DaVita Spencer - E&SC Stormwater Calc Report

Erosion Control and
Stormwater Report

DaVita Spencer

Project Location: Spencer, North Carolina Project #: 17-025

Designer:
Triad Design Group, P.C.
4807-C Koger Blvd
Greensboro, NC 27407

July 27, 2017

Stormwater Report Rowan County North Carolina
DaVita Spencer 17-025

1 | P a g e

Narrative:
The purpose of this project is to construct a 9,121 sf building with associated drive and parking aisles on
the 4.951 acre site located at the physical address of 1287 Salisbury Avenue. The existing site currently
has approximately 0.13 acres of BUA. An additional 0.94 acres of BUA are being proposed due to the
proposed construction, with an area for a 0.07 acres building addition bringing the total BUA to 1.14
acres or 23.02% BUA. A wet detention pond will be constructed to treat hand detain the increased flow
created by the additional BUA created due to the project. The 1, 2, and 10 year storm events have been
modeled and the runoff from wet detention pond has been reduced to pre-development rates. A
summary of the flows are listed below.

Drainage Area 1 -
Pre-Development
DA-1
Post-Development
DA-1
Drainage Area 1.67 AC 2.23 AC
CN 64 82
BUA 0.13 Acres 1.14 Acres
Tc 10 min 5 min

Flows –
Flows

Pre-Development
Condition DA-1
Post-Development
Condition DA-1
Routed Condition
DA-1
1-yr 24-hr 0.587 cfs 4.453 cfs 0.016cfs
2 yr 24-hr 1.229 cfs 6.115 cfs 0.146 cfs
10 yr 24-hr 3.380 cfs 10.81 cfs 3.005 cfs
100 yr 24-hr 7.435 cfs 18.30 cfs 8.961 cfs

PERMANENT WET DETENTION POND DESIGN - RISER/BARREL
Revised 8-24-99
GUILFORD COUNTY
PLANNING & DEVELOPMENT DEPARTMENT
INDEXINDEX NO:DaVita SpencerPROJECT:
MWJCHECKED BY:
April 06, 2017DATE:Spencer NCLOCATION:
REVISED:
SITE DATA
RANDLEMAN DAMWATERSHED =4.99TOTAL SITE AREA =
IVCLASSIFICATION : WS -0.13Existing BUILT UPON AREA =
GWA(GWA/WCA) =1.01Proposed BUILT UPON AREA =
1.14TOTAL ON-SITE BUILT UPON AREA =
22.85%PERCENT BUILT-UPON =
2.23 ON-SITE DRAINAGE AREA TO POND =
1.14ON-SITE BUA TO POND =
51.12%ONSITE % BUA FOR POND SUB-BASIN =
70%MAX. OFF-SITE B.U.% = 0.36 OFF-SITE DRAINAGE AREA TO POND =
2.59TOTAL WATERSHED AREA TO POND =
2.50DISTURBED AREA =
yTEMP. SED. STOR. USED (Y/N)
DESIGN DATA
acre-inch per disturbed acre0.5TEMPORARY SEDIMENT STORAGE
acre-in per total drainage area 0.125PERMANENT SEDIMENT STORAGE
PERMANENT WATER QUALITY
percent53.75COMPOSITE B.U. % =
feet3.4DEPTH (minimum 3 feet)
percent3.26SA/DA (Figure 5.6-2)
rainfall to be controlled1.0TEMPORARY WATER QUALITY
PRINCIPAL SPILLWAY
corrugated aluminumXTYPE
reinforced concrete
year10DESIGN STORM
inches per hour6.89RAINFALL INTENSITY
0.63RUNOFF COEFFICIENT
EMERGENCY SPILLWAY
grass linedXTYPE
rip-rap lined
year100DESIGN STORM
inches per hour8RAINFALL INTENSITY
0.8RUNOFF COEFFICIENT
POND DATA
829SURFACE AREA =730.5ELEV. @ BOT. OF POND =
829SURFACE AREA =730.5ELEV.@ BOT. OF PSS =
1364SURFACE AREA =732ELEV. @ BOT. OF PWQ =
5660SURFACE AREA =736.5ELEV. @ NORMAL POOL =
7978SURFACE AREA =737.75ELEV. @ TOP. OF RISER =
738.5ELEV. @ EMER. SPILLWAY =
740ELEV. @ TOP OF DAM =
728INVERT OF BARREL =
POND DESIGN
4538TEMPORARY SEDIMENT STORAGE VOLUME REQUIRED
POND CHECK Future- RISER2.qpw 07/28/17
Page 1
VOLUME PROVIDED
829SURFACE AREA =730.50ELEV. @ BOT. OF POND=
5660SURFACE AREA =736.50ELEV. @ NORMAL POOL =
14600ALLOW 75% OF BASIN VOLUME TO WQ ORIFICE =
OK
1175PERMANENT SEDIMENT STORAGE VOLUME REQUIRED
VOLUME PROVIDED
829SURFACE AREA =730.50ELEV. @ BOT. OF PSS =
1364SURFACE AREA =732.00ELEV. @ BOT. OF PWQ =
1645VOLUME PROVIDED =
OK
3678PERMANENT WATER QUALITY SURFACE AREA REQ'D
736.50NORMAL POOL ELEVATION =
5660SURFACE AREA PROVIDED =
OK
TEMPORARY WATER QUALITY STORAGE REQUIRED
0.534Rv=
5018VOLUME REQUIRED =
VOLUME PROVIDED
5660SURFACE AREA =736.50ELEV. @ BOT. OF TWQ =
7978SURFACE AREA =737.75ELEV. @ TOP OF TWQ =
8524VOLUME PROVIDED =
OK
POND CHECK Future- RISER2.qpw 07/28/17
Page 2
Average Depth
Option 1
Permanent pool voulme divided by permanent pool surface area
Pool Volume Pv =106418 Hydro Flow
Perm Pool Surface Area PSA =25832 Pond Check Sheet
Avg Depth davg =4.119619
Option 2
A bottom shelf Abs =4148
A perm pool App = 5659
A bottom pond Abp = 1366
Depth D = 4.5
davg =3.424207
Water Quality Draw Down Time
Size of Hole 0.75 0.003068
Storage Volume 6919
Surface Area of Pond ft^2 (As) 28067
Head of Water above Hole, ft (h) 2
Coefficient of Contraction of an orrifice (0.6) 0.6
Time to Dewater Days 3.83328
Q=0.02089 cfs
Qmin 0.01602 5 days
Qmax 0.04004 2 days
1 2
3
1
Watershed Model Schematic Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Project: Pond Routing.gpw Wednesday, 06 / 7 / 2017
Hyd.Origin Description
Legend
1 SCS Runoff Pre Development
2 SCS Runoff Post Development
3 Reservoir Proposed Pond
Hydrograph Return Period Recap
2
Hyd. Hydrograph Inflow Peak Outflow (cfs)Hydrograph
No. type hyd(s)Description
(origin) 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
1 SCS Runoff ------ 0.587 1.229 ------- ------- 3.380 ------- ------- 7.435 Pre Development
2 SCS Runoff ------ 4.453 6.115 ------- ------- 10.81 ------- ------- 18.30 Post Development
3 Reservoir 2 0.015 0.096 ------- ------- 1.681 ------- ------- 8.035 Proposed Pond
Proj. file: Pond Routing.gpw Wednesday, 06 / 7 / 2017
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Hydrograph Summary Report
3
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 0.587 2 724 2,251 ------ ------ ------ Pre Development
2 SCS Runoff 4.453 2 718 8,937 ------ ------ ------ Post Development
3 Reservoir 0.015 2 1444 3,914 2 737.53 21,376 Proposed Pond
Pond Routing.gpw Return Period: 1 Year Wednesday, 06 / 7 / 2017
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 1
Pre Development
Hydrograph type = SCS Runoff Peak discharge = 0.587 cfs
Storm frequency = 1 yrs Time to peak = 12.07 hrs
Time interval = 2 min Hyd. volume = 2,251 cuft
Drainage area = 1.670 ac Curve number = 64*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 10.00 min
Total precip. = 2.74 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.130 x 98) + (1.540 x 61)] / 1.670
4
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (hrs)
Pre Development
Hyd. No. 1 -- 1 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 2
Post Development
Hydrograph type = SCS Runoff Peak discharge = 4.453 cfs
Storm frequency = 1 yrs Time to peak = 11.97 hrs
Time interval = 2 min Hyd. volume = 8,937 cuft
Drainage area = 2.230 ac Curve number = 82*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 2.74 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.800 x 61) + (1.070 x 98) + (0.360 x 78)] / 2.230
5
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
Q (cfs)
Time (hrs)
Post Development
Hyd. No. 2 -- 1 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 3
Proposed Pond
Hydrograph type = Reservoir Peak discharge = 0.015 cfs
Storm frequency = 1 yrs Time to peak = 24.07 hrs
Time interval = 2 min Hyd. volume = 3,914 cuft
Inflow hyd. No. = 2 - Post Development Max. Elevation = 737.53 ft
Reservoir name = Proposed Pond Max. Storage = 21,376 cuft
Storage Indication method used. Wet pond routing start elevation = 736.25 ft.
6
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
Q (cfs)
Time (hrs)
Proposed Pond
Hyd. No. 3 -- 1 Year
Hyd No. 3 Hyd No. 2 Total storage used = 21,376 cuft
Hydrograph Summary Report
7
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 1.229 2 722 3,821 ------ ------ ------ Pre Development
2 SCS Runoff 6.115 2 716 12,347 ------ ------ ------ Post Development
3 Reservoir 0.096 2 1098 5,946 2 737.76 23,270 Proposed Pond
Pond Routing.gpw Return Period: 2 Year Wednesday, 06 / 7 / 2017
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 1
Pre Development
Hydrograph type = SCS Runoff Peak discharge = 1.229 cfs
Storm frequency = 2 yrs Time to peak = 12.03 hrs
Time interval = 2 min Hyd. volume = 3,821 cuft
Drainage area = 1.670 ac Curve number = 64*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 10.00 min
Total precip. = 3.31 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.130 x 98) + (1.540 x 61)] / 1.670
8
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
Q (cfs)
Time (hrs)
Pre Development
Hyd. No. 1 -- 2 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 2
Post Development
Hydrograph type = SCS Runoff Peak discharge = 6.115 cfs
Storm frequency = 2 yrs Time to peak = 11.93 hrs
Time interval = 2 min Hyd. volume = 12,347 cuft
Drainage area = 2.230 ac Curve number = 82*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 3.31 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.800 x 61) + (1.070 x 98) + (0.360 x 78)] / 2.230
9
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (hrs)
Post Development
Hyd. No. 2 -- 2 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 3
Proposed Pond
Hydrograph type = Reservoir Peak discharge = 0.096 cfs
Storm frequency = 2 yrs Time to peak = 18.30 hrs
Time interval = 2 min Hyd. volume = 5,946 cuft
Inflow hyd. No. = 2 - Post Development Max. Elevation = 737.76 ft
Reservoir name = Proposed Pond Max. Storage = 23,270 cuft
Storage Indication method used. Wet pond routing start elevation = 736.25 ft.
10
0 10 20 30 40 50 60 70 80 90 100
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
5.00 5.00
6.00 6.00
7.00 7.00
Q (cfs)
Time (hrs)
Proposed Pond
Hyd. No. 3 -- 2 Year
Hyd No. 3 Hyd No. 2 Total storage used = 23,270 cuft
Hydrograph Summary Report
11
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 3.380 2 722 9,118 ------ ------ ------ Pre Development
2 SCS Runoff 10.81 2 716 22,082 ------ ------ ------ Post Development
3 Reservoir 1.681 2 726 15,673 2 737.91 24,429 Proposed Pond
Pond Routing.gpw Return Period: 10 Year Wednesday, 06 / 7 / 2017
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 1
Pre Development
Hydrograph type = SCS Runoff Peak discharge = 3.380 cfs
Storm frequency = 10 yrs Time to peak = 12.03 hrs
Time interval = 2 min Hyd. volume = 9,118 cuft
Drainage area = 1.670 ac Curve number = 64*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 10.00 min
Total precip. = 4.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.130 x 98) + (1.540 x 61)] / 1.670
12
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (hrs)
Pre Development
Hyd. No. 1 -- 10 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 2
Post Development
Hydrograph type = SCS Runoff Peak discharge = 10.81 cfs
Storm frequency = 10 yrs Time to peak = 11.93 hrs
Time interval = 2 min Hyd. volume = 22,082 cuft
Drainage area = 2.230 ac Curve number = 82*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 4.81 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.800 x 61) + (1.070 x 98) + (0.360 x 78)] / 2.230
13
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Post Development
Hyd. No. 2 -- 10 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 3
Proposed Pond
Hydrograph type = Reservoir Peak discharge = 1.681 cfs
Storm frequency = 10 yrs Time to peak = 12.10 hrs
Time interval = 2 min Hyd. volume = 15,673 cuft
Inflow hyd. No. = 2 - Post Development Max. Elevation = 737.91 ft
Reservoir name = Proposed Pond Max. Storage = 24,429 cuft
Storage Indication method used. Wet pond routing start elevation = 736.25 ft.
14
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
10.00 10.00
12.00 12.00
Q (cfs)
Time (hrs)
Proposed Pond
Hyd. No. 3 -- 10 Year
Hyd No. 3 Hyd No. 2 Total storage used = 24,429 cuft
Hydrograph Summary Report
15
Hyd. Hydrograph Peak Time Time to Hyd. Inflow Maximum Total Hydrograph
No. type flow interval Peak volume hyd(s) elevation strge used Description
(origin) (cfs) (min) (min) (cuft) (ft) (cuft)
1 SCS Runoff 7.435 2 720 19,431 ------ ------ ------ Pre Development
2 SCS Runoff 18.30 2 716 38,305 ------ ------ ------ Post Development
3 Reservoir 8.035 2 722 31,889 2 738.51 29,571 Proposed Pond
Pond Routing.gpw Return Period: 100 Year Wednesday, 06 / 7 / 2017
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 1
Pre Development
Hydrograph type = SCS Runoff Peak discharge = 7.435 cfs
Storm frequency = 100 yrs Time to peak = 12.00 hrs
Time interval = 2 min Hyd. volume = 19,431 cuft
Drainage area = 1.670 ac Curve number = 64*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 10.00 min
Total precip. = 7.14 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.130 x 98) + (1.540 x 61)] / 1.670
16
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
2.00 2.00
4.00 4.00
6.00 6.00
8.00 8.00
Q (cfs)
Time (hrs)
Pre Development
Hyd. No. 1 -- 100 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 2
Post Development
Hydrograph type = SCS Runoff Peak discharge = 18.30 cfs
Storm frequency = 100 yrs Time to peak = 11.93 hrs
Time interval = 2 min Hyd. volume = 38,305 cuft
Drainage area = 2.230 ac Curve number = 82*
Basin Slope = 0.0 % Hydraulic length = 0 ft
Tc method = User Time of conc. (Tc) = 5.00 min
Total precip. = 7.14 in Distribution = Type II
Storm duration = 24 hrs Shape factor = 484
* Composite (Area/CN) = [(0.800 x 61) + (1.070 x 98) + (0.360 x 78)] / 2.230
17
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Q (cfs)
0.00 0.00
3.00 3.00
6.00 6.00
9.00 9.00
12.00 12.00
15.00 15.00
18.00 18.00
21.00 21.00
Q (cfs)
Time (hrs)
Post Development
Hyd. No. 2 -- 100 Year
Hyd No. 2
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Hyd. No. 3
Proposed Pond
Hydrograph type = Reservoir Peak discharge = 8.035 cfs
Storm frequency = 100 yrs Time to peak = 12.03 hrs
Time interval = 2 min Hyd. volume = 31,889 cuft
Inflow hyd. No. = 2 - Post Development Max. Elevation = 738.51 ft
Reservoir name = Proposed Pond Max. Storage = 29,571 cuft
Storage Indication method used. Wet pond routing start elevation = 736.25 ft.
18
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Q (cfs)
0.00 0.00
3.00 3.00
6.00 6.00
9.00 9.00
12.00 12.00
15.00 15.00
18.00 18.00
21.00 21.00
Q (cfs)
Time (hrs)
Proposed Pond
Hyd. No. 3 -- 100 Year
Hyd No. 3 Hyd No. 2 Total storage used = 29,571 cuft
Hydraflow Rainfall Report
19
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Return Intensity-Duration-Frequency Equation Coefficients (FHA)
Period
(Yrs) B D E (N/A)
1 62.3444 12.9000 0.8970 --------
2 69.3303 12.8000 0.8761 --------
3 0.0000 0.0000 0.0000 --------
5 70.1736 12.6000 0.8315 --------
10 72.6290 12.7000 0.8116 --------
25 60.3885 11.1000 0.7422 --------
50 47.4392 9.2000 0.6687 --------
100 47.9028 9.2000 0.6571 --------
File name: Rainfall Curve - Alamance Foods 15-083.IDF
Intensity = B / (Tc + D)^E
Return Intensity Values (in/hr)
Period
(Yrs) 5 min 10 15 20 25 30 35 40 45 50 55 60
1 4.69 3.76 3.15 2.72 2.39 2.14 1.94 1.77 1.64 1.52 1.42 1.33
2 5.56 4.48 3.77 3.26 2.88 2.58 2.34 2.15 1.98 1.84 1.72 1.62
3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
5 6.46 5.25 4.45 3.87 3.44 3.10 2.83 2.60 2.41 2.25 2.11 1.99
10 7.05 5.76 4.90 4.28 3.82 3.45 3.15 2.91 2.70 2.53 2.37 2.24
25 7.68 6.28 5.36 4.71 4.22 3.83 3.52 3.26 3.04 2.85 2.69 2.55
50 8.05 6.58 5.63 4.97 4.47 4.08 3.77 3.50 3.29 3.10 2.93 2.79
100 8.38 6.87 5.90 5.22 4.70 4.30 3.97 3.70 3.48 3.28 3.11 2.96
Tc = time in minutes. Values may exceed 60.
Rainfall Precipitation Table (in)
Precip. file name: Sample.pcp
Storm
Distribution 1-yr 2-yr 3-yr 5-yr 10-yr 25-yr 50-yr 100-yr
SCS 24-hour 2.74 3.31 0.00 3.30 4.81 5.81 6.80 7.14
SCS 6-Hr 0.00 1.80 0.00 0.00 2.60 0.00 0.00 4.00
Huff-1st 0.00 1.55 0.00 2.75 4.00 5.38 6.50 8.00
Huff-2nd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-3rd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-4th 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Huff-Indy 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Custom 0.00 1.75 0.00 2.80 3.90 5.25 6.00 7.10
Hydraflow Table of Contents Pond Routing.gpw
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v11 Wednesday, 06 / 7 / 2017
Watershed Model Schematic..................................................................................... 1
Hydrograph Return Period Recap............................................................................. 2
1 - Year
Summary Report......................................................................................................................... 3
Hydrograph Reports................................................................................................................... 4
Hydrograph No. 1, SCS Runoff, Pre Development.................................................................. 4
Hydrograph No. 2, SCS Runoff, Post Development................................................................. 5
Hydrograph No. 3, Reservoir, Proposed Pond......................................................................... 6
2 - Year
Summary Report......................................................................................................................... 7
Hydrograph Reports................................................................................................................... 8
Hydrograph No. 1, SCS Runoff, Pre Development.................................................................. 8
Hydrograph No. 2, SCS Runoff, Post Development................................................................. 9
Hydrograph No. 3, Reservoir, Proposed Pond....................................................................... 10
10 - Year
Summary Report....................................................................................................................... 11
Hydrograph Reports................................................................................................................. 12
Hydrograph No. 1, SCS Runoff, Pre Development................................................................ 12
Hydrograph No. 2, SCS Runoff, Post Development............................................................... 13
Hydrograph No. 3, Reservoir, Proposed Pond....................................................................... 14
100 - Year
Summary Report....................................................................................................................... 15
Hydrograph Reports................................................................................................................. 16
Hydrograph No. 1, SCS Runoff, Pre Development................................................................ 16
Hydrograph No. 2, SCS Runoff, Post Development............................................................... 17
Hydrograph No. 3, Reservoir, Proposed Pond....................................................................... 18
IDF Report.................................................................................................................. 19
DaVita Spencer
Skimmer Basin NO. 1
DRAINAGE AREA = 2.34 Acres
DISTURBED AREA = 2.34 Acres 4807-C Koger Blvd
Greensboro, NC 27407
REQUIRED SURFACE AREA FOR 75% TRAPPING EFFICIENCY 336-218-8282 * 336-218-8010 Fax
Surface Area (SA) = 0.01 x Peak Flow (Q10)
Peak Flow = CIA
Runoff Coefficient(C) = 0.45
Intensity(I) = 6.85 in/hr
Area(A) = 2.34 Acres
Peak Flow = 7.21 CFS
Required Surface Area (SA) = 0.054 Acres
2344 sf
REQUIRED SEDIMENT STORAGE VOLUME
VOL = DISTURBED AREA x 1800 cf/Acre
VOL = 4212 cf
TRIAL SIZE (LENGTH = 2 x WIDTH)
Width = (Surface Area/2)^0.5 Length = 2 x Width
Width = 34.2 ft Length = 68.5 ft
ACTUAL BASIN SIZE
WIDTH LENGTH DEPTH
TOP 112 35 2.5
BOTTOM 102 25 OFFSET
4
SA PROVIDED = 3920 sf
SA REQUIRED = 2344 sf
STORAGE PROVIDED = 8025 cf
STORAGE REQUIRED = 4212 cf
WEIR LENGTH (TABLE 6.60a NCDENR MANUAL)
Weir = 6 ft
SKIMMER TRAP CALCULATION FOR
EFFICIENCY BASED DESIGN
Calculate Skimmer Size
Basin Volume in Cubic Feet 14,600 Cu.Ft Skimmer Size 2.0 Inch
Days to Drain*5 Days Orifice Radius 0.9 Inch[es]
Orifice Diameter 1.8 Inch[es]
*In NC assume 3 days to drain
Estimate Volume of Basin Length Width
Top of water surface in feet Feet VOLUME 0 Cu. Ft.
Bottom dimensions in feet Feet
Depth in feet Feet