HomeMy WebLinkAbout2018-093-10/02/2018-DIRECTING THE CITY MANAGER TO SUBMIT TO THE U.S. ARMY CORPS OF ENGINEERS THE CITY'S COMMENTS ON THE RESOLUTION 2018-093
OF THE COUNCIL OF THE CITY OF FORT COLLINS
DIRECTING THE CITY MANAGER TO SUBMIT TO THE U.S. ARMY CORPS OF
ENGINEERS THE CITY'S COMMENTS ON THE FINAL ENVIRONMENTAL IMPACT
STATEMENT FOR THE NORTHERN INTEGRATED SUPPLY PROJECT
WHEREAS, the Northern Colorado Water Conservancy District ("Northern Water") is
pursuing the Northern Integrated Supply Project ("NISP"), a water storage and supply project that
would divert significant amounts of water from the Cache la Poudre River upstream of Fort
Collins; and
WHEREAS, to move forward with the necessary federal permitting for NISP, Northern
Water is required by the National Environmental Policy Act to complete an environmental impact
review process, conducted in this case by the U.S. Army Corps of Engineers ("Corps") as the
permitting agency under the federal Clean Water Act; and
WHEREAS,as part of the federal environmental impact review process,on April 30,2008,
the Corps issued a draft Environmental Impact Statement ("DEIS"); and
WHEREAS, pursuant to Resolution 2008-082, the City timely submitted comments to the
DEIS on September 10, 2008, which resolution states, among other things; that "the City Council
opposes NISP as it is described and proposed in the DEIS and also opposes any variant of NISP
that does not address the City's fundamental concerns about the quality of its water supply and the
effects on the Cache la Poudre River through the City, which are critical to the City's quality of
life, health, and economic development and environment"; and
WHEREAS; as part of the federal environmental impact review process, on June 19, 2015,
the Corps issued a supplemental draft Environmental Impact Statement ("SDEIS"), which
included a conceptual mitigation plan to mitigate NISP's impacts; and
WHEREAS, pursuant to Resolution 2015-082, the City timely submitted comments to the
SDEIS on September 2-, 2015, which resolution states, among other things, that "the City Council
cannot support NISP as it is currently described and proposed in the SDEIS,with the understanding
that City Council may reach a different conclusion with respect to a future variant of NISP, such
as the proposed Modified Alternative Number 4 as described in the City's comments, if such
variant addresses the City's fundamental concerns expressed in the City's comments to the DEIS
and comments to the SDEIS"; and
WHEREAS,pursuant to Resolution 2017-073,the City submitted comments and provided
testimony in a State process under Section 37-60-122.2 of the Colorado Revised Statutes,by which
Northern Water sought and subsequently received State approval of a plan to mitigate NISP's
impacts on fish and wildlife resources ("State Fish and Wildlife Mitigation and Enhancement
Plan");and
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WHEREAS, pursuant to Resolution 2017-024, City Council authorized and directed the
City Manager or his designees "to meet on a regular basis with the Northern Water regarding NISP
and to discuss and explore the City's concerns and interests in order to ascertain whether those
interests can be met, including through potential solutions to address the City's goals and issues
related to NISP";and
WHEREAS, pursuant to Resolution 2018-053, City Council authorized and directed the
City Manager or his designees "to meet with Northern Water to seek to negotiate regarding NISP,
and if Northern Water is so willing, to engage in negotiations regarding NISP" pursuant to the
direction given in said resolution; and
WHEREAS, as part of the federal environmental impact review process, on July 20, 2018,.
the Corps issued a final Environmental Impact Statement ("FEIS"), which included a conceptual
mitigation plan to mitigate NISP's impacts, and pursuant to, a subsequent extension of time,
provided for submission of public comment up to October 4, 2018; and
WHEREAS, various modifications to the preferred alternative for NISP are included in the
FEIS, some of which affect the amount of water that would flow through portions of Fort Collins,
which raises various issues for the City; and
WHEREAS, pursuant to the direction of City Council, City staff, working with the
assistance of outside technical experts, undertook a thorough and detailed technical analysis of the
FEIS primarily as it pertains to the NISP proposed action and its direct impacts in Fort Collins and
to the City; and
WHEREAS, at the September 11, 2018 City Council work session, City staff presented
background on NISP as well as staff's proposed analytical and data-driven objective approach to
commenting on the FEIS pursuant to previous direction from City Council; which approach City
Council endorsed; and
WHEREAS, to the extent practicable under the short period of review of the FEIS, City
staff received input from various City boards and the public regarding NISP; and
WHEREAS, the City wishes to express its support for other communities, including
participants in NISP, in their quest to acquire reliable water supplies without significantly
adversely affecting other communities and the environment; and
WHEREAS,the City has concluded that the FEIS is deficient in various respects,including
proposed actions to mitigate NISP's impacts, as set forth in the City's comments to the FEIS,
which are attached hereto as Exhibit "A";
WHEREAS, City staff has concluded that NISP will be harmful to Fort Collins and to the
City based on a thorough review of the impacts described by the FEIS as well as the impacts that
staff expects from the project; and
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WHEREAS, in view of the significance of the impacts that NISP would have on the City
and the Fort Collins community,it is in the City's best interest to comment on the FEIS,to continue
to participate in these proceedings, and to monitor the responses to the comments of the City and
others.
NOW THEREFORE, BE IT RESOLVED BY THE COUNCIL OF THE CITY OF FORT
COLLINS as follows:
Section 1. That the City Council cannot support NISP as it is currently described and
proposed in the FEIS, with the understanding that the City Council may reach a different
conclusion with respect to a future variant of NISP and its mitigation plan, if such variant and
associated mitigation address the City's fundamental concerns, including but not limited to those
expressed in the City's comments to the DEIS, SDEIS, State Fish and Wildlife Mitigation and
Enhancement Plan, and FEIS through improved mitigation or other means.
Section 2. That the City Manager is hereby authorized and directed to submit to the
Corps formal comments to the FEIS that are substantially similar with those attached hereto as
Exhibit "A" and incorporated herein by reference, in accordance with the deadline for such
submission.
Passed and adopted on at a regular meeting of the Council of the City of Fort Collins this
2nd day of October, A.D. 2018.
Mayor
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EXHIBIT A
City of
Flort Collmins
Comments on the Final Environmental Impact Statement
for the
Northern Integrated Supply Project
Dated: October 4, 2018
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 2 of 51
Table of Contents
INTRODUCTION AND EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
SECTION 1 : INCORPORATION OF FORT COLLINS ' PREVIOUS COMMENTS . . . . . . . . 6
TODEIS AND SDEIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SECTION 2 : WATER QUALITY-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 . 1 Glade Reservoir (and Forebay) Water Quality Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SECTION 3 : GEOMORPHOLOGY-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 . 1 . 1 Inconsistencies and Inadequacies in Geomorphic Analysis in the FEIS Stream
Morphology and Sediment Transport Technical Report Must Be Addressed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3 . 1 .2 Inadequacies in Geomorphic Analysis Must Be Addressed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3 . 1 . 3 Additional Analysis Suggest that the FEIS Substantial Underestimates Alternative 2M ' s
Impacts 23
3 .2 Additional Specific Geomorphological Comments on the FEIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3 .2 .2 Reduction of Scouring Flows have Been Ignored as an Important Factor in Maintaining
ChannelCapacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3 .2 . 3 Reduction of Scouring Flows Has Been Ignored as an Important Factor in Maintaining
ChannelCapacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3 . 2 .4 Bio-Geomorphic Feedback Loop Has Been Dismissed Upstream of I-25 . . . . . . . . . . . . . . . . . . . . . 30
SECTION 4 : RIPARIAN-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2 Unmitigated Wetland Impacts Must Be Mitigated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
SECTION 5 : RECREATION-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5 . 1 Impacts to Boating and Tubing Are Underestimated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
SECTION 6 : SOCIOECONOMIC-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6 . 1 The FEIS Fails to Include Any Analysis of Property Value Diminution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 3 of 51
SECTION 7 : AIR QUALITY-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
7 . 1 Northern Should be Required to Mitigate Air Quality Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
SECTION 8 : WILDLIFE-RELATED COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8 . 1 Impacts to Wildlife from a Slow Change in Riparian Habitats Must Be Mitigated . . . . . . . . . . . . 45
8 .2 Impacts to Fish Should Be Mitigated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
SECTION 9 : ADAPTIVE MANAGEMENT COMMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
9 . 1 The Adaptive Management Plan Should Be Revised to Meet the Goals of Mitigation and
Enhancement ' , , ' . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 4 of 51
INTRODUCTION AND EXECUTIVE SUMMARY
The City of Fort Collins ("Fort Collins") respectfully submits to the United States Army Corps
of Engineers ("Corps") these comments on Final Environmental Impact Statement, dated July
2018 and issued on July 20, 2018 ("FEIS"), and its associated technical reports and related
documents, regarding the Northern Integrated Supply Project ("NISP" or "Project") proposed by
the applicant, the Northern Colorado Water Conservancy District ("Northern" or "District") .
Reference materials are identified in the comments . These reference materials constitute part of
these comments . Fort Collins reserves all rights to supplement these comments on the FEIS
and/or NISP, as may be appropriate.
To the extent permitted by the short comment period, Fort Collins has completed a thorough,
scientific review of the FEIS under the Clean Water Act, 33 U. S . C . § 1251 et seq. ("CWA") , the
National Environmental Policy Act, 42 U. S . C . § 4321 et seq. ("NEPA"), and other relevant
authority. Fort Collins completed this review through expert Fort Collins staff and consultants
listed in Appendix A.
Fort Collins was founded and is located along the Cache la Poudre River ("Poudre River") . The
Poudre River is a significant amenity and resource for Fort Collins in numerous respects and is
cherished as a defining element of the city and community. As described below, Fort Collins has
invested significant resources into the Poudre River, including through the use of two wastewater
treatment plants, by purchasing land along the river' s banks, improved flood conveyance to
protect and enhance public safety, and using it for recreation and economic enhancement. It is
difficult to overstate the meaning and significance of the Poudre River to Fort Collins and its
community.
Fort Collins is located downstream of the Project ' s primary points of diversion on the Poudre
River, and thus stands to bear the brunt of NISP ' s impacts. While Fort Collins understands and
appreciates the needs of other communities to develop their water supplies in environmentally-
responsible ways, Fort Collins must take reasonable actions to protect its assets and investments .
Fort Collins has thus sought through these comments a pragmatic approach of focusing on
Alternative 2M, direct impacts to Fort Collins, and ways to improve mitigation of the Project ' s
impacts . See 40 C .F .R. § 230. 93 (a)( 1 ) (regarding compensation for all "aquatic resource
functions that will be lost as a result of the permitted activity. ") . Fort Collins ' comments are
organized by general topic area. The following is a brief summary.
SECTION I * Incorporation of Fort Collins ' Previous Comments to DEIS and SDEIS.
Fort Collins incorporates by reference its comments on the original draft and supplemental draft
environmental impact statements for NISP .
SECTION 2 : Water Quality-Related Comments. Fort Collins concerns regarding water
quality focus on three primary areas of impacts to Fort Collins : degradation of river water
quality; impacts to Fort Collins ' wastewater operations ; and impaired waters (303 (d)) listing. As
set forth in detail below, Fort Collins proposes additional mitigation measures that are needed
address these impacts. With respect to certain impacts to Fort Collins ' wastewater operations,
additional information is needed in order to Fort Collins to understand such impacts .
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 5 of 51
SECTION 3 : Geomorphology-Related Comments. There are certain deficiencies in the FEIS
regarding impacts of NISP operations on river geomorphology, particularly the impacts of NISP
on increased flood risk and Poudre River health and function through Fort Collins . Among other
recommendations, Fort Collins recommends flow-based mitigation in the form of a three-day
peak flow bypass in all years and a minimization of abrupt changes in the "descending limb" of
the hydrograph. Additional necessary mitigation is set forth in detail below.
SECTION 4 : Riparian-Related Comments. Fort Collins continues to be concerned over
potential underestimation of impacts to riparian and wetland habitats . The focus of these
comments is on the sufficiency of mitigation for impacts . Among other recommendations, any
approval of NISP must include mitigation for Poudre River wetland functional losses and losses
of stream function. Additional necessary mitigation is set forth in detail below.
SECTION 5 : Recreation-Related Comments. Over decades, the City has spent tens of
millions of dollars acquiring and improving land along the Poudre River, building recreation
amenities on those lands , and restoration natural habitat. The FEIS does not appear to have
properly addressed the impacts from NISP to recreation.
SECTION 6 : Socioeconomic-Related Comments. The FEIS property value analysis focuses
exclusively on flood risks; no analysis has been provided regarding the diminution of property
values near the Poudre River and within Fort Collins ' municipal limits should reduced river
flows adversely impact the riparian forest.
SECTION 7 : Air-Quality-Related Comments. As stated in the FEIS , there will be
demonstrable impacts to NOx and VOC, which contribute to the formation of ozone. NISP
should employ dust control strategies during construction that are consistent with Fort Collins '
dust control ordinance. Additional necessary mitigation is set forth in detail below.
SECTION 8 : Wildlife-Related Comments. The FEIS fails to recognize that the loss of
wetland and riparian habitat is a real and cumulative change that must be mitigated regardless of
the time needed for this change to occur or the rate of change. Northern Water should be
required to monitor and quantify reductions in habitat and develop actions to restore or replace as
impacts are identified, and to adequately address such issue through adaptive management.
Additional necessary mitigation is set forth in detail below.
SECTION 9 : Adaptive Management Comments. Fort Collins agrees with the description
provided of adaptive management in the Conceptual Mitigation Plan. However, Fort Collins is
concerned that certain omissions will lead to an ineffective adaptive management program and
presents the following recommendations to remedy this concern. Specific recommendations to
improve the adaptive management program are set forth below.
[Remainder of Page Left Blank Intentionally]
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 6 of 51
SECTION 1 : INCORPORATION OF FORT COLLINS ' PREVIOUS COMMENTS
TO DEIS AND SDEIS
Fort Collins hereby incorporates by reference its comments on the original DEIS for NISP ,
including comments on the regulatory framework, which Fort Collins provided on September 10,
2008 , and its comments on the SDEIS for NISP, including comments on the regulatory
framework, which Fort Collins provided on September 2, 2015 . The original DEIS and SDEIS
contained flaws that rendered it insufficient under NEPA and the rules and regulations and
guidelines thereunder, the Clean Water Act, and the rules and regulations and guidelines
thereunder, and other relevant legal requirements. The Corps has addressed some of the
comments made by Fort Collins and other stakeholders . However, the FEIS remains inadequate
for the Corps to adequately discharge its obligations under these requirements and, as discussed
herein, underestimates various impacts .
[ Remainder of Page Left Blank Intentionally]
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 7 of 51
SECTION 2 : WATER QUALITY-RELATED COMMENTS
2. 1 GLADE RESERVOIR (AND FOREBAY) WATER QUALITY COMMENTS
2. 1 . 1 The Initial Fill of Glade Reservoir Must Be Addressed
FEIS Section 4.3 .2.2. 1
"Glade Reservoir would likely experience a trophic upsurge and trophic depression in
the initial decade following the first filling of the reservoir (Hydros 2018j). Water quality
in the reservoir during this period is uncertain and would likely differ from the long-term
results simulated with Glade Reservoir water quality model. Since there is no reliable,
well-tested method for predicting the magnitude and duration of the tropic upsurge
period, and because no data during the trophic upsurge is available for a similar
reservoir, the analysis for Glade Reservoir is limited to a qualitative discussion with a
high degree of uncertainty.
"Assuming nutrient concentrations are approximately twice as high in the period
following initial fill than those simulated in the water quality model suggests that the TN
and TP concentrations could range from 500 to 800 ug/L and 24 to 30 ug/L. TN and TP
concentration in Glade Reservoir could therefore potentially exceed the applicable in-
reservoir interim numeric values of 426 ug/L and 25 ug/L during the reservoir transition
period. Additionally, internal loading of NH3 and ortho-P could likely be relatively high
as well, due to decomposition of organic material in the existing soil and vegetation at
the Glade Reservoir site. Elevated nutrient concentrations . . . could increase the impact of
Glade Reservoir releases on water quality in the Poudre River.
"Depending on the timing and relative magnitude of releases from Glade Reservoir, the
elevated nutrient concentration could increase nutrient concentrations in the Poudre
River and potentially increase algae and periphyton growth downstream of the release
point to the river. "
Comment: The Glade Reservoir water quality model predicts water quality during the post-
filling phase of reservoir operations . Due to data and modeling constraints acknowledged in the
FEIS , a simulation of water quality during the filling period was not conducted, nor is feasible.
As a result, there is a great deal of uncertainty around water quality of releases during the first
decade of operations . At this time, it is unclear if the water quality certification under Section
401 of the Clean Water Act ("401 Certification") will consider the two distinct operational
phases for the Project, and as such, it is unclear how the risks to downstream Poudre River water
quality will be managed.
Furthermore, it is unknown to what extent the expected increases in nutrient levels will impact
water quality in Segment 11 , within which Fort Collins has two permitted wastewater discharge
points for Fort Collins ' Mulberry and Drake Facilities . The effluent discharge limits that are
calculated as part of the respective permits are based on a 5 -year records of historical water
quality of the receiving water, in this case, Segment I I of the Poudre River. As such, future
discharge permits for the Mulberry and Drake Facilities will convey the financial and operational
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 8 of 51
burden of water quality impacts caused by NISP during the filling phase onto Fort Collins '
wastewater operations through stricter permit conditions, which translate to additional
operational and technological control measures.
Recommendation : If the 401 Certification process does not include specific conditions for the
filling phase of Glade Reservoir, Northern should be required to expressly include in its
proposed adaptive management plan, specific water quality targets for the filling phase that
minimize impacts to downstream water quality to the same extent that the 401 Certification
requires for the post-fill, full reservoir operations .
2 . 1 . 2 Degraded Forebay Water Quality Is a Concern and Must Be Monitored
Glade Reservoir Water-Quality Model Report Section 5.7.8
"As previously described, water diverted to Glade Reservoir would flow into a forebay
before being pumped into the reservoir. The forebay would store approximately 2, 500
AF (including �500 AF of dead pool) with a surface area of approximately 100 acres (0. 4
km2). Given the size of the forebay, there is potential for changes in water quality,
particularly temperature, during temporary storage in the forebay . . . The impact of
temporary storage in the forebay on temperature and water quality depends on several
factors, including meteorology, inflowing temperature and water quality, and flow rates.
The changes in water quality and temperature are typically greatest at low inflow rates,
due to the longer residence time in the forebay under these conditions (I week or more).
Changes also tend to be large when diversions begin, since diverted Poudre River water
mixes with water that has been stored in the forebay. When inflow rates are high, the
forebay has less of an impact on water quality, since the residence time in the forebay is
relatively short under these conditions, on the order of 23 days. Generally speaking,
temporary storage in the forebay results in increases in water temperatures of�1, 7 °C (3
Y) on average, though this can vary from -3. 5 °C to + 7. 5 °C (- 6. 3 OF to 13. 5OF). DO
decreases by �0. 5 mg/L on average and changes range from - 1 . 5 mg/L to + 1 . 5 mg/L.
Nutrient concentrations (ortho-P, NH3, NO3) typically decrease due to algae growth in
the forebay, particularly when flow through the forebay is low. TOC concentrations also
decrease slightly as organic matter is mineralized in the forebay. "
Comment: The forebay is small, shallow (�8 m) and will not allow for significant dilution of
nutrients (such as phosphorus and nitrogen, which typically are the factors limiting maximum
growth potential of algae in a standing water body) . When concentrations are high, the forebay
the forebay could become eutrophic, promoting the growth of suspended algae. This would most
likely occur when low flow or no flow is entering the forebay and thus minimal dilution.
Such conditions would likely be temporary, but algal growth response to nitrogen and
phosphorus can be very rapid (e. g. populations can double in less than a day), which can produce
an algal bloom in a matter of days . If the forebay is stagnant, which it likely will be at times
under conditions that are outlined for its management as part of Alternative 2M, algal blooms are
likely.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 9 of 51
Furthermore, forebay algal blooms involving undesirable algal species, such as some species of
blue-green algae (cyanobacteria), could also have an undesirable effect on the species
composition of phytoplankton within Glade Reservoir. The forebay could, in fact, serve as a
source of undesirable algal species in the reservoir, adversely affecting the species composition
of reservoir phytoplankton. It is recognized that a nuisance bloom of algae in the forebay would
not directly cause downstream impairment on the Poudre River because the water will enter
Glade Reservoir prior before being discharged to the Poudre River. However, because the inlet
to Glade Reservoir is near the outlet, there is the risk that degraded water from the forebay will
not be well-mixed in Glade Reservoir before entering the Poudre River. As such, reservoir
releases have the potential to degrade downstream waters .
Recommendation : To avoid having degraded water from the forebay being flushed into the
Poudre River and affecting the water quality of the Poudre River, Fort Collins recommends that
chlorophyll a be monitored as part of Northern Water' s long-term water quality monitoring
program, as generally described in the 2017 Fish & Wildlife Mitigation & Enhancement Plan.
Triggers for management action should be identified in adaptive management plans and should
support meeting the interim chlorophyll a cold water Lakes and Reservoir Standard for Direct
Use Water Supply Reservoirs of 5 ug/L (5 CCR 1002-31 ), slated for adoption in 2022 .
2.2.3 Releases of Glade Reservoir Water Must Be Monitored to Address Hypoxia
Glade Reservoir Water-Quality Model Report Section 7.2. 1 .2
"The simulations suggest that summer algae growth may cause local DO maxima in the
metalimnion (see profile on 712111998), but the decomposition of these algae may also
cause a metalimnetic minimum to form later in the year (see profile on 911511998).
Toward the end of the stratified season, hypoxic (< 2. 0 mg/L) DO conditions can develop
at the bottom of the reservoir. In years with higher storage volumes in Glade Reservoir,
such as in 1998, the hypoxic conditions are generally limited to the bottom 10 20 feet of
the reservoir, representing a small fraction of the overall hypolimnion volume, while DO
concentrations in the rest of the hypolimnion remain higher (typically around 4 6
mg/L). In years with lower storage, such as 1993, the hypolimnion of Glade Reservoir is
much smaller and low DO concentrations are more likely to impact a large fraction of
the hypolimnion prior to fall turnover (Figure 44). Once the reservoir turns over in the
fall, DO concentrations near the bottom are replenished and are relatively uniform
throughout the water column. "
NISP Fish and Wildlife Mitigation and Enhancement Plan 5.2. 1 .5
"Currently, it is expected that both the low flow pipeline release and the high flow canal
release would incorporate a chute feature at their outfalls into the Poudre River that
contain either baffles or steps to increase dissolved oxygen and dissipate energy to
prevent channel erosion, or contain in channel rock structures that would serve the same
YY
purposes.
Comment: Modeling reported in the FEIS and supporting documents shows that hypoxia is
expected in the hypolimnion of Glade Reservoir. However, the documents assert that the
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 10 of 51
impacts from the degraded quality of water released to the Poudre River from Glade Reservoir
will be insignificant.
The hypolimnetic releases from Glade Reservoir to the Poudre River during periods of hypoxia
(oxygen depletion) could contain dissolved manganese, iron, and other metals and metalloids
that are commonly released in dissolved form from hypoxic sediments of lakes. If released
directly to the Poudre River, the dissolved metals could cause downstream reaches to exceed
water quality standards .
The 2017 Fish and Wildlife Mitigation and Enhancement Plan specifies that Northern will
construct a passive aeration pathway for water being delivered out of Glade Reservoir so that the
released water will be oxygenated when it merges with the Poudre River. This design feature of
the outlet will likely be successful in oxygenating hypoxic waters that are leaving Glade
Reservoir, which will promote oxidation of dissolved substances such as manganese, iron, or
other metals or metalloids near the point of discharge. Oxidation of metals does not always
occur quickly, however, and may not be complete in transit to the river even following
successful oxygenation of outflow water. Also, oxidation of metals is not a full solution to the
potential problem of excessive concentrations of metals that pass from the lake sediments to the
hypolimnion because of hypoxia.
Precipitated (solid) forms of metals, in addition to dissolved forms, are subject to numeric
standards promulgated by the State of Colorado (through the Colorado Water Quality Control
Commission) that limit concentrations of total metals (dissolved plus particulate) . Therefore,
even complete elimination of metals in dissolved form would not resolve the potential water
quality problem of excessive concentrations for total metals in water reaching the Poudre River.
In addition to metals, phosphorus in dissolved form is often released from hypoxic sediments and
could cause exceedance of future stream standards for total phosphorus . Although not currently
regulated, the Colorado Water Quality Control Commission has issued interim numerical values
for total phosphorus and nitrogen, which are slated for adoption in 2027 (5 CCR 1002-31 ,
Section 31 . 17) . Release of fixed nitrogen (i . e. , excluding N2, which is inert) is less likely, but
ammonia is frequently present in hypoxic water. Ammonia, which is strictly regulated under
Regulation 31 (5 CCR 1002-31 ), would not be fully oxidized during aeration at the discharge
site.
Recommendation : To avoid degradation of Poudre River water quality by Glade Reservoir
releases, it is recommended that total and dissolved metals, ammonia, total nitrogen, and
phosphorus be monitored at the reservoir outlet as part of Northern Water' s long-term water
quality monitoring program, as generally described in the 2017 Fish and Wildlife Mitigation and
Enhancement Plan. Triggers for management action should be identified in adaptive
management plans and should support meeting existing standards as well as the Interim Values
for cold water Lakes and Reservoirs for Total Nitrogen and Total Phosphorus (5 CCR 1002-31 ) .
Northern must prepare a contingency plan that includes design features and costs for
hypolimnetic aeration of Glade Reservoir by a process that prevents disruption of water column
stratification as a means of offsetting adverse effects of deep water release from the reservoir, if
such effects are documented through water quality monitoring.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 11 of 51
2.2 POUDRE RIVER WATER QUALITY COMMENTS
2.2.1 Uncertainties Inherent in the Modeling Process Must be Addressed by
Northern
Cache la Poudre River Water-Quality Analysis Effects Report Section 1 .3
"In February 2009, the Corps decided that a common technical platform (CTP) would be
developed for several key resources potentially affected by NISP, the proposed Halligan
Water Supply Project and the Seaman Water Supply Project. The CTP was developed
such that environmental effects to multiple resources—surface water, groundwater, water
quality, geomorphology, aquatic habitat, riparian habitat, etc. occurring as a result of
NISP, Halligan, and Seaman projects could be compared against consistently-defined
current conditions hydrology and future conditions hydrology. With three proposed
projects located primarily in a single river basin and potentially impacting some of the
same reaches of that river, it is important that each EIS represent the river basin using a
CTP that is based on consistent data and assumptions regarding key operational aspects.
To meet this objective, a series of integrated hydrologic models known as the CTP model
sequence was developed to simulate current conditions hydrology, future conditions
hydrology, project alternatives scenarios, and cumulative effects of the proposed project
alternatives. "
Comment: There is a level of uncertainty inherent to water quality modeling that is reflected in
the described Poudre River water quality impacts from Alternative 2M. This level of uncertainty
is magnified by the fact that information about other future proposed reservoirs expansions was
not available at the time of modeling.
Recommendation : Northern should be accountable for mitigation of water quality problems
caused by Glade Reservoir, including unexpected exceedance of stream standards not predicted
by current modeling. 40 C .F .R. § 230, 10(d) (no CWA Section 404 permit shall be issued "unless
appropriate and practicable steps have been taken which will minimize potential adverse
impacts"). Moreover, Northern should work with other stakeholders to strengthen and integrate
existing water quality monitoring programs on the Poudre River and use proposed adaptive
management framework to mitigate the effects of changes in water quality resulting from NISP
operations . The CWA and NEAP require the FEIS and Record of Decision include adequate
mitigation measures . See Robertson v. Methow Valley Citizens Council, 490 U. S . 332, 352
( 1989) (stating that mitigation measures should be "reasonably complete" and be discussed in
"sufficient detail") ; Bering Strait Citizens for Responsible Res. Dev. v. United States, 524 F . 3d
938, 955 (9th Cir. 2008) (explaining that mitigation measures should be developed to a
"reasonable degree"). Courts have rejected adaptive management plans where agencies have
failed to use definite criteria or standards . See, e.g. , Natural Res. Def. Council v. Kempthorne,
506 F. Supp. 2d 322, 387 (E.D . Cal. 2007) ("Adaptive management is within the agency's
discretion to choose and employ, however, the absence of any definite, certain, or enforceable
criteria or standards make its use arbitrary and capricious under the totality of the
circumstances . ") ; Nat 'l Wildlife Fed'n v. U. S. Army Corps of Eng 'rs, 92 F . Supp. 2d 1072 , 1078
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 12 of 51
(D . Or. 2001 ) (explaining that the Corps ' adaptive management approach provided the court with
insufficient information to rule on summary judgment) .
2 .2 . 2 Northern Must Be Responsible for 303(d) Listing Issues
Cache la Poudre Water-Quality Analysis Effects Report Section 3.3
"As a basis for the qualitative analysis, five questions were addressed for each
constituent. The purpose of these questions was to develop multiple lines of evidence
regarding potential changes in constituent concentrations . . . Proxy constituents, in this
context, are constituents quantitatively evaluated in the model that demonstrate similarity
in sources and behavior to a constituent evaluated qualitatively. In this case,
quantitative estimates of concentration changes for a proxy constituent can be used to
help inform the qualitative evaluation of a related constituent. The evaluation and
interpretation of these individual lines of evidence provide an estimate of potential
direction and magnitude of changes in water quality. Recognizing the inherent
uncertainty of this process, the results are descriptive in nature and provide less detail
than quantitative estimates. "
Comment: There is a lack of regulatory context for water quality impairment predicted by the
modeling underlying the FEIS . Specifically, some degradations of river water quality by
Alternative 2M are identified by modeling, as given in the FEIS and supporting documentation,
but are not framed in terms of 303 (d) listings . See 33 U. S . C . 1313 (d) .
It is important that the Corps impose binding permit conditions on Northern to guarantee
Northern' s duty to assist Fort Collins or other affected parties in correcting and mitigating water
quality problems resulting from the Project that either cause a new 303 (d) listing that did not
exist prior to implementation of the Project or exacerbate an existing 303 (d) listing. The
following are examples from the FEIS where 303 (d) listing may occur or existing listing may be
exacerbated as a result of Alternative 2M :
• Segment 12 of the Poudre River is currently on the Colorado Department of Public
Health and Environment ' s ("CDPHE") Monitoring and Evaluation List due to elevated
pH and Segment 12 regularly exceeds the State ' s interim nutrient criteria. Changes in
peak flows during May-July in Segment 12 of the Poudre River are predicted to
significantly increase temperature, nutrient concentrations, sediment aggradation and
periphyton standing crop near the Fossil Creek confluence. Combined, these changes
may negatively impact the aquatic life community within this reach and increase the
likelihood of 303 (d) listings for nutrients, pH and dissolved oxygen (with increased
photosynthesis and metabolism) .
• Concentrations of selenium and iron in Segment 12 near the Fossil Creek confluence are
also predicted to increase during May-July. Concentrations of these constituents are
already elevated as compared to aquatic life standards .
• Segment 12 of the Poudre River is currently on the 303 (d) list because the recreational
use is impaired due to elevated E. coli concentrations. During May-July, this segment is
predicted to see large increases in E . coli concentrations ; the higher end of the range of
predicted increase would be above the CDPHE ' s standard. The timing of the loss of
dilution flows will make it even more difficult to meet the standard. A total maximum
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 13 of 51
daily load ("TMDL") for this segment is currently being developed by CDPHE; it is very
important that the State of Colorado recognize the timing and magnitude of flow
reductions when developing TMDL models and assigning load and waste load
allocations .
• Water temperature near the transition between Poudre River Segments 11 and 12 (near
the Boxelder Creek confluence with the Poudre River) is predicted to increase
considerably under current and future conditions using Alternative 2M. It can be
assumed that these temperature changes would also occur on the Poudre River at the
outfall of the Drake Water Reclamation Facility ("Drake Facility") and the Poudre River
below the Fossil Creek confluence. These changes would increase the risk of exceeding
CDPHE ' s aquatic life warm water temperature criteria in both segments and could affect
Fort Collins ' ability to discharge to the Poudre River.
Recommendation : Northern should commit to being involved as a stakeholder during any
303 (d) listing process and/or TMDL development, and commit to adjusting Glade Reservoir
operations where possible to help reduce constituent concentrations of interest. In addition,
Northern Water should commit to work with other stakeholders to strengthen and integrate
existing water quality monitoring programs on the Poudre River and use an adequate proposed
adaptive management framework to mitigate the effects of changes in quality and reduced flows
on aquatic life.
2.3 FORT COLLINS WASTEWATER OPERATIONS COMMENTS
2.3. 1 Northern Must Not Reduce Dilution Flows at the Mulberry Water
Reclamation Facility Discharge Location
Cache la Poudre River Water-Quality Analysis Effects Report Section 1 .2.2
"Alternative 2M is a modified version of NISP Alternative 2 and is the Applicant 's
preferred alternative. As with Alternative 2, Alternative 2M would include construction
of Glade Reservoir and Upper Galeton (Figure 3). Also, like Alternative 2, these new
reservoirs would be filled by diversion to the Poudre Valley Canal and the SPWCP,
respectively. There is, however, one key difference between Alternative 2 and
Alternative 2M. Alternative 2M is designed to increase the amount of water in the river
between the Poudre Valley Canal and the Mulberry Water Reclamation Facility
(Mulberry WRF) outfall. This is achieved by delivering a fraction of the water to
Participants via a new diversion. This new diversion would be located immediately
above the Mulberry WRF outfall (RM 43, Figure 3) to maintain higher water quality for
delivery to project Participants. Water is either left in the river through lower diversions
at the Poudre Valley Canal (compared to Alternative 2) or added back to the river by
release from Glade Reservoir for subsequent diversion at the new NISP diversion
location downstream (0. 1 miles upstream of the Mulberry WRF outfall). As a result,
flow rates during low flow periods tend to be higher from the Poudre Valley Canal to the
Mulberry WRF outfall for Alternative 2M as compared to Alternative 2. "
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 14 of 51
FEIS Section 4.3 .2.6. 1
"The Mulberry WRF discharges to the Poudre River downstream of the Lincoln Street
Gage (Figure 4-20). Chronic annual low flow values decrease from 1 . 6 cfs under
Current Conditions hydrology to 1 . 4 cfs and acute annual low values remain unchanged
at 0. 2 cfs. Beneficial effects can occur at times due to requirements associated with the
exchange of diversions from the Larimer- Weld Canal to the Poudre Valley Canal.
Chronic WQBEL values are slightly lower for all modeled water quality constituents in
Alternative 2M except E. coli. Changes are typically less than 3 % compared to Current
Conditions hydrology. Acute WQBEL values are unchanged. Chronic ammonia WQBEL
values are generally less than 2 % lower than Current Condition Effects in the majority of
months. Acute ammonia WQBELs show increases and decreases of less than 2 % or no
change depending on the month. Chronic WA temperature WQBELs from April to
September for Alternative 2M are less than 0. 8 °C higher than Current Conditions
hydrology, while acute DM values range from zero to 1. 1 °C higher than Current
Conditions hydrology. "
See also FEIS Sections 4.2 . 5 .4, 5 . 3 .4 .2 . 5 -6, 5 . 3 .4 .4, 5 . 6 .2 . 1 .2, 5 . 3 .4.2 . 1 -5 . 3 . 4 . 2 . 7 ,
4. 3 .2 . 5 . 1 ,4 . 3 .2 . 6 . 1 , 4 . 3 .2 . 6 .25 5 . 3 .4 . 5 .2 regarding specific constituents .
Comment: Without a specific mitigation requirement for Alternative 2M, effluent limits
established at 5 -year intervals by Colorado Water Quality Control Commission permitting of
treated wastewater discharge by the Mulberry Water Reclamation Facility ("Mulberry Facility")
likely will become more stringent as a result of reduced dilution flow in the Poudre River near
the Mulberry Facility' s outfall.
The discharge permit limits for Fort Collins ' Mulberry Facility are calculated based on the
available dilution flows in the Poudre River at the permitted outfall. These dilutions flows allow
for less stringent effluent limits than would be required without these flows . Under the Mulberry
Facility' s current five-year permit, the annual regulatory dilution (regulatory low flow) for
Mulberry Facility is 1 . 6 cfs for chronic (30-day) low flow and is 0 .2 cfs for the acute low flow.
Because of the relatively small size of the permitted effluent discharge (6 mgd, 9 . 3 cfs), the small
dilution flows are significant to Fort Collins in meeting effluent limits .
Flow that in the past has reached the Mulberry Facility derives from diffuse upstream sources,
including ground water accretions and some small overland flow in wet weather. Most critical is
ground water accretions, which persists even in dry weather. Under Alternative 2M, a new NISP
diversion of flow from the Poudre River will occur 0 . 1 mile above the Mulberry Facility outfall .
Therefore, the diversion structure will receive the diffuse flow that was received in the past by
the Mulberry Facility.
In theory, strict water administration could allow the Mulberry Facility to continue to receive the
dilution flow as in the past, and Northern could, at the same time, take the full amount of water
from the Poudre River corresponding to its deliveries upstream (less transit and other losses) . In
reality, however, several complications that make this outcome very unlikely to succeed in
providing dilution flows for the Mulberry Facility.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 15 of 51
Water flows to be managed at the new Poudre River diversion by Northern will be large
compared with the small amount of water that would match the flows that are now reaching the
Mulberry Facility. Therefore, as a practical matter, ensuring that Northern only takes the water
equal to its deliveries from Glade Reservoir (less transit and other losses) will need to occur on a
day-to-day basis, and would require the installation and operation of appropriate monitoring
equipment for water flow in small amounts at and below the diversion.
Northern could thus inadvertently deprive the Mulberry Facility of a portion of these flows
because of estimation errors in accounting for water losses in the Poudre River that occur
between the upstream point of delivery of Glade Reservoir water into the Poudre River and the
downstream point of re-diversion of such water. Although standard allowances likely will be
made for these losses (e. g. , 0 .25 % per mile), the allowances are estimates, and the needed flow
for the Mulberry Facility likely falls within the margin of error for the estimated losses. Thus,
the estimates will likely lead to reductions of the historical flow for the Mulberry Facility in
some instances.
The Water Quality Control Division, which issues discharge permits at five-year intervals, uses
an algorithm (known as "DFLOW") for quantifying the dilution flow credit for a wastewater
discharge. The basis for the DFLOW calculations is a daily record of discharge. DFLOW
calculates low flows for acute ( 1 -day) and chronic (30-day) conditions ; the lowest daily and
monthly DFLOW values are used as annual regulatory flows . Weekly DFLOWS also are
calculated. Specific water quality constituents differ in application of DFLOW values . For
example, for chronic conditions, metals follow annual DFLOWs, temperature follows weekly
DFLOWs, and ammonia follows monthly DFLOWs. In other words, all time intervals are
significant in application of DFLOW to determination of effluent limits .
The DFLOW algorithm chooses low flows based on the daily record. The algorithm is complex;
it does not identify the single lowest flow as the regulatory limit, but DFLOW values typically
are close to the lowest flow. Because the computation is based on daily data, a few days per year
of zero flow would reduce the acute low flow to zero, and would reduce the chronic low flow,
which is calculated from running 30-day averages. Furthermore, because the calculations are
made from a 10-year record of flow, even one year during which small flows were improperly
managed could result in a very adverse DFLOW values for chronic and acute conditions used in
permitting. Therefore, the flow management related to regulatory flows, which has not been
necessary in the past because of the natural flow conditions, is quantitatively more demanding
than typical water management for the amounts of water that are of interest to Northern.
Some specific consequences for the Mulberry Facility that would result from depletion or loss of
low flows as calculated from the DFLOW algorithm include lower (more stringent) effluent
limits for the many constituents that are subject to water quality standards . These would include
heavy metals, for example or, in the future, concentrations of total nitrogen, total phosphorus ,
and increasingly stringent standards for ammonia. Depletion or loss of regulatory low flows also
would have an adverse effect on compliance with the temperature standard. For some of these
constituents, a requirement that the Mulberry Facility meet stream standards without the benefit
of dilution could exceed the capabilities of the facility, which would lead to a regulatory demand
for major changes in the facility.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 16 of 51
Failure of the Mulberry Facility to meet standards could create new 303 (d) listings for the
Poudre River below the discharge or exacerbate recognized water quality problems that currently
exist. Knowingly contributing to the increase of concentrations in a 303 (d) listed segment is not
allowed by the regulatory authority. See 40 C .F.R. 230 . 10(b)( 1 ) (The Corps cannot permit a
project if it contributes to a violation of water quality standards) .
Recommendation : Northern should be required to guarantee a minimum flow of 2 cfs at the
Mulberry Facility' s point of discharge to ensure that historical low flows are maintained on a
daily, monthly, and annual basis for both acute and chronic conditions at the point of discharge.
This should be achieved with accurate flow monitoring of water that merges with effluent form
the Mulberry Facility. Alternatively, Northern should agree to bear the cost of renovating the
Mulberry Facility as needed to comply with stream standards in the absence of effluent dilution.
2.3.2 Flows for the Mulberry Water Reclamation Facility Were Calculated
Incorrectly and Must Be Corrected
Cache la Poudre River Water-Quality Analysis Effects Report Section 3.4. 1
"Low flow values were calculated using the EPA software package DFLOW
(v4. 0; Rossman, 1990). This software allows the calculation of acute and chronic
low flow values from a series of daily flow values. The acute low flow (1 e3) used
to develop WQBELs for acute conditions is the one-day low flow with a three year
recurrence interval. WQBELs for chronic standards use the chronic low flow
(30e3), which is a 30-day average low flow with a three year recurrence interval.
The WQBEL for the maximum weekly average temperature (MWAT) is based on
the 7-day average low flow with a three year recurrence interval (7e3).
Individual monthly low flow values are used as input values for the ammonia and
temperature WQBELs. Annual low flow values, calculated as the minimum of the
monthly low flow values, are used for other WQBEL calculations. A 26 year
period (November 1979 through October 2005) of daily flow values was used for
the calculation of low flow values. Monthly low flows from the CTP model were
disaggregated to provide this 26 year period of daily flows. The methods and
basis for this disaggregation are described in Hydros (2018c). In the case that
the acute low flows calculated from DFLOW were higher than the corresponding
chronic low flow, the acute low flow was set to the chronic low flow. This
methodology is consistent with methods used by CDPHE (CDPHE, 2011). "
Cache la Poudre River Water-Quality Analysis Effects Section 4.2.4 (Table 6)
Statement: "Table 6. Maximum WWTF Discharge Rates (cfs) for Current (Run 1)
and Future (Run 2) Conditions "
Facility Name Run I Run 2
Mulberry 3. 8 5. 7
Boxelder 5. 5 8. 0
Windsor 2. 0 2. 0
Carestream 2. 0 2. 0
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 17 of 51
Front Range Energy 0. 46 0. 46
Greeley 21. 8 34. 6
Leprino 0. 99 0. 99
Comment: Estimates of the effects of Alternative 2M on effluent limits at the Mulberry Facility
were made incorrectly with historical effluent flows rather than with design capacity effluent
flows, which are higher, as required by the Colorado Water Quality Control Division for
permitting purposes . Additionally, regulatory low flows for permitting of the Mulberry Facility
facility were modeled on the basis of a 26-year upstream flow record, which obscures variance
across individual 10-year intervals, as used in permitting.
Recommendation : The analysis must be revised based on the above comments before a CWA
permit can be issued by the Corps. See 33 C .F .R. 325 , Appendix B , Section 9 .B . 13 (The Corps
"should consider all incoming comments and provide responses when substantive issues are
raised which have not been addressed in the final EIS . ") ; Alliance to Save the Mattaponi v. U. S.
Army Corps ofEng 'rs, 606 F. Supp. 2d 121 , 132 (D.D . C . 2009) (requiring Corps to "demonstrate
that it has considered significant comments and criticisms by explaining why it disagrees with
them; it may not dismiss them without adequate explanation.") .
2.3.3 Poudre River Water Quality Based Effluent Limits Should Be Analyzed
FEIS Section 5.3.4.5
"The constituents, temperature, and ammonia WQBEL analysis and calculation of low
flows provides an approximation of values based on water quality and temperature
modeling and predicted flows (Hydros 2018H). Results of the analysis for the eight
WWTFs on the Poudre River for Future Conditions Effects and Cumulative Effects
should be considered as the estimated direction and relative magnitude of change for
comparison of alternatives, rather than absolute values. "
Examples of model results of adverse stream impacts in Segment 11 are found in FEIS
Section 5 . 3 .4 .2 . 5 (Total Nitrogen) and FEIS Section 5 . 3 .4.2 . 6 (Total Phosphorus).
Examples of model results of increased WQBEL values are found in FEIS Section
5 . 3 .4. 5 . 1 (Mulberry Facility) and FEIS Section 5 . 3 .4. 5 .2 (Drake Facility) .
Comment: The water quality modeling completed for the FEIS does not quantitatively describe
the forecasted changes in water quality constituent concentrations in Segments 11 and 12 of the
Poudre River. Rather, it merely describes the direction and relative magnitudes of change that
the project alternatives will have on the Poudre River water quality. An EIS must properly
consider the effects of a proposed action which requires "some quantified or detailed
information"; general statements about possible effects "do not constitute a hard look. "
Klamath-Siskiyou Wildlands Ctr. v. Bureau of Land Mgmt. , 387 F. 3d 989, 993 -94 (9th Cir. 2004)
(holding that while qualitative statements at times are suitable, there are "clearly variables that
can be quantified") .
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 18 of 51
This omission is important because water quality based effluent limits ("WQBEL") calculations
are based on the water quality of the stream receiving the discharge in addition to impacts from
reduced stream flows. If there is degradation from NISP activities of stream water quality at a
discharge outfall, it will result in more stringent effluent limits for the discharger when the
permit is renewed. The water quality modeling results predict some adverse impacts to Segment
11 of the Poudre River, where both the Mulberry Facility and the Drake Facility have permitted
discharges . The WQBEL analysis in the FEIS confirms that these reduced flows and water
quality impacts from NISP will have an adverse impact on the operations of Mulberry and Drake
Facilities, but do not provide a quantitative net effect. Furthermore, it clearly states that outputs
should not be compared to regulatory standards and are for alternative comparisons only.
Without a quantitative description magnitude, duration and frequency of changes caused by
NISP for key water quality constituents and without correcting errors in WQBEL calculations
(See comment 2 . 3 .2), it is impossible for Fort Collins to estimate the impact the of these likely
changes to future wastewater discharge permit limits or to estimate the associated financial
impact the Fort Collins would incur because of required upgrades to meet those new stricter
limits . It is expected however, that even small negative changes in receiving water quality could
translate to very large financial impacts, as a direct result of NISP .
Recommendation : Northern should be required to prepare a quantitative estimate of net impacts
to Fort Collins ' effluent limits for all water quality constituents included in the City' s current
wastewater discharge permits, including industrial pretreatment operations, to inform planning
process and enable estimation of potential financial impacts to Fort Collins . Without a
quantitative analysis, Northern cannot fully and adequately assess the impacts under NEPA and
the CWA. Wyoming Outdoor Council v. U. S. Army Corps of Eng 'rs, 351 F . Supp . 2d 1232,
1244 (D . Wyo. 2005) (explaining that "impacts to water quality should be considered when there
is the potential that a § 404 permit will significantly affect water quality") ; see also San Juan
Citizens All. V. U. S. Bureau of Land Mgmt. , No. 16-cv-376-MCA-JHR, 2018 WL 2994406, at
* 18 - 19 (D .N.M. June 14, 2018) (holding that by failing to quantify the impacts of water quantity,
BLM "failed to meet its duty to take a hard look at the environmental impacts of the proposed
action") .
[Remainder of Page Left Blank Intentionally]
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 19 of 51
SECTION 3 : GEOMORPHOLOGY-RELATED COMMENTS
The Poudre River' s geomorphological response to Alternative 2M is a key concern for Fort
Collins because it directly affects flood risk and stream functions . The following comments
describe the City' s concerns over the accuracy of the predicted impacts on flood risk and Poudre
River health and function that are described in the FEIS .
Fort Collins is a national leader in flood management. Decades of strategic investments in
reducing flood risks have resulted in Fort Collins being one of only seven communities in the
United States with a FEMA Community Rating System ("CRS") score of 2 or lower, and the
only Colorado community with a CRS score under 5 . The Class 2 CRS rating results in many
benefits including a 40% reduction in flood insurance premiums in Fort Collins .
To ensure that Fort Collins ' nationally-recognized flood management program continues to be
effective, the Poudre River' s capacity to carry flood flows must be sustained. The Poudre ' s
capacity to carry flood waters fundamentally depends on: 1 ) maintaining the depth and width of
the river channel, and 2) minimizing increases in resistance to flow. Unless capacity reductions
are adequately addressed, flood risk will be increased in Fort Collins .
Aquatic and riparian functioning condition are directly reliant on geomorphic condition as well.
Fish and riparian birds depend on insects that emerge from the bottom of the river as a critical
food source. If the spaces between the substrate of rocks on the bottom of the river (also known
as the river "bed") become clogged with sand and silt, then many of these types of river insects
will be reduced in numbers and the food base will increasingly become dominated by more
worm-like species that are a less preferable food source for cold water and transition zone fish.
In a healthy river, annual flows that fill or nearly fill the river channel clean and rejuvenate the
river bed. The spring flows that fill or nearly fill the river channel have the power to flush away
sand and silt between rocks and open up spaces in the river bed that provide safe habitats with
plenty of dissolved oxygen for river insects to grow and for fish to spawn. If the power of these
annual floods is reduced by the water diversions proposed for NISP, the river could cross a
threshold where the spaces between the gravels in the river bed are rarely cleaned and the insect
and spawning habitats are no longer maintained often enough to support the life cycle needs for
various river life. The end result would be a loss of essential habitat and food sources for many
animals and these effects could cascade throughout the river ecosystem
The flows that maintain the river' s capacity to carry floods are the same flows that clean the river
bed and maintain the food base for trout and birds . Thus, effective management and
maintenance of peak river flows in terms of how often and how long they occur year by year can
create a win-win situation: valuable benefits for flood management, infrastructure, recreation,
and wildlife.
Fort Collins has significant concerns about the conclusions in the FEIS and these concerns are
supported by internationally renowned subject matter experts and based on FEIS flow data,
fundamentals of geomorphic theory, local analysis, and other observational lines of evidence.
Fort Collins ' perspective, based on FEIS hydrology, is that:
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 20 of 51
• NISP will reduce the river' s capacity to move sediment through the City.
• NISP will accelerate the establishment of woody vegetation along the river channel,
thereby reducing the capacity of to convey flood waters in the river channel .
• NISP will reduce the flows that clean the river bed and maintain the food base for trout,
birds, and other wildlife (in terms of both how often and how long the flows do the work
of cleaning the river bed) .
The interplay between water and physical elements (geomorphology) in a post-NISP world will
determine outcomes for both flood risk and ecosystem health. For this reason, Fort Collins is
relying on underlying geomorphic analyses to demonstrate logical internal connections, the use
of substantiated theories, observational models that include the full suite of field evidence and
consistent reporting across FEIS documents . Fort Collins remains extremely concerned that
NISP FEIS and associated geomorphic analyses does not meet this criterion. Fort Collins
remains concerned that NISP will cause measurable changes to channel size and the river' s
physical condition and that the FEIS inadequate analyses lead to underestimation of impacts and
insufficient mitigation.
Fort Collins has reviewed the FEIS and related reports to understand the assumptions, methods ,
analyses, and conclusions reached regarding the current conditions of the Poudre River and the
potential impacts of NISP operations . The Stream Morphology and Sediment Transport
Technical Report presented conclusions on impacts to the Poudre River from NISP flow
operations, including conclusions pertaining to potential impacts to various environmental flows,
sediment transport, vegetation encroachment, and channel narrowing.
In response to deficiencies in those reports and conclusions , additional analyses were performed
to garner a better understanding of how NISP might impact resiliency and flood risk in Fort
Collins, as it pertains both to the Poudre River and the people affected by its flood storage
benefits, recreational values, and ecological functions . These additional analyses included
hydraulic modeling of a wide range of flow conditions in the river, calculations of bed mobility
and sediment transport capacity, historic data review, and field observations and measurements .
The results of these analyses are presented and interpreted in Appendix B (referred to herein as
the "Fort Collins Geomorphology Report") . From these analyses, three general comments have
been identified and are discussed below.
3. 1 GENERAL GEOMORPHOLOGICAL COMMENTS ON THE FEIS
3 . 1 . 1 Inconsistencies and Inadequacies in Geomorphic Analysis in the FEIS
Stream Morphology and Sediment Transport Technical Report Must Be
Addressed
Comment: The basis for the selected geomorphology methods and conclusions are not
supported by the best available science and data. See 40 C .F.R. § 1500 . 1 (b) (NEPA requires
"high-quality . . . accurate scientific analysis") ; New Mexico ex reL Richardson v. Bureau of
Land Mgmt. , 565 F . 3d 683 , 713 ( 1Oth Cir. 2009) (explaining that an agency must consider "the
relevant data and articulate a rational connection between the facts found and the decision
made") . The Corps cannot rely on inaccurate data or assumptions . See Native Ecosystems
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Council v. U. S. Forest Serv. , 418 F . 3d 953 , 964-65 (9th Cir. 2005) (holding that "to take the
required ` hard look' at a proposed project' s effects, an agency may not rely on incorrect
assumptions or data in an EIS"); see also Sierra Club v. Van Antwerp, 526 F . 3d 1353 , 1368 n. 6
( 1 lth Cir. 2008) (stating that the Corps "must independently evaluate the information" and "shall
be responsible for its accuracy") (quoting 33 C .F .R. § 325 App. B . § 8(f)(2)) . Also, the
interpretation of those results is not always consistent with the results themselves .
A wide range of flow magnitudes was used during the studies leading up to the FEIS and
assumed to satisfy the flushing criteria. The figure below presents a graphic illustration of how
the range of flows required to meet the selected definition of flushing flows changed throughout
the process leading to the FEIS . (In this figure, "FFR" refers to Flushing Flows Report, 2017 .)
The range is ultimately a reflection of shifting definitions, changing assumptions , and an
apparently arbitrary selection key values .
10000
9000
8000
� Range
7000 - of
6000 Flushing
o Flows
0 5000 Average
�_ 4000 Flushing
.C: Flow
Ln D 3000 Result
2000
1000
0
SDEIS : Using every FFR : Using riffle cross FFR : Using Q2 as
cross section and D50 sections and ( 2 - Baseline Flushing Flow
64mm ) values
The final range of flushing flow values used in the FEIS ignores the detailed sediment transport
calculations presented previously in EIS documents that reflect the considerable complexity and
variability of sediment transport dynamics along the Poudre River. The value used in the FEIS
appears to be a value based on a flow recurrence interval, though the basis for that interval is
uncertain. Given the long history of flow extraction and channelization on the Poudre River
through Fort Collins, recurrence intervals are moving targets that poorly characterize the modern
hydrologic and sediment regimes . Furthermore, Fort Collins is unaware of any peer-reviewed
justification for the determination of a flushing flow value based on a particular recurrence
interval discharge. While there is no absolute legal requirement that a methodology be peer
reviewed, an agency must acknowledge and discuss any flaws in its chosen method. All. For the
Wild Rockies v. Bradford, 720 F . Supp. 2d 1193 , 1222 (D . Mont. 2010) (holding that the "Forest
Service [could] not simply rely on [a study] as the best scientific information available; it must
acknowledge and discuss any flaws") .
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The FEIS also dismisses many of the impacts on the assumption that the Poudre River is
sediment supply-limited. The FEIS includes similar statements when presenting the results of
technical analyses, but then disregards or downplays them in the FEIS ' s conclusions . The
argument for minor impacts hinges on the assumption that the Poudre River through Fort Collins
is "sediment supply limited. " However, this assumption is unfounded because sediment supply
has not been quantitatively assessed to verify the asserted supply limited classification. The
CWA and NEPA require that the Corps and Northern meaningfully assess these impacts and
correct errors pointed out by Fort Collins, including the flow values used in the FEIS . See Sierra
Club v. United States Army Corps of Engineers, 701 F .2d 1011 , 1029 (2d Cir. 1983 ) (An EIS
must ensure "the integrity of the process of decision by giving assurance that stubborn problems
or serious criticisms have not been ` swept under the rug. "') .
The results of additional Fort Collins analyses show that the flood capacity and habitat quality of
the Poudre River is susceptible to episodic inputs of sediment. Further, the reductions in
sediment transport capacity produced by the selected alternative and proposed mitigation plan
will exacerbate the channel narrowing and loss of flood capacity currently observed in the Fort
Collins reaches of the Poudre River.
While a stronger physical signature of sediment storage may exist downstream of I-25 , the
Alternative 2M will reduce the transport capacity of river reaches in Fort Collins to levels below
those now experienced downstream of I-25 . This will exacerbate the channel narrowing and
sediment storage already observed upstream through Fort Collins . The FEIS disregards this key
conclusion based on an unsupported assumption that the channel is sediment supply limited. See
Or. Natural Desert Assn v. Jewell, 840 F . 3d 562, 570 (9th Cir. 2016) (finding a violation of
NEPA because "inaccurate information and unsupported assumption materially impeded
informed decisionmaking and public participation") . Risk and consequence are extremely high
for Fort Collins due to broad implications for impacts to flood mitigation, infrastructure,
recreation, and wildlife habitat.
3 . 1 .2 Inadequacies in Geomorphic Analysis Must Be Addressed
Comment: The modeling methods and assumptions used in the FEIS are inadequate to predict
and evaluate the impacts of NISP on sediment flushing and flood risk. The incorporation of
other assessment methods that add context to and qualify the modeling calculations, lead to
conclusions contrary to those presented in the FEIS . Under the CWA, when the Corps receives
contradictory evidence, it must "conduct a thorough examination of the record [and] explain why
it has rejected or ignored contradictory evidence ." Islander E. Pipeline Co. v. Conn. Dep 't of
Envtl. Prot. , 482 F. 3d 791 99- 100 (2d Cir. 2006) .
Uncertainty in the shear stress calculations and comparison with the tracer rock observations
suggest that capacity and competence calculations, performed with 1D model hydraulics, are
alone insufficient for the determination of flushing flows. Other evidence needs to be considered
along with more rigorous analytical tools . It is apparent from field investigations (presented in
the attached Fort Collins Geomorphology Report) that a biofeedback loop is occurring on the
Poudre River through Fort Collins and the results presented in the EIS documents indicate that
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NISP will exacerbate this channel narrowing behavior and ultimately increase flood levels and
risk to private property and infrastructure located in the floodplain.
3 . 1.3 Additional Analysis Suggest that the FEIS Substantial Underestimates
Alternative 2M ' s Impacts
Comment: The evidence presented in the attached Fort Collins Geomorphology Report establish
that the anticipated changes to Poudre River flows from Alternative 2M will reduce flood
carrying capacity and simultaneously degrade riverine habitat. The expected stream response to
Alternative 2M will include rapid vertical accretion of bars at the channel margin leading to a
reduction in conveyance; recolonization of the newly formed bars by vegetation leading to
increased roughness; and an associated reduction in channel topographic complexity, leading to a
homogenous, more canal-like Poudre River. The cumulative impacts equate to increased flood
risk and decreased ecologic function through Fort Collins . A discussion of the cumulative
environmental impacts is an essential part of the environmental review process . Colo. Envtl.
Coal. v. Office of Legacy Mgmt. , 819 F . Supp. 2d 1193 , 1213 - 14 (D. Colo . 2011 ) (holding that
the agency had failed to adequately address the cumulative impacts of its decision) .
As a national leader in flood management, Fort Collins has made substantial investments in
mitigation of flood hazards along the Poudre River corridor. Fort Collins has embraced the
vision of a healthy and resilient Poudre River. Fort Collins has official policy to support such
health and resiliency improvements. Increases in flood risk and alterations that require increased
maintenance (cost and time investment) to sustain current levels of flood protection are not
acceptable and impose additional risk on Fort Collins . Additionally, changes to flushing flows
are unacceptable when they notably reduce the ability of the channel to maintain the current
active width, as this limits in perpetuity Fort Collins ' ability to achieve its vision of a healthy and
resilient river
Sweeping fine particles from the surface of the river bed is not a sufficient flushing objective for
Fort Collins, nor is it based in a realistic understanding of how the channel bed functions .
Without effective channel maintenance flows, increases in channel roughness resulting from
encroachment of woody vegetation that increases in height and stiffness over time will lead to
reduced flow conveyance in the channel, channel straightening, and a reduction in habitat
diversity. As predicted by Fort Collins ' Ecological Response Modell , the channel will shrink
and become more limited in its capacity to absorb and convey large flood events within current
floodplain extents . Fort Collins will need to invest more heavily in maintenance to avoid
increased flood hazards. The proposed mitigation measures are unrealistic ; conveyance will be
lost in locations where adjacent land is not available to be repurposed for flood mitigation.
Overall, Fort Collins ' additional analyses indicate that:
• Sediment transport processes on the Poudre River may be currently functioning more
than the FEIS and associated reports indicate; and
1 See https ://www. fcgov.com/naturalareas/eco-reWonse.php
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• The Poudre River has adequate sediment supply to generate substantial accumulation
along the channel margin, building new surfaces upon which vegetation can colonize and,
as a consequence, triggering further sediment storage.
Field-based results have also underscored the uncertainties inherent in analyses of river bed
mobilization based on one-dimensional and uncalibrated hydraulic models . The FEIS relies
heavily on computer modeling alone, but the additional Fort Collins analyses (including the
attached Fort Collins Geomorphology Report) show that these tools in isolation are insufficient
to understand the impacted river processes and must be tempered with field evidence. See
Mountaineers v. U. S. Forest Serv. , 445 F . Supp. 2d 1245 , 1250 (W.D . Wash. 2006) (holding that
an agency failed to adequately assess the cumulative impacts of a proposed action because no
actual "in-the-field study" had been conducted and the agency had simply relied upon a general,
hypothetical analysis) . These findings suggest that the predicted impacts of Alternative 2M on
current conditions presented in the FEIS may be significantly underestimated.
3 .2 ADDITIONAL SPECIFIC GEOMORPHOLOGICAL COMMENTS ON THE FEIS
3.2. 1 Peak Flow Operations Program Is Unclear and Its Adverse Impacts Are Not
Considered
FEIS Section 4.4.3 . 1 .2
"The Peaks Flow Operations Program would reduce the impacts of Alternative 2M on
flushing flows that are ciritcal to spawning habitats for fish. [. . .J From a hydrologic
perspective, the Peak Flow Operations Program would increase the frequency of peak
flows to more closely resemble the recurrence interval for historic hydrologic conditions.
It would also lessen the impacts of Alternative 2M on geomorphology and sediment
transport associated with reduced occurrence of peak flows (2 % exceedance and I- to 2-
year floods).
[. . .J The Peak Flow Program does not specify what ither flow range would be reduced in
order to maintain firm project yield. Without additionla detail, the overall impact of
Alternative 2M with the Peak Flow Operations Program on overall stream morpholpgy
and sediment transport id unknown. In the absence of more detailed informaiton, the
impact of Alternative 2M with the Peak Flow Operations Program would remain minor
upstream of I-15 and moderate downstream of I-25, as described in the impact summary
(Table 4-50). The overall effect on flushing flows after considering the Pleak Flow
Operations Plan would be minor. "
FEIS Section 4.2.3.3. 1
"Northern Water developed a Peak Flow Operations Program to minimize the potential
effect of NISP operations on peak flows, which act to flush out course gravels and help
maintain spawning habitat. [. . .J Following the peak flow event, Northern Water would
attempt to increase diversions and make up a portion of the volume bypassed assuming
the Grey Mountain water right remained in priority. 11
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FEIS Section 4. 1 . 1 .3
"Effects determinations include consideration of avoidance, minimization and
enhancement measures that would either avoid causing an effect or minimize the effects
intensity. "
FEIS Section S-24.
"Forgoing of diversions to implement the peak flow operation program is not intended to
reduce overall project yield. To maintain firm yield of the project, Northern Water would
increase diversions in the Poudre Valley Canal up to 1, 700 cfs immediately following the
peak flow operational period. Additional days of diversion at the end of the runoff
hydrograph may be necessary to make up the bypassed volume. Compensation of the full
bypassed volume would ideally be made up within the same year if conditions were
favorable. If the bypassed volume was not recovered within the same year, it would be
made up in subsequent years through increased diversions ."
Comment: One of the key principles presented throughout the FEIS is that changing flows will
affect Poudre River ecosystems and habitats . While Fort Collins appreciates the effort taken by
Northern to develop the Peak Flow Operations Program, Fort Collins has certain key concerns .
First, the Peak Flow Operations Plan is described in the 2017 Fish and Wildlife Mitigation and
Enhancement Plan. ? However, there is some uncertainty regarding how certain aspects of the
Peak Flow Operations Plan will be implemented, which results in uncertainty regarding how
many peak flow bypasses will result. This leaves Fort Collins with uncertainty over the future
hydrology and the degree to which flushing flows will occur. The following is an example of
this uncertainty:
• Table 6 of the 2017 Fish and Wildlife Mitigation and Enhancement Plan describes that
the operational tiers will be determined partially based on whether the streamflow
forecast indicates if the streamflow will be greater or less than the average. However,
how the streamflow will be forecasted and how the average will be calculated is not
explained.
Second, it appears that Project diversions following peak flow bypasses will be increased, which
will likely have different impacts that do not appear to have been analyzed. This time period
following peak flows ("descending limb") is ecological and recreationally significant. However,
impacts to the Poudre River from such a modified descending limb are not analyzed in the FEIS .
The conceptual image below is Fort Collins ' current understanding of how NISP ' s peak flow
operations Program may affect current flows . The impacts to the descending limb will shorten
duration of peak flows which will result in impacts to geomorphology, riparian and wetland
habitat. It may cause more rapid declines in river flow, which could preclude successful
establishment of cottonwood seedling. Rapid declines in flow could also cause stranding of fish
and affect critical life cycle behaviors such as spawning and migration patterns of the small
2 Under Tier 2a of Peak Flow Operations Program, bypasses will occur only to the extent that it is necessary to bring
the flow at the Canyon gage up to 2,800 cfs. As indicated in previous comments, Fort Collins disagrees with the use
of the 2,800 cfs value for flushing flows.
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native fish. It could reduce sediment transport and increase aggradation through Fort Collins
which would result in increased flood risk. Last, if flows at the tail end of the descending limb
are reduced, there will be a greater impact on boatable day. This makes it difficult to understand
Project impacts and the sufficiency of mitigation.
1
I I I
I 1 1
1 I
1
_O
May June
a codidgual image of future flows with NISP compared to
today' s flows
3 .2.2 Reduction of Scouring Flows have Been Ignored as an Important Factor in
Maintaining Channel Capacity
Stream Morphology and Sediment Transport Technical Report Section 2.7.2
"Reduced duration of flows that generate motion of bed material has implications both
upstream and downstream of I-25. In both cases it implies that the river is predicted to
move less sediment through the system under Alternative 2M than under current
conditions hydrology. [. . .J
As a second order effect, the truncated periods of bed material motion is predicted to
decrease the opportunity for scouring of in-channel vegetation from bars, islands and
channel margins. [. . .J
Where the supply of material that makes up the bed is limited, such as in the Fort Collins
and Laporte Reaches, reduced movement of bed material under Alternative 2M is likely
to lead to lower rates of change of in-channel bars, islands, benches, and channel form.
I. . .I
There are very few cases where an isolated occurrence of bed material motion is
predicted to be lost altogether. This leads to the general finding that while the duration
and frequency of bed material motion is predicted to be less for Alternative 2M, the time
between occurrences of bed material motion is not greatly impacted by Alternative 2M.
The spells analysis suggests that the time between occurrences of bed material motion is
not generally increased under Alternative 2M, so to the extent that colonization of
vegetation is dependent on the existence of a stable substrate, no significant change in
the rate or extent of new colonization is expected. "
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Comment: The FEIS states that the ability of flows to scour away encroaching woody
vegetation (to reduce channel narrowing and roughening) depends on the duration of scouring
flows. The FEIS also states that Alternative 2M will reduce the duration and frequency of
scouring flows, but not generally increase the time (spells) between occurrences of scouring
flows. However, the FEIS then states that only the existence of a stable substrate affects
encroaching woody vegetation. This underlies the FEIS ' s conclusion that Alternative 2M will
not cause significant change in the rate or extent of new vegetation encroachment, particularly in
reaches that are claimed to be sediment supply limited.
These FEIS statements are contradictory and the conclusion is not supported by evidence. Motor
Vehicle Mfrs. Assn v. State Farm Mut. Auto. Ins. Co. , 463 U. S . 295 43 ( 1983) (holding that an
agency acts arbitrarily and capriciously when its "explanation for its decision . . . runs counter to
the evidence before it") . If the effectiveness of scouring flows is duration dependent and
Alternative 2M will reduce duration, then it follows that Alternative 2M can lead to increased
vegetation encroachment. This direct link between duration and vegetation scour has widespread
concurrence in peer-reviewed scientific literature (Pasquale et al. , 2011 ; Edmaier et al. , 2010) .
The FEIS makes no link and points to no evidence in the available body of literature on time
between occurrences and vegetation scour. Alternative 2M will decrease peak flow duration,
magnitude, and frequency — all of which are documented in scientific literature as having the
potential to increase vegetation encroachment and therefore flood risk (Poff and Zimmerman,
2009) .
The assertion that upper reaches of the Poudre River are sediment supply limited is also not
supported by evidence. Utahns for Better Transp. v. U. S. Dep 't of Transp. , 305 F . 3d 1152 , 1187
( loth Cir. 2002) (holding that a Corps Section 404 decision was arbitrary and capricious because
it was not supported by record evidence) . Recent events and watershed disturbances including
fires in the upstream watershed have resulted in substantial storage of sediment in the river
channel and the formation and expansion of new bars and vegetated islands (see the attached
Fort Collins Geomorphology Report) . In the lower Fort Collins reaches, particularly from
Prospect Road to I-25 , current conditions include substantial fine sediment aggradation.
Furthermore, woody vegetation establishment is widely documented to occur in rivers with low
sediment supplies.
Increased vegetation encroachment will increase flood risks through Fort Collins because woody
vegetation increases flow resistance and causes sediment to accumulate. This increases flooding
width and depth, as well as reduces the river' s capacity to safely carry floods through Fort
Collins unless additional capacity is provided to offset the loss.
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3 .2.3 Reduction of Scouriniz Flows Has Been Ignored as an Important Factor in
Maintaining Channel Capacity
Stream Mor ology and Sediment Transport Technical Report Section 2. 10
Possible Impact Laporte Reach Fort Collins Reach
(plus Timnath Reach upstream of
I-25)
Loss of morphologic complexity Bed material moves at about 28% of the cross sections under both current conditions and Alternative 2M
hydrology. Average duration of bed material movement is reduced by 18% for Alternative 2M.
Spatial variability of biotopes is provided by existing bed forms and the proliferation of diversion
structures. Spatial variability is predicted to be maintained under Alternative 2M, but temporal variability
is predicted to be reduced because of reduced flow variability.
Channel contraction Sediment transport potential is predicted to be reduced throughout the river under Alternative 2M
Under Alternative 2M total transport potential is reduced by 5% to 30%. Transport potential to move sand
and gravel is reduced by 3% to 305, and 8% to 31 %, respectively, under Alternative 2M
Together with the reduced sediment transport Sediment transport potential is reduced by around
capacity, a slight reduction in effective 40% across a broad range of flows but the effective
discharge suggests an ongoing tendency toward discharge remains unchanged at about 2,000 cfs. The
channel contraction in this reach as the result of effective discharge suggests an ongoing trend of
Alternative 2M. But the response is predicted to channel contraction, but this is the same for current
be constrained by the limited supply of material conditions hydrology and Alternative 2M and channel
available for deposition. A model based on contraction is predicted to continue to be constrained
observed historic response predicts that the by the limited supply of material available for
reach is supply limited and that processes of deposition.
channel contraction will be insensitive to the The reduced duration of high flows suggests an
changes in sediment transport potential that are increase in vegetation persistence. Vegetation may
attributable to Alternative 2M. cause channel contraction by colonizing bars and
The persistence of in-channel vegetation is channel margins but there is little change in the
expected to increase and this could encourage average time between high (scouring) flows between
channel contraction even without abundant current conditions and Alternative 2M, so no rapid
sediment. However, the average time between expansion in vegetated area is expected. The spells
scouring events is not greatly altered so the rate analysis suggests that the time between occurrences of
of growth of vegetated areas should not be bed material motion is not generally increased under
greatly affected. The spells analysis suggests Alternative 2M, so to the extent that colonization of
that the time between occurrences of bed vegetation is dependent on the existence of a stable
material motion is not generally increased substrate, no significant change in the rate or extent of
under Alternative 2M, so to the extent that new colonization is expected.
colonization of vegetation is dependent on the In the reach between Coy Ditch and Lemay Avenue,
existence of a stable substrate, no significant channel contraction is more likely to be temporary in
change in the rate or extent of new colonization response to pulses of sediment or dry periods. There
is expected. will be a tendency in this reach for the river to
develop a
temporary smaller channel within the larger cross
section.
Comment: The FEIS states that Alternative 2M would reduce the total capacity to transport
sediment over a period of years by 5 % to 30% in the Laporte and Fort Collins Reaches . The
FEIS also states that capacity to transport sand and gravel would be reduced by 8 % to 3 1 % in the
Fort Collins Reach, and that sediment transport potential in the Fort Collins Reach would be
reduced by approximately 40% . Despite the results of these sediment transport calculations , the
FEIS predicts that channel contraction will be lessened due to the limited supply of sediment
delivered from upstream.
The assertion that upper reaches of the Poudre River are sediment supply limited is not supported
by the evidence. Earlier arguments have been based on the notion that upstream of I-25 the
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Poudre River has a capacity to move sediment that exceeds the supply of sediment from
upstream — and specifically on observations that " [i]n general, the bed is armored with cobbles
and coarse gravels that only move rarely in response to high flow periods" (SDEIS 2013 pg. 9-
4) . Further, the FEIS states that because the coarse material on the river bed is rarely mobilized,
the finer material underneath is rarely released; thus, the river is thought to generally have a lack
of sediment supply upstream of I-25 . This condition is coupled with observations upstream of I-
25 that, "Bars, islands and marginal deposits do form, but signs of consistent, contiguous
aggradation are not evident" (SDEIS 2013 pg. 9-4) . The observations that upstream of I-25 is
sediment supply limited and lacks signs of large scale aggradation ultimately leads to the broad
assertion that aggradation is not a current issue and will not be an issue under future NISP
conditions .
In 2018 , Fort Collins conducted field investigations to provide multiple lines of evidence for
better understanding Poudre River sediment supply upstream of I-25 . The lines of evidence
confirm that the methods used in the FEIS and related reports to estimate the future risk of
sediment build up are inadequate for assessing sediment dynamics on the Poudre River (see the
attached Fort Collins Geomorphology Report) . Analysis results show that the Poudre River is
susceptible to episodic inputs of sediment and that the reductions in transport capacity that would
result from NISP will exacerbate the narrowing and shrinking capacity of the river channel
currently observed in the Fort Collins reaches . The FEIS documents appear to reach this same
conclusion.
The results of Fort Collins tracer rock study (see the attached Fort Collins Geomorphology
Report) suggest that the coarse bed material of Poudre River through Fort Collins is more mobile
than depicted in the FEIS which asserts the bed is largely armored and immobile. Further, the
methods used to quantify the mobility of the river bed did not adequately predict the mobility of
the bed following the 2013 flood and five subsequent wet years . Due to this , high uncertainty
exists in the percentages reported for which cross sections are mobile and how much the
preferred alternative might reduce that number. The result is that the extent to which each of the
alternatives will impact the Poudre River is still not understood. Wild Earth Guardians v. U. S.
Bureau of Reclamation, 870 F . 3d 1222 , 1237 ( loth Cir. 2017) (explaining that NEPA ' s purpose
is to "prevent uninformed agency decisions").
Understanding the physics of whether a channel is sediment supply limited or capacity limited
fundamentally requires a comparison between sediment supply and transport capacity over a
range of flow events (Montgomery & Buffington 1997) . Sediment supply has not been
quantitatively assessed in the FEIS documents . Based on the definitive scientific paper on this
subject (Montgomery & Buffington 1997), the Poudre River would be classified as capacity
limited both above and below I-25 .
Evidence from Fort Collins field investigations showing vegetation encroachment and
aggradation indicate that while historic channel forms have been strongly influenced by land-use
and development, the Poudre River is capacity limited above I-25 during some high flow events
and upstream watershed conditions . Sediment supply, however, is now more episodic in nature
(associated with moderate flows). While a stronger physical signature of sediment storage may
exist downstream of 1-25 , the FEIS predicts preferred alternative will reduce the transport
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capacity of the reaches in Fort Collins to levels below those now experienced downstream of I-
25 , thus exacerbating the channel narrowing and sediment storage currently observed upstream
in the urban reaches.
3 .2.4 Bio-Geomorphic Feedback Loop Has Been Dismissed Upstream of I-25
Stream Morphology and Sediment Transport Technical Report FEIS Section 2. 10
"In overview, the trajectory of the river condition is expected to continue under both
current conditions and Alternative 2Mhydrology.
"Based largely on an observational model of response to current conditions hydrology,
the trends that were identified in the Baseline Report are expected to continue and be
more severe downstream of I-25 than upstream of I-25 because:
• sediment supply in the size fractions relevant for deposition is more limited
upstream of I-25 than downstream; and
• bio-geomorphic processes involving vegetation establishment on benches and
bars prevail more downstream of I-25 compared to upstream.
Assessments of the effects of the Alternative 2M compared to the current conditions
hydrology amplify the trajectory of the river conditions identified in the Baseline Report
reflected in continuing channel contraction, fining of surficial material, and loss of
channel complexity. "
FEIS Section 3.4.2.3.5
"The natural system is often able to accommodate considerable change in its controlling
parameters without a consequential response, until some threshold is reached beyond
which major response is initiated. [. . .J The likelihood of such non-linear response
thresholds can be elucidated by observation or space for time substitution, but accurate
prediction is generally beyond current analytical techniques . . . . in a potentially aggrading
reach, progressive reductions in the frequency of moderate to large flows may initiate
channel contraction until a threshold is reached where the time between flow events
allows vegetation to establish to a point that is resists further removal by flow. "
Comment: The statements above relies on a largely unstudied assumption that bio-geomorphic
feedback loops prevail more downstream of I-25 and presumption that feedback loops upstream
of 1-25 are therefore un-notable. See Or. Natural Desert Assn, 840 F . 3d at 570 (prohibiting
"unsupported assumptions"). The term bio-geomorphic feedback loop describes the self-
perpetuating process where flow reductions cause sediment build up, which creates a narrower
and shallower channel and allows persistent woody vegetation to establish, which over time
locks in sediment(e. g. , via rooting around large rocks), which enables seedlings to become young
trees and grow taller and stiffer, which increases flow resistance and causes more sediment build
up among the young trees, which continues the loop via continued narrowing and vegetation
encroachment.
The FEIS uses a related argument that bio-geomorphic feedback loops are less prevalent
upstream of 1-25 to support recommendations for mitigation downstream, but not upstream of I-
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25 . Fort Collins disagrees with this assertion for two reasons . First, bio-geomorphic feedback
loops have been documented in Fort Collins. Second, the relative argument misses the critical
point that flow reduction commonly triggers these bio-geomorphic processes. This crossing of a
threshold is identified in the FEIS and has been observed on the Poudre River, as well as several
other Front Range systems (e. g. , Left Hand Creek, South Boulder Creek) that have experienced
flow reductions .
Fort Collins has conducted initial investigations and presents two field-based lines of evidence
suggesting Alternative 2M could increase bio-geomorphic processes upstream of I-25 , which
would exacerbate flood risk to Fort Collins via tightening, shrinking, and roughening of the
channel. This impact can render current floodplain maps obsolete and unprotective. Locally,
reduced flows can cause sediment buildup at bridges and culverts, increasing risk of overtopping
and damage and requiring expensive preventative maintenance by Fort Collins . Although NISP
operations will reduce flood peaks, the resultant flood capacity reductions (systemwide via
vegetation encroachment and locally at critical infrastructure) will outweigh any benefits by
increasing flood risk.
First, the Fort Collins Geomorphology Report presents an analysis of historical aerials and pre-
and post-runoff photos that examine vegetation encroachment on channel bars following a large
flood event in 1999 and the subsequent dry years until 2012 . Additionally, the 2013 flood event
was not able to remove much of the woody vegetation that had re-colonized bar surfaces since
1999 . Furthermore, 2018 runoff had little effect on seedlings growing along the channel margin.
These seedlings, if able to survive, then mature, trap additional sediments, and reduce channel
capacity, cycling through the feedback loop . Alternative 2M would likely exacerbate this
pattern.
Fort Collins Geomorphology Report presents a point bar case study documenting one known
bio-geomorphic feedback loop in Fort Collins upstream of I-25 . This point bar investigation
showed a clear pattern of vegetation encroachment from 1999 to present and up to 4 feet of
sediment deposition over that period. Significantly, this bio-geomorphic feedback loop is
occurring in a reach with relatively higher transport capacity (compared to downstream),
countering the FEIS assumption that the river upstream of 1-25 is not at risk of increased
aggradation because it is supply limited. While this bar is located within a reach of relatively
higher transport capacity, it represents channel behavior at a finer scale than captured by the
reach-scale capacity modeling. The dynamics of site-scale features, such as this bar, have the
potential to make significant reductions in transport capacity, especially when located near
critical infrastructure. Alternative 2M is likely to impact the river upstream of I-25 by creating
substantially more analogous, low energy places in the river similar to the examined bar.
An important note is that the deposition seen on the bar is not the result of a singular event (i. e. ,
the 2013 floods) . The photograph in Figure 18 from the Fort Collins Geomorphology Report
shows that around 1 . 5 feet of extra deposition occurred on the bar from the 2013 event.
Therefore, up to 4 feet of deposition observed in 2018 is strong evidence that supply was
available in the years following 2013 and that vegetation that had encroached on these bars is
trapping sediment and reducing channel conveyance. This observation is in direct contradiction
to the conclusion in the EIS documents that the reach is sediment supply limited and shows the
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channel to be susceptible to episodic inputs of sediment, including fine sediments which the
calculations suggest should be moved through the reach. If NISP operations increase the rate of
channel contraction occurring through Fort Collins, the lost conveyance puts Fort Collins at
greater risk to flooding.
3.3. RECOMMENDATIONS RELATED TO GEOMORPHOLOGICAL COMMENTS
Fort Collins makes the following recommendations related to its above geomorphologic
comments .
Northern should be required to provide, at minimum, a complete three-day peak flow in all years .
If the Peak Flow Operations Program remains in effect, Fort Collins requests clarification on the
implementation and effects of the program, including how stream flows are required to be
forecast and how the averages are to be calculated. Northern should also be required to annually
publish notice of how the Peak Flow Operations Program was implemented. Northern should
also be required perform additional mitigation to compensate for the apparent lack of analysis of
the impacts resulting from increased diversions following the peak flow bypass period (under a
complete three-day peak flow or something less under the Peak Flow Operations Program) to
address the apparent lack of analyses of such impacts .
Northern should be required to establish minimization or mitigation for impacts to the
descending limb, given the loss of flows past a three-day period will reduce the overall
probability of occurrence for geomorphic functions .
Northern should be required to work under express thresholds for geomorphic-related adaptive
management items . Subsequently, Northern should be required to perform long-term monitoring
of vegetation encroachment on the Poudre River, in addition to long-term monitoring of channel
narrowing, sediment accumulation, and habitat degradation. If such long-term monitoring
demonstrates an increase in vegetation encroachment, channel narrowing, sediment
accumulation, and/or habitat degradation, Northern should be required to take steps to address
the impacts, preferably through flow-based approaches .
If adequate, flow-based mitigation is not achieved, the City likely need to make expenditures of
$300,000 to $400,000 annually for spring and fall river cleanups, repair of banks damage from
vegetation encroachment, and removal of vegetation and sediment following flood events to
remove blockages at bridges and diversion structures to mitigation the potential for flood risks to
Fort Collins . Northern should mitigate such impacts .
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SECTION 4 : RIPARIAN-RELATED COMMENTS
4. 1 THE POUDRE RIVER IS NOT ON A TRAJECTORY OF INEVITABLE DECLINE
FEIS Section 4.9.8. 1
"All action alternatives would cause reductions inflows and river stages of the Poudre
River which are predicted to accelerate and/or reinforce the well-established trajectory. "
Comment: Fort Collins disagrees with the assumptions and statements that the Poudre River is
on a trajectory of inevitable decline. In the context of mitigation and adaptive management
commitments, Fort Collins emphasizes the need for a proper and integrated understanding of the
systems ' contemporary condition.
Although the FEIS correctly states the Poudre River is compromised by historic and current
human influences, the use of this statement to propose a declining trajectory is overly simplistic,
erroneous, and misleading. The FEIS concludes in many places that the Poudre River is on a
well-established downward decline, and states that this downward trajectory "provides the basis
for comparisons related to potential flow alterations". In the response to comment (3032), the
Corps states that "the Corps did not portray the trajectories as negative or positive, but simply
disclosed the projected trajectories. " It is unclear how "declining trajectory" could be interpreted
as something other than negative. This erroneous representation of the Poudre River serves as
the basis for conclusions in various portions of the FEIS , including stream morphology and
sediment transport and riparian vegetation community. The FEIS often circularly concludes that,
despite potential changes, impacts are minor because the future state is assumed to be worse than
current conditions .
Fort Collins contends that there are many functioning elements and/or reaches that do not match
the FEIS ' s assumption of decline. Current scientific theory and approaches to ecosystem
management utilize the widely accepted paradigm of multiple stable states, acknowledging that
ecosystems can operate under different states or conditions , based on the stressors or disturbance
regimes that occur. Thus, rather than being in a declining trajectory, the Poudre River would be
in a different "stable state" based on the historic and current human influences that are placed on
the river (gravel mining, irrigation diversions, municipal diversions, recreation, etc) . However,
the FEIS argues that historic disturbances have put the Poudre River on a continued downward
trajectory, rather than acknowledging the potential for an alternate stable state under current
conditions . The FEIS is therefore not in line with accepted scientific theories, nor is it in line
with data collected by Fort Collins .
Fort Collins presents the River Health Assessment Framework ("RHAF") as an integrated
assessment framework for this complex dynamic system. The RHAF is an information
framework that was used to develop the first State of the Poudre Report. This framework allows
for incorporation of a spectrum of data and analyses types to track river health and function
depending on the scope and needs of a given program. The RHAF is a close adaptation of the
FACstream method which was developed through an EPA 104(b)(3 ) state wetlands grant
program as well as funding from Colorado Water Conservation Board. The results from the first
State of the Poudre can be presented at many scales, but even at the coarsest scale (presented
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below) there is a strong indication this system maintains both strengths and weaknesses that
should not be dismissed with the application of a declining trajectory.
Zone CNVM Rural 1 0 ru�eoan
Reach 1 2 3 4 1 5 6 1 7 1 8 9 1 10 11 1191
F low Reg lme 77 75 75 74 74 73 73 7Z 7Z T 7777
Sedlment Regime FM54 54 53 82 K 53 52 81 79 79 80 79 79 79 79 79
Water Qua Itty 77 • • • • 57 57 57 87 ® 89 89 89 88 55 55 5E 53
FIoodplaIn Conn ectivlty 75 82 55 71 65 6Z 61 87 50 67 73 70 77 50 98 52 T-
RlparlanCondltlon 85 97 55 ' ? 1 64 69 7E 63 65 70 71 73 70 76 71 68
RHerForm 82 74 72 68 67 74 7E 70 75 74 75 777 F4 75 (19
Re5111ence 82 79 76 >< 1 75d 67 11 5 69 79 77 74 75 71 75 74 68
PhySICalStnrzture 76 74 71 5 72 6L 77 79 77 51 70 77 76 74 74 E9
Aquatic We 80 81 75 7E 7E I 7E 77 1 75 7Z 1 741 79 79 85 85 7M
R Mer Health 52 79 75 1 74 75 70 1 74 75 70 74 1 74 75 1 76 1 70 _M 76 T3
EU 7E 74 75
Grading Scale
100-90
B+ I 89-87
9 1 86-83
82-80
- 79-77
76-73
C- 72-70
D!F 69 or lower
Results of the 2017 State of the Poudre Report (reprinted from Table 4. 1 ) .
Recommendation : Mitigation should demonstrably offset impacts at each level of the stream
functions pyramid based on contemporary conditions, not a speculative future condition. In
order to effectively implement Northern' s existing commitments for mitigation and adaptive
management, and to better implement the recommendations in these comments, Fort Collins
recommends that the Corps imposes a mitigation objective and response mechanism for each
impacted level/component of the Stream Functions Pyramid (see https ://www. ppa. gov/cwa-
404/stream-functions-p ry amid) . The RHAF is based on concepts inherent in the Stream
Functions Pyramid so the RHAF Indicators and Metrics closely align with concepts presented in
the Stream Functions Pyramid.
Fort Collins intends to continue to use the RHAF and to place additional quantitative measures
within the RHAF to monitor the ongoing health of the river under pre and post-NISP conditions
This will inform the City' s perspective on signals and needs for adaptive response actions . The
Corps could apply the RHAF in a similar fashion to inform discussions and decisions with the
adaptive management stakeholder group. This would enable the Corps to track as-built effects of
NISP and more closely meet mitigation requirements and commitments as outlined in the 2017
Fish and Wildlife Mitigation and Enhancement Plan. The City would welcome the opportunity
to collaborate on these parallel monitoring and management efforts .
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4.2 UNMITIGATED WETLAND IMPACTS MUST BE MITIGATED
FEIS Appendix B Section 1 .5.4
"Mitigation activities are intended to fully mitigate an affected resource, and in many
cases, enhance environmental resources and ecological functions. "
FEIS Section 4.9.4.3 .5
"Alternative 2M would slightly lower the composite functional capacity index score for
all riverine surface water and ground water wetlands within 100 feet of the river and
most of the groundwater wetlands greater than 100 feet from the river. "
FEIS Section 4.9.2.3
"The largest potential effect on functions is predicted to be to riverine surface water
supported wetlands and groundwater wetlands within 100 feet of the river banks. The
NISP action alternatives could change the functions of these wetlands by altering river
stage, inundation, and/or water quality. Effects on riverine ground water wetlands
greater than 100 feet from the river banks are also anticipated due to changes in
inundation and vegetation structures and complexity. "
FEIS Section 4.9.8.3
"Along the Poudre River, wetland functions would decrease for riverine surface water
and riverine ground water wetlands. The greatest reductions in composite functional
capacity index score are for Alternatives 2 and 3 at Martinez Park. "
Comment: In the FEIS , impacts to Poudre River wetland functions are described, with the
severity of impacts varying by location. For example, as noted above, the FEIS states that nearly
all wetlands within 100 feet of the Poudre River will be impacted. No compensatory mitigation
for these unavoidable functional impacts is provided in the Conceptual Mitigation Plan, which is
required by the CWA. See 40 C . F .R. § 230 . 91 (a) (purpose of mitigation is to "offset
unavoidable impacts to waters of the United States"); id. § 230 . 11 (h) (requiring evaluation and
mitigation of "secondary effects" on aquatic ecosystem resulting from project) .
Table 1 of the Poudre River Wetland and Riparian Mapping technical report, dated February 1 ,
2018 (with excerpts below), summarizes habitats along the Poudre River that appear to be
wetlands and which would subject to functional losses .
Wetland Type Acres
Riparian Herbaceous - Cattails/Sedges/Rushes 418 . 8
Riparian Herbaceous-Sedges/Rushes/Mesic 303 . 5
Grasses
Riparian Shrub-Willow 216A
Total acreage subject to impact 938.7
As summarized above, approximately 938 . 7 acres of probable wetland habitat within 100 feet of
the Poudre River would be impacted.
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Nearly all these wetlands will be subjected to functional impacts . Fort Collins and its properties
along the Poudre River will be adversely affected by NISP and the lack of compensatory
mitigation for the wetland impacts noted above. Although the predicted impacts will fall short of
outright habitat destruction, Corps regulations do not distinguish between partial and total
functional loss in setting mitigation requirements . See 40 C .F .R. § 230 . 93 (a)( 1 ) (stating
"fundamental objective of compensatory mitigation is to offset environmental losses resulting
from unavoidable impacts to waters of the United States") . Mitigation must compensate for all
"aquatic resource functions that will be lost" as result of the project. Id. ; see also id. § 230 . 92
(defining "impact" as any "adverse effect," and not a complete loss of aquatic ecosystem
functions) .
Recommendations . Any approval of the Project must include compensatory mitigation for
Poudre River wetland functional losses as required by Corps regulations as part of offsetting
losses to aquatic resource functions . Id. § 230. 93 (a)( 1 ) . Mitigation of Poudre River wetland
functional losses must be sufficient to achieve the expressed goals of the Conceptual Mitigation
Plan. Id. § 230 . 94(c) (setting forth criteria for mitigation plan) . Compensatory mitigation should
be required to offset the incremental functional impairment of these wetlands . Id. Such
compensatory mitigation should offset temporal and spatial impacts and other risks, as well as
employ a watershed approach in planning. Id. § 230 . 93 (m) (requiring to the extent appropriate
"additional compensatory mitigation to offset temporal losses of aquatic functions that will result
from the permitted activity. ") .
4.3 UNMITIGATED IMPACTS TO STREAM FUNCTIONS MUST BE MITIGATED
FEIS Section 4.5.3.3
"For the four river segments that were analyzed (A, B, C, and F), the predicted
reductions in maximum river stage would range from about 1. 8 feet to 3. 0 feet. "
FEIS Section 4.4.7.3
"The occurrence of flushing flows would be reduced by a total of 1 to 2 years (out of 26
years). The average duration of flushing flows would be reduced by up to 4. 9 days/year
and the median duration by up to 12 days/year. "
FEIS Section 4.4.7.3
"Sediment transport potential is predicted to be reduced throughout the river. The
capability of the river to move bed material is predicted to be reduced between 5 % and
30% upstream of I-25. "
FEIS Section 4 . 3 . 6 .2 . 1
"Adverse effects generally occur in May August and are more pronounced below the
extent of conveyance refinement flows. "
FEIS Section 4. 12.3.3 . 1
"Alternative 2Mwould have an overall minor adverse effect on aquatic. 91
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Fish and Wildlife Mitigation and Enhancement Plan
"The mitigation costs are exclusive of costs for other mitigation requirements that will be
developed for and required by the Final EIS, 401 certification, and 404 permit. "
Comment: According to the Omaha District of the Corps (Corps 2018), stream functions are
impacted when adverse changes to hydrology, hydraulics, geomorphology, physicochemistry
(water quality), and/or biota occur. The FEIS predicts such impacts as noted in the example
statements listed above.
The compensatory mitigation included in the 2017 Fish and Wildlife Mitigation and
Enhancement Plan is exclusive of the requirements of other applicable legal requirements,
including Section 404 of the Clean Water Act. Table 1 of the Compensatory Mitigation Plan
indicates that no compensatory mitigation for stream functional losses is being proposed in
response to Clean Water Act Requirements . Adequate compensatory mitigation of stream
functional losses is critical under the Corps ' regulations, which expressly recognize streams as
"difficult-to-replace resources ." 40 C .F .R. § 230 . 93 (e)(3 ) . Compensating for lost stream
functions has been a long-standing Corps practice under the CWA. See e.g. Regulatory
Guidance Letter 02-2 (December 24, 2002) (superseded by 40 C .F.R. § 230 . 91 ) ("Districts
should require compensatory mitigation projects for streams to replace stream functions where
sufficient functional assessment is feasible. ") .
The 2008 Final Rule on Compensatory Mitigation for Losses of Aquatic Resources (40 C .F.R. §
230 et seq. ) ("Mitigation Rule") states that compensatory mitigation "involves actions taken to
offset unavoidable adverse impacts to wetlands, streams and other aquatic resources. " 73 Fed.
Reg. 19, 594, 19,594 (April 10, 2008) (emphasis added) . Under the Mitigation Rule, stream
mitigation plans must contain the same 12 fundamental standards as those applied to wetland
mitigation—including adequate baseline information and ecological performance standards . 73
Fed. Reg. at 19, 597 , The Mitigation Rule requires replacement of stream functions lost as a
result of a federally-permitted action, to the degree practicable. 40 C .F . R. § 230 . 93 (e)( 1 )—(3 )
(discussing stream mitigation) ; id. § 230. 94(c)(7) (setting forth criteria for work plans regarding
"stream compensatory mitigation projects").
The 2017 Fish and Wildlife Mitigation and Enhancement Plan includes mitigation for stream-
related impacts to fish and wildlife as described in the Fish and Wildlife Mitigation and
Enhancement Plan. However, the Poudre River stream functions that would be adversely
affected by NISP go beyond fish and wildlife impacts, and the 2017 Fish and Wildlife Mitigation
and Enhancement Plan does not offset all the predicted impacts to Poudre River stream
functions.
Under the Mitigation Rule, the Conceptual Mitigation Plan must adequately describe the
"resource type(s) and amount(s) that will be provided," "the method of compensation," and "the
manner in which the resource functions of the compensatory mitigation project will address the
needs of the watershed," which include stream functions . 40 C .F .R. § 230 . 94(c)(2) . Thus, the
Conceptual Mitigation Plan must adequately offset the adverse impacts to stream functions .
Compensatory mitigation for unavoidable stream functional impacts in response to the
requirements of the Mitigation Rule was not included in the Conceptual Mitigation Plan,
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therefore the Conceptual Mitigation Plan does not comply with the Mitigation Rule nor is it
consistent with the stated goals of the Conceptual Mitigation Plan as discussed above.
Recommendation : Any approval of the Project must provide adequate compensatory mitigation
for losses of stream function in and along the Poudre River, including offsets for any predicted
temporal and spatial impacts or other risks, and should consider both in-stream and near-stream
components of habitats . Systemic impacts should be mitigated with systemic solutions . Three
key elements to a systemic solutions are recommended :
1 . A three-day peak flow bypass in all years .
2 . A recommended approach for minimization of the descending limb is to model historic
behavior of the descending limb (i . e. the rate of change as evaluated by year type) and
calculate 30% of the historic averages. This new rate, or slope, of the descending limb,
would become the flow management goal. The 30% value is proposed as reasonable and
practicable value that allows for NISP diversions but retains some characteristics of the
natural features of the descending limb .
3 . Establish an integrated for flow-physical management plan. Physical manipulations of
vegetation or floodplain habitat in advance of the May/June rise in years when flows,
combined with NISP flow mitigation plans, are anticipated to be sufficient to support
ecological functions . In other words, in an average or above average year, physical
manipulation could jump start the processes of scouring encroached vegetation or
preparing bare sites in the floodplain for cottonwood establishment could greatly enhance
the probability of success these stream functions will occur. Numerous recent restoration
efforts in fort Collins clearly shown this approach can be highly successful for supporting
cottonwood renewal (as was documented in the City' s comments to the FEIS .)
4A UNMITIGATED RISKS To AQUATIC HABITATS MUST BE MITIGATED
FEIS Section 4.4.3. 1 .2
Section 3. 4 of the Operations Report provides a qualitative description of how NISP
diversions may be operated immediately following a peak flow operational period. The
Peak Flow Operations Plan does not specific what other flow range would be reduced in
order to maintain firm yield. Without additional detail, the overall impact of
Alternative 2M with Peak Flow Operations Program on overall stream morphology and
sediment transport is unknown "
Comment: Because impacts of the Project are uncertain, there is significant risk to Fort Collins
that impacts to stream and wetland resources will be greater than predicted. Uncertainties
described in the FEIS include those regarding how stream flow alterations might affect the in-
stream processes that drive aquatic habitat functioning (such as sediment transport), and those
regarding how alterations in river flows will affect riparian habitats that support stream
functioning. These uncertainties should be addressed through additional mitigation set forth in
the Mitigation Plan, See 73 Fed. Reg. 19,594, 19,613 (April 10, 2008) (affording the Corps
broad discretion in determining the amount of mitigation "sufficient to replace lost aquatic
resource functions") ,
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City of Fort Collins NISP FEIS Comments
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Fort Collins acknowledges that predictive modeling always includes inherent uncertainty and
appreciates the discussion of those uncertainties included in the FEIS . Fort Collins maintains
that the uncertainties expressed in the FEIS analyses and confirmed in Fort Collins own analyses
constitute real risks, many of which Fort Collins will ultimately bear. Furthermore, because of
extensive concerns previously expressed by Fort Collins regarding the adequacy and validity of
the science underlying FEIS conclusions, Fort Collins contends this leads to exacerbated level of
uncertainty and risk to the accuracy of the predicted impacts . Project risks include under
estimation of impacts to stream and wetland resources in terms of severity, extent, and type of
impact, as well as, spatial, temporal and watershed-based impacts .
The most substantial risk to the Poudre River aquatic system in Alternative 2M is the unknown
effect of altering the descending limb of the Poudre River' s hydrograph, as stated above. The
risks of analytical uncertainty can be most effectively minimized by improving the flow
characteristics of the descending limb of the Poudre River hydrograph, generally by extending
the descending limb to make impacts more gradual.
Recommendation : A compensatory mitigation plan for unavoidable impacts to aquatic
resources, including both stream and wetland habitats, should be developed and that plan should
include measures to offset the risks of the predictive uncertainties identified and acknowledged
in the FEIS .
4.5 COMPARISONS TO A SPECULATIVE FUTURE CONDITIONS OF A DEGRADED POUDRE
RIVER ECOSYSTEM MUST NOT BE MADE
FEIS Section 4. 18.3.3
Flow reductions along the Poudre for all segments would be a negligible effect. Changes
in Poudre River flows are not expected to have an adverse effect on riparian vegetation
except to contribute to the trajectory of vegetation changes already occurring. Changes
would be gradual over time . . . .
FEIS Section 4.9.4.3
The trajectory previously described for the Poudre riparian resources is predicted to
continue with or without the NISP alternatives. Changes in flows associated with
Alternative 2Mwould accelerate and/or reinforce the trajectory but are unlikely to affect
existing stands of trees.
FEIS Section 4.9.4.3.4
The current trajectory for the plant communities bordering the Poudre River involves less
inundation.
Comment: Throughout the FEIS , the severity of predicted Project impacts to Poudre River
stream and wetland habitats are cast in the light of an assumed on-going downward trajectory of
habitat conditions . Although the FEIS suggests that this downward trajectory is well established,
Fort Collins contends that it is not.
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Poudre River stream, wetland, and riparian functioning will be harmed by all NISP alternatives,
as noted above. That harm includes the acceleration of the assumed downward trajectory in
degradation because that constitutes a temporal impact. In determining compensatory mitigation
requirements under Section 404 of the Clean Water Act for unavoidable impacts to aquatic
resources, solid benchmarks must be established. The Conceptual Mitigation Plan must include
"baseline information" regarding the ecological characteristics of the aquatic ecosystem,
including streams. 40 C .F .R. § 230 . 94(c)(5). A benchmark for pre-NISP functional condition of
wetlands is provided in the FEIS and Poudre River Wetland and Riparian Vegetation Mapping
technical report, dated February 1 , 2018 . No such assessment is provided for stream functional
condition.
Fort Collins understands that compensatory mitigation for Poudre River wetland and stream
functional impacts must be included in the NISP Conceptual Mitigation Plan. Moreover, the
nature and amount of compensatory mitigation should be based on the conditions characterized
at the time of the FEIS and not on a speculative future resource condition at an undetermined
time in the future. The Conceptual Mitigation Plan ' s "baseline information" should provide a
"description of the ecological characteristics" of impacted sites, including "historic and existing
conditions ." Id. (emphasis added) . Use of a debatable future condition as a benchmark to
determine compensatory mitigation requirements for impacts to aquatic resources does not
accurately reflect the existing conditions of the Poudre River stream and wetland habitats and
does not ensure impacts to existing resources are adequately offset under the Mitigation Rule.
See 40 C .F .R. § 230. 93 (a)( 1 ) (mitigation shall compensate for the "aquatic resource functions
that will be lost as a result of the permitted activity.") .
Recommendation : All compensatory mitigation for Poudre River aquatic resource impacts
must be based on existing habitat conditions as documented in the FEIS .
4.6 MITIGATION SHOULD OCCUR DURING THE INITIAL FILL PERIOD
Fish and Wildlife Mitigation and Enhancement Plan Section 5.2.2.4
" . . . diversions cannot be made through the Poudre River intake if there is insufficient
demand from Participants . . .
Fish and Wildlife Mitigation and Enhancement Plan, Section 5.2.2.6
"The operations described for this program would apply to diversions filling storage
space in Glade Reservoir that has already once been filled and is no longer under any
type of fill restrictions . . . during this interim initial fill period, filling of storage space that
remains underfill restrictions will be consistent with Tier 3 conditions. A bypass could be
considered as part of the Adaptive Management Program. "
Comment: Fort Collins is concerned about the lack of mitigation during the initial fill period.
Both the base flow conveyance refinement and the Peak Flow Operation Program would not
begin during this period, which according to the FEIS , Section 4 . 3 .2 .2 . 1 , could be up to 10
years. If lower than average water years occur during the initial filling period, the Poudre River
may undergo changes that are difficult to reverse. The Poudre River could see a transition to an
EXHIBIT A
City of Fort Collins NISP FEIS Comments
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alternate state (such as a smaller channel and embedded riverbed) that would limit opportunities
to optimize river health through future management.
Recommendation : Northern should be required to mitigate the impacts during the initial fill
period , and to not wait until the Project has been operated for nearly 10 years .
[Remainder of Page Left Blank Intentionally]
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SECTION 5 : RECREATION-RELATED COMMENTS
Over decades, Fort Collins has spent tens of millions of dollars acquiring and improving land
along the Poudre River, building recreation amenities on those lands , and restoration natural
habitat. (See the City of Fort Collins Natural Areas Master Plan and Cache la Poudre River
Natural Areas Management Plan Update) . Fort Collins owns three parks on the River and over
1 , 800 acres of natural areas . In 2014, City Council adopted a Downtown Poudre River Master
Plan that describes a vision for continuing to improve the most heavily visited reach of the River
from Shields Street to Mulberry. A regional trail runs the length of the Poudre from Laporte to
nearly 1-25 .
5. 1 IMPACTS TO BOATING AND TUBING ARE UNDERESTIMATED
FEIS Section 4. 16.3.3 .2
"Segment B is popular for boating (tubing, canoeing, and kayaking) and is the location
of a proposed whitewater park. Compared with Current Conditions hydrology,
Alternative 2Mwould increase the number of days over the boating season (May through
September) suitable for tubing and have no net effect on the number of days suitable for
kayaking. The number of days suitable for freestyle kayaking would decrease by 8 days,
with most of the decrease occurring in May (Table 4-113). Overall, Alternative 2M
would have minor beneficial effect on tubing opportunities, no effect on kayaking, and a
minor adverse impact of freestyle kayaking in Segment B. "
Comment: The FEIS underestimates the reduction of tubing days, and possibly of boating days
due to an assumption that tubing can occur at flows as low as 50 cfs . This is based on the
proposed wave design of the Fort Collins whitewater park. However, the wave design is
intended to concentrate flows to make it possible to tube at 50 cfs .
For the most popular tubing reach of the Poudre River, from Shields Street to Lee Martinez Park,
it is not possible to tube at 50 cfs. Based on the accumulated experience of Fort Collins Staff, a
more accurate minimum flow rate for tubing would be at least 75 cfs . A more enjoyable flow
that would make it possible to tube the entire reach without walking would require
approximately 150 cfs .
Recommendation : The mitigation Northern is required to offset boating impacts should take
into account the above analysis and Northern should be required to mitigate these impacts .
[Remainder of Page Left Blank Intentionally]
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SECTION 6 : SOCIOECONOMIC-RELATED COMMENTS
6. 1 THE FEIS FAILS TO INCLUDE ANY ANALYSIS OF PROPERTY VALUE DIMINUTION
FEIS Section 4.20.3.2.2
"In sum, Alternative 2M may have a minor adverse effect on future flood risk and flood
damages under a 100 yer flood event downstream of I-25 and a minor benefit on future
flood risk and flood damages under a 25 year flood event. "
Comment: The FEIS property value analysis focuses exclusively on flood risks ; no analysis has
been provided regarding the diminution of property values near the Poudre River and within Fort
Collins ' municipal limits should reduced river flows adversely impact the riparian forest. Recent
private sector investment adjacent the Poudre River, such as the $200 million Woodward
Campus development, show the area ' s present desirability given the Poudre River' s value as a
natural amenity.
Recommendation : Northern should be required to mitigate these impacts as described herein.
6 . 2 SOCIOECONOMIC IMPACT ANALYSIS IS INACCURATELY BASED ON PAST DATA
FEIS Section 4 .20.3.2.4
"there is no direct way to estimate the effect (f any) of changes in peak flows in the
Poudre River on business attraction or retention in Fort Collins ", and that "Based on
analysis of sales tax data for the City of Fort Collins during the spring and summer of
2012, a very dry year with unusually low flows in the Poudre River, there is no evidence
of a systemic relationship between flow levels in the Poudre River and the overall Fort
Collins economic conditions. "
Comment: These statements are based on past conditions and not the projected development
strategies described in adopted community plans . Recent multimillion dollar investment of
public and private sector funds has been made to properties proximal to the Poudre River
Corridor and many more are expected in the reasonably foreseeable future. This overall vision
and strategy to develop employment, housing, lodging and service uses within the area is
described in the recently adopted Fort Collins Downtown Plan (2017), and the North College and
East Mulberry Corridor Plans . Most of the reasonably foreseeable uses described in the plans are
not in the retail category and would, therefore, not be measured through sales tax data. Success
of the future community vision expressed in these plans are predicated on a robust and healthy
Poudre River ecosystem, with connections and access being made between the Downtown, the
Downtown River Corridor, the North College Corridor and the East Mulberry Corridor. The
economic impact to recent and projected public and private sector investments proximal to the
Poudre River Corridor has not been described.
Recommendation : Northern should be required to mitigate these impacts as described herein.
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EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 44 of 51
SECTION 7 : AIR QUALITY-RELATED COMMENTS
7. 1 NORTHERN SHOULD BE REQUIRED TO MITIGATE AIR QUALITY IMPACTS
FDEIS Section 4. 14
"The CDPHE 's Air Pollution Control Division determined that NISP conforms based on
the population analysis and that the project emissions are within the SIP emissions
budgets and consistent with the reasonable further progress demonstration in the SIP. "
FDEIS Section 4. 14
"Northern Water would implement fugitive dust controls as a result of CDPHE 's
construction permitting and fugitive dust control regulations. "
Comment: Regional impacts on ozone are the most important air quality impact for Fort Collins .
As stated in the FEIS , there will be demonstrable impacts to NOx and VOC, which contribute to
the formation of ozone. Major sources expected to contribute to these emissions upwind of Fort
Collins include temporary emissions from construction activities (up to 15 years), and ongoing
operations , including recreational boat traffic (small, high emitting 2-stroke engines) and
recreational vehicle traffic to/from reservoir. The FEIS states all projects demonstrate general
conformity with the 2016 Moderate Area SIP .
Particle and dust emissions will also be expected during construction. Dust is expected to be
controlled per CDPHE rules and regulations . Fort Collins has also recently adopted a dust
control ordinance that is more stringent than CDPHE regulations .
Recommendation : In addition to CDPHE requirements, it is requested that dust control
strategies applied are also consistent with Fort Collins ' requirements (such as limited speeds,
limited stock pile heights, and high wind work restrictions) as described at
(www. fcjzov. com/dust) .
To measure impacts to dust or particulate matter (PM2 . 5 and PM10) , ozone and ozone precursors
(NOx and VOC), it is recommended that an air quality monitoring station be installed at the
mouth of the canyon, near the communities of Bellvue or LaPorte. It is requested that
monitoring occur before, during and after construction, to demonstrate impacts on emissions in
these communities, and transported emissions to Fort Collins .
Per post-construction operation, it is recommended that the size of the boats be limited, with no
allowances for 2-stroke engines that both have relatively high air quality emission and leak raw
gasoline (which could also impact water quality) .
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EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 45 of 51
SECTION 8 : WILDLIFE-RELATED COMMENTS
8. 1 IMPACTS TO WILDLIFE FROM A SLOW CHANGE IN RIPARIAN HABITATS MUST BE
MITIGATED
SDEIS Section 4. 10.3
"A predicted shift in species composition favoring plant species adapted to greater
fluctuations in ground water levels could result in slight habitat changes in Segment B for
the common garter snake, northern leopard frog, smoky-eyed brown butterfly, two-
spotted skipper and other wildlife that may use these habitats. The predicted changes in
vegetation would occur slowly over a long period of time and would likely be negligible
and imperceptible given the dynamics of riparian areas. Wildlife using these habitats
typically use a wide range of aquatic, wetlands, and riparian habitats and would likely
adapt to the new habitat conditions that currently occur within the riparian areas of the
rivers . "
Comment: The assumption that a slow change in riparian habitats would be negligible and
imperceptible and that wildlife would likely adapt to new habitat conditions is repeated
throughout the FEIS in Sections 4 . 10 and 4. 11 . A loss of wetland and riparian habitat will take
place due to a reduction in high flows . See 40 C .F .R. § 230. 32(b) (citing loss of habitat due to
change in water flows as a factor considered in evaluating impacts to aquatic ecosystems). This
loss of habitat is a real and cumulative change that must be considered in assessing the adequacy
of mitigation regardless of the time needed for this change to occur or the rate of change. See id.
§ 230 . 75 (setting forth minimization measures to address adverse effects on wildlife); see also §
230 . 93 (d) (listing habitat status and trends as factors in determining whether a compensatory
mitigation site is "ecologically suitable") . The reduction in habitat is significant and will affect
the species mentioned above, along with many other wildlife species .
Riparian habitats are very rare throughout Colorado (less than 3 % land cover) but have, "the
highest species richness of all major ecosystem types in Colorado' (Mammals of Colorado,
Second Edition 2011 ) and 80% of resident bird species depend on them (Colorado Partners in
Flight, 2000) .
The assertion that wildlife will adapt to the new habitat conditions is also incorrect. Many
species require specific habitats and will not adapt to changes in relatively short time intervals .
Lower river flows will lead to an overall reduction of riparian habitats, which will either lead to a
reduction of wildlife species richness and abundance or a change in species composition along
the river, regardless of temporal scale or rate of change.
The Natural Areas Department has invested considerable financial resources into improving
riparian wildlife habitat and ecosystem function through the implementation of several riparian
and wetland restoration projects along the Poudre River. Additional restoration efforts are
planned through 2025 and beyond. Projects to date have lowered river banks allowing for an
increased frequency for overbank flows to reach the floodplain and restore important
components of ecosystem function such as natural cottonwood regeneration and a more
structurally diverse riparian habitat.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 46 of 51
Although these projects are designed for a variety of river flows, lower average river flows
resulting from NISP represent a diminishing return on wildlife habitat value. Importantly, with
fewer overbanking high flows, important ecosystem functions such as cottonwood regeneration
and varied riparian habitat structure will be negatively affected.
Recommendation : Northern should be required to monitor and quantify long and short-term
reductions in habitat and develop actions to restore or replace as impacts are identified, and to
mitigate such impacts .
8.2 IMPACTS TO FISH SHOULD BE MITIGATED
Aquatic Biological Resources Technical Report Section 2.4.2. 1
"There are no standard approaches and each project developed approaches appropriate
for the specific conditions of the project. "
Comment: The data interpretation for the Habitat Time Series analysis was non-standard and
the quote above appears to be the justification for this choice. The Habitat Time Series is a
fundamental tool for quantifying effects on aquatic habitats resulting from changes to the flow
regime. While some practitioners have deviated from the standard protocols, the developers of
the protocol were very specific as to how this analysis should be done (Bovee et al. , 1998.3).
The approach utilized by GEI was borrowed from the science of hydrology, whereby a synthetic
hydrograph representing a particular type of water year could be represented. This may work in
hydrology; a wet water year tends to produce large high flows and substantial low flows and dry
water years have smaller runoff events and lower base flows . .
Habitat time series do not work in this way because habitat limitations occur at both ends of the
hydrologic spectrum. The approach utilized by GEI in their habitat time series analysis is likely
to overestimate benefits of Alternative 2M and underestimate the negative effects. This is
because the most biologically relevant statistics produced in the FEIS are the average 20th
percentile values from the time series. This metric approximates biologically relevant limiting
habitat events, but it ignores the events most likely to constrain populations, inhibit recruitment,
or alter species compositions . A 20th percentile habitat time series can easily consist of some of
the low habitat events caused by high flows and some by low flows . This makes interpretation
of cause and effect very difficult, and in turn makes formulation of good mitigation alternatives
nearly impossible.
Recommendation : Maintaining healthy fish populations is central to managing for a healthy
river ecosystem and thus Fort Collins expects it will also be a priority for NISP mitigation and
adaptive management. Because the approach used by GEI may underestimate negative impacts,
3 Bovee, K. D. , B .L. Lamb, J.M. Bartholow, C.B . Stalnaker, J. Taylor, and J. Henriksen. 1998 . Stream habitat
analysis using the Instream Flow Incremental Methodology. U. S. Geological Survey, Biological Resources Division
Information and Technology Report USGSBRD- 1998-0004. viii + 131 pp.
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 47 of 51
Fort Collins recommends all future fisheries objectives in adaptive management are established
based on the standard protocol outlined in Bovee et al. , ( 1997), or deviations from the standard
protocol reported in habitat time series or fishery peer reviewed literature standard for
interpretation of the FEIS data.
Second, while high flows are common habitat limiting events for small-bodied fish, high flows
are also absolutely necessary to maintain the structural components of fish habitat, including
channel dimensions, width to depth ratios, riffle-pool periodicity, meander wavelength, substrate
composition, deposits of large woody debris, and vegetative encroachment. Therefore, the
recommendations under geomorphology are a priority for the fish communities as well.
Third, impairments to water quality, in particular temperature, is directly threatening to fish. All
efforts to ensure good water quality with NISP, including the recommendations set forth in this
document, are a priority for fish as well.
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EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 48 of 51
SECTION 9 : ADAPTIVE MANAGEMENT COMMENTS
9. 1 THE ADAPTIVE MANAGEMENT PLAN SHOULD BE REVISED TO MEET THE GOALS OF
MITIGATION AND ENHANCEMENT
FEIS : Appendix B, Conceptual Mitigation Plan, 2.8 Adaptive Management
Comment: Fort Collins appreciates the inclusion of the concept of adaptive management in
NISP Conceptual Mitigation Plan. As Fort Collins understands it, the purpose of adaptive
management is to identify and adaptively respond to unpredicted impacts . As described in the
above comments, Fort Collins is concerned that the impacts of Alternative 2M may have been
underestimated, which will result in insufficient mitigation. Therefore, an effective adaptive
management program is a Fort Collins priority to ensure that Fort Collins does not incur undue
risk, cost, and burden because of NISP . Fort Collins agrees with the description provided of
adaptive management in the Conceptual Mitigation Plan. However, Fort Collins is concerned
that certain omissions will lead to an ineffective adaptive management program and presents the
following recommendations to remedy this concern.
Recommendations :
Performance standards in the adaptive management program should be based on FEIS -predicted
impacts, a modified to factor in uncertainty as described herein. For example, if changes to
channel morphology are predicted as minor in the FEIS , then the adaptive management objective
should be maintain today' s conditions with additional minor changes. Any observed changes
beyond minor, should trigger an actionable response. The objectives and thresholds for
actionable response should be clearly defined in enforceable legal documents .
For adaptive management to be successful, clear structures must be established, including those
regarding what entities are participating and their role(s) , funding and spending mechanisms, and
enforcement/response.
The City recommends that the adaptive management program be required for no less than 50
years from full operation of the Project, due to the fact that NISP will operate in perpetuity.
As discussed above, Fort Collins ' River Health Assessment Framework would be useful in
providing the adaptive management program participants with a holistic picture of river
conditions and elucidating issues and opportunities for specific mitigation projects . Quantitative
measures can be added within the existing River Health Assessment Framework for NISP .
Changes to physical parameters can be most directly attributed to NISP and are recommended as
the primary measures for this program. Two examples of physical performance standards could
be measured annually and directly attributable to changes from NISP are suggested:
• Establish performance standards around the function of flushing flows . For example,
monitor sediment transport and physical embeddedness prior to NISP construction to
be able to tie these parameters and behavior specific to the Poudre to the historical
flow record. This relationship can then be applied to changes observed with NISP .
EXHIBIT A
City of Fort Collins NISP FEIS Comments
Dated October 4, 2018
Page 49 of 51
• Establish performance standards related to the bio-geomorphic feedback loop that
may change in the Fort Collins reaches with an annual survey using permanent cross
sections to observe possible aggradation and vegetation encroachment.
With clear objectives, structures, monitoring programs, and performance standards, determining
the response mechanism in advance is the final step towards ensuring an effective adaptive
management program. Systemic impacts are most effectively remedied with systemic efforts .
Therefore, Fort Collins recommends flow (flow releases or bypasses) are provided as the first
response mechanism.
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EXHIBIT A
APPENDIX A
(City of Fort Collins ' Comments on the Final Environmental Impact Statement for the
Northern Integrated Supply Project, Dated: October 4, 2018)
City of Fort Collins Staff
Cassie Archuleta, Environmental Program Manager, Environmental Services
Dan Evans, Civil Engineer III, Utilities Engineering Division
Daylan Figgs, Environmental Program Manager, Natural Areas Department
Cameron Gloss, City Planning Manager, Community Development & Neighborhood Services
Jill Oropeza, Director, Water Quality Service Division
Eric Potyondy, Assistant City Attorney, City Attorney' s Office
Bonnie Pierce, Senior Science Specialist, Environmental Regulatory Affairs
Jennifer Roberts, Environmental Planner, Natural Areas Department
Ken Sampley, Civil Engineering Director, Water, Utilities Engineering Divisions
Jennifer Shanahan, Watershed Planner, Natural Areas Department
Lucinda Smith, Environmental Services Director, Environmental Services
John Stokes, Director, Natural Areas Department
Richard Thorpe, Lead Science Specialist, Utilities Water Quality Services Division
Carol Webb, Deputy Director, Utilities, Water Production Division
External Contributors
Daniel Baker, PhD PE, Assistant Professor, Geomorphologist, Dept of Civil & Environmental
Engineering Colorado State University.
Johannes Beeby, Senior Hydrologist, Otak Inc .
Brian Bledsoe, PhD PE, Professor, Geomorphologist, University of Georgia
Ken Bovee, retired hydrologist, USGS .
Brad Johnson, PhD, PWS , Principal Scientist, Johnson Environmental Consulting, LLC
Nate Hunt, Esq. , Kaplan Kirsch Rockwell
William Lewis, Professor and Director, CU Center for Limnology, Cooperative Institute for
Research in Environmental Sciences, CU Boulder
Lori Potter, Esq. , Kaplan Kirsch Rockwell
Jennifer Roberson, Data Analyst, CU Center for Limnology, Cooperative Institute for Research
in Environmental Sciences, CU Boulder
Jeremy Sueltenfuss, Ecology Research Scientist, Colorado State University
Travis Stroth, Water Resource Engineer, Otak, Inc.
Luke Swan, Senior Fluvial Geomorphologist, Inter-Fluve, Inc. , Applied fluvial geomorphology
EXHIBIT A
APPENDIX B
(City of Fort Collins ' Comments on the Final Environmental Impact Statement for the
Northern Integrated Supply Project, Dated: October 4, 2018)
[Cover Page]
EXHIBIT A
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Poudre River FEIS
NISP Re -Analysis
Submitted to : Prepared By :
City of Fort Collins Otak, Inc.
5777 Central Ave .
[August 16 , 2018] Boulder, CO 80301
Project No . 18436
i
Otak
EXHIBIT A
TABLE OF CONTENTS
Page
Section1 —Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Section2—EIS Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 . 1 Background on Flushing Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 . 1 . 1 Defining Flushing Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 . 1 . 2 How the Definition of Flushing Flows Affects the Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 . 1 . 3 Literature Review Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 . 1 . 4 Effective Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 . 2 Summary of EIS Reports Analyses and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 . 2 . 1 Aggradation and Vegetation Encroachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 . 2 . 2 Flushing Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2 . 2 . 3 Effective Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 . 3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Section 3—Methods and Results of Desktop - Based Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 . 1 Recalculation of Flushing Flows Results Using D50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 . 2 Aggradation and Vegetation Encroachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 . 2 . 1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 . 2 . 2 Historical Aerial Imagery Analysis for Vegetation Encroachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 . 3 Recalculation of the Effective Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Section 4—Methods and Results of Field - Based Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 . 1 2018 Runoff Field Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4 . 1 . 1 Tracer Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4 . 1 . 2 Pre- and Post- Runoff Vegetation Encroachment Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 . 1 . 3 Case Study for Vegetation Encroachment and Aggradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4 . 2 Embeddedness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Section5—Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5 . 1 Flushing Flows and Sediment Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5 . 1 . 1 EIS Reports Flushing Flows Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5 . 1 . 2 Recalculation of Flushing Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5 . 1 . 3 Tracer Rocks Field Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5 . 1 . 4 Recalculation of the Effective Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5 . 2 Aggradation and Vegetation Encroachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5 . 2 . 1 Field Studies for Vegetation Encroachment and Aggradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Section 6—Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Appendices
Appendix A—Long -Term Monitoring Study
Figures
Figure 1 —Timeline of EIS Reports and technical documents related to stream morphology and sediment
transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Figure 2— Excerpt of conclusions for channel contraction based on the preferred alternative 2M from Stream
Morphology and Sediment Transport ( FEIS , 2018 ) Effects Report pg . 44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 3— Excerpt of description for spells analysis for vegetation impacts from SDEIS (2013 ) pg . 5- 18 . . . . . . . 6
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Figure 4— Range of and average flushing flow results as presented in the SDEIS Technical Report (2013 )
andFFR (2017 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 5— Excerpt of flushing flows results using 2-64mm grain size range from FFR (2017) pg . 8 . . . . . . . . . . . . . . 11
Figure 6— Excerpt of final baseline flushing flow results (equivalent to current conditions Q2 flow) presented
inFFR (2017 ) pg . 19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 7— Excerpt of effective discharge , Qeff analysis results presented in SDEIS Technical Report (2013)
pg . 8-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 8— Excerpt summarizing a description of sediment transport processes associated with T*c ranges
following research from Milhous (2000 and 2003 ) who performed scour chain studies on the Poudre River.
Table from ERM (2014 ) p9 . 28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 9— Plot of Qeff analysis results ( peak is Qeff) using T = yDSf (friction slope) and Parker ( 1990 ) and
Wilcock and Kenworthy (2002 ) bedload sediment transport equations for reach FC1 from SDEIS Technical
Report (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 10— Plot of Qeff analysis results ( peak is Qeff) using T = yRSe ( Energy Slope) and Parker ( 1990 ) and
Wilcock and Kenworthy (2002 ) bedload sediment transport equations for reach FC1 from SDEIS Technical
Report (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 11 — One grouping of tracer rocks placed pre- runoff in a riffle within the bankfull channel . . . . . . . . . . . . . . . . . 21
Figure 12— Photo ( looking downstream ) of bar on river left just upstream of Overland Trail Bridge in May
2018 (above) and July 2018 ( below) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 13— Photo (looking upstream ) of bar on river right adjacent to North Shields Ponds Natural Area in
May 2018 (above ) and July 2018 ( below) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 14— Photo ( looking upstream ) of bar on river left adjacent to McMurry Natural Area in May 2018
(above) and July 2018 (below) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Figure 15— Photo ( looking upstream ) in 2018 of case study point bar on river right just upstream of Shields
St. Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Figure 16— Four-foot steel soil probe stuck approximately ( 15 ) in ground until hitting coarse layer near
outskirts of case study bar just upstream of Shields St. Bridge ( photo from 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 17— Four-foot steel soil probe stuck approximately (4' ) in ground until hitting coarse layer near center
of case study bar just upstream of Shields St. Bridge . Woody vegetation was approximately 8- 10' tall and
verydense ( photo from 2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure 18— Photo ( looking upstream ) in 2004 of case study point bar on river right looking from Shields St .
Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Figure 19— Photo (looking downstream ) in 2013 of case study point bar on river right looking at cross
section taken for High Park Fire study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Tables
Table 1 —Summary of Key Points and Changes in Flushing Flows between EIS Reports . The FEIS is based
onFFR (2017) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 2— Recalculated flushing flow results for range of T*c values using D50 and friction slope (T=yDSf) . . . 15
Table 3— Recalculated flushing flow results for range of T*c values using D50 and energy slope (T=yRSe ) . . 15
Table 4— Summary of results from historical aerial analysis for vegetation encroachment. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Table 5— Comparison of discharges at three gages for the date of the aerial analyzed for vegetation
encroachment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 6—Summary of recalculated effective discharge , Qeff using two methods of calculating shear stress . 19
Table 7—Summary of colors the tracer rocks were painted for each size class in study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Table 8—Summary of tracer rock cross sections locations and associated parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 9—Summary of tracer rock field study results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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Section 1 — Introduction
This report presents an evaluation of the Northern Integrated Supply Project ( NISP) Environmental
Impact Statement ( EIS) conducted in consideration of the City of Fort Collins policies regarding flood risk
reduction and health and resiliency improvement.
The City of Fort Collins is a national leader in flood management and has made substantial investments
in mitigation of flood hazards along the Cache la Poudre River ( Poudre River) corridor. Additionally, the
City has embraced the vision of a healthy and resilient Poudre River and City Council has set policy to
support health and resiliency improvements .
Section 2 of this report reviews aspects of the EIS documents pertinent to the determination of flushing
flows on the Poudre River and provides a discussion of key results presented in the EIS documents .
Section 3 presents methods and results of Desktop-Based Analyses , including shear stress and effective
discharge analyses using replicated models and data from the EIS documents and aerial photo analysis
on magnitude and distribution of vegetation encroachment near the City.
Section 4 presents methods and results of Field-Based Analyses , including field studies on sediment
mobilization in riffle features to support interpretation of hydraulic and sediment transport modeling . The
analyses also provide additional lines of evidence for use in conjunction with modeling to provide greater
insight into the mobility of the channel bed , how that mobility may be impacted by vegetation , what can be
expected moving forward , and for application for potential long-term monitoring opportunities .
Section 5 presents a discussion of results and recommendations .
Section 6 provides a report summary and conclusions .
Methods to estimate flushing flows have been developed in various contexts to meet ecological and/or
management objectives that range from targeting a particular gravel quality to maintaining an active
channel width . The determination of flushing flows in the Poudre River for the NISP EIS process has used
a shifting set of definitions and approaches that ultimately settled on a definition of flushing flows focused
on maintaining fish spawning habitat.
Engineering and geomorphic analysis methods used in the NISP EIS yield results that portray the Poudre
River as a relatively non- responsive river that will not be impacted by the projected flow extraction
associated with NISP , despite substantial reductions in sediment transport capacity and flows that inhibit
encroachment of trees into the channel ( DEIS 2008 , SDEIS 2013 , and FEIS 2018 ) .
Analyses and multiple lines of evidence presented in this report run counter to the FEIS conclusions and
indicate that the flow extraction resulting from NISP will result in increased rates of vegetation
encroachment, channel contraction , and an increase in flood risk to the City of Fort Collins .
To understand the flushing capability of the Poudre River, under the current hydrologic regime , relative to
results presented in the EIS documents , this report specifically:
1 . Examine the hydrologic, hydraulic and geomorphic analyses presented in the EIS to understand
the data , assumptions , and decisions made to arrive at the conclusions stated in those reports ;
2 . Use the EIS hydraulic model , the best available geomorphic data , and standard methods from
the scientific and engineering literature to calculate fundamental measures of sediment flushing
capacity (dimensionless shear stress and effective discharge) and compare those results to the
EIS reports , flow frequency estimates , and field observations of tracer particles ;
3 . Perform effective discharge analysis using site specific grain size distributions and sediment
transport models appropriate for those distributions ; and
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EXHIBIT A
4 . Use historical aerial photographs and field observations to examine bar formation .
From this analysis , three key conclusions emerge :
1 . The geomorphic analysis methods and interpretation of results have been variable and
inconsistent. The physical basis for the selected geomorphology methods and conclusions are
not supported by the best available science and data .
2 . The modeling methods and assumptions used in the EIS are inadequate to predict and evaluate
the impacts of NISP on flood risk . We believe the preferred alternative will increase sediment
deposition and woody vegetation establishment in the river channel , despite the proposed
mitigation plan . This will potentially increase flood levels and risks to private property and critical
infrastructure (e . g . , bridges ) along the river corridor.
3 . There are multiple lines of evidence from our analyses ( including historical and field evidence)
that suggest the proposed changes to river flows will reduce flood carrying capacity and
simultaneously degrade habitat. Ultimately, the City will be faced with increased costs and
maintenance requirements to sustain the current level of flood protection along the river corridor.
The City's ability to achieve its vision of a healthy and resilient river, will also be limited in
perpetuity, as the selected alternative and mitigation plan will substantially reduce the amount of
time that flows meet critical thresholds for preventing sediment build up and maintenance of
channel capacity.
Section 2—EIS Review
In the following sections , we review those aspects of the EIS documents pertinent to the determination of
flushing flows on the Poudre River. Specifically, we examine the chosen definition of flushing flows , the
determination of those flows , the effective discharge calculations , and the aggradation analysis
performed . A timeline of the EIS reports and technical documents related to stream morphology and
sediment transport is shown if Figure 1 for reference . Hereafter, the EIS reports regarding stream
morphology will be abbreviated as follows :
DEIS (2008) : Draft Environmental Impact Statement River Morphology Report, 2008
SDEIS Technical Report (2013) : Supplemental Draft Environmental Impact Statement Stream
Morphology Baseline Report Parts 1 and 2 , 2013
SDEIS Technical Report (2014) : Supplemental Draft Environmental Impact Statement Stream
Morphology Effects Report, 2014
FFR (2017) : Assessment of Flushing Flows Report, 2017
FEIS (2018) : Final Environmental Impact Statement Stream Morphology Effects Report, 2018
Figure 1 —Timeline of EIS Reports and technical documents related to stream morphology and sediment
transport.
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EXHIBIT A
2028
2008 2024 FDEIS:
DEIS: SDEIS: Stream
River Stream Morphology
Morphology Morphology Final Effects
Report 2010 2012 Effects Report 2016 Report
0 0 0 0 0 0 0 0 0 0 0
2009 2011 2013 2015 2017
SDEIS: SDEIS: SDEIS:
2D Hydraulic Stream Assessment
Modeling Morphology of Flushing
Report Baseline Report Flows Report
Part 1 and 2
2 . 1 Background on Flushing Flows
The flushing flows analyses performed for the EIS reports can have large implications for the diversion
management decisions that are agreed upon for NISP which could ultimately lead to negative impacts on
flood risk in the City of Fort Collins and river health/function . There were several analyses completed
regarding flushing flows in the EIS reports , but those analyses varied in intent and methods which
markedly affected the final results .
2 . 1 . 1 Defining Flushing Flows
Flushing flows have been defined for a wide range of ecological and/or management objectives ( Kondolf
& Wilcock , 1996 ) . Thus , the definition for each application needs to be explicitly defined , in terms of a
physical stream response . The definition of flushing used in the EIS process changed with the release of
the FFR (2017 ) ultimately settling on the ecological objective of maintaining trout spawning habitat by
flushing fine sediment from the top of a coarse armor layer of gravels and cobbles . This definition does
not include channel maintenance objectives , which are critical for reducing flood risk in the City and
cleaning/rejuvenating habitats below the surface of the river bed that are essential for aquatic insects (the
food base for trout and other fishes ) . The FEIS (2018 ) uses the flushing flow definitons and results
presented in the FFR (2017 ) .
While the FFR (2017 ) ecological objective is focused on maintaining spawning habitat, the underlying
assumptions do not provide the mechanism for achieving that goal . Specifically, flushing fine sediment off
the top of a coarse armor layer will not maintain the interstitial spaces necessary for egg incubation and
habitat for benthic macroinvertebrates (a key food source for trout and other fishes) .
2 . 1 . 2 How the Definition of Flushing Flows Affects the Analysis
The selected definition and targeted objectives of flushing flows have large impacts on the chosen
analysis and results . The FFR (2017 ) specifically considers spawning habitat for Brown Trout. This report
claims that only fine sediments that have deposited on top of the coarse bed material affect the fish . This
incorrect assumption highly affects sediment transport calculations because only transporting surficial
veneers of fine material require much less flow than transporting the coarser bed material , especially if
the bed is armored or embedded . When considering channel maintenance objectives , flushing flows are
required to release fines from the interstitial spaces among the coarse bed particles . This significantly
changes sediment transport calculations because , to release fines from the interstitial spaces , the coarse
bed material has to be sufficiently vibrated or fully mobilized . This can drastically increase the amount of
shear stress required to produce 'flushing flows . '
While there are no exact guidelines to define an all-encompassing flushing flow value , the definition must
be tied to the specific function (s ) to be maintained or restored by the flushing flow . The most recent
definition used in the EIS process stated that the objective of the flushing flows was specifically tied to fish
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EXHIBIT A
spawning habitat; however, we argue that the City requires channel maintenance flows to help mitigate
increases in flood risk . These channel maintenance flows have the added benefit of being most likely to
maintain and create both fish spawning and macroinvertebrate habitat. This would provide the most
benefit for river health and resiliency since macroinvertebrates are the main food supply for fishes , and it
is just as essential to maintain macroinvertebrate populations as it is to maintain fish populations .
2 . 1 . 3 Literature Review Summary
A literature review was conducted on previous Army Corp decisions involving water development projects
with flushing flow analyses . Only two such projects were found 1 ) The Windy Gap Firming Project and 2 )
The Moffat Collection System Project. Both projects relied on the same flushing flow analysis which
looked to quantify the minimum flow necessary for flushing . The analyses involved using the Parker
( 1990 ) bedload sediment transport equation to determine when sediment transport is initiated for flushing
flows . As opposed to the methods used in the NISP EIS reports , the Parker ( 1990 ) equation is more
appropriate and commonly used to model gravel/cobble bed rivers and more closely aligns with what is
considered the best available science . The Parker equation includes the effects of the entire grain size
distribution on sediment movement using a hiding function rather than examining a single particle as used
in the SDEIS Technical Report (2013) and FFR (2017 ) . This method captures a more realistic initiation of
bed material movement and therefore can produce a more encompassing estimate of flushing flows .
2 . 1 . 4 Effective Discharge
The effective discharge (Qeff) is defined as the discharge that moves the most sediment over a period of
years and is one approximation of the geomorphic concept of the `channel -forming ' discharge . This
concept is important because it relates to creating and maintaining the active channel dimensions and
capacity which directly correlates to many aspects of river health , function , and flood conveyance .
In the context of trying to understand the impacts of NISP , Qeff can give another line of evidence for
bracketing the range of flows performing the most work in transporting sediments and maintaining the
river channel and substrate . Calculating Qeff utilizes full sediment transport equations rather than a
simplified incipient motion analysis (dimensionless shear stress ) as in the flushing flows analysis . This
technique also incorporates the whole grain size distribution based on measured data from the Poudre
River in Fort Collins , utilizes hiding factors on the transport of sediment, and frequency of all flows in the
river segment.
2 . 2 Summary of EIS Reports Analyses and Results
2 . 2 . 1 Aggradation and Vegetation Encroachment
The DEIS (2008 ) , SDEIS Technical Reports (2013- 14 ) , and FEIS (2028) have several analyses focused
on calculating different aspects of sediment transport; however, the conclusions concerning aggradation
and vegetation encroachment near the City of Fort Collins seem to rely mostly on qualitative observations
and speculation . The discussion of river condition on the Poudre is generally split into " Upstream of I -25"
and " Downstream of I -25 , " although there is no apparent geomorphological basis for this distinction . As
opposed to other analyses in the EIS Reports , the general conclusion on aggradation and vegetation
encroachment is consistent across the reports : upstream of I -25 ( including the reach through the City of
Fort Collins ) will not be drastically impacted by aggradation and vegetation encroachment under NISP
operations because it is "supply limited . " However, we conclude that current conditions and available data
show little evidence of this response . Conversely, the EIS reports conclude that downstream of 1 -25 will
possibly be impacted since it is "transport limited" and shows signs of aggradation and vegetation
encroachment. More details of this opposing conclusions are found in the paragraphs below.
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The EIS reports describe the Poudre upstream of 1 -25 (from the mouth of Poudre Canyon to near
Timnath ) as a "supply-limited" reach . This is based on observations that " In general , the bed is armored
with cobbles and coarse gravels that only move rarely in response to high flow periods" (SDEIS Technical
Report, 2013 pg . 9-4 ) . Further, the EIS reports state that because the coarse material is rarely mobilized ,
the finer material underneath is rarely released ; thus , the river is thought to generally have a lack of
sediment supply moving downstream through the system (specifically upstream of 1 -25) . This is coupled
with observations of upstream of 1 -25 that , " Bars , islands and marginal deposits do form , but signs of
consistent, contiguous aggradation are not evident' (SDEIS Technical Report 2013 pg . 9-4 ) . The
observations that upstream of 1 -25 is transport limited and lacks signs of large scale aggradation
ultimately leads the EIS reports to the broad assertion that aggradation is not a current issue and will not
be under future NISP conditions .
In contrast to upstream of 1 -25 , the EIS reports state that the river downstream of 1 -25 has finer bed
material and is "transport limited " because , "The control on sediment transport shifts so that the
movement of sediment is limited more by the transport capacity of the river than by supply from external
sources" (SDEIS Technical Report 2013 pg . 9-4) . This is coupled with observations that the river
downstream of 1 -25 has signs of continuous aggradation and "bio-geomorphic feedback loops" occurring ;
therefore , there will be more of an impact in this location under NISP conditions .
The following excerpt is from the summary of conclusions table in the Stream Morphology and Sediment
Transport ( FEIS , 2018 ) Effects Report. This conclusion is based on a predicted reduction in sediment
transport capacity for the NISP preferred alternative conditions throughout the river corridor, and notably
larger reduction in capacity upstream of 1 -25 than compared to downstream . Despite the 40% reduction in
sediment transport capacity upstream , this report reasserts the conclusion that there will be more impacts
downstream because the upstream reach is "supply-limited . " We were unable to find quantitative
evidence to support this claim .
Figure 2— Excerpt of conclusions for channel contraction based on the preferred alternative 2M from
Stream Morphology and Sediment Transport ( FEIS , 2018 ) Effects Report pg . 44 .
Sediment transport potential is reduced by around 40%
across a broad range of flows but the effective discharge
remains unchanged at about 2 , 000 cfs . The effective
discharge suggests an ongoing trend of channel
contraction , but this is the same for current conditions
hydrology and Alternative 2M and channel contraction is
predicted to continue to be constrained by the limited
supply of material available for deposition .
The SDEIS Technical Report (2013 ) describes the connection of aggradation and vegetation
encroachment with the concept of a bio-geomorphic feedback loop . However, this discussion focuses on
the colonization of Reed Canary Grass and specifically on the Poudre River downstream of 1 -25 because
vegetation encroachment is not deemed prevalent upstream of I -25 . Reed Canary Grass is commonly
known as an invasive species in Colorado but is not an intrusive obstruction during flood flows because
they, " Bend and streamline in response to high flow" (SDEIS Technical Report 2013 pg . 9-5) . The
discussion on vegetation encroachment in the EIS Reports seems to focus on the impacts of vegetation
on the geomorphic response of the channel rather than discussing the potential increase to flood risk
caused by increased roughness and the trapping of sediment by prevalent woody species such as
willows .
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EXHIBIT A
Additionally, the SDEIS Technical Report (2013 ) describes an analysis performed to quantify the flows
when different plant communities are inundated but does not describe the purpose of the analysis or
discuss conclusions . The analysis is presumably only to support the " CTP Wetland and Riparian
Resources Baseline Report" and again does not appear to address the connection of vegetation
encroachment with flood risk .
Figure 3— Excerpt of description for spells analysis for vegetation impacts from SDEIS (2013 ) pg . 5- 18 .
5. 5. 3 Spells Analysis for Vegetation Impacts
A number of cross sections were surveyed by vegetation specialists within the detailed
habitat modeling sites as part of a baseline vegetation assessment for the EIS . The specialists
identified the key in -channel and floodplain vegetation communities within these sections . The
sections were incorporated into the hydraulic modeling so that it was possible to identify the flow
at which each vegetation community was inundated . These flows were then used as threshold
flows in a spells analysis to describe the pattern of occurrence of inundation of each vegetation
community .
Table 5 . 8 summarizes the threshold flows that were tested for this assessment . Further
details are given in Appendix D and are discussed in the CTP Wetland and Riparian Resources
Baseline Report for the NISP and HSWSPs EISs ( ERO , 2011 ) .
2 . 2 . 2 Flushing Flows
Note that the DEIS (2008 ) did not consider flushing flows , hence analyses regarding flushing flows were
exclusive to the SDEIS Technical Reports (2013- 14 ) and FFR (2017) . The FEIS (2018 ) uses the same
results from the analyses in the FFR (2017) so this discussion applies to the FEIS (2018) as well .
Inconsistent Methods and Analyses
There were several shifts in objectives and methodology used between these reports , and ultimately the
conclusions do not align with the results from the analyses performed in the SDEIS Technical Report
(2013) and FFR (2017) .
The primary factor that affected the results of the flushing flows analysis was a change in the definition of
flushing between the SDEIS Technical Report (2013) and the FFR (2017 ) . The definition used to define
flushing flows in the SDEIS Technical Report (2013) is , `disturbing coarse bed material sufficiently to
release fines from interstitial spaces . In the FFR (2017 ) , the definition was changed to specifically
examine surficial flushing for fish spawning habitat . This new definition requires the `surface cleaning of
riffles' which only involves mobilizing the fine material deposited on top of the coarse bed material to
provide `flushing . ' Using this definition requires much less channel bed shear stress and therefore less
flow ( lower flushing flows ) . The definition used in the SDEIS Technical Report (2013 ) is more closely
related to the needs of the City and better aligned with the City's broader stream health and flood safety
goals .
The FFR (2017 ) presented a new analysis that examined the potential movement of individual particles in
the `optimal sediment range for brown trout spawning habitat. ' This method examined a range of generic
grain size classes (2-64mm ) and did not consider location specific grain size distribution data from the
river. We were unable to find examples where this technique was supported in the scientific literature or
used at all in other reports . Furthermore , this method does not consider a hiding factor which we consider
to be a very prevalent effect on the Poudre River especially in riffle features . Small particles in
gravel/cobble bed streams tend to ` hide ' behind the coarser bed material making it harder for the particles
Poudre River FEIS Assessment 6
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EXHIBIT A
to be mobilized . Thus , calculating the movement of fine particles without accounting for this effect over-
estimates the probability of sediment mobility and thus reduces required flushing flow values .
Lastly, the final values chosen for flushing flows were altered again by the selection of " Baseline Flushing
Flow Values" that were ultimately chosen to examine the impacts of different NISP alternative hydrology's
on flushing flows . The " Baseline Flushing Flow Values" were stated to be selected based on feedback
from DNR, CPW , and EPA who agreed that a 1 . 5- to 2-year recurrence interval discharge (Q1 .5-Q2 ) would
"Optimize benefits for aquatic species in the study area . " This decision essentially nullified all the previous
results from their other analyses which showed large variability throughout the study reach , and bases
flushing solely on a theoretical function of flow associated with a particular recurrence interval rather than
on hydraulics and/or sediment transport, including the analyses performed for the SDEIS Technical
Report (2013) . The recurrence interval is a moving and arbitrary target in the Poudre River given the long
history and evolution of flow extraction , and again we are unaware of any peer-review and published
justification for the determination of a flushing flow value based on a particular recurrence interval
discharge . Without an in-depth understanding of how the investigated hydrologic regime can transport
sediment into and through the project reach , the results are irrelevant and arbitrary.
The flushing flows analyses increasingly used less data and more averaging through time leading to
decreasing variability in results . The SDEIS Technical Report (2013 ) which calculated flushing flows at
every cross section showed results ranging from < 10cfs to > 10 , 000cfs . The FFR (2017 ) which only
considered cross sections at selected riffles presented results ranging from < 10cfs to 6800cfs for the 2-
64mm grain size range . Lastly, the range was decreased again with the selection of the baseline flushing
flow values which ranged from 972 cfs-2406 cfs across the study reach , again , based on flow recurrence
interval alone .
Despite the changes in assumptions and analysis across the reports , a key general conclusion about the
impact of NISP on channel conditions reported in the SDEIS Technical Reports (2013- 14) and FFR
(2017) appears incontestable and has remained consistent: NISP will reduce the quantity of water in the
Poudre River and therefore lower sediment transport capacity and total stream power.
Figure 4— Range of and average flushing flow results as presented in the SDEIS Technical Report
(2013 ) and FFR (2017 ) .
10000
9000
8000
7000 Range of
Flushing
V) 6000 Flows
o Results
LL 5000
ao
Average
4000 Flushing
N
3000 Flow
Result
2000
1000
0
SDEIS : Using every cross FFR : Using riffle cross FFR : Using Q2 as Baseline
section and D50 sections and (2-64mm ) Flushing Flow values
Poudre River FEIS Assessment 7
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Table 1 —Summary of Key Points and Changes in Flushing Flows between EIS Reports . The FEIS is based on FFR (2017 ) .
Key Point or DEIS River Morphology SDEIS Baseline and Effects Flushing Flows Report (2017) Why is this important?
Change Report (2008) Reports (2013-14)
This report does not define or Definition : Definition : . Only removing fines from the top of riffle
calculate flushing flows . • Flushing needs to disturb • Flushing only needs to does not require the movement of the
However, the report does coarse bed material remove fines that are coarse bed material which is much
mention the need for flushing sufficiently to release resting on top of the easier to mobilize which effectively
flows in relation to channel fines from interstitial coarse armor layer reduces the required flushing flows .
maintenance and scouring spaces Benefits/Purpose : • All the reports show that it is harder to
vegetation in the Timnath Benefits/Purpose : • "The objective of the move the bigger grain sizes , specifically
Changed " Flushing through Greeley reaches . • This helps "strip algae flushing flows is to the D50 , under NISP, but this is not
Flows" Definition and benefit maintain spawning habitat reflected in their conclusions . If the D50
macroinvertebrate for fish " does not move, the flows are not likely to
habitat" Calculations : flush fines or scour plant seedlings from
Calculations : • Incipient motion calcs with the interstitial spaces or from hiding
• Incipient motion calcs T*c = 0. 047 referenced to locations
with T*c = 0 .02 2-64mm grain size • T*c = 0 . 047 is not commonly used for
referenced to D50 classes sand and fine gravel sized particles as in
the FFR (2017 )
This was not used in this report This was not used in this report "Baseline Flushing Flow values" . This decision essentially nullified all the
were selected based on feedback previous flushing flow analyses which
from DNR, CPW , and EPA to showed that the flushing flow values in
evaluate the impact of NISP Fort Collins and Timnath were very high
alternatives . They agreed that a for the 32-64mm grain size classes ,
Use of " Baseline Q, s-Qz flood flow would "Optimize
sizes most akin to the D50
benefits for aquatic species in the Qz is a commonly assumed proxy for Qeff
Flushing Flow orQbf but does not apply in disturbed ,
Values" study area ". urbanized systems . The assumption was
specifically developed for equilibrium
channels , of which the Poudre through
the project area is not.
• This method disregards all the previous
analyses and does not account for the
variability in the system
This report did not mention This report partitioned shear stress This report did not partition shear • Not partitioning shear stress results in
partitioning shear stress using a relationship that is stress the calculation of higher shear values ,
physically inappropriate for the thus greater flow competence and a
Partitioning Shear Poudre River (Ackers and White reduction of the flushing flows or
Stress 1973 ) discharge required to move the particles .
No explanation was given as to why the
shear was originally partitioned , then
subsequently not partitioned .
Poudre River FEIS Assessment 8
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Key Point or DEIS River Morphology SDEIS Baseline and Effects Flushing Flows Report (2017) Why is this important?
Change Report (2008) Reports (2013-14)
The most significant impacts This report gave broad This report had minimal to no . The conclusions from the SDEIS do not
are stated to be downstream conclusions and in summary conclusions . The results were match the results using the method that
of Fort Collins to Greeley, stated the river will probably not presented for each of the NISP was supported by the literature (Milhous ) ,
where sediment deposition change much , although the results alternatives comparisons but did not which appears to show a significant
and veg encroachment "would showed a reduction up to 50% in offer any conclusion to what that impact to flushing flows
be expected to be the flushing of fines and moving means or which options are best for • The flushing flows report changed the
Report Conclusions accelerated . " Overall , effects the bed material for most of the flushing flows . definition and analysis but not discuss
vs. Results are "expected to be less than NISP alternatives comparisons . how that compared to the previousanalysis or what it means for the Poudre
the morphologic changes River.
already occurring" even . We do not know if and/or how well the
though the results show alternatives meet the stated spawning
significant reduction in stream habitat objective or the City's
power. maintenance flow objective .
This analysis did not use this This analysis did not use this This analysis performed incipient . The technique does not appear to be
technique , but used a technique , but used a motion calculations for generic grain supported in the literature
representative D50 instead representative D50 instead with T*c size classes 2 ,4 , 8, 16 , 32, 64 mm and • This technique does not consider a hiding
with T*c = 0 .03 & 0 . 047 = 0 . 02 & 0 . 03 used a T*c = 0 . 047 function which is very prevalent from field
Calculations using observations by Otak and others
2-64mm Grain Size • This does not consider the grain sizes
Classes instead of actually present in the river or the spatial
D5o and T*c value relationships and longitudinal trends of
the grains present in the bed .
• T*c = 0 . 047 does not typically apply to
fine material such as 2-8mm and the
shifting of the selected T*c values renders
the results difficult to compare
Neither of these were Neither of these were mentioned in The D16 of the coarse armor layer . The D16 as related to flushing flows does
mentioned in this report this report samples and research by ( Raleigh not appear to be supported in the
et al 1984), who stated that the literature
Using D16 and optimum range of grains sizes for • The Fort Collins and Timnath reaches
( Raleigh et al 1984) Brown Trout spawning are 10- rarely mobilized 32-64mm in their
for Grain Size 70mm , were used to justify the analysis but this was disregarded with the
Selection selection of using 2-64mm grain use of the baseline flushing flow values
• Grain sizes were ultimately not used in
size classes for their analysis the comparison to the NISP alternatives ,
just the occurrence of the Q2 event
Poudre River FEIS Assessment 9
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Key Point or DEIS River Morphology SDEIS Baseline and Effects Flushing Flows Report (2017) Why is this important?
Change Report (2008) Reports (2013-14)
Averaging Flushing flows were not Results were calculated using Results were calculated at 53 . The technique in the flushing flows report
Technique and calculated for this report every cross section in the model defined riffle features then averaged did not recognize or discussion the
Variability for into 5 reaches variability of the results spatially
Flushing Flows
Analysis
Poudre River FEIS Assessment 10
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Summary of Results Presented in EIS Documents
The first flushing flows analyses in the EIS reports were performed in the SDEIS (2013 ) . This analysis
calculated the 'flushing flow' for every cross section in the hydraulic model using incipient motion
referenced to the median grain size ( D50) . The results ranged from < 10cfs to > 10 , 000cfs (SDEIS 2013 pg .
7- 11 ) . The SDEIS Effects Report released in 2014 showed that the impact of the different NISP
alternatives will reduce the duration of flushing flow values for all cross sections from 0-50% (SDEIS 2013
pg . 11 -3 & 11 -5 ) . The current ' preferred alternative' ( Run 3b ) showed a reduction of the duration of
flushing flows of 30-40% for 55% of the cross sections or little to no change for 45 % of the cross sections .
The cross sections that are estimated to not flush under existing conditions are included in the 45 % of
cross sections with little or no change .
Subsequent to the SDEIS Technical Reports (2013- 14 ) , the FFR (2017 ) identified different flushing flows ,
and those are presented in the table below. The analysis calculated the potential movement of individual
grains across a generic size class range from (2-64mm ) and used 53 riffle cross sections focused only on
the river from the confluence with the North Fork Poudre River to 1 -25 as opposed to using all cross
sections from the North Fork Poudre River Confluence to the South Platte Confluence as used in the
SDEIS Technical Reports (2013- 14) . This technique assumes this sediment is ' resting on top of the
coarse bed material matrix (or armor layer) in riffles . ' These results were averaged into 5 reaches and
values ranged from (5cfs - 6817cfs ) for the (2-64mm ) range .
Figure 5— Excerpt of flushing flows results using 2-64mm grain size range from FFR (2017) pg . 8 .
Table 2-1 Reach-Average Flushing Flows Computed with Riffle Cross Sections Considering Coarse Bed
Material Sample Data .
Laporte: Fort Collins:
Laporte: North Larimer County Fort Collins:
Study Reach Fork to Larimer Canal to Larimer and Coy Ditch to Timn FCRID
County Canal Larimer and Weld Canal to FCRID too 1-25
Weld Canal Coy Ditch
Grain Class Reach Avera a Flushing Flow cfs
Coarse Sand 2 mm 8 5 22 29 41
Very Fine Gravel 4 mm 20 11 43 63 97
Fine Gravel 8 mm 57 45 98 142 230
Medium Gravel 16 mm 187 177 225 346 583
Coarse Gravel 32 mm 556 681 586 1, 152 1 .959
I LVery Coarse Gravel 64 mm 1,667 1,873 30729 4,802 6,817
a of Riffle Cross Sections 10 14 5 15 9
The table below presents the final 'flushing flows' values selected in the FFR (2017 ) . These values are
equivalent to the estimated 2-year recurrence interval discharge under current operations at each of the
specified nodes using the point flow model developed in other EIS Reports . The basis for this decision is
not reported , but presumably, is based on the unfounded assumption that the contemporary Q2 of the
highly modified flow regime represents an important ecological threshold for the Poudre River regarding
fish spawning habitat.
Poudre River FEIS Assessment 11
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EXHIBIT A
Figure 6— Excerpt of final baseline flushing flow results (equivalent to current conditions Q2 flow)
presented in FFR (2017) pg . 19 .
Table 2-10 Baseline Flushing Flow Values.
Study Reach Flow Node Baseline Flushing Flows (cfs)
(Equal to Current Conditions 2-Year Q)
2 2,406
North Fork to Larimer County Canal 4 2,337
Laporte 7 2,250
Larimer County Canal to Larimer and Weld 8 1,999
Canal 12 10797
Larimer and Weld Canal to Coy Ditch 17 1,381
Fort Collins 20 1,300
Coy Ditch to FCRID
23 1,355
Timnath FCRID to 1-25 32 972
2 . 2 . 3 Effective Discharge
The only calculation of the Qeff was presented in the SDEIS Technical Report (2013 ) , and those same
results were presented in the FFR (2017 ) but further averaged into the new five reaches defined in this
report.
The SDEIS Technical Report (2013 ) calculated Qeff using SIAM in HEC-RAS . The SIAM model appears to
have used the Meyer- Peter, and Muller ( 1948 ) sediment transport equation , reach -averaged hydraulics ,
the point flow model created for the EIS , and a combination of surface and sub-surface grain size
distribution data . This is a relatively common methodology for calculating sediment transport , but there
are several factors that lessen the applicability of this methodology in the case of the Poudre River. There
have been many/countless advances in the prediction of bedload transport and use of the Meyer- Peter
and , Muller ( 1948 ) equation is no longer advisable/appropriate . Furthermore , it appears the surface and
sub-surface grain size distributions ( GSD ) were combined into one for the calculations which is not a
method supported by the literature and is also not appropriate for use in the Meyer-Peter Muller equation ,
as it is a surface- based transport relationship . Combining the surface and sub-surface GSD also biases
the effective discharge estimate toward a lower value .
In general , the Qeff values developed in the SDEIS Technical Report (2013 ) are relatively low compared
to other reported analyses for the Poudre River including those calculated herein . The values range from
(70-2200cfs ) for the entire modeled reach from the SDEIS Technical Report (2013 ) extending from the
confluence with the North Fork of the Poudre River through the Confluence with the South Platte . The
results range from (800-2200cfs ) for the study reach defined in the FFR (2017) that only extents from the
confluence of the North Fork of the Poudre River to 1 -25 . The FFR (2017 ) results are close to the reported
Q2 flows for the same extent using the current conditions hydrology. This is important because the
correlation between the SDEIS Technical Report (2013 ) estimated Qeff and the Q2 under current
operations was stated as a justification for selecting final ` Baseline Flushing Flows' equal to Q2 .
Poudre River FEIS Assessment 12
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EXHIBIT A
Figure 7— Excerpt of effective discharge , Qeff analysis results presented in SDEIS Technical Report
(2013 ) pg . 8-7
SIAMEffective 2% Annual 2-Year Flood
Reach
Annual study Reach Discharge * Exceedance Freq Flow
Reach Exceedanc%e Node
(cfs) Discharge (cfs) Discharge (cfs)
1 1, 600 (45) 4. 9% ( 69%) 2, 315 21406 2
2 11800 3. 6% 29238 21337 4
3 Laporte 1,400 6. 1% 29170 21250 7
4 900 9. 1% 11988 11999 8
5 800 8. 3% 19865 1, 797 12
6 FC1 21200 1. 2%
11704 11381 17
7 FC2 20100 1. 3%
8 21200 1. 2%
9 FC3 2,000 (400) 1.4% ( 7. 6%) 11694 11300 20
10 FC4 21100 1. 3%
11 FC5 21200 1. 2%
12 FC6 21200 ( 350) 1. 2% (9%) 1772 1, 355 23
13 21000 ( 35) 1. 0% ( 40%) 1603 972 32
Ti mnath
14 21200 (45) 1. 2% ( 33%) 1674 657 34
15 Windsor 21200 ( 35) 1. 2% ( 51%) 1 , 711 685 35
16 Greeley US 21200 ( 30) 1. 2% ( 59%)
17 70 ( 2, 200) 39% ( 1. 3%) 1 , 760 910 41
18
Greeley Ch 21200 (80) 1. 3% ( 33%)
19 100 ( 2, 200) 1. 3% ( 39%) 11802 991 43
20 GreeleyDS 100 ( 11800) 48% ( 2%) 11812 11120 47
* Values in ( ) indicate 2nd peak in curve
2 . 3 Summary
A review of the EIS reports raises concerns about the nature of the methods and analyses used , the
disconnect between analysis results and conclusions , and the reliance on qualitative observations to draw
conclusions about the impacts of NISP alternatives . Flushing flows can be defined many ways , and the
selected definition can change the analysis and results with significant implications for flood conveyance
and habitat . The definition and associated analyses should reflect the desired objectives of the flushing
flows . The analyses from the EIS reports calculated a reduction in flushing flows and sediment transport
capacity under NISP conditions although the conclusions state there will be minimum impact upstream of
1 -25 because it is supply limited . The supply limited claim is not backed by quantitative evidence and runs
counter to other analysis results . The Qeff results are generally lower than other reported values and on
the magnitude of a 1 -2 year flow ( indicating fairly regular mobilization of the channel ) although their
observations state that sediment rarely moves on the Poudre River.
The disconnect in the analyses and results from EIS Reports merited further examination of these topics
(flushing flows , Qeff, aggradation , and vegetation encroachment) to understand the potential impacts of
NISP operations . The following sections summarize the methods , analyses , and results that re-evaluate
these topics .
Poudre River FEIS Assessment 13
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Section 3— Methods and Results of Desktop - Based Analyses
To provide concrete evidence regarding the deficiencies described in Section 2 , we have replicated the
models and data from the EIS documents to perform shear stress and effective discharge analyses . In
addition , we present a new aerial photo analysis to investigate the magnitude and distribution of
vegetation encroachment near the City of Fort Collins .
The analyses performed in the FFR (2017 ) regarding flushing flows focused on the results of hydraulic
and sediment transport computations at riffle cross sections . Riffles are generally the focus of bed stability
analyses because the stability of the riffles controls the stability of the channel in pool-riffle (as defined in
Montgomery & Buffington , 1997) type streams . To facilitate direct comparison with the analyses
performed for the EIS , we focus on the same riffle sections . It is important to note that while we examine
the flushing and bed stability characteristics of the riffles for this analysis , the performance of flushing
flows are important in all areas of the river for different species' habitats and the maintenance of various
river health functions .
3 . 1 Recalculation of Flushing Flows Results Using D50
To understand the capacity of river flows to move sediment through the project area , excess shear stress
calculations were performed using the HEC-RAS 1 D hydraulic model and estimates of the diameters of
sediments (grain sizes ) in the channel substrate . The approach attempts to use the same data used by
the FFR (2017 ) , but the shear stress calculations for assessing which grain sizes are mobilized by which
flows were based on D50 rather than the (2-64mm ) grain size range . To understand the sensitivity of the
shear stress calculations to methodological differences , two approaches were used to perform the
analysis , following recommendations from the City's Ecosystem Response Model ( ERM 2014) . The
methods differ in that one calculates shear stress using energy grade line slope and hydraulic radius (the
default method in HEC- RAS) and the other uses hydraulic depth and friction slope . While in principle
' energy grade slope' and friction slope are synonymous , they are computed differently in HEC- RAS . The
friction slope essentially averages energy slope across two cross-sections and is less variable than
energy slope which is calculated at a point ( refer to the HEC- RAS Hydraulic Reference for more
information ) . The default shear stress output from HEC- RAS uses :
Shear Stress = yRSe
The alternative method for shear is calculated with :
Shear Stress = yDSf
With :
y = specific weight of water
R = hydraulic radius
D = hydraulic depth
Se = energy grade slope
Sf = friction slope
The potential movement of the representative D50 particle for each reach was estimated at different
critical shear stress thresholds and outputs are averaged into the same five reaches presented in the FFR
(2017 ) . The range of critical shear stress values follow the research of Milhous (2000 and 2003) which
was also used in the ERM (also shown below) . This technique assumes the applicability of the equal
mobility concept (Wilcock et. al 2009 ; Parker 2008 ) which states that large particles are relatively easier to
move because they protrude into flow, and smaller particles are harder to move because they hide behind
large particles . The flushing flow values range from 1135cfs to 8557cfs for the five T*c values using the
Poudre River FEIS Assessment 14
NISP Re-Analysis Otak
EXHIBIT A
alternative shear stress method (Table 2 ) . The flushing flow values range from 872cfs to 8277cfs using
the standard HEC- RAS method for calculating shear stress (Table 3 ) .
Table 2— Recalculated flushing flow results for range of T*c values using D50 and friction slope (T=yDSf) .
*C Reach 1 Reach 2 Reach 3 Reach 4 Reach 5
T
Reach Averaged Qcrit (cfs)
0 , 021 2476 3325 1850 2805 1135
0 , 03 3481 4350 3718 4158 2182
0 , 035 4221 4912 4653 5441 3984
0 , 047 6311 6760 6621 6982 6372
0 , 06 1 7857 7899 8557 8472 8538
Table 3— Recalculated flushing flow results for range of T*c values using D50 and energy slope (T=yRSe ) .
r*c
Reach 1 Reach 2 Reach 3 Reach 4 Reach 5
Reach Averaged Qcrit (cfs)
0 .021 987 1281 872 1290 1517
0 .03 1702 1956 2251 3224 3304
0 .035 2306 3081 4214 3911 4546
0 .047 4189 5559 4950 6139 7266
0 .06 5577 7367 6051 8246 8277
The thresholds for sediment movement represented by the critical shear stress values (0 . 021 -0 . 06 ) are
not discrete values but are probabilistic targets for different types of sediment movement along the river.
The excerpt from the ERM (2014 ) in Figure 8 below summarizes a description for the likely type of
sediment movement that could be expected in each T*c range based on Milhous (2000 and 2003 ) .
Following this table , the surface clearing of fine material is likely to occur with a T*c of (0 . 021 -0 . 035) , the
initial movement of the coarse bed material and releasing fines from the sub-surface is likely to occur with
a T*c of (0 . 035-0 . 06 ) , and general movement of sediment along the bed with T*c ( >0 . 06 ) . These are not
absolute thresholds but represent the most probable targets for different types of sediment movement
along a spectrum , with the upper bound of the range being the most likely to occur.
Figure 8— Excerpt summarizing a description of sediment transport processes associated with T*c ranges
following research from Milhous (2000 and 2003 ) who performed scour chain studies on the Poudre
River. Table from ERM (2014 ) pg . 28 .
Dimensionless shear stress (T• )
referenced to d5o
Sediment movement state Lower bound Upper bound
Fines and sand are stored 0 .009
Fines and sand in motion 0 .009 0.021
Surface cleaning and removal of fines 0 .021 0.035
Initial movement of armor and substrate cleaning 0 .035 0 .06
General movement of and cleaning of substrate 0.06-0 . 084 —
Source : Adapted from Milhous , 2000, 2003.
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The recalculated flushing flows results show large variability between the two methods used and each T*c
range . The friction slope in HEC-RAS is generally lower than the energy grade slope and therefore results
in higher flushing flow values required to move the same particles . The results are generally closer using
the two methods for higher T*c thresholds but can be on the order of +/- 100% of each other at the lower
thresholds of T*c (0 . 021 -0 . 03) , which are associated with physical stream responses most in question in
this analysis ( i . e . , the removal of fines from the bed ) . In some cases , there are jumps between
subsequent flow thresholds (e . g . , 0 . 03 to 0 . 035 ) of up to 2000 cfs . The recalculated values sometimes
align with the final baseline flushing flow values selected in the FFR (2017) but are in general much
higher ( up to 4100cfs higher for T*c =0 . 021 -0 . 035) .
The large variability of flushing flows results using different methodologies suggests a good amount of
uncertainty in the ability of calculated hydraulic metrics to determine the flows required to perform specific
flushing functions . Therefore , we decided this merited further investigation using additional analyses ,
including field-based evidence .
3 . 2 Aggradation and Vegetation Encroachment
3 . 2 . 1 Background
A reduction in river discharge generally will lead to a reduction in stream power and sediment transport
capacity therefore increasing the possibility of aggradation (accumulation of deposited sediment) and
woody vegetation encroachment. Aggradation physically increases the elevation of the river bed and
woody vegetation encroachment increases hydraulic roughness both of which lead to an increase in
water surface elevation (WSE ) and and elevated flood risk . Aggradation and vegetation encroachment
often function together in a bio-feedback loop . New deposition creates a favorable location for vegetation
to establish , then as vegetation matures it increases hydraulic roughness and traps more sediment .
In a natural meandering river, a vegetated point bar will encourage channel migration by pushing flow
away from the bar and scouring the opposite bank therefore maintaining channel capacity and creating
new deposition . However, in an urban setting such as the Poudre River through Fort Collins , where the
channel is laterally constrained , any new bar formation and vegetation encroachment reduces overall
channel capacity.
Although aggradation and vegetation often function in tandem , this is not always the case especially in
highly modified/urban settings . Water diversion practices along the Poudre River have drastically reduced
the available water discharge and in turn have reduced the sediment transport capacity as well as the
sediment transport continuity along the river. The diversion structures not only reduce water discharge but
also reduce flow velocity upstream of the structures and physically hinder bedload (coarse sand , gravels ,
and cobble sized material ) from being transported downstream . These combined factors can collectively
reduce the overall sediment transport supply moving through the Poudre River system . However, our
analyses suggest that the EIS reports underestimate the sediment supply through the City of Fort Collins
and therefore understate the channel aggradation impacts due to flow reduction from NISP . Further, the
reduction in stream power also limits the ability of the river to strip out vegetation and prevent
establishment and encroachment regardless of whether aggradation is occuring or not . Therefore , even if
sediment supply is only available during large flood events , the vegetation encroachment between events
could drastically increase the aggradation potential (flood risk) when the flood occurs .
3 . 2 . 2 Historical Aerial Imagery Analysis for Vegetation Encroachment
Aerial imagery was studied to evaluate how the sequence of previous flood and drought events have
influenced deposition , scour, and vegetation encroachment. The analysis was broken into the ten reaches
used in the SDEIS Technical Report (2013 ) ( Laporte 1 through Timnath reaches ) .
Poudre River FEIS Assessment 16
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1999 =2012 - Drought Years
The study first examined aerial imagery from October Td , 1999 to measure the area of recent deposition
from the April 1 , 1999 flood . Google Earth polygons were used to track and measure each depositional
bar area and vegetated areas on each bar. The 1999 aerial image is black-and-white and relatively poor
quality. Flood deposits were generally identified by their light color and configuration in the channel ( i . e .
lateral bar or mid-channel bar) . Vegetated portions of bars appear darker than the surrounding
depositional area .
The study then used the same methodology using an aerial image from August 18t" , 2012 . This aerial
image captures the effects of 13 primarily drought years after the 1999 flood event. The bars and
vegetated areas identified in the 1999 study were compared directly to the 2012 image . A new set of
2012 polygons were drawn for each bar. In most cases , there was no discernable difference in total bar
size or shape between 1999 and 2012 . However, most of the unvegetated bar areas in 1999 were
vegetated by 2012 . On average , the bars identified in 1999 were 38% vegetated , and those same bars
were 80 % vegetated by 2012 .
2012 =2017 - High Water Years
A third aerial image from October 14t" , 2017 was studied to evaluate the impact of the September 2013
flood event (which was similar magnitude as the 1999 event) and subsequent recovery period which had
several other relatively high flow years . The bars and vegetated areas identified in the 2012 study were
compared directly to the 2017 image . A new set of 2017 polygons were drawn for each bar. Aside from
comparing the individual bar areas , additional polygons for new depositional area were created to
accurately measure the overall ratio of vegetated bars to total bar area . On average , 11 % of the
vegetation identified in the 2012 aerial image did not appear in the 2017 image ( presumably this
vegetation was scoured or drowned in the 2013 flood event) . The total area of deposition increased 17%
on average .
Table 4- Summary of results from historical aerial analysis for vegetation encroachment.
Aerial Year 1999 2012 2017
Reach Total Total Percent Total Total Percent Total Total Percent
Bar s V Vegetated Bar s V Vegetated Bar s V s Vegetated
Iaportel 461,306 1463614 32% 4633460 3693193 80% 5982846 341,507 57%
Iaporte2 324,986 113,978 35% 308,748 265,254 860/c 4153293 235,141 57%
1aporte3 498,979 79,894 16% 493,519 4203507 85% 6192020 353,207 57%
FC1 86,882 27,427 32% 96,814 86,076 89% 93,099 44,534 48%
FC2 121,970 52,810 43% 127,522 1183324 93% 1103412 922849 84%
FC3 34,290 123917 38% 32,857 32,756 1000/0 35,637 2%584 83%
FC4 78,777 28,888 37% 84,167 82,774 98% 8%815 58,220 65%
FC5 141,185 73,306 52% 142,630 130,210 91% 1582025 121,105 77%
FC6 503,272 261,644 52% 509,701 401,442 79% 534,696 384,663 72%
Timna 711,402 319,536 45% 727,435 659,820 91% 837,210 6143527 73%
Total Z9633049 13117,013 38% Z9862852 2,566,356 86% 3,492,052 2,275,337 65%
Sources of error
The apparent size of a given bar can vary depending on the flows on the day the aerial image was taken .
Table 5 provides the flows recorded at three gages within the study area . These flow data alone are not
always sufficient to account for apparent bar size differences because diversions can affect flow levels
between the gages . Some judgment was required to assess whether a given bar had changed size during
the study period , or if the bar was simply more exposed or inundated due to flow differences . Lastly, this
analysis only accounts for two-dimensional changes in bar area and is unable to capture the changes of
Poudre River FEIS Assessment 17
NISP Re-Analysis Otak
EXHIBIT A
bars in the vertical direction . Although there is uncertainty in the analysis , the flows at each gage were
close (Table 5) , and the analysis is able to provide an informative outlook on the historical vegetation
encroachment near the City of Fort Collins .
Table 5— Comparison of discharges at three gages for the date of the aerial analyzed for vegetation
encroachment.
Date of Aerial Canyon Lincoln Boxelder
Analyzed Gage (cfs ) Gage (cfs ) Gage (cfs )
10/3/ 1999 90 103 75
8/ 18/2012 192 103 100
10/14/2017 107 150 96
Trends of Aggradation
The aerial analysis also revealed a large scale trend which can be identified by comparing the change in
total bar area along the study reach . There is larger total bar area at the upstream side of the study reach
( Laporte 1 -3) , less in the middle sections around the City of Fort Collins ( FC 1 -5) , and larger total area
again near the downstream end approaching 1 -25 ( FC 6 and Timnath ) . This trend aligns with what is
expected when considering the large scale natural and anthropogenic geomorphic controls in the system .
The upstream section of the study reach is located in an alluvial fan zone which is the transition between
the confined canyon to the less confined , milder slope front range . This transition generally leads to
reduced stream power and is therefore a naturally depositional area for mountain river systems . The river
is then artificially confined and constrained laterally by gravel mining activities and infrastructure through
the City of Fort Collins . These influences typically increase stream power which will lead to less
accumulation of sediment; however, this section has also been cleared and dredged of debris and
sediment historically ( including around bridges on an annual basis ) . Lastly, near the downstream end of
the study reach exiting the City of Fort Collins , there is less infrastructure , confinement, and lower
channel gradient leading to a reduction in stream power and increase in aggradation . This downstream
response may indicate that coarse supply is moving through the system , so as flow is decreased through
the City (i . e under NISP operations) less will move through leading to aggradation . Lastly, the cumulative
sediment transport capacity for ` upstream of 1 -25' under the preferred alternative for NISP operations
(SDEIS Technical Report 2014 ) is projected to be reduced to a magnitude similar to `downstream of 1 -25'
under current conditions . This suggests that ` upstream of 1 -25' under NISP conditions could experience
aggradation similar to what is occurring `downstream of 1 -25' currently.
3 . 3 Recalculation of the Effective Discharge
An effective discharge calculation was performed for this report over a sub-reach from the SDEIS called
FC1 (see Figure 7) that goes from the Larimer and Weld Canal to Wood St. As the results presented in
the EIS documents were calculated with inadequate methods and differ from those calculated for the
ERM , this analysis was performed to present one comparison using transport models appropriate for the
Poudre River system .
The following data and techniques were used :
Grain Size : 300 count sample by Otak using a grid sampler at the riffle upstream of Shields Bridge .
Hydrology : Available 15-min data from Lincoln gage for water years 1988-2017 . Flows were sorted into
25 arithmetic bins .
Hydraulics : Reach averaged hydraulics from the SDEIS 1 D HEC- RAS model were used for the FC 1
reach from Larimer/Weld Canal to Wood St. The cross sections at diversion structures and bridges were
removed but the the expansion/contraction cross sections of the bridges were left in .
Poudre River FEIS Assessment 18
NISP Re-Analysis Otak
EXHIBIT A
Shear Stress : The analysis was done with two ways of calculating shear stress from HEC- RAS
for comparison . One method follows the default method from HEC-RAS for calculating shear
using Shear = yRSe , and the second approach follows suggestions from the ERM (2014 ) with
Shear = yDSf .
Sediment transport equations : Parker ( 1990 ) and Wilcock and Kenworthy (2002 ) surface-based
bedload sediment transport equations .
Table 6—Summary of recalculated effective discharge , Qeff using two methods of calculating shear stress .
Effective Discharge, Qeff (cfs)
Using Shear = yDSf Using Shear = yRSe
4050cfs 2100cfs
Figure 9— Plot of Qeff analysis results ( peak is Qeff) using T = yDSf (friction slope) and Parker ( 1990 ) and
Wilcock and Kenworthy (2002 ) bedload sediment transport equations for reach FC1 from SDEIS
Technical Report (2013) .
0. 08
0.07
T 0.06
0.05
N
v 0.04
c
a)
0.03
a)
Lu 0.02
0.01
0
0 1000 2000 3000 4000 5000 6000 7000 8000
Discharge ( cfs )
Parker ( 1990) —*--- Wilcock & Kenworthy ( 2002 )
Figure 10— Plot of Qeff analysis results ( peak is Qeff) using T = yRSe ( Energy Slope) and Parker ( 1990 )
and Wilcock and Kenworthy (2002 ) bedload sediment transport equations for reach FC1 from SDEIS
Technical Report (2013 ) .
Poudre River FEIS Assessment 19
NISP Re-Analysis Otak
EXHIBIT A
0.4
0. 35
a
0. 3
0. 25
Ln
Ln
v 0. 2
c
v
0. 15
v
"' 0. 1
0.05
0
0 1000 2000 3000 4000 5000 6000 7000 8000
Discharge (cfs)
-0-- Parker ( 1990) f Wilcock & Kenworthy (2002 )
Similar to the recalculation of the flushing flows values , the results using different methods to calculate
Qeff varies widely. Using the alternative method of calculating shear stress using friction slope and
hydraulic depth , estimates two distinct peaks at 7650cfs and 4050cfs using both the Parker ( 1990 ) and
Wilcock and Kenworthy (2002 ) bedload sediment transport equations . Using the default HEC-RAS
method of calculating shear stress using energy grade slope and hydraulic radius , estimates an effective
discharge of 2100cfs using both transport equations . The effective discharge calculated in the SDEIS
Technical Report (2013) for the same reach was 2200cfs . The nearest section of river from the ERM
(2014 ) to this reach is Reach 3a which extends from the Taft Hill to Shields St. crossings . The effective
discharge from Reach 3a in the ERM (2014 ) is 3350cfs using the Parker et al . 1984 equation and 2120cfs
using the Wilcock and Crowe (2003 ) equation .
Section 4— Methods and Results of Field - Based Analyses
4 . 1 2018 Runoff Field Studies
Two field studies were conducted during the spring and early summer of 2018 to produce field -based
evidence for mobilizing sediment in riffle features and the ability of the peak flows to remove plant
seedlings on bars . These field- based studies were also used to corroborate and improve interpretation of
hydraulic and sediment transport modeling . The first part of the studies included placing tracer rocks
( brightly painted river rocks) of different size classes at several riffle features and taking photos of plant
seedlings on bars before the 2018 runoff occurred then returning to the same locations to observe the
effects of the peak flow after the runoff occurred . These investigations provide additional lines of evidence
that can be used in conjunction with the hydraulic modeling to provide additional insight into the mobility
of the channel bed , how that mobility may be impacted by vegetation , what we may expect moving
forward , and a starting point for potential long-term monitoring opportunities .
Poudre River FEIS Assessment 20
NISP Re-Analysis Otak
EXHIBIT A
4 . 1 . 1 Tracer Rocks
Methods
Tracer rocks were placed at six locations on representative riffle features near the City of Fort Collins from
approximately Shields St. Bridge to the Boxelder gage and analyzed for movement after the 2018 runoff
event. The selected locations were aligned with the 53 riffle cross sections used in the FFR (2017 )
analysis when possible to provide the most direct comparison to the modeling calculations (4 out of 6
locations align with the 53 FFR 2017 riffles) . For the four cross sections that aligned with model , we
calculated the critical dimensionless shear stress (T*c) for motion using an estimate of the 2018 runoff
peak flow ( using gage and diversion data ) , the same D50 values as the flushing flows analysis , and both
methods described above for shear stress ( using energy grade slope , Se and friction slope , Sf) (Table 8 ) .
Rocks for the study were collected downstream of Shields St. Bridge in three size class ranges using a
gravelometer and then painted a different color according to the size class (Table 7) . For reference , the
D50 values used in the analysis from the canyon mouth to 1 -25 ranged from
(56mm-85mm ) .
Table 7—Summary of colors the tracer rocks were painted for each size class in study.
Size Class 32-45 mm 45-64 mm 64-90 mm
Color Orange Green Yellow
Painted
Groups of three tracer rocks ( 1 of each size class ) were placed at ten locations equally-spaced across a
transect on each riffle for a total of thirty tracer rocks at each cross section ( Figure 11 ) . When placing the
tracer rocks , we attempted to match the embeddedness to the local bed sediment by pushing the rocks
into the surface layer rather than setting them on top which would have exposed them to elevated shear
stresses and hence biased the sediment mobility. The exact locations of the rocks were placed randomly,
hence some tracer rocks were hiding behind larger rocks and others were exposed .
Figure 11 — One grouping of tracer rocks placed pre- runoff in a riffle within the bankfull channel .
-x.
Off
t-..
P
e y� Sr
Y.
4
a
t
Poudre River FEIS Assessment 21
NISP Re-Analysis Otak
EXHIBIT A
Table 8—Summary of tracer rock cross sections locations and associated parameters .
Tracer Is it a FFR Approximate Calculated T*c Calculated T*c
Rock Location (2017) riffle 2018 Peak referenced to D50 referenced to
XS Description cross section ? Flow (cfs) with T=yRSe D50with T=yDSf
1 US of Shields St. Yes , ~ 1800 0 . 043 0 . 014
Bridge (XS 242265)
US of the Gage
2 Bridge ( Lee Yes , ~ 1800 0 . 023 0 . 014
Martinez Park) (XS 238538 )
Between Lincoln
3 St . and Mulberry No ~ 1550 n/a n/a
St. Bridges near
Woodward
Downstream of
Timberline Rd . Yes ,
4 Bridge near (XS 215717 ) ~ 1550 0 . 016 0 . 025
Riverbend Ponds
Natural Area
Upstream of
5 Prospect Rd . Yes , ~ 1550 0 . 018 0 . 028
Bridge (XS 212726)
6 Upstream of No ~ 1450 n/a n/a
Boxelder Gage
Results
After runoff we revisited each cross section and noted one of three outcomes for each tracer rock ; either
a tracer rock was found in the same location as placed ( assumed no movement) , a tracer rock was found
downstream of the original location ( assumed to move ) , or a tracer rock was not found (conclusion based
on other evidence ) . In general , rocks that were not found appeared to have moved . In a few cases the
rocks were found buried under newly transported material indicating that the upstream bed mobilized .
Thus , we assumed bed mobility occurred if the rocks were not found . Table 9 summarized the results of
the study.
Table 9—Summary of tracer rock field study results.
32-45 45-64 64-90
Tracer mm mm mm Transect Notes
Rock % of Total
Cross Maximum Number of Rocks Mobilized Longitudinal Representative Approximate
Section Mobilized (out of 10) Location on of Riffle ? Channel
Riffle Width (ft)*
1 10 9 8 90% middle good 63
2 7 6 7 67% middle good 80
3 8 3 4 50% middle and top okay 84
4 9 7 8 80% middle good 70
5 8 2 5 50% bottom bad 57
6 8 2 2 44% top okay 75
*Active channel width during the time fieldwork was conducted
Poudre River FEIS Assessment 22
NISP Re-Analysis Otak
EXHIBIT A
The ` maximum number of rocks mobilized ' results include the rocks not found that were assumed to move
or were covered by other material on the riffle that was mobilized upstream . These results represent the
upper bound of potential movement of the tracer rocks . With these assumptions , the total percent of
tracer rocks mobilized at each cross section ranged from 44%-90 % . These results generally align with
observations of the bed during fieldwork such as the looseness of the bed material , the pre- and post-
runoff amount of embeddedness and algae , fine material present, etc . In general , the movement of the
tracer rocks could be described as having ` randomness and patchiness ' which matches expectations for
natural sediment transport processes , but also hinders the ability to interpret the results and identify
trends for other locations and river habitats .
The calculated T*c values presented in Table 8 show that there are very different estimates of the type of
sediment transport that could be expected based on the method of shear stress used (Se vs . Sf) . There is
substantial spatial variability in T*c among cross sections with similar flow values . In the case of tracer
rock cross sections ( 1 and 2) , the calculated T*c using the Se method for shear aligns closer with the field
observed estimates . However, for tracer rock cross sections (4 and 5 ) , the calculated T*c using the Sf
method for shear aligns closer with what was expected based on field observations . If the calculated
values are used as a potential range of T*c , then the field-based estimates align with the calculations
better overall , but generally the calculated values underestimate field values . These comparisons suggest
that computational tools alone are inadequate to understand flushing flows dynamics on the Poudre
River, and a more holistic understanding requires a variety of field , desktop , and computational methods .
4 . 1 . 2 Pre - and Post - Runoff Vegetation Encroachment Photos
Before the 2018 runoff event, point bars and mid-channel bars near the City of Fort Collins (from near
Laporte Middle School to Prospect Rd . Bridge ) were examined for plant seedlings that may continue to
establish and increase vegetation encroachment in the future . These bars were photographed before and
after the 2018 runoff event to understand the effect this peak event had on scouring vegetation . While this
exercise has limitations , it presents another line of evidence for understanding vegetation encroachment
near the City of Fort Collins and can be the start to a longer-term monitoring opportunity.
Results
The plant seedlings most commonly present on the bars were Coyote Willow ( Salix exigua) followed by a
mixture of Plains Cottonwood (Populus deltoides monilifera) , Narrowleaf Cottonwood ( Populus
augustifolia), Peachleaf Willow ( Salix amygdaloides) , and Reed Canary Grass (Phalaris arundinacea)
depending on location . Overall , there were no noticeable changes in the vegetation pre- and post-runoff
and no indication that vegetation was scoured during the event . Several areas also showed signs that the
plants were not touched by the peak flow event or barely inundated . This is problematic for the City
concerning vegetation encroachment because the roots of tree seedlings get locked around cobbles in as
little as 2-3 years and then they require exponentially more shear stress to rip out .
The results from this study indicate that the 2018 runoff event did not have the capacity to scour newly
established vegetation with very shallow and weak roots in the areas that were examined . This is very
important for the City of Fort Collins , because if runoff events in the future are similar to the 2018 event or
less then there will be a high likelihood that woody vegetation will continue to establish , increasing
roughness along the channel boundary, reduce the mobility of the surface upon which they are growing ,
and ultimately lead to reduced channel capacity, vertical accretion , and increased flood risk . However,
many bars including the examples shown below, had a distinct difference in age class between the new
plant seedlings and the surrounding vegetation . This can be an indication that there were recent runoff
events that were able to scour or drown new plant seedlings before establishing . This would most likely
be correlated to the 2013-2015 large runoff events .
Poudre River FEIS Assessment 23
NISP Re-Analysis Otak
9 �
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EXHIBIT A
• • • ( looking • • of bar on river left just upstreamof Overland Trail Bridge in May
2018 (above ) and July 2018 ( below) .
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EXHIBIT A
Figure 13— Photo ( looking upstream ) of bar on river right adjacent to North Shields Ponds Natural Area
in May 2018 (above ) and July 2018 ( below) .
1 ,
IAL.
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y 1*
/p
i
. rt
x`wt
AI
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Figure 14— Photo ( looking upstream ) of bar on river left adjacent to McMurry Natural Area in May 2018
(above ) and July 2018 ( below) .
Poudre River FEIS Assessment 26
NISP Re-Analysis Otak
EXHIBIT A
4 . 1 . 3 Case Study for Vegetation Encroachment and Aggradation
One representative lateral bar feature was selected and examined further to understand the potential
combined effects of vegetation encroachment and aggradation within the City of Fort Collins . The bar is
located on river right, just upstream of the Shields St. crossing ( Figure 15 ) and represents an example of
potential aggradation in a lower energy zone associated with a crossing , with potential impacts to critical
infrastructure . This bar was observed to be created during the 1999 runoff event and has progressively
encroached with vegetation since then . Historical aerial photos indicate that even the 2013 flood event
was not able to strip out the vegetation present on the bar which has implications for future flood risk
concerns . We examined the depth of fine material deposited on the bar with a 4 ' steel soil probe to
estimate how much sediment has been trapped on the cobble bar since its initial formation .
w ..
No
# s a Ito
r
to
- r vILim. to ..T . JI
t to
o
Figure 15— Photo (looking upstream ) in 2018 of case study point bar on river right just upstream of
Shields St. Bridge .
The bar currently has around 1 - 1 . 5' of fine material deposited on top of a coarse layer near the channel -
side margins of the bar as shown in Figure 15 , and up to around 4' of deposition near the center of the
bar ( Figure 16 and 17 ) .
Poudre River FEIS Assessment 27
NISP Re-Analysis Otak
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EXHIBIT A
This particular bar was chosen because of the length of available observations and its proximity to
infrastructure . The bar provides an example of channel encroachment during lower flow years that
reduces the available space for flow conveyance during higher flow events . Observations of rapid vertical
accretion in the channel margins have been noted by others in similar scenarios where high stage is
accompanied by large concentration of fine sediment ( Milhous chapter in Gravel Bed Rivers book) . These
fine sediments then deposit along the channel margin or lower energy areas , providing a surface for
vegetation to grow (Wilcock et al . , 1996 ) . Our case study of the bar shows evidence of this exact process .
According to the results of transport capacity calculations reported in the EIS documents , NISP will
exacerbate this process through reductions in transport capacity. While the example above focuses on a
single lateral bar, the Poudre through the study reach has many similar locations where crossings are
encouraging the development of bank-attached bar formations .
4 . 2 Embeddedness
When considering the definition of flushing flows as disturbing the bed sufficiently to release fines from
the interstitial spaces , embeddedness directly relates to flushing flows and can be an indicator of the
occurrence and effectiveness of flushing . If a riffle feature , for instance , is highly embedded then the riffle
has most likely not been disturbed nor mobilized the bed enough to release fines from the interstitial
spaces of the coarse sediment, indicating a lack of recent flushing . With the newest definition of flushing
flows from the FFR (2017 ) only requiring the removal of fines from the surface fines embeddedness may
not directly relate to the occurrence of flushing . Under this definition , a riffle may be highly embedded and
still be `flushing ' as mobilizing fines on the surface does nothing for the interstitial spaces . Alternatively, it
could be argued that to have a layer of fine material resting on top of the coarse riffle sediment, there
would have to be enough embeddedness to negate the impacts of grain hiding , packing , and other
behaviors that limit the transport of fines . Therefore , the chosen definition of flushing is only possible if
one subscribes to the notion that the Poudre River is static and canal- like .
The EIS reports did not directly describe observations related to embeddedness , however there are
indirect implications that can be made from other stated observations . The reports describe the Poudre
River as being very armored with a layer of fines sitting on top of the coarse material in many locations
especially downstream of I -25 and into Greeley. This does not align with observations from Otak's
fieldwork in 2016 , 2017 , and 2018 . Otak recognizes that observations described in the EIS were
presumably made around 2012 which happened to be at the end of a 13-year drought period that had
very low peaks from 1999-2012 . In contrast, our observations were after the large 2013 flood event
followed by a relatively wet period with higher flood peaks . Otak does not doubt that the river was more
embedded and armored with more surface fines during 2012 .
However, the newest analyses in the EIS Reports appear to assume these same observations even
though the Flushing Flows Report was released in 2017 . Desktop and field-based evidence suggests that
the September 2013 flood was large enough to change the river to the point where the assertion (that the
channel is well armored ) is no longer valid . The assumption that the Poudre River is armored is used as a
basis to justify many decisions in the EIS documents (e . g . , modeling approach , calculation of effective
discharge) . In this case , the assumption being no longer valid creates uncertainty around if the methods ,
results , and conclusions in the EIS reports still apply to the current state of the Poudre River. The 2013
flood was a large disturbance event which rejuvenated many portions of the substrate , therefore there is
an opportunity to continue this healthy trajectory along the Poudre River. But , the reduced sediment
transport capacity under NISP will decrease the likelihood of maintaining this ` healthy substrate'
trajectory.
Poudre River FEIS Assessment 30
NISP Re-Analysis Otak
EXHIBIT A
Section 5— Discussion
The results of the multiple lines of evidence discussed above highlight the inadequacies of the EIS
analyses and interpretations and yield evidence of a very different perspective on the geomorphology and
likely geomorphic trajectory of the Poudre River under NISP .
5 . 1 Flushing Flows and Sediment Transport
The results of the review of the flushing flows analyses performed for the EIS and our own analyses
( including both calculations and field investigations) indicate that invalid assumptions made regarding the
geomorphology of the Poudre River skewed the interpretation of the analyses results . Our multiple- lines-
of-evidence approach contradicts the conclusion that the Poudre is supply-limited with thus be minimally
affected by NISP .
5 . 1 . 1 EIS Reports Flushing Flows Analyses
The approaches used for the analyses presented in the EIS documents are non-standard , ambiguous ,
and not well documented in the literature . The interpretations of the results of the methods are often
based on large assumptions and are contrary to the results of the transport calculations .
As stated previously, the decisions to change definition of flushing and the methods chosen to define the
flushing flow essentially nullified previous results from their other analyses which showed large variability
throughout the study reach and bases the determination of flushing solely on hydrology A ) rather than
hydraulics or sediment transport. While in coarse-grained , self-adjusted , equilibrium channels Q2 has
been shown to have morphologic significance , the Poudre River through Fort Collins does not meet those
assumptions . The Q2 flood discharge has been drastically reduced with the current hydrologic regime ,
and infrastructure confinement and bank armoring , etc. has limited the ability of the stream to respond
geomorphically to the changes . Therefore , a Q2 discharge based on the current hydrology could
drastically underestimate the flow required to perform the functions expected from a Q2 flood on a ' natural
stream . ' Furthermore , flow frequency metrics such as recurrence intervals (e . g . , Q2) only describe
average conditions . Stream resiliency is developed by experiencing conditions outside of the averages .
As the analysis presented in the EIS documents only examines average conditions , many questions
remain as to how NISP will impact the river's resilience .
It intuitively seems that there would have to be a notable amount of deposition and/or embeddedness
present in a riffle for a grain size range of (2-64mm ) to be resting on top of the coarse 'armor layer. ' One
of the justifications for using the (2-64mm ) grain size range cites Raleigh et al . ( 1986) who presented the
optimal grain size range for brown trout spawning to be ( 10-70mm ) . However, this paper also stated that
" potential spawning sites are characterized by upwelling of water through the gravel or by the presence of
water current flowing downward through the gravel " ( Raleigh et al . , 1986 pg . 8 ) . These characteristics
describe conditions with high amounts of hyporheic exchange that requires 'clean ' interstitial spaces in
the coarse bed material layer. This creates favorable spawning habitat by helping to decrease and
maintain water temperature and increase dissolved oxygen content . According to the definition of flushing
flows presented in the FFR (2017) , the river bed may be completely armored and/or embedded , yet still
provide good fish spawning habitat if the fines are swept off the surface . This assumption does not align
with the habitat requirements presented in Raleigh et al . ( 1986 ) .
Furthermore , the language used for the flushing flows definition simplifies the channel bed into a 'surface . '
While this simplification may be necessary within a modeling context, interpretation of the results of the
modeling need to account for the simplifying assumptions . The 'surface' is an assemblage of fine
sediments , gravels , cobbles , and boulders with substantial roughness characteristics that forms a
complex channel bed where smaller rocks are hidden behind larger rocks . The notion that fines can be
swept off the surface implies that the channel bed is substantially embedded to begin with , which is
simply not the case for large portions of the Poudre River after recent high flows .
Poudre River FEIS Assessment 31
NISP Re-Analysis Otak
EXHIBIT A
In summary, the final flushing flow values presented in the FFR (2017 ) are likely underestimates of the
flows necessary to provide both the stated functions and those acceptable to the City. Our recalculation of
the flow metrics , combined with targeted field investigations suggest that the calculations performed for
the EIS process are not able to answer fundamental questions regarding the sediment and channel
maintenance capabilities of the Poudre River.
5 . 1 . 2 Recalculation of Flushing Flows
When comparing the sediment movement ranges from Milhous' research ( Milhous 2000 and 2003 ) to the
flushing flows results using D50 , there are a wide range of discharges that correlate to each range of T*c
values . Furthermore , when comparing the results using D50 to the results from the FFR (2017 ) there are a
large range of possible conclusions depending on which analyses are used . This generally highlights the
fact that there is much uncertainty in calculating sediment transport and additional analyses including
field-based evidence are merited to converge on more reliable estimates of flushing flows . Also , the
nature of sediment transport, in reality, is spatially patchy in a river and sporadic , therefore the threshold
to mobilize sediment varies for different areas within the river based on the particular sediment
composition , configuration , etc . Thus , maintaining higher flows will only increase the probability of
initiating different types of sediment transport in more areas of the river rather than increasing transport
uniformly across the entire channel . These factors consequently merit the use of flushing flows as
probabilistic ranges rather than discrete values . Furthermore , in gravel/cobble bed streams , the threshold
nature of sediment transport initiation and exponential flow vs sediment flux relationship , dictate that
minimal transport will occur until the threshold is reached . Therefore , getting half of a `flushing flow' will
not equal half of the flushing .
Comparing the results from using D50 to the final baseline flushing flow values selected in FFR (2017)
raises some concern about reaching the threshold for transport necessary for flushing the intersitial
spaces of the coarse substrate or even surface fines . All the baseline flushing flow values are less than
the calculated values using D50 with a T*c of 0 . 021 . This is defined by Milhous to be the lowest threshold
for sweeping fines from the surface layer, so values below this will be unable to provide that function and
even less likely to flush interstitial spaces . The technique used to calculate flushing using the D50 may be
overestimating the required flushing flow, but also indicates that the baseline values provided in the FFR
(2017 ) could also be highly underestimated .
5mU Tracer Rocks Field Study
The moderate spatial variation of tracer rock mobility was in line with what could be expected from this
type of field study. Some of the highlights include : ( 1 ) particles in the 32-45mm grain size class moved the
most (84 % average mobility with a range of 70- 100 % ) at every cross section which intuitively makes
sense because smaller grains are easier to transport, and (2 ) far fewer particles in the 45-64mm size
class and 64-90mm size class moved than the finer tracer rocks and with much higher variation . These
results indicate that the flows from the 2018 runoff event most likely had the sediment transport capacity
to mobilize sediment in the 32-45mm grain size range and below, but the larger two size class ranges are
less certain and sporadic. Numerous factors such as the rock orientation , embeddedness , hiding or
protruding factor, and the movement of sediment around the tracer rocks , etc. could have influence on the
transport.
Impacts of Location and the 2013 Flood
It should be noted that the tracer rock study results were heavily influenced by the location of the cross
sections and the impacts of the 2013 flood and proceeding higher water years before this year's runoff.
The tracer rock cross sections were selected to be only on riffle features which can be the areas of
greatest overall shear stress and capacity to move sediment during low to moderate flow events . The
2013 flood was a large disturbance event that was able to move sediment throughout the river system
therefore loosening the bed material and decreasing embeddedness . This ` looser' bed is much more
primed for movement and thus requires less flow to mobilize the sediment. This is opposed to having a
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long period where the bed moves minimally and becomes very embedded such as in 2012 after the
drought period that began in 1999 . The initial 10-year filling period of Glade reservoir, depending on the
runoff characteristics during those years , could create drought-like conditions on Poudre River. We
should expect vegetation to encroach upon the channel substantially during that time . As seen in 2013 ,
10 years of woody plant growth will most likely be too much for the next flood to remove ( i . e . , as observed
in the 2013 flood ) given the significant rooting strength that woody vegetation typically develops in three
or fewer years . This vegetation establishment and the resulting sediment deposition , will increase flow
resistance , decrease channel capacity, and ultimately lead to inundation of a larger than anticipated area .
5A A Recalculation of the Effective Discharge
The results shown in Figures 9 and 10 using the two different methods of shear stress suggest several
potential conclusions regarding the calculation of Qeff. We interpret the results by examing the definition of
the effective discharge . The Qeff is one approximation of the ` channel forming ' discharge and can be
thought of as the discharge that moves the most sediment over a period of years , . In self adjusted , coarse
grained channels , these two concepts often correlate , however this is often not true in modified , urban
systems . We perceive the 4050cfs and 7650cfs peaks from Figure 9 to be most representative of a
current `channel forming ' flow, in the sense that those flows have the capacity to move the coarser
fraction of the bed that defines the channel 's morphologic character. The 2100cfs peak in Figure 10
possibly represents the flow that moves the most sediment over time , but does so on the assumption of a
large supply of fine sediments .
The 7650cfs peak in Figure 9 is probably overestimated because all of the data for this flow came from
the one 2013 event using 15min flow data . However, it is important to capture the recent `wetter' years
the Poudre River has experienced in this analysis , to most accurately model the current hydrologic
regime . These results indicate that these really large flood events may be more `effective' than we think
they are . This means that the frequency of floods with the high magnitude and sediment transport
capacity of 2013 is perhaps underestimated and may occur more than expected . For instance , there were
other events of similar magnitude in 1983 and 1999 as well . However, we believe the second peak of
4050cfs in Figure 9 is probably the most representative Qeff for this reach as a channel forming discharge .
These calculations suggest that it may require a less frequent flood event to fully mobilize the larger
material such as coarse gravels and cobbles that make up the grade controlling bedforms of the Poudre
River. This aligns with expectations because the sediment transport capacity as been greatly reduced
from existing diversion operations . With less sediment transport capacity, it requires higher, less frequent
flood events to mobilize the coarse bed layer to rearrange and develop new bedforms . This higher Qeff,
closer to the historical Q5 event, also aligns with our studies on the Lower Poudre River ( Lower Poudre
Master Plan 2017) , where we did sediment transport analyses from I -25 to the South Platte River
confluence .
Even though the SDEIS Technical Report (2013) report used grain size data that combined surface and
sub-surface samples and the Meyer- Peter Muller ( 1948) equation , our peak in Figure 10 aligns with their
Qeff results . The result for this reach from the SDEIS Technical Report (2013) was Qeff = 2 , 200cfs . From
examining the per grain size results from the SDEIS Technical Report (2013) it appears this discharge
may be an important threshold for moving finer material such as 16mm and below on the Poudre River.
This does not mean , however, that it is capable of meeting the management objective of either
maintaining spawning habitat and/or maintaining channel conveyance .
5 . 2 Aggradation and Vegetation Encroachment
The theme in the EIS Reports regarding aggradation and vegetation encroachment stays relatively
consistent and concludes that the Poudre River upstream of 1 -25 will be minimally impacted under NISP
operations . This conclusion heavily relies on the qualitative observations that the river is `supply limited '
and shows little signs of current large-scale aggradation or biogeomorphic feedback loops occurring . The
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conclusions on aggradation and vegetation encroachment seem to disregard the analyses performed in
the SDEIS Technical Report (2013) , and there is no evidence or analyses presented that support the
claim of the river being `supply limited ' upstream of I -25 . The reports recognize that channel contraction
from vegetation encroachment may be increased under NISP conditions , however the impacts are
presumed to be minimal because there is no sediment to cause aggradation (supply limited ) .
This conclusion of the channel being supply limited contradicts evidence from our desktop- and field-
based analyses that show many examples of channel contraction with both Reed Canary Grass and
woody species such as Coyote Willows that contract the channel .
There are limitations to the aerial analysis approach ; however, there are a few large scale trends that
were identified from the analysis that can have important implications for future vegetation encroachment
and potential flood risk on the Poudre River.
Future Implications on Vegetation Encroachment
The general change in total vegetation between 1999-2012 indicates there was a large amount of
vegetation encroachment that occurred during this drought period . Furthermore , the comparisons of the
2012-2017 photos , although less certain results , showed that the 2013 and subsequent high flow years
were apparently able to scour or drown around one fourth (�25% ) of vegetation but not enough to come
close to returning to the amount present in 1999 . This has important implications for flood risk near the
City of Fort Collins because eventhough the 2013 flood peak was larger than the 1999 flood peak it was
evidently less effective at scouring vegetaion and therefore has led to overall less river conveyance as
compared to 1999 . This is most likely because the vegetation that was recruited after the 1999 event was
able to establish and mature for over 10 years , increasingly becoming more erosion resistant , with the
absence of flows that were able to cause significant mortality by scouring and/or drowning the plants . This
has important implications for vegetation encroachment in the future because in the event there is
another drought period similar to 1999-2012 there would presumably be even more encroachment,
increased flow roughness , and would require a higher peak flow to scour vegetation .
The chance of having a low flow period similar to 1999-2012 is arguably greater under NISP conditions .
Some of the most drastic changes to the hydrology under NISP will be during the initial ten year filling
period of the new reservoir. Reducing flows for this long of a time period can increase the chance of
having conditions and vegetation encroachment similar to the 1999-2012 period . It can be argued that
NISP will not affect the largest flood events such as 2013 and thus will not affect the present ability of the
river to scour vegetation . However, the reduction of the medium and low flows events can also be
important for future vegetation encroachment, because during an average flow year the mechanism most
likely to control new vegetation growth maybe drowning rather than scour. Field observations suggest
seedlings that start to establish each year are potentially more vulnerable to being drowned rather than
scoured under the current hydrology conditions . Therefore , under NISP operations , the recruitment and
establishment of new vegetation could be increased since there will be less flow for longer durations of
time .
5 . 2 . 1 Field Studies for Vegetation Encroachment and Aggradation
The pre- and post-runoff vegetation photos and point bar case study can give a novel insight into the
potential for vegetation encroachment and aggradation near the City of Fort Collins . The results from the
field-based studies contradict the claims made in the EIS Reports that aggradation and vegetation
encroachment are not prevalent near the City of Fort Collins and supply limited conditions eliminate risk .
The pre- and post-runoff vegetation photos study showed that the 2018 runoff event was not able to
cause significant mortality or removal of plant seedlings starting to establish on over twenty bar locations
near the City of Fort Collins . These results are concerning because the 2018 peak flow through the City
was above the baseline flushing flow values selected in the FFR (2017 ) , therefore the current EIS flushing
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flow values clearly are not representative of channel maintenance flows required by the City to maintain
current flood risk standards .
The point bar case study used to understand the connection of vegetation encroachment and aggradation
near the City of Fort Collins challenges the claim made in the EIS reports regarding supply limited
conditions . The investigation of this bar showed a clear pattern of vegetation encroachment from 1999 to
present and up to 4' of deposition that occurred on this bar during that time frame . This is clear evidence
that aggradation and vegetation encroachment is occurring near the City of Fort Collins . This also
contradicts the claims that the Poudre River upstream of 1 -25 is not at risk of increased aggradation
because it is supply limited . It is important to note that the deposition seen on the bar is not the result of a
singular event ( i . e . , the 2013 floods ) . The photograph in Figure 18 shows that around 1 . 5' of extra
deposition occurred on the bar from the 2013 event. Therefore , up to 4' of deposition observed in 2018 is
strong evidence that there was available supply in the years following 2013 .
These field studies provide strong evidence that aggradation and vegetation encroachment is occurring
near the City of Fort Collins and the supply is not limiting this from occurring nearly as much as the EIS
reports conclude . The results for the preferred alternative from SDEIS Technical Report (2014 ) shown in
Figure 2 state there will be a larger decrease in sediment transport potential upstream than downstream
of I -25 , but there will be less to no impact because of supply limited conditions . The evidence from the
field studies suggest that this is not true .
Section 6—Conclusions
The EIS reports were reviewed to understand the assumptions , methods , analyses , and conclusions
reached regarding the current conditions of the Poudre River and the potential impacts of NISP
operations . In response to deficiencies in those reports , additional analyses , including hydraulic
simulations , flow competence and capacity calculations , historic data review, and field observations and
measurements were subsequently performed to gain a better understanding of how NISP might impact
resiliency and flood risk on the Poudre River.
The geomorphic analysis methods and interpretation of results have been variable and at time erratic.
The physical basis for the selected geomorphology methods and conclusions are not supported by the
best available science and data.
Of primary concern are the reliance on the assumption of the Poudre as being supply-limited and the
assumptions inherent to the selected definition of flushing . The results of our analyses show that the
Poudre is susceptible to episodic inputs of sediment and that the reductions in transport capacity
calculated will exacerbate the channel contraction currently observed in the Fort Collins reaches . The EIS
documents appear to reach the same conclusion yet disregard the results of their own analyses despite
having not performed any analysis to verify the classification of the channel as supply limited .
Determinations on whether a channel is supply limited or capacity limited fundamentally requires a
comparison between sediment supply and transport capacity ( Montgomery & Buffington 1997) . Other
than qualitatively, sediment supply has not been assessed . Based on ( Montgomery & Buffington 1997 )
the Poudre would be classified ( both above and below 1 -25 ) as capacity limited , but anthropogenic
influences obscure direct application . Evidence from our field investigations , showing vegetation
encroachment and aggradation , suggest that while historic channel forms have been strongly influenced
by development, the Poudre likely remains capacity limited above 1 -25 . Sediment supply, however, is now
more episodic in nature (associated with moderate flows ) . While downstream of 1 -25 there may be a
stronger physical signature , NISP will reduce the transport capacity of the reaches in town to levels below
those now experienced downstream of 1 -25 , thus exacerbating the channel aggradation currently
observed in reaches through town . This key conclusion from the EIS process is disregarded based on an
assertion of the channel being supply limited .
Furthermore , the definition of flushing changed to rely on a flow associated with Q2 , which the literature
has shown to indicative of the channel forming flow, in some rivers . As discussed above , this assumption
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applies to coarse-grained , equilibrium channels , and the Poudre is not one of those channels .
Additionally, this approach is based on an average condition , but observations from recent years suggest
that non-average conditions have the potential to significantly alter the condition of the Poudre .
Developing resiliency in the river corridor is a primary concern for the City and our results suggest that
moderate floods , in addition to higher floods , give the system its resiliency.
The modeling methods and assumptions used in the EIS are inadequate to predict and evaluate the
impacts of NISP on flood risk. We believe the preferred alternative will increase sediment deposition and
woody vegetation establishment in the river channel, despite the proposed mitigation plan. This will
potentially increase flood levels and risks to private property and critical infrastructure (e. g. , bridges)
along the river corridor.
Uncertainty in the shear stress calculations and comparison with the tracer rock observations suggest
that capacity and competence calculations , performed with 1 D model hydraulics , are alone insufficient for
the determination of flushing flows . Other lines of evidence need to be considered along with the
analytical tools . It is apparent from our field investigations that the Poudre is gradually losing channel
capacity and the results of the EIS documents suggest NISP will exacerbate this behavior. That will
increase flood levels and risk to private property and infrastructure located in the floodplain .
There are multiple lines of evidence from our analyses (including historical and field evidence) that
suggest the proposed changes to river flows will reduce flood carrying capacity and simultaneously
degrade habitat. Ultimately, the City is likely going to be faced with increased costs and maintenance
requirements to sustain the current level of flood protection along the river corridor. The City's ability to
achieve its vision of a healthy and resilient river, will also be limited in perpetuity, as the selected
alternative and mitigation plan will substantially reduce the amount of time that flows meet critical
thresholds for preventing sediment build up and maintenance of channel capacity.
As discussed above , sweeping fines off the surface is not a sufficient flushing objective , nor is it based in
a realistic understanding of the channel bed . Without channel maintenance flows , short term changes in
boundary roughness will lead to reduced flow conveyance in the channel , channel straightening , and a
reduction in habitat diversity. As determined by the ERM , the channel will become more canal-like and
limited in its ability to handle disturbance events . The City will need to invest more heavily in maintenance
to avoid increased flood risk . The proposed mitigation measures are not realistic as conveyance will be
lost in locations where adjacent land is not available to be repurposed for flood mitigation .
Overall , our desktop- and field-based analyses ( including tracer rocks during an average runoff year and
vegetation analyses ) have shown that the sediment transport processes on the Poudre River may be
functioning more than the EIS reports suggest and have more sediment supply while simultaneously
having risk of continued vegetation encroachment and increased aggradation . Furthermore , field- based
results have rendered model results uncertain which has reduced reliability of the modeling approaches .
The EIS Reports rely heavily on modeling alone , but our results show that the tools in isolation are
insufficient to understand the questions being asked and must be tempered with field evidence . These
findings suggest that the predicted impacts of NISP operations on current conditions presented in the EIS
reports may be grossly underestimated .
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References
Anderson Consulting Engineers , Inc. 2013 Stream Morphology and Sediment Transport, Cache la Poudre
River Mainstem Baseline Report. NISP and HSWSPs Environmental Impact Statements .
Prepared for U . S . Army Corps of Engineers . March 9 .
Anderson Consulting Engineers , Inc. 2017a Northern Integrated Supply Project Final Environmental
Impact Statement assessment of Flushing Flows on the Cache la Poudre River. Prepared for
U . S . Army Corps of Engineers . March 9 .
Bunte , K. , and S . R . Abt (2001 ) . Sampling Surface and Subsurface Particle-size Distributions in Wadable
Gravel and Cobble Bed Streams for Analyses in Sediment Transport, Hydraulics , and Streambed
Monitoring . General Technical Report RMRS-GTR- 74; Fort Collins , CO : U . S . Department of
Agriculture , Forest Service , Rocky Mountain Research Station ; 428 p .
City of Fort Collins . 2014 . Ecological Response Model . Fort Collins , CO .
Coalition Poudre River Watershed . 2017 . Lower Poudre River Resiliency Plan . Fort Collins , CO .
Grand County Stream Management Plan ( GCSMP ) (2010) . Draft Report, Stream Management Plan ,
Phase 3 , Grand County, Colorado . Report and Appendices , Draft Report prepared for Grand
County, Colorado , August, 37 p . , URL : http ://co . grand . co . us/WRM/ Draft Report/d raft. htmI
including appendices .
Kondolf, G . M . , and P . R . Wilcock ( 1996 ) . The flushing flow problem : defining and evaluating objectives .
Water Resources Research 32 (8) : 2589-2599 , DOI : 10 . 1029/96W R00898 .
Milhous , R. T . (2000 ) . Numerical modeling of flushing flows in gravel-bed rivers . Pages 579— 608 ,
Chapter 25 in : Gravel-Bed Rivers in the Environment, P . C . Klingeman , R . L . Beschta ,
P . D . Komar, and J . B . Bradley ( Eds . ) , Water Resources Publications , LLC , Littleton , CO ,
832 p .
Milhous , R. T . (2003) . Reconnaissance — Level Application of Physical Habitat Simulation in the
Evaluation of Physical Habitat Limits in the Animas Basin , Colorado . U . S . Geological
Survey Open File Report 03-222 , available from the Fort Collins Science Center, Fort
Collins , CO , 16 p .
Montgomery, D and J . M . Buffington ( 1997) . Channel -reach morphology in mountain drainage basins .
Geological Society of America Bulletin 109 (5) : 596-611 .
Parker, G . (2008 ) . Transport of gravel and sediment mixtures . Chapter 3 ( Pages 165-251 ) in
Sedimentation Engineering : Theories , Measurements , Modeling , and Practice (ASCE Manuals
and Reports on Engineering Practice No. 110) , M . H . Garcia ( Ed . ) ; New York , NY: American
Society of Civil Engineers ; 1150 p . , DOI : 10 . 1061 /9780784408148 . ch03 .
Wilcock , P . R. ( 1998 ) . Sediment maintenance flows : feasibility and basis for prescription . Chapter 26
( Pages 609-638) in Gravel - Bed Rivers in the Environment, P . C . Klingeman , R . L . Beschta , P . D .
Komar, and J . B . Bradley ( Eds . ) ; Highlands Ranch , CO : Water Resources Publications , LLC .
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Wilcock , Peter; Pitlick , John ; Cui , Yantao (2009 ) . Sediment transport primer: estimating bed-material
transport in gravel-bed rivers . Gen . Tech . Rep . RMRS-GTR-226 . Fort Collins , CO : U . S .
Department of Agriculture , Forest Service , Rocky Mountain Research Station . 78 p .
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Appendix A
Long-Term Monitoring Study
With uncertainty remaining in the magnitude and scale of potential impacts from NISP on the Poudre
River' s ability to transport sediment, maintain flushing flows , and sustain current channel dimension and
flood conveyance it is important to establish a long-term monitoring plan to help inform potential adaptive
management decisions in the future . It has been stated in the FEIS that NISP will alter the capacity of the
Poudre River to move sediment which could potentially increase aggradation and vegetation
encroachment through the City. Furthermore , NISP will decrease the frequency and duration of flushing
flows necessary to remove fine sediment from interstitial spaces and maintain physical habitat for fishes
and aquatic insects . To better determine the impact of these altered flows as a result of NISP on the
Poudre River a multiple lines of evidence approach should be taken within the long-term monitoring effort.
Physical data should be collected annually post-runoff which will provide valuable information for baseline
data pre- NISP , during the filling period of the Glade Reservoir, and potential post-NISP impacts . It is
recommended to establish study sites as soon as possible to be able to start collecting pre- NISP baseline
data . Key evidence used to estimate changes in sediment transport, vegetation encroachment, and
flushing flows will include :
1 . Aggradation
a . Annual survey of permanent cross-sections and longitudinal profile
b . Photo points
c . Highly detailed field observations
2 . Vegetation Encroachment
a . Annual survey of permanent cross-sections marking vegetation line
b . Photo points
c . Highly detailed field observations
3 . Flushing Flows
a . Tracerrocks
b . Pebble counts
c . Percent fines/coarse/algae
d . Percent embeddedness
e . Photo points
f. Highly detailed field observations
g . Magnitudes and durations of pre- vs . post- NISP peak flows as measured by U . S .
Geological Survey ( USGS)
Twenty-six sites have been selected along the Poudre River from Lions Park downstream to I -25 for
permanent cross-sections to be established . Six of these sites were part of the tracer rock study and
already have rebar installed . Eighteen of the sites are located at riffles features and an additional eight
are located in run sections . Approximate site locations are presented in Google Earth files ( . kmz)
delivered separately to the City of Fort Collins . Final cross-section locations at each site will be decided in
the field and will be ideally placed through the middle of riffles and runs or as deemed most
representative of the geomorphic unit that is being surveyed . A longitudinal profile should also be
surveyed starting at the next riffle crest upstream of the cross-section being surveyed and continue down
to the next riffle crest downstream of the cross-section . The twenty-six sites were chosen to represent the
range of physical , geomorphological , and hydrological conditions occurring in the Poudre River through
Fort Collins . In addition to the permanent cross-sections , the 27 bars that were visually assessed for
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aggradation and vegetation encroachment as part of the current study should also be repeated annually.
Three new bars are also being added to the previous 27 making a total of 30 bars to be visually assessed
through the study area .
A systematic point grid frame method would ideally be used in combination with a gravelometer to collect
substrate data at each site ( Bunte and Abt, 2001 ) . Greater than 300 substrate observations should be
taken along the cross-section spanning the entire bankfull channel . An additional 300 observations of
presence of fines , algae , and coarse material should also be taken along the cross-section with the point
grid frame in combination with a viewing bucket . Finally, embeddedness data should be collected by
measuring the average depth of the largest substrate above and below the layer of fine material
surrounding the rock . Fifteen embeddedness measurements should be taken equidistance along the
cross-section . Tracer rock , photo point, and field observations should follow methods presented
previously in this report.
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Parameter Monitoring Questions Data to be collected What we learn Sampling
Timeline
30 bars will be visually assessed Whether aggradation is
• for aggradation with highly occurring at an increased rate
Is aggradation detailed observations being post-NISP and if there is a
occurring at an documented bio-feedback loop with
vegetation encroachment
Aggradation increased rate post- Photo points at bars , bridges ,
NISP? and upstream of diversion dams occurring . Furthermore , is
Cross-section and longitudinal aggradation leading to a loss
• survey through 12 of the 30 of flood conveyance through
point bars the City.
• 30 bars will be visually assessed
Is vegetation for vegetation encroachment Whether vegetation
encroachment with highly detailed observations encroachment is occurring at
Vegetation occurring at an being documented an increased rate post NISP
Encroachment increased rate post- Y Photo points at bars and if this is leading to a loss Annually post-
NISP? Cross-sectional survey through of flood conveyance through runoff
12 of the 30 bars marking the the City.
vegetation line
• 26 cross-sections
o Tracer rocks
o Pebble counts (300
Are decreases in peak samples )
flow magnitude and o Percent fines/coarse/algae If altered flows from NISP are
Flushing duration from NISP (300 observations ) decreasing the frequency and
Flows leading to increased o Percent embeddedness ( 15 duration of flushing flows to a
riffle/run measurements) point where riffle/run habitat is
o Photo points becoming more embedded .
embeddedness? o Highly detailed field
observations