HomeMy WebLinkAboutCOUNTRY CLUB CORNERS SIXTH FILING (CARWASH) - FDP - FDP170012 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
March 29, 2017
Mr. Wes Lamarque
Fort Collins Utilities – Stormwater
700 Wood Street
Fort Collins, CO 80522
Re: Country Club Corners Sixth Filing – Lot 1
Final Storm Drainage Letter
Dear Wes,
Please accept the following letter describing the storm drainage intent demonstrating the proposed site
improvement’s ability to comply with the City’s stormwater requirements.
INTRODUCTION
The Country Club Corners Sixth Filing – Lot 1 proposes to construct a drive through carwash along with
the supporting utility infrastructure, site accesses (pedestrian/vehicular), along with modifying the
existing interim detention pond to accommodate the proposed improvements. The site is located within
the commercial plaza located in the southeast corner of N. College Ave (Hwy 287) and E. Willox Lane,
north of Bristlecone Dr, and west of Blue Spruce Drive. Lot 1 of Country Club Corners Sixth Filing is a
replat of Lot 8, Country Club Corners Third Filing PUD, and Lot 1, Country Club Corners Fifth Filing,
located in the Northwest Quarter Section 1, Township 7 North, Range 69 West of the 6th P.M., City of
Fort Collins, County of Larimer, State of Colorado. A vicinity map is attached for reference.
The carwash site is located with Lot 1 and the interim detention pond is proposed to be located within Lot
2 of Country Club Corners Sixth Filing. Lot 1 is approximately 1.09 acres, and Lot 2 is approximately
1.09 acres. A significant portion of both lots will be disturbed with the proposed improvements, for a
total disturbed area estimated at 2.18± acres. The proposed improvements will be completed in one phase
of construction.
EXISTING CONDITIONS
The project site is located within the Northeast College Corridor Outfall (NECCO) drainage basin and
detention is not required. An existing storm drainage infrastructure is described in the following drainage
reports and/or utility plans:
• Country Club Corners Third Filing P.U.D. (1995)
• Lot 3, Replat No. 1 of Country Club Corners Third Filing P.U.D. (1996)
• Country Club Corners Fourth Filing P.U.D. (1997)
• Country Club Corners Fifth Filing (2002)
The original drainage plan was established with the Country Club Corners Third Filing PUD. This filing
proposed that the storm drainage infrastructure be constructed in two phases, with the swale to Evergreen
Pond as the ultimate outfall for both phases. References are attached. Phase 1 established an interim
Country Club Corners Sixth Filing – Lot 1
Final Storm Drainage Letter
March 29, 2017
Page 2 of 4
detention pond with a temporary outfall pipe, and Phase 2 is to complete the storm drain outfall within
Bristlecone Dr to the Evergreen Pond swale. No dedicated onsite detention facilities are required with the
completion of Phase 2 of the storm drainage infrastructure. Phase 1 utilized a temporary 24” HDPE
outfall pipe and swale to drain the pond. The remaining filings listed above either modified the interim
detention pond or enclosed the temporary outfall swale in a pipe. The Phase 2 of the storm drain system
has not be completed. Unfortunately, no mechanism was established with the original PUD to complete
the extensive infrastructure needed to complete the drainage outfall. The last modification to the interim
detention pond is described within the Country Club Corners Fourth Filing PUD.
The project is not located within a FEMA mapped 100-yr floodplain.
PROPOSED DEVELOPMENT
The improvements associated with Lot 1 will consist of constructing a 4,680 sqft drive through carwash
with supporting utility infrastructure and pedestrian/vehicle accesses. The interim detention pond will be
reconfigured to accommodate the carwash improvements.
Without the completion of the originally proposed storm drain system, the interim detention pond will
need to remain and will be located within Lot 2 of the Country Club Corners Sixth Filing. At the time the
outfall is complete, dedicated onsite detention facilities are not required. To determine the appropriate
detention volume required, the basins draining to the interim pond were reanalyzed with the current
rainfall depths along with confirming the ponds release rate. The capacity of the existing 30” RCP within
Bristlecone Dr limits the pond release rate. The pond was originally designed with a 6.60 cfs release rate
based on the available capacity of 25 cfs within the 30” RCP determined within the Country Club Corners
Third Filing PUD drainage report. Reanalyzing the existing 30” RCP and allowing the energy grade line
(EGL) to be 1.0’ below the roadway surface, the pipe capacity was confirmed to allow 26.18 cfs. The
street capacity of Bristlecone Dr was also confirmed for reference. Based on these capacities, the pond
release rate could be increased to 7.78 cfs. The pond is designed with a a release rate of 7.78 cfs,
requiring 2.27 acre-ft of storage.
To accommodate the carwash improvements, the portion of the existing storm drain within Lot 1 will be
realigned. Storm drain sizing calculations are provide with reference to the Country Club Corners Third
Filing PUD drainage report for offsite flows.
The project is required to implement Low Impact Development (LID) techniques to provide water quality
enhancement. A bioretention rain garden is proposed to treat at least 75% of the proposed impervious
area.
There is some offsite drainage from the west that sheet flows to the carwash site. These flows will be
directed to the interim detention pond without being conveyed to the proposed rain garden utilizing a curb
cut near the carwash entrance. Approximately 2,250 sqft of the private drive along the east of the site
drains to the rain garden. The remaining eastern private drive that drains to the carwash site is conveyed
to the interim detention pond through a combination of curb cuts and a swale.
The carwash site is divided into 3 basins:
Basin 101 consists of majority of the site improvements. This basin drains to and is treated by the rain
garden along the eastern property line. The basin is approximately 0.82 acres and is 71.2% impervious
with an estimated 100-yr runoff rate of 6.86 cfs. Runoff from the rain garden is directed to the relocated
36” storm drain along the eastern property line than to the interim detention pond.
Country Club Corners Sixth Filing – Lot 1
Final Storm Drainage Letter
March 29, 2017
Page 3 of 4
Basin 102 consist of the proposed carwash building and the carwash entry/exit drives. This basin is
approximately 0.19 acres and is 68.5% impervious with an estimated 100-yr runoff rate of 1.75 cfs.
Runoff from the basin in collected by a series of area inlets and directed to the storm drain manhole
proposed to be located north of the carwash building.
Basing 103 consist of the west portion of Lot 1 that is not conveyed to the rain garden. This basin is
approximately 0.09 acres and is 43.4% impervious with an estimated 100-yr runoff rate of 0.56 cfs.
Runoff from this basin is directed to the interim detention pond via surface from and a curb cut in the
carwash site entry drive.
All calculations and exhibits are attached for reference.
LOW IMPACT DEVELOPMENT TECHNIQUES
In reference to the code requirements for implementation of Low Impact Development (LID) techniques,
the use of a bioretention rain garden is necessary to satisfy these requirements. The rain garden will
promote infiltration while capturing fine sediment that drains off of the impervious areas. A Standard
Operations Procedure will be provided at final design to assist in ensuring that these BMPs will
adequately perform over time.
Below is a description of the 4 step process for selecting structural BMPs:
Urban Drainage and Flood Control District (UDFCD) recommends a Four Step Process for receiving
water protection that focuses on reducing runoff volumes, treating the water quality capture volume
(WQCV), stabilizing drainageways and implementing long-term source controls. The Four Step Process
applies to the management of smaller, frequently occurring events.
Step 1: Employ Runoff Reduction Practices
To reduce runoff peaks, volumes, and pollutant loads from urbanizing areas, implement Low Impact
Development (LID) strategies, including Minimizing Directly Connected Impervious Areas (MDCIA).
Runoff throughout the site is mainly conveyed to the rain garden via overland sheet flow, curb & gutter,
and drain pans. The rain garden will slow runoff, promote infiltration, and filter runoff prior to being
released into the adjacent storm drain system.
Step 2: Implement BMPs that Provide a Water Quality Capture Volume with Slow Release
The rain garden is designed to provide water quality capture volume per Urban Drainage’s
recommendations and calculations. The captured runoff is design for a 12-hr drain time.
Step 3: Stabilize Drainageways
Natural Drainageways are subject to bed and bank erosion due to increases in frequency, duration, rate
and volume of runoff during and following development. Because the site will drain to an existing
storm system, bank stabilization is unnecessary with this project.
Step 4: Implement Site Specific and Other Source Control BMPs
Country Club Corners Sixth Filing – Lot 1
Final Storm Drainage Letter
March 29, 2017
Page 4 of 4
Proactively controlling pollutants at their source by preventing pollution rather than removing
contaminants once they have entered the stormwater system or receiving waters is important when
protecting storm systems and receiving waters. This can be accomplished through site specific needs
such as construction site runoff control, post-construction runoff control and pollution prevention / good
housekeeping. It will be the responsibility of the contractor to develop a procedural best management
practice for the site.
All calculations are attached for reference.
EROSION CONTROL
Erosion and sedimentation will be controlled on-site by use of sediment control logs, inlet protection, a
gravel construction entrance, seeding, mulch, and turf. The measures are designed to limit the overall
sediment yield increase due to construction as required by the City of Fort Collins. During overlot and
final grading the soil will be roughened and furrowed perpendicular to the prevailing winds.
During the performance of the work required by these specifications or any operations appurtenant
thereto, whether on right-of-way provided by the City or elsewhere, the contractor shall furnish all labor,
equipment, materials, and means required. The Contractor shall carry out proper efficient measures
wherever and as necessary to reduce dust nuisance, and to prevent dust nuisance that has originated from
his operations from damaging crops, orchards, cultivated fields, and dwellings, or causing naissance to
persons. The Contractor will be held liable for any damage resulting from dust originating from his
operations under these specifications on right-of-way or elsewhere.
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights-of-way.
Wherever construction vehicles access routes or intersect paved public roads, previsions must be made to
minimize the transport of sediment by runoff or vehicles tracking onto the paved surface. Stabilized
construction entrances are required with base material consisting of 6” coarse aggregate. The contractor
will be responsible for clearing mud tracked onto city streets on a daily basis.
All temporary and permanent erosion and sediment control practices must be maintained and repaired as
needed to assure continued performance of their intended function. Silt fence and sediment control logs
will require periodic replacement. Maintenance is the responsibility of the contractor.
All disturbed areas must be seeded and mulched within 30 days of project start. Vegetation shall not be
considered established until a ground cover is achieved which is demonstrated to be mature enough to
control soil erosion to the satisfaction of the City Inspector and to survive severe weather condition.
Thank you in advance for your time and if you have any questions or comments please contact me at
(970) 347-8917.
Sincerely,
Jason T. Claeys, P.E., LEED AP
Interwest Consulting Group
Attachments
SITE
Vicinity Map
Scale: 1" = 1000'
PROJECT DATUM: NAVD88
CITY OF FORT COLLINS BENCHMARK #42-97
ON TOP OF A STORM INLET STRUCTURE ON THE EAST
SIDE OF REDWOOD ST., 400 FEET SOUTH OF WILLOX LANE.
ELEV= 4969.93
CITY OF FORT COLLINS BENCHMARK #V401
AT THE JUNCTION OF U.S. HIGHWAY 287 AND BRISTLECONE DRIVE, 194.9 FT EAST OF THE
CENTERLINE OF THE NORTH BOUND LANES OF THE HIGHWAY, 48.2 FT NORTH OF THE CENTER
OF THE DRIVE, AND 3.6 FT NORTH OF A UTILITY POLE AND POWERLINE CROSSING THE DRIVE
ELEV= 4977.81
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL DATUM.
IF NGVD29 UNADJUSTED IS REQUIRED FOR ANY PURPOSE,
THE FOLLOWING EQUATIONS SHOULD BE USED:
NGVD UNADJUSTED = 4969.93 (NAVD88) - 3.18
NGVD UNADJUSTED = 4977.81 (NAVD88) - 3.17
HORIZONTAL DATUM: COLORADO STATE PLAN COORDINATES NAD 83(2007) DATUM.
HORIZONTAL CONTROL BASED VRS.
Hydrologic Soil Group—Larimer County Area, Colorado
(Country Club Corners Sixth Filing - Lot 1)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/19/2017
Page 1 of 4
4495250 4495260 4495270 4495280 4495290 4495300 4495310 4495320
4495250 4495260 4495270 4495280 4495290 4495300 4495310 4495320
493600 493610 493620 493630 493640 493650 493660 493670 493680 493690 493700 493710
493600 493610 493620 493630 493640 493650 493660 493670 493680 493690 493700 493710
40° 36' 31'' N
105° 4' 32'' W
40° 36' 31'' N
105° 4' 27'' W
40° 36' 28'' N
105° 4' 32'' W
40° 36' 28'' N
105° 4' 27'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 25 50 100 150
Feet
0 5 10 20 30
Meters
Map Scale: 1:580 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
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
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
73 Nunn clay loam, 0 to 1
percent slopes
C 1.7 100.0%
Totals for Area of Interest 1.7 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Hydrologic Soil Group—Larimer County Area, Colorado Country Club Corners Sixth Filing -
Lot 1
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/19/2017
Page 3 of 4
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado Country Club Corners Sixth Filing -
Lot 1
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/19/2017
Page 4 of 4
Country Club Corners Sixth Filing - Lot 1
DEVELOPED IMPERVIOUS AREA CALCULATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
BASINS:
%
Impervious
Runoff
Coefficient C
Return
Period
Frequency
Adjustment
Factor (Cf)
100% 0.95
2-year to
10-year
1.00
90% 0.95 100-year 1.25
90% 0.95
40% 0.50
0% 0.25
C2 to C10 C100
101 35,609 0.817 25,162 0 221 0 10,227 71.2% 0.75 0.94
102 8,183 0.188 1,389 4,680 0 0 2,113 68.5% 0.77 0.96
103 3,788 0.087 1,642 0 0 0 2,146 43.4% 0.55 0.69
Overall 47,579 1.092 28,193 4,680 221 0 14,486 68.5% 0.74 0.92
Weighted %
Impervious
Apaved COMPOSITE
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Agravel/pavers
(sq feet)
Alawn
(sq feet)
Gravel/Pavers
Lawns
(Heavy, 2-7% Slope)
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Land Use
Paved
Roof
Walks
J.Claeys
Interwest Consulting Group
1303-158-00
Country Club Corners Sixth Filing - Lot 1
DEVELOPED TIME OF CONCENTRATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
EQUATIONS:
-Equation 6-2 -Equation 6-4 -Urbanized Check Equation 6-5
-Equation 6-3
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition
500 ft - Overland flow shall not exceed for undeveloped condition
Final t c = minimum of t i + t t and urbanized basin check
recommended minimum t c = 5 min for urbanized basins
BASINS
Type of Travel
Surface
Cv
1 101 71.2% 0.75 0.723 60 0.0146 4.41 256 0.0101 Paved Areas 20 2.01 2.12 6.54 0.0109 9.05 6.54
2 102 68.5% 0.77 0.438 35 0.0209 2.83 99 0.0100 Paved Areas 20 2.00 0.82 5.00 0.0129 8.42 5.00
3 103 43.4% 0.55 1.161 24 0.0200 3.90 150 0.0038 Paved Areas 20 1.23 2.03 5.92 0.0060 13.16 5.92
REMARKS
Final
tc
(min)
tc
=ti
+tt
(min)
J.Claeys
Interwest Consulting Group
1303-158-00
March 29, 2017
SLOPE
(ft/ft)
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
ti
(min)
LENGTH Table RO-2
(ft)
INITIAL/OVERLAND
TIME (ti)
DESIGN
POINT
Sub-basin C5
SUB-BASIN DATA
%
Impervious
Urban Check
tc
(min)
OVERALL SLOPE
(ft/ft)
TRAVEL TIME (tt)
SLOPE
(ft/ft)
VELOCITY
(ft/s)
tt
Country Club Corners Sixth Filing - Lot 1
DEVELOPED PEAK RUNOFF
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Town of Timnth - Design Criteria Manual (2016)
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS: I = rainfall intensity (in/hr)
Q n = n -yr peak discharge (cfs) P 1 = one-hour point rainfall depth (in)
C n = n -yr runoff coefficient t c = time of concentration (min)
I n = n -yr rainfall intensity (in/hr) P 1-5yr = 1.14 in
A n = Basin drainage area (ac) P 1-10yr = 1.40 in
P 1-100yr = 2.86 in
BASIN SUMMARY:
Runoff Coeff.
(C5)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
Runoff Coeff.
(C10)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
Runoff Coeff.
(C100)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
1 101 0.817 6.54 0.75 0.61 3.57 2.19 0.75 0.61 4.39 2.69 0.94 0.77 8.97 6.86
2 102 0.188 5.00 0.77 0.14 3.86 0.56 0.77 0.14 4.74 0.68 0.96 0.18 9.68 1.75
3 103 0.087 5.92 0.55 0.05 3.68 0.18 0.55 0.05 4.52 0.22 0.69 0.06 9.24 0.56
100-yr Peak Runoff
J.Claeys
Interwest Consulting Group
1303-158-00
March 29, 2017
10-yr Peak Runoff
Design
Point
Sub-basin Area (acres) tc (min)
5-yr Peak Runoff
Q n = C n I n A n
0.786651)
1
( 10 )
28 . 5
t c
P
I
+
=
Country Club Corners Sixth Filing - Lot 1
Low Impact Development
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Low Impact Development Summary
Pavement Area Summary
28,193 sqft
0 sqft
0.0%
Developed Area Summary
47,579 sqft
Total New Impervious area: 33,094 sqft
Total Impervious Area required for Treatment (75%): 24,820 sqft
0 sqft
0 sqft
0 sqft
25,162 sqft
25,162 sqft
76.0%
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010
Total New Paved Area:
Permeable Paver Area:
Total Newly Developed Area:
Proposed Area of Pavers:
Additional Area Treated by Pavers:
Total Area Treated by Pavers:
Total Area Treated by LID:
Percent Site Impervious Area Treated by LID:
Percent Pavement Area as Permeable Pavers:
Impervious Area Treated by Rain Garden:
City of Fort Collins - Ordinance No. 007, 2016
- Treat at least 75% of any newly developed or redeveloped area using one or a combination of LID
techniques, or
- Treat at least 50% of any newly developed or redeveloped area using one or a combination of LID
techniques when 25% of private driveable surfaces are permeable.
J.Claeys
Interwest Consulting Group
1303-158-00
March 29, 2017
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 71.2 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.712
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 35,609 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 666.0 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 507 sq ft
D) Actual Flat Surface Area AActual = 512 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1170 sq ft
F) Rain Garden Total Volume VT= 841 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
CoFC Rain Garden Section (12" Growing Media, 6" Pea Gravel,
10" CDOT Class 2)
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 666 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 3/5 in
Design Procedure Form: Rain Garden (RG)
J.Claeys
Interwest Consulting Group
March 29, 2017
Country Club Corners Sixth Filing - Lot 1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1303-158-00 UD-BMP_v3.05.xlsm, RG 3/28/2017, 1:51 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
J.Claeys
Interwest Consulting Group
March 29, 2017
Country Club Corners Sixth Filing - Lot 1
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
1303-158-00 UD-BMP_v3.05.xlsm, RG 3/28/2017, 1:51 PM
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Detention Volume Calculation
0.9
1.25
1.00 ft3 acre-ft
11.69 acres 98,838 2.269
7.78 cfs
Time
(min)
100-yr
Intensity
(I , in/hr)
Q100
(cfs)
Accumulative
Runoff Volume
(ft3)
Release
Volume
(ft3)
Detained
Volume
(ft3)
Detained
Volume
(acre-ft)
0 0.00 0.00 0.00 0.00 0.00 0.0000
5 9.95 116.32 34,894.65 2,334.64 32,560.01 0.7475
10 7.72 90.25 54,148.08 4,669.29 49,478.79 1.1359
15 6.52 76.22 68,596.92 7,003.93 61,592.99 1.4140
20 5.60 65.46 78,556.80 9,338.57 69,218.23 1.5890
25 4.98 58.22 87,324.30 11,673.22 75,651.08 1.7367
30 4.52 52.84 95,109.84 14,007.86 81,101.98 1.8618
35 4.08 47.70 100,159.92 16,342.51 83,817.41 1.9242
40 3.74 43.72 104,929.44 18,677.15 86,252.29 1.9801
45 3.46 40.45 109,207.98 21,011.79 88,196.19 2.0247
50 3.23 37.76 113,276.10 23,346.44 89,929.66 2.0645
55 3.03 35.42 116,888.31 25,681.08 91,207.23 2.0938
60 2.86 33.43 120,360.24 28,015.72 92,344.52 2.1199
65 2.72 31.80 124,007.52 30,350.37 93,657.15 2.1501
70 2.59 30.28 127,163.82 32,685.01 94,478.81 2.1689
75 2.48 28.99 130,460.40 35,019.65 95,440.75 2.1910
80 2.38 27.82 133,546.56 37,354.30 96,192.26 2.2083
85 2.29 26.77 136,527.51 39,688.94 96,838.57 2.2231
90 2.21 25.83 139,508.46 42,023.59 97,484.87 2.2379
95 2.13 24.90 141,928.29 44,358.23 97,570.06 2.2399
100 2.06 24.08 144,488.40 46,692.87 97,795.53 2.2451
105 2.00 23.38 147,294.00 49,027.52 98,266.48 2.2559
110 1.94 22.68 149,678.76 51,362.16 98,316.60 2.2570
115 1.89 22.09 152,449.29 53,696.80 98,752.49 2.2670
120 1.84 21.51 154,869.12 56,031.45 98,837.67 2.2690
125 1.79 20.93 156,938.25 58,366.09 98,572.16 2.2629
130 1.75 20.46 159,568.50 60,700.73 98,867.77 2.2697
135 1.71 19.99 161,918.19 63,035.38 98,882.81 2.2700
140 1.67 19.52 163,987.32 65,370.02 98,617.30 2.2639
145 1.63 19.05 165,775.89 67,704.67 98,071.22 2.2514
Country Club Corners Sixth Filing
Critical Pond Elevations
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised January 2016)
Stage Storage
Volume (pond volume calculated using the prismoidal formula):
CONTOUR (FT) AREA (FT2) AREA (ACRE)
VOLUME
(ACRE-FT)
DEPTH (FT)
CUMULATIVE VOLUME
(ACRE-FT)
4973.15 0 0.000 0.000 0.00 0.000
4974.0 3641 0.084 0.024 0.85 0.024
4975.0 15055 0.346 0.200 1.85 0.223
4976.0 29283 0.672 0.500 2.85 0.723
4977.0 34157 0.784 0.727 3.85 1.451
4978.0 37138 0.853 0.818 4.85 2.269
0.000 N/A ft
2.269 4978.00 ft
J.Claeys
Interwest Consulting Group
1303-158-00
Acre-Ft Interpolates to an Elev. of
Required 100-yr Detention Volume (including WQCV) =
March 28, 2017
Required Water Quality Capture Volume (WQCV) =
Acre-Ft Interpolates to an Elev. of
( )
3
AAAADepth 1 2 1 2
V
+ +
=
1303-158-00 PondCalcs.xls - Pond Stage Storage Page 1 of 1 Interwest Consulting Group
Bristlecone Ex 30" RCP Capacity
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 10.0 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 = 20.0 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 = 0.004 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.016
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 18.5 20.0 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
Maximum Capacity for 1/2 Street based On Allowable Spread Minor Storm Major Storm
Water Depth without Gutter Depression (Eq. ST-2) y = 4.44 4.80 inches
Vertical Depth between Gutter Lip and Gutter Flowline (usually 2") dC = 2.0 2.0 inches
Gutter Depression (dC - (W * Sx * 12)) a = 1.51 1.51 inches
Water Depth at Gutter Flowline d = 5.95 6.31 inches
Allowable Spread for Discharge outside the Gutter Section W (T - W) TX = 16.5 18.0 ft
Gutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 0.321 0.296
Discharge outside the Gutter Section W, carried in Section TX QX = 5.8 7.3 cfs
Discharge within the Gutter Section W (QT - QX) QW = 2.7 3.1 cfs
Discharge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 0.0 cfs
Maximum Flow Based On Allowable Spread QT = 8.5 10.3 cfs
Flow Velocity within the Gutter Section V = 3.3 3.5 fps
V*d Product: Flow Velocity times Gutter Flowline Depth V*d = 1.6 1.8
Maximum Capacity for 1/2 Street based on Allowable Depth Minor Storm Major Storm
Theoretical Water Spread TTH = 18.7 43.7 ft
Theoretical Spread for Discharge outside the Gutter Section W (T - W) TX TH = 16.7 41.7 ft
Gutter Flow to Design Flow Ratio by FHWA HEC-22 method (Eq. ST-7) EO = 0.318 0.130
Theoretical Discharge outside the Gutter Section W, carried in Section TX TH QX TH = 5.9 68.2 cfs
Actual Discharge outside the Gutter Section W, (limited by distance TCROWN) QX = 5.9 53.1 cfs
Discharge within the Gutter Section W (Qd - QX) QW = 2.8 10.2 cfs
Discharge Behind the Curb (e.g., sidewalk, driveways, & lawns) QBACK = 0.0 10.4 cfs
Total Discharge for Major & Minor Storm (Pre-Safety Factor) Q = 8.7 73.7 cfs
Average Flow Velocity Within the Gutter Section V = 3.3 5.6 fps
V*d Product: Flow Velocity Times Gutter Flowline Depth V*d = 1.7 5.6
Slope-Based Depth Safety Reduction Factor for Major & Minor (d > 6") Storm R = 1.00 1.00
Max Flow Based on Allowable Depth (Safety Factor Applied) Qd = 8.7 73.7 cfs
Resultant Flow Depth at Gutter Flowline (Safety Factor Applied) d = 6.00 12.00 inches
Resultant Flow Depth at Street Crown (Safety Factor Applied) dCROWN = 0.00 5.69 inches
MINOR STORM Allowable Capacity is based on Spread Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = 8.5 73.7 cfs
Version 4.04 Released November 2016
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Country Club Corners 6th Filing
Bristlecone Capacity
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
UD-Inlet_v4.04.xlsm, Bristlecone Capacity 1/25/2017, 9:59 AM
Full Street Capacity = 2(73.7) = 147.4 cfs
Per Country Club Corners Filing 3, Full Street Capacity = 43.22 cfs
With approximated 32.5 cfs (25 cfs orignially) available within 30" RCP,
there is a total street+pipe capacity within Bristlecone of 179.9 cfs
150 1.60 18.70 168,336.00 70,039.31 98,296.69 2.2566
155 1.57 18.35 170,685.69 72,373.95 98,311.74 2.2569
160 1.54 18.00 172,824.96 74,708.60 98,116.36 2.2524
165 1.51 17.65 174,753.81 77,043.24 97,710.57 2.2431
170 1.48 17.30 176,472.24 79,377.88 97,094.36 2.2290
175 1.45 16.95 177,980.25 81,712.53 96,267.72 2.2100
180 1.42 16.60 179,277.84 84,047.17 95,230.67 2.1862
185 1.40 16.37 181,662.60 86,381.81 95,280.79 2.1873
190 1.38 16.13 183,907.08 88,716.46 95,190.62 2.1853
195 1.36 15.90 186,011.28 91,051.10 94,960.18 2.1800
200 1.34 15.66 187,975.20 93,385.74 94,589.46 2.1715
205 1.32 15.43 189,798.84 95,720.39 94,078.45 2.1597
210 1.30 15.20 191,482.20 98,055.03 93,427.17 2.1448
215 1.28 14.96 193,025.28 100,389.68 92,635.60 2.1266
220 1.26 14.73 194,428.08 102,724.32 91,703.76 2.1052
225 1.24 14.50 195,690.60 105,058.96 90,631.64 2.0806
230 1.22 14.26 196,812.84 107,393.61 89,419.23 2.0528
235 1.21 14.14 199,443.09 109,728.25 89,714.84 2.0596
240 1.20 14.03 202,003.20 112,062.89 89,940.31 2.0647
Adjusted Runoff Coefficient (CC f )
Area (A )
Allowed Release Rate
Required Detention
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
City of Fort Collins - Storm Water Criteria Manual
March 29, 2017
Runoff Coefficient (C )
Frequency Factor (C f )
100-yr Detention Volume - FAA Method
Country Club Corners Sizth Filing
J.Claeys
Interwest Consulting
1308-158-00
Interim Detention Pond
(min)
AREA
(acres)
LENGTH
(ft)
( )
0 .33
0 . 395 1 . 1 5
S
C L
ti
−
=
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
��
= 18 − 15� +
�
60 24� + 12 �
March 29, 2017
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
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: Apr 22, 2011—Apr
28, 2011
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.
Hydrologic Soil Group—Larimer County Area, Colorado
(Country Club Corners Sixth Filing - Lot 1)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/19/2017
Page 2 of 4