HomeMy WebLinkAboutVILLAGE ON REDWOOD (FORT COLLINS HOUSING AUTHORITY) - FDP - FDP150036 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT
FOR
Village on Redwood
Prepared by:
Interwest Consulting Group
1218 West Ash, Suite A
Windsor, Colorado 80550
Phone: 970.674.3300
Fax: 970.674.3303
Prepared for:
Fort Collins Housing Authority
1715 West Mountain Ave.
Fort Collins, Colorado 80521
Phone: 970.416.2910
October 14, 2015
Job Number 1237-112-00
October 14, 2015
Mr. Wes Lamarque
Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522
RE: Final Drainage Report for Village on Redwood
Dear Wes,
We are pleased to submit for your review and approval, this Final Drainage Report for the
Village on Redwood low-income housing development. I certify that this report for the drainage
design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage
Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
Jason T. Claeys, P.E., LEED AP
Interwest Consulting Group
1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................................................. 1
2. EXISTING CONDITIONS .................................................................................................................................... 1
3. DEVELOPED CONDITIONS ............................................................................................................................... 2
4. LOW IMPACT DEVELOPMENT TECHNIQUES .............................................................................................. 3
5. CONCLUSION ...................................................................................................................................................... 3
6. REFERENCES ...................................................................................................................................................... 4
APPENDIX A — SITE DESCRIPTIONS, CHARACTERISTICS & REFERENCES ........................................ A
APPENDIX B — RATIONAL CALCULATIONS .................................................................................................. B
APPENDIX C — STORM DRAIN SIZING ............................................................................................................ C
APPENDIX D — DETENTION POND CALCULATIONS ................................................................................... D
APPENDIX E — LOW IMPACT DEVELOPMENT CALCULATIONS ............................................................ E
1
1. INTRODUCTION
The project site currently is an undeveloped infill site located north of Nokomis Ct and
west of Redwood St. The site is 9.61 acres with approximately 3.0± acres being an
existing detention pond and approximately 6.6± acres of developable land. The property
will be subdivided into two lots, one containing the existing detention pond and the other
being the developed portion for low income housing. The project will consist of
constructing 12 low income housing buildings, a community clubhouse, and associated
pedestrian and vehicle accesses. This project will be completed in one phase of
construction.
2. EXISTING CONDITIONS
The project site is bound by Redwood St to the east and surrounded by previously
developed properties on the north, south, and west. The site is currently undeveloped and
appears to be vegetated with native grasses and wetland plants surrounding the existing
detention pond. The existing detention pond encompasses the western portion of the site.
Based on research of the site, it appears that this detention pond was constructed
sometime after 1975. The site is within the Dry Creek basin and within the basin limits
of the Northeast College Corridor Outfall improvements. The existing site is
approximately 2.7% impervious, including the west half of Redwood St. The existing
100-yr peak runoff rate from Redwood St (Basin H1) and to the existing detention pond
(Basin H2) is 14.10 cfs and 11.31 cfs, respectively. The runoff directed to Redwood St is
conveyed to and collected by an existing 15’ Type R inlet located near the southeast
corner of the site.
Upon further research of the surrounding storm drainage infrastructure, the design
drawings and calculations were found. Referencing the “Redwood Street Improvements”
plan set, dated September 1996 and prepared by Stewart & Associates, the existing storm
drain within Redwood Street was sized and constructed to convey the 100-yr developed
runoff from the proposed Village on Redwood site. The storm drain is anticipated to
capture and convey 33.5 cfs from the site during a 100-yr storm event. The recorded
documents are attached for reference and further discussion is needed to determine the
impacts to the proposed storm drain system within Villages on Redwood.
The existing runoff rates, stated above, are referenced for the stormwater release rates for
2
the proposed improvements. All calculations and exhibits are attached.
3. DEVELOPED CONDITIONS
The project proposes to develop this infill site with 12 low income housing buildings
(with a total of 72 units), a community clubhouse and associated infrastructure and
site/building pedestrian and vehicle access. The property will be subdivided into 2 lots,
one containing the existing detention pond and the remaining containing the proposed
low income housing development.
The project is required to detain the developed 100-yr runoff to the existing 100-yr runoff
rate. Further discussion is needed due to the recent information found determining that
the existing storm drain within Redwood Street was sized and constructed to convey 33.5
cfs from the Village on Redwood site. The detention requirements will be provided
through the use of a detention pond in the southeast corner of the site. Water quality
capture volume and associated infrastructure is not required as part of this project, though
implementation of Low Impact Development (LID) techniques for water quality
enhancement are required and proposed with this project.
Similar to the existing conditions, the proposed project is divided into two major basins,
one basin draining undetained to the existing detention pond to the west (Basin D7), and
the remaining basin draining towards Redwood St (Basins D1 thru D6). In general, the
basin limits are maintained for the areas draining to the existing detention pond and
towards Redwood Street. This causes a slight increase to the existing pond and is
considered negligible. Runoff from Basins D1 thru D5 are conveyed to the proposed
detention pond in the southeast corner of the site, with the outfall being the connection to
the existing storm drain within Redwood St. The undetained developed portion (Basin
D6) drains to the existing inlet within Redwood St. Under the developed condition, the
100-yr peak runoff rates to the existing detention pond and Redwood Street are estimated
to be 12.33 cfs and 34.25 cfs, respectively. Detaining the developed runoff to the
existing 100-yr runoff rate for the basin draining towards Redwood Street, in addition to
accounting for the undetained portions that drain directly to Redwood, requires a
detention volume of 0.375 acre-ft. The undetained portion has a runoff rate of 7.20 cfs,
combined with detention pond release rate of 6.90 cfs, has a peak 100-yr runoff rate of
14.10 cfs, equal to the existing 100-yr runoff rate.
3
The storm drain pipe sizes were determined utilizing Hydraflow. The storm drain system
has been designed to convey the 100-yr storm through a combination of the pipe and
overland flow. The grading design is such that when the hydraulic grade line exceeds the
pipe capacities at the inlets, the runoff will overtop the adjacent high point and convey
overland ultimately to the proposed detention pond.
All preliminary calculations and exhibits are attached for reference.
4. LOW IMPACT DEVELOPMENT TECHNIQUES
In reference to the code requirements for implementation of Low Impact Development
(LID) techniques, the use of permeable pavers and a sand filter are necessary to satisfy
these requirements. The main LID being proposed to be implemented on site are
permeable pavers located in sections of the north and south drives. The remaining
developed area will be treated by a sand filter located near the southeast corner of the site
within the detention pond. The sand filter is designed to detain and infiltrate the required
water quality capture volume and directly spill into the detention area for events beyond
the capacity of the sand filter. The sand filter water quality capture volume is designed to
have a depth of 12 inches. Underdrains are not required with a full infiltration design.
Percolation test was performed and is provided in the appendix. Based on the average
percolation rate of 8.6 minutes per inch, it is estimated that the water quality capture
volume will infiltrate within 2 hrs of filling. A Standard Operations Procedure will be
provided to assist in ensuring that these BMPs will adequately perform over time.
All calculations are attached for reference.
5. CONCLUSION
All computations that have been completed within this report are in compliance with the
CoFC Stormwater Criteria Manual, and Urban Drainage and Flood Control District
requirements and standards. The proposed drainage concepts presented in this report and
on the construction plans adequately provide for stormwater quantity and quality
treatment of proposed impervious areas. Conveyance elements have been designed to
pass required flows and to minimize future maintenance.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit will be required.
4
6. REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage
and Flood Control District, June 2001, Revised April 2008.
2. Storm Drainage Criteria Manual and Construction Standards, City of Fort Collins
Storm Water Utility, City of Fort Collins, Colorado, Updated January, 1997 with
2012 amendments.
3. “Hydrologic Group Rating for Larimer County Area, Colorado”, USDA-Natural
Resources Conservation Service, National Cooperative Soil Survey. Web Soil
Survey URL: http://websoilsurvey.nrcs.usda.gov. [03/28/2014]
APPENDIX A — SITE DESCRIPTIONS, CHARACTERISTICS & REFERENCES
vicinity map
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 #43-97
ON THE SOUTH END OF THE WEST HEADWALL OF THE
LAKE CANAL BRIDGE AT NORTH LEMAY AVE., 200 FEET
SOUTH OF THE INTERSECTION OF LEMAY AVE. AND CONIFER ST.
ELEV= 4960.11
PLEASE NOTE: THIS PLAN SET IS USING NAVD88 FOR A VERTICAL
DATUM. SURROUNDING DEVELOPMENTS HAVE USED NGVD29
UNADJUSTED FOR THEIR VERTICAL DATUMS.
IF NGVD29 UNADJUSTED DATUM IS REQUIRED FOR ANY PURPOSE,
THE FOLLOWING EQUATIONS SHOULD BE USED:
NGVD29 UNADJUSTED = 4969.93 (NAVD88) - 3.18 = 4966.75
NGVD29 UNADJUSTED = 4960.11 (NAVD88) - 3.17 = 4956.94
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/14/2015
Page 1 of 4
4494910 4494940 4494970 4495000 4495030 4495060 4495090
4494910 4494940 4494970 4495000 4495030 4495060 4495090
494040 494070 494100 494130 494160 494190 494220 494250 494280 494310 494340
494040 494070 494100 494130 494160 494190 494220 494250 494280 494310 494340
40° 36' 24'' N
105° 4' 14'' W
40° 36' 24'' N
105° 4' 0'' W
40° 36' 17'' N
105° 4' 14'' W
40° 36' 17'' N
105° 4' 0'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 20 40 80 120
Meters
Map Scale: 1:1,470 if printed on A landscape (11" x 8.5") sheet.
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: http://websoilsurvey.nrcs.usda.gov
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 of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
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
64 Loveland clay loam, 0 to
1 percent slopes
C 3.3 32.5%
73 Nunn clay loam, 0 to 1
percent slopes
C 7.0 67.5%
Totals for Area of Interest 10.3 100.0%
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
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/14/2015
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/14/2015
Page 4 of 4
Storm drain sized for 100 yr
(33.5 cfs) developed flows from
Village on Redwood site
Assumed developed flows from
Village on Redwood site, referenced
for existing storm drain sizing
(100-yr = 33.5cfs)
B
APPENDIX B — RATIONAL CALCULATIONS
FCHA - Villages on Redwood
DRAINAGE SUMMARY
Design Engineer:
Design Firm:
Project Number:
Date:
DRAINAGE SUMMARY:
Area (acres)
%
Imprevious
100-yr Peak
Runoff (cfs) Area (acres)
%
Imprevious
100-yr Peak
Runoff (cfs)
To Redwood 6.217 4.4% 14.10 5.983 52.3% 26.92 H1 compared to D1+...D6
To Existing Pond 3.785 0.0% 11.45 4.020 1.4% 12.33 H2+OF1 compared to D7+OF1
Totals 10.002 2.7% 25.56 10.002 32.4% 39.25
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
Basins Notes
Historical Developed
FCHA - Villages on Redwood
HISTORIC 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 August 2006)
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
H1 270,830 6.217 11,888 0 0 0 258,941 4.4% 0.28 0.35
H2 162,764 3.737 0 0 0 0 162,764 0.0% 0.25 0.31
OF1 2,110 0.048 0 0 0 0 2,110 0.0% 0.25 0.31
Total 435,704 10.002 11,888 0 0 0 423,816 2.7% 0.27 0.34
Pavers
Walks
Apaved
(sq feet)
Lawns (Heavy, 2-7%
Slope)
Weighted % COMPOSITE
Impervious
1237-112-00
Interwest Consulting Group
T.Alva
October 14, 2015
Sub-basin
Designation
Atotal
(sq feet)
Atotal
(acres)
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
Land Use
Paved
Roof
Alawn
(sq feet)
Apavers
FCHA - Villages on Redwood
HISTORIC TIME OF CONCENTRATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
-Equation RO-3 -Equation RO-4 -Urbanized Check Equation RO-5
-Equation RO-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
H1 H1 0.28 6.217 419 0.0043 40.72 495 0.0059 Paved Areas 20 1.54 5.37 46.09 15.08 15.08
H2 H2 0.25 3.737 32 0.2582 3.00 0 0.0001 Tilage/Field 5 0.05 0.00 5.00 10.18 5.00 All Overland Flow
OF1 OF1 0.25 0.048 15 0.0802 3.06 38 0.0251 Tilage/Field 5 0.79 0.81 5.00 10.30 5.00
SUB-BASIN DATA
INITIAL/OVERLAND
TIME (ti
)
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
DESIGN
POINT
Sub-basin C5
AREA
(acres)
LENGTH
(ft)
SLOPE
(ft/ft)
ti
(min)
LENGTH Table RO-2
(ft)
TRAVEL TIME (tt
)
REMARKS
tc
Urban
Check
Final tc
(min)
tc
=ti
+tt
SLOPE (min)
(ft/ft)
VEL.
(ft/s)
tt
FCHA - Villages on Redwood
HISTORIC PEAK RUNOFF
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
Q n = n -yr peak discharge (cfs) I = rainfall intensity (in/hr) P 1-5yr = 1.14 in
C n = n -yr runoff coefficient P 1 = one-hour point rainfall depth (in) P 1-100yr = 2.86 in
I n = n -yr rainfall intensity (in/hr) t c = time of concentration (min) P 1-10yr = 1.40 in
A n = Basin drainage area (ac)
BASINS:
Runoff Coeff.
(C5
)
C(A)
(acres)
Intensity
(in/hr)
Q (ft
3
/s)
Runoff Coeff.
(C5
)
C(A)
(acres)
Intensity
(in/hr)
Q (ft
3
/s)
Runoff Coeff.
(C100
)
C(A) (acres)
Intensity
(in/hr)
Q (ft
3
/s)
H1 H1 6.217 15.08 0.28 1.75 2.58 4.50 0.28 1.75 6.46 11.28 0.35 2.18 6.46 14.10
H2 H2 3.737 5.00 0.25 0.93 3.86 3.61 0.25 0.93 9.68 9.05 0.31 1.17 9.68 11.31
OF1 OF1 0.048 5.00 0.25 0.01 3.86 0.05 0.25 0.01 9.68 0.12 0.31 0.02 9.68 0.15
5-yr Peak Runoff 10-yr Peak Runoff 100-yr Peak Runoff
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
City of Fort Collins - Storm Water Criteria Manual (1997)
Design
Point
Sub-basin Area (acres) tc
(min)
Q n = C n I n A n
0.786651)
1
( 10 )
FCHA - Villages on Redwood
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 August 2006)
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
D1 56,993 1.308 12,612 11,987 7,688 1,783 22,924 54.4% 0.65 0.82
D2 31,622 0.726 5,422 7,283 4,383 5,115 9,420 56.8% 0.67 0.84
D3 39,575 0.909 0 5,212 17,663 0 16,700 52.0% 0.65 0.82
D4 43,270 0.993 11,976 10,161 5,206 4,278 11,650 63.6% 0.72 0.90
D5 41,915 0.962 7,156 5,710 2,547 0 26,502 34.8% 0.51 0.63
D6 47,238 1.084 16,675 3,986 7,526 0 19,051 57.2% 0.67 0.83
D7 174,015 3.995 0 2,185 523 0 171,307 1.4% 0.26 0.33
OF1 1,076 0.025 0 0 0 0 1,076 0.0% 0.25 0.31
Total 435,704 10.002 53,841 46,524 45,535 11,175 278,629 32.4% 0.49 0.61
Inlet 02 (D1+D2+D3) 128,190 2.943 18,034 24,482 29,733 6,897 49,043 54.3% 0.66 0.82
Inlet 01 (D1+D2+D3+D4) 171,461 3.936 30,010 34,643 34,939 11,175 60,693 56.6% 0.67 0.84
To Redwood 260,614 5.983 53,841 44,340 45,012 11,175 106,246 53.2% 0.65 0.81
Sub-basin
Designation
Paved
Pavers
Land Use
Atotal
(sq feet)
Atotal
(acres)
Walks
Lawns (Heavy, 2-
7% Slope)
Weighted %
Impervious
COMPOSITE
Roof
Apaved
(sq feet)
FCHA - Villages on Redwood
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 August 2006)
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
D1 56,993 1.308 12,612 11,987 7,688 1,783 22,924 54.4% 0.65 0.82
D2 31,622 0.726 5,422 7,283 4,383 5,115 9,420 56.8% 0.67 0.84
D3 39,575 0.909 0 5,212 17,663 0 16,700 52.0% 0.65 0.82
D4 43,270 0.993 11,976 10,161 5,206 4,278 11,650 63.6% 0.72 0.90
D5 41,915 0.962 7,156 5,710 2,547 0 26,502 34.8% 0.51 0.63
D6 47,238 1.084 16,675 3,986 7,526 0 19,051 57.2% 0.67 0.83
D7 174,015 3.995 0 2,185 523 0 171,307 1.4% 0.26 0.33
OF1 1,076 0.025 0 0 0 0 1,076 0.0% 0.25 0.31
Total 435,704 10.002 53,841 46,524 45,535 11,175 278,629 32.4% 0.49 0.61
Inlet 02 (D1+D2+D3) 128,190 2.943 18,034 24,482 29,733 6,897 49,043 54.3% 0.66 0.82
Inlet 01 (D1+D2+D3+D4) 171,461 3.936 30,010 34,643 34,939 11,175 60,693 56.6% 0.67 0.84
To Outlet Headwall 213,376 4.898 37,166 40,354 37,486 11,175 87,195 52.3% 0.64 0.80
To Redwood 260,614 5.983 53,841 44,340 45,012 11,175 106,246 53.2% 0.65 0.81
Basin D3 to ROW 27,055 0.621 2,671 4,612 3,982 0 15,790 38.5% 0.54 0.68
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
Weighted %
Impervious
COMPOSITE
Roof
Apaved
(sq feet)
Aroof
(sq feet)
Awalk
(sq feet)
Apavers
(sq feet)
Alawn
FCHA - Villages on Redwood
DEVELOPED TIME OF CONCENTRATION
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
-Equation RO-2 -Equation RO-4 -Urbanized Check Equation RO-5
-Equation RO-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
D1 D1 0.65 1.308 21 0.0446 2.29 529 0.0068 Paved Areas 20 1.65 5.34 7.63 13.05 7.63
D2 D2 0.67 0.726 78 0.0268 5.02 156 0.0063 Paved Areas 20 1.59 1.63 6.65 11.30 6.65
D3 D3 0.65 0.909 82 0.0443 4.51 140 0.0116 Paved Areas 20 2.15 1.08 5.59 11.23 5.59
D4 D4 0.72 0.993 41 0.0701 2.34 255 0.0093 Paved Areas 20 1.93 2.20 5.00 11.64 5.00
D5 D5 0.51 0.962 44 0.0281 5.11 82 0.0130 Paved Areas 20 2.28 0.60 5.71 10.70 5.71
D6 D6 0.67 1.084 13 0.1729 1.13 568 0.0038 Paved Areas 20 1.23 7.70 8.82 13.23 8.82
D7 D7 0.26 3.995 37 0.0513 5.44 0 0.0001 Paved Areas 20 0.20 0.00 5.44 10.21 5.44 All Overland Flow
OF1 OF1 0.25 0.025 6 0.1371 1.66 0 0.0001 Paved Areas 20 0.20 0.00 5.00 10.04 5.00 All Overland Flow
TRAVEL TIME (tt)
REMARKS
tc
Urban
Check
Final tc
(min)
tc
=ti
+tt
SLOPE (min)
(ft/ft)
VEL.
(ft/s)
tt
(min)
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
SLOPE
(ft/ft)
ti
(min)
LENGTH Table RO-2
(ft)
SUB-BASIN DATA
INITIAL/OVERLAND
TIME (ti)
DESIGN
POINT
Sub-basin C5
FCHA - Villages on Redwood
DEVELOPED PEAK RUNOFF
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001 (Revised August 2006)
EQUATIONS:
Q n = n -yr peak discharge (cfs) I = rainfall intensity (in/hr) P 1-5yr = 1.14 in
C n = n -yr runoff coefficient P 1 = one-hour point rainfall depth (in) P 1-10yr = 1.40 in
I n = n -yr rainfall intensity (in/hr) t c = time of concentration (min) P 1-100yr = 2.86 in
A n = Basin drainage area (ac)
BASINS:
Runoff Coeff.
(C5)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
Runoff Coeff.
(C5)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
Runoff Coeff.
(C100)
C(A)
(acres)
Intensity
(in/hr)
Q (ft3/s)
D1 D1 1.308 7.63 0.65 0.86 3.40 2.91 0.65 0.86 4.17 3.57 0.82 1.07 8.53 9.13
D2 D2 0.726 6.65 0.67 0.49 3.56 1.73 0.67 0.49 4.37 2.12 0.84 0.61 8.92 5.41
D3 D3 0.909 5.59 0.65 0.59 3.74 2.23 0.65 0.59 4.60 2.73 0.82 0.74 9.39 6.98
D4 D4 0.993 5.00 0.72 0.71 3.86 2.75 0.72 0.71 4.74 3.38 0.90 0.89 9.68 8.62
D5 D5 0.962 5.71 0.51 0.49 3.72 1.82 0.51 0.49 4.57 2.23 0.63 0.61 9.34 5.70
D6 D6 1.084 8.82 0.67 0.72 3.23 2.34 0.67 0.72 3.97 2.87 0.83 0.91 8.10 7.33
D7 D7 3.995 5.44 0.26 1.04 3.77 3.93 0.26 1.04 4.63 4.83 0.33 1.30 9.47 12.33
OF1 OF1 0.025 5.00 0.25 0.01 3.86 0.02 0.25 0.01 4.74 0.03 0.31 0.01 9.68 0.07
100-yr Peak Runoff
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
Design
Point
Sub-basin Area (acres) tc (min)
5-yr Peak Runoff 10-yr Peak Runoff
City of Fort Collins - Storm Water Criteria Manual (1997)
Q n = C n I n A n
0.786651)
1
( 10 )
28 . 5
t c
P
FCHA - Villages at Redwood
Attenuated Flows for Pipe Sizing
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001
EQUATIONS:
-Equation RO-2 -Equation RO-4
-Equation RO-3
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition Final t c = minimum of t i + t t and urbanized basin check
500 ft - Overland flow shall not exceed for undeveloped condition recommended minimum t c = 5 min for urbanized basins
Qn = n -yr peak discharge (cfs) I = rainfall intensity (in/hr)
Cn = n -yr runoff coefficient P1 = one-hour point rainfall depth (in)
In = n -yr rainfall intensity (in/hr) tc = time of concentration (min)
A = drainage area (ac) P1-5yr = 1.14 in.
P1-10yr = 1.40 in.
P1-100yr = 2.86 in.
BASINS:
UD-Sewer - DP/Manhole Inlet 02
Contributing Basins D1+D2+D3
Contributing Area (acres) 2.94
C2 to C10 C100
Runoff Coefficients 0.66 0.82
Overland Flow Time
Length (ft) 21
Slope (ft/ft) 0.04
ti
(min) 2.27
Travel Time
Length (ft) Slope (%)
Type of Travel
Surface Cv Velocity (ft/s) tt (min)
529 0.68% Paved Areas 20 1.65 5.35
108 0.25% Paved Areas 20 1.00 1.80
Total Time 7.15
Final Time of Concentration - tc (min)
tc
(min) 9.42
Intensities (in/hr)
5-yr 10-yr 100-yr
3.15 3.87 7.90
Discharge (cfs)
5-yr 10-yr 100-yr
6.10 7.49 19.13
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
City of Fort Collins - Storm Water Criteria Manual (1997)
Q n = C n I n A
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
=
( )
FCHA - Villages at Redwood
Attenuated Flows for Pipe Sizing
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001
EQUATIONS:
-Equation RO-2 -Equation RO-4
-Equation RO-3
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition Final t c = minimum of t i + t t and urbanized basin check
500 ft - Overland flow shall not exceed for undeveloped condition recommended minimum t c = 5 min for urbanized basins
Qn = n -yr peak discharge (cfs) I = rainfall intensity (in/hr)
Cn = n -yr runoff coefficient P1 = one-hour point rainfall depth (in)
In = n -yr rainfall intensity (in/hr) tc = time of concentration (min)
A = drainage area (ac) P1-5yr = 1.14 in.
P1-10yr = 1.40 in.
P1-100yr = 2.86 in.
BASINS:
UD-Sewer - DP/Manhole Inlet 01
Contributing Basins D1+D2+D3+D4
Contributing Area (acres) 3.94
C2 to C10 C100
Runoff Coefficients 0.67 0.84
Overland Flow Time
Length (ft) 21
Slope (ft/ft) 0.05
ti
(min) 2.17
Travel Time
Length (ft) Slope (%)
Type of Travel
Surface Cv Velocity (ft/s) tt (min)
529 0.68% Paved Areas 20 1.65 5.35
108 0.25% Paved Areas 20 1.00 1.80
102 0.25% Paved Areas 20 1.00 1.69
57 0.25% Paved Areas 20 1.00 0.94
Total Time 9.79
Final Time of Concentration - tc (min)
tc
(min) 11.96
Intensities (in/hr)
5-yr 10-yr 100-yr
2.86 3.51 7.18
Discharge (cfs)
5-yr 10-yr 100-yr
7.58 9.30 23.76
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
City of Fort Collins - Storm Water Criteria Manual (1997)
Q n = C n I n A
t c = t i + t t 0 . 5
V = C v S w
V
L
tt 60
FCHA - Villages at Redwood
Attenuated Flows for Pipe Sizing
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA:
Urban Storm Drainage Criteria Manual by Urban Drainage and Flood Control District, June 2001
EQUATIONS:
-Equation RO-2 -Equation RO-4
-Equation RO-3
CONSTRAINTS:
300 ft - Overland flow shall not exceed for developed condition Final t c = minimum of t i + t t and urbanized basin check
500 ft - Overland flow shall not exceed for undeveloped condition recommended minimum t c = 5 min for urbanized basins
Qn = n -yr peak discharge (cfs) I = rainfall intensity (in/hr)
Cn = n -yr runoff coefficient P1 = one-hour point rainfall depth (in)
In = n -yr rainfall intensity (in/hr) tc = time of concentration (min)
A = drainage area (ac) P1-5yr = 1.14 in.
P1-10yr = 1.40 in.
P1-100yr = 2.86 in.
BASINS:
UD-Sewer - DP/Manhole To Redwood
Contributing Basins D1+D2+D3+D4+D5
Contributing Area (acres) 4.90
C2 to C10 C100
Runoff Coefficients 0.64 0.80
Overland Flow Time
Length (ft) 21
Slope (ft/ft) 0.05
ti
(min) 2.33
Travel Time
Length (ft) Slope (%)
Type of Travel
Surface Cv Velocity (ft/s) tt (min)
529 0.68% Paved Areas 20 1.65 5.35
108 0.25% Paved Areas 20 1.00 1.80
102 0.25% Paved Areas 20 1.00 1.69
57 0.25% Paved Areas 20 1.00 0.94
94 0.50% Paved Areas 20 1.41 1.11 pan from fes to headwall
Total Time 10.89
Final Time of Concentration - tc (min)
tc
(min) 13.23
Intensities (in/hr)
5-yr 10-yr 100-yr
2.74 3.36 6.86
Discharge (cfs)
5-yr 10-yr 100-yr
8.58 10.54 26.92
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
City of Fort Collins - Storm Water Criteria Manual (1997)
Q n = C n I n A
t c = t i + t t 0 . 5
V = C v S w
V
L
C
APPENDIX C — STORM DRAIN SIZING
D
APPENDIX D — DETENTION POND CALCULATIONS
Project:
Basin ID:
Design Information (Input): Design Information (Input):
Catchment Drainage Imperviousness Ia = 52.30 percent Catchment Drainage Imperviousness I
a = 52.30 percent
Catchment Drainage Area A = 4.900 acres Catchment Drainage Area A = 4.900 acres
Predevelopment NRCS Soil Group Type = C A, B, C, or D Predevelopment NRCS Soil Group Type = C A, B, C, or D
Return Period for Detention Control T = 5 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100)
Time of Concentration of Watershed Tc = 13 minutes Time of Concentration of Watershed Tc = 13 minutes
Allowable Unit Release Rate q = 1.38 cfs/acre Allowable Unit Release Rate q = 1.38 cfs/acre
One-hour Precipitation P1 = 1.14 inches One-hour Precipitation P
1 = 2.86 inches
Design Rainfall IDF Formula i = C1* P
1/(C2
+Tc)^C
3 Design Rainfall IDF Formula i = C1
* P1/(C
2+Tc
)^C3
Coefficient One C1 = 28.50 Coefficient One C
1 = 28.50
Coefficient Two C2 = 10 Coefficient Two C
2 = 10
Coefficient Three C3 = 0.787 Coefficient Three C
3 = 0.787
Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated):
Runoff Coefficient C = 0.41 Runoff Coefficient C = 0.61
Inflow Peak Runoff Qp-in = 5.50 cfs Inflow Peak Runoff Qp-in = 20.52 cfs
Allowable Peak Outflow Rate Qp-out = 6.76 cfs Allowable Peak Outflow Rate Qp-out = 6.76 cfs
Mod. FAA Minor Storage Volume = 298 cubic feet Mod. FAA Major Storage Volume = 16,352 cubic feet
Mod. FAA Minor Storage Volume = 0.007 acre-ft Mod. FAA Major Storage Volume = 0.375 acre-ft
5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes)
Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage
Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume
minutes inches / hr acre-feet "m" cfs acre-feet acre-feet minutes inches / hr acre-feet "m" cfs acre-feet acre-feet
(input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output)
0 0.00 0.000 0.00 0.00 0.000 0.000 0 0.00 0.000 0.00 0.00 0.000 0.000
5 3.86 0.053 1.00 6.76 0.047 0.007 5 9.68 0.199 1.00 6.76 0.047 0.153
10 3.08 0.085 1.00 6.76 0.093 -0.008 10 7.72 0.318 1.00 6.76 0.093 0.225
15 2.58 0.107 0.94 6.36 0.131 -0.024 15 6.48 0.400 0.94 6.36 0.131 0.269
20 2.24 0.124 0.83 5.62 0.155 -0.031 20 5.61 0.462 0.83 5.62 0.155 0.307
25 1.98 0.137 0.76 5.17 0.178 -0.041 25 4.97 0.512 0.76 5.17 0.178 0.334
30 1.78 0.148 0.72 4.87 0.201 -0.053 30 4.48 0.553 0.72 4.87 0.201 0.352
35 1.63 0.158 0.69 4.66 0.225 -0.067 35 4.08 0.588 0.69 4.66 0.225 0.363
40 1.50 0.166 0.67 4.50 0.248 -0.082 40 3.76 0.619 0.67 4.50 0.248 0.371
45 1.39 0.173 0.65 4.38 0.271 -0.098 45 3.48 0.646 0.65 4.38 0.271 0.374
50 1.30 0.179 0.63 4.28 0.294 -0.115 50 3.25 0.670 0.63 4.28 0.294 0.375
55 1.22 0.185 0.62 4.19 0.318 -0.132 55 3.06 0.692 0.62 4.19 0.318 0.374
60 1.15 0.191 0.61 4.13 0.341 -0.150 60 2.88 0.712 0.61 4.13 0.341 0.371
65 1.09 0.196 0.60 4.07 0.364 -0.169 65 2.73 0.731 0.60 4.07 0.364 0.366
70 1.03 0.200 0.59 4.02 0.388 -0.187 70 2.60 0.748 0.59 4.02 0.388 0.360
75 0.99 0.205 0.59 3.98 0.411 -0.206 75 2.47 0.764 0.59 3.98 0.411 0.353
80 0.94 0.209 0.58 3.94 0.434 -0.225 80 2.37 0.779 0.58 3.94 0.434 0.345
85 0.90 0.213 0.58 3.91 0.457 -0.245 85 2.27 0.793 0.58 3.91 0.457 0.336
90 0.87 0.216 0.57 3.88 0.481 -0.265 90 2.18 0.807 0.57 3.88 0.481 0.326
95 0.84 0.220 0.57 3.85 0.504 -0.284 95 2.10 0.820 0.57 3.85 0.504 0.315
100 0.81 0.223 0.57 3.83 0.527 -0.305 100 2.02 0.832 0.57 3.83 0.527 0.304
105 0.78 0.226 0.56 3.81 0.551 -0.325 105 1.95 0.843 0.56 3.81 0.551 0.293
110 0.75 0.229 0.56 3.79 0.574 -0.345 110 1.89 0.854 0.56 3.79 0.574 0.280
115 0.73 0.232 0.56 3.77 0.597 -0.365 115 1.83 0.865 0.56 3.77 0.597 0.268
Project:
Basin ID:
DETENTION VOLUME BY THE MODIFIED FAA METHOD
FCHA - Villages at Redwood
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.35, Released January 2015
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 50 100 150 200 250 300 350
Volume (acre-feet)
Duration (Minutes)
Inflow and Outflow Volumes vs. Rainfall Duration
Minor Storm Inflow Volume Minor Storm Outflow Volume Minor Storm Storage Volume Major Storm Inflow Volume Major Storm Outflow Volume Major Storm Storage Volume
1237-112-00 UD-Detention_v2.35.xls, Modified FAA 10/14/2015, 2:06 PM
Village on Redwood
Critical Pond Elevations (Basin D1)
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, June 2001 (Revised April 2008)
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)
4962.38 0 0.000 0.000 0.00 0.000
4963.0 2517 0.058 0.012 0.62 0.012
4964.0 6693 0.154 0.102 1.62 0.114
4965.0 9740 0.224 0.188 2.62 0.301
4966.0 12947 0.297 0.260 3.62 0.561
0.38 4965.28 ft
T.Alva
Interwest Consulting Group
1237-112-00
Acre-Ft Interpolates to an Elev. of
Acre-Ft Interpolates to an Elev. of
Required Water Quality Capture Volume =0
Required 100-yr Detention Volume (including WQCV) =
October 14, 2015
4962.00
4962.50
4963.00
4963.50
4964.00
4964.50
4965.00
4965.50
4966.00
4966.50
0.0 0.1 0.2 0.3 0.4 0.5 0.6
ELEVATION (FT)
DETENTION POND VOLUME (AC-FT)
DETENTION POND VOLUME
VERSUS ELEVATION
( )
3
AAAADepth 1 2 1 2
V
+ +
=
1237-112-00 PondCalcs.xls - Pond Stage Storage Page 1 of 1 Interwest Consulting Group
E
APPENDIX E — LOW IMPACT DEVELOPMENT CALCULATIONS
FCHA - Villages on Redwood
Low Impact Development
Design Engineer:
Design Firm:
Project Number:
Date:
DESIGN CRITERIA
Low Impact Development Summary
Pavement Area Summary
43,661 sqft
11,194 sqft
25.6%
Newly Added Impervious Area Summary
128,515 sqft
11,194 sqft
30,431 sqft
41,625 sqft
22,632 sqft
64,258 sqft
50.0%
Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, January 2010
Total Paved Area:
Permeable Paver Area:
Total Site Impervious Area:
Proposed Area of Pavers:
Additional Area Treated by Pavers:
Total Area Treated by Pavers:
Area to be Treated by Sand Filter:
Total Area Treated by LID:
Percent Impervious Area Treated by LID:
Percent Pavement Area as Permeable Pavers:
City of Fort Collins - Ordinance No. 152
- No less than 25% of any newly added pavement areas must be treated using a permeable pavement
technology that is considered an LID Technique, and
- No less than 50% of any newly added impervious area must be treated using one or a combination of LID
techniques
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 100.0 %
(100% if all paved and roofed areas upstream of sand filter)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 1.000
C) Water Quality Capture Volume (WQCV) Based on 12-hour Drain Time WQCV = 0.45 watershed inches
WQCV= 0.9 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including sand filter area) Area = 22,633 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 849 cu ft
VWQCV = 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 = 849 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = 850 cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth DWQCV = 1.0 ft
B) Sand Filter Side Slopes (Horizontal distance per unit vertical, Z = 4.00 ft / ft
4:1 or flatter preferred). Use "0" if sand filter has vertical walls.
C) Mimimum Filter Area (Flat Surface Area) AMin = 189 sq ft
D) Actual Filter Area AActual = 850 sq ft
E) Volume Provided VT = 850 cu ft
3. Filter Material
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 = N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Village on Redwood
Fort Collins, CO
Design Procedure Form: Sand Filter (SF)
J.Claeys
Interwest Consulting Group
October 14, 2015
Choose One
Choose One
18" CDOT Class C Filter Material
Other (Explain):
YES
NO
1237-112-00 UD-BMP_v3.03.xlsm, SF 10/14/2015, 11:29 AM
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?
6-7. Inlet / Outlet Works
A) Describe the type of energy dissipation at inlet points and means of
conveying flows in excess of the WQCV through the outlet
Notes:
Full Infiltration
Design Procedure Form: Sand Filter (SF)
J.Claeys
Interwest Consulting Group
October 14, 2015
Village on Redwood
Fort Collins, CO
Choose One
YES NO
1237-112-00 UD-BMP_v3.03.xlsm, SF 10/14/2015, 11:29 AM
Percolation Test Results
DEPTH DEPTH PERC
PERC MINUTES START END CHANGE RATE
HOLE (INCHES) (INCHES) (INCHES) (MPI)
1 10 22.88 24.75 1.88 5.3
10 24.75 26.25 1.50 6.7
10 26.25 27.50 1.25 8.0
10 27.50 28.63 1.13 8.9
10 28.63 29.75 1.13 8.9
10 29.75 30.88 1.13 8.9
10 20.50 22.38 1.88 5.3
10 22.38 24.13 1.75 5.7
2* 10 19.38 19.38 0.00 >80
10 19.38 19.50 0.13 80.0
10 19.50 19.50 0.00 >80
10 19.50 19.63 0.13 80.0
10 19.63 19.75 0.13 80.0
10 19.75 19.75 0.00 >80
10 19.75 19.88 0.13 80.0
10 19.88 20.00 0.13 80.0
3 10 20.25 22.00 1.75 5.7
10 22.00 23.63 1.63 6.2
10 23.63 25.25 1.63 6.2
10 25.25 26.63 1.38 7.3
10 26.63 27.88 1.25 8.0
10 27.88 29.25 1.38 7.3
10 29.25 30.13 0.88 11.4
10 30.13 31.00 0.88 11.4
4 10 17.25 18.63 1.38 7.3
10 18.63 19.88 1.25 8.0
10 19.78 21.00 1.22 8.2
10 21.00 22.00 1.00 10.0
10 22.00 23.13 1.13 8.9
10 23.13 24.00 0.88 11.4
10 24.00 24.88 0.88 11.4
10 16.88 18.00 1.13 8.9
5 10 22.00 24.25 2.25 4.4
10 24.25 26.38 2.13 4.7
10 26.38 28.25 1.88 5.3
10 28.25 29.88 1.63 6.2
10 29.88 31.25 1.38 7.3
10 31.25 32.63 1.38 7.3
10 32.63 33.88 1.25 8.0
10 33.88 35.13 1.25 8.0
6 10 22.88 31.25 8.38 1.2
10 31.25 38.00 6.75 1.5
10 28.25 35.25 7.00 1.4
10 35.25 41.75 6.50 1.5
10 41.75 45.00 3.25 3.1
10 21.75 30.50 8.75 1.1
10 30.50 37.63 7.13 1.4
10 37.63 41.63 4.00 2.5
Average Percolation Rate (mpi): 8.6
*Perc hole 2 was neglected for our average percolation rate
INTERWEST CONSULTING GROUP
FCHA REDWOOD DEVELOPMENT
CTL | T PROJECT NO. FC06667.001-130 FIGURE 3
120 0.71 0.234 0.56 3.75 0.620 -0.386 120 1.77 0.875 0.56 3.75 0.620 0.255
125 0.69 0.237 0.55 3.74 0.644 -0.407 125 1.72 0.885 0.55 3.74 0.644 0.241
130 0.67 0.240 0.55 3.73 0.667 -0.427 130 1.67 0.894 0.55 3.73 0.667 0.227
135 0.65 0.242 0.55 3.71 0.690 -0.448 135 1.63 0.903 0.55 3.71 0.690 0.213
140 0.63 0.244 0.55 3.70 0.714 -0.469 140 1.58 0.912 0.55 3.70 0.714 0.199
145 0.61 0.247 0.55 3.69 0.737 -0.490 145 1.54 0.921 0.55 3.69 0.737 0.184
150 0.60 0.249 0.54 3.68 0.760 -0.511 150 1.50 0.929 0.54 3.68 0.760 0.169
155 0.59 0.251 0.54 3.67 0.783 -0.532 155 1.47 0.937 0.54 3.67 0.783 0.154
160 0.57 0.253 0.54 3.66 0.807 -0.554 160 1.43 0.945 0.54 3.66 0.807 0.138
165 0.56 0.255 0.54 3.65 0.830 -0.575 165 1.40 0.952 0.54 3.65 0.830 0.122
170 0.55 0.257 0.54 3.64 0.853 -0.596 170 1.37 0.960 0.54 3.64 0.853 0.106
175 0.53 0.259 0.54 3.64 0.877 -0.618 175 1.34 0.967 0.54 3.64 0.877 0.090
180 0.52 0.261 0.54 3.63 0.900 -0.639 180 1.31 0.974 0.54 3.63 0.900 0.074
185 0.51 0.263 0.54 3.62 0.923 -0.660 185 1.29 0.981 0.54 3.62 0.923 0.057
190 0.50 0.265 0.53 3.62 0.946 -0.682 190 1.26 0.987 0.53 3.62 0.946 0.041
195 0.49 0.266 0.53 3.61 0.970 -0.703 195 1.24 0.994 0.53 3.61 0.970 0.024
200 0.48 0.268 0.53 3.60 0.993 -0.725 200 1.21 1.000 0.53 3.60 0.993 0.007
205 0.48 0.270 0.53 3.60 1.016 -0.747 205 1.19 1.006 0.53 3.60 1.016 -0.010
210 0.47 0.271 0.53 3.59 1.040 -0.768 210 1.17 1.012 0.53 3.59 1.040 -0.027
215 0.46 0.273 0.53 3.59 1.063 -0.790 215 1.15 1.018 0.53 3.59 1.063 -0.045
220 0.45 0.274 0.53 3.58 1.086 -0.812 220 1.13 1.024 0.53 3.58 1.086 -0.062
225 0.44 0.276 0.53 3.58 1.109 -0.834 225 1.11 1.030 0.53 3.58 1.109 -0.080
230 0.44 0.277 0.53 3.58 1.133 -0.855 230 1.09 1.035 0.53 3.58 1.133 -0.097
235 0.43 0.279 0.53 3.57 1.156 -0.877 235 1.08 1.041 0.53 3.57 1.156 -0.115
240 0.42 0.280 0.53 3.57 1.179 -0.899 240 1.06 1.046 0.53 3.57 1.179 -0.133
245 0.42 0.282 0.53 3.56 1.203 -0.921 245 1.04 1.052 0.53 3.56 1.203 -0.151
250 0.41 0.283 0.53 3.56 1.226 -0.943 250 1.03 1.057 0.53 3.56 1.226 -0.169
255 0.40 0.285 0.53 3.56 1.249 -0.965 255 1.01 1.062 0.53 3.56 1.249 -0.187
260 0.40 0.286 0.53 3.55 1.272 -0.987 260 1.00 1.067 0.53 3.55 1.272 -0.206
265 0.39 0.287 0.52 3.55 1.296 -1.009 265 0.98 1.072 0.52 3.55 1.296 -0.224
270 0.39 0.288 0.52 3.55 1.319 -1.031 270 0.97 1.077 0.52 3.55 1.319 -0.242
275 0.38 0.290 0.52 3.54 1.342 -1.053 275 0.96 1.082 0.52 3.54 1.342 -0.261
280 0.38 0.291 0.52 3.54 1.366 -1.075 280 0.94 1.086 0.52 3.54 1.366 -0.279
285 0.37 0.292 0.52 3.54 1.389 -1.097 285 0.93 1.091 0.52 3.54 1.389 -0.298
290 0.37 0.293 0.52 3.54 1.412 -1.119 290 0.92 1.095 0.52 3.54 1.412 -0.317
295 0.36 0.295 0.52 3.53 1.435 -1.141 295 0.91 1.100 0.52 3.53 1.435 -0.336
300 0.36 0.296 0.52 3.53 1.459 -1.163 300 0.89 1.104 0.52 3.53 1.459 -0.354
Mod. FAA Minor Storage Volume (cubic ft.) = 298 Mod. FAA Major Storage Volume (cubic ft.) = 16,352
Mod. FAA Minor Storage Volume (acre-ft.) = 0.0068 Mod. FAA Major Storage Volume (acre-ft.) = 0.3754
DETENTION VOLUME BY THE MODIFIED FAA METHOD
FCHA - Villages at Redwood
Determination of MAJOR Detention Volume Using Modified FAA Method
(For catchments less than 160 acres only. For larger catchments, use hydrograph routing method)
(NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.35, Released January 2015
Determination of MINOR Detention Volume Using Modified FAA Method
1237-112-00 UD-Detention_v2.35.xls, Modified FAA 10/14/2015, 2:06 PM
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(sq feet)
Sub-basin
Designation
Paved
Pavers
Land Use
Atotal
(sq feet)
Atotal
(acres)
Walks
Lawns (Heavy, 2-
7% Slope)
Aroof
(sq feet)
Awalk
(sq feet)
Apavers
(sq feet)
Alawn
(sq feet)
% Impervious values from Table RO-3 in the Urban Storm Drainage Criteria Manual
Runoff Coefficients and Frequency Adjustment Factors for City of Fort Collins - Storm Water Criteria Manual
T.Alva
Interwest Consulting Group
1237-112-00
October 14, 2015
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(sq feet)
Awalk
(sq feet)
Aroof
(sq feet)
Survey Area Data: Version 9, Sep 22, 2014
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
10/14/2015
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