HomeMy WebLinkAboutPARADIGM - OVERALL DEVELOPMENT PLAN - ODP170004 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPrepared For:
Paradigm Properties, LLC
2186 Knoll Drive
Ventura, CA 93003
Prepared By
Coffey Engineering & Surveying
4045 St. Cloud Drive, Suite 180
Loveland, CO 80538
970-622-2095
Project No. 2276.00
October 17, 2017
DRAINAGE REPORT
PARADIGM ODP
FORT COLLINS, CO 80525
PAGE | 1
Paradigm ODP
ODP DRAINAGE REPORT
ENGINEER’S CERTIFICATION
I hereby certify that this Overall Development Plan Drainage Report for the design of stormwater
management facilities for the Paradigm ODP was prepared by me, or under my direct
supervision, in accordance with the provisions of the City of Fort Collins Stormwater Criteria
Manual for the owners thereof.
Troy Campbell, PE
Registered Professional Engineer
State of Colorado No. 41159
PAGE | 2
I. Table of Contents
I. GENERAL LOCATION AND EXISTING SITE INFORMATION ........ 3
II. MAJOR DRAINAGE BASIN INFORMATION ........................................ 4
III. Floodplain information .................................................................................. 4
IV. Proposed drainage facilities ........................................................................... 4
V. REFERENCES ............................................................................................... 5
VI. APPENDICES
A. Hydrologic Computations
FEMA Firm Panel 08069C1003E
NRSC Soil Map
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table 3.2-1 Zoning Classification - Runoff Coefficients
Table 4.1-2 Land Use - Percent Impervious
Rational Method Calculated Composite C Tables
Rational Method Calculated Imperviousness
Rational Method Calculated Flows
B. Hydraulic Computations
Preliminary Modified FAA Method
C. Map Pocket
Drainage Plan
PAGE | 3
I. GENERAL LOCATION AND EXISTING SITE INFORMATION
The Overall Development Plan Drainage Report serves as the summary of the hydrologic design
for parcels 8722200013 and 8722200025. The site is located in the NW 1/4 Section 22 Township
07N Range 68W of the 6
th
Principal Meridian in the City of Fort Collins, Larimer County,
Colorado. More specifically the site is bound by the I-25 exit ramp to the west, Prospect Road to
the north, and I-25 Frontage Road to the south and east.
The site is currently used for agricultural purposes, but is zoned as General Commercial. An
existing recreational vehicle dealership is located to the east. An existing motorcycle dealership
and repair shop is located to the southwest. A proposed development to the north of Prospect
Road will likely consist of commercial, light industrial, and affordable housing. Land to the
south and southeast is currently used for agriculture and agriculture related businesses.
According to the NRCS soils map survey, the native soils consist of Nunn Clay Loam (Type
“C”) soils. These soils have a moderately low infiltration rate when thoroughly wet.
The site is not located within any of the 12 Fort Collins major drainage basins according to the
City of Fort Collins Master Drainage Plan, but runoff drains into the Cooper Slough/Boxelder
Basin. This basin is bound by I-25 at Prospect Road. The site is currently a vacant lot covered
with native vegetation. Historically, the site drains south/southwest at an approximate slope of
0.5% until it crosses under I-25, and flows west into an existing detention pond. There are no
existing drainage facilities on site. There are small irrigation laterals on site formerly used for
agricultural purposes.
PAGE | 4
II. MAJOR DRAINAGE BASIN INFORMATION
The site is currently not in any Fort Collins Major Drainage Basin, but drains into the lower
portion of the Cooper Slough/Boxelder Drainage Basin. The Boxelder Creek and Cooper Slough
Basin encompass approximately 265 square miles, beginning north of the Colorado/Wyoming
border and extending southward into east Fort Collins, where it ends at the Cache la Poudre
River. The basin is primarily characterized by farmland with isolated areas of mixed-use
residential development and limited commercial development. It is anticipated the lower part of
the basin will undergo urbanization in the future. Recently, a series of 4’ X 12’ box culverts were
constructed under Prospect Road at Boxelder Creek just west of I-25, but no master planning
improvements are proposed for this site. The Lake Canal is located east of the site, but the
proposed drainage improvements will not influence irrigation facilities.
III. FLOODPLAIN INFORMATION
The site is located in the FEMA Flood Panel 08069C1003G, and is within FEMA Flood Zone
AE. Boxelder Stormwater Authority obtained a Conditional Letter of Map Revision (CLOMR)
and are currently constructing a large regional detention pond and unplugging existing culverts
under I-25. The goal of these construction projects is to remove a large section of developable
land, including the subject property owned by Paradigm Properties, from the Boxelder Creek
Floodplain. Once construction is complete and approved, Federal Emergency Management
Authority (FEMA) would need to approve a Letter of Map Revision (LOMR) before the site is
officially removed from the floodplain. Boxelder Stormwater Authority expects FEMA to
approve the LOMR. The site is not located within any City of Fort Collins floodplain.
IV. PROPOSED DRAINAGE FACILITIES
The proposed drainage patterns will generally match existing drainage patterns, flowing north to
south. A portion of the site will be detained off-site in an existing detention pond southwest of
the site. There are existing drainage easements to allow this off-site detention. The remaining
runoff will be detained in a proposed detention pond in the southwest corner of the site. From the
detention pond, runoff flows south through a series of culverts and grass channels under I-25 and
into the off-site detention pond. The northern portion of the site reaches the proposed detention
pond through overland flow and channelized flow via culverts and swales. The southern portion
of the site will flow into the on-site detention pond via sheet and channelized flow. The portion
of flow detained in the off-site pond will either bypass the on-site pond or overflow the on-site
pond through a spillway.
According to Table 3.2-1 Zoning Classification – Runoff Coefficients, the “C” value for
Commercial zoning is 0.85. From Table 4.1-2 Land Use – Percent Impervious, Commercial
PAGE | 5
zoning has an assumed percent impervious of 80%. There are no anticipated off-site flows
running onto the site. From the assumed runoff coefficient and percent impervious an
approximate required detention volume can be calculated. Using the 100-year storm from the
City of Fort Collins Rainfall Intensity-Duration-Frequency Table and the Modified FAA Method
the approximate detention volume required is 4.21 acre-ft (200,000 ft
3
). There is an off-site
detention pond that was sized to detain 2.14 acre-feet of runoff from the 100-year event for this
site. Approximately 2.07 acre-feet (90,000 ft
3
) of on-site detention is required. The pond will
have a release rate of the 2-year historic event of approximately 5.61 cfs.
Low Impact Development (LID) requirements area required on all new or redeveloping property,
which includes sites required to be brought into compliance with the Land Use Code. These
require a higher degree of water quality treatment with one of the two following options:
a. 50% of the newly added or modified impervious area must be treated by LID techniques
and 25% of new paved areas must be pervious.
b. 75% of all newly added or modified impervious area must be treated by LID techniques,
The four-step process will be used to achieve this goal. Some common LID techniques will be
used, including; constructing a wetland detention pond, and a wetland channel/bioswale to
convey runoff to the pond. Also, a vegetative buffer will be incorporated to prevent continuous
impervious area to run into the pond. Individual lots will use techniques such as permeable
pavers, sand filters, rain gardens, or tree filters before directing runoff to the regional detention
pond.
V. REFERENCES
“City of Fort Collins Stormwater Criteria Manual”, City of Fort Collins, Adopted December
2011.
Urban Storm Drainage Criteria Manual, Volumes 1, 2, and 3, Urban Drainage and Flood Control
District, April 2008.
SITE
1
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
9/22/2017
Page 1 of 3
4490300 4490360 4490420 4490480 4490540 4490600 4490660
4490300 4490360 4490420 4490480 4490540 4490600 4490660
499850 499910 499970 500030 500090 500150 500210 500270 500330 500390
499850 499910 499970 500030 500090 500150 500210 500270 500330 500390
40° 34' 0'' N
105° 0' 6'' W
40° 34' 0'' N
104° 59' 42'' W
40° 33' 48'' N
105° 0' 6'' W
40° 33' 48'' N
104° 59' 42'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 35 70 140 210
Meters
Map Scale: 1:2,560 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
2
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
76 Nunn clay loam, wet, 1 to 3
percent slopes
15.6 100.0%
Totals for Area of Interest 15.6 100.0%
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
9/22/2017
Page 3 of 3
4
5
6
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
Table 3.2-1. Zoning Classification - Runoff Coefficients
7
Land Use Percent Impervious (%)
Residential
Urban Estate 30
Low Density 50
Medium Density 70
High Density 90
Commercial
Commercial 80
Industrial 90
Undeveloped
Open Lands, Transition 20
Greenbelts, Agriculture 2
Offsite Flow Analysis (when
Land Use not defined)
45
Table 4.2-2. Land Use - Percent Impervious
8
Composite C Values
I-25 Prospect
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Pavers (acres) Lawns (acres) Total Area Minor (2-YR) Major (100-YR)
(C = 0.95) (C = 0.95) (C = 0.50) (C = 0.50) (C = 0.10) (acres) Composite "C" Composite "C" (Cf x C)
E1 E1 0.00 0.00 0.00 0.00 0.00 16.910 0.15 0.19
D1 P1 0.00 0.000 0.00 0.000 0.000 8.720 0.85 1.00
D2 P2 0.00 0.000 0.00 0.000 0.000 8.190 0.85 1.00
Total - 0.00 0.000 0.00 0.000 0.000 16.910 0.85 1.00
Notes:
Runoff Coefficients per Table 3.2-1 - Zoning Classification
Major Storm Runoff factored per Table R0-12
Developed
Design Point Basin(s)
Existing
MAP Rational Method.xlsx 9/26/2017
9
Impeviousness
I-25 Prospect
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Pavers (acres) Lawns (acres) Total Area Percent
(I = 100) (I = 100) (I = 40) (I = 50) (I = 0) (acres) Imperviousness
E1 E1 0.00 0.00 0.000 0.00 0.00 16.9100 2%
D1 P1 0.00 0.000 0.00 0.000 0.000 8.720 80%
D2 P2 0.00 0.000 0.00 0.000 0.000 8.190 80%
Total - 0.00 0.000 0.00 0.000 0.000 16.910 80%
Notes:
Percent Impervious Table 4.1-2
Design Point Basin (s)
Existing
Developed
CAG Rational Method.xlsx 9/26/2017
10
Preliminary Basin Flow Calculations
I-25 Prospect
Area Minor Major
(acres) Composite "C" Composite "C" Length (ft) Slope (%)
Minor tov
(min)
a
Major tov
(min)
a Length (ft)
Slope
(%)
Channel
Type
Velocity
(fps)c tt (min)
Minor TC
(min)
Major TC (min) 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr
E1 E1 16.9100 0.15 0.19 1000 0.50 70.78 67.99 0 0.60 PA 1.55 0.00 10.00 10.00 2.21 3.78 7.72 5.61 9.59 24.48
D1 P1 8.7200 0.85 1.00 1000 2.00 11.73 4.69 750 1.00 PA 2.00 6.2500 17.98 10.94 1.70 2.90 7.42 12.60 21.49 64.70
D2 P2 8.1900 0.85 1.00 1000 2.00 11.73 4.69 750 1.00 PA 2.00 6.2500 17.98 10.94 1.70 2.90 7.42 11.83 20.19 60.77
Total - 16.9100 0.85 1.00 2000 2.00 16.59 6.64 1500 1.00 PA 2.00 12.5000 29.09 19.14 1.32 2.25 5.75 18.97 32.34 97.23
Notes:
a
b HM = Heavy Meadow, TF = Tillage/field, PL = Short pasture and lawns, BG = Nearly bare ground, GW = Grassed Waterway, PA = Paved Areas
c Velocity alues from Figure 3-3/Table RO-2 Estimate of Average Flow Velocity for use with the Rational Method
Design
Point
Developed
Existing
Initial/Overland Time Final TC Intensity (in/hr) Basin Flows (cfs)
Basin (s)
Travel Time
1 / 3
1 . 87 ( 1 . 1 ) 1 / 2
S
CC D
t f
ov
−
=
CAG 10/17/2017
11 11
Ex-Pr Difference 9/26/2017
Project: Paradigm Properties
Location: I-25 & Prospect
Fort Collins, Colorado
Project Number:2276.00
Date: 9/26/2017
PROPOSED ft3
acre-ft.
'C' value 0.85 183631.7 4.2156
'C' * 1.25 1
Area 16.91 acres
Release Rate 5.61
DETENTION POND SIZING (100-Year)
TIME TIME INTENSITY Q 100 Runoff Release Required Required
cum 100 year Volume Cum total Detention Detention
(mins) (secs) (in/hr) (cfs) (ft^3) (ft^3) (ft^3) (ac-ft)
0 0 0 0.00 0 0.0 0.0 0.0000
5 300 9.950 168.25 50476.35 1683.0 48793.4 1.1201
10 600 7.720 130.55 78327.12 3366.0 74961.1 1.7209
15 900 6.520 110.25 99227.88 5049.0 94178.9 2.1620
20 1200 5.600 94.70 113635.2 6732.0 106903.2 2.4542
25 1500 4.980 84.21 126317.7 8415.0 117902.7 2.7067
30 1800 4.520 76.43 137579.8 10098.0 127481.8 2.9266
35 2100 4.080 68.99 144884.9 11781.0 133103.9 3.0556
40 2400 3.740 63.24 151784.2 13464.0 138320.2 3.1754
45 2700 3.460 58.51 157973.2 15147.0 142826.2 3.2788
50 3000 3.230 54.62 163857.9 16830.0 147027.9 3.3753
55 3300 3.030 51.24 169083.1 18513.0 150570.1 3.4566
60 3600 2.860 48.36 174105.4 20196.0 153909.4 3.5333
65 3900 2.720 46.00 179381.3 21879.0 157502.3 3.6158
70 4200 2.590 43.80 183947 23562.0 160385.0 3.6819
75 4500 2.480 41.94 188715.6 25245.0 163470.6 3.7528
80 4800 2.380 40.25 193179.8 26928.0 166251.8 3.8166
85 5100 2.290 38.72 197491.9 28611.0 168880.9 3.8770
90 5400 2.210 37.37 201803.9 30294.0 171509.9 3.9373
95 5700 2.130 36.02 205304.3 31977.0 173327.3 3.9790
100 6000 2.060 34.83 209007.6 33660.0 175347.6 4.0254
105 6300 2.000 33.82 213066 35343.0 177723.0 4.0800
110 6600 1.940 32.81 216515.6 37026.0 179489.6 4.1205
115 6900 1.890 31.96 220523.3 38709.0 181814.3 4.1739
120 7200 1.840 31.11 224023.7 40392.0 183631.7 4.2156 100-Year Volume
125 7500 1.790 30.27 227016.8 42075.0 184941.8 4.2457
130 7800 1.750 29.59 230821.5 43758.0 187063.5 4.2944
135 8100 1.710 28.92 234220.4 45441.0 188779.4 4.3338
140 8400 1.670 28.24 237213.5 47124.0 190089.5 4.3639
145 8700 1.630 27.56 239800.7 48807.0 190993.7 4.3846
150 9000 1.600 27.06 243504 50490.0 193014.0 4.4310
155 9300 1.570 26.55 246902.9 52173.0 194729.9 4.4704
160 9600 1.540 26.04 249997.4 53856.0 196141.4 4.5028
165 9900 1.510 25.53 252787.6 55539.0 197248.6 4.5282
170 10200 1.480 25.03 255273.4 57222.0 198051.4 4.5466
175 10500 1.450 24.52 257454.8 58905.0 198549.8 4.5581
180 10800 1.420 24.01 259331.8 60588.0 198743.8 4.5625
185 11100 1.400 23.67 262781.4 62271.0 200510.4 4.6031
190 11400 1.380 23.34 266028.1 63954.0 202074.1 4.6390
195 11700 1.360 23.00 269071.9 65637.0 203434.9 4.6702
200 12000 1.340 22.66 271912.8 67320.0 204592.8 4.6968
205 12300 1.320 22.32 274550.8 69003.0 205547.8 4.7187
210 12600 1.300 21.98 276985.8 70686.0 206299.8 4.7360
Required detention
EAST PROSPECT ROAD
FRONTAGE ROAD
INTERSTATE 25 - OFF RAMP
PROPOSED ROAD
PROPOSED ROAD
FRONTAGE ROAD
N
1
OVERALL DRAINAGE EXHIBIT RJP
CJD
DP1
LEGEND:
SURVEY & CONTROL NOTES
OVERALL DEVELOPMENT PLANS FOR
PARADIGM ODP
ENGINEERING & SURVEYING
4045 St. Cloud Drive, Suite 180
Loveland, CO 80538
[P] 970-622-2095 [F] 307-742-7403
NW
1
4 OF SECTION 22, T7N, R68W, 6TH P.M., CITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADO
DRAWING NO.
1
NOT FOR CONSTRUCTION
PRELIMINARY
NO. REVISION DATE
SHEET NO.
OF
PROJECT:
DATE:
DESIGNER:
DRAFTER:
CHECKED BY:
APPROVED BY:
Know what's below.
Call before you dig.
R
2276.00
10/17/17
TWC
TWC
NOTES:
Basin Runoff Summary
Page 1
12
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 11, Sep 23, 2016
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2015—Oct
15, 2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
9/22/2017
Page 2 of 3
3