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FINAL DRAINAGE AND EROSION
CONTROL REPORT
LITTLE BEARS CHILD CARE
FINAL DRAINAGE & EROSION
CONTROL REPORT
LITTLE BEARS CHILD CARE INC.
Prepared for:
Little Bears Child Care
1900 South Lemay Avenue
Fort Collins, CO 80525
Prepared by:
North Star Design
700 Automation Drive, Unit I
Windsor, Colorado 80550
(970) 686-6939
May 29, 2012
Job Number 331-01
May 29, 2012
Glen Schlueter
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80522
RE: Final Drainage and Erosion Control Report for Little Bears Child Care, Inc.
Dear Glen,
I am pleased to submit for your review and approval, this Final Drainage and Erosion Control
Report for the Little Bears Child Care project. I certify that this report for the drainage design of
the Little Bears 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.
Prepared by:
Patricia Kroetch P.E.
Project Manager
700 Automation Drive, Unit I
Windsor, CO 80550
Phone: 970-686-6939
Fax: 970-686-1188
iii
TABLE OF CONTENTS
TABLE OF CONTENTS ............................................................................................................... iii
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location ...................................................................................................................1
1.2 Description of Property ............................................................................................1
1.3 Major Basin Description ..........................................................................................2
1.4 Sub Basin Description .............................................................................................2
2. DRAINAGE DESIGN CRITERIA
2.1 Regulations ..............................................................................................................2
2.2 Development Criteria Reference and Constraints ...................................................2
2.3 Hydrologic Criteria ..................................................................................................3
2.4 Hydraulic Criteria ....................................................................................................3
3. DRAINAGE FACILITY DESIGN
3.1 General Concept ......................................................................................................3
3.2 Specific Flow Routing .............................................................................................3
3.3 Drainage Summary ..................................................................................................4
4. EROSION CONTROL
4.1 Written Analysis .....................................................................................................4
4.2 Stormwater Management Controls ..........................................................................6
4.3 Four Step BMP Selection Process ...........................................................................7
5. CONCLUSIONS
5.1 Compliance with Standards ....................................................................................8
5.2 Drainage Concept ....................................................................................................8
6. REFERENCES ....................................................................................................................9
APPENDICES
A Vicinity Map
B Hydrologic Computations
C Hydraulic Calculations
E Figures and Tables
1
1. GENERAL LOCATION AND DESCRIPTION
1.1. Location
The Little Bears Child Care project is located at 1247 Riverside Avenue and 1230
Elizabeth Street. The proposed project is located on the Riverside II Condo Amended
(1247 Riverside) and Lot 3, Viking I Subdivision (1230 Elizabeth) in the Northeast
Quarter of Section 13, Township 7 North, Range 69 West of the Sixth Principal
Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in
Appendix A.
This project is bounded on the northeast by Riverside Avenue, on the south by Elizabeth
Street and on all other boundaries by existing commercial development.
1.2. Description of Property
The project consists of approximately 0.85 acres of land inclusive of both lots. The
project site consists of an existing building, parking lot, walks and landscaping on the
Riverside II lot and a majority of these improvements will remain. Lot 3 is currently
undeveloped and ground cover consists of grasses and weeds. This lot will be developed
as a playground for use by the proposed child care facility on the Riverside II lot.
Existing vegetation at 1247 Riverside site consists of mature trees, established grasses
and other landscaping along Riverside Avenue and adjacent to the existing building. No
developed landscaping exists on the site at 1230 Elizabeth. Stormwater runoff currently
sheet flows to the adjacent streets and is conveyed in the curb and gutter to the existing
storm inlets and ultimately conveyed to the Poudre River. The existing slopes onsite are
approximately 1% to 3% to the adjacent streets.
Currently water quality and detention measures have not been provided for the existing
development and, since only minor improvements are proposed on the Riverside lot, no
detention or water quality enhancement measures are being proposed for the Riverside
lot. For the proposed development on the Elizabeth lot, the City of Fort Collins
Stormwater Criteria allows a site to construct up to 1,000 square feet of additional
impervious area before the City requires water quality and detention. On the Elizabeth
lot, it is proposed to construct approximately 3,000 square feet of concrete walk in the
playground area. Since there is a greater than 1,000 square feet of impervious area being
2
constructed, water quality and detention will be required for the new impervious area on
the playground.
The site has been divided into 2 drainage basins coinciding with the existing lot
definitions. The majority of the improvements to the site will occur in Basin 1 which is
the Elizabeth lot and encompasses the proposed playground.
DRAINAGE BASINS AND SUB-BASINS
1.3. Major Basin Description
This site is located in the Spring Creek Basin. The site is not located within a City or
FEMA designated 100 year floodplain.
1.4. Sub-basin Description
The existing Riverside lot (Basin 2) drains to Riverside Avenue via sheet flow, piped
flow and channelized flow. The drainage patterns for this lot will not be altered. Runoff
from the Elizabeth lot (Basin 1) currently flows north and then east in a grassed swale to
a concrete channel that conveys the runoff to McHugh Street. This drainage pattern will
be maintained to the greatest extent possible. See Section 4 of this report for specific
details for each sub-basin.
2. DRAINAGE DESIGN CRITERIA
2.1. Regulations
Drainage for this site has been designed to meet or exceed the “City of Fort Collins
Stormwater Criteria Manual” specifications and the City of Fort Collins Spring Creek
Basin Master Plan. Where applicable, the criteria established in the “Urban Storm
Drainage Criteria Manual” (UDFCD), 2001 has been used.
2.2. Development Criteria Reference and Constraints
Stormwater runoff from this site has been routed to conform to the requirements of the
City Stormwater Department. Detention is required for this site and will be provided for
Basin 1.
3
Water quality facilities are required for the improvements and are being provided by
water quality extended detention within the proposed pond.
2.3. Hydrologic Criteria
Runoff computations were prepared for the 2 year and 10 year minor and 100 year major
storm frequency utilizing the Rational Method. All hydrologic calculations associated
with the basins are included in Appendix B of this report.
2.4. Hydraulic Criteria
All hydraulic calculations within this report have been prepared in accordance with the
City of Fort Collins Drainage Criteria, Urban Area Drainage Criteria Manual and are
included in Appendix C.
3. DRAINAGE FACILITY DESIGN
3.1. General Concept
All of the runoff from this site historically flows to Riverside Avenue. With the
construction of the proposed improvements, onsite stormwater from Basin 1 will be
collected in the detention pond and released at the 2 year historic rate. Runoff from
Basin 2 will not be altered.
3.2. Specific Flow Routing
A summary of the drainage patterns within each basin is provided in the following
paragraphs.
Basin 1 is located in the south part of the site and includes all of Lot 3, Viking I
Subdivision. The playground for the child care facility is proposed to be developed on
this lot. Runoff from this basin will sheet flow to the north and enter the proposed
detention & water quality pond. Runoff will be attenuated to the 2 year historic relase
rate and then be released to the east and into an existing concrete channel that will
convey the runoff to McHugh Street.
Basin 2 is located in the north portion the site. This basin includes an existing building,
existing asphalt drive and parking lot, existing concrete sidewalks and significant
established landscape improvements. Runoff is routed via curb and gutter to an existing
4
pipe in the parking lot that will convey the water east to a sidewalk chase and into
Riverside Avenue. A small portion of the runoff will be collected in the existing concrete
channel on the south side of the existing building and will also flow to McHugh Street.
3.3. Drainage Summary
Drainage for this site was designed to conform to the City of Fort Collins stormwater
requirements. Detention and water quality extended detention is provided for Basin 1
and disturbance in Basin 2 will be kept to a minimum.
4. EROSION CONTROL
4.1. Written Analysis
A. Developed Conditions
A portion of the site is being used as it is currently developed and a portion of the
site is being developed into a playground to be used in conjunction with the
remainder of the site. The amount of disturbance on the site is approximately 0.36
acres which will not require the site to obtain a State Stormwater Mangement
Permit.
B. Rainfall Erodibility
This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City
of Fort Collins. A majority of the site has been developed with building,
pavement and landscaping which will be maintained to the greatest extent
possible, therefore further reducing the site erodibility.
C. Sediment Control Methods
Erosion and sediment control BMP’s are the BMP’s intended to control the
amount of sediment becoming suspended and transported off-site by on-site
stormwater runoff. Drainage and Erosion/Sediment Control Standard to be
followed shall be the City of Fort Collins’s Stormwater Criteria Manual and
Sediment/Erosion Control Standards at the time of commencing construction.
Temporary BMP’s
Structural Practices: All BMP’s shall be inspected and repaired or replaced as
5
required to satisfy the City Erosion Control Inspector. All temporary BMP’s
must be maintained and repaired as needed to assure continued performance of
their intended function. Temporary, structural erosion and sediment control
BMP’s are described in detail in the following paragraphs.
Perimeter silt fence shall be installed along the perimeter of the project as shown
on the Drainage and Erosion Control plan. Silt fence shall be in place prior to
commencement of any construction activity. During clearing and grubbing
necessary for perimeter silt fence installation, all cleared material shall be placed
on the uphill side of the 6”x6” trench described in City of Fort Collins Silt Fence
Detail, so that if erosion occurs during the silt fence installation from the cleared
material, sediment/erosion will be trapped in the above mentioned trench and not
transported downstream.
Wattles shall be implemented in swales and in the curb and gutter as shown on
the Drainage and Sediment/Erosion Control Plan. Wattles shall be installed upon
completion of overlot grading.
Non-Structural Practices: Temporary non-structural BMP’s for the site will
consist of water trucks as needed.
Water trucks shall apply water to the ground to wet the soil to reduce the amount
of wind erosion and dust being transported off-site. Watering will occur when
environmental conditions are conducive to causing excessive amounts of dust and
wind erosion.
Permanent BMP’s
Permanent BMP’s include vegetative swales, a water quality pond, the
completion of all site improvements and permanent vegetative soil stabilization.
No soils in areas outside project street rights-of-way shall remain exposed by land
disturbing activity for more than thirty (30) days before required temporary or
permanent erosion control (e.g. seed/mulch, landscaping, etc.) is installed unless
otherwise approved by the City of Fort Collins Erosion Control Inspector.
Final stabilization shall be considered achieved once all proposed site
improvements have been installed, proposed grassed areas have been permanently
seeded, and the vegetation is considered established. Vegetation shall not be
6
considered established until a ground cover is achieved which is demonstrated to
be mature enough to control soil erosion, typically a minimum of 70%.
Tracking Mud on City Streets
It is unlawful to track or cause to be tracked mud or other debris onto city streets
or public rights-of-way. Wherever construction vehicles access paved public
roads, provisions must be made to minimize the transport of sediment (mud) by
runoff or vehicles tracking onto the paved surface. The contractor will be
responsible for clearing mud tracked onto city streets on a daily basis and after
any rain event which causes sediment to be transported offsite.
Maintenance
All erosion and sediment control practices shall be maintained, repaired, and/or
replaced as needed to ensure the continued performance of their intended
function. Temporary erosion and sediment control practices shall be inspected at
least once every two weeks and after any significant storm event. Permanent
erosion and sediment control practices shall be inspected at least twice per year
and after any significant storm event. A significant storm event is a storm event
that causes runoff.
4.2 Stormwater Management Controls
A. SWMP Administrator
The SWMP Administrator for this site is Sean Rogers, Hillside Construction, 970-
567-1821.
B. Potential Pollutant Sources
Disturbed soils shall be watered to prevent air borne sediment transport. No soils
are anticipated to be stored on site.
Vehicle tracking of mud will require the streets to be cleaned on a daily basis. No
vehicle tracking control pad is being proposed but may be required by the City
Erosion Control Inspector if tracking of mud becomes problematic.
Loading and unloading of materials will not occur on this site. Materials will be
stored in the existing building.
7
Equipment will not be maintained or fueled on site. A porta-potty will be
provided for the construction workers on site and will be maintained by a
qualified waste management company.
The majority of the site construction will be installation of concrete for the
playground and for the sidewalk along Riverside. If concrete construction exceeds
one day in duration a concrete washout will be installed on site per the Drainage
and Erosion Control Plan. No dedicated asphalt or concrete batch plants will be
allowed on site.
C. Dry Land Vegetation
The onsite soils are Kim Loam and Satanta Loam which are well drained and
have a moderately high to high capacity to transmit water. It is anticipated that the
soil will not remain disturbed for more than 30 days but, if that does occur, the
dry land seed mix specified on the Drainage and Erosion Control Plan will be
installed. Final landscape treatments (seeded and sodded areas) and the
anticipated soil amendments are shown on the Landscape Plan.
D. Sequence of Construction Activities
Construction Activity EC measures implemented
Strip ground cover Silt Fence around perimeter
Grading of site to final sub grade Wattles in concrete channels
And water truck as needed
Install concrete sidewalk & outlet structure Concrete washout if needed
Install playground equipment Maintain EC measures above
Install seed/sod/trees per the landscape plan Remove silt fence & washout
E. Erosion Control Security Calculations
Refer to calculations in the Appendix.
4.3 Four Step BMP Selection Process
A. Employ Runoff Reduction Practices
Runoff from the playground is primarily from the concrete sidewalks and play
areas. This runoff is routed through the grassed areas prior to enter the detention
area. This routing will provide additional opportunities for particulates to be
8
removed from the runoff and will slow the runoff time allowing the water to
percolate into the pervious areas to the greatest extent possible. Existing
amenities are being preserved (including existing grass and trees) on the
Riverside lot in every possible location which will minimize site disturbances.
B. Implement BMPS with WQ Capture Volume & Slow Release
The site will include a water quality extended detention element in the detention
pond which will provide additional capture volume and a slow release through a
restriction plate.
C. Stabilize Drainageways
The conveyances utilized for this site include an existing pipe which discharges
into a concrete channel on the Riverside lot. This situation will remain although
the metal sidewalk culvert will be removed and replaced. On the Elizabeth lot, a
grassed swale will be used to convey water adjacent to the playground and will
route the water to the detention pond. The release from the detention pond will
discharge into an existing concrete channel that will convey the water to McHugh
Street. In essence, all drainageways on site will be grassed or concrete lined.
D. Implement Source Control BMPS
No permanent contamination sources are proposed on site. The water quality
element of the detention pond will address potential sediment transport from the
site which would be the primary contamination source.
5. CONCLUSIONS
5.1. Compliance with Standards
All computations that have been completed within this report are in compliance with the
City of Fort Collins Erosion Control Reference Manual for Construction Sites and the
City of Fort Collins Stormwater Criteria Manual.
5.2. Drainage Concept
The proposed drainage concepts presented in this report, and on the construction plans,
adequately provide for stormwater quality treatment for the proposed improvements and
9
to minimize the disturbance to the existing site. The site is designed to convey developed
playground flows to the proposed detention and water quality pond and ultimately into
McHugh Street.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit will be required.
10
6. REFERENCES
1. City of Fort Collins, “Storm Drainage Criteria Manual”, (SDCM), dated March
1999.
2. Urban Drainage and Flood Control District, “Urban Storm Drainage Criteria
Manual”, Volumes 1 and 2, dated June 2001, and Volume 3 dated September
2001.
APPENDIX A
VICINITY MAP
B
APPENDIX B
HYDROLOGIC COMPUTATIONS
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, CO 80550
LOCATION: Little Bears
PROJECT NO: 331-01
COMPUTATIONS BY: PPK
DATE: 5/29/2012
Recommended % Impervious from Urban Storm Drainage Criteria Manual
%
Impervious
Roofs: 90%
Streets and Parking (Asphalt) 100%
Concrete Drives and Walks 90%
Packed Gravel: 40%
Landscaped Areas (Clayey soil, 0-1% slopes): 0%
SUBBASIN TOTAL TOTAL ROOF ASPHALT CONCRETE GRAVEL LANDSCAPE % RUNOFF RUNOFF RUNOFF RUNOFF
ID AREA AREA AREA AREA AREA AREA AREA Impervious COEFF. COEFF. COEFF. COEFF.
(ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) C2 C5 C10 C100
1 (exist) 0.36 15,498 0 694 0 1115 13,689 7% 0.09 0.20 0.29 0.52
1 (playground) 0.36 15,498 0 694 2,967 0 11,837 22% 0.18 0.27 0.35 0.56
2 (existing lot/bldg) 0.51 22,124 6,260 7,690 1,160 0 7,014 65% 0.45 0.49 0.54 0.65
RUNOFF COEFFICIENTS & % IMPERVIOUS
Flow.xls Cval
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, CO 80550
LOCATION: Little Bears
PROJECT NO: 331-01
COMPUTATIONS BY: PPK
DATE: 5/29/2012
SUB-BASIN DATA INITIAL / OVERLAND TIME TRAVEL TIME / GUTTER OR CHANNEL FLOW tc CHECK FINAL REMARKS
(ti)(tt) (URBANIZED BASIN) tc
DESIGN SUBBASIN Area C5 Length Slope ti Length Slope Chan. Cv Vel. tt tc = Total L tc=(l/180)+10
POINT ID (ac) (ft) (ft/ft) (min) (ft) (ft/ft) Type (ft/s) (min) ti + tt (ft) (min) (min)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)
1 1 (exist) 0.36 0.20 142 0.028 14.0 40 0.005 E 15 1.1 0.6 14.6 182 11.0 11.0
1 1 (playground) 0.36 0.27 117 0.020 13.1 75 0.005 E 15 1.1 1.2 14.3 192 11.1 11.1
2 2 (existing lot/bldg) 0.51 0.49 90 0.010 10.6 130 0.005 F 20 1.4 1.5 12.1 220 11.2 11.2
EQUATIONS: Channel Type Cv
tc = t
i + tt
A 2.5
B 5.0
ti = [0.395 (1.1 - C
5 ) L
0.5
] / S
1/3
C 7.0
D 10.0
tt = L/V V = C
v*S
0.5
E 15.0
F 20.0
final tc = minimum of t
i + tt
and urbanized basin check
minimum tc = 5 minutes
TIME OF CONCENTRATION
Paved
Grassed Waterway
Bare Ground
Short Pasture/ Lawn
Tillage / Field
Heavy Meadow
Flow.xls TOC5
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, CO 80550
LOCATION: Little Bears
PROJECT NO: 331-01
COMPUTATIONS BY: PPK
DATE: 5/29/2012
DIRECT RUNOFF TOTAL Inlet Capacity REMARKS
RATIONAL METHOD PEAK RUNOFF
(2-YEAR)
DESIGN SUBBASIN A C2 tc iQ2 Q2 Total
POINT ID
(ac) (min) (in/hr) (cfs) (cfs) (cfs)
1 1 (exist) 0.36 0.09 11.0 2.14 0.07 0.1
1 1 (playground) 0.36 0.18 11.1 2.14 0.14 0.1
2 2 (existing lot/bldg) 0.51 0.45 11.2 2.14 0.48 0.5
Q = C i A
Q = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from IDF curve
A = drainage area (acres)
Flow.xls Q2
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, CO 80550
LOCATION: Little Bears
PROJECT NO: 331-01
COMPUTATIONS BY: PPK
DATE: 5/29/2012
DIRECT RUNOFF TOTAL Inlet Capacity REMARKS
DESIGN SUBBASIN A C10 tc iQ10 Q10 Total
POINT ID
(ac) (min) (in/hr) (cfs) (cfs) (cfs)
1 1 (exist) 0.36 0.29 11.0 3.66 0.38 0.4
1 1 (playground) 0.36 0.35 11.1 3.65 0.46 0.5
2 2 (existing lot/bldg) 0.51 0.54 11.2 3.64 1.00 1.0
Q = C i A
Q = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from IDF curve
A = drainage area (acres)
RATIONAL METHOD PEAK RUNOFF
(10-YEAR)
Flow.xls Q10
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, CO 80550
LOCATION: Little Bears
PROJECT NO: 331-01
COMPUTATIONS BY: PPK
DATE: 5/29/2012
DIRECT RUNOFF TOTAL Inlet Capacity REMARKS
DESIGN SUBBASIN A C100 t
c iQ100
Q100 Total
POINT ID
(ac) (min) (in/hr) (cfs) (cfs) (cfs)
RATIONAL METHOD PEAK RUNOFF
(100-YEAR)
1 1 (exist) 0.36 0.52 11.0 7.48 1.40 1.4
1 1 (playground) 0.36 0.56 11.1 7.46 1.47 1.5
2 2 (existing lot/bldg) 0.51 0.65 11.2 7.44 2.47 2.5
Q = C i A
Q = peak discharge (cfs)
C = runoff coefficient
i = rainfall intensity (in/hr) from IDF curve
A = drainage area (acres)
Flow.xls Q100
C
APPENDIX C
HYDRAULIC CALCULATIONS
Project:
Basin ID:
Design Information (Input):
Catchment Drainage Imperviousness Ia = 22.00 percent
Catchment Drainage Area A = 0.3600 acres
Predevelopment NRCS Soil Group Type = A A, B, C, or D
Return Period for Detention Control T = 2 years (2, 5, 10, 25, 50, or 100)
Time of Concentration of Watershed Tc = 11 minutes
Allowable Unit Release Rate (See Table A) q = 0.28 cfs/acre
One-hour Precipitation P1 = 0.95 inches
Design Rainfall IDF Formula I = C1* P1/(C2+Tc)^C3
Coefficient One C1 = 28.50
Coefficient Two C2 = 10.00
Coefficient Three C3 = 0.79
Determination of Average Outflow from the Basin (Calculated):
Runoff Coefficient C = 0.07
Inflow Peak Runoff Qp-in = 0.06 cfs
Allowable Peak Outflow Rate Qp-out = 0.10 cfs
Ratio of Qp-out/Qp-in Ratio = 1.63
5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes)
Rainfall Rainfall Inflow Average Outflow Storage Adjustment Average Outflow Storage
Duration Intensity Volume Outflow Volume Volume Factor Outflow Volume Volume
minutes inches / hr cubic feet (FAA, cfs) (FAA, cf) (FAA, cf) (Modified) (Mod, cfs) (Mod, cf) (Mod, cf)
(input) (output) (output) (output) (output) (output) (output) (output) (output) (output)
5 3.19 24 0.10 30 -6 1.00 0.10 30 -6
10 2.54 38 0.10 60 -22 1.00 0.10 60 -22
15 2.13 48 0.10 90 -42 0.87 0.09 78 -30
20 1.84 56 0.10 120 -64 0.78 0.08 93 -38
25 1.63 62 0.10 150 -88 0.72 0.07 108 -47
30 1.47 67 0.10 180 -113 0.69 0.07 123 -57
35 1.34 71 0.10 210 -139 0.66 0.07 138 -67
40 1.23 74 0.10 240 -166 0.64 0.06 153 -79
45 1.14 78 0.10 270 -192 0.62 0.06 168 -91
50 1.07 81 0.10 300 -219 0.61 0.06 183 -103
55 1.00 83 0.10 330 -247 0.60 0.06 198 -115
60 0.94 86 0.10 360 -274 0.59 0.06 213 -128
65 0.89 88 0.10 390 -302 0.59 0.06 228 -140
70 0.85 90 0.10 420 -330 0.58 0.06 243 -153
75 0.81 92 0.10 450 -358 0.57 0.06 258 -166
80 0.77 94 0.10 480 -386 0.57 0.06 273 -180
85 0.74 95 0.10 510 -415 0.57 0.06 288 -193
90 0.71 97 0.10 540 -443 0.56 0.06 303 -206
95 0.69 98 0.10 570 -472 0.56 0.06 318 -220
100 0.66 100 0.10 600 -500 0.56 0.06 333 -233
105 0.64 101 0.10 630 -529 0.55 0.06 348 -247
110 0.62 103 0.10 660 -557 0.55 0.06 363 -261
115 0.60 104 0.10 690 -586 0.55 0.05 378 -274
120 0.58 105 0.10 720 -615 0.55 0.05 393 -288
125 0.56 106 0.10 750 -644 0.54 0.05 408 -302
130 0.55 107 0.10 780 -673 0.54 0.05 423 -316
135 0.53 108 0.10 810 -702 0.54 0.05 438 -330
140 0.52 109 0.10 840 -731 0.54 0.05 453 -344
145 0.50 110 0.10 870 -760 0.54 0.05 468 -358
150 0.49 111 0.10 900 -789 0.54 0.05 483 -372
155 0.48 112 0.10 930 -818 0.54 0.05 498 -386
160 0.47 113 0.10 960 -847 0.53 0.05 513 -400
165 0.46 114 0.10 990 -876 0.53 0.05 528 -414
170 0.45 115 0.10 1,020 -905 0.53 0.05 543 -428
175 0.44 116 0.10 1,050 -934 0.53 0.05 558 -442
180 0.43 117 0.10 1,080 -963 0.53 0.05 573 -457
Project:
Basin ID:
Rainfall Storage Average Outflow
Duration Volume Outflow Volume
minutes cubic feet cfs cubic feet
(input) (output) (Modified) (Modified)
5.00 -6 0.10 30
10.00 -22 0.10 60
15.00 -30 0.09 78
20.00 -38 0.08 93
25.00 -47 0.07 108
30.00 -57 0.07 123
35.00 -67 0.07 138
40.00 -79 0.06 153
45.00 -91 0.06 168
50.00 -103 0.06 183
55.00 -115 0.06 198
60.00 -128 0.06 213
65.00 -140 0.06 228
70.00 -153 0.06 243
75.00 -166 0.06 258
80.00 -180 0.06 273
85.00 -193 0.06 288
90.00 -206 0.06 303
95.00 -220 0.06 318
100.00 -233 0.06 333
105.00 -247 0.06 348
110.00 -261 0.06 363
115.00 -274 0.05 378
120.00 -288 0.05 393
125.00 -302 0.05 408
130.00 -316 0.05 423
135.00 -330 0.05 438
140.00 -344 0.05 453
145.00 -358 0.05 468
150.00 -372 0.05 483
155.00 -386 0.05 498
160.00 -400 0.05 513
165.00 -414 0.05 528
170.00 -428 0.05 543
175.00 -442 0.05 558
180.00 -457 0.05 573
185.00 -471 0.05 588
UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.02, Released January 2007
1 (Playground)
MINOR DETENTION VOLUME BY FAA & MODIFIED FAA METHOD
(See USDCM Volume I Runoff Chapter for description of method)
Little Bears Day Care
0
200
400
600
800
1,000
1,200
0 20 40 60 80 100 120 140 160 180 200
Volume (Cubic Feet)
Duration (Minutes)
Inflow and Outflow Volumes vs. Rainfall Duration
Intersection of Modified and FAA Outflow Plots is at maximum detention volume
Project:
Basin ID:
Design Information (Input):
Catchment Drainage Imperviousness Ia = 22.00 percent
Catchment Drainage Area A = 0.3600 acres
Predevelopment NRCS Soil Group Type = A A, B, C, or D
Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100)
Time of Concentration of Watershed Tc = 11 minutes
Allowable Unit Release Rate (See Table A) q = 0.28 cfs/acre
One-hour Precipitation P1 = 2.61 inches
Design Rainfall IDF Formula I = C1* P1/(C2+Tc)^C3
Coefficient One C1 = 28.50
Coefficient Two C2 = 10.00
Coefficient Three C3 = 0.79
Determination of Average Outflow from the Basin (Calculated):
Runoff Coefficient C = 0.34
Inflow Peak Runoff Qp-in = 0.82 cfs
Allowable Peak Outflow Rate Qp-out = 0.10 cfs
Ratio of Qp-out/Qp-in Ratio = 0.12
5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes)
Rainfall Rainfall Inflow Average Outflow Storage Adjustment Average Outflow Storage
Duration Intensity Volume Outflow Volume Volume Factor Outflow Volume Volume
minutes inches / hr cubic feet (FAA, cfs) (FAA, cf) (FAA, cf) (Modified) (Mod, cfs) (Mod, cf) (Mod, cf)
(input) (output) (output) (output) (output) (output) (output) (output) (output) (output)
5 8.76 322 0.05 16 305 1.00 0.10 30 292
10 6.98 512 0.05 33 480 1.00 0.10 60 452
15 5.85 644 0.05 49 595 0.87 0.09 78 566
20 5.06 744 0.05 65 679 0.78 0.08 93 651
25 4.48 823 0.05 82 742 0.72 0.07 108 715
30 4.04 889 0.05 98 791 0.69 0.07 123 766
35 3.68 945 0.05 114 831 0.66 0.07 138 807
40 3.38 994 0.05 131 863 0.64 0.06 153 840
45 3.14 1,037 0.05 147 890 0.62 0.06 168 869
50 2.93 1,076 0.05 163 912 0.61 0.06 183 892
55 2.75 1,111 0.05 180 931 0.60 0.06 198 912
60 2.59 1,143 0.05 196 947 0.59 0.06 213 929
65 2.46 1,172 0.05 212 960 0.59 0.06 228 944
70 2.33 1,200 0.05 229 971 0.58 0.06 243 956
75 2.22 1,225 0.05 245 980 0.57 0.06 258 967
80 2.13 1,249 0.05 261 988 0.57 0.06 273 976
85 2.04 1,272 0.05 278 994 0.57 0.06 288 984
90 1.96 1,293 0.05 294 999 0.56 0.06 303 990
95 1.88 1,313 0.05 310 1,003 0.56 0.06 318 995
100 1.81 1,333 0.05 327 1,006 0.56 0.06 333 999
105 1.75 1,351 0.05 343 1,008 0.55 0.06 348 1,003
110 1.69 1,369 0.05 359 1,009 0.55 0.06 363 1,005
115 1.64 1,385 0.05 376 1,010 0.55 0.05 378 1,007
120 1.59 1,401 0.05 392 1,010 0.55 0.05 393 1,008
125 1.54 1,417 0.05 408 1,009 0.54 0.05 408 1,009
130 1.50 1,432 0.05 425 1,007 0.54 0.05 423 1,009
135 1.46 1,446 0.05 441 1,005 0.54 0.05 438 1,008
140 1.42 1,460 0.05 457 1,003 0.54 0.05 453 1,007
145 1.38 1,474 0.05 474 1,000 0.54 0.05 468 1,005
150 1.35 1,487 0.05 490 997 0.54 0.05 483 1,004
155 1.32 1,499 0.05 506 993 0.54 0.05 498 1,001
160 1.29 1,512 0.05 523 989 0.53 0.05 513 998
165 1.26 1,524 0.05 539 985 0.53 0.05 528 995
170 1.23 1,535 0.05 555 980 0.53 0.05 543 992
175 1.20 1,547 0.05 572 975 0.53 0.05 558 988
180 1.18 1,558 0.05 588 970 0.53 0.05 573 984
Project:
Basin ID:
Rainfall Storage Average Outflow
Duration Volume Outflow Volume
minutes cubic feet cfs cubic feet
(input) (output) (Modified) (Modified)
5.00 292 0.10 30
10.00 452 0.10 60
15.00 566 0.09 78
20.00 651 0.08 93
25.00 715 0.07 108
30.00 766 0.07 123
35.00 807 0.07 138
40.00 840 0.06 153
45.00 869 0.06 168
50.00 892 0.06 183
55.00 912 0.06 198
60.00 929 0.06 213
65.00 944 0.06 228
70.00 956 0.06 243
75.00 967 0.06 258
80.00 976 0.06 273
85.00 984 0.06 288
90.00 990 0.06 303
95.00 995 0.06 318
100.00 999 0.06 333
105.00 1,003 0.06 348
110.00 1,005 0.06 363
115.00 1,007 0.05 378
120.00 1,008 0.05 393
125.00 1,009 0.05 408
130.00 1,009 0.05 423
135.00 1,008 0.05 438
140.00 1,007 0.05 453
145.00 1,005 0.05 468
150.00 1,004 0.05 483
155.00 1,001 0.05 498
160.00 998 0.05 513
165.00 995 0.05 528
170.00 992 0.05 543
175.00 988 0.05 558
180.00 984 0.05 573
185.00 980 0.05 588
UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.02, Released January 2007
1 (Playground)
MAJOR DETENTION VOLUME BY FAA & MODIFIED FAA METHOD
(See USDCM Volume I Runoff Chapter for description of method)
Little Bears Day Care
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
0 20 40 60 80 100 120 140 160 180 200
Volume (Cubic Feet)
Project:
Basin ID:
WQCV Design Volume (Input):
Catchment Imperviousness, Ia = 22.0 percent Diameter of holes, D = 0.100 in. Time to Drain the Pond = 40 hours
Catchment Area, A = 0.3600 acres Number of holes per layer, N = 1
Depth at WQCV outlet above lowest perforation, H = 12.00 inches OR
Number of layers, NL = 3
Vertical distance between layers, h = 4.00 inches Height of slot, H = in.
Orifice discharge coefficient, Co = 0.65 Width of slot, W = in.
Outlet Design Information (Output):
Water Quality Capture Volume (1.0 * (0.91 * I^3 - 1.19 * I^2 + 0.78 * I)), WQCV = 0.12 watershed inches
Design Volume (WQCV / 12 * Area * 1.2) Vol = 0.0045 acre-feet 0.00
Recommended maximum outlet area per layer (based on 4" vertical spacing of layers), Ao = 0.0201 square inches
Total opening area at each layer based on user-input above, Ao = 0.01 square inches
Total opening area at each layer based on user-input above, Ao = 0.0001 square feet
Calculation of Collection Capacity :
Stage Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Layer 7 Layer 8 Layer 9 Layer 10 Layer 11 Layer 12 Layer 13 Layer 14 Layer 15 Layer 16 Layer 17 Layer 18 Flow
ft 53.20 53.53 53.87 cfs
(input)
53.20 0.000 0.000 0.000 0.00
53.30 0.000 0.000 0.000 0.00
53.40 0.000 0.000 0.000 0.00
53.50 0.000 0.000 0.000 0.00
53.60 0.000 0.000 0.000 0.00
53.70 0.000 0.000 0.000 0.00
53.80 0.000 0.000 0.000 0.00
53.90 0.000 0.000 0.000 0.00
54.00 0.000 0.000 0.000 0.00
54.10 0.000 0.000 0.000 0.00
54.20 0.000 0.000 0.000 0.00
54.30 0.000 0.000 0.000 0.00
54.40 0.000 0.000 0.000 0.00
54.50 0.000 0.000 0.000 0.00
54.60 0.000 0.000 0.000 0.00
54.70 0.000 0.000 0.000 0.00
54.80 0.000 0.000 0.000 0.00
54.90 0.000 0.000 0.000 0.00
55.00 0.000 0.000 0.000 0.00
55.10 0.000 0.000 0.000 0.00
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Detention Pond - Stage/Storage
LOCATION: Little Bears Day Care
PROJECT NO: 331-01
COMPUTATIONS BY: ppk
DATE: 5/29/2012
V = 1/3 d ( A + B + sqrt(A*B))
where V = volume between contours, ft3
d = depth between contours, ft
A = surface area of contour
Detention Volume Required 1010 Cu-Ft
Water quality Volume Required 196 Cu-Ft
Surface Incremental Total
Stage Area Storage Storage
(ft) (ft2) (ac-ft) (ac-ft)
4953.2 0
4953.6 1475 197 197 <- WQ Volume
4954 4954.0 3135 888 888
4954.1 3588 336 1224 <- Det Volume
4954.5 5580 2322 3546 <- Top of Berm
Detpond_rev.xls
Detention Pond Outlet Sizing
(100 yr event)
LOCATION: Little Bears Day Care
PROJECT NO: 331-01
COMPUTATIONS BY: ppk
DATE: 5/29/2012
Submerged Orifice Outlet:
release rate is described by the orifice equation,
Qo = CoAo sqrt( 2g(h-Eo))
where Qo = orifice outflow (cfs)
Co = orifice discharge coefficient
g = gravitational acceleration = 32.20 ft/s
Ao = effective area of the orifice (ft2)
Eo = geometric center elevation of the orifice
h = water surface elevation (ft)
Qo = 0.10 cfs
outlet pipe dia = D = 8.0 in
Invert elev. = 4953.18 ft
Eo = 4953.26 ft
h = 4954.10 ft - 100 yr WSEL
Co = 0.65
solve for effective area of orifice using the orifice equation
Ao = 0.021 ft2
= 3.0 in2
orifice dia. = d = 1.96 in
Use d = 2 in
A o = 0.022 ft 2 = 3.14 in 2
Qmax = 0.10 cfs
Detpond_rev.xls
Emergency Overflow Spillway Sizing
LOCATION: Little Bears Day Care
PROJECT NO: 331-01
COMPUTATIONS BY: ppk
DATE: 5/29/2012
Equation for flow over a broad crested weir
Q = CLH3/2
where C = weir coefficient = 3.0
H = overflow height
L = length of the weir
Spillways will be designed with 0.5 ft max flow depth, thus H = 0.5 ft
Q (100) = 1.5 cfs
Spill elev = 4954.10 ft 100 yr WSEL = 4954.10 ft
Min top of berm elev elev.= 4954 4954.50
Weir length required:
L = 1 ft
Use L = 4 ft
v = 0.55 ft/s
Detpond_rev.xls
D
APPENDIX D
FIGURES AND TABLES
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Central Elevations of Layers of Holes in feet
Collection Capacity for Each Layer of Holes in cfs
STAGE-DISCHARGE SIZING OF THE WATER QUALITY CAPTURE VOLUME (WQCV) OUTLET
Little Bears Day Car
1 (playground)
Water Quality Capture Volume Method Selected (40-
Hour Release)
UD-Detention_v2.02.xls, WQCV 5/29/2012, 3:38 PM
Duration (Minutes)
Inflow and Outflow Volumes vs. Rainfall Duration
Intersection of Modified and FAA Outflow Plots is at maximum detention volume
Inflow Volume Modified Outflow Volume FAA Outflow Volume
UD-Detention_v2.02.xls, Modified FAA 5/29/2012, 3:37 PM
185 1.15 1,568 0.05 604 964 0.53 0.05 588 980
FAA Major Storage Volume (cubic ft.) = 1,010 Mod. FAA Major Storage Volume (cubic ft.) = 1,009
FAA Major Storage Volume (acre-ft.) = 0.0232 Mod. FAA Major Storage Volume (acre-ft.) = 0.0232
UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.02, Released January 2007
Little Bears Day Care
1 (Playground)
(Note: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
The user must fill in all of the blue cells for these sheets to function.
Determination of MAJOR Detention Volume Using FAA & Modified FAA Method
MAJOR DETENTION VOLUME BY FAA & MODIFIED FAA METHOD
(See USDCM Volume I Runoff Chapter for description of method)
(For catchments less than 160 acres only. For larger catchments, use hydrograph routing method)
UD-Detention_v2.02.xls, Modified FAA 5/29/2012, 3:37 PM
Inflow Volume Modified Outflow Volume FAA Outflow Volume
UD-Detention_v2.02.xls, Modified FAA 5/29/2012, 3:37 PM
185 0.42 118 0.10 1,110 -992 0.53 0.05 588 -471
FAA Minor Storage Volume (cubic ft.) = -6 Mod. FAA Minor Storage Volume (cubic ft.) = -6
FAA Minor Storage Volume (acre-ft.) = -0.0001 Mod. FAA Minor Storage Volume (acre-ft.) = -0.0001
UDFCD DETENTION VOLUME ESTIMATING WORKBOOK Version 2.02, Released January 2007
Little Bears Day Care
1 (Playground)
MINOR DETENTION VOLUME BY FAA & MODIFIED FAA METHOD
(See USDCM Volume I Runoff Chapter for description of method)
Determination of MINOR Detention Volume Using FAA & 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)
The user must fill in all of the blue cells for these sheets to function.
UD-Detention_v2.02.xls, Modified FAA 5/29/2012, 3:37 PM