HomeMy WebLinkAboutNE PROSPECT & I-25 ODP - MA210006 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORT
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March 3, 2021
Mr. Shane Boyle
Fort Collins Utilities
700 Wood Street
Fort Collins, Colorado 80524
RE: PROSPECT/I-25 ODP FIRST AMENDMENT
PROJECT NUMBER: 1489-001
Dear Mr. Boyle:
This letter report accompanies the submittal for the Rudolph Farms Overall Development Plan (ODP). Specifically,
this letter report serves to document the overall drainage impacts associated with the proposed Rudolph Farms
Development.
The proposed development site is located northeast of the I-25/Prospect Road interchange in Fort Collins,
Colorado. The site is situated along Prospect Road, just east of the I-25/Prospect Road Interchange, and just west
of the Poudre School District Middle/High School development. The overall Rudolph Farms site is roughly 116
acres in size.
Zoning across the site includes Industrial (I), Commercial (C), and Urban Estate (UE). The east I -25 Frontage Road
access, from Prospect Road to the northwest corner of the development, will be abandoned as part of the
Colorado Department of Transportation North I-25 Express Lanes improvement project. The vacated right-of-way
for the east I-25 Frontage Road access is to be included as part of this Overall Development Plan. The extension of
Carriage Parkway from Fox Groves to Prospect Road is proposed as part of this project.
Southwest Corner of the Site:
The southwest corner of the proposed development site is in Basin SB-3 of the Town of Timnath Master Drainage
Plan. Detention requirements are determined from the Town of Timnath Master Drainage plan, and the detention
volumes will meet the following criteria:
• The historic 10-year release rate during a 100-year event.
• The historic 2-year release rate during a 2-year event.
The Town of Timnath prefers full spectrum detention unless required per the Town of Timnath Master Drainage
Plan. No SWMM modeling has been done at the present. SWMM modeling will be conducted at Project
Development Plan submittal to verify detention volumes and viability of full spectrum detention. The current
submittal does show proposed on-site detention proportioned to the respective basin in the Town of Timnath
Master Drainage Plan.
The outfall for the southwest corner of the site is a proposed 36” culvert underneath Prospect Road. The culvert
will be installed as part of the Colorado Department of Transportation North I-25 Express Lanes improvement
project as a replacement to an existing culvert prior to construction. The existing culvert is shown in Figure 1. A
detention pond, per the City of Fort Collins stormwater regulations, will be constructed upstream of the 36”
culvert as part of this project. The detention will be sized per the SWMM model during the Project Development
Plan submittal.
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Southeast Corner of the Site:
The southeast corner of the proposed development site is in Basin SB-6 of the Town of Timnath Master Drainage
Plan. Detention requirements are determined from the Town of Timnath Master Drainage plan, and the detention
volumes will meet the following criteria:
• The historic 10-year release rate during a 100-year event.
• The historic 2-year release rate during a 2-year event.
Figure 1: Existing culvert prior to CDOT intersection improvements.
Figure 2: Location photograph of existing culvert.
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The Town of Timnath prefers full spectrum detention unless required per the Town of Timnath Master Drainage
Plan. No SWMM modeling has been done at the present. SWMM modeling will be conducted at Project
Development Plan submittal to verify detention volumes and viability of full spectrum detention. The current
submittal does show proposed on-site detention proportioned to the respective basin in the Town of Timnath
Master Drainage Plan.
The outfall for the southeast corner of the site is Lake Canal. The development will be required to provide a
between the owner of the Lake Canal to discharge developed drainage into Lake Canal. Developed drainage will
be routed through water quality and detention pond prior to release into Lake Canal.
North Half of the Site:
The north half of the proposed development is in Basins SB-2 and SB-5 of the Town of Timnath Master Drainage
Plan. Basins SB-2 and SB-5 historically drain into the Timnath Reservoir Inlet Canal (TRIC). Detention
requirements for the Town of Timnath are to meet the following criteria:
• The historic 10-year release rate during a 100-year event.
• The historic 2-year release rate during a 2-year event.
According to the Town of Timnath Master Plan, the historic 10-year release rate is more the restrictive of the two
Town of Timnath requirements. The SWMM model for the Town of Timnath Master Plan assumes the historic 10-
year release rate will be conveyed by TRIC to the Timnath Reservoir.
According to the Town of Timnath Master Drainage Plan, TRIC will overflow at two (2) locations on the project
site and three (3) downstream locations. Spill D, just north of County Road 42E, limits the capacity of TRIC to
190 cfs. Northern Engineering, as part of the drainage analysis for the Poudre School District Middle/High
School development, further analyzed the Poudre School District Middle/High School drainage analysis, studied
the irrigation flows and capacity of TRIC. Based on this analysis, the normal irrigation flows in TRIC are between
25-50 cfs from November to April to refill Timnath Reservoir and maximum flows of 100 cfs in the spring for no
more than a week. The Cache La Poudre Reservoir Canal, the operator for TRIC, has the option to increase
spring flows in TRIC to 150 cfs, but this only occurs if Timnath Reservoir is lower than expected and the winter
flows were deficient. The Poudre School District Middle/High School drainage analysis assumed 100 cfs of
irrigation flow within TRIC. The overspills are not necessary to preclude discharge into TRIC. The project will
comply with the 10-year historic release rate per the Town of Timnath Master Plan. An analysis of downstream
infrastructure is not part of this study.
Spills A and B are shown on the ODP Drainage Plan for reference. In order to provide the required detention,
bank improvements will be necessary at Spill A as part of this project. The banks of TRIC in the vicinity of Spill B
was improved as part of 2020 – 2021 construction projects. Improvements in the vicinity of Spill B included
raising the height of the south bank and installation of a box culvert along the north side of Prospect Road.
Therefore, improvements at Spill B will not be required by this project.
Therefore, detention for the north half of the site will be sized on the more conservative of the Town of Timnath
Master Drainage Plan and/or the capacity of TRIC assuming 100 cfs of irrigation. The Tow n of Timnath prefers
full spectrum detention unless required per the Town of Timnath Master Drainage Plan. No SWMM modeling has
been done at the present. SWMM modeling will be conducted at Project Development Plan submittal to verify
detention volumes and viability of full spectrum detention. The current submittal does show proposed on-site
detention proportioned to the respective basin in the Town of Timnath Master Drainage Plan.
Detention Volume, Water Quality, and LID:
Detention volumes and release rates shown on the Master Drainage Plan are based on the Town of Timnath
Master Plan 10-Year historic release per the respective basins. A percentage of each basin was determined from
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the respective basin in Town of Timnath Master Drainage Plan, and then the detention volume and release rates
were prorated from this percentage. The volume was then compared to the Urban Drainage Detention Basin
Volume Estimating Workbook, Version 2.33. The more constrictive volume is shown on the ODP Drainage Plan.
These detention volumes will be adjusted as the site further develops and proposed percent impervious are
further refined with Project Development Plan submittals.
The development will provide multiple onsite detention ponds. The multiple detention ponds will reduce the
need of a single, large regional detention pond, provide additional water quality treatment through a treatment
train, and enhanced landscaping per the City of Fort Collins Stormwater Criteria Manual. Water quality and LID
requirements will be provided with each respective Project Development Plan per the City of Fort Collins
Stormwater Criteria Manual.
Detention pond release rates and volumes will be determined per the Town of Timnath Master Drainage Plan. All
other stormwater requirements will be per the City of Fort Collins Stormwater Criteria Manual.
Floodplain:
The far northwest corner of the site is located within the existing Boxelder Creek Flood fringe and floodway. FEMA
FIRM Panel Number 08069C0984H and 08069C1003G for Larimer County, Dated May 2, 2012 is referenced in this
study. Base (100-year) flood elevations in the vicinity of the proposed project range from 4919.9 to 4920.7
(elevations referenced to the City of Fort Collins NAVD 88). Please see th e attached FIRMette and City Floodplain
Mapping exhibits.
A CLOMR has been submitted to FEMA and was approved for the Boxelder 6 CLOMR prepared for Boxelder Basin
Regional Stormwater Authority (Case Number 15-08-0329R). Improvements include an overflow channels, box
culverts, dams, and bridge replacement. These improvements are proposed to remove much of this property
from the flood fringe and floodway. Limits for both the existing FEMA Floodway/Floodplain and the proposed
Floodplain/Floodway are shown on the Master Drainage Plan. These master plans were prepar ed utilizing the
proposed floodplain/floodway. Most of the development will avoid the proposed floodplain/floodway limits per
the Boxelder 6 CLOMR revisions.
It is acknowledged that any improvements located within the Boxelder Creek floodplain and floodway must
satisfy the standards of Chapter 10 of City Code; and final design documents will be completed accordingly. Any
development within the Boxelder Creek floodplain will be required to provide a City of Fort Collins floodplain use
permit prior to construction. Any development with the Boxelder Creek floodway will be required to provide a
City of Fort Collins no-rise certification prior to construction.
Offsite Flows:
Offsite flows, except those identified as part of the Boxelder Creek floodplain and floodway, are not expected to
impact this site. However, further analysis will be required during Project Development Plan to ensure there are
no offsite stormwater impacts from Fox Grove, Kitchell Subdivision, and Poudre School District Middle/High
School developments. Offsite flows will be passed through the site without providing any detrimental impact to
the development and downstream users.
In summary, this Overall Drainage Report letter adequately addresses any potential stormwater changes
associated with the proposed Overall Development Plan Amendment. In general, there are no significant changes
proposed at a major drainage level. The ODP complies with the governing City of Fort Collins Master Drainage
Plans, and the previously approved drainage plans specific for the subject property
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Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Frederick S. Wegert, PE
Project Engineer
Attachments: Excerpts from Boxelder 6 CLOMR; FEMA Firmette; City of Fort Collins Flood Risk Map; City of Fort
Collins Stormwater Manual Table 3.2-1; Town of Timnath Master Drainage Plan SWMM Subbasin Map –
Developed Condition; Excerpts from Town of Timnath SWMM Model; Town of Timnath TRIC Spill Map; Northern
Engineering TRIC Irrigation Flows Memo; Calculation of Detention Volumes and Release Rates; Sheet 76 from
CDOT North I-25 Express Lanes – Prospect Road – Drainage Plan
National Flood Hazard Layer FIRMette
0 500 1,000 1,500 2,000250
Feet
Ü
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
SPECIAL FLOOD
HAZARD AREAS
Without Base Flood Elevation (BFE)
Zone A, V, A99
With BFE or DepthZone AE, AO, AH, VE, AR
Regulatory Floodway
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 mileZone X
Future Conditions 1% Annual
Chance Flood HazardZone X
Area with Reduced Flood Risk due to
Levee. See Notes.Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood HazardZone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This map complies with FEMA's standards for the use of
digital flood maps if it is not void as described below.
The basemap shown complies with FEMA's basemap
accuracy standards
The flood hazard information is derived directly from the
authoritative NFHL web services provided by FEMA. This map
was exported on 1/25/2021 at 4:16 PM and does not
reflect changes or amendments subsequent to this date and
time. The NFHL and effective information may change or
become superseded by new data over time.
This map image is void if the one or more of the following map
elements do not appear: basemap imagery, flood zone labels,
legend, scale bar, map creation date, community identifiers,
FIRM panel number, and FIRM effective date. Map images for
unmapped and unmodernized areas cannot be used for
regulatory purposes.
Legend
OTHER AREAS OF
FLOOD HAZARD
OTHER AREAS
GENERAL
STRUCTURES
OTHER
FEATURES
MAP PANELS
8
B 20.2
The pin displayed on the map is an approximate
point selected by the user and does not represent
an authoritative property location.
1:6,000
105°0'11"W 40°34'28"N
104°59'34"W 40°34'N
Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020
INTERSTATE 25E PROSPECT RDSE FRONTAGE RDSW FRONTAGE RDQUEST DR
FOX GROVE DR
OFF RAMPVIXEN DRCARRIAGE PKW YHUNTSMAN DR TOD DRROLLINS DEN DRSMITHFIELD DR KIT DEN DR
INTERSTATE 25Printed: 11/16/2020.
All floodplain boundaries are approximate.
This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information.
FEMA Flood Risk Map
Moderate Risk
May include:- Areas of FEMA 500-year floodplain (FEMA Zone X-shaded).- Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot.- Areas protected by levees from the 100-year flood.Low Risk
Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist.
FEMA Flood Fringe - May Include:- Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH)- Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet.There is a 1% annual chance that these areas will be flooded.
High Risk
FEMA Floodway - Area of 100-year floodplain with greatest depths and fastest velocities.
Erosion Buffer Limits
0 240 480 720 960120
Feet
PROSPECT & I-25 ODP
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.2 Runoff Coefficients
Page 4
3.2 Runoff Coefficients
Runoff coefficients used for the Rational Method are determined based on either overall land use or
surface type across the drainage area. For Overall Drainage Plan (ODP) submittals, when surface types
may not yet be known, land use shall be used to estimate flow rates and volumes. Table 3.2-1 lists the
runoff coefficients for common types of land uses in the City.
Table 3.2-1. Zoning Classification - Runoff Coefficients
Land Use Runoff Coefficient (C)
Residential
Urban Estate 0.30
Low Density 0.55
Medium Density 0.65
High Density 0.85
Commercial
Commercial 0.85
Industrial 0.95
Undeveloped
Open Lands, Transition 0.20
Greenbelts, Agriculture 0.20
Reference: For further guidance regarding zoning classifications, refer to the Land Use
Code, Article 4.
For a Project Development Plan (PDP) or Final Plan (FP) submittals, runoff coefficients must be based on
the proposed land surface types. Since the actual runoff coefficients may be different from those
specified in Table 3.2-1, Table 3.2-2 lists coefficients for the specific types of land surfaces.
MAIN ST.COUNTY ROAD 5HIGHWAY 14
Downtown Timnath AreaSee Map B-5 MATCHLINE - SEE SHEET B-2TIMNATHRESERVOIR
E C
E MULBERRY ST
E COUNTY ROAD 40E HORSETOOTH RD
E PROSPECT RD
INTERSTATE 25!(SB 1251047 ac.43%
!(SB 1263423 ac.15%
!(SB 2634 ac.66%
!(SB 2733 ac.20%
!(SB 2835 ac.20%
!(SB 3145 ac.25%
!(SB 309 ac.30%!(SB 2537 ac.15%
!(SB 3444 ac.61%
!(SB 432 ac.80%!(SB 732 ac.40%
!(SB 69 ac.90%
!(SB 337 ac.80%!(SB 15A43 ac.55%
!(SB 582 ac.55%
!(SB 237 ac.30%
!(SB 5A33 ac.15%
!(SB 1587 ac.20%
!(SB 1326 ac.38%!(SB 1643 ac.25%
!(SB 3256 ac.20%
!(SB 9143 ac.50%
!(SB 8197 ac.67%
!(SB 4A30 ac.70%
!(SB 1876 ac.51%
!(SB 1136 ac.39%
!(SB 1242 ac.44%
!(SB 10115 ac.55%
!(SB 14103 ac.33%
!(SB 1737 ac.45%
!(SB 2036 ac.40%!(SB 2154 ac.45%
!(SB 50A7 ac.50%
!(SB 506 ac.50%
!(SB 5214 ac.78%
!(SB 5121 ac.78%
!(SB 4884 ac.68%
!(SB 4932 ac.64%
!(SB 3310 ac.29%
!(SB 37117 ac.37%
!(SB 4420 ac.5%
!(SB 43A41 ac.44%!(SB 4656 ac.38%
!(SB 47A23 ac.43%
!(SB 4719 ac.34%!(SB 4566 ac.42%!(SB 7679 ac.35%!(SB 7928 ac.5%
!(SB 7872 ac.5%
!(SB 3948 ac.21%
!(SB 3582 ac.45%
!(SB 77A2 ac.10%!(SB 77B2 ac.10%!(SB 80B1 ac.10%!(SB 80A4 ac.10%
!(SB 808 ac.15%!(SB 72A5 ac.30%
!(SB 7288 ac.32%!(SB 6730 ac.49%
!(SB 6851 ac.36%
!(SB 7117 ac.30%
!(SB 1201225 ac.65%
!(SB 8145 ac.25%
!(SB 8221 ac.30%!(SB 82A16 ac.10%!(SB 82B3 ac.10%
!(SB 81A6 ac.30%
!(SB 77C9 ac.25%!(SB 77D27 ac.30%
!(SB 80D10 ac.10%
!(SB 80C10 ac.10%
!(SB 8449 ac.25%
!(SB 8449 ac.25%!(SB 82C8 ac.10%!(SB 82D109 ac.30%!(SB 7055 ac.50%!(SB 73159 ac.50%
!(SB 2247 ac.20%
!(SB 25A17 ac.10%
!(SB 2421 ac.15%
!(SB 2922 ac.20%
!(SB 267 ac.90%
!(SB 3866 ac.30%
!(SB 9A23 ac.25%
!(SB 21A77 ac.42%
!(SB 43107 ac.22%
!(SB 70A30 ac.67%
Timnath Drainage Master Plan 2018 Update
EXHIBIT B-1 - SWMM Subbasin MapDeveloped Condition - North Map
Legend
SWMM Subbasins Developed Imperv.
0 - 6%
7 - 20%
21 - 35%
36 - 50%
51 - 65%
66 - 80%
81 - 100%
SWMM Subbasin (Name, Area - Ac, % Imp.)
SWMM Routing Link q
600 Feet
File: F:\32-1881.00 Timnath Master Plan Update\GIS\MXD\AppendixMaps\AppB_Future\B-1 - FUT_BasinMap_North.mxd - Plot By: SimpsonM - Date: 8/21/2018
[SUBCATCHMENTS]Name RainGage Outlet Area Exist %Imperv Future Imperviousness Width Flow Length Slope Land Use Conversion2 RG1 53 67.09 2 90 9741 300 1Yes3 RG1 54 36.68 5 80 5326 300 1Yes4 RG1 117 32.45 20 80 4712 300 1Yes5 RG1 129 82.16 2 55 11930 300 1Yes6 RG1 133 8.54 2 90 1240 300 1Yes7 RG1 132 31.57 20 40 4584 300 1Yes8 RG1 134 197.45 5 67 28670 300 1Yes9 RG1 500 142.96 5 50 20758 300 1Yes10 RG1 138 115.38 12 55 16753 300 1Yes11 RG1 142 36.46 2 39 5294 300 1Yes12 RG1 143 41.68 5 44 6052 300 1Yes13 RG1 LAKECANAL2 26.3 20 38 3819 300 1Yes14 RG1 146 102.97 2 33 14951 300 1Yes15 RG1 149 86.87 5 20 12614 300 1Yes16 RG1 LAKECANAL3 42.8 25 25 6235 299 0.44 No17 RG1 153 37.16 2 45 5396 300 1Yes18 RG1 156 76.37 2 51 11089 300 1Yes20 RG1 159 36.41 12 40 5287 300 1Yes21 RG1 162 54.43 12 45 7903 300 1Yes22 RG1 164 47.17 20 20 7110 289 1.8 No23 RG1 165 7.37 30 30 642 500 0.54 No24 RG1 166 21.36 15 15 3101 300 1.86 No25 RG1 P‐25 36.96 15 15 3220 500 0.65 No26 RG1 169 33.5 10 66 4864 300 1Yes27 RG1 170 33.05 20 20 2879 500 0.43 No28 RG1 173 35.06 20 20 3054 500 1.73 No29 RG1 P‐29 22.18 20 20 1932 500 2.48 No30 RG1 177 9.32 5 30 1720 236 1.18Yes31 RG1 P‐31 45.38 25 25 4707 420 2.57 No32 RG1 LAKECANAL4 56.49 20 20 8202 300 0.57 No33 RG1 179 10.33 12 29 1500 300 1Yes34 RG1 180 44.49 10 61 6460 300 1.75Yes35 RG1 182 81.61 5 45 11850 300 1.5Yes37 RG1 187 117.18 5 37 17015 300 1Yes38 RG1 186 66.39 5 30 9640 300 1Yes39 RG1 TRIC6 47.66 5 21 6920 300 3Yes43 RG1 193 107.04 5 22 15542 300 1Yes44 RG1 LAKECANAL8 20.16 5 6 4391 200 5.8Yes45 RG1 199 65.97 2 42 9579 300 1.57Yes46 RG1 201 56.24 12 38 8166 300 1Yes47 RG1 LAKECANAL9 19.4 5 34 2817 300 6.64Yes48 RG1 204 84.49 5 68 12268 300 1Yes49 RG1 207 32.41 12 64 4706 300 1Yes50 RG1 P‐50 5.78 50 50 3187 79 0.72 No51 RG1 213 20.68 10 78 3003 300 1Yes52 RG1 216 14.31 20 78 2078 300 1Yes55 RG1 217 10.68 45 75 1551 300 1Yes57 RG1 DTN4 2.69 80 80 391 300 1Yes58 RG1 DTN6 1.11 50 80 322 150 1.15Yes59 RG1 DTN7 3.22 50 50 712 197 1Yes60 RG1 DTN7 1.38 50 56 707 85 1Yes61 RG1 220 2.51 40 70 547 200 1Yes62 RG1 DTN3 2.53 70 79 841 131 1Yes63 RG1 DTN6 0.91 50 80 551 72 1Yes64 RG1 221 2.17 50 77 722 131 1.56Yes65 RG1 DTN14 1.94 50 80 397 213 1.15YesFutureTable B‐1 ‐ SWMM Subbasin Parameters ‐ Future ConditionExisting ConditionF:\32‐1881.00 Timnath Master Plan Update\Hydrology\EPA SWMM\SWMM_Subbasin_Parameters.xlsx8/21/2018
2‐Yr 5‐Yr 10‐Yr 25‐Yr 50‐Yr 100‐Yr 2‐Yr 5‐Yr 10‐Yr 25‐Yr 50‐Yr 100‐Yr 2‐Yr 5‐Yr 10‐Yr 25‐Yr 50‐Yr 100‐Yr
2 L‐CP‐2 457122858 139206260352463607 234567
3 L‐CP‐3 579142134 70102129176233309 2457810
4 L‐CP‐4 17 24 30 41 55 76 62 91 114 155 204 272 10 15 18 22 27 32
5 L‐CP‐5 579173771 116167210290391534 124679
6 L‐CP‐6 011248 182633466078 011111
7 L‐CP‐7 17 24 30 42 57 81 34 48 60 84 116 162 7 11 14 19 25 32
8 L‐CP‐8 28 39 49 74 116 187 327 476 597 815 1,089 1,466 11 18 24 33 41 49
9 L‐CP‐9 20 29 35 53 83 137 186 267 333 454 613 842 7 12 16 23 30 37
10 L‐CP‐10 38 54 67 92 128 185 163 235 293 396 531 725 18 27 33 44 55 67
11 L‐CP‐11 23461327 38546792126176 112234
12 L‐CP‐12 6810162644 496986117158219 2346811
13 L‐CP‐13 15 21 26 37 53 77 27 38 48 67 93 130 6 10 12 16 21 27
14 L‐CP‐14 6810183878 93132163223309438 1236811
15 L‐CP‐15 12 17 22 34 57 96 49 69 85 123 179 269 2 3 5 12 17 22
16 ‐2941517097138 2941517097138 ‐‐‐‐‐‐
17 L‐CP‐17 23492245 446379107145201 112334
18 L‐CP‐18 468133163 101145181245330452 123568
20 L‐CP‐20 12 17 21 29 42 63 39 56 69 94 128 178 5 8 9 13 17 22
21 L‐CP‐21 18 25 31 43 60 86 65 93 115 156 211 292 6 11 14 19 25 32
22 ‐27384668103160 27384668103160 ‐‐‐‐‐‐
23 ‐5810131825 5810131825 ‐‐‐‐‐‐
24 ‐91316243761 91316243761 ‐‐‐‐‐‐
25 ‐152227375174 152227375174 ‐‐‐‐‐‐
26 L‐CP‐26 9 13 16 23 32 49 55 80 100 135 180 242 6 8 9 12 15 18
27 ‐172531425678 172531425678 ‐‐‐‐‐‐
28 ‐202834476697 202834476697 ‐‐‐‐‐‐
29 ‐121822304365 121822304365 ‐‐‐‐‐‐
30 L‐CP‐30 1224918 81114192740 011223
31 ‐32455680116171 32455680116171 ‐‐‐‐‐‐
32 ‐31445575106155 31445575106155 ‐‐‐‐‐‐
33 L‐CP‐33 35681218 81214202840 112356
34 L‐CP‐34 13 18 23 37 58 93 71 102 129 180 244 332 6 9 12 16 20 24
35 L‐CP‐35 12 16 22 40 70 125 99 141 178 251 346 482 4 7 10 14 18 22
37 L‐CP‐37 17 23 29 42 64 104 117 167 206 281 384 540 5 8 11 17 22 29
38 L‐CP‐38 9 13 16 24 36 59 55 78 96 131 182 261 3 5 6 10 13 17
39 L‐CP‐39 71012224483 29404975117184 1246912
43 L‐CP‐43 15 21 26 41 69 120 66 93 115 160 230 341 3 5 7 14 21 27
44 ‐346214379 346214379 ‐‐‐‐‐‐
45 L‐CP‐45 457204688 76107133185256360 123467
46 L‐CP‐46 19 26 32 45 63 92 58 82 102 140 193 271 6 9 13 19 26 33
47 L‐CP‐47 345163670 1926324770106 112345
48 L‐CP‐48 12 17 21 31 49 80 141 206 258 352 469 631 6 9 11 14 17 21
49 L‐CP‐49 11 15 19 26 37 55 52 75 94 127 169 229 5 8 10 12 15 19
50 ‐81214202942 81214202942 ‐‐‐‐‐‐
51 L‐CP‐51 34581221 38577196127170 223456
52 L‐CP‐52 81114192739 2739496789118 5 6 8101114
55 L‐CP‐55 12 17 21 29 39 53 19 28 36 48 64 85 7 10 12 15 18 22
57 ‐479121621 589131723 ‐‐‐‐‐‐
58 ‐223457 2346810 ‐‐‐‐‐‐
59 ‐468101420 468111420 ‐‐‐‐‐‐
60 ‐2335710 2345811 ‐‐‐‐‐‐
61 L‐CP‐61 3457913 578111520 122345
62 ‐578111520 5810131723 ‐‐‐‐‐‐
63 ‐122357 234579 ‐‐‐‐‐‐
64 L‐CP‐64 34571115 578111520 123345
65 ‐3456912 467101317 ‐‐‐‐‐‐
66 ‐45791217 6810141824 ‐‐‐‐‐‐
67 L‐CP‐67 22351224 38556994127174 111233
68 L‐CP‐68 345112446 507088123170240 112456
69 L‐CP‐69 23471633 72106133180239319 122334
70 L‐CP‐70 34592041 72103129175235323 123456
71 L‐CP‐71 23471529 142025355279 111235
72 L‐CP‐72 57103167124 78111139198282406 1235810
73 L‐CP‐73 9 13 17 32 70 134 207 298 373 515 698 959 4 7 8 11 14 17
74 ‐1825314672116 1825314672116 ‐‐‐‐‐‐
75 ‐2839486895135 2839486895135 ‐‐‐‐‐‐
76 L‐CP‐76 11 16 19 39 84 161 77 109 134 188 265 383 3 5 7 12 15 20
77 ‐33465886129198 33465886129198 ‐‐‐‐‐‐
78 ‐1015184193177 1015184193177 ‐‐‐‐‐‐
79 ‐467142954 467142954 ‐‐‐‐‐‐
80 ‐356111830 356111830 ‐‐‐‐‐‐
81 ‐32445581120180 32445581120180 ‐‐‐‐‐‐
82 ‐1825304568106 1825304568106 ‐‐‐‐‐‐
83 L‐CP‐83 10 14 18 30 52 91 128 187 235 321 427 573 6 8 10 13 16 19
84 ‐35496095160264 35496095160264 ‐‐‐‐‐‐
85 L‐CP‐85 20 28 34 50 77 125 195 282 351 475 637 870 7 12 16 22 28 35
86 ‐557897132181256 557897132181256 ‐‐‐‐‐‐
87 L‐CP‐87 11282039 2028354969100 111122
88 ‐93132163224307432 93132163224307432 ‐‐‐‐‐‐
89 L‐CP‐89 1114919 121721294161 011122
90 L‐CP‐90 345102552 476783113156221 112356
91 L‐CP‐91 23471119 32476081107142 123345
92 L‐CP‐92 81114223867 5884104141187249 35791114
93 L‐CP‐93 6810163471 131188234317426585 2346810
94 L‐CP‐94 467122552 86123153207280388 123568
95 ‐76108133183254361 76108133183254361 ‐‐‐‐‐‐
96 ‐356143160 356143160 ‐‐‐‐‐‐
97 ‐6085104148217325 6085104148217325 ‐‐‐‐‐‐
98 ‐6389110153213304 6389110153213304 ‐‐‐‐‐‐
99 L‐CP‐99 12251020 142025355073 011223
100 L‐CP‐100 6911172847 33465780112163 1226811
101 L‐CP‐101 578153469 99142176239324449 123579
102 L‐CP‐102 6810152441 517390122164226 2346810
103 ‐3043537297134 3043537297134 ‐‐‐‐‐‐
104 ‐86121150206284398 86121150206284398 ‐‐‐‐‐‐
105 ‐31455777103141 31455777103141 ‐‐‐‐‐‐
106 L‐CP‐106 71012193253 30435374103145 23471012
107 ‐6389110152211300 6389110152211300 ‐‐‐‐‐‐
108 L‐CP‐108 578121930 162329405577 122468
109 L‐CP‐109 91215213043 5682102139185247 34691214
110 L‐CP‐110 568121830 476987117156209 234568
112 ‐223479 223479 ‐‐‐‐‐‐
114 ‐568111522 568111522 ‐‐‐‐‐‐
119 ‐589131927 589131927 ‐‐‐‐‐‐
120 ‐1,144 1,796 2,331 3,237 4,328 5,829 1,277 2,049 2,691 3,774 5,073 6,847 ‐ ‐ ‐‐‐‐
121 L‐CP‐121 702 995 1,231 1,700 2,364 3,402 2,216 3,433 4,425 6,109 8,149 10,971 259 431 558 754 974 1,238
122 L‐CP‐122 43 59 73 122 231 465 640 992 1,278 1,765 2,354 3,170 21 30 36 47 59 72
123 L‐CP‐123 40 56 68 114 217 437 552 845 1,082 1,486 1,980 2,668 18 27 33 44 55 68
124 L‐CP‐124 93 130 160 267 506 1,019 1,454 2,265 2,929 4,053 5,411 7,285 36 61 76 103 130 159
125 L‐CP‐125 409 588 731 998 1,354 1,886 880 1,357 1,745 2,406 3,207 4,319 194 298 362 464 579 730
126 L‐CP‐126 935 1,325 1,639 2,263 3,148 4,530 1,336 1,920 2,389 3,261 4,424 6,163 203 337 465 753 1,112 1,641
130 ‐35681217 35681217 ‐‐‐‐‐‐
Future SWMM Model Results ‐ Concept Detention Discharge
Discharge (cfs)Subbasin
Concept
Detention
Outlet Link
Table B‐3 ‐ Subbasin Discharge Results
Existing SWMM Model Results ‐ Subbasin Discharge Future SWMM Model Results ‐ Subbasin Discharge
Discharge (cfs) Discharge (cfs)
F:\32‐1881.00 Timnath Master Plan Update\Hydrology\EPA SWMM\Results\Subbasin Results.xlsx 8/21/2018
TRIC SPILL B
TRIC SPILL C
TRIC SPILL D
TRIC SPILL E
TRIC
TRIC 100yr
Spill Boundary (E.C.)
Timnath
Reservoir
190
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TRIC SPILL A 350 cfs Max Capacity
275 c
fs
Max
Capac
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190 c
fs
Max
Capaci
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200 c
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Ma
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Capac
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Capacity:185cfs - Nort
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P
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S COUNTY ROAD 5CARRIAGE
PKWY
E PROSPECT RD
SW FRONTAGE
RDINTERSTATE 25SE FRONTAGE RD
SE FRON
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R
D
49144915.54914.549154913
4913.5
49124912.54910.77Timnath Reservoir Inlet Canal Spills Map
q
SRH-2D Model Results (Existing 100-year)
Document Path: F:\32-1881.00 Timnath Master Plan Update\GIS\MXD\TRIC Spills\TRIC Spills_100yr Existing.mxd Date: 8/21/2018MCLAUGHLIN LN.Legend
TRIC 100-year WSEL Contours (Existing)
TRIC 100-year Boundary (Existing)
850
Feet
Date: December 9, 2019
Project: Timnath Reservoir Inlet Canal Relocation Project No. 100-019
Fort Collins, Colorado
Re: TRIC Flow Depths Memo
To whom it may concern:
This memo is intended to document the conversations and design process regarding the design of the
Timnath Reservoir Inlet Canal (TRIC) box culvert and the associated pond design for the Poudre School
District site at the corner of Prospect Road and County Road 5 (Main Street) in Fort Collins.
Dale Trowbridge, the manager of the Cache La Poudre Reservoir Company and operator of the TRIC was
contacted to determine the irrigation flows that are present in the ditch during normal operations. The
TRIC runs off-season (November-April typically) to refill the Timnath Reservoir. In the conversation with
Dale, we were informed that normal flows are typically between 25-50 cfs. In the spring, there can be
flows of up to 100 cfs, but this flow is generally limited to no more than a week before reducing back to
normal flow rates. If needed, the flows in the ditch can be increased up to 150 cfs, but this only occurs if
the reservoir is lower than expected and the winter flows were deficient. In the event of a 150 cfs flow in
the ditch being needed for operations, it would only be at that flow for few days before decreasing again.
Please refer to the Drainage Letter Report for the Timnath Reservoir Inlet Canal (TRIC) Relocation dated
December 5, 2019 for information regarding ditch performance during storm events.
We took the flowrates provided by Dale and ran them through Hydraflow to determine the operational
water surface elevation in the box culvert under different conditions. It is worth noting that flap gates are
provided at the pond outlets and that ditch operations should not cause ponding in the ponds, regardless
of flow rate. Ponding would only occur if a rain or snow event were to occur while the higher operational
levels were present, thereby preventing the flap gates from opening and draining the ponds. The analysis,
illustrated in the TRIC Operational Flow Summary below, showed varying flow depths in the culvert which
have could different implications to the project, with the lower flows having no impact on the ponds and
the higher flows resulting in potential ponding within the ponds that would not be able to drain until flows
in the ditch subsided.
Using this analysis, it was decided that the optimal pond bottom elevation would be designed to minimize
ponding with the more common 100 cfs flow in mind. This results in a minimum pond bottom elevation
of 4911.0 that would see approximately three inches of ponding if a storm event were to occur the ditch
is running at that flow. The duration of the ponding would typically be for a few days, but no more than
a week. In the event that a storm event occurred while the ditch was flowing at the more unusual 150 cfs,
it is possible that the ponds would see up to 1.37’ of ponding that would not drain until the flow in the
ditch subsided. This condition was viewed as acceptable when balancing the relative infrequency of the
event (per Dale) and relatively short duration of the ponding against the significant reduction to site
earthwork and improved overall drainage performance that can be achieved by having a lower pond
bottom.
Page 2
TRIC Operational Flow Summary
Flow
(cfs)
Flow Depth in
Culvert* (ft)
WSEL
(ft)
Ponding**
(ft) Frequency/Duration
50 2.07 4909.97 0 Normal Winter Flow
100 3.35 4911.25 0.25 Spring Final Fill-up - Week Max
150 4.47 4912.37 1.37 Spring Pond top off on dry years - Few Days Max
*Connection 5 used, Inv=4907.9,
**Pond Bottom = 4911.0
Please do not hesitate to contact us if you have questions or require additional information.
Sincerely,
Andy Reese
Project Manager
Benjamin Ruch, PE
Project Engineer
Town
Basin
Percent
of Basin
10-Year
Release Rate
(cfs)
Detention
Volume
(ac-ft)
OP-1 20.79 85%SB-3 57%9.0 10.0 5.10 6.80
OP-2 5.63 85%SB-3 15%9.0 10.0 1.38 1.84
OP-3 6.09 95%SB-6 71%0.7 1.0 0.51 0.86
OP-4 4.32 95%SB-5 5%9.0 9.0 0.47 0.57
OP-5 68.18 95%SB-2 100%7.0 7.0 7.00 8.40
OP-6 10.47 30%SB-5 13%9.0 9.0 1.15 1.38
Detention Volumes and Release Rates
Per Town of Timnath Master Plan
Basin ID Area (ac.)Percent
Impervious
Calculated
Release
Rate
(cfs)
Calculated
Detention
Volume
(ac-ft)
W
WE
E
E
EW
WE
E
PROSPECT RD HCL
ROW
ROW
FES-II-2820-1D
FES-II-2822-1D
P-II-2822-1
FES-II-2820-1U
P-II-2820-1
FES-II-2822-2D
P-II-2822-2
IN-II-2822-2
IN-II-2822-1
LINE II-13
LINE II-12
LINE II-11
CH-II-2821-1EA
CH-II-2821-1EB
CH-II-2821-1EC
CH-II-2821-1ED
CH-II-2821-1EE
CH-II-2821-1EF
CH-II-2821-1EG
CH-II-2821-1EH
CH-II-2821-1EI
CH-II-2821-1EJ
CH-II-2821-1WA
CH-II-2821-1WB
CH-II-2821-1WC
CH-II-2821-1WD
CH-II-2821-1WE
CH-II-2821-1WF
CH-II-812J
CH-II-812K
CH-II-812L
CH-II-812M
CH-II-812N
CH-II-812O
CH-II-812P
CH-II-812Q CH-II-812R
CH-II-812S
CH-II-812T49054905
4905
49054910
4
9
1
049104910491049154915492049204925KEY MAP
PROSPECT RD
BOXELDER CREEK
SH 14
PORT OF ENTRY
12 14
13
2820+002825+002830+00FRONTAGE RDPROSPECT RD
DR-PLAN 14 15
J. Murray
J. Murray
PROSPECT RD
DRAINAGE PLANMATCH LINE STA 2819+00FRONTAGE RD10601 West 10th Street
Phone:
Greeley, CO 80634
(970)-350-2205 FAX: (970)339-9530
Colorado Department of Transportation
Region 4 SMR
Numbers
Structure
No Revisions:
Revised:
Void:Sheet Subset:
Detailer:
Designer:21506
IM 0253-255
Sheet NumberSubset Sheets:of
Init.CommentsDate:
Sheet Revisions As Constructed9/9/2019Print Date:
Horiz. Scale:1:100 Vert. Scale: As Noted
Project No./Code
File Name:
NORTH I-25 EXPRESS LANES
21506HYD_Plan-Prospect-S5M-PI.dgn
MurrayJ9/9/20191:29:43 PM01-PROSPECT-MAIN-03DGN MODEL:pw:\\rshpw01.rsandh.com:PW_RSH\Documents\Transportation\Projects\21506 - North I-25 (CDOT)\MIRA\SEG 5 Prospect Interchange\Hydraulics\Drawings\21506HYD_Plan-Prospect-S5M-PI.dgnNOTES:
100'0'50'200'
LEGEND:
INFORMATION REGARDING OUTFALL.
SEE HEADWALL DETAIL FOR 2
CONCRETE PIPE OF EQUIVALENT SIZE.
BE REPLACED WITH REINFORCED
ACCEPTABLE CONDITION, PIPE SHALL
VERIFIED. IF CONDITION IS NOT IN
EXISTING PIPE CONDITION SHALL BE 1
ULTIMATE CAN BE CONSTRUCTED.
DETERMINE TEMPORARY DRAINAGE UNTIL
CONFIGURATION. CONTRACTOR TO
3. DRAINAGE DESIGN REFLECTS ULTIMATE
SECTIONS FOR CHANNEL LININGS.
GEOMETRY. SEE DITCH TYPICAL
2. SEE DITCH TABLES FOR CHANNEL
FOR IRRIGATION REMOVAL INFORMATION.
OTHERWISE NOTED. SEE REMOVAL PLANS
BE PROTECTED IN PLACE UNLESS
1. ALL EXISTING DRAINAGE SYSTEMS TO
NOT FOR CONSTRUCTION
SHEET
PROFILE LINE ID STATION/OFFSET HCL ITEM LENGTH PAY DEPTH MISC NOTES
11
II-11
FES-II-2820-1D 2821+03.10, 130.93' RT.PROSPECT RD 36" RCES RIPRAP APRON D50=9" - SEE DRAINAGE DETAILS
P-II-2820-1 36" RCP 240'
FES-II-2820-1U 2821+06.36, 125.20' LT.PROSPECT RD 36" RCES
II-12
FES-II-2822-1D 2821+39.52, 125.92' RT.PROSPECT RD 18" RCES RIPRAP APRON D50=9" - SEE DRAINAGE DETAILS
P-II-2822-1 18" RCP 51'
IN-II-2822-1 2821+47.71, 65.50' RT.PROSPECT RD INLET TYPE R (L=10)10'
II-13
IN-II-2822-2 2821+47.55, 62.58' LT.PROSPECT RD INLET TYPE R (L=10)10'
P-II-2822-2 18" RCP 54'
FES-II-2822-2D 2821+47.14, 126.30' LT. PROSPECT RD 18" RCES RIPRAP APRON D50=9" - SEE DRAINAGE DETAILS
76