HomeMy WebLinkAboutStorm Drain Calcs V1STORM DRAINAGE REPORT AND CALCULATIONS
FOR
SKYBREAK SUBDIVISION NO. 1
/GENF��
16970
ksT11-12-21
OF
MERIDIAN, IDAHO
PREPARED BY:
CORINNE M GRAHAM, PE
October 26, 2021
Csw
C 1N/I L S ITE
w 0 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 80t" 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
�---
- - BASIN #3P
ACHD BASIN 1#1
� I
1
-- BASIN-
T� I
1 I �
BASIN #BP - - - -�
BASIN #5P
-TTTT
BASIN #4P BASIN #7P
SKYBREAK SUBDIVISION NO. 1
DRAINAGE BASIN MAP
N
T
100 0 100 200
SCALE: 1' - 200'
CSW
C I V I L S I T E
Prepared By: Corinne Graham, PE
October 26, 2021
Skybreak Subdivision No. 1
Storm Drainage Calculations
Drainaee Basin Characteristics
C Values
Impervious = 0.90
Landscape = 0.20
ACH D
Basin #1
Basin #2P
Basin #3P
Basin #4P
Basin #5P
Basin #6P
Basin #7P
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 #113
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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
2.81
2.58 in hr
2.81 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
3,761
3,761 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
Both
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
V„
1,332
1,332 fY
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
376
ft'
Primary Treatment/StorageBasin
V
3,385
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
3,761
3,761 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
35,396
7,982
41,809
1.96
0.90
0.90
0.20
0.56
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.30-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.56
1.96 acres
0.00 cfs
V 3,761
Link to: LQV
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD 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
6.3 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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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 Is area drainage basin map provided?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
2.29
2.58 in hr
2.29 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
3,061
3,061 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
Vrr
1,084
1,084 fY
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
306
ft'
Primary Treatment/StorageBasin
V
2,755
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
3,061
3,061 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
30,097
4,390
37,746
1.66
0.90
0.90
0.20
0.53
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.30-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.53
1.66 acres
0.00 cfs
V 3,061
Link to: LQV
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
46.8
46.8 ft'/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
10.0 ft
18 Time to Drain
6.4 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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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 Is area drainage basin map provided?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
4.66
2.58 in hr
4.66 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
6,236
6,236 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
Vrr
2,208
2,208 ft,
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
624
ft'
Primary Treatment/StorageBasin
V
5,612
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
6,236
6,236 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
32,430
5,197
36,737
58,342
3.05
0.90
0.90
0.90
0.20
0.59
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.10-0.25
Playgrounds
0.20-0.31
Railroad yard areas
0.20210
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.59
3.05 acres
0.00 cfs
V 6,236
Link to: LQV
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
93.5
93.5 ft'/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
6.3 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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
4.73
2.58 in hr
4.73 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
6,331
6,331 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
V„
2,242
2,242 ft
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
633
ft'
Primary Treatment/StorageBasin
V
5,698
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
6,331
6,331 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
37,226
5,780
34,409
50,629
2.94
0.90
0.90
0.90
0.20
0.62
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.10-0.25
Playgrounds
0.20-0.31
Railroad yard areas
0.20210
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.62
2.94 acres
0.00 cfs
V 6,331
Link to: LQV
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
51.5
51.5 ft'/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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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 Is area drainage basin map provided?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
2.80
2.58 in hr
2.80 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
3,757
3,757 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
Vrr
1,331
1,331 ft,
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
376
ft'
Primary Treatment/StorageBasin
V
3,381
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
3,757
3,757 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
23,903
3,989
18,406
28,427
1.72
0.90
0.90
0.90
0.20
0.63
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.10-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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 #5P
2 Enter number of Seepage Beds (25 max)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.63
1.72 acres
0.00 cfs
V 3,757
Link to: L0,v
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
37.5
37.5 ft'/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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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 Is area drainage basin map provided?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
2.59
2.58 in hr
2.59 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
3,469
3,469 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
V„
1,228
1,228 ft,
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
347
ft'
Primary Treatment/StorageBasin
V
3,122
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
3,469
3,469 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
21,282
1,891
18,562
30,788
1.66
0.90
0.90
0.90
0.20
0.60
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.10-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.60
1.66 acres
0.00 cfs
V 3,469
Link to: L0,v
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
37.5
37.5 ft'/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
6.4 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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 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.
Steps for Peak Discharge Rate using the Rational Method calculated for post-developm ■
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?
(map must be included with stormwater calculations)
3 Enter Design Storm (100-Year or 25-Year With 100-Year Flood Route)
4 Enter number of storage facilities (25 max)
5 Area of Drainage Subbasin (SF or Acres) SF
Acre
6 Determine the Weighted Runoff Coefficient (C)
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg
7 Calculate Overland Flow Time of Concentration in Minutes (Tc) or use default 10 User Calculate
min
0 Min.
8 Determine the average rainfall intensity (i) from IDF Curve based on Tc
9 Calculate the Post -Development peak discharge (QPeak)
i
QPeak
2.58
2.92
2.58 in hr
2.92 cfs
10 Calculate total runoff vol (V) (for sizing primary storage)
V
3,917
3,917 ft
V = Ci (Tc=60)Ax3600
11 Calculate Volume of Runoff Reduction Vrr
Enter Percentile Storm I (95th percentile = 0.60 in)
80th
0.34 in
Enter Runoff Reduction Vol (95th Percentile=0.60-in x Area x C)
V„
1,387
1,387 ft,
12 Detention: Approved Discharge Rate to Surface Waters (if applicable)
0.00 cfs
13 Volume Summary
Surface Storage: Basin
Basin Forebay
V
392
ft'
Primary Treatment/StorageBasin
V
3,526
ft'
Subsurface Storage
Volume Without Sediment Factor (See BMP 20 Tab)
V
3,917
3,917 ft'
YES
rlir4 to Sh- 10-1-hh.6- I-1
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
Subbasin
1
Subbasin 2
3
4
5
Subbasin 6
7
8
9
10
22,052
4,781
19,101
40,165
1.98
0.90
0.90
0.90
0.20
0.57
Estimated Runoff Coefficients for Various Surfac
Type of Surface
Runoff Coefficients "I
Business
Downtown areas
0.70-0.95
Urban neighborhoods
0.50-0.70
Residential
Single Family
0.35-0.50
Multi -family
0.60-0.75
Residential (rural)
0.25-0.40
Apartment Dwelling Areas
0.70
Industrial and Commercial
Light areas
0.80
Heavy areas
0.90
Parks, Cemeteries
0.10-0.25
Playgrounds
0.20-0.35
Railroad yard areas
0.20-0.40
Unimproved areas
0.10-0.30
Streets
Asphalt
0.95
Concrete
0.95
Brick
0.95
Roofs
0.95
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
Version 10.5, November 2018
10/26/2021, 10:54 AM
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)
3 Design Storm
4 Weighted Runoff Coefficient C
5 Area A (Acres)
6 Approved discharge rate (if applicable)
7 Is Seepage Bed in Common Lot? Yes
100
0.57
1.98 acres
0.00 cfs
V 3,917
Link to: L0,v
QV TR55
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 180°)
Dia pipe
18 in
13 Size of Overflow Perf Pipe (Perfs 360°), REQD if Q100>3.3 cfs
in
14 Calculate Total Storage per Foot
Spf
30.5
30.5 ft'/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
6.4 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 9r
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
6 Chamber Storage Volume, With Rock, Per Manuf
74.90 ft3
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 Drain age\ACH D_SD_CALCS_1 12018 10/26/2021, 10:54 AM
Version 10.0, May 2018