HomeMy WebLinkAboutCOUNCIL - AGENDA ITEM - 01/05/2016 - ITEMS RELATING TO REVISIONS OF CERTAIN DETENTION AAgenda Item 10
Item # 10 Page 1
AGENDA ITEM SUMMARY January 5, 2016
City Council
STAFF
Basil Hamdan, Civil Engineer II
Ken Sampley, Stormwater/Floodplain Program Mgr
Kevin Gertig, Utilities Executive Director
Jon Haukaas, Water Engr Field Operations Mgr
SUBJECT
Items Relating to Revisions of Certain Detention and Development Policies in the Fort Collins Stormwater
Criteria Manual.
EXECUTIVE SUMMARY
A. First Reading of Ordinance No. 006, 2016, Amending Chapter 26 of the Code of the City of Fort Collins
and the Fort Collins Stormwater Criteria Manual to Modify the Criteria for Underground Detention Systems.
B. First Reading of Ordinance No. 007, 2016, Amending Chapter 26 of the Code of the City of Fort Collins
and the Fort Collins Stormwater Criteria Manual to Modify Provisions Implementing Low Impact
Development Principles.
The purpose of this item is to formally adopt two updates to the Stormwater Criteria Manual. Ordinance No.
006, 2016, updates the criteria that govern when, where, and to what extent it is appropriate to design and
construct underground stormwater detention systems in the City of Fort Collins. Ordinance No.007, 2016,
updates the current Low Impact Development (LID) criteria. The two policies are consistent with sustainability
goals for the City of Fort Collins which center on three themes: innovate, sustain and connect. The adoption of
these updated policies will allow for more efficient use of space, thus allowing the City to meet its sustainability
goals, provide innovative design flexibility for new development that will enhance community affordability and
livability, and allow a more compact development pattern in Fort Collins enhancing connectivity and reducing
sprawl.
STAFF RECOMMENDATION
Staff recommends adoption of the Ordinances on First Reading.
BACKGROUND / DISCUSSION
Updated Underground Detention Policy
The City of Fort Collins adopted an updated Stormwater Criteria Manual (Manual) on December 20, 2011 (Ord.
No. 174, 2011), adopting by reference certain portions of the Urban Storm Drainage Criteria Manual, 2001
Edition published by the Denver Urban Drainage and Flood Control District, a widely applied and referenced
set of storm water-related standards along with a separately codified set of extensive amendments
customizing the standards, policies and practices of the Urban Drainage Manual for use in Fort Collins (“Fort
Collins Amendments”), all as set forth in City Code Section 26-500. Unless an amendment to the Manual is a
purely technical revision in nature, modification of the Fort Collins Amendments must be approved by City
Council. The Utilities Executive Director may otherwise approve limited technical revisions to the Manual.
Agenda Item 10
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Currently, under the City Code and the Manual, underground detention is only allowed at the discretion of the
Utilities Executive Director as an exception, with such approval subject to separate construction, operation,
and maintenance conditions. The City can advance the interest of its Stormwater Utility customers and
facilitate development in the community by adjusting the current underground detention policy in the Manual to
recognize an explicit set of system criteria that ensure construction and maintenance of such systems are
conducted in a consistent, safe, maintainable, and effective manner.
Purpose and Benefits of Underground Detention
The need to revise the policy involving underground detention facilities arose in conjunction with adoption of
the Low Impact Development (LID) Policy by the City in March 2013. The LID policy is aimed at encouraging
sustainable practices in stormwater management. LID practices, sometimes also referred to as “Green
Infrastructure” (GI), generally encourage infiltration of runoff to reduce volume and improve water quality.
LID or GI is a comprehensive land planning and engineering design approach to managing stormwater runoff
with a goal of replicating natural systems that existed prior to development. LID techniques treat and control
stormwater at its source, thereby reducing the need for large structures or end-of-pipe treatment.
Since LID practices encourage infiltration systems, prohibition of underground detention is contrary to that
goal, which has led to the current proposed update to the underground detention policy.
Proposed Underground Detention Policy
The proposed underground detention policy is intended for use only where surface detention is deemed
impracticable. When applicable, the proposed policy allows underground detention under the following
conditions:
It must be safe, i.e., it must not cause flooding to nearby public or private property
It must be efficient, i.e., it must provide effective water quality treatment.
It must be accompanied by an approved Standard Operations Procedures (SOPs) manual that will
ensure appropriate maintenance practices are followed by all owners of the facility
It must have a gravity driven outfall system
It must be relatively small in volume, i.e., not exceed 1 acre-foot
It must preserve downstream water rights
It must be inspected regularly
It must be designed with maintenance in mind
It must comply with all other technical criteria as specified
Updated Policy Development Process
The underground detention policy was developed after extensive consultation in coordination with practicing
stormwater engineering and development professionals in the City of Fort Collins. The City’s Water Board
reviewed the proposed policy at its regular meeting on November 19, 2015, and voted unanimously to
recommend City Council adopt the updated policy, including additional technical criteria specified by the
Board. (Attachment 1).
Updated Low Impact Development Criteria
As discussed above, an element of the integrated stormwater management system established under the Fort
Collins Stormwater Criterial Manual is the application of LID criteria to facilitate distributed and landscaping-
based stormwater runoff management. In conjunction with the updated underground detention policy, staff has
recommended the LID criteria set forth in Section 3.1 of Volume 3, Chapter 2, Paragraph K of the Fort Collins
Amendments be clarified as to when they are applied.
Agenda Item 10
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The focus of the updated criteria is to clarify that LID techniques need to be applied on any newly developed or
redeveloped site and any modification of impervious area on a previously developed site for which a
development construction permit is required under City codes and regulations.
Background
Fort Collins Utilities staff has met with the Chamber of Commerce and representatives from the development
community and engineering consultants to consider updates to the LID Policy in response to concerns raised
to City Council and the Chamber of Commerce in the last several months. Meeting summary notes from the
Chamber presentation are appended as Attachment 3. Staff also engaged community roundtables on
November 18 and December 16, 2015, after which further revisions were made to the proposed LID Policy
update (see Roundtable summary memo, Attachment 2). The main concern presented to staff during these
engagements has been the high initial cost for the permeable pavement component of the existing policy.
The current LID Policy was adopted in February 2013 and has been in effect since March 1, 2013. It is
outlined in Volume 3 Chapter 3 of the Fort Collins’ Stormwater Criteria Manual, as reflected in Attachment 4.
The current policy states: at least fifty percent (50%) of a site must be treated by an LID technique when a
minimum of twenty-five percent (25%) of the driving or parking area in parking lots is constructed with a
permeable pavement system that functions as an LID technique. An alternative compliance clause is also
included that allows variation from these standards when these conditions cannot be met due physical site
constraints, and an equal or better alternative is provided.
When the policy was first adopted in 2013, initial cost issues were considered; however, the decision to
proceed with the current regulations as stated in the policy were driven by life cycle costs analysis and
considerations which show that over the life cycle of the project the LID treatment type design tends to be
more economical than conventional solutions.
Proposed Policy
In response to development concerns, the City is proposing a revision to the LID criteria providing options that
offer a wider range of design solutions to better fit the type of development under consideration (i.e.
“greenfield” versus highly-developed infill).
The proposed policy will ensure the technologies used in the treatment of proposed developments are still in
concert with the City’s overall sustainability goals. Under the updated LID policy, three options would be
allowed:
Under the first option the required amount of LID treatment is increased from 50 to 75% of the new
development and redevelopment area and removes the permeable pavement requirement when a
75% LID treatment level is provided.
The second option allows the amount of LID treatment to remain at the currently required 50% level,
provided a permeable pavement system is constructed on at least 25% of the drivable pavement area
in any development. This option was added to encourage this type of technology when space
constraints do not allow for a higher level of LID treatment and encourages the dual use of parking lots
as a usable development area as well as a water quality treatment component. It is also based on
studies that show that permeable pavement in general provides a higher level of pollutant removal
rates.
The third option maintains the alternative compliance option that allows the Utilities Executive Director
to vary some of the requirements when site engineering constraints do not allow the for the
construction of LID techniques as prescribed in the first two options. This allows for a staff level
interpretation of the LID regulations, as long as an “equal or better” level of water quality treatment is
deemed to be achieved and increases the level of flexibility in how that level is accomplished. This is
an important consideration when designing an LID treatment system because site conditions often
dictate what can be constructed based on constraints unique to each site.
Agenda Item 10
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This LID Policy update taken in conjunction with the Underground Detention Policy update will provide an
incentive for developers to use pervious pavement system as a water quality treatment option when land costs
are a major consideration.
BOARD / COMMISSION RECOMMENDATION
At its regular November 19, 2015 meeting, the Water Board considered staff’s recommendation regarding the
underground detention policy, and voted unanimously to recommend City Council adopt the updated policy,
including additional technical criteria specified by the Board. (Attachment 1).
At its December 17, 2015 meeting, the Water Board considered staff’s recommendation regarding the LID
updates and unanimously voted to recommend Council adopt the updated LID criteria for the Fort Collins
Stormwater Criterial Manual, with some suggested language changes. The Water Board’s suggested changes
and clarifications have been incorporated into the proposed ordinance language.
PUBLIC OUTREACH
Staff has met with Councilmembers, the Fort Collins Chamber of Commerce and representatives of the
development industry and design professionals (Attachment 3). A LID Policy Roundtable meeting was held on
November 18, 2015. Staff listened to concerns from the Chamber of Commerce on December 4, 2015 and
has responded to the issues that were brought up at that meeting.
After meeting with Roundtable participants again on December 16, 2015, staff made further revisions to the
LID Policy update based on those discussions (Attachment 2). Staff presented the revised LID policy for
Water Board review and discussion on December 17, 2015, at which time the Board recommended Council
approval of the revised policy. Staff intends to continue discussions with key stakeholders in the upcoming
months to work on further updates to the policy, if needed.
ATTACHMENTS
1. Water Board minutes, November 19, 2015 (draft) (PDF)
2. LID Policy Update Roundtable Discussion, November 18, 2015 (PDF)
3. Chamber of Commerce Discussion notes, December 4, 2015 (PDF)
4. Current LID Policy (PDF)
5. Water Board Minutes, December 17, 2015 (draft) (PDF)
Excerpt from Unapproved Water Board Minutes – November 19, 2015
Underground Detention Policy Update
(Attachments available upon request)
Stormwater Quality Engineer Basil Hamdan of the Environmental Regulatory Affairs Division
gave an overview of underground detention policies in the City. Currently, underground
detention is only allowed on an exception basis and the Utilities Executive Director must
approve all requests. Staff intends to streamline the approval process by amending City policy to
adopt criteria that mirrors the City’s sustainability goals.
The proposed policy update intends to increase storage below grade through the adoption of
criteria that grants easier approval to design and construction of underground stormwater
detention facilities in the City of Fort Collins. As described in the presentation, underground
detention allows increase in detention of onsite runoff, without tying up additional surface area.
The intent of the underground detention policy is targeted toward smaller facilities, and should
not be the exclusive method of stormwater control on larger projects.
To be effective, underground detention structures must be maintained in accordance with
developed standard operating procedures. In order to address the maintenance requirements, the
new policy will require facilities with underground detention structures to inspect their own
facilities twice per year. The City will visually inspect all structures approximately every two
years for proper operation. Staff feels this is an appropriate mechanism to control stormwater and
wants to place into City Code.
Highlights of the Discussion
A board member sought clarification on the types of impervious areas that will be
targeted with the policy update. Mr. Hamdan replied that it will generally be parking
areas and other areas that must maximize the available surface area, without storing water
above ground.
A board member inquired about the maintenance required with underground detention
structures. Mr. Hamdan indicated that maintenance and operations procedures
recommend cleaning and vacuuming on a six-month schedule that will be required in the
new regulations.
A board member inquired if the life-cycle of underground storage structures were less
than other above ground structures. It was communicated that the stability and durability
of the systems is high, which allows long life spans of the structures.
Freezing and thawing is not an issue due to the design of the system and the associated
porous nature of the structure and air movement.
A board member identified a concern regarding potential of system degradation due to
excessive use. Staff emphasized the importance of maintenance and reiterated that
maintenance standards will be built into the regulations and must be followed to ensure
an effective structure.
Approximately every two years, Utilities staff will conduct a visual inspection to evaluate
the effectiveness of the drainage structure. In addition, as part of the standard operating
procedures, the facility must inspect their own facilities twice per year.
There have been 20 to 30 approvals of underground storage structures in recent history.
ATTACHMENT 1
A board member sought assurances that any new policies associated with underground
detention structures will be vetted through the Water Board and City Council. As
described by Mr. Hamdan, all policy changes require Water Board and City Council
approval. Future technical aspects can be changed administratively through Utilities staff
approval.
A board member inquired if mosquitoes were a concern with underground detention
structures. Due to the 72-hour detention maximum, and lack of standing water,
mosquitoes are not an issue.
A board member recommended that any violations requiring corrective measures to a
structure be consistent with City code. Previous corrective measures with a time
stipulation have led to discussion among the Water Board in the past.
A board member recommended that the overarching guidance regarding underground
storage structures be presented with the materials for ease of understanding.
Board Member Brian Brown moved that the Water Board recommend City Council
approve the Underground Detention Criteria Policy amendment to the Stormwater
Criteria Manual.
Board Member Phyllis Ortman seconded the motion. There was no discussion.
Vote on the motion: The motion passed unanimously, 8-0.
ATTACHMENT 2
Chamber Dec. 4
LIDs
x What are the challenges costs, such as soil replacement present both pros and cons
x Being paired with streetscape standards lids got lost with the other efforts recommend a more
singular focus with LID is it part of streetscape thus paired with other sustainable efforts and did
not receive the focus necessary
x Pigeon hole terminable pavers, other options allow permeability why not allow other types of
terminable.
x Why isn’t the city putting in permeable pavers on roadways as well?
x Brower county some major arterials have pavers at intersections.
x Why pavers in urban densely populated areas only – up for discussion
x What is life span of pavers, such as spaulding assume same problems in parking lots
x What is average life of concrete is about 10 years; pavers parking lot lifespan 25 years with
maintenance
x Every 6 months to vacuum for maintenance of pavers
x Spreadsheet that shows costs side by side to LLAC
x Cost to use machine on square foot basis about $500 twice a year with vehicle; City will allow
using machine
x Does it remove gravel or just dirt; mostly just dirt
x Rule has passed any thought given to incentivizing, would a developer want to put in versus
detention was there a reason we had to make them a law? Are they not that good so we
mandated.
x Changing regulations to have more flexibility does not have to be technology developers
provided more flexibility. Convening panel of experts to discuss options to modify LIDs.
Relaxing regulations when in economic benefit. No money other breaks within development
city does not need to pay for projects just more other benefits in other aspects of the
development
x Basic reason is water quality what is difference of quality of output using non-permeable versus
requiring pavers significant of water does it matter if soaks in immediately versus retention
improvement from 15% increase benefit but increasing cost 2 times
x Slide 7 where are the mandatory percentages come from? question the percentage with less
than 50% mandate for the benefit be flexible with percentages going forward to meet water
quality need
x System works better with soil types so when discuss paver’s costs look at what other treatments
must be done to soils additional costs preparing for pavers. Filter water before SW system
treating on-site versus at treatment facility.
x Whether cheaper to treat in regional versus individual development
x CSU monitoring copy of report email to ANN
ATTACHMENT 3
x Cleaning every six months how regulated new City employee – there are three year inspections
performed from employee. Oil spills, containments dropped or leaked monitoring direct to rip
out and redo
x Further opening dialogue of next steps adjust as needed what is present and future right sizing
regulations
x Old town already developed already maximized the impermeable surface, why reduce demand
if impermeable surface is maximized?
x What are the next steps for continued feedback from public want to be part of solutions –
guideline booklet/toolkit suggestions or requirements your option to how to meet.
performance based achieve results of better water quality/permeability
x Performance based are guidelines include specific tactics to achieve per existing regulations
x If considering relaxing 25% targets how handle current in cue for approval or under construction
in March, April, May – enforce City Code today. If approved in February project in April redesign
to meet modified City Code if have not resubmit as a minor amendment. Revise construction as
a minor amendment If approved plan start processing amendment soon but may not pass
x Contractor south Florida pavers issues image not interlocking pavers; interlocking pavers butt
abut against each other seems to be a lot less O&M moving forward pavers have O&M last piece
soil conditions vary quite bit. Soil test to engineering firm no run off to adjoining properties. Do
not broad stroke this situation
x Focus on outcome
x Open to make comments at Water Board
x The cost of doing this solution raises the initial cost then raises the permit fee consider fee to
incentive solution from clients and developers
x Charge costs water costs if systems not maintained SW runoff not happening should be fairly
easy to track LID technology ahead of maintenance
Volume 3, Chapter-3 - Calculating the WQCV and Volume Reduction
(1) Section 1.0 is amended to read as follows:
1.0 Introduction
This chapter presents the hydrologic basis and calculations for the Water Quality Capture Volume
(“WQCV”) and discusses the benefits of attenuating this volume. This chapter also describes various
methods for quantifying volume reduction when using LID practices. Use of these methods should begin
during the planning phase for preliminary sizing and development of the site layout. The calculations and
procedures in this chapter allow the engineer to determine effective impervious area, calculate the
WQCV, and more accurately quantify potential volume reduction benefits of BMPs.
(2) Section 2.4 is deleted in its entirety.
(3) A new Section 3.1 is added, to read as follows:
3.1 Low Impact Development (LID) Criteria
Once the WQCV has been calculated in accordance with the specifications of Section 3.0 of this chapter
the total WQCV must be treated by one or more of the methods outlined in Volume 3, Chapter 4,
Treatment BMPs. In addition, the requirements set forth below in this section, referred to as Low Impact
Development (LID) Criteria must be met. For the purposes of this section, the LID methods and
techniques described in Volume 3, Chapter 1, Section 4.1, Runoff Reduction Practices, together with any
methods or techniques determined by the Executive Director to be functionally equivalent, shall be
considered LID techniques.
(a) The LID Criteria are as follows:
(1) No less than fifty percent (50%) of any newly added impervious area must be treated using
one or a combination of LID techniques; and
(2) No less than twenty five percent (25%) of any newly added pavement areas must be treated
using a permeable pavement technology that is considered an LID technique.
(b) If, in the judgment of the Executive Director, one or more requirements of this section cannot be
met due to site engineering constraints, then a design alternative will be allowed, provided that
the design results in equal or better stormwater quality than would compliance with the otherwise
applicable requirement.
ATTACHMENT 4
From Unapproved Draft Minutes – December 17, 2015 Water Board
From Unapproved Draft Minutes – December 17, 2015 Water Board
Low-Impact Development (LID) Policy Update
(Attachments available upon request)
Stormwater Quality Engineer Basil Hamden and Water Utilities Engineering Manager Ken
Sampley presented a summary of the Low Impact Development (LID) Policy Update. LID is
green infrastructure that helps maintain historic flows and filter pollutants. The City plan calls
for a specific prescriptive approach that should be updated. The new recommendations come
from a data-driven approach that involved multiple pilot projects. The main benefits are more
efficient use of space, improved water quality, resiliency, improved groundwater recharge,
reduced energy demand, and enhanced property values and aesthetics.
Key Goals
x Provide a more flexible performance measures instead of just technology restrictions
x Respond to initial cost issues
x Clarify terminology
Current Key Regulations
x Minimum of 50% of new impervious surfaces must be LID-type device or technology
and 25% must be treated with pervious pavement
x Or, new development must meet equal or better LID standard as judged by staff
(Alternative Compliance)
Key Changes to Regulations
(See Executive Summary)
x No less than 75% of new or redeveloped area impervious surfaces must be LID-type device
or technology
x Or, No less than 50% of new or redeveloped area impervious surfaces must be LID-type
device or technology when permeable pavers are 25% of drivable land cover
City Council adoption is expected in January 2016 with continued outreach throughout the year.
Discussion Highlights
x A board member suggested using “at least as much as” “instead of “no less than.”
x A board member suggested making these codes more accessible.
x A board member expressed concern that a small driveway using pavers will reduce the
LID requirements from 75% to 50% even though the pavers will do very little. This may
be a loophole for developers.
ATTACHMENT 5
From Unapproved Draft Minutes – December 17, 2015 Water Board
x A board member suggested changing “private development property.”
x Water Engineering Field Operations Manager Jon Haukaas expressed the idea that this is
a policy, and not a bright-line rule for each case, thus it contains additional flexibility and
broadness.
Board Member Brian Brown moved that the Water Board recommends that Council
approve an update to the low impact development (LID) policy to allow more flexibility in
how the LID criteria can be met in accordance with Attachment Two and amended per the
Water Board discussion.
Board Member Kent Bruxvoort seconded the motion.
Vote on the motion: It passed unanimously, 11-0.
ORDINANCE NO. 006, 2016
OF THE COUNCIL OF THE CITY OF FORT COLLINS
AMENDING CHAPTER 26 OF THE CODE OF THE CITY OF FORT COLLINS
AND THE FORT COLLINS STORMWATER CRITERIA MANUAL
TO MODIFY THE CRITERIA FOR UNDERGROUND DETENTION SYSTEMS
WHEREAS, on December 20, 2011, the City Council adopted Ordinance No. 174, 2011,
which amended certain sections of Chapter 26 of the City Code and adopted a set of technical
criteria governing the design and performance of stormwater improvements and related practices
by adopting by reference certain portions of the Urban Drainage and Flood Control District
(“UDFCD”) Criteria Manual, 2001 Edition, published by the Denver Urban Drainage and Flood
Control District, as modified by the Fort Collins Amendments, also adopted by Ordinance No.
174, together referred to and codified as the Fort Collins Stormwater Criteria Manual (the
“Manual”); and
WHEREAS, the Manual, including the separately codified Fort Collins Amendments, has
been modified from time to time by limited technical revisions adopted administratively by the
Utilities Executive Director and filed with the City Clerk as authorized by in City Code Section
26-500; and
WHEREAS, as adopted with the Fort Collins Amendments, the Manual currently
prohibits underground detention as a stormwater management practice, except upon special
review and exception granted at the discretion of the Utilities Executive Director; and
WHEREAS, as part of recent reviews of the City's Municipal Separate Stormwater
System, and in an effort to align the Manual with Low Impact Development policies adopted by
City Council in March 2013, City staff has developed a new amendment to the Manual that
establishes detailed underground detention system criteria (“UDS amendment”); and
WHEREAS, the purpose of the UDS amendment is to facilitate appropriate use of
underground stormwater detention as a best management practice, ensuring predictable, safe,
maintainable, and effective construction and maintenance of such systems; and
WHEREAS, the UDS amendment was presented to the Water Board at its November 18,
2015, regular meeting, and the Board voted unanimously to recommend City Council adoption
of the amendment; and
WHEREAS, the City Council finds that amending the Manual to facilitate predictable
and appropriate construction and maintenance of underground stormwater detention systems,
based on documented review criteria, benefits the City’s citizens and Stormwater Utility
customers by creating a regular process to accommodate such systems.
NOW, THEREFORE, BE IT ORDAINED BY THE COUNCIL OF THE CITY OF
FORT COLLINS as follows:
Section 1. That the City Council hereby makes and adopts the determinations and
findings set forth in recitals above.
Section 2. That Paragraph 4.16 of Volume 2, Chapter 10, Section H of the Fort
Collins Amendments, which is a component of the Fort Collins Stormwater Criteria Manual, is
hereby amended to read as follows:
4.16 Underground Detention
4.16.1 Policy
The use of structural underground detention is generally discouraged, except when the criteria set
forth in 4.16.2 are satisfied. Underground BMPs should not be considered for detention storage
when surface-based systems are practicable. For most areas of new urban development or
significant redevelopment, it is feasible and desirable to provide the required storage on the
surface. The responsible partysystem owner must demonstrate that surface-based detention or
other BMPs have been thoroughly evaluated and found to be infeasible before an underground
system is proposed. In the event where If an underground storage system is proposed, a system
owner must seek approval of such a system by written request for approval of such a system
must be submitted by the Owner describing the system in detailing. Tthe Utilities Executive
Director, who may approve such a system upon a determination that the requirements of this
4.16.2 provision have been met are satisfied and that no adverse impacts are expected to result
from the proposed system. For any underground detention, runoff must flow through a pre-
treatment facility before it enters the underground detention facility. A standard operating
procedures manual must be submitted and approved by the City for all underground facilities. A
final copy of the approved standard operating procedures manual must be provided to City and
must be maintained on-site by the entity responsible for the facility maintenance. Annual reports
must also be prepared and submitted to the City discussing the results of the maintenance
program (i.e. inspection dates, inspection frequency, volume loss due to sedimentation,
corrective actions taken, etc.)
4.16.2 Underground Detention Criteria.
The purpose of this subsection is to set forth technical criteria to be utilized for the use of
underground stormwater detention as a structural BMP to meet water quality and/or
stormwater runoff detention requirements.
(a) All systems.
Any proposed underground stormwater detention system, including gravel
reservoirs in porous interlocking concrete pavement (PICP) systems and
chambers or pipes, shall satisfy the following design and operating criteria:
1. The system owner shall provide to the City a Standard Operating
Procedures (SOPs) Manual detailing the operation and maintenance of the
proposed system. The SOPs Manual must comply with approved and
updated operational and maintenance procedures maintained by the City
for different types of underground detention systems. The SOPs Manual
must be submitted to and approved in written form by the Utilities
Executive Director prior to system approval and operation. A final copy of
the approved SOPs Manual must be maintained on-site by the party
responsible for facility maintenance. Annual reports must be prepared and
submitted to the City detailing the results of the maintenance program (i.e.
inspection dates, inspection frequency, volume loss due to sedimentation,
corrective actions taken, etc.);
2. Runoff must flow through a pre-treatment facility before it enters the
underground detention system;
3. A gravity outfall is required at the invert, i.e. lowest point, of the
underground detention system;
4. An observation well is required at the downstream end with a perforated
stand pipe, as well as a redundant overflow inlet located in a sump
condition. The redundant inlet must be designed with pre-sedimentation
control at the upstream end of the inlet;
5. The water table level must be documented to be at least one foot (1’)
below reservoir bottom during the high groundwater period of the calendar
year;
6. Where underdrain drainage systems are needed, due to underlying soil
conditions, the underdrain pipe diameter shall be at least eight inches (8”).
Underdrain cleanouts are required at all changes in direction or elevation
locations. If the minimum underdrain size (8”) results in a release rate
larger than allowed under this Manual, a restrictor plate must be added at
the point of outflow;
7. Potential lateral movement of detained storage water outside the limits of
the detention storage reservoir must be controlled, accounted and designed
for in a manner that ensures the structural integrity of adjacent structures
and infrastructure;
8. Infiltration testing must be performed during installation of open
bottom/infiltrating systems, after excavation is complete and before rock
placement in reservoir. These results must be submitted to the City and
approval obtained before commencement of construction activities on the
underground detention facility(ies). If the underground detention reservoir
is intended to allow for infiltration, the bottom of the reservoir must be
protected during construction to minimize compaction;
9. Annual visual inspection is required for all underground detention
systems. Documentation verifying inspection and performance must be
provided to the City within four (4) weeks after completion of annual
inspection. These inspection reports must be filed and available at the City
of Fort Collins Utilities office;
10. The underground detention system owner must submit for review a deed
restriction on the affected real property, incorporating the SOPs and
penalties specified for lack of performance. SOPs must be included in the
site’s Development Agreement, as well as in the deed restriction, subject
to review by the City Attorney’s Office. The deed restriction must
provide for the continued, long term operation and maintenance of the
underground detention system by subsequent owners of the affected
property and must be fully executed by the owners of the affected property
and recorded prior to system approval and operation; and
11. The deed restriction must also provide that if the City deems that the
underground detention system is not being maintained in accordance with
the SOPs specified in the deed restriction, and the system owner has been
given written notice and at least ten (10) days to cure and has not done so,
the City shall have the right of entry to the property in order to maintain
the system. The City may then charge the owner the time and material
costs incurred by the City to take corrective action and maintain the
system, in addition to any administrative costs incurred by the City.
(b) Detention reservoirs located in gravel void spaces of PICP systems.
In addition to the criteria set forth in 4.16.2 (a), the following additional criteria
apply to any Porous Interlocking Concrete Pavement (PICP) system with a gravel
layer void space:
1. The maximum water quantity detention volume allowed in the subsurface
void space is the greater of 0.2 acre-feet or 20% of the total water quantity
and water quality detention required. The maximum total detention storage
volume to be accounted for in the void space of gravel reservoirs shall be
less than 1.0 acre-foot. Additional storage volume is allowed in chambers
or pipes or a combination of all the system methods;
2. The material specified in the reservoir storage layer must comply with
ASTM Number 2 specifications for rock aggregate, or an alternate
approved in writing by the Utilities Executive Director. A 30% ratio for
available storage volume in the reservoir layer must be used in volume
calculations in order to account for potential sedimentation;
3. A minimum 13,500 pound-force vibratory plate compactor with a
compaction indicator and/or a minimum 10-ton vibratory roller must be
used to compact the system;
4. A PICP parking lot surface must be designed with a minimum 0.5% slope.
All systems must be designed to account for volume detained based on the
physical site characteristics and the ability of the system to intercept that
volume; and
5. Maintenance vacuuming must be performed in accordance with the
approved SOPs for the system. Any infiltration test on the system must be
done in accordance with ASTM C1781. Surface infiltration testing
locations must be indicated on a site map provided to the City pursuant to
Section 4.16. If testing shows an average infiltration rate in excess of one
hundred inches per hour (100”/hr.), vacuuming may occur at six month
intervals. In no instance shall a system be vacuumed less than once each
calendar year.
(c) Detention storage in chambers or pipes.
In addition to the criteria set forth in 4.16.2 (a), the following additional criteria
apply to any storage system using underground chambers and/or pipes:
1. All chambers or pipes must be placed with a minimum slope of 0.2%;
2. Maintenance access must be provided at point of inflow and point of
outflow into the system. The access must be such that it would allow
human access to inspect the functioning of the storage;
3. All pipes or chambers must be vacuum truck accessible through manholes;
4. An underdrain system is recommended for open bottom chambers if the
soil underlying the storage reservoir does not consist of either Type A or
Type B soils;
5. The minimum pipe size allowed for detention in pipes is fifteen inches
(15”);
6. The structural system capacity must be designed to support AASHTO
HS20 (fire truck) loading, as well as anticipated lifetime AASHTO 18,000
lb. equivalent single axle loads (ESALs); and
7. The system must be inspected at least once every five (5) years using
remote video technology. A written record of this inspection must be
submitted to the Utilities Executive Director.
Introduced, considered favorably on first reading, and ordered published this 5th day of
January, A.D. 2016, and to be presented for final passage on the 19th day of January, A.D. 2016.
_________________________________
Mayor
ATTEST:
_____________________________
City Clerk
Passed and adopted on final reading on the 19th day of January, A.D. 2016.
_________________________________
Mayor
ATTEST:
_____________________________
City Clerk
ORDINANCE NO. 007, 2016
OF THE COUNCIL OF THE CITY OF FORT COLLINS
AMENDING CHAPTER 26 OF THE CODE OF THE CITY OF FORT COLLINS
AND THE FORT COLLINS STORMWATER CRITERIA MANUAL
TO MODIFY PROVISIONS IMPLEMENTING
LOW IMPACT DEVELOPMENT PRINCIPLES
WHEREAS, on December 20, 2011, the City Council adopted on second reading
Ordinance No. 174, 2011, amending certain sections of Chapter 26 of the City Code to adopt a
set of technical criteria governing the design and performance of stormwater improvements and
related practices, referred to as the "Fort Collins Stormwater Criteria Manual"; and
WHEREAS, the Fort Collins Stormwater Criteria Manual consists of certain portions of
the Urban Storm Drainage Criteria Manual, 2001 Edition published by the Denver Urban
Drainage and Flood Control District (the "Urban Drainage Manual"), a widely applied and
referenced set of storm water-related standards adopted by reference, and a separately codified
set of extensive amendments customizing the standards, policies and practices of the Urban
Drainage Manual for use in Fort Collins (the “Fort Collins Amendments”), all as set forth in
Section 26-500 of the City Code; and
WHEREAS, the Fort Collins Stormwater Criterial Manual, including the separately
codified Fort Collins Amendments, has been modified from time to time by limited technical
revisions adopted administratively by the Utilities Executive Director and filed with the City
Clerk, as authorized by Section 26-500 of the City Code; and
WHEREAS, one element of the integrated, sustainable stormwater management system
established under the Fort Collins Stormwater Criterial Manual is the use of low impact
development (“LID”) criteria to require and encourage more distributed and landscaping-based
stormwater runoff management and control relying on filtration and infiltration to treat and
manage stormwater runoff; and
WHEREAS, staff has recommended that the LID criteria set forth in Section 3.1 of
Volume 3, Chapter 2, Section K of the Fort Collins Amendments be amended to clarify the Low
Impact Development Criteria set forth therein; and
WHEREAS, the City’s Water Board considered staff’s recommendation at the Board’s
regular meeting on December 17, 2015, and voted to recommend City Council adopt such
amendments to the LID criteria in the Fort Collins Stormwater Criteria Manual; and
WHEREAS, Council has determined that the adoption and implementation of this
Ordinance amending the LID criteria set forth in the Fort Collins Amendments to the Urban
Drainage Manual will promote the purposes of the Stormwater Utility and the City and will
further facilitate the holistic and integrated management of stormwater in Fort Collins.
NOW, THEREFORE, BE IT ORDAINED BY THE COUNCIL OF THE CITY OF
FORT COLLINS as follows:
Section 1. That the City Council hereby makes and adopts the determinations and
findings contained in the recitals set forth above.
Section 2. That Section 3.1 of Volume 3, Chapter 2, Section K of the Fort Collins
Amendments, which is a component of the Fort Collins Stormwater Criteria Manual, is hereby
amended to read as follows:
3.1 Low Impact Development Criteria
Once the WQCV has been calculated in accordance with the specifications of Section 3.0
of this chapter, the total WQCV must be treated by one or more of the methods outlined
in Volume 3, Chapter 4, Treatment BMPs. In addition, the requirements set forth below
in this Section, referred to as Low Impact Development (LID) Criteria, must be met. For
the purposes of this Section, the LID methods and techniques described in Volume 3,
Chapter 1, Section 4.1, Runoff Reduction Practices, together with any methods or
techniques determined by the Utilities Executive Director to be functionally equivalent,
shall be considered LID techniques.
(a) The LID Criteria are as follows:
(1)(a) No less than fifty percent (50%) seventy five percent (75%) of any
newly added impervious area developed or redeveloped area, and
any modification on a previously developed area for which a
construction permit is required under City codes and regulations,
must be treated using one or a combination of LID techniques.; and
or
(2)(b) No less than twenty five percent (25%) fifty percent (50%) of any
newly added pavement areas developed or redeveloped area, and
any modification on a previously developed area for which a
construction permit is required under City codes and regulations,
must be treated using a permeable pavement technology that is
considered an LID technique one or a combination of LID
techniques, when a permeable pavement area covering at least
twenty five (25%) of the drivable surface area on private
development property is constructed as one of the components of
the LID treatment techniques used on that site.
(b)(c) If, in the judgment of the Utilities Executive Director, one or more
requirements of this Section cannot be met due to site engineering
constraints, then a design alternative will be allowed, provided that
the design results in equal or better stormwater quality than would
compliance with the otherwise applicable requirement.
Introduced, considered favorably on first reading, and ordered published this 5th day of
January, A.D. 2016, and to be presented for final passage on the 19th day of January, A.D. 2016.
__________________________________
Mayor
ATTEST:
_______________________________
City Clerk
Passed and adopted on final reading on the 19th day of January, A.D. 2016.
__________________________________
Mayor
ATTEST:
_______________________________
City Clerk