HomeMy WebLinkAboutHARMONY 23 - PDP - PDP160031 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTProject Development Plan (PDP)
Preliminary Drainage Report
for
Harmony 23
submitted to:
City of Fort Collins,
Colorado
September 28, 2016
760 Whalers Way
Bldg C, Suite 200
Fort Collins, CO 80525
970.226.0557 main
303.595.9103 metro
970.226.0204 fax
ideas@tstinc.com
www.tstinc.com
September 28, 2016
Mr. Shane Boyle, P.E., CFM
City of Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80521
Re: Project Development Plan (PDP) for H23
Project No. 1219.0002.00
Dear Mr. Boyle:
We are pleased to submit this Preliminary Drainage Report for H23. This report
analyzes the developed stormwater runoff from the project and provides
stormwater infrastructure and water quality management for runoff. This report has
been prepared based on the City of Fort Collins Stormwater Criteria Manual and
complies with the PDP submittal requirements for a final drainage report.
Respectfully,
TST, INC. CONSULTING ENGINEERS
Derek A. Patterson, P.E. Jon Sweet, P.E.
DAP/JFS/jrm
Harmony 23 Preliminary Drainage Report
TABLE OF CONTENTS
Page
1.0 Introduction
1.1 Scope and Purpose ..................................................................................................... 1
1.2 Project Location and Description ................................................................................. 1
1.3 Previous Studies ......................................................................................................... 3
1.4 Limitations of Future Projections ................................................................................. 3
2.0 Historic/Existing Conditions ......................................................................................... 3
3.0 Developed Conditions Plan
3.1 Design Criteria for Hydrologic Analysis ....................................................................... 6
3.2 Drainage Plan Development ....................................................................................... 7
3.2.1 Street Capacity ................................................................................................... 8
3.2.2 Inlet Design ........................................................................................................ 9
3.2.3 Storm Sewer Design .......................................................................................... 9
3.2.4 Channel Design .................................................................................................. 9
3.2.5 Riprap Design ..................................................................................................... 9
3.2.6 Detention Pond Design .................................................................................... 10
3.3 Low Impact Development .......................................................................................... 12
3.4 Floodplain Management ............................................................................................ 14
4.0 Conclusion ....................................................................................................................... 14
5.0 References ....................................................................................................................... 16
Figures
Figure 1. Vicinity Map ................................................................................................................... 2
Figure 2. Outfall to the Poudre River ............................................................................................ 5
Figure 3. Four-Step Process for Stormwater Quality Management ............................................ 12
Appendices
Appendix A: Rational Method Hydrologic Analysis
Appendix B: Street Capacity and Inlet Analysis
Appendix C: Storm Sewer Design
Appendix D: Channel Design
Appendix E: Riprap Design
Appendix F: Detention Pond Design
Appendix G: FIRM Maps and Original Floodplain Workmap
Harmony 23 Preliminary Drainage Report
Page 1
1.0 Introduction
1.1 Scope and Purpose
This report presents the results of a preliminary drainage analysis for the H23 project. This
report has been developed in accordance with the City of Fort Collins Stormwater Criteria Manual
requirements and complies with Project Development Plan (PDP) submittal requirements.
1.2 Project Location and Description
The H23 project is a multifamily development situated on approximately 25 acres. The project is
located in the northeast corner of Section 4, Township 6 North, Range 68 West, more
specifically at the southwest corner of the intersection of Harmony Road and Strauss Cabin
Road. The site is generally bounded by the following roadways: Strauss Cabin Road on the
east, Harmony Road on the north, and the Fossil Creek Reservoir Inlet Ditch (FCRID) along the
south and west. Surrounding properties include: The Arapaho Bend Natural Area on the north
side of Harmony Road, the Harmony & Strauss Cabin Convenience Shopping Center
Subdivision (development recently approved) to the east of Strauss Cabin Road, Brookfield
Subdivision to the southwest, and undeveloped land to the west.
The Boxelder Ditch cuts through the site starting north at Harmony Road and running south
through the middle of the site where it crosses Strauss Cabin Road approximately 1600’ south
of Harmony Road.
This development is located within the Cache la Poudre watershed and City of Fort Collins
Poudre River drainage basin. This project site sits just west of the FEMA regulated floodway but
within the 500-yr floodplain, per FEMA FIRM Maps 08069C0994F LOMR dated December 15,
2014. The floodplain and floodways lines are shown in Figure 1 on the next page.
Harmony 23 Preliminary Drainage Report
Page 2
Figure 1. Vicinity Map
Harmony 23 Preliminary Drainage Report
Page 3
1.3 Previous Studies
WEITZEL POND #1 Drainage Report for Harmony & Strauss Cabin
ODP Drainage Report for Harmony & Strauss Cabin
Harmony & Strauss Cabin Subdivision Filing No. 1 Convenience Shopping Center PDP
Final Drainage Report
North I-25 EIS, August 2011
Poudre River Drainage Basin Master Plan
1.4 Limitations of Future Projections
The analysis and proposed stormwater improvements contained in this study are for the H23
project area. Assumptions have been made to account for future development adjacent to the
site where developed flows and storm infrastructure from this project will influence future
designs. In addition, assumptions were made to account for interim and ultimate tail water
conditions downstream of this site. It is assumed that the outfall from the H23 site will connect
to a future stormwater system, which will ultimately daylight into a regional detention facility for
the 266-acre Harmony and I-25 development. This regional detention facility is also assumed to
be a non-potable irrigation pond. The final/ultimate water surface elevation in this future
regional detention pond will need to be designed to not effect upstream developments. A
master plan for the Harmony and I-25 development is in progress, but has not been completed
at the time of this report.
The grading and drainage plan provided herein assumes that the WEITZEL POND #1 project
has progressed and has filled the portion of the Existing Gravel Pond #1 shown in the WEITZEL
POND #1 plans. The report also assumes that the Convenience Shopping Center has been or
is being constructed when construction begins on this project, and that the Box Elder Ditch will
be realigned through the site. For this project the interim 100-yr WSEL in the interim regional
pond is assumed to be a 4838.59, per the Convenience Shopping Center report. This tailwater
elevation was assumed to be the worst case scenario, and was used for the H23 design and
calculations. The ultimate/final water surface elevation in the regional detention pond is
assumed to be equal to or lower than this elevation.
Stream stability analysis, open water and wetlands mitigation are beyond the scope of this
report and will be addressed separately or in a subsequent design report.
2.0 Historic/Existing Conditions
Historically this area was undeveloped grasslands, that was eventually utilized for farming.
The Boxelder Ditch which runs through the site was used for irrigation purposes. Today, this
site is no longer used for farming and has returned back to undeveloped grasslands. The site
Harmony 23 Preliminary Drainage Report
Page 4
generally slopes from the west to the east to the low point in Strauss Cabin Road. Slopes vary
from 1:1 on the west end to basically flat on the east.
According to the Natural Resources Conservation Service (NRCS) the project site is
characterized by Type A, B and D soils. The NRCS soils data for this site can be found in the
Appendix
The historic stormwater runoff rate from this site is based on the calculations provided in the
Convenience Shopping Center report, which was determined to be 0.164 cfs/acre.
There are currently a small amount wetlands located on the project site. As stated previously
wetlands will be addressed separately in a subsequent design report if required.
Harmony 23 Preliminary Drainage Report
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Figure 2. Outfall to the Poudre River
Harmony 23 Preliminary Drainage Report
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3.0 Developed Conditions Plan
3.1 Design Criteria for Hydrologic Analysis
The drainage plan presented in this report has been developed in accordance with the City of
Fort Collins Stormwater Criteria Manual and the City of Fort Collins submittal requirements for a
Project Development Plan (PDP). The drainage plan presented is based upon the allowable
developed stormwater release rates prescribed for the Poudre River drainage basin, that being
the 2-year historic rate.
The drainage basin presented in this report is less than 90 acres, therefore, the method used to
analyze drainage for this project will be the Rational Method. Runoff calculations for both the 2-year
and 100-year storms will be presented here.
The Rational Method is given by:
Q = C(Cf)IA where
Q is the maximum rate of runoff in cfs
C is the runoff coefficient
Cf is the runoff coefficient frequency factor adjustment
I is the rainfall intensity in inches per hour for a storm duration equal to the time of
concentration
A is the total area of the basin in acres
The runoff coefficient C has different values depending on the design storm recurrence interval.
The runoff coefficient is also dependent on land use or surface characteristics/imperviousness.
Runoff coefficients were assigned using Table RO-11 from the Fort Collins Stormwater Criteria
Manual. The frequency factor adjustment, Cf, varies depending on the storm frequency and can be
found in Table RO-12 of the Fort Collins Stormwater Criteria Manual.
The rainfall intensity is selected from Rainfall Intensity Duration Frequency Curves for the City of
Fort Collins (Tables RA-7 through RA-9 of the Fort Collins Stormwater Criteria Manual).
In order to utilize the Rainfall Intensity Duration Curves, the time of concentration is required. The
following equation is used to determine the time of concentration
tc = ti + tt where
tc is the time of concentration in minutes
ti is the initial or overland flow time in minutes
Harmony 23 Preliminary Drainage Report
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tt is the conveyance travel time in minutes
The initial or overland flow time is calculated with the UDFCD equation:
0.33
f
i S
t 1.87 1.1 * C D
C
3.2 Drainage Plan Development
The H23 project is proposed to be a multifamily site accompanied by parking areas, open
space, and public roadway improvements. The site and associated storm sewer system has
been designed to collect and convey a majority runoff from this project, including portions of the
fronting ½ of the surrounding public roadways to the two separate constructed wetland ponds
located onsite. Due to design constraints a small portion of runoff from the project site will be
collected and conveyed to an offsite detention pond where it will be detained and released.
For preliminary design calculations the site was divided into several larger basins. All “N”, “S”
and “U” basins described below will be further subdivided with final design.
Basin N-1, as shown on the Drainage Plan, is the northern portion of the project site which
includes open space, parking areas and building footprints. Runoff from this basin is conveyed
via curb & gutter into the storm sewer system which drains into to Pond A. The calculated water
quality capture volume (WQCV) from this basin will be treated in Pond A which is designed as a
constructed wetland pond. They 100-yr detention portion of this basin will also be detained in
Pond A where it will ultimately be released to the proposed storm sewer system in Strauss
Cabin Road which conveys runoff to Pond B.
Basin S-1 is the southern portion of the project site which includes open space, parking areas
and building footprints. Runoff from this basin is conveyed via curb & gutter into the storm
sewer system which drains into Pond B. Pond B which is designed as a constructed wetland
pond will treat the WQCV from this basin.
Basin S-2 incorporates the southern fronting portion of Strauss Cabin Road to the back of the
detached sidewalk. Runoff from this basin is conveyed via curb & gutter to a low point in
Strauss Cabin Road where it is conveyed via the proposed storm sewer system and into Pond
B. The WQCV from this basin will be treated in Pond B.
Basin U-1 incorporates the fronting portions of Harmony Road and Strauss Cabin Road in
addition to a portion of the project site. Runoff from this basin is conveyed via curb & gutter to
the low point in Strauss Cabin Road just south of Hacienda Drive, where it is conveyed via the
proposed storm sewer system south to the offsite ponds designed with the Convenient
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Shopping Center Report. All storage for this basin will be handled in the offsite ponds.
Basins O-1, O-2, and O-3 are offsite basins that will pass through the site. No water quality or
detention will be provided for these basins as they are not part of the subject property.
Basins O-1 and O-2 are the areas between the FCRID and the property boundary which
consists of gravel access road and undeveloped open space. Runoff from Basin O-1 will be
routed through Pond A and ultimately Pond B, and runoff from Basin O-2 will be routed through
Pond B.
Basin O-3 is the area just south of the project which consists of a small portion of undeveloped
open space and a portion of Strauss Cabin Road. Runoff from this basin is conveyed via curb &
gutter to a low point in Strauss Cabin Road where it will be routed through Pond B.
The 100-yr runoff volume for all “N” basins will be detained in Pond A, while all runoff for all “S”
basins will be detained in Pond B. The 100-yr runoff volume for Basin U-1 will be detained in
the existing ponds offsite.
3.2.1 Street Capacity
Street capacities have been analyzed using the Urban Drainage UD-Inlet spreadsheet, version
4.01. Street capacity was analyzed along Strauss Cabin Road on the west side where ultimate
roadway improvements are proposed between Harmony Road and the south end of this project.
Table ST-2 and ST-3 in the City of Fort Collins Stormwater Criteria Manual state inundation
standards for the minor and major storms. These standards are summarized in the table below.
Table 1.
Street ID Street Classification Minor Storm (2-yr)
requirements
Major Storm (100-yr)
requirements
Strauss Cabin Road 2-Lane Arterial No curb-overtopping,
flow spread must
leave at least 12’ wide
travel path in each
direction
Depth of water must
not exceed bottom of
median gutter, 12”
max depth at gutter
flowline, flow must be
contained within
ROW.
The streets meet the applicable requirements and will function below the allowed capacities.
The results of the street capacity analysis can be found with supporting calculations in Appendix
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B.
3.2.2 Inlet Design
Inlets have been analyzed using the Urban Drainage UD-Inlet spreadsheet, version 4.01. CDOT
Type R inlets are proposed to collect runoff and have been placed at the low points of the
basins where infall, vertical curb & gutter is located and have been analyzed for a “sump”
condition. These inlets have been sized to capture the 100-yr storm.
On-grade Type 13 inlets have been strategically placed within the cross pans in the parking lot
to intercept portions of runoff and direct it to the proposed storm sewer system. These have
been placed to reduce the amount or runoff that would flow down the drive isle, and to help
reduce inlet sizes further downstream.
The results of the inlet analysis will be provided at final design in Appendix B.
3.2.3 Storm Sewer Design
Storm sewer pipes have been analyzed using UDSEWER 2009, version 1.4. All storm pipes on
this project site are designed to collect and convey the 100-yr storm runoff. The pipes have all
been sized to ensure that the hydraulic grade lines remain below the flowline elevation at inlets
and below rim elevations at manholes.
The results of the storm sewer analysis will be provided at final design in Appendix C.
3.2.4 Channel Design
Proposed channels and swales at this project site have been analyzed using Bentley
Flowmaster V8i, Select Series 1 software. These swales have been designed to include 1’ of
freeboard above the normal 100-yr water depth in the channel. Where the 1’ criteria isn’t
possible, the swales have been checked to make sure they can pass at least 133% of design
flow.
Swale A-A is triangular swale located in Basin N-1 which conveys a portion of runoff within that
basin directly into Pond A.
The results of the channel design will be provided at final design in Appendix D.
3.2.5 Riprap Design
Riprap has been proposed at the outlet pipe to Pond B. Although the approximate groundwater
elevation is 4838 at this location and the pipe outlet and riprap are anticipated to be underwater
Harmony 23 Preliminary Drainage Report
Page 10
during an average day scenario, the groundwater in that pond may be lowered at any given time
due to future construction activities at this site, so riprap has been proposed in this area as a
ground stabilization measure.
The results of riprap sizing will be provided at final design in Appendix E.
All other pipes which discharge into the ponds onsite will discharge into concrete forebays.
These forebays are designed to dissipate energy in addition to providing sedimentation.
3.2.6 Detention Pond Design
The existing conditions for this area was analyzed with the Convenience Shopping Center
report to determine the allowable release rate from the site. The 2-yr historic discharge for this
area was determined to be 4.50 cfs for the 27.2 acres estimated in that report. This ends up
being a release rate of approximately 0.165 cfs/acre (4.5/27.2) which is the allowable release
rate used in this report.
There will be two ponds utilized on this site for water quality and detention. Pond A on the
northeast end of the site and Pond B on the south end of the site. Both are designed as
constructed wetland ponds to treat the WQCV. Both ponds will be supplied by groundwater to
help maintain vegetation and microorganisms.
The Ex. Gravel Pond #2 utilized in the Convenience Shopping Center Report will be utilized to
detain the 100-yr runoff from Basin U-1. Per conversations with the City stormwater staff, the
existing gravel ponds can be used as a water quality feature. Therefore, the WQCV for Basin
U-1 was not added into the total required volume being detained offsite in Ex. Gravel Pond #2.
The UDFCD UD-BMP spreadsheet version 3.05 was used to calculate the WQCV for each of
the two constructed wetland ponds. Pond A is sized to collect the WQCV for all N basins, and
Pond B is sized to collect the WQCV for all S basins. The WQCV is designed to be released in
24-hr as recommend by UDFCD for a constructed wetland pond. In addition, the minimum
permanent pool and forebay volumes were also sized using this spreadsheet.
A mass-balance spreadsheet was used to calculate the overall 100-yr detention requirements
for this site. The required 100-yr detention volumes for Pond A and Pond B calculated from this
spreadsheet were determined to be 1.92 acre-feet, and 2.27 acre-feet respectively. An
additional 20% was added to these volumes, per City Criteria, resulting in a total 100-yr volume
of 2.39 acre-feet for Pond A and 3.98 acre-feet for Pond B. The total volume required in the
ponds based on City Criteria is the 100-yr plus the WQCV. Therefore, the required total volume
was determined to be 2.56 acre-feet for Pond A and 4.27 acre-feet for Pond B. The results for
these ponds are provided in Table 2.
Harmony 23 Preliminary Drainage Report
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Table 2.
Pond
ID
Contributing
Area (acres)
Groundwater
Surface
Elevation
2-yr
Historic
Release
Rate
(0.165
cfs/acre)
100-yr
Detention
Volume
(120%)
(ac-ft)
WQCV
(ac-ft)
Total
Provided
Storage
(ac-ft)
Pond A 9.77 4843.00 1.67 2.31 0.16 2.78
Pond B 11.40 4839.00 2.78 2.73 0.19 3.05
Total
Required
5.04 0.35 5.83
A mass-balance spreadsheet was used to calculate the overall 100-yr detention requirement for
Basin U-1. The required 100-yr detention volume from this Basin was calculated to be 1.14 ac-
ft. An additional 20% was added to the volume for a total volume of 1.37 ac-ft. This volume
was then added to the 11.57 ac-ft required per the Convenience Shopping Center Report for a
total volume of 12.94 ac-ft. Because Ex. Gravel Pond #1 has no available storage left, the 1.37
ac-ft was added to Ex. Gravel Pond #2. The approximate surface area of this pond was
determined to be approximately 14.53 acres resulting in an increase of storage depth of 0.094
feet (1.37ac-ft / 14.53 acres). Because we will be adding additional storage volume in this
pond, the emergency spillway designed with the Convenience Shopping Center report will need
to be modified. To simplify the design, the 9.0 cfs release rate from the spillway structure will be
maintained and both the 2-yr spillway crest (Ex. Elev.=4837.39) and the 100-yr spillway crest
(Ex. Elev.=4837.64) will be raised 0.10 feet each.
The undeveloped areas adjacent to the site denoted as O-1, O-2, and O-3 will release
undetained through the site. This amount will be treated as a pass-through flow. The resulting
amount of stormwater (100-yr) passing from Pond A will be approximately 1.1 cfs and 5.9 cfs for
Pond B. The total 100-yr release from these undeveloped areas amounts to 7.0 cfs.
Outlet structures for Pond A and B will consist of 3 stages. A WQCV stage (24-hr drain time),
detention volume (2-yr historic release), and emergency overflow. An emergency overflow
stage was added due to site constraints discussed below. All ponds will have a minimum 1’ of
freeboard above the detention surface elevation.
The ponds for this site were located in areas to maximize developable area. Emergency
spillways for each pond have not been provided due to site constraints. Therefore, these ponds
don’t have a defined spillway. Instead Pond A is designed to pass a portion of the emergency
flow through the 100-yr overflow stage on the outlet structure. Any runoff which exceeds the
overflow capacity will pond up to the Boxelder Ditch located along the east side of this pond,
where it will ultimately either spill into and or across this ditch to the low point in Strauss Cabin
Harmony 23 Preliminary Drainage Report
Page 12
Road. The difference between the detention surface elevation of Pond A and the Boxelder
Ditch is approximately 1.25’.
Similar to Pond A, Pond B will also have an emergency overflow stage on the outlet structure.
However, this outlet structure and outlet pipe will be sized to convey the 100-yr storm event. In
the event that the outlet pipe becomes clogged, runoff would back up into the parking lot until it
would spill down the drive entrance into Strauss Cabin Road. This elevation is approximately
4850. All buildings within this area will be designed at an elevation higher than the spill
elevation to prevent flooding.
3.3 Low Impact Development
With the building coverage and parking areas, the amount of new imperviousness introduced to
this site will be approximately 60%. However, the grading design aims to minimize the “directly
connected impervious area” (DCIA) as much as possible. Strategies to minimize directly
connected impervious areas follow the Four-Step Process for Stormwater Quality Management,
as outlined in Volume 3 of the Urban Storm Drainage Criteria Manual. The four-step process is
shown below.
Figure 4. Four-Step Process for Stormwater Quality Management
Harmony 23 Preliminary Drainage Report
Page 13
Step 1: Runoff Reduction Practices for this project site are planned to include parking lot
drainage toward grassed swales located adjacent to parking lot areas to capture and route
stormwater drainage toward the two separate ponds located on the north and south ends of the
site. These grassed swales are intended to have meandering alignments to increase the
aesthetic and the time of concentration.
Step 2: BMP’s to Provide WQCV with Slow Release for this project site will employ LID
techniques such as constructed wetland ponds to act as a sedimentation basin by allowing for
the sediment, fines and pollution suspended in the stormwater to settle out into the groundwater
fed ponds. The ponds will be equipped with outlet structures to control the release and improve
water quality.
The City of Fort Collins criteria for low impact development, as outlined in the Stormwater
Criteria Manual in Volume 3, Chapter 3, are as follows:
No less than 75% of any newly developed or redeveloped area must be treated using
one or a combination of LID techniques,
OR
No less than 50% of any newly developed or redeveloped area must be treated using
one or a combination of LID techniques when a permeable pavement area covering at
least 25% of drivable surface area on private development property is constructed as
one of the components of the LID treatment techniques used on that site.
For this site, approximately 85% of the project will be treated using constructed wetland ponds,
and therefore, permeable pavers will not be required. The other 15% will be treated in the
massive gravel ponds located offsite.
Step 3: Stabilized Drainageways will come in the form of seeding, planting, energy dissipation
basins (forebays), and maintaining the constructed wetlands and grassed swales created for
this project site.
Step 4: Site Specific Source Control BMP’s will include things like proper maintenance and
sedimentation removal of the forebays and constructed wetland ponds.
The areas where the various LID techniques are planned to be utilized on the site are shown on
the drainage map. LID calculations are included in Appendix F.
Harmony 23 Preliminary Drainage Report
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3.4 Floodplain Management
This site is situated outside of any City of Fort Collins regulatory floodways and floodplains.
This project site sits within the FEMA FIRM Map 08069C0994F dated December 19, 2006. The
new LOMR (Case # 14-08-0580P, effective date 12-15-2014) that just received FEMA approval
corrected the floodway and floodplain lines to align with the original floodplain workmap.
Information provided in this LOMR was taken into consideration for this project. More
specifically, flood zone designations within this project site per the LOMR are as follows:
Flood Zone X, Shaded 500-YEAR FLOODPLAIN: Areas of 0.2% annual chance flood
hazard. Areas of 1% annual chance flood with average depth less than one foot or with
drainage areas of less than one square mile.
Flood Zone X, Unshaded: Areas determined to be outside the 0.2% annual chance
floodplain.
Chapter 10, Flood Prevention and Protection, of the Fort Collins Municipal Code provided
guidance and limitations for building and development within the floodway and floodplain.
Division 4 – Poudre River Flood Hazard Areas of this chapter provide specific standards for
development within the Poudre River floodway and flood fringe.
The “Limits of Development” as shown on the Grading and Drainage Plan are outside of the
half-foot floodway. However, we recognize that a majority of this area still resides within the
500-year floodplain. Land uses proposed within the “Limits of Development” do not include any
critical facilities, essential service critical facilities, hazardous materials facilities, government
services, or at risk population facilities. All structures planned to be built within the “Limits of
Development” will be elevated and flood-proofed 2 feet above the 100-year flood elevations
(shown as Base Flood elevations on the FIRM maps.)
4.0 Conclusion
The City of Fort Collins Stormwater Criteria Manual has been used to establish the criteria for a
developed condition runoff plan within the H23 project. This PDP drainage design report has
highlighted the following items:
Project site development is outside of the effective floodway boundary, but within the 500-yr
floodplain.
LID techniques are planned to be implemented within the site design including measures
that will help minimize directly connected impervious areas. These LID techniques will
Harmony 23 Preliminary Drainage Report
Page 15
include grassed swales and constructed wetland ponds.
Water quality and stormwater detention for the project will be provided in two separate
wetland ponds located onsite. These ponds have been sized to release the 100-yr storm at
the 2-yr historic release.
A small portion of this project will be detained offsite in the ex. Gravel ponds located east of
the project.
All storm infrastructure has been sized to collect and convey the 100-yr storm event.
Harmony 23 Preliminary Drainage Report
Page 16
5.0 References
1. City of Fort Collins Stormwater Criteria Manual, Amendments to the Urban Drainage
and Flood Control District Criteria Manual, Adopted December 2011, Last Revision
April 2012.
2. Urban Drainage and Flood Control District Criteria Manual, Volume 3, August 2011
3. Federal Emergency Management Agency, 2006, Flood Insurance Rate Map, Larimer
County, Colorado, Map Number 08069C0994F
4. Federal Emergency Management Agency, 2006, Flood Insurance Rate Map, Larimer
County, Colorado, Map Number 08069C1013F
5. Natural Resources Conservation Services, 2013, Web Soil Survey: Soil Survey Area
Larimer County Area, Version 8, Dec 23, 2013
6. Colorado Division of Reclamation, Mining & Safety website,
http://mining.state.co.us/Pages/Home.aspx
7. Chapter 10 of the Fort Collins Municipal Code, http://colocode.com/fcmunihtml.html
8. LOMR, Case #14-08-0580P, Letter of Map Revision (LOMR-BD) Based on Better
Data on the Cache la Poudre River I-25 Divided Flow Path Southwest of Harmony
Road and Interstate 25, Anderson Consulting Engineers, Effective Date December
15, 2014.
APPENDIX A
Rational Method Hydrologic Analysis
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H23 Preliminary Drainage Report
City of Fort Collins
IDF Curves
Duration 2-yr 10-yr 100-yr
5 2.85 4.87 9.95
6 2.67 4.56 9.31
7 2.52 4.31 8.80
8 2.40 4.10 8.38
9 2.30 3.93 8.03
10 2.21 3.78 7.72
11 2.13 3.63 7.42
12 2.05 3.50 7.16
13 1.98 3.39 6.92
14 1.92 3.29 6.71
15 1.87 3.19 6.52
16 1.81 3.08 6.30
17 1.75 2.99 6.10
18 1.70 2.90 5.92
19 1.65 2.82 5.75
20 1.61 2.74 5.60
21 1.56 2.67 5.46
22 1.53 2.61 5.32
23 1.49 2.55 5.20
24 1.46 2.49 5.09
25 1.43 2.44 4.98
26 1.40 2.39 4.87
27 1.37 2.34 4.78
28 1.34 2.29 4.69
29 1.32 2.25 4.60
30 1.30 2.21 4.52
31 1.27 2.16 4.42
32 1.24 2.12 4.33
33 1.22 2.08 4.24
34 1.19 2.04 4.16
35 1.17 2.00 4.08
36 1.15 1.96 4.01
37 1.13 1.93 3.93
38 1.11 1.89 3.87
39 1.09 1.86 3.80
40 1.07 1.83 3.74
41 1.05 1.80 3.68
42 1.04 1.77 3.62
43 1.02 1.74 3.56
44 1.01 1.72 3.51
45 0.99 1.69 3.46
46 0.98 1.67 3.41
47 0.96 1.64 3.36
48 0.95 1.62 3.31
49 0.94 1.60 3.27
50 0.92 1.58 3.23
51 0.91 1.56 3.18
52 0.90 1.54 3.14
53 0.89 1.52 3.10
54 0.88 1.50 3.07
55 0.87 1.48 3.03
56 0.86 1.47 2.99
57 0.85 1.45 2.96
58 0.84 1.43 2.92
59 0.83 1.42 2.89
60 0.82 1.40 2.86
H23 Preliminary Drainage Report
From the Town of Timnath Design Criteria Manual and Construction Specifications
y = 2.5665e-0.021x
R² = 0.9633
y = 26.332x-0.53
R² = 0.9879
0.00
2.00
4.00
6.00
8.00
10.00
12.00
010203040506070
Rainfall Intensity (in/hr)
Storm Duration (min)
City of Fort Collins IDF Curves
2-yr
10-yr
100-yr
Expon. (2-yr)
Power (100-yr)
Appendix A
H23 Preliminary Drainage Report
City of Fort Collins
Rational Method Runoff Coefficients
Lawn, Heavy, <2% Slope 0.20
Lawn, Heavy, >7% Slope 0.35
Lawn, Heavy, 2-7% Slope 0.25
Lawn, Sandy, <2% Slope 0.10
Lawn, Sandy, >7% Slope 0.20
Lawn, Sandy, 2-7% Slope 0.15
Roofs 0.95
Streets: Permeable Pavers 0.30
Streets: Gravel 0.50
Streets: Paved 0.95
From Table 3-3 of the City of Fort Collins, Stormwater Criteria
Runoff
Coefficient
Appendix A
H23 Preliminary Drainage Report
C2 C10 C100
Streets: Paved 3.36 0.95
Lawn, Heavy, <2% Slope 4.31 0.20
Roofs 2.09 0.95
Total N Basins 9.77 Total % Imp. 54.6% Avg. 100-yr C100 = 0.77
Streets: Paved 4.17 0.95
Lawn, Heavy, <2% Slope 4.76 0.20
Roofs 1.63 0.95
Streets: Paved 0.66 0.95
Lawn, Heavy, <2% Slope 0.18 0.20
Roofs 0.00 0.95
Total S Basins 11.40 56.1% Avg. 100-yr C100 = 0.78
Streets: Paved 2.71 0.95
Lawn, Heavy, <2% Slope 2.59 0.20
Roofs 0.52 0.95
Total U Basins 5.82 55.5% Avg. 100-yr C100 = 0.77
Total 26.99 Total % Imp. 55.4% Avg. 100-yr C100 = 0.78
*Percent Impervious Values based on UDFCD Vol 1., Chapter 6, Table 6-3
Rational Method Frequency Adjustment Factors
Min year Max year Frequency Factor, Cf
210 1
11 25 1.1
26 50 1.2
51 100 1.25
From Table 3-4 in the City of Fort Collins, SDDCCS
U-1 5.82 55.5% 0.62 0.62 0.62 0.77
0.79 0.99
0.62 0.62 0.77
S-2 0.84 79.3% 0.79 0.79
0.61 0.61 0.76
0.62
Attribute Area
(ac)
Runoff
Coefficient, C
Percent
Impervious
S-1 10.56 54.3% 0.61
Composite C
Frequency Adjusted Runoff Coefficients (C*Cf)
Table A-1
N-1 9.77
Basin Composite Runoff Coefficients
Basin/ Sub-
Basin Area (ac) Attribute
54.6%
Appendix A
H23 Preliminary Drainage Report
Overland Flow Average Channelized Channel Channel Channelized
Length, D Overland Slope Tov Tov Tov Flow Length Slope Velocity Time (Tt)
(ft) (%) 2-year 10-year 100-year (ft) (%) (ft/s) (min) 2-year 10-year 100-year
N-1 0.62 0.62 0.77 190 2 10 10 7 615 2.2 3 3.4 13 13 10
S-1 0.61 0.61 0.76 66 2 6 6 4 1150 1 2 9.6 16 16 14
S-2 0.79 0.79 0.99 26 2 2 2 1 630 2.2 2.9 3.6 6 6 5
U-1 0.62 0.62 0.77 66 2 6 6 4 950 0.9 1.8 8.8 15 15 13
O-1 (EX. CONDITIONS
OFFSITE) 0.20 0.20 0.25 50 33 4 4 4 0 0 1 0.0 5 5 5
O-2 (EX. CONDITIONS
OFFSITE) 0.20 0.20 0.25 50 33 4 4 4 0 0.0 1.0 0.0 5 5 5
O-3 (EX. CONDITIONS
OFFSITE) 0.20 0.20 0.25 26 2 7 7 6 136 3.6 3.6 0.6 8 8 7
Basin
Table A-2
Basin Time of Concentration
Frequency Adj. Runoff Coefficients (C*Cf)
C2 C10 C100
Overland Travel Time Time of Concentration
Tc = Tov + Tt (min)
Appendix A
H23 Preliminary Drainage Report
2 - year 10 - year 100 - year 2 - year 10 - year 100 - year 2 - Year 10 - Year 100 - Year 2 - Year 10 - Year 100 - Year
N-1 9.77 0.62 0.62 0.77 13 13 10 1.98 3.39 7.72 12.0 20.5 58.4
S-1 10.56 0.61 0.61 0.76 16 16 14 1.81 3.08 6.71 11.7 19.9 54.2
S-2 0.84 0.79 0.79 0.99 6 6 5 2.67 4.56 9.95 1.8 3.0 8.3
U-1 5.82 0.62 0.62 0.77 15 15 13 1.87 3.19 6.92 6.7 11.4 31.0
O-1 (EX. CONDITIONS
OFFSITE) 0.44 0.20 0.20 0.25 5 5 5 2.85 4.87 9.95 0.3 0.4 1.1
O-2 (EX. CONDITIONS
OFFSITE) 2.04 0.20 0.20 0.25 5 5 5 2.85 4.87 9.95 1.2 2.0 5.1
O-3 (EX. CONDITIONS
OFFSITE) 0.38 0.20 0.20 0.25 8 8 7 2.40 4.10 8.80 0.2 0.3 0.8
Total Bypass Flow 7.0
Time of Concentration, Tc (min)
Table A-3
Basin Peak Discharge
Basin Rainfall Intensity (in/hr) Peak Discharge (cfs)
Basin Area
(ac)
Frequency Adj. Runoff Coefficients
Appendix A
H23 Preliminary Drainage Report
2 - year 10 - year 100 - year 2 - year 10 - year 100 - year 2 - year 10 - year 100 - year 2 - year 10 - year 100 - year 2 - year 10 - year 100 - year
1 (Pond A Outlet) N-1 9.77 13 13 10 0.62 0.62 0.77 1.98 3.39 7.72 11.97 20.50 58.36 12.23 20.93 59.45
2 (SDMH-1C) Pond A Release, U-1 5.82 15 15 13 0.62 0.62 0.77 1.87 3.19 6.92 8.32 13.06 32.65 8.57 13.49 33.74
*3 (SDMH-1A) Pond A and B Release,
U-1 26.99 15 15 13 0.62 0.62 0.77 1.87 3.19 6.92 11.81 16.55 36.14 13.23 18.97 42.31
6 (Pond B Outlet) All S Basins 11.40 16 16 14 0.63 0.63 0.78 1.81 3.08 6.71 12.90 21.95 59.77 19.90 28.95 66.78
Contributing Basins &
Design Point Design Points
*Peak discharge based on combined release rates from Ponds A and B plus Basin U-1 which is
released undetained from the site.
Peak Discharge + Offsite Bypass Flows (cfs)
Table A-4
Attenuation of Peak Discharge
Time of Concentration, Tc (min) Weighted Runoff Coefficient Rainfall Intensity (in/hr) Peak Discharge (cfs)
Area (acres)
Appendix A
APPENDIX B
Street Capacity and Inlet Analysis
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 16.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.020
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 40.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 12.0 32.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 12.0 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
H23
Inlet-01A
UD-Inlet_v4.01, Inlet-1A 9/27/2016, 1:47 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 4 4
Water Depth at Flowline (outside of local depression) Ponding Depth = 4.4 9.2 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.20 0.60 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.42 0.87
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 0.67 0.94
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 7.2 45.8 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 6.7 31.0 cfs
INLET IN A SUMP OR SAG LOCATION
CDOT Type R Curb Opening
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.01, Inlet-1A 9/27/2016, 1:47 PM
APPENDIX F
Detention Pond Design
H23 Preliminary Drainage Report
Detention Requirements Pond A - Major Storm (100-yr)
Mass Balance Method
0.77
1.61 cfs
9.77 acres
Detention
Requirements 1.92 acre-feet
City of Fort Collins
criteria (120%) 2.31 acre-feet
Time (min) Intensity (in/hr) Qin (cfs) Volume
in (ft
3
) Qout
(cfs) Volumeout
(ft
3
) Volume detained
(acre-feet)
5 9.95 74.853 22,455.86 1.61 484 0.504
10 7.72 58.077 34,846.07 1.61 967 0.778
15 6.52 49.049 44,144.38 1.61 1,451 0.980
20 5.60 42.128 50,553.89 1.61 1,934 1.116
25 4.98 37.464 56,196.06 1.61 2,418 1.235
30 4.52 34.004 61,206.31 1.61 2,902 1.338
35 4.08 30.693 64,456.21 1.61 3,385 1.402
40 3.74 28.136 67,525.55 1.61 3,869 1.461
45 3.46 26.029 70,278.93 1.61 4,353 1.513
50 3.23 24.299 72,896.90 1.61 4,836 1.562
55 3.03 22.794 75,221.48 1.61 5,320 1.605
60 2.86 21.515 77,455.78 1.61 5,803 1.645
65 2.70 20.312 79,216.14 1.61 6,287 1.674
70 2.60 19.560 82,150.07 1.61 6,771 1.730
75 2.50 18.807 84,632.63 1.61 7,254 1.776
80 2.40 18.055 86,663.81 1.61 7,738 1.812
85 2.30 17.303 88,243.62 1.61 8,221 1.837
90 2.20 16.550 89,372.05 1.61 8,705 1.852
100 2.05 15.422 92,531.67 1.61 9,672 1.902
110 1.90 14.294 94,337.17 1.61 10,640 1.921
120 1.75 13.165 94,788.54 1.61 11,607 1.910
130 1.60 12.037 93,885.79 1.61 12,574 1.867
140 1.40 10.532 88,469.30 1.61 13,541 1.720
150 1.20 9.027 81,247.32 1.61 14,508 1.532
160 1.15 8.651 83,052.82 1.61 15,476 1.551
170 1.10 8.275 84,406.94 1.61 16,443 1.560
180 1.05 7.899 85,309.69 1.61 17,410 1.559
Runoff Coefficient, C =
2-yr Release, Qout =
Area =
Appendix F
Project:
Basin ID:
Design Information (Input):
Width of Basin Bottom, W = ft Right Triangle OR…
Length of Basin Bottom, L = ft Isosceles Triangle OR…
Dam Side-slope (H:V), Zd = ft/ft Rectangle OR…
Circle / Ellipse OR…
Irregular X (Use Overide values in cells G32:G52)
MINOR MAJOR
Storage Requirement from Sheet 'Modified FAA': acre-ft.
Stage-Storage Relationship: Storage Requirement from Sheet 'Hydrograph': acre-ft.
Storage Requirement from Sheet 'Full-Spectrum': acre-ft.
Labels Water Side Basin Basin Surface Surface Volume Surface Volume Target Volumes
for WQCV, Minor, Surface Slope Width at Length at Area at Area at Below Area at Below for WQCV, Minor,
& Major Storage Elevation (H:V) Stage Stage Stage Stage Stage Stage Stage & Major Storage
Stages ft ft/ft ft ft ft
2
ft
2
User ft
3
acres acre-ft Volumes
(input) (input) Below El. (output) (output) (output) Overide (output) (output) (output) (for goal seek)
4843.00 (input) 18,220 0 0.418 0.000
4844.00 4.00 0.00 0.00 21,150 19,685 0.486 0.452
4845.00 4.00 0.00 0.00 24,180 42,350 0.555 0.972
4846.00 4.00 0.00 0.00 27,312 68,096 0.627 1.563
4847.00 4.00 0.00 0.00 30,544 97,024 0.701 2.227
4847.75 4.00 0.00 0.00 33,035 120,866 0.758 2.775
4848.00 4.00 0.00 0.00 38,013 129,747 0.873 2.979
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Project:
Basin ID:
STAGE-STORAGE SIZING FOR DETENTION BASINS
4843.00
4844.00
4845.00
4846.00
4847.00
4848.00
4849.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
Stage (ft. elev.)
Storage (acre-feet)
STAGE-STORAGE CURVE FOR THE POND
UD Detention Pond A VolCalc, Basin 9/27/2016, 10:20 AM
Sheet 1 of 3
Designer:
Company:
Date:
Project:
Location:
1. Baseflow
A) Is the permanent pool established by groundwater?
2. Surcharge Volume
A) Effective Imperviousness of Tributary Area, Ia
Ia = 54.6 %
B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.546
C) Contributing Watershed Area Area = 9.770 ac
D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in
Runoff Producing Storm
E) Design Concept
(Select EURV when also designing for flood control)
F) Water Quality Capture Volume (WQCV) Design Volume VWQCV
= 0.161 ac-ft
Based on 24-hour Drain Time
(VWQCV = (0.9 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12 * Area)
G) For Watersheds Outside of the Denver Region, VWQCV OTHER
= ac-ft
Water Quality Capture Volume (WQCV) Design Volume
(VWQCV OTHER = (d
6*(VWQCV
/0.43))
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER
= ac-ft
(Only if a different WQCV Design Volume is desired)
I) Predominant Watershed NRCS Soil Group
WQCV selected. Soil group not required.
J) Excess Urban Runoff Volume (EURV) Design Volume
For HSG A: EURVA = 1.68 * i
1.28
For HSG B: EURVB = 1.36 * i
1.08
For HSG C/D: EURVC/D = 1.20 * i
1.08
EURV = ac-f t
3. Depth of Surcharge WQCV DWQCV
= 1.0 ft
(Should not exceed 2 feet, required even if EURV is chosen)
4. Basin Shape L : W = 4.0 : 1
(It is recommended to have a basin length to width ratio between 2:1 and 4:1)
5. Permanent Pool
A) Minimum Permanent Pool Volume VPOOL
= 0.120 ac-ft
6. Side Slopes
A) Maximum Side Slope Above the Safety Wetland Bench Z = 4.00 ft / ft
(Horiz. dist. per unit vertical, should be no steeper than 4:1)
7. Inlet
A) Describe means of providing energy dissipation at concentrated
inflow locations:
DAP
TST, Inc. Consulting Engineers
Project:
Basin ID:
Design Information (Input):
Width of Basin Bottom, W = ft Right Triangle OR…
Length of Basin Bottom, L = ft Isosceles Triangle OR…
Dam Side-slope (H:V), Zd = ft/ft Rectangle OR…
Circle / Ellipse OR…
Irregular X (Use Overide values in cells G32:G52)
MINOR MAJOR
Storage Requirement from Sheet 'Modified FAA': acre-ft.
Stage-Storage Relationship: Storage Requirement from Sheet 'Hydrograph': acre-ft.
Storage Requirement from Sheet 'Full-Spectrum': acre-ft.
Labels Water Side Basin Basin Surface Surface Volume Surface Volume Target Volumes
for WQCV, Minor, Surface Slope Width at Length at Area at Area at Below Area at Below for WQCV, Minor,
& Major Storage Elevation (H:V) Stage Stage Stage Stage Stage Stage Stage & Major Storage
Stages ft ft/ft ft ft ft
2
ft
2
User ft
3
acres acre-ft Volumes
(input) (input) Below El. (output) (output) (output) Overide (output) (output) (output) (for goal seek)
4842.00 (input) 15,391 0 0.353 0.000
4843.00 4.00 0.00 0.00 18,220 16,806 0.418 0.386
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Project:
Basin ID:
STAGE-STORAGE SIZING FOR DETENTION BASINS
4842.00
4842.20
4842.40
4842.60
4842.80
4843.00
4843.20
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Stage (ft. elev.)
Storage (acre-feet)
STAGE-STORAGE CURVE FOR THE POND
UD Detention Pond A PermPool VolCalc, Basin 9/27/2016, 10:19 AM
H23 Preliminary Drainage Report
Detention Requirements Pond B - Major Storm (100-yr)
Mass Balance Method
0.78
1.88 cfs
11.40 acres
Detention
Requirements 2.27 acre-feet
City of Fort Collins
criteria (120%) 2.73 acre-feet
Time (min) Intensity (in/hr) Qin (cfs) Volume
in (ft
3
) Qout
(cfs) Volumeout
(ft
3
) Volume detained
(acre-feet)
5 9.95 88.475 26,542.62 1.88 564 0.596
10 7.72 68.646 41,187.74 1.88 1,129 0.920
15 6.52 57.976 52,178.26 1.88 1,693 1.159
20 5.60 49.795 59,754.24 1.88 2,257 1.320
25 4.98 44.282 66,423.24 1.88 2,822 1.460
30 4.52 40.192 72,345.31 1.88 3,386 1.583
35 4.08 36.279 76,186.66 1.88 3,950 1.658
40 3.74 33.256 79,814.59 1.88 4,514 1.729
45 3.46 30.766 83,069.06 1.88 5,079 1.790
50 3.23 28.721 86,163.48 1.88 5,643 1.848
55 3.03 26.943 88,911.11 1.88 6,207 1.899
60 2.86 25.431 91,552.03 1.88 6,772 1.946
65 2.70 24.008 93,632.76 1.88 7,336 1.981
70 2.60 23.119 97,100.64 1.88 7,900 2.048
75 2.50 22.230 100,035.00 1.88 8,465 2.102
80 2.40 21.341 102,435.84 1.88 9,029 2.144
85 2.30 20.452 104,303.16 1.88 9,593 2.174
90 2.20 19.562 105,636.96 1.88 10,157 2.192
100 2.05 18.229 109,371.60 1.88 11,286 2.252
110 1.90 16.895 111,505.68 1.88 12,415 2.275
120 1.75 15.561 112,039.20 1.88 13,543 2.261
130 1.60 14.227 110,972.16 1.88 14,672 2.211
140 1.40 12.449 104,569.92 1.88 15,800 2.038
150 1.20 10.670 96,033.60 1.88 16,929 1.816
160 1.15 10.226 98,167.68 1.88 18,058 1.839
170 1.10 9.781 99,768.24 1.88 19,186 1.850
180 1.05 9.337 100,835.28 1.88 20,315 1.848
Runoff Coefficient, C =
2-yr Release, Qout =
Area =
Appendix F
Project:
Basin ID:
Design Information (Input):
Width of Basin Bottom, W = ft Right Triangle OR…
Length of Basin Bottom, L = ft Isosceles Triangle OR…
Dam Side-slope (H:V), Zd = ft/ft Rectangle OR…
Circle / Ellipse OR…
Irregular X (Use Overide values in cells G32:G52)
MINOR MAJOR
Storage Requirement from Sheet 'Modified FAA': acre-ft.
Stage-Storage Relationship: Storage Requirement from Sheet 'Hydrograph': acre-ft.
Storage Requirement from Sheet 'Full-Spectrum': acre-ft.
Labels Water Side Basin Basin Surface Surface Volume Surface Volume Target Volumes
for WQCV, Minor, Surface Slope Width at Length at Area at Area at Below Area at Below for WQCV, Minor,
& Major Storage Elevation (H:V) Stage Stage Stage Stage Stage Stage Stage & Major Storage
Stages ft ft/ft ft ft ft
2
ft
2
User ft
3
acres acre-ft Volumes
(input) (input) Below El. (output) (output) (output) Overide (output) (output) (output) (for goal seek)
4839.00 (input) 8,417 0 0.193 0.000
4840.00 4.00 0.00 0.00 10,896 9,657 0.250 0.222
4841.00 4.00 0.00 0.00 13,604 21,907 0.312 0.503
4842.00 4.00 0.00 0.00 16,778 37,098 0.385 0.852
4843.00 4.00 0.00 0.00 20,071 55,522 0.461 1.275
4844.00 4.00 0.00 0.00 23,406 77,261 0.537 1.774
4845.00 4.00 0.00 0.00 27,602 102,765 0.634 2.359
4846.00 4.00 0.00 0.00 32,629 132,880 0.749 3.051
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Project:
Basin ID:
STAGE-STORAGE SIZING FOR DETENTION BASINS
4839.00
4840.00
4841.00
4842.00
4843.00
4844.00
4845.00
4846.00
4847.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
Stage (ft. elev.)
Storage (acre-feet)
STAGE-STORAGE CURVE FOR THE POND
UD Detention Pond B VolCalc, Basin 9/27/2016, 10:21 AM
Sheet 1 of 3
Designer:
Company:
Date:
Project:
Location:
1. Baseflow
A) Is the permanent pool established by groundwater?
2. Surcharge Volume
A) Effective Imperviousness of Tributary Area, Ia
Ia = 56.1 %
B) Tributary Area's Imperviousness Ratio (i = Ia / 100 ) i = 0.561
C) Contributing Watershed Area Area = 11.400 ac
D) For Watersheds Outside of the Denver Region, Depth of Average d6 = in
Runoff Producing Storm
E) Design Concept
(Select EURV when also designing for flood control)
F) Water Quality Capture Volume (WQCV) Design Volume VWQCV
= 0.191 ac-ft
Based on 24-hour Drain Time
(VWQCV = (0.9 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12 * Area)
G) For Watersheds Outside of the Denver Region, VWQCV OTHER
= ac-ft
Water Quality Capture Volume (WQCV) Design Volume
(VWQCV OTHER = (d
6*(VWQCV
/0.43))
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER
= ac-ft
(Only if a different WQCV Design Volume is desired)
I) Predominant Watershed NRCS Soil Group
WQCV selected. Soil group not required.
J) Excess Urban Runoff Volume (EURV) Design Volume
For HSG A: EURVA = 1.68 * i
1.28
For HSG B: EURVB = 1.36 * i
1.08
For HSG C/D: EURVC/D = 1.20 * i
1.08
EURV = ac-f t
3. Depth of Surcharge WQCV DWQCV
= 1.0 ft
(Should not exceed 2 feet, required even if EURV is chosen)
4. Basin Shape L : W = 4.0 : 1
(It is recommended to have a basin length to width ratio between 2:1 and 4:1)
5. Permanent Pool
A) Minimum Permanent Pool Volume VPOOL
= 0.143 ac-ft
6. Side Slopes
A) Maximum Side Slope Above the Safety Wetland Bench Z = 4.00 ft / ft
(Horiz. dist. per unit vertical, should be no steeper than 4:1)
7. Inlet
A) Describe means of providing energy dissipation at concentrated
inflow locations:
DAP
TST, Inc. Consulting Engineers
Project:
Basin ID:
Design Information (Input):
Width of Basin Bottom, W = ft Right Triangle OR…
Length of Basin Bottom, L = ft Isosceles Triangle OR…
Dam Side-slope (H:V), Zd = ft/ft Rectangle OR…
Circle / Ellipse OR…
Irregular X (Use Overide values in cells G32:G52)
MINOR MAJOR
Storage Requirement from Sheet 'Modified FAA': acre-ft.
Stage-Storage Relationship: Storage Requirement from Sheet 'Hydrograph': acre-ft.
Storage Requirement from Sheet 'Full-Spectrum': acre-ft.
Labels Water Side Basin Basin Surface Surface Volume Surface Volume Target Volumes
for WQCV, Minor, Surface Slope Width at Length at Area at Area at Below Area at Below for WQCV, Minor,
& Major Storage Elevation (H:V) Stage Stage Stage Stage Stage Stage Stage & Major Storage
Stages ft ft/ft ft ft ft
2
ft
2
User ft
3
acres acre-ft Volumes
(input) (input) Below El. (output) (output) (output) Overide (output) (output) (output) (for goal seek)
4838.00 (input) 6,220 0 0.143 0.000
4839.00 4.00 0.00 0.00 8,417 7,319 0.193 0.168
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Project:
Basin ID:
STAGE-STORAGE SIZING FOR DETENTION BASINS
4838.00
4838.20
4838.40
4838.60
4838.80
4839.00
4839.20
0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18
Stage (ft. elev.)
Storage (acre-feet)
STAGE-STORAGE CURVE FOR THE POND
UD Detention Pond B PermPool VolCalc, Basin 9/27/2016, 10:19 AM
APPENDIX G
FIRM Maps and
Original Floodplain Workmap
Page 1 of 5 Issue Date: August 1, 2014 Effective Date: December 15, 2014 Case No.: LOMR-APP
14-08-0580P
Washington, D.C. 20472
Federal Emergency Management Agency
LETTER OF MAP REVISION
DETERMINATION DOCUMENT
COMMUNITY AND REVISION INFORMATION PROJECT DESCRIPTION
COMMUNITY
APPROXIMATE LATITUDE & LONGITUDE: 40.518, -104.995
SOURCE: USGS QUADRANGLE DATUM: NAD 83
City of Fort Collins
Larimer County
Colorado
COMMUNITY NO.: 080102
BASIS OF REQUEST
IDENTIFIER
NO PROJECT UPDATE
Cache La Poudre River I-25 Divided Flow Path
ANNOTATED MAPPING ENCLOSURES ANNOTATED STUDY ENCLOSURES
TYPE: FIRM* NO.: 08069C0994F DATE: December 19, 2006
TYPE: FIRM* NO.: 08069C1013F DATE: December 19, 2006
DATE OF EFFECTIVE FLOOD INSURANCE STUDY:
Enclosures reflect changes to flooding sources affected by this revision.
* FIRM - Flood Insurance Rate Map; ** FBFM - Flood Boundary and Floodway Map; *** FHBM - Flood Hazard Boundary Map
FLOODING SOURCE(S) & REVISED REACH(ES)
Cache La Poudre River I-25 Divided Flow Path - from approximately 110 feet downstream of County Road 36 to approximately 140 feet upstream of County Road 38
SUMMARY OF REVISIONS
Flooding Source Effective Flooding Revised Flooding Increases Decreases
Cache La Poudre River I-25 Divided Flow Path Zone AE Zone AE YES YES
Zone X (shaded) Zone X (shaded) YES YES
Floodway Floodway YES YES
* BFEs - Base Flood Elevations
DETERMINATION
This document provides the determination from the Department of Homeland Security's Federal Emergency Management Agency (FEMA) regarding
a request for a Letter of Map Revision (LOMR) for the area described above. Using the information submitted, we have determined that a revision to
the flood hazards depicted in the Flood Insurance Study (FIS) report and/or National Flood Insurance Program (NFIP) map is warranted. This
document revises the effective NFIP map, as indicated in the attached documentation. Please use the enclosed annotated map panels revised by
this LOMR for floodplain management purposes and for all flood insurance policies and renewals in your community.
This determination is based on the flood data presently available. The enclosed documents provide additional information regarding this determination. If you have any
questions about this document, please contact the FEMA Map Information eXchange toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC
Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFIP is available on our website at http://www.fema.gov/nfip.
132942 PT202.BKR.14080580P.H20 102-I-C
Luis Rodriguez, P.E., Chief
Engineering Management Branch
Federal Insurance and Mitigation Administration
FLOODWAY DATA TABLE: 4
February 06, 2013
Page 2 of 5 Issue Date: Effective Date: Case No.: 14-08-0580P LOMR-APP
Washington, D.C. 20472
Issue Date: August 1, 2014 Effective Date: December 15, 2014
Federal Emergency Management Agency
LETTER OF MAP REVISION
DETERMINATION DOCUMENT (CONTINUED)
OTHER COMMUNITIES AFFECTED BY THIS REVISION
CID Number: 080101 Name: Larimer County, Colorado
AFFECTED MAP PANELS AFFECTED PORTIONS OF THE FLOOD INSURANCE STUDY REPORT
DATE OF EFFECTIVE FLOOD INSURANCE STUDY
FLOODWAY DATA TABLE: 4
TYPE: FIRM*
TYPE: FIRM*
NO.: 08069C0994F
NO.: 08069C1013F
DATE: December 19, 2006
DATE: December 19, 2006
This determination is based on the flood data presently available. The enclosed documents provide additional information regarding this determination. If you have any
questions about this document, please contact the FEMA Map Information eXchange toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC
Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFIP is available on our website at http://www.fema.gov/nfip.
132942 PT202.BKR.14080580P.H20 102-I-C
Luis Rodriguez, P.E., Chief
Engineering Management Branch
Federal Insurance and Mitigation Administration
: February 6, 2013
Page 3 of 5 Issue Date: Effective Date: Case No.: 14-08-0580P LOMR-APP
Washington, D.C. 20472
Issue Date: August 1, 2014 Effective Date: December 15, 2014
Federal Emergency Management Agency
LETTER OF MAP REVISION
DETERMINATION DOCUMENT (CONTINUED)
COMMUNITY INFORMATION
APPLICABLE NFIP REGULATIONS/COMMUNITY OBLIGATION
We have made this determination pursuant to Section 206 of the Flood Disaster Protection Act of 1973 (P.L. 93-234) and in accordance with
the National Flood Insurance Act of 1968, as amended (Title XIII of the Housing and Urban Development Act of 1968, P.L. 90-448),
42 U.S.C. 4001-4128, and 44 CFR Part 65. Pursuant to Section 1361 of the National Flood Insurance Act of 1968, as amended,
communities participating in the NFIP are required to adopt and enforce floodplain management regulations that meet or exceed NFIP
criteria. These criteria, including adoption of the FIS report and FIRM, and the modifications made by this LOMR, are the minimum
requirements for continued NFIP participation and do not supersede more stringent State/Commonwealth or local requirements to which the
regulations apply.
We provide the floodway designation to your community as a tool to regulate floodplain development. Therefore, the floodway revision
we have described in this letter, while acceptable to us, must also be acceptable to your community and adopted by appropriate community
action, as specified in Paragraph 60.3(d) of the NFIP regulations.
COMMUNITY REMINDERS
We based this determination on the base (1-percent-annual-chance) flood discharges computed in the FIS for your community without
considering subsequent changes in watershed characteristics that could increase flood discharges. Future development of projects
upstream could cause increased flood discharges, which could cause increased flood hazards. A comprehensive restudy of your
community’s flood hazards would consider the cumulative effects of development on flood discharges subsequent to the publication of the
FIS report for your community and could, therefore, establish greater flood hazards in this area.
Your community must regulate all proposed floodplain development and ensure that permits required by Federal and/or
State/Commonwealth law have been obtained. State/Commonwealth or community officials, based on knowledge of local conditions and
in the interest of safety, may set higher standards for construction or may limit development in floodplain areas. If your
State/Commonwealth or community has adopted more restrictive or comprehensive floodplain management criteria, those criteria take
precedence over the minimum NFIP requirements.
We will not print and distribute this LOMR to primary users, such as local insurance agents or mortgage lenders; instead, the community
will serve as a repository for the new data. We encourage you to disseminate the information in this LOMR by preparing a news release for
publication in your community's newspaper that describes the revision and explains how your community will provide the data and help
interpret the NFIP maps. In that way, interested persons, such as property owners, insurance agents, and mortgage lenders, can benefit
from the information.
This determination is based on the flood data presently available. The enclosed documents provide additional information regarding this determination. If you have any
questions about this document, please contact the FEMA Map Information eXchange toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC
Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFIP is available on our website at http://www.fema.gov/nfip.
132942 PT202.BKR.14080580P.H20 102-I-C
Luis Rodriguez, P.E., Chief
Engineering Management Branch
Federal Insurance and Mitigation Administration
Page 4 of 5 Issue Date: Effective Date: Case No.: 14-08-0580P LOMR-APP
Washington, D.C. 20472
Issue Date: August 1, 2014 Effective Date: December 15, 2014
Federal Emergency Management Agency
LETTER OF MAP REVISION
DETERMINATION DOCUMENT (CONTINUED)
COMMUNITY INFORMATION (CONTINUED)
We have designated a Consultation Coordination Officer (CCO) to assist your community. The CCO will be the primary liaison between
your community and FEMA. For information regarding your CCO, please contact:
Ms. Jeanine D. Petterson
Director, Mitigation Division
Federal Emergency Management Agency, Region VIII
Denver Federal Center, Building 710
P.O. Box 25267
Denver, CO 80225-0267
(303) 235-4830
STATUS OF THE COMMUNITY NFIP MAPS
We will not physically revise and republish the FIRM and FIS report for your community to reflect the modifications made by this LOMR
at this time. When changes to the previously cited FIRM panel(s) and FIS report warrant physical revision and republication in the future,
we will incorporate the modifications made by this LOMR at that time.
This determination is based on the flood data presently available. The enclosed documents provide additional information regarding this determination. If you have any
questions about this document, please contact the FEMA Map Information eXchange toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC
Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFIP is available on our website at http://www.fema.gov/nfip.
132942 PT202.BKR.14080580P.H20 102-I-C
Luis Rodriguez, P.E., Chief
Engineering Management Branch
Federal Insurance and Mitigation Administration
Page 5 of 5 Issue Date: Effective Date: Case No.: 14-08-0580P LOMR-APP
Washington, D.C. 20472
Issue Date: August 1, 2014 Effective Date: December 15, 2014
Federal Emergency Management Agency
LETTER OF MAP REVISION
DETERMINATION DOCUMENT (CONTINUED)
COMMUNITY INFORMATION (CONTINUED)
A notice of changes will be published in the Federal Register. This information also will be published in your local newspaper on or about
the dates listed below and through FEMA’s Flood Hazard Mapping website at https://www.floodmaps.fema.gov/fhm/Scripts/bfe_main.asp.
LOCAL NEWSPAPER Name: The Fort Collins Coloradoan
Dates: August 8, 2014 and August 15, 2014
Within 90 days of the second publication in the local newspaper, a citizen may request that we reconsider this determination. Any request
for reconsideration must be based on scientific or technical data. Therefore, this letter will be effective only after the 90-day appeal period
has elapsed and we have resolved any appeals that we receive during this appeal period. Until this LOMR is effective, the revised flood
hazard determination information presented in this LOMR may be changed.
This determination is based on the flood data presently available. The enclosed documents provide additional information regarding this determination. If you have any
questions about this document, please contact the FEMA Map Information eXchange toll free at 1-877-336-2627 (1-877-FEMA MAP) or by letter addressed to the LOMC
Clearinghouse, 847 South Pickett Street, Alexandria, VA 22304-4605. Additional Information about the NFIP is available on our website at http://www.fema.gov/nfip.
132942 PT202.BKR.14080580P.H20 102-I-C
Luis Rodriguez, P.E., Chief
Engineering Management Branch
Federal Insurance and Mitigation Administration
15,100 3,600 11,992 1.3 4,820.7 4,820.7 4,821.4 0.7
18,988 901 2,871 1.6 4,826.7 4,826.7 4,827.6 0.9
C 20,738 385 446 6.0 4,833.5 4,833.5 4,833.9 0.4
D 21,993 1,011 1,277 2.1 4,836.7 4,836.7 4,837.7 1.0
E 23,278 1,004 4,622 1.0 4,837.1 4,837.1 4,838.0 0.9
F 24,268 1,000 3,848 1.2 4,837.3 4,837.3 4,838.2 0.9
G 24,993 900 890 5.3 4,841.1 4,841.1 4,841.3 0.2
H 25,893 1,000 3,163 1.5 4,842.2 4,842.2 4,843.2 1.0
I 27,193 700 1,154 4.1 4,843.9 4,843.9 4,844.7 0.8
J 27,903 600 726 6.5 4,849.9 4,849.9 4,850.4 0.5
K 29,603 796 3,402 1.4 4,850.3 4,850.3 4,851.3 1.0
L 30,103 451 692 6.8 4,853.3 4,853.3 4,853.6 0.3
1 Feet above Larimer-Weld County Line Road
FEDERAL EMERGENCY MANAGEMENT AGENCY
LARIMER COUNTY, CO
AND INCORPORATED AREAS
CACHE LA POUDRE
RIVER - I-25 DIVIDED
FLOW
TABLE 4
FLOODWAY
1-PERCENT ANNUAL CHANCE FLOOD
WATER SURFACE ELEVATION
FLOODWAY DATA
CACHE LA POUDRE RIVER -
INTERSTATE HIGHWAY 25 DIVIDED FLOW
FLOODING SOURCE
A
B
CROSS SECTION DISTANCE1 WIDTH
(FEET)
SECTION
AREA
(SQUARE
FEET)
MEAN
VELOCITY
(FEET PER
SECOND)
REGULATORY
(NAVD 88)
INCREASE
(FEET)
WITHOUT
FLOODWAY
(FEET NAVD)
WITH
FLOODWAY
(NAVD 88)
REVISED
DATA
REVISED
DATA
4834
4831
4832
FLOODING I-25 DIVIDED EFFECTS FLOW
CHACHE LA POUDRE RIVER
c7
STAR GAZER DRIVE
ECLIPSE LANE
OBSERVATORY DRIVE
SOUTHERN CROSS
LANE
ROCK CREEK DRIVE
STEELHEAD STREET
PRECISION DRIVE
,
,
,
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BROOKFIELD DRIVE
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BYREVISED AREA LOMR DATED
NOVEMBER 2008 14,
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748 Whalers Way, Suite 200 Fort Collins, CO 80525 ideas@tstinc.com
970.226.0557 main 303.595.9103 metro 970.226.0204 fax www.tstinc.com
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PONDS DRIVE
COUNTY
ROAD 36 ROAD
Fort City Collins of
080102
Timnath Town of
080005
Town 080005 of Timnath
Unincorporated Larimer County Areas
080101
FRONTAGE INTERSTATE ROAD 25
c
38
Cache I-La 25 Divided Poudre River
Flow Path
T. 7 N.
T. 6 N.
La Cache Poudre
River
BoxelderDitch
Profile Baseline
NOTE: IS LOCATED MAP AREA WITHIN SHOWN TOWNSHIP ON THIS 6 NORTH PANEL
RANGE RANGE 68 68 WEST WEST. AND TOWNSHIP 7 NORTH
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Fossil Creek
Reservoir Inlet
HARMONY ROAD
SCALE
Map Projection:
NAD83 STATE PLANE Colorado North FIPS 0501 (Feet)
1 inch = 500 feet 1:6,000
Western Hemisphere; Vertical Datum: NAVD88
0 250000 500 1,Feet
0 75 150 300 Meters
NATIONAL FLOODPROGRAM INSURANCE FLOOD INSURANCE RATE MAP
AndCOLORADO LARIMER Incorporated COUNTY, Areas
PANEL 1013 OF 1420
Panel Contains:
COMMUNITY NUMBER PANEL SUFFIX
1013
1013
1013
F
F
F
FORT CITY OF COLLINS,
LARIMER COUNTY
TIMNATH, OF TOWN
080102
080101
080005
MAP NUMBER
MAP REVISED
08069C1013F
DECEMBER 19, 2006
VERSION N1U.MBER1.1.0
SPECIAL HAZARD FLOOD AREAS
OTHER FLOOD AREAS HAZARD OF
Without Base Flood Elevation (BFE)
With BFE or Depth
Regulatory Floodway
0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas
depth areas of less less than than one one foot square or with mile drainage
Future Chance Conditions Flood Hazard 1% Annual
Area SeeLevee Notes. with Reduced Flood Risk due to
Zone A,V, A99 Zone AE, AO, AH, VE, AR
Zone X
Zone X
Zone X
4849.9
4850
ZONE AE
Fossil Creek Reservoir Inlet
ZONE AE
REAVRIESAED
NOTE: IS LOCATED MAP AREA WITHIN SHOWN TOWNSHIP ON THIS 6 NORTH, PANEL
RANGE RANGE 68 68 WEST WEST. AND TOWNSHIP 7 NORTH,
City of 080102 Fort Collins
Unincorporated Larimer County Areas
080101
9 10
33 34
3
4
c36
City of 080102 Fort Collins
T. T. 7 6 N. N.
H
ARMONY ROAD
SCALE
Map Projection:
NAD83 STATE PLANE Colorado North FIPS 0501 (Feet)
1 inch = 500 feet 1:6,000
Western Hemisphere; Vertical Datum: NAVD88
0 250000 500 1,Feet
0 75 150 300 Meters
NATIONAL FLOODPROGRAM INSURANCE FLOOD INSURANCE RATE MAP
AndCOLORADO LARIMER Incorporated COUNTY, Areas
PANEL 994 OF 1420
Panel Contains:
COMMUNITY NUMBER PANEL SUFFIX
0994
0994
F
F
FORT CITY OF COLLINS,
LARIMER COUNTY
080102
080101
MAP NUMBER
MAP REVISED
08069C0994F
DECEMBER 19, 2006
VERSION N1U.MBER1.1.0
SPECIAL HAZARD FLOOD AREAS
OTHER FLOOD AREAS HAZARD OF
Without Base Flood Elevation (BFE)
With BFE or Depth
Regulatory Floodway
0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas
depth areas of less less than than one one foot square or with mile drainage
Future Chance Conditions Flood Hazard 1% Annual
Area SeeLevee Notes. with Reduced Flood Risk due to
Zone A,V, A99 Zone AE, AO, AH, VE, AR
Zone X
Zone X
Zone X
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
STAGE-STORAGE SIZING FOR DETENTION BASINS
H23
Check Basin Shape
Pond B CWP Permanent Pool Volume
UD Detention Pond B PermPool VolCalc, Basin 9/27/2016, 10:19 AM
SW Corner of Harmony Road and Strauss Cabin Road
September 27, 2016
H23 - Pond B
Design Procedure Form: Constructed Wetland Pond (CWP)
Riprap Pads
Choose One
Excess Urban Runoff Volume (EURV)
Choose One
A
B
C / D
Water Quality Capture Volume (WQCV)
Choose One
YES
NO
UD-BMP_v3.05 - H23 Pond B, CWP 9/27/2016, 1:52 PM
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
STAGE-STORAGE SIZING FOR DETENTION BASINS
H23
Check Basin Shape
Pond B
UD Detention Pond B VolCalc, Basin 9/27/2016, 10:21 AM
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
STAGE-STORAGE SIZING FOR DETENTION BASINS
H23
Check Basin Shape
Pond A CWP Permanent Pool Volume
UD Detention Pond A PermPool VolCalc, Basin 9/27/2016, 10:19 AM
SW Corner of Harmony Road and Strauss Cabin Road
September 27, 2016
H23 - Pond A
Design Procedure Form: Constructed Wetland Pond (CWP)
Concrete forebays and riprap pads
Choose One
Excess Urban Runoff Volume (EURV)
Choose One
A
B
C / D
Water Quality Capture Volume (WQCV)
Choose One
YES
NO
UD-BMP_v3.05 - H23 Pond A, CWP 9/27/2016, 1:52 PM
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
#N/A #N/A
STAGE-STORAGE SIZING FOR DETENTION BASINS
H23
Check Basin Shape
Pond A
UD Detention Pond A VolCalc, Basin 9/27/2016, 10:20 AM
From the City of Fort Collins Storm Drainage Design Criteria and Construction Standards
Appendix A
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