CC - Storm Drain Calcs STORM DRAINAGE REPORT AND CALCULATIONS
FOR
SKYBREAK SUBDIVISION NO. 1
MERIDIAN, IDAHO
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NSE� % PREPARED BY:
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16970 CORINNE M GRAHAM, PE
C,os�g �P,o�P�. October 26, 2021
OF1
��tiNE M.GAP
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C 1N/I L S ITE
W O R K S
PO BOX 6059
BOISE, ID 83707
(208) 946-3874
cgraham@cswengineering.com
INTRODUCTION
The existing 30.76-acre site for the proposed Skybreak Subdivision No. 1 is currently agricultural row
crop ground.The proposed development includes 54 single family residential lots, 18 landscape
common lots, and associated public and private streets, landscaping, and utilities.
HISTORIC DRAINAGE
The existing project site sits southeast of the intersection of E. Lake Hazel Road and S. Eagle Road in
Meridian.The eastern portion of the site that will be developed in Phase 1 lies along Meridian's
southern rim.
Surficial soils are comprised of sandy silts and silty sands.At depths of 3-6 feet, free draining poorly
graded gravel with sand was encountered during geotechnical exploration. Groundwater was not
encountered at depths up to 15.2 feet and is not anticipated to reach levels higher than 20 feet below
existing ground.
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.
Stormwater runoff from the public entry street is conveyed via curb and gutter to drain inlets within the
roadway then piped to an underground seepage bed where it is treated, stored, and finally infiltrated.A
sand and grease trap will be installed to provide pre-treatment for the water quality event.
Storm water runoff from the private streets and an area 40 feet behind the sidewalk within the
residential lots, including driveways,will be conveyed to the public stormwater system to be owned and
maintained by the subdivision HOA. Remaining lot drainage will be contained within individual lots.
Storm water runoff is conveyed via curb and gutter to drain inlets within the private roadway then
piped to six underground seepage beds where it is treated, stored, and finally infiltrated. Sand and
grease traps will be installed to provide pre-treatment for the water quality event.
APPENDICES
• Drainage Basin Map
• Storm Drainage Calculations
• Project Geotechnical Report
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O R K 6 SKYBREAK SUBDIVISION NO. 1
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PO BOX6059 DRAINAGE BASIN MAP
BOISE,ID 83707 SCALE: 1� = 200'
Ph: (208)946-3874
cgra ham@cswengineering.com
Prepared By: Corinne Graham, PE
CSw October 26, 2021
CIVIL S I T E
Skybreak Subdivision No. 1
Storm Drainage Calculations
Drainage Basin Characteristics
C Values
Impervious =0.90
Landscape =0.20
ACHD
Basin#1 Basin#211) Basin#311) Basin#411) Basin#511) Basin#611) Basin#711)
Total Area (SF) 85187 72233 132706 128044 74725 72523 86099
Roadway Area (SF) 35396 30097 32430 37226 23903 21282 22052
Sidewalk Area (SF) 7982 4390 5197 5780 3989 1891 4781
House/Driveway Area (SF) 0 0 36737 34409 18406 18562 19101
Landscape Area (SF) 41809 37746 58342 50629 28427 30788 40165
C Value: 0.56 0.53 0.59 0.62 0.63 0.60 0.57
Catch Basin Calculations
CB#1A CB#1113
Total Area (SF) 42370 42817
Roadway Area (SF) 17670 17726
Sidewalk Area (SF) 3968 4014
House/Driveway Area (SF) 0 0
Landscape Area (SF) 20732 21077
C Value: 0.56 0.56
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)
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 35,396 7,982 41,809
Acres 1.96
6 Determine the Weighted Runoff Coefficient(C) 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(OPeak) OPeA 2.81 2.81 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 3,761 3,761 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, 1,332 1,332 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.
Playgrounds 0.20-0.0-0.35
5
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 376 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 3,385 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,761 3,761 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 0.56 Link to: QV —
QV TR55
5 Area A(Acres) 1.96 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 3,761 3,761 ft' 0%Sediment
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(Pert 1800) 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 67 67 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 67 67.0 ft
17 Variable Infiltration Window W SWW 12.0 12.0 ft
18 Time to Drain 67 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 67 67 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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.
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 Basin#21P
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)
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 30,097 4,390 37,746
Acres 1.66
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.53
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(OPeak) OPeA 2.29 2.29 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 3,061 3,061 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 1,084 1,084 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.
Playgrounds 0.20-0.0-0.35
5
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 306 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 2,755 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,061 3,061 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#2P
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.53 Link to: QV —
QV TR55
5 Area A(Acres) 1.66 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 3,061 3,061 ft' 0%Sediment
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(Pert 1800) 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 46.8 ft3/ft
15 Calculate Design Length L 65 65 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 65 65.0 ft
17 Variable Infiltration Window W SWW 10.0 107 ft
18 Time to Drain 6-T hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 65 65 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers W
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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.
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 Basin#31P
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)
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 32,430 5,197 36,737 58,342
Acres 3.05
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.59
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 2.58 2.58 in hr Business
Downtown areas 0.70-0.95
9 Calculate the Post-Development peak discharge(ClPeak) peak 4.66 4.66 cfs Urban neighborhoods 0.50-0.70
Residential
50
10 Calculate total runoff vol V for sizing rims storage) V 6,236 6,236 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, 2,208 2,208 fY 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 624 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 5,612 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 6,236 6,236 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#3P
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.59 Link to: QV —
QV TR55
5 Area A(Acres) 3.05 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 6,236 6,236 ft' 0%Sediment
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(Pert 1800) 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 93.5 ft3/ft
15 Calculate Design Length L 67 67 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 67 67.0 ft
17 Variable Infiltration Window W SWW 20.0 20.0 ft
18 Time to Drain 67 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 67 67 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers W
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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.
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 Basin#4P
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)
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 37,226 5,780 34,409 50,629
Acres 2.94
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.62
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(OPeak) OPeA 4.73 4.73 cfs Urban neighborhoods 0.50-0.70
Residential
50
10 Calculate total runoff vol V for sizing rims storage) V 6,331 6,331 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, 2,242 7242 fY 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 633 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 5,698 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 6,331 6,331 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#4P
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.62 Link to: QV —
QV TR55
5 Area A(Acres) 2.94 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 6,331 6,331 ft' 0%Sediment
8 Set Total Design Width of All Drain Rock W 11.0 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(Pert 1800) 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 51.5 51.5 ft3/ft
15 Calculate Design Length L 123 123 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 123 123.0 ft
17 Variable Infiltration Window W SWW 11.0 11.0 ft
18 Time to Drain 6.3 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 123 123 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers W
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:55 AM
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.
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 Basin#5P
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)
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 23,903 3,989 18,406 28,427
Acres 1.72
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.63
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(OPeak) OPeA 2.80 2.80 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 3,757 3,757 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, 1,331 1,331 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.
Playgrounds 0.20-0.0-0.35
5
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 376 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 3,381 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,757 3,757 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#SP
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.63 Link to: QV —
QV TR55
5 Area A(Acres) 1.72 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 3,757 3,757 ft' 0%Sediment
8 Set Total Design Width of All Drain Rock W 8.0 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(Pert 1800) 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 37.5 37.5 ft3/ft
15 Calculate Design Length L 100 100 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 100 100.0 ft
17 Variable Infiltration Window W SWW 8.0 8.0 ft
18 Time to Drain 6.3 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 100 100 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers W
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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.
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 Basin#61P
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)
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 21,282 1,891 18,562 30,788
Acres 1.66
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.60
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(OPeak) OPeA 2.59 2.59 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 3,469 3,469 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, 1,228 1,228 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.
Playgrounds 0.20-0.0-0.35
5
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 347 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 3,122 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,469 3,469 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#6P
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.60 Link to: QV —
QV TR55
5 Area A(Acres) 1.66 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 3,469 3,469 ft' 0%Sediment
8 Set Total Design Width of All Drain Rock W 8.0 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(Pert 1800) 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 37.5 37.5 ft3/ft
15 Calculate Design Length L 92 92 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 92 92.0 ft
17 Variable Infiltration Window W SWW 8.0 8.0 ft
18 Time to Drain 6-T hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 92 92 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers W
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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.
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 Basin#7P
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)
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 22,052 4,781 19,101 40,165
Acres 1.98
6 Determine the Weighted Runoff Coefficient(C) 0.90 0.90 0.90 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg 0.57
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(OPeak) OPeA 2.92 2.92 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 3,917 3,917 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, 1,387 1,387 W Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.00 cfs Parks,cemeteries 0.20-0.25
Playgrounds 0. 0-0.35
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 392 ft' .
Y Concrete 0.95
Primary Treatment/StorageBasin V 3,526 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 3,917 3,917 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\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
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
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 Basin#7P
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.57 Link to: QV —
QV TR55
5 Area A(Acres) 1.98 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 3,917 3,917 ft' 0%Sediment
8 Set Total Design Width of All Drain Rock W 6.5 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(Pert 1800) 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 30.5 30.5 ft3/ft
15 Calculate Design Length L 128 128 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 128 128.0 ft
17 Variable Infiltration Window W SWW 6.5 6.7 ft
18 Time to Drain 6-T hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 128 128 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optional Storage Chambers
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 0 ft3
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
C:\Users\cgrah\Dropbox\Projects\19044 Skybreak Subdivision\Reports\Storm Drainage\ACHD_SD_CALCS_112018 10/26/2021,10:54 AM
Version 10.0,May 2018