2017_10_26 Reafield 2nd Submittal Calcs

STORM DRAINAGE, EROSION CONTROL
& WATER QUALITY CALCULATIONS

FOR
REAFIELD
Union County, North Carolina

George Macon
2400 South Blvd., Suite 300
Charlotte, NC 28203

Date: June 20, 2017
Revised: October 26, 2017

Project No: 16-115

Calculations By: udp

PRELIMINARY
CALCS & MAPS

STORM DRAINAGE PIPE
CALCULATIONS

ReafieldUrban Design PartnersJOB NO.:16-115BY:udp1318-E6 Central AvenueDATE:05.16.17P.M.:lbtCharlotte, NC 28205REVISED:10.26.17 STORM DRAINAGE DESIGN DATALOCATIONDRAINRUNOFFINVERT ELEV.AREAROUNDED ACTUAL (FROM) (FROM) PIPEFROM TO C I Q inlet Q pipe n SLOPE LENGTH SIZE CAPACITY VEL. INV INV RIM COVER MATERIAL(acres) (cfs) (cfs) (%) (ft) (inches) (cfs) (fps) OUT IN ELEVATION DEPTHCB-21 FES-20 1.10 0.95 7.52 7.8 7.8 0.012 0.73% 34189.77 6.42 585.25 585.00 590.10 3.35 HDPEYI-17JB-90.12 0.75 7.52 0.7 0.7 0.012 2.77% 58103.96 4.94 588.00 586.40 591.50 2.67 HDPEYI-16 YI-15 0.04 0.95 7.52 0.3 0.3 0.012 1.51% 33102.93 2.47 589.00 588.50 591.35 1.52 HDPEYI-15CO-120.01 0.95 7.52 0.1 0.4 0.012 1.57% 16102.98 3.28 588.50 588.25 591.20 1.87 HDPEYI-14 YI-13 0.13 0.75 7.52 0.7 0.7 0.012 1.12% 67102.52 3.74 589.00 588.25 591.85 2.02 HDPEYI-13 CO-12 0.10 0.75 7.52 0.6 1.3 0.012 1.21% 41102.62 4.42 588.25 587.75 591.50 2.42 HDPECO-12YI-11 0.00 0.60 7.52 0.0 1.7 0.012 0.61% 57101.86 4.03 587.75 587.40 592.25 3.67 HDPEYI-11 YI-10 0.15 0.75 7.52 0.9 2.5 0.012 0.65% 77123.12 4.61 587.40 586.90 590.50 2.10 HDPEYI-10 JB-9 0.14 0.75 7.52 0.8 3.3 0.012 0.78% 64123.41 5.25 586.90 586.40 590.50 2.60 HDPEJB-9JB-8 0.00 0.60 7.52 0.0 4.0 0.012 0.58% 103155.35 4.89 586.40 585.80 594.75 7.10 HDPEJB-8 CB-7 0.00 0.60 7.52 0.0 4.0 0.012 0.63% 103155.57 5.09 585.80 585.15 591.00 3.95 HDPECB-7 FES-6 0.20 0.95 7.52 1.4 5.4 0.012 0.91% 16156.71 6.23 585.15 585.00 588.83 2.43 HDPECB-5 CB-4 1.05 0.95 7.52 7.5 7.5 0.012 0.58% 17188.68 5.79 585.22 585.12 587.85 1.13 HDPECB-4 FES-3 0.68 0.95 7.52 4.8 12.3 0.012 0.54% 222418.12 6.29 585.12 585.00 587.85 0.73 HDPEOS-2 FES-1 - - - - 13.0 0.013 0.75% 67189.10 6.28 584.50 584.00 587.00 0.71 III RCPPIPEPIPE DEPTHSTORM DRAINAGE DESIGN DATA
EROSION CONTROL
CALCULATIONS

Reafield Urban Design Partners
JOB NO.:16-115 BY:udp 1318-E6 Central Avenue
DATE:05.16.17 P.M.:lbt Charlotte, NC 28205
REVISED:10.26.17
SKIMMER BASIN
DRAINAGE AREAS/REQ'D STORAGE DESIGN CRITERIA
Total drainage area (TDA)4.29 ac Proposed sediment depth 2 ft
Disturbed area(DA)4.29 ac Bottom elevation of basin 585 msl
Required sediment storage(1800xTDA) 7,722 cf Side slopes (H:V)3 :1
Required surface area:4,550 sf Depth of flow over spillway 1 ft
BASIN CONFIGURATION PLANNED BASIN SIZE
Bottom elevation 585 msl (REFER TO EROSION CONTROL PLAN)
Sediment Storage elevation 587 msl Elev.Area (SF)Cumulative Volume (CF)
Top of Berm 589 msl 585 10,050 0
586 12,484 11,267
BASIN EFFICIENCY 587 14,973 24,996
Sediment storage required: 7,722 cf 588 17,518 41,241
Sediment storage provided:24,996 OKAY 589 20,122 60,061
Surface area required: 4,550 sq ft
Surface area provided:14,973 OKAY
PRIMARY SPILLWAY DESIGN (2-YEAR STORM)
PRIMARY SPILLWAY DESIGN
Bare soil coefficient 'C' = 0.45 Spillway design: (L=Q/(C*h^1.5)); C=3.0, h= 1
Area 'A' =4.29 ac
2 yr. storm rainfall intensity, 'I' = 5.03 in/hr
2 yr Design flow, 'Q' = 10 cfs
10 yr storm rainfall intensity, 'I' = 7.03 in/hr Spillway length @ flow depth 10 ft
Design flow from site, 'Q' =14 cfs
Skimmer Basin Design
DESIGN FLOW (Q=CIA)
RIPRAP
CALCULATIONS
(STORM DRAINAGE OUTLET PIPES)

Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
FES-1:
Q = 13.0 cfs
d0 = 18"
3d0 = 4.5'
La = 12'
w = 13.5'
v = 6.3 fps
d50 = 0.6'
Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
FES-3:
Q = 12.3 cfs
d0 = 24"
3d0 = 6'
La = 13'
w = 15'
v = 6.3 fps
d50 = 0.60'
Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
FES-6:
Q = 5.4 cfs
d0 = 15"
3d0 = 3.75'
La = 10'
w = 11.25'
v = 6.2 fps
d50 =0.50'
Figure 8.06a: Design of outlet protection from a round pipe flowing full, minimum
tailwater condition (Tw<0.5 diameter)
FES-20:
Q = 7.8 cfs
d0 = 18"
3d0 = 4.5'
La = 10'
w = 11.50'
v = 6.4 fps
d50 =0.60'

BMP CALCULATIONS

ReafieldUrban Design PartnersJOB NO.:16-115BY:udp1318-E6 Central AvenueDATE:05.15.17P.M.:lbtCharlotte, NC 28205REVISED:10.26.17 PRELIMINARY CALCULATIONSINTRODUCTION:SUMMARYDRAINAGE AREAS: Predeveloped Drainage Area4.29acresPostdeveloped Drainage Area4.29acresSOIL TYPES:(see attached soils map)Area (ac)Area (%)Soil TypeHydrologic Soil Group4.29100%CTotal4.29100%CCURVE NUMBER:Predeveloped CN50/50 ConditionCover TypeArea (ac)%CNWtd. CNWoods2.1450%7035Grass2.1450%7437Total4.29 72Composite CNUse CN =72Postdeveloped CNCover TypeArea (ac)%CNWtd. CNImpervious 3.1173%9871Grass1.1727%7420Total4.29 91Composite CNUse CN =91HYDROLOGIC CALCULATIONSPost-developedDrainage area (DA)4.29ac.4.29acCuve Number (CN)7291Time of Concentration0.25hr.0.08hr.Impervious Percentage0%73%Pre-developedThe site currently consists of open space and some wooded areas, mostly along McBride Branch. The site falls within the Goose Creek watershed and must meet rules set for water quality treatment in 15A NCAC 02B.0600. The proposed development includes 3 retail/commercial buildings and associated parking. Impervious area for a future building and parking lot have been included in the calculations. All on-site drainage will be captured by a storm drainage system and will be detained and treated by a sand filter dry detention basin.
ReafieldJOB NO.:16-115BY:udpDATE:05.15.17P.M.:lbtREVISED:10.26.17 Sand Filter Design RequirementsDesign MethodDesign MethodTSSDetention Time2.0daysFilter Bed Depth2.5ftUnderdrain System Thickness1.0ftHydrologic CalculationsPost-developedDrainage area to pond (Da)= 4.29ac.4.29acCuve Number (CN)7291Time of Concentration0.25hr.0.08hr.Impervious Percentage0%73%Water Quality Volume (Post-Pre 1-yr 24-hr)Volume must be released over a period of 2-5 days1-year 24-hour volume: Pre-developed =11,968cfPost-Developed = 32,702cfWQv = Post-Pre0.446ac-ftWQv = 31,458-12,02419,434cf0.335ac-ft14,576cfChannel Protection VolumeQ=(P-0.2S)^2/(P+0.8S)Q=accumulated runoff volume, inchesP=accumulated rainfall (potential maximum runoff), inches2.93inS=potential maximum soil retention, inches = 1000/CN-10 =0.99inCN=SCS curve number91Q=2.01cfsComputer Watershed RunoffCPv=0.72ac-ft31,233cfSAND FILTER DESIGNCharlotte, NC 282051318-E6 Central AvenueUrban Design Partners75% WQv =Pre-developedWQv=
ReafieldJOB NO.:16-115BY:udpDATE:05.15.17P.M.:lbtREVISED:10.26.17 SAND FILTER DESIGNCharlotte, NC 282051318-E6 Central AvenueUrban Design PartnersCalculate Release RatesWater Quality Release Rate2.00days48hoursRelease=0.106cfsChannel Protection Volume Release Rate (1yr, 24 hr storm)hold volume 24 hrs past center of storm (12 hr)36hoursRelease=0.241cfsDetermine Orifice Size for drawdownQ= CA x sqrt(2gh) orifice equationaA= Area of orificea sqftt= Time to drawdown 129,600 sec 36 hoursg= Gravity constant 32.2 ft/s^2h= Change in head 1.00 ftC= Orifice constant 0.6Maximum orifice area = 0.0501 sq ftMaximum orifice size =3.03in.Calculate Pretreatment System Requirementssedimentation chamber (forebay) must hold 20% of the WQvVolume=2,915cf(required)Chamber Approximate DimensionsDepth=3ftLength=190ftWidth=30ftArea=6,206sf(surface area at top)Volume=4,551cf(provided)15% of main pond volumeDetermine Suface Area to Treat WQvSurface Area based on Darcy's EquationAf=(WQv)(df)/{(k)(h+d)(t)}Af=surface area of ponding area (sq ft)WQv=water quality control volume14,576cfd=filter bed depth2.5ftk=coefficient of permeability of filter media3.5ft/dayh=average height of water above filter bed (ft)1ft24" max for WQ storm eventt=design filter bed drain time (days)2.50dayAf=1,586sf(required)Determine DimensionsLength=64ftWidth=25ftArea=1,600sf(provided)
ReafieldJOB NO.:16-115BY:udpDATE:05.15.17P.M.:lbtREVISED:10.26.17 SAND FILTER DESIGNCharlotte, NC 282051318-E6 Central AvenueUrban Design PartnersStage/Storage TableElevation Forebay Pond Total Total Forebay Pond Cumulative Vol Cumulative Vol(msl) Area (sf) Area (sf) Area (sf) Area (ac) Vol (cu-ft) Vol (cu-ft) (cu-ft) (ac-ft)584.5 0 1,600 1,6000.037 0 0 0 0.000585 4,034 6,017 10,0510.231 0 1,785 1,785 0.041586 5,097 7,387 12,4840.287 4,551 8,468 14,804 0.340587 6,206 8,767 14,9730.344 10,187 16,528 41,519 0.953588 17,518 17,5180.402 29,407 70,926 1.628589 20,122 20,1220.462 48,193 119,119 2.735Stage/Discharge TableQ=Af(k)(h+d)/(d)Af=surface area of ponding area (sq ft)1,600 sfd=filter bed depth2.5 ftk=coefficient of permeability of filter media3.5 ft/dayh=average height of water above filter bed (ft)Elevation Height Fow FlowForebay Weir(msl) (ft) (cf/day) (cfs)Elevation = 587.0584.5 00 0.000Q= 3.33lh^3/2585.5 1.07,840 0.091Q=2 yr. storm runoff15.13cfs586.5 2.010,080 0.117l=weir lengthlft587.5 3.012,320 0.143h=elevation over weir0.50ft588.5 4.014,560 0.169l=Q/(3.33 x l^3/2)589.0 4.515,680 0.181Weir Length13Water Quality Surface Elevation (Interpolation)WQv Drawdown Time (Interpolation)ElevTime (hr) Storage Volume (cf)586.1148ElevElev586.0251Temp. Storage Elev: 1.53 ft. above perm. pool elev.51 hoursTemp. Pool Elev:586.032.125 daysPeak Flow Attenuation (See Hydrocad Model)Water SurfacePrePostRoutedElev1-year3.8914.710.13yes586.852-year6.0518.590.56yes587.0410-year12.7529.0111.67yes587.3725-year17.1635.2512.95yes587.7250-year20.8240.2613.82yes588.03100-year24.6545.3714.60yes588.32Storage Volume (cf)Storm EventPeak Flow (cfs)Peak Flow Controlled?15,60214,57614,460WQv Drawdown Time:15,60214,57614,4600.3580.4460.332Storage Volume (ac-ft)
ReafieldUrban Design PartnersJOB NO.:16-115BY:udp1318-E6 Central AvenueDATE:05.15.17P.M.:lbtCharlotte, NC 28205REVISED:10.26.17 IMPERVIOUS CALCULATIONSExisting ImperviousBuilding: 0 sfConcrete: 0 sfAsphalt: 2,315 sfTotal Impervious Area:2,315sf0.05ac.Drainage Area:4.29Impervious Percentage: 1.2%Proposed ImperviousBuilding: 22,200 sfConcrete: 14,050 sfAsphalt: 60,938 sfFuture: 38,500 sfTotal Impervious Area:135,688 sf3.11ac.Drainage Area:4.29Impervious Percentage: 73%

BMP
ROUTINGS

1
Predeveloped
2
Post Developed
3
Sand Filter
Routing Diagram for 16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Subcat Reach Pond Link

1-YEAR
ROUTING

Type II 24-hr 1-yr Rainfall=2.93"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 3.89 cfs @ 12.09 hrs, Volume= 12,024 cf, Depth= 0.77"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 1-yr Rainfall=2.93"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)4
3
2
1
0
Type II 24-hr
1-yr Rainfall=2.93"
Runoff Area=4.320 ac
Runoff Volume=12,024 cf
Runoff Depth=0.77"
Tc=15.0 min
CN=72
3.89 cfs
Type II 24-hr 1-yr Rainfall=2.93"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 14.71 cfs @ 11.95 hrs, Volume= 31,458 cf, Depth= 2.01"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 1-yr Rainfall=2.93"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
1-yr Rainfall=2.93"
Runoff Area=4.320 ac
Runoff Volume=31,458 cf
Runoff Depth=2.01"
Tc=5.0 min
CN=91
14.71 cfs
Type II 24-hr 1-yr Rainfall=2.93"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 2.01" for 1-yr event
Inflow = 14.71 cfs @ 11.95 hrs, Volume= 31,458 cf
Outflow = 0.13 cfs @ 23.98 hrs, Volume= 31,226 cf, Atten= 99%, Lag= 721.9 min
Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf
Secondary = 0.13 cfs @ 23.98 hrs, Volume= 31,226 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 586.85' @ 23.98 hrs Surf.Area= 14,589 sf Storage= 25,626 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 2,238.3 min calculated for 31,226 cf (99% of inflow)
Center-of-Mass det. time= 2,233.7 min ( 3,035.5 - 801.8 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=584.50' (Free Discharge)
1=18" Outlet ( Controls 0.00 cfs)
3=Grate Top ( Controls 0.00 cfs)
Secondary OutFlow Max=0.13 cfs @ 23.98 hrs HW=586.85' (Free Discharge)
2=Sand Bed (Custom Controls 0.13 cfs)
Type II 24-hr 1-yr Rainfall=2.93"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=188,179 sf
Peak Elev=586.85'
Storage=25,626 cf
14.71 cfs
0.13 cfs
0.00 cfs
0.13 cfs
Type II 24-hr 1-yr Rainfall=2.93"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Hydrograph for Pond 3: Sand Filter
Time
(hours)
Inflow
(cfs)
Storage
(cubic-feet)
Elevation
(feet)
Outflow
(cfs)
Primary
(cfs)
Secondary
(cfs)
0.00 0.00 0 584.50 0.00 0.00 0.00
3.00 0.00 0 584.50 0.00 0.00 0.00
6.00 0.01 16 584.51 0.00 0.00 0.00
9.00 0.13 577 584.68 0.02 0.00 0.02
12.00 12.77 14,245 586.01 0.10 0.00 0.10
15.00 0.35 23,420 586.69 0.12 0.00 0.12
18.00 0.21 24,961 586.80 0.12 0.00 0.12
21.00 0.15 25,479 586.84 0.13 0.00 0.13
24.00 0.13 25,626 586.85 0.13 0.00 0.13
27.00 0.00 24,314 586.75 0.12 0.00 0.12
30.00 0.00 22,992 586.66 0.12 0.00 0.12
33.00 0.00 21,696 586.57 0.12 0.00 0.12
36.00 0.00 20,426 586.48 0.12 0.00 0.12
39.00 0.00 19,182 586.39 0.11 0.00 0.11
42.00 0.00 17,963 586.29 0.11 0.00 0.11
45.00 0.00 16,770 586.20 0.11 0.00 0.11
48.00 0.00 15,602 586.11 0.11 0.00 0.11
51.00 0.00 14,460 586.02 0.10 0.00 0.10
54.00 0.00 13,343 585.93 0.10 0.00 0.10
57.00 0.00 12,252 585.84 0.10 0.00 0.10
60.00 0.00 11,185 585.75 0.10 0.00 0.10
63.00 0.00 10,143 585.67 0.10 0.00 0.10
66.00 0.00 9,126 585.58 0.09 0.00 0.09
69.00 0.00 8,134 585.49 0.09 0.00 0.09
72.00 0.00 7,203 585.41 0.08 0.00 0.08
75.00 0.00 6,350 585.33 0.08 0.00 0.08
78.00 0.00 5,572 585.26 0.07 0.00 0.07
81.00 0.00 4,861 585.19 0.06 0.00 0.06
84.00 0.00 4,215 585.13 0.06 0.00 0.06
87.00 0.00 3,626 585.07 0.05 0.00 0.05
90.00 0.00 3,092 585.02 0.05 0.00 0.05
93.00 0.00 2,608 584.97 0.04 0.00 0.04
96.00 0.00 2,171 584.92 0.04 0.00 0.04
99.00 0.00 1,781 584.87 0.03 0.00 0.03
102.00 0.00 1,436 584.83 0.03 0.00 0.03
105.00 0.00 1,136 584.78 0.03 0.00 0.03
108.00 0.00 878 584.74 0.02 0.00 0.02
111.00 0.00 662 584.70 0.02 0.00 0.02
114.00 0.00 484 584.66 0.01 0.00 0.01
117.00 0.00 342 584.63 0.01 0.00 0.01
120.00 0.00 233 584.60 0.01 0.00 0.01
1-yr 24-hr Pre = 12,024 cf
1-yr 24-hr Post = 31,458 cf
WQv (Post - Pre) = 19,434 cf
75% WQv = 14,576 cf
Drawdown time = 50.7 hr

2-YEAR
ROUTING

Type II 24-hr 2-yr Rainfall=3.53"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 6.05 cfs @ 12.08 hrs, Volume= 17,886 cf, Depth= 1.14"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 2-yr Rainfall=3.53"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)6
5
4
3
2
1
0
Type II 24-hr
2-yr Rainfall=3.53"
Runoff Area=4.320 ac
Runoff Volume=17,886 cf
Runoff Depth=1.14"
Tc=15.0 min
CN=72
6.05 cfs
Type II 24-hr 2-yr Rainfall=3.53"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 18.59 cfs @ 11.95 hrs, Volume= 40,295 cf, Depth= 2.57"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 2-yr Rainfall=3.53"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
2-yr Rainfall=3.53"
Runoff Area=4.320 ac
Runoff Volume=40,295 cf
Runoff Depth=2.57"
Tc=5.0 min
CN=91
18.59 cfs
Type II 24-hr 2-yr Rainfall=3.53"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 2.57" for 2-yr event
Inflow = 18.59 cfs @ 11.95 hrs, Volume= 40,295 cf
Outflow = 0.56 cfs @ 13.96 hrs, Volume= 39,859 cf, Atten= 97%, Lag= 120.4 min
Primary = 0.43 cfs @ 13.96 hrs, Volume= 6,023 cf
Secondary = 0.13 cfs @ 13.96 hrs, Volume= 33,836 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 587.04' @ 13.96 hrs Surf.Area= 15,069 sf Storage= 28,476 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 2,001.3 min calculated for 39,859 cf (99% of inflow)
Center-of-Mass det. time= 1,994.4 min ( 2,789.2 - 794.8 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=0.38 cfs @ 13.96 hrs HW=587.04' (Free Discharge)
1=18" Outlet (Passes 0.38 cfs of 10.65 cfs potential flow)
3=Grate Top (Weir Controls 0.38 cfs @ 0.64 fps)
Secondary OutFlow Max=0.13 cfs @ 13.96 hrs HW=587.04' (Free Discharge)
2=Sand Bed (Custom Controls 0.13 cfs)
Type II 24-hr 2-yr Rainfall=3.53"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=188,179 sf
Peak Elev=587.04'
Storage=28,476 cf
18.59 cfs
0.56 cfs
0.43 cfs
0.13 cfs

10-YEAR
ROUTING

Type II 24-hr 10-yr Rainfall=5.15"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 12.75 cfs @ 12.07 hrs, Volume= 36,287 cf, Depth= 2.31"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 10-yr Rainfall=5.15"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
10-yr Rainfall=5.15"
Runoff Area=4.320 ac
Runoff Volume=36,287 cf
Runoff Depth=2.31"
Tc=15.0 min
CN=72
12.75 cfs
Type II 24-hr 10-yr Rainfall=5.15"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 29.01 cfs @ 11.95 hrs, Volume= 64,731 cf, Depth= 4.13"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 10-yr Rainfall=5.15"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
10-yr Rainfall=5.15"
Runoff Area=4.320 ac
Runoff Volume=64,731 cf
Runoff Depth=4.13"
Tc=5.0 min
CN=91
29.01 cfs
Type II 24-hr 10-yr Rainfall=5.15"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 4.13" for 10-yr event
Inflow = 29.01 cfs @ 11.95 hrs, Volume= 64,731 cf
Outflow = 11.67 cfs @ 12.08 hrs, Volume= 64,284 cf, Atten= 60%, Lag= 7.8 min
Primary = 11.53 cfs @ 12.08 hrs, Volume= 29,813 cf
Secondary = 0.14 cfs @ 12.08 hrs, Volume= 34,471 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 587.37' @ 12.08 hrs Surf.Area= 15,919 sf Storage= 33,648 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 1,264.4 min calculated for 64,252 cf (99% of inflow)
Center-of-Mass det. time= 1,262.2 min ( 2,043.8 - 781.7 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=11.02 cfs @ 12.08 hrs HW=587.35' (Free Discharge)
1=18" Outlet (Passes 11.02 cfs of 11.70 cfs potential flow)
3=Grate Top (Weir Controls 11.02 cfs @ 1.95 fps)
Secondary OutFlow Max=0.14 cfs @ 12.08 hrs HW=587.35' (Free Discharge)
2=Sand Bed (Custom Controls 0.14 cfs)
Type II 24-hr 10-yr Rainfall=5.15"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=188,179 sf
Peak Elev=587.37'
Storage=33,648 cf
29.01 cfs
11.67 cfs
11.53 cfs
0.14 cfs

25-YEAR
ROUTING

Type II 24-hr 25-yr Rainfall=6.13"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 17.16 cfs @ 12.07 hrs, Volume= 48,611 cf, Depth= 3.10"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 25-yr Rainfall=6.13"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
25-yr Rainfall=6.13"
Runoff Area=4.320 ac
Runoff Volume=48,611 cf
Runoff Depth=3.10"
Tc=15.0 min
CN=72
17.16 cfs
Type II 24-hr 25-yr Rainfall=6.13"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 35.25 cfs @ 11.95 hrs, Volume= 79,733 cf, Depth= 5.08"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 25-yr Rainfall=6.13"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
25-yr Rainfall=6.13"
Runoff Area=4.320 ac
Runoff Volume=79,733 cf
Runoff Depth=5.08"
Tc=5.0 min
CN=91
35.25 cfs
Type II 24-hr 25-yr Rainfall=6.13"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 5.08" for 25-yr event
Inflow = 35.25 cfs @ 11.95 hrs, Volume= 79,733 cf
Outflow = 12.95 cfs @ 12.08 hrs, Volume= 79,282 cf, Atten= 63%, Lag= 7.7 min
Primary = 12.80 cfs @ 12.08 hrs, Volume= 44,483 cf
Secondary = 0.15 cfs @ 12.08 hrs, Volume= 34,800 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 587.72' @ 12.08 hrs Surf.Area= 16,804 sf Storage= 39,339 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 1,038.2 min calculated for 79,282 cf (99% of inflow)
Center-of-Mass det. time= 1,034.5 min ( 1,810.6 - 776.1 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=12.75 cfs @ 12.08 hrs HW=587.70' (Free Discharge)
1=18" Outlet (Barrel Controls 12.75 cfs @ 7.22 fps)
3=Grate Top (Passes 12.75 cfs of 30.90 cfs potential flow)
Secondary OutFlow Max=0.15 cfs @ 12.08 hrs HW=587.70' (Free Discharge)
2=Sand Bed (Custom Controls 0.15 cfs)
Type II 24-hr 25-yr Rainfall=6.13"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=188,179 sf
Peak Elev=587.72'
Storage=39,339 cf
35.25 cfs
12.95 cfs
12.80 cfs
0.15 cfs

50-YEAR
ROUTING

Type II 24-hr 50-yr Rainfall=6.92"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 20.82 cfs @ 12.07 hrs, Volume= 58,978 cf, Depth= 3.76"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 50-yr Rainfall=6.92"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
50-yr Rainfall=6.92"
Runoff Area=4.320 ac
Runoff Volume=58,978 cf
Runoff Depth=3.76"
Tc=15.0 min
CN=72
20.82 cfs
Type II 24-hr 50-yr Rainfall=6.92"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 40.26 cfs @ 11.95 hrs, Volume= 91,895 cf, Depth= 5.86"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 50-yr Rainfall=6.92"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
50-yr Rainfall=6.92"
Runoff Area=4.320 ac
Runoff Volume=91,895 cf
Runoff Depth=5.86"
Tc=5.0 min
CN=91
40.26 cfs
Type II 24-hr 50-yr Rainfall=6.92"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 5.86" for 50-yr event
Inflow = 40.26 cfs @ 11.95 hrs, Volume= 91,895 cf
Outflow = 13.82 cfs @ 12.08 hrs, Volume= 91,442 cf, Atten= 66%, Lag= 8.0 min
Primary = 13.67 cfs @ 12.08 hrs, Volume= 56,400 cf
Secondary = 0.16 cfs @ 12.08 hrs, Volume= 35,042 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 588.03' @ 12.08 hrs Surf.Area= 17,598 sf Storage= 44,695 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 908.6 min calculated for 91,442 cf (100% of inflow)
Center-of-Mass det. time= 905.3 min ( 1,677.7 - 772.4 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=13.61 cfs @ 12.08 hrs HW=588.01' (Free Discharge)
1=18" Outlet (Barrel Controls 13.61 cfs @ 7.70 fps)
3=Grate Top (Passes 13.61 cfs of 53.24 cfs potential flow)
Secondary OutFlow Max=0.16 cfs @ 12.08 hrs HW=588.01' (Free Discharge)
2=Sand Bed (Custom Controls 0.16 cfs)
Type II 24-hr 50-yr Rainfall=6.92"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=188,179 sf
Peak Elev=588.03'
Storage=44,695 cf
40.26 cfs
13.82 cfs
13.67 cfs
0.16 cfs

100-YEAR
ROUTING

Type II 24-hr 100-yr Rainfall=7.73"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: Predeveloped
Runoff = 24.65 cfs @ 12.07 hrs, Volume= 69,914 cf, Depth= 4.46"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 100-yr Rainfall=7.73"
Area (ac) CN Description
* 4.320 72
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
15.0 Direct Entry, Pre Tc
Subcatchment 1: Predeveloped
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-yr Rainfall=7.73"
Runoff Area=4.320 ac
Runoff Volume=69,914 cf
Runoff Depth=4.46"
Tc=15.0 min
CN=72
24.65 cfs
Type II 24-hr 100-yr Rainfall=7.73"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Subcatchment 2: Post Developed
Runoff = 45.37 cfs @ 11.95 hrs, Volume= 104,408 cf, Depth= 6.66"
Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Type II 24-hr 100-yr Rainfall=7.73"
Area (ac) CN Description
* 4.320 91
4.320 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry, Post Tc
Subcatchment 2: Post Developed
Runoff
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Type II 24-hr
100-yr Rainfall=7.73"
Runoff Area=4.320 ac
Runoff Volume=104,408 cf
Runoff Depth=6.66"
Tc=5.0 min
CN=91
45.37 cfs
Type II 24-hr 100-yr Rainfall=7.73"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Summary for Pond 3: Sand Filter
Inflow Area = 188,179 sf, 0.00% Impervious, Inflow Depth = 6.66" for 100-yr event
Inflow = 45.37 cfs @ 11.95 hrs, Volume= 104,408 cf
Outflow = 14.60 cfs @ 12.08 hrs, Volume= 103,954 cf, Atten= 68%, Lag= 8.2 min
Primary = 14.44 cfs @ 12.08 hrs, Volume= 68,676 cf
Secondary = 0.16 cfs @ 12.08 hrs, Volume= 35,278 cf
Routing by Stor-Ind method, Time Span= 0.00-120.00 hrs, dt= 0.06 hrs
Peak Elev= 588.32' @ 12.08 hrs Surf.Area= 18,363 sf Storage= 49,977 cf
Flood Elev= 589.00' Surf.Area= 20,122 sf Storage= 62,974 cf
Plug-Flow detention time= 807.3 min calculated for 103,954 cf (100% of inflow)
Center-of-Mass det. time= 804.4 min ( 1,573.5 - 769.1 )
Volume Invert Avail.Storage Storage Description
#1 584.50' 62,974 cf Dry Detention (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
584.50 1,600 0 0
585.00 10,051 2,913 2,913
586.00 12,484 11,268 14,180
587.00 14,973 13,729 27,909
588.00 17,518 16,246 44,154
589.00 20,122 18,820 62,974
Device Routing Invert Outlet Devices
#1 Primary 584.50'18.0" Round 18" Outlet L= 67.0' Ke= 0.500
Inlet / Outlet Invert= 584.50' / 584.00' S= 0.0075 '/' Cc= 0.900
n= 0.013, Flow Area= 1.77 sf
#2 Secondary 584.50'Sand Bed
Head (feet) 0.00 1.00 2.00 3.00 4.00 4.50
Disch. (cfs) 0.000 0.091 0.117 0.143 0.169 0.181
#3 Device 1 587.00'1.0" x 1.0" Horiz. Grate Top X 48.00 columns
X 48 rows C= 0.600 in 48.0" x 48.0" Grate (100% open area)
Limited to weir flow at low heads
Primary OutFlow Max=14.38 cfs @ 12.08 hrs HW=588.30' (Free Discharge)
1=18" Outlet (Barrel Controls 14.38 cfs @ 8.14 fps)
3=Grate Top (Passes 14.38 cfs of 77.77 cfs potential flow)
Secondary OutFlow Max=0.16 cfs @ 12.08 hrs HW=588.30' (Free Discharge)
2=Sand Bed (Custom Controls 0.16 cfs)
Type II 24-hr 100-yr Rainfall=7.73"16-115 BMP
Prepared by Urban Design Partners
HydroCAD® 10.00-20 s/n 09103 © 2017 HydroCAD Software Solutions LLC
Pond 3: Sand Filter
Inflow
Outflow
Primary
Secondary
Hydrograph
Time (hours)
12011511010510095908580757065605550454035302520151050Flow (cfs)50
45
40
35
30
25
20
15
10
5
0
Inflow Area=188,179 sf
Peak Elev=588.32'
Storage=49,977 cf
45.37 cfs
14.60 cfs
14.44 cfs
0.16 cfs