CC - Drainage Calc Phases 1 and 2 Hensley Station Subdivision No. 1 & 2
October 22, 2020
Drainage Calculations for both phases of construction
ONAL E
cygoF OF
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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 HENSLEY STATION SUBDIVISION#2 POND 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 Subbasin
1 Subbasin 2 3 4 5 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 163,114
Acres 3.74
6 Determine the Weighted Runoff Coefficient(C) 0.85
C=](C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.85
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate
min E10 Min. Estimated Runoff Coefficients for Various Surface
- Type of Surface Runoff Coefficients"(
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 2.58 in r Business
y Downtown areas 0.70-0.95
Calculate the Post-Development peak discharge(QPeak) Qpe.k 8.21 cfs Urban neighborhoods 0.50-0.70
Residential
10 Calculate total runoff vol(V)(for sizing primary storage) V 11,000 ft Single Family 0.35-0.50 Mufti.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
Enter Percentile Storm I(95th percentile=0.60 in) 95th Industrial and Commercial
0.60 in tight areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) V,r 6,875 ft' Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) 0.83 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 0.95
Basin Forebay V 1,100 ft' concrete 0.95
Primary Treatment/Storage Basin V 6,912 ft' Brick 0.95
Subsurface Storage Roofs _ 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 11,000 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:>W. 0.13 0.1S 0.23 0.
Adapted from ASCE
D:\11M MERKLE\HENSLEY STATION DEVELOPMENT\Documents\DRAI NAG E CALC's\HENSLEY STATION POND 2-21-20 10/22/2020,11:32 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 HENSLEY STATION SUBDIVISION#2-POND 1 PRE-DEVELOPMENT DISCHARGE RATE
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) 2
4 Enter number of storage facilities(25 max)
Click to Show More Subbasins ❑
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 262,718
Acres 6.03
6 Determine the Weighted Runoff Coefficient(C) 0.20
C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avg1 0.20
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate
min ILO in. Runoff Coefficients for Various Surfact
Type of Surface Runoff Coefficients"t
8 Determine the average rainfall intensity(i)from IDF Curve based on Tc 0.69 in hr Business
y Calculate the Post-Development peak discharge(Qeeak) Downtown areas 0.70.0.95
Qp.k 0.84 cfs Urban neighborhoods 0.50-0.70
Residential
Single Family 0.35-0.50
V 1,129 ft Multi-family 0.60.0.75
10 Calculate total runoff vol(V)(for sizing primary storage)
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) 95th 0.60 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) VR 2,605 ftJ Heavy areas M90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cis 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 0.95
Basin Forebay V 113 ft' Concrete 0.95
Primary Treatment/Storage Basin V 1,016 W Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 1,129 ft' Gravel 0.75
Fields:Sandy soil Soil Type
Slope A B C D
Flat:O-2ie 0.04 0.07 0.11 0.
Average:2.6% 0.09 0.12 0.15 O.
Steep:>6S' 0.13 0.1S 0.23 O.
Adapted from ASCE
D:\JIM MERKLE\HENSLEY STATION DEVELOPMENT\Documents\DRAINAGE CALC's\HENSLEY STATION PRE-DEVELOPMENT RUNOFF 2-21-20 10/22/2020,11:32 AM
Version 10.0,May 2018
ACHD Calculation Sheet for Sizing Basins
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.
User input in yellow cells.
1 Project Name HENSLEY STATION SUBDIVISION#2 POND 1
2 Enter number of Basins(25 max) 1
3 Number of Cells(Forebay+Primary=2,Primary Only=1) 1
4 Design Storm 100 Unkto:[q,v �
5 Weighted Runoff Coefficient C 0.85 o.v TR55
6 Area A(Acres) 3.74 acres
7 Approved Discharge Rate(if applicable) 0.83 cfs
8 2-Primary Treatment/Storage V 11,000 ft3
Toggle between Forebay and Primary Basin,enter data and printfor each ---'——"
sie slye 2 S&SWF z Sid,
sr. ` Fl.r
'SYe SIgeL �
�... > <----------�---------> sib S*z �> Sik SY*ea
Primary Basin
9 Select Primary Basin Shape 5-Irregular
10 Width of Primary Basin Bottom W 73.0 ft
11 Length of Primary Basin Bottom L 61.0 it
12 Side Slopes(H:1) H:1 3.00
13 Enter Bottom Elevation 2540.38 it
14 Enter Top Bank Elevation 2544.25 ft
15 Enter Water Surface Elevation(WSE) 2543.75 ft
16 Distance Between Forebay and Primary Basin(blank if na) 0.00 ft
17 Enter Elevation Berm 2544.25 ft
18 Enter High Groundwater Elevation 2537.75 it
19 Min.Freeboard Requirement 1.00
20 Freeboard Provided
21 Infiltration Area for Primary/Storage Basin Infiltration? 6.00 in/hr Note:infiltration required if
Design Infiltration Rate,Enter 0 for no infiltration bottom s1ope<2%or 0 outflow
22 Infiltration Area for Primary Asand 341 ft'
Enter 0 for no infiltration
23 Adjusted Storage Required
iT
ration i total Q Runoff Vol Perc Vol Pre-Dev Total Max Vol
Discharge Discharge Reqd
Hr in/hr cfs ft3 ft3 ft3 ft3ft3
1.00 0.96 3.06 11,000 171 2,988 3,159 7.842
24 ept - tcrage Relationship:
Saved Surface
Basin Basin Surface Surface Area A at Volume
Saved Stage Side Slope Width at Length at Area A at Area A at Stage(ftz) Below Stage
(ft) New Stage(ft) (H:V) Stage(ft) Stage(ft) Stage(ft) Stage(ft) OVERIDE (fts)
2540.38 2540.38 3.000 73.0 61.0 Override 1324.00 0
2543.75 2543.75 3.000 0.0 0.0 Override 3678.00 9,271
3.37 ft depth for storage STORAGE OK
25 Does primary/storage basin have capacity? YES
26 Time to drain primary/storage basin 3.1 hours
90%volume in 48-hours minimum OK
D:\11M MERKLE\HENSLEY STATION DEVELOPMENT\Documents\DRAINAGE CALC's\HENSLEY STATION POND 2-21-20 10/22/2020,11:53 AM
Version 10.0,May 2018
ACHD Quick Ca)cs for Pipe and Ditch Capacity
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.
User input in yellow cells.
1 Project Name HENSLEY STATION SUBDIVISION#2 POND 1
2 Pipes
PIPE
1 Enter Flow Q= cfs -DEPTHOFFLOW
2 Manning'sn n= Table on0,VTob
3 Slope S= ft/ft
4 Pipe Diameter D= in
5 Uniform Flow Depth Y.= 0.0 in
6 Normal Velocity V= 0.00 ft/s
7 Critical Flow Depth Yc= 0.00 In
t
8 Critical Velocity V= o.00 ft/s
8 Full Flow Qr.il= 0.00 cfs
9 Full Flow% 0% "DIAMETER
MANNINGS
f FLOW CFS FT/FT SLOPE
3 Ditches
1 Flow Rate Q= cfs
2 Manning's n n=
3 Downstream Slope SL= ft/ft
4 Base Width b= ft
5 Side Slope(1-1:1) Sx H:1= —DITCF
6 Uniform Flow Depth yn= 0.00 ft I —WSE
7 Velocity V= 0.00 ft/s
FLOW 4 CFS
0.005 FT/FT SLOPE
4 Orifice/Weirs 1 0
---................... — --------
Slide On Orifice Cap, Hole High Elev.at Set Width Height
>=3.. Water Orifice Round Rectangle Rectangle
Elev. Bottom Q Area A(ftz) Dia.(in) (in) (in)
25-year
50-year
100-year 2543.75 2540.00 0.83 0.10 4.24 36.00 0.39
High
Width b Water
End V�<v
2-Sharp Crest Weir (ft) Elev.(ft) Crotch Elev.(ft) h Q lilt
0.00 0.00 �v
0.000 9 radians a
0.607 Ce
0.014 k
D:\11M MERKLE\HENSLEY STATION DEVELOPMENT\Documents\DRAINAGE CALC's\HENSLEY STATION POND 2-21-20 10/22/2020,11:34 AM
Version 10.0,May 2018
ACHD Calculation Sheet for Sand/Grease Traps
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.
Sups for Sand Grease Trap Veloaity,Ca"llatIon
User input in yellow cells.
1 Project Name HENSLEY STATION SUBDIVISION#2 POND 1
2 Enter number of Sand/Grease Traps(25 max) 1
Number of Peak Flow Baffle Throat Velocity Is the
Vault Size S/G Traps Q-cfs Spacing width Area(ft2) 0.5 fps Velocity
(inch) (inch) max. ok?
1500 G 2 8.21 20 60 16.67 0.49
Reference for Throat widths(inch)
ADS
Boise Lar-ken WQU,
Vault BMP 16
1000 G 48.0 50.5 n/a
1500 G 60.0 61.5 n/a
WQU1000 n/a n/a 60
WQU1500 n/a n/a 60
D:\JIM MERKLE\HENSLEY STATION DEVELOPMENT\Documents\DRAINAGE CALC's\HENSLEY STATION POND 2-21-20)0/22/2020, 11:01 AM
Version 10.0, May 2018
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