CC - Storm Drainage Calcs STORM DRAINAGE REPORT AND CALCULATIONS
FOR
STAPLETON SUBDIVISION NO. 2
MERIDIAN, IDAHO
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NSE4 PREPARED BY:
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16970 CORINNE M GRAHAM, PE
October 26, 2020
Csw
CIVIL SIT E
w o a is s
PO BOX 6059
BOISE, ID 83707
(208) 946-3874
cgraham@cswengineering.com
INTRODUCTION
The existing 10.45-acre site for the proposed Stapleton Subdivision No. 2 is currently vacant ground.The
proposed development includes 63 single family residential lots, 7 common lots, and associated public
roads, landscaping, and utilities.
HISTORIC DRAINAGE
The existing project site sits southwest of the intersection of W. Harris Street and S. Meridian Road in
Meridian. Historically the site drains from west to southeast.An irrigation pipe at the southwest corner
of the site conveys historical runoff from the site and from the borrow ditch along Meridian Road north
across Harris Street.
Surficial soils are comprised of lean clays, sands, and silts with sand. At depths of 3-8 feet,free draining
sand and gravels were encountered during geotechnical exploration. Groundwater was not encountered
at depths up to 12.5 feet.
Because of the presence of free draining materials and the depth to groundwater,the site is suitable for
the use of infiltration facilities.
PROPOSED DRAINAGE
The storm drainage calculations and design for the proposed improvements are intended to meet the
requirements of ACHD's storm water policy. Storm water facilities are designed to store and treat runoff
from a 100-year storm event and to pretreat the water quality volume defined as the 801h percentile
storm event. Storm water runoff from 40' behind the sidewalk, including residential driveways,will be
conveyed to the public stormwater system to be owned and maintained by ACHD. Remaining lot
drainage will be contained within individual lots.
Storm water runoff is conveyed via curb and gutter to drain inlets within the roadway then piped to four
underground seepage beds where it is treated and finally infiltrated. Storm drain manholes will be
installed to provide pre-treatment for the water quality event.
Basin#4 is designed to store the storm runoff from the Harris Street improvements and future Phase 3
improvements and is located near the bottom of the slope at the Harris Street and Meridian Road
intersection. Storm drain piping will be stubbed to Phase 3 to allow for easy tie-in and to allow for
installation of landscaping along the frontage streets.
APPENDICES
• Drainage Basin Map
• Storm Drainage Calculations
• Project Geotechnical Report
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CIVIL SITE STAPLETON SUBDIVISION NO. 2
DRAINAGE BASIN MAP
60 0 60 120
PO BOX 6059
BOISE,ID 83707 SCALE: 1' = 120'
Ph: (208)946-3874
cgraham@cswengineering.com
Prepared By:Corinne Graham, PE
CSW October 26, 2020
CIVIL SIT E
Stapleton Subdivision No. 2
Storm Drainage Calculations
ACHD Basin Characteristics
C Values
Impervious=0.90
Landscape=0.20
Basin#1 Basin#2 Basin#3 Basin#4
Total Area (SF) 101047 67854 89785 202970
Roadway Area (SF) 30393 16096 37924 45789
Sidewalk Area (SF) 9135 5624 8962 14429
House/Driveway Area (SF) 37950 25520 9660 43060
Landscape Area (SF) 23569 20614 33239 99692
C Value: 1 0.74 1 0.69 1 0.64 1 0.56
Catch Basin Calcs
CB#1A CB#16 CB#2A CB#26 CB#3A CB#36 CB#3C CB#31D CB#4A
Total Area (SF) 42777 58270 41420 26434 15077 34882 34980 4846 100654
Roadway Area (SF) 11179 19214 9738 6358 6665 14012 14919 2328 22952
Sidewalk Area (SF) 3533 5602 2533 3091 1 1558 3303 3627 474 5963
House/Driveway Area (SF) 18560 19390 15400 10120 0 8280 1380 0 0
Landscape Area (SF) 9505 14064 13749 6865 6854 9287 15054 2044 71739
C Value: 1 0.74 1 0.73 1 0.67 1 0.72 0.58 1 0.71 1 0.60 1 0.60 1 0.40
ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These
calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted.
Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#1
2 Is area drainage basin map provided? YES
(map must be included with stormwater calculations)
3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100
4 Enter number of storage facilities(25 max) 8
Click to Show More Subbasins ❑
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 30,393 9,135 37,950 23,569
Acres 2.32
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.74
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate
min
10 Min. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"I
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i Downtown areas 0.70-0.95
2.58 2.58 in hr Business
9 Calculate the Post-Development peak discharge(QPeak) Opeak 4.41 4.41 cfs Urban neighborhoods 0.50-0.70
Residential
50
10 Calculate total runoff vol V for sizing rims storage) V 5,906 5,906 ft Single Family 0.60-0.75
( )( g primary g ) Multi-family 0.60-0.75
V=Ci(Tc=60)Ax3600 Residential(rural) 0.25-0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Industrial and Commercial
Enter Percentile Storm I(95th percentile=0.60 in) 80th 0.34 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vr, 2,092 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.10-0.25
Playgrounds 0.20-0.35
Railroad yard areas 0.20-0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Asphalt 095
Basin Foreba V 591 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 5,316 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 5,906 5,906 ft' Gravel 0.75
Fields:Sandy soil Soil Type
Slope A B C D
Flat:0-2% 0.04 0.07 0.11 0.
Average:2-6% 0.09 0.12 0.15 0.
Steep:>6% 0.13 0.18 0.23 0.
Adapted from ASCE
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.5,November 2018
ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the
Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in
facilities that meet or exceed these calculations in order to be accepted.
Note this spreadsheet pulls information from the"Peak QV"tab
Steps�Beds
Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#1
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.74 Unkto: Low
QV2
5 Area A(Acres) 2.32 acres QV3
6 Approved discharge rate(if applicable) 0.00 cfs QV4
Qvs
7 Is Seepage Bed in Common Lot? Yes V 5,906 5,066 ft' 0%Sediment
840 CIF(1st hour of drainage)
8 Set Total Design Width of All Drain Rock W 15.0 ft
9 Set Total Design Depth of All Drain Rock D 10.0 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
10 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"drain rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr
12 Size of WQ Perf Pipe(Perf 180°) Dia pipe 18 in
13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in
14 Calculate Total Storage per Foot Spf 70.2 ft3/ft
15 Calculate Design Length L 84 84 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 84 ft
17 Variable Infiltration Window W SWW 15.0 ft
18 Time to Drain 5.4 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 84 84 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxJ(2xgxH)
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These
calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted.
Iculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#2
2 Is area drainage basin map provided? YES
(map must be included with stormwater calculations)
3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100
Click to Show More Subbasins ❑
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 16,096 5,624 25,520 20,614
Acres 1.56
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.69
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate
min 10 Min. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"I
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 2.58 in hr Business
Downtown areas 0.70-0.95
9 Calculate the Post-Development peak discharge(QPeak) Qpeak 2.76 2.76 cfs Urban neighborhoods 0.50-0.70
Residential
Single Family 0.35-0.50
10 Calculate total runoff vol(V)(for sizing primary storage) V 3,700 3,700 ft Multi-family 0.60-0.75
V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Industrial and Commercial
Enter Percentile Storm I(95th percentile=0.60 in) 80th 0.34 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vr, 1,311 ft' Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,Cemeteries 0.10-0.25
Playgrounds 0.20-0.35
Railroad yard areas 0.20-0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Foreba V 370 ft` Asphalt 0.95
Y Concrete 0.95
Primary Treatment/StorageBasin V 3,330 fts Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,700 3,700 ft' Gravel 0.75
Fields:Sandy soil Soil Type
Slope A B C D
Flat:0-2% 0.04 0.07 0.11 0.
Average:2-6% 0.09 0.12 0.15 0.
Steep:>6% 0.13 0.18 0.23 0.
Adapted from ASCE
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.5,November 2018
ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the
Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in
facilities that meet or exceed these calculations in order to be accepted.
Note this spreadsheet pulls information from the"Peak QV"tab
Steps�Beds
Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#2
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.69 Unkto: Low
Qv2
5 Area A(Acres) 1.56 acres QV3
6 Approved discharge rate(if applicable) 0.00 cfs QV4
Qv5
7 Is Seepage Bed in Common Lot? Yes V 3,700 3,174 ft' 0%Sediment
527 CF(1st hour of drainage)
8 Set Total Design Width of All Drain Rock W 10.0 ft
9 Set Total Design Depth of All Drain Rock D 10.0 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
10 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"drain rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr
12 Size of WQ Perf Pipe(Perf 180°) Dia pipe 18 in
13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in
14 Calculate Total Storage per Foot Spf 46.8 ft3/ft
15 Calculate Design Length L 79 79 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 79 ft
17 Variable Infiltration Window W SWW 10.0 ft
18 Time to Drain 5.4 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 79 79 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxJ(2xgxH)
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These
calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted.
Iculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#3
2 Is area drainage basin map provided? YES
(map must be included with stormwater calculations)
3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100
Click to Show More Subbasins ❑
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 37,924 8,962 9,660 33,239
Acres 2.06
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.64
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate
min 10 Min. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"I
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 2.58 in hr Business
Downtown areas 0.70-0.95
9 Calculate the Post-Development peak discharge(QPeak) Qpeak 3.41 3.41 cfs Urban neighborhoods 0.50-0.70
Residential
Single Family 0.35-0.50
10 Calculate total runoff vol(V)(for sizing primary storage) V 4,565 4,565 ft Multi-family 0.60-0.75
V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Industrial and Commercial
Enter Percentile Storm I(95th percentile=0.60 in) 80th 0.34 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 1,617 ft' Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,Cemeteries 0.10-0.25
Playgrounds 0.20-0.35
Railroad yard areas 0.20-0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Foreba V 457 ft' Asphalt 0.95
Y Concrete 0.95
Primary Treatment/StorageBasin V 4,109 fts Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 4,565 4,565 ft' Gravel 0.75
Fields:Sandy soil Soil Type
Slope A B C D
Flat:0-2% 0.04 0.07 0.11 0.
Average:2-6% 0.09 0.12 0.15 0.
Steep:>6% 0.13 0.18 0.23 0.
Adapted from ASCE
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.5,November 2018
ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the
Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in
facilities that meet or exceed these calculations in order to be accepted.
Note this spreadsheet pulls information from the"Peak QV"tab
Steps�Beds
Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#3
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.64 Unkto: Low
QV2
5 Area A(Acres) 2.06 acres QV3
6 Approved discharge rate(if applicable) 0.00 cfs QV4
Qvs
7 Is Seepage Bed in Common Lot? Yes V 4,565 3,909 ft, 0%Sediment
656 CIF(1st hour of drainage)
8 Set Total Design Width of All Drain Rock W 12.0 ft
9 Set Total Design Depth of All Drain Rock D 10.0 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
10 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"drain rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr
12 Size of WQ Perf Pipe(Perf 180°) Dia pipe 18 in
13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in
14 Calculate Total Storage per Foot Spf 56.2 ft3/ft
15 Calculate Design Length L 81 82 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 82 ft
17 Variable Infiltration Window W SWW 12.0 ft
18 Time to Drain 5.4 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 82 82 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxJ(2xgxH)
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These
calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted.
Iculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#5
2 Is area drainage basin map provided? YES
(map must be included with stormwater calculations)
3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100
Click to Show More Subbasins ❑
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 45,789 14,429 43,060 99,692
Acres 4.66
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.56
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 User Calculate
min 10 Min. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"I
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 2.58 in hr Business
Downtown areas 0.70-0.95
9 Calculate the Post-Development peak discharge(QPeak) Qpeak 6.69 6.69 cfs Urban neighborhoods 0.50-0.70
Residential
Single Family 0.35-0.50
10 Calculate total runoff vol(V)(for sizing primary storage) V 8,956 8,956 ft Multi-family 0.60-0.75
V=CI(Tc=60)Ax3600 Residential(rural) 0.25-0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Industrial and Commercial
Enter Percentile Storm I(95th percentile=0.60 in) 80th 0.34 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vr, 3,172 ft' Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,Cemeteries 0.10-0.25
Playgrounds 0.20-0.35
Railroad yard areas 0.20-0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Foreba V 896 ft' Asphalt 0.95
Y Concrete 0.95
Primary Treatment/StorageBasin V 8,061 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 8,956 8,956 ft' Gravel 0.75
Fields:Sandy soil Soil Type
Slope A B C D
Flat:0-2% 0.04 0.07 0." O.
Average:2-6% 0.09 0.12 0.15 O.
Steep:>6% 0.13 0.18 0.23 O.
Adapted from ASCE
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.5,November 2018
ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers
NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the
Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in
facilities that meet or exceed these calculations in order to be accepted.
Note this spreadsheet pulls information from the"Peak QV"tab
Steps�Beds
Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name ACHD Basin#5
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.56 Unkto: Low
Qv2
5 Area A(Acres) 4.66 acres QV3
6 Approved discharge rate(if applicable) 0.00 cfs Qv4
Qvs
7 Is Seepage Bed in Common Lot? Yes V 8,956 7,676 ft' 0%Sediment
1280 CF(1st hour of drainage)
8 Set Total Design Width of All Drain Rock W 20.0 ft
9 Set Total Design Depth of All Drain Rock D 10.0 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
10 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"drain rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr
12 Size of WQ Perf Pipe(Perf 180°) Dia pipe 18 in
13 Size of Overflow Perf Pipe(Perfs 3600),READ if Q100>3.3 cfs in
14 Calculate Total Storage per Foot Spf 93.5 ft3/ft
15 Calculate Design Length L 96 96 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 96 ft
17 Variable Infiltration Window W SWW 20.0 ft
18 Time to Drain 5.4 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 96 96 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxJ(2xgxH)
C:\Users\cgrah\Dropbox\Projects\19043 Stapleton Subdivision Ph2\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2020,6:29 PM
Version 10.0,May 2018