SW3201203_Stormwater Report_20210120

Encore at Streamside
Stormwater Impact Analysis and Final Design of Stormwater Management Facilities
ENCORE AT STREAMSIDE
Union County, North Carolina
Stormwater Impact Analysis &
Design of Stormwater Control Measures
Project Number:DWH-19010
Designed By:Marc Van Dine, PE
Stuart Woodard, PE
Date:December 2020
3430 Toringdon Way, Suite 110
Charlotte, North Carolina 28277
NC Lic. # C-0293
STORMWATER IMPACT ANALYSIS
creating experiences through experience 3430 Toringdon Way, Suite 110, Charlotte, NC 28277 /704.527. 0800
GENERAL DESCRIPTION
Located in Union County east of the intersection of S Providence Road and Cuthbertson Road is the
proposed Encore at Streamside single-family subdivision development.The existing site consists of
heavily wooded areas as well as open agricultural fields. Proposed development on this site will consist of
the construction of single-family homes and amenity center along with the associated roads and
sidewalks, utility improvements, and three stormwater control measures.
The proposed development is located within the Catawba River basin with stormwater runoff from the
proposed development draining into East Fork Twelvemile Creek as well as a small portion of the site
draining to West Fork Twelvemile Creek. Ultimately all runoff combines into Twelvemile Creek at the
western property boundary. This development is located within Union County and as a result the
proposed stormwater management on this site shall meet both Union County’s Development Standards
as well as the stormwater management performance standards for development set forth by NCDEQ’s
Phase II Post-Construction SW requirements. These are as follows:
Union County Development Standards:
60.170-C Stormwater Management
3.Post-development stormwater discharge rates at the property boundary of an approved
cluster development may not exceed the pre-development rate for the 2-and 25-year storm events. This
regulation does not apply if discharging directly into a FEMA-regulated floodplain.
This project is exempt from this requirement as each facility discharges directly into a FEMA-regulated
floodplain. As a result stormwater detention is not required. Stormwater quality is required and is per the
state performance standards.
In order to meet the water quality requirements,three wet ponds are proposed. The existing pond on-
site will serve as an amenity and is not proposed to be used for either stormwater quantity or quality
control. This report serves as he stormwater impact analysis for the proposed development and includes
design calculations for these facilities.
CALCULATION METHODOLOGY
>Rainfall data for the analysis was taken from NOAA Atlas 14.Please reference the precipitation
information section within this report for additional information.
>Using maps contained within the Union county Soil Survey, the on-site soils were determined to
be hydrologic soil groups (HSG)‘B’and ‘C’soils. Since the method chosen to compute post-
development peak flow rates and runoff volumes is dependent upon the soil type, care was taken
when selecting the appropriate Soil Conservation Service Curve Number (SCS CN). A composite
SCS CN was computed for each post-development sub-basin. For example,Sub-basin #3 in the
post-development analysis consists of approximately 75% HSG ‘B’, and 25% HSG ‘C’soils.
Therefore, for the wooded cover condition, the composite SCS CN is computed as follows
(assuming good conditions):
>Composite Wooded SCS CN =(75%x 55)+ (25% x 70) =59
STORMWATER IMPACT ANALYSIS
creating experiences through experience 2 of 2
>A composite SCS Curve Number was calculated for the post-development condition for each sub-
basin using SCS curve numbers and land cover conditions.Land cover conditions for the post-
development condition were taken from the proposed development plan.
>The time of concentration was calculated using SCS TR-55 (Segmental Approach, 1986). The Tc
flow path was divided into three segments: overland flow,concentrated flow, and channel flow.
The travel time was then computed for each segment, from which the overall time of
concentration was determine by taking the sum of each segmental time.For each sub-basin
draining to a stormwater control measure a minimum time of concentration of 5 minutes was
assumed.
>PondPack Version V8i was used in determined the post-development peak flow rates for the 1-,
2-, 10-,25-, and 100-year storm events, as well as routing calculations for the proposed
stormwater control measure.
>The proposed stormwater control measures were designed in accordance with the Minimum
Design Criteria (MDC) standards set forth in the NCDEQ Stormwater Design Manual.
DISCUSSION OF RESULTS
Peak Runoff Control Requirements:
Peak runoff control is not required for this project. Per the Union County development standards quantity
control is not required if discharging directly into a FEMA-regulated floodplain which such is the case for
this development.The stormwater control measures have been designed to safely pass the higher storm
events.
Water Quality Requirements:
The proposed facilities has been designed in accordance with the Minimum Design Criteria (MDC)
standards set forth in the NCDEQ Stormwater Design Manual.The proposed facilities will provide the
required 85% TSS removal.
CONCLUSION
If the development on this tract is built as proposed within this report, then the requirements set forth in
Union County’s Development Standards will be met. However, modifications to the proposed
development may require that this analysis be revised. Some modifications that would require this
analysis to be revised include:
>The proposed site impervious surface exceeds the amount accounted for in this report.
>The post-development watershed breaks change significantly from those used to prepare this
report.
The above modifications may result in the assumptions within this report becoming invalid. The
computations within this report will need to be revisited if any of the above conditions become apparent
as development of the proposed site moves forward.
5 POST-DEVELOPMENT HYDROLOGIC
CALCULATIONS
8 STORMWATER CONTROL MEASURE C DESIGN
CALCULATIONS
6 STORMWATER CONTROL MEASURE A DESIGN
CALCULATIONS
7 STORMWATER CONTROL MEASURE B DESIGN
CALCULATIONS
4 SITE PRECIPITATION DATA
1 SUMMARY OF RESULTS
2 MISCELLANEOUS SITE INFORMATION
3 WATERSHED SOILS INFORMATION
ENCORE AT STREAMSIDE
DWH-19010
SUMMARY OF RESULTS
Subsection: Master Network Summary
Catchments Summary
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
5.249187.008,468.0000Post WQVSub-1
31.578186.0046,121.0002Post 2-yearSub-1
72.193186.00124,943.00025Post 25-yearSub-1
93.034186.00163,494.000100Post 100-yearSub-1
5.162186.508,033.0000Post WQVSub-2
27.982186.0040,864.0002Post 2-yearSub-2
62.027186.00107,938.00025Post 25-yearSub-2
79.461186.00140,499.000100Post 100-yearSub-2
9.560187.5018,569.0000Post WQVSub-3
86.251186.50126,844.0002Post 2-yearSub-3
217.360186.00371,541.00025Post 25-yearSub-3
285.405186.00494,117.000100Post 100-yearSub-3
Node Summary
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
0.139363.006,377.0000Post WQVPOA-1
5.456208.0035,814.0002Post 2-yearPOA-1
45.382191.00114,565.00025Post 25-yearPOA-1
63.481189.50153,095.000100Post 100-yearPOA-1
0.123363.006,109.0000Post WQVPOA-2
3.992212.5030,296.0002Post 2-yearPOA-2
43.629189.5097,288.00025Post 25-yearPOA-2
61.501188.50129,823.000100Post 100-yearPOA-2
0.387362.5015,625.0000Post WQVPOA-3
6.799241.50104,313.0002Post 2-yearPOA-3
96.913194.50348,284.00025Post 25-yearPOA-3
178.456191.00470,643.000100Post 100-yearPOA-3
Pond Summary
Maximum
Pond Storage
(ft³)
Maximum
Water
Surface
Elevation
(ft)
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
(N/A)(N/A)5.249187.008,468.0000Post WQVSCM A (IN)
7,219.000536.490.139363.006,377.0000Post WQVSCM A
(OUT)
(N/A)(N/A)31.578186.0046,121.0002Post 2-yearSCM A (IN)
26,748.000537.655.456208.0035,814.0002Post 2-yearSCM A
(OUT)
(N/A)(N/A)72.193186.00124,943.00025Post 25-yearSCM A (IN)
45,088.000538.6445.382191.00114,565.00025Post 25-yearSCM A
(OUT)
(N/A)(N/A)93.034186.00163,494.000100Post 100-yearSCM A (IN)
52,686.000539.0263.481189.50153,095.000100Post 100-yearSCM A
(OUT)
(N/A)(N/A)5.162186.508,033.0000Post WQVSCM B (IN)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Subsection: Master Network Summary
Pond Summary
Maximum
Pond Storage
(ft³)
Maximum
Water
Surface
Elevation
(ft)
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
6,836.000519.600.123363.006,109.0000Post WQVSCM B
(OUT)
(N/A)(N/A)27.982186.0040,864.0002Post 2-yearSCM B (IN)
25,400.000520.973.992212.5030,296.0002Post 2-yearSCM B
(OUT)
(N/A)(N/A)62.027186.00107,938.00025Post 25-yearSCM B (IN)
37,884.000521.8143.629189.5097,288.00025Post 25-yearSCM B
(OUT)
(N/A)(N/A)79.461186.00140,499.000100Post 100-yearSCM B (IN)
42,918.000522.1261.501188.50129,823.000100Post 100-yearSCM B
(OUT)
(N/A)(N/A)9.560187.5018,569.0000Post WQVSCM C (IN)
14,924.000513.360.387362.5015,625.0000Post WQVSCM C
(OUT)
(N/A)(N/A)86.251186.50126,844.0002Post 2-yearSCM C (IN)
87,002.000514.876.799241.50104,313.0002Post 2-yearSCM C
(OUT)
(N/A)(N/A)217.360186.00371,541.00025Post 25-yearSCM C (IN)
162,455.000516.2996.913194.50348,284.00025Post 25-yearSCM C
(OUT)
(N/A)(N/A)285.405186.00494,117.000100Post 100-yearSCM C (IN)
186,128.000516.71178.456191.00470,643.000100Post 100-yearSCM C
(OUT)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
ENCORE AT STREAMSIDE
DWH-19010
MISCELLANEOUS SITE INFORMATION
NC Center for Geographic Information & Analysis, Esri, HERE, Garmin, ©OpenStreetMap contributors
0 2,00 0 4,00 01,00 0 Feet1 inch = 2,000 feet
¯ENCORE AT STREAMSIDE
SITE A ERIAL MAPPROJECT #: DWH -19010UNION COUNTY, NORTH CAROLINA
Copyright:© 2013 National Geographic Society, i-cubed
0 2,000 4,0001,000 Feet1 inch = 2,000 feet
¯ENCORE AT STREAMSIDE
USGS TOPO MAPPROJECT #: DWH -19010UNION COUNTY, NORTH CAROLINA
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ENCORE AT STREAMSIDE
DWH-19010
WATERSHED SOILS INFORMATION
ENCORE AT STREAMSIDE
DWH-19010
PRECIPITATION DATA
Storm Data Detailed
Report: Charlotte
Element Details
206ID Notes
CharlotteLabel
1 inch
1 inchLabel min5.00Increment
years0Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
1 inch
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0030.0030.0030.0030.0000.00
0.0040.0040.0040.0030.00325.00
0.0040.0040.0040.0040.00450.00
0.0060.0050.0050.0050.00575.00
0.0080.0080.0070.0070.007100.00
0.0120.0110.0100.0090.009125.00
0.0390.0250.0220.0190.013150.00
0.0430.0750.1880.1080.050175.00
0.0120.0140.0200.0230.028200.00
0.0080.0090.0090.0100.011225.00
0.0060.0070.0070.0070.008250.00
0.0050.0050.0050.0050.005275.00
0.0040.0040.0040.0040.004300.00
0.0030.0030.0040.0040.004325.00
(N/A)(N/A)0.0030.0030.003350.00
1 year 24 hr
1 year 24 hrLabel min6.00Increment
years1Return Event min1,440.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
1 year 24 hr
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0030.0030.0030.0030.0000.00
0.0030.0030.0030.0030.00330.00
0.0030.0030.0030.0030.00360.00
0.0030.0030.0030.0030.00390.00
0.0030.0030.0030.0030.003120.00
0.0030.0030.0030.0030.003150.00
0.0040.0030.0030.0030.003180.00
0.0040.0030.0040.0040.003210.00
0.0040.0040.0040.0040.004240.00
0.0040.0040.0040.0040.004270.00
0.0040.0040.0040.0040.004300.00
0.0050.0040.0040.0050.004330.00
0.0050.0050.0050.0050.005360.00
0.0050.0050.0050.0050.005390.00
0.0050.0050.0050.0050.005420.00
0.0060.0050.0050.0050.005450.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Data Detailed
Report: Charlotte
1 year 24 hr
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0070.0060.0060.0060.006480.00
0.0080.0080.0080.0070.007510.00
0.0080.0080.0080.0080.008540.00
0.0100.0090.0090.0090.008570.00
0.0120.0120.0110.0110.010600.00
0.0170.0160.0150.0140.013630.00
0.0270.0250.0220.0200.018660.00
0.3540.1970.1230.0610.030690.00
0.0320.0370.0430.0490.245720.00
0.0180.0190.0210.0220.025750.00
0.0130.0140.0140.0160.017780.00
0.0100.0110.0110.0120.012810.00
0.0090.0090.0090.0100.010840.00
0.0080.0080.0090.0090.009870.00
0.0070.0070.0080.0080.008900.00
0.0060.0070.0070.0070.007930.00
0.0060.0060.0060.0060.006960.00
0.0050.0050.0050.0060.006990.00
0.0050.0050.0050.0050.0051,020.00
0.0050.0050.0050.0050.0051,050.00
0.0040.0050.0040.0050.0051,080.00
0.0040.0040.0040.0040.0041,110.00
0.0040.0040.0040.0040.0041,140.00
0.0040.0030.0040.0040.0041,170.00
0.0030.0030.0030.0030.0031,200.00
0.0030.0030.0030.0030.0031,230.00
0.0030.0030.0030.0030.0031,260.00
0.0030.0030.0030.0030.0031,290.00
0.0030.0030.0030.0030.0031,320.00
0.0030.0030.0030.0030.0031,350.00
0.0030.0030.0030.0030.0031,380.00
0.0030.0030.0030.0030.0031,410.00
(N/A)(N/A)(N/A)(N/A)0.0031,440.00
2 year
2 yearLabel min5.00Increment
years2Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
2 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0080.0080.0070.0070.0000.00
0.0090.0090.0080.0080.00825.00
0.0100.0100.0100.0090.00950.00
0.0140.0120.0110.0110.01175.00
0.0180.0170.0160.0150.014100.00
0.0280.0260.0240.0220.021125.00
0.0890.0580.0500.0440.031150.00
0.1000.1680.4200.2420.115175.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Data Detailed
Report: Charlotte
2 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0290.0330.0470.0540.064200.00
0.0180.0210.0230.0250.027225.00
0.0140.0150.0160.0160.017250.00
0.0100.0110.0110.0120.012275.00
0.0090.0090.0090.0100.010300.00
0.0080.0080.0080.0080.009325.00
(N/A)(N/A)0.0070.0070.008350.00
10 year
10 yearLabel min5.00Increment
years10Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
10 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0120.0120.0110.0110.0000.00
0.0130.0130.0130.0120.01225.00
0.0160.0150.0150.0140.01450.00
0.0230.0180.0180.0170.01675.00
0.0290.0270.0260.0250.024100.00
0.0490.0450.0420.0390.036125.00
0.1610.1030.0890.0790.054150.00
0.1770.2750.5900.3950.201175.00
0.0510.0570.0840.0960.112200.00
0.0300.0380.0400.0430.047225.00
0.0230.0240.0250.0270.028250.00
0.0160.0170.0170.0180.019275.00
0.0140.0140.0150.0150.016300.00
0.0120.0120.0130.0130.013325.00
(N/A)(N/A)0.0110.0110.012350.00
25 year
25 yearLabel min5.00Increment
years25Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
25 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0150.0140.0140.0140.0000.00
0.0170.0160.0160.0150.01525.00
0.0190.0190.0180.0180.01750.00
0.0250.0230.0220.0210.02075.00
0.0330.0310.0290.0280.027100.00
0.0580.0530.0490.0460.043125.00
0.1890.1200.1040.0930.064150.00
0.2080.3240.6800.4660.235175.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Data Detailed
Report: Charlotte
25 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0610.0670.0980.1110.131200.00
0.0340.0450.0480.0510.055225.00
0.0260.0270.0290.0300.032250.00
0.0200.0210.0210.0220.023275.00
0.0170.0170.0180.0190.019300.00
0.0150.0150.0160.0160.016325.00
(N/A)(N/A)0.0140.0140.014350.00
50 year
50 yearLabel min5.00Increment
years50Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
50 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0170.0160.0160.0160.0000.00
0.0190.0190.0180.0180.01725.00
0.0220.0220.0210.0200.02050.00
0.0310.0260.0250.0240.02375.00
0.0390.0370.0350.0330.032100.00
0.0660.0610.0560.0530.049125.00
0.2090.1330.1160.1030.073150.00
0.2310.3560.7490.5130.260175.00
0.0690.0770.1090.1240.145200.00
0.0400.0510.0540.0580.063225.00
0.0310.0330.0340.0360.038250.00
0.0230.0230.0240.0250.026275.00
0.0190.0200.0210.0210.022300.00
0.0170.0170.0180.0180.019325.00
(N/A)(N/A)0.0160.0160.017350.00
100 year
100 yearLabel min5.00Increment
years100Return Event min360.00End Time
min0.00Start Time IncrementalStorm Event Depth Type
100 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0180.0180.0170.0170.0000.00
0.0210.0200.0200.0200.01925.00
0.0240.0230.0230.0220.02250.00
0.0320.0280.0270.0260.02575.00
0.0410.0390.0370.0350.034100.00
0.0710.0650.0600.0560.053125.00
0.2260.1470.1260.1130.078150.00
0.2500.3860.8300.5550.282175.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Data Detailed
Report: Charlotte
100 year
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Depth
(in)
Time
(min)
0.0740.0820.1190.1360.160200.00
0.0420.0550.0580.0630.068225.00
0.0330.0340.0360.0380.040250.00
0.0250.0250.0260.0270.029275.00
0.0210.0220.0220.0230.024300.00
0.0190.0190.0200.0200.021325.00
(N/A)(N/A)0.0170.0180.018350.00
100 year 50 year 25 year 10 year 2 year
1 year 24 hr 1 inchDepth (in)0.875
0.750
0.625
0.500
0.375
0.250
0.125
0.000
Time (min)
1,440.001,296.001,152.001,008.00864.00720.00576.00432.00288.00144.000.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
ENCORE AT STREAMSIDE
DWH-19010
POST-DEVELOPMENT HYDROLOGIC
CALCULATIONS
CLIENT
REVISIONS
PROJECT NO.DWH-19010
FILENAME
CHECKED BY SAW
DRAWN BY SAW/AJB/SAG/JMC
SCALE
DATE 10. 12. 2020
N0.DATE
Y:\Projects\DWH\DWH-19010\04-Production\Engineering\Construction Drawings\Current Drawings\DWH19010-Post.dwg, 11/19/2020 3:29:24 PM, Woodard, StuartThe John R. McAdams Company, Inc.
www.mcadamsco.com
3430 Toringdon Way
Suite 110
phone [phone]
fax [phone]
license number: C-0293, C-187
Charlotte, NC 28277
ENCORE AT STREAMSIDECONSTRUCTION DRAWINGS2219 CUTHBERTSON ROADWAXHAW, NORTH CAROLINA, 28173SHEET
PLAN INFORMATION
FINAL DRAWING - NOT RELEASED FOR CONSTRUCTION
DAVID WEEKLEY HOMES - CHARLOTTE DIVISION
11430 NORTH COMMUNITY HOUSE ROAD
SUITE 275, CHARLOTTE, NC 28277
PHONE: [phone]
DWH19010-Post
POST
1"=200'
POST DEVELOPMENTGRAPHIC SCALE
0 100 200 400
1 inch = 200 ft.
SITE LEGEND
CONTRACTOR SHALL NOTIFY "NC811" (811) OR (1-800-632-4949) AT
LEAST 3 FULL BUSINESS DAYS PRIOR TO BEGINNING CONSTRUCTION
OR EXCAVATION TO HAVE EXISTING UTILITIES LOCATED.
CONTRACTOR SHALL CONTACT ANY LOCAL UTILITIES THAT PROVIDE
THEIR OWN LOCATOR SERVICES INDEPENDENT OF "NC811".
REPORT ANY DISCREPANCIES TO THE ENGINEER IMMEDIATELY.
R
EXISTING
CUTHBERTSON ROAD
(PUBLIC R/W)
ADJACENT PARCEL INFORMATION
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
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24
25
26272829
30
31323334353637383940
41
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44
45
46
47
48
50
5152
53
54
55 56
57
58
59
6061
62
6364
65
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67 68
69 70 71
72
73
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78
97
96
94
93
92
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90
89
8879
80
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83 84 85 86 87
98
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100
101
102
322
321
320
319
318
317
316
315
314
313
312
311
310
309
308
307
306
305
304
303
302301
300
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297
256 257 258 259 260
261
262
263
264
265
266
267
268
269
270
271
255
254
253
252
251
250
249
248
247
272 273 274
275 276
277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296
160 161
159
158
157
156
155
154
153
152
151
150
216 215 214 213 212 211 210 209 208 207 206
191
192
193
194 195 196 197 198 199 200 201 202 203 204 205
218
219
220
246 245 244 243 242 241 240 239 238 237 236 235
221 222 223 224 225 226 227 228 229 230 231 232 233 234
167
166
179 178
177
176
175
174
182
183
184
185
186
187
188
181180
165
164
163
162
49
190
189
149 148 147 146 145 144 143 142 141 140 139 138 137 136
135 134
173172171170
169
168
133
132
131
130
129 128
103
104
105
106
107
108
109
110
111
112
127
126
125
124
123
122
121
120
119
113
114
115
116
117118
95
ENCORE

L
A
N
E
BOURN LANE
MEANDER LANE
MEANDE
R
L
A
N
E
LOWLAND ALLEYENCORE LA
N
ECANE WAYENCORE LANEIDYLLIC LANEID
Y
L
L
I
C

L
A
N
E
M
I
N
E
R
A
L

W
A
Y
PASTO
R
A
L
P
L
A
C
E
FEN L
A
N
E
PASTORAL PLACE
217
HYDROLOGY MAP
POA 1
SUB 1-TO SCM A
AREA = 11.90 AC
POA 2
SUB 2-TO SCM B
AREA = 9.95 AC
POA 3
SUB 3-TO SCM C
AREA = 38.55 AC
SCM A
SCM B
SCM C
Project Name: Encore at Streamside Date: 12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
INPUT SUMMARY
Total Area
Subbasin ID Impervious Open Wooded Pond Total Impervious Open Wooded Pond 2-ac Lots Total [acres]SCS CN Tc [min]
1-To SCM A 5.41 6.01 0.00 0.31 11.73 0.16 0.00 0.00 0.00 0.00 0.16 11.90 86 5.00
2-To SCM B 4.94 4.77 0.00 0.24 9.95 0.00 0.00 0.00 0.00 0.00 0.00 9.95 87 5.00
3-To SCM C 20.62 17.60 0.00 0.86 39.08 0.00 0.00 0.00 0.00 0.00 0.00 39.08 83 5.00
Totals 5.41 6.01 0.00 0.31 11.73 0.16 0.00 0.00 0.00 0.00 0.16 11.90
POST DEVELOPMENT HYDROLOGIC SUMMARY
Onsite Area [acres]Offsite Area [acres]
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Subbasin ID:1-To SCM A
SCS CURVE NUMBER
(REF: TR-55 and NRCS Web Soil Survey).
HSG Impervious Open Wooded Pond
A 98 39 30 100
B 98 61 55 100
C 98 74 70 100
D 98 80 77 100
HSG 'A' =0%
HSG 'B' =0%
HSG 'C' =100%
HSG 'D' =0%
Cover Composite
Condition SCS CN
Impervious 98
Open 74
Wooded 70
Pond 100
WATERSHED BREAKDOWN
# of Onsite Lots =40 Type Area No. of Units Imp. Area
Assumed Impervious Area per Lot =3,374 sf Bldg Pad Area 45 x 75 9 30375
Total Impervious Area from Onsite Lots =134,950 sf Bldg Pad Area 35 x 75 31 81375
Driveways 20 x 20 48 19200
Additional Onsite Impervious Area =100,858 sf Patios 10 x 10 40 4000
Total 134950
Composite Area Area
SCS CN [sf][acres]
98 235,808 5.41 Type Area
74 261,976 6.01 Roadway 70009
70 0 0.00 Sidewalk 24369
100 13,323 0.31 Driveways 6480
98 7,173 0.16 Total 100858
74 0 0.00
70 0 0.00
100 0 0.00
Total Area =518,280 sf
=11.90 acres
Composite SCS CN =86
% Impervious =46.88%
TIME OF CONCENTRATION
Time of Concentration =5.00 minutes
SCS Lag Time =3.00 minutes
Offsite Wooded Assume good condition
Offsite Pond -
Onsite Pond -
Offsite Impervious -
Offsite Open Assume good condition
Onsite Impervious -
Onsite Open Assume good condition
Onsite Wooded Assume good condition
Impervious Area Outside of Right-of-Way (Onsite Lots)
Additional On-Site Imp. Area
-
POST DEVELOPMENT HYDROLOGIC CALCULATIONS
Comments
-
Assume good condition
Assume good condition
Contributing Area Comments
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Subbasin ID:2-To SCM B
SCS CURVE NUMBER
(REF: TR-55 and NRCS Web Soil Survey).
HSG Impervious Open Wooded Pond
A 98 39 30 100
B 98 61 55 100
C 98 74 70 100
D 98 80 77 100
HSG 'A' =0%
HSG 'B' =0%
HSG 'C' =100%
HSG 'D' =0%
Cover Composite
Condition SCS CN
Impervious 98
Open 74
Wooded 70
Pond 100
WATERSHED BREAKDOWN
# of Onsite Lots =38 Type Area No. of Units Imp. Area
Assumed Impervious Area per Lot =3,463 sf Bldg Pad Area 45 x 75 15 50625
Total Impervious Area from Onsite Lots =131,600 sf Bldg Pad Area 35 x 75 23 60375
Driveways 20 x 20 42 16800
Additional Onsite Impervious Area =83,743 sf Patios 10 x 10 38 3800
Total 131600
Composite Area Area
SCS CN [sf][acres]
98 215,343 4.94 Type Area
74 207,997 4.77 Roadway 57394
70 0 0.00 Sidewalk 19629
100 10,239 0.24 Driveways 6720
98 0 0.00 Total 83743
74 0 0.00
70 0 0.00
100 0 0.00
Total Area =433,579 sf
=9.95 acres
Composite SCS CN =87
% Impervious =49.67%
TIME OF CONCENTRATION
Time of Concentration =5.00 minutes
SCS Lag Time =3.00 minutes
Offsite Pond -
Offsite Impervious -
Offsite Open Assume good condition
Offsite Wooded Assume good condition
Onsite Open Assume good condition
Onsite Wooded Assume good condition
Onsite Pond -
Impervious Area Outside of Right-of-Way (Onsite Lots)
Contributing Area Comments Additional On-Site Imp. Area
Onsite Impervious -
-
POST DEVELOPMENT HYDROLOGIC CALCULATIONS
Comments
-
Assume good condition
Assume good condition
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Subbasin ID:3-To SCM C
SCS CURVE NUMBER
(REF: TR-55 and NRCS Web Soil Survey).
HSG Impervious Open Wooded Pond
A 98 39 30 100
B 98 61 55 100
C 98 74 70 100
D 98 80 77 100
HSG 'A' =0%
HSG 'B' =75%
HSG 'C' =25%
HSG 'D' =0%
Cover Composite
Condition SCS CN
Impervious 98
Open 64
Wooded 59
Pond 100
WATERSHED BREAKDOWN
# of Onsite Lots =148 Type Area No. of Units Imp. Area
Assumed Impervious Area per Lot =3,380 sf Bldg Pad Area 45 x 75 34 116473
Total Impervious Area from Onsite Lots =500,223 sf Bldg Pad Area 35 x 75 114 299250
Driveways 20 x 20 174 69600
Additional Onsite Impervious Area =398,097 sf Patios 10 x 10 147 14900
Total 500223
Composite Area Area
SCS CN [sf][acres]
98 898,320 20.62 Type Area
64 766,589 17.60 Roadway 238794
59 0 0.00 Sidewalk 76552
100 37,331 0.86 Driveways 27840
98 0 0.00 Amenity 54911
64 0 0.00 Total 398097
59 0 0.00
100 0 0.00
Total Area =1,702,240 sf
=39.08 acres
Composite SCS CN =83
% Impervious =52.77%
TIME OF CONCENTRATION
Time of Concentration =5.00 minutes
SCS Lag Time =3.00 minutes
Offsite Pond -
Offsite Impervious -
Offsite Open Assume good condition
Offsite Wooded Assume good condition
Onsite Open Assume good condition
Onsite Wooded Assume good condition
Onsite Pond -
Impervious Area Outside of Right-of-Way (Onsite Lots)
Contributing Area Comments Additional On-Site Imp. Area
Onsite Impervious -
-
POST DEVELOPMENT HYDROLOGIC CALCULATIONS
Comments
-
Assume good condition
Assume good condition
Scenario: Post WQV
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Subsection: Master Network Summary
Catchments Summary
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
5.249187.008,468.0000Post WQVSub-1
31.578186.0046,121.0002Post 2-yearSub-1
72.193186.00124,943.00025Post 25-yearSub-1
5.162186.508,033.0000Post WQVSub-2
27.982186.0040,864.0002Post 2-yearSub-2
62.027186.00107,938.00025Post 25-yearSub-2
9.560187.5018,569.0000Post WQVSub-3
86.251186.50126,844.0002Post 2-yearSub-3
217.360186.00371,541.00025Post 25-yearSub-3
Node Summary
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
0.139363.006,377.0000Post WQVPOA-1
5.456208.0035,814.0002Post 2-yearPOA-1
45.382191.00114,565.00025Post 25-yearPOA-1
0.123363.006,109.0000Post WQVPOA-2
3.992212.5030,296.0002Post 2-yearPOA-2
43.629189.5097,288.00025Post 25-yearPOA-2
0.387362.5015,625.0000Post WQVPOA-3
6.799241.50104,313.0002Post 2-yearPOA-3
96.913194.50348,284.00025Post 25-yearPOA-3
Pond Summary
Maximum
Pond Storage
(ft³)
Maximum
Water
Surface
Elevation
(ft)
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
(N/A)(N/A)5.249187.008,468.0000Post WQVSCM A (IN)
7,219.000536.490.139363.006,377.0000Post WQVSCM A
(OUT)
(N/A)(N/A)31.578186.0046,121.0002Post 2-yearSCM A (IN)
26,748.000537.655.456208.0035,814.0002Post 2-yearSCM A
(OUT)
(N/A)(N/A)72.193186.00124,943.00025Post 25-yearSCM A (IN)
45,088.000538.6445.382191.00114,565.00025Post 25-yearSCM A
(OUT)
(N/A)(N/A)5.162186.508,033.0000Post WQVSCM B (IN)
6,836.000519.600.123363.006,109.0000Post WQVSCM B
(OUT)
(N/A)(N/A)27.982186.0040,864.0002Post 2-yearSCM B (IN)
25,400.000520.973.992212.5030,296.0002Post 2-yearSCM B
(OUT)
(N/A)(N/A)62.027186.00107,938.00025Post 25-yearSCM B (IN)
37,884.000521.8143.629189.5097,288.00025Post 25-yearSCM B
(OUT)
(N/A)(N/A)9.560187.5018,569.0000Post WQVSCM C (IN)
14,924.000513.360.387362.5015,625.0000Post WQVSCM C
(OUT)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Subsection: Master Network Summary
Pond Summary
Maximum
Pond Storage
(ft³)
Maximum
Water
Surface
Elevation
(ft)
Peak Flow
(ft³/s)
Time to Peak
(min)
Hydrograph
Volume
(ft³)
Return
Event
(years)
ScenarioLabel
(N/A)(N/A)86.251186.50126,844.0002Post 2-yearSCM C (IN)
87,002.000514.876.799241.50104,313.0002Post 2-yearSCM C
(OUT)
(N/A)(N/A)217.360186.00371,541.00025Post 25-yearSCM C (IN)
162,455.000516.2996.913194.50348,284.00025Post 25-yearSCM C
(OUT)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
ENCORE AT STREAMSIDE
DWH-19010
DESIGN OF STORMWATER CONTROL
MEASURE A
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Above NP
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
536.00 0.00 13,323
536.50 0.50 15,930 14627 7313 7313 0.50
537.00 1.00 16,743 16337 8168 15482 0.99
538.00 2.00 18,411 17577 17577 33059 1.98
538.50 2.50 19,267 18839 9420 42478 2.49
539.00 3.00 20,136 19702 9851 52329 3.01
539.50 3.50 21,020 20578 10289 62618 3.54
1.101221687 9.653216715
15571.79766
KS = 15572
b =1.1012
y = 15572x1.1012
R² = 0.9999
0
10000
20000
30000
40000
50000
60000
70000
0.00 1.00 2.00 3.00 4.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Main Pool
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - MAIN POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
530.00 -1.00 4,486
531.00 0.00 5,158
532.00 1.00 5,859 5509 5509 5509 1.00
535.00 4.00 8,129 6994 20982 26491 3.95
535.50 4.50 8,531 8330 4165 30656 4.48
536.00 5.00 10,371 9451 4726 35381 5.08
*surface area and volume used for avg. depth calculation
1.146014749 8.61155961
5494.811763
KS = 5495
b =1.1460
Sediment Storage
y = 5494.8x1.146
R² = 0.9997
0
5000
10000
15000
20000
25000
30000
35000
40000
0.00 1.00 2.00 3.00 4.00 5.00 6.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Forebay
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - FOREBAY
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
531.00 -1.00 660
532.00 0.00 887
535.00 3.00 1,754 1321 3962 3962 3.01
535.50 3.50 1,924 1839 920 4881 3.48
536.00 4.00 2,603 2264 1132 6013 4.01
1.44795552 6.689047185
803.5562466
KS = 803.6
b =1.4480
Sediment Storage
y = 803.56x1.448
R² = 0.9983
0
1000
2000
3000
4000
5000
6000
7000
0.00 1.00 2.00 3.00 4.00 5.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Volume Calculation
S. Woodard, PE
01/08/2020
TOTAL VOLUME OF FACILITY
Volume of Main Pool below Normal Pool=35,381 cf
Volume of Forebay below Normal Pool=6,013 cf
Total Volume Below Normal Pool =41,394 cf
Total Volume Above Normal Pool=62,618 cf
Total Volume of Facility =104,012 cf
FOREBAY PERCENTAGE OF PERMANENT POOL VOLUME
approximately 15-20% of the main pool volume.
Total Main Pool Volume =35,381 cf
Provided Forebay Volume =6,013 cf
Provided Forebay Volume % =17%
AVERAGE DEPTH OF MAIN POOL
Main Pool Volume at Normal Pool =35,381 cf
Main Pool Area at Normal Pool =10,371 sf
Average Depth =3.41 ft
Per NCDEQ Minimum Design Criteria, the forebay volume should equal
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Surface Area Calculation
S. Woodard, PE
01/08/2020
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics ==>
11.90 acres
5.58 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond, not just the impervious
surface from on-site development.
Drainage area =11.90 acres @ 46.9%impervious
Estimate the surface area required at pond normal pool elevation ==>
Wet Detention Basins are based on an minimum average depth of =3.41 feet (Calculated)
3.0 3.41 4.0
Lower Boundary =>40.0 1.51 1.24
Site % impervious =>46.9 1.70 1.59 1.43
Upper Boundary =>50.0 1.79 1.51
Therefore, SA/DA required =1.59
Surface area required for main pool at normal pool = 8,234 ft2
=0.19 acres
Surface area provided for main pool at normal pool = 10,371 ft2
Total drainage area to pond =
Total impervious area to pond =
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Calculation
S. Woodard, PE
01/08/2020
DETERMINATION OF WATER QUALITY VOLUME
WQ V = (P)(R V )(A)/12
where,
WQV = water quality volume (in acre-ft)
RV = 0.05+0.009(I) where I is percent impervious cover
A = area in acres
P = rainfall (in inches)
Input data:
Total area, A =11.90 acres
Impervious area =5.58 acres
Percent impervious cover, I =46.9 %
Rainfall, P =1.00 inches
Calculated values:
RV = 0.47
WQV = 0.47 acre-ft
=20383 cf.
ASSOCIATED DEPTH IN POND
WQV = 20383 cf.
Stage / Storage Data:
Ks =15572
b =1.101
Zo =536.00
Volume in 1" rainfall =20383 cf.
Calculated values:
Depth of WQv in Basin =1.28 ft
=15.32 inches
Elevation =537.28 ft
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Drawdown Calculation
S. Woodard, PE
01/08/2020
DRAWDOWN ORIFICE DESIGN
D orifice =2.25 inch
# orifices =1
Ks =15572
b =1.1012
Cd orifice =0.60
Normal Pool Elevation =536.00 feet
Volume @ Normal Pool =0 cf
Orifice Invert =536.00 feet
WSEL @ 1" Runoff Volume =537.28 feet
WSEL Vol. Stored Orifice Flow Avg. Flow Incr. Vol.Incr. Time
(feet)(cf)(cfs)(cfs)(cf)(sec)
537.28 20383 0.144
537.17 18425 0.137 0.141 1958 13900
537.05 16485 0.130 0.134 1939 14505
536.94 14567 0.122 0.126 1919 15214
536.83 12671 0.114 0.118 1896 16061
536.72 10802 0.105 0.109 1870 17101
536.61 8961 0.095 0.100 1840 18424
536.49 7155 0.084 0.089 1806 20192
536.38 5391 0.071 0.078 1765 22748
536.27 3678 0.056 0.063 1712 26987
536.16 2038 0.031 0.044 1640 37630
Drawdown Time =2.35 days
Storm Event: 1 inchLabel: SCM A
Return Event: 0 yearsSubsection: Elevation-Area Volume Curve
Volume (Total)
(ft³)
Volume
(ft³)
A1+A2+sqr
(A1*A2)
(ft²)
Area
(ft²)
Planimeter
(ft²)
Elevation
(ft)
0.0000.0000.0013,323.000.000536.00
7,304.0007,304.00043,821.3015,930.000.000536.50
15,471.0008,167.00049,004.4416,743.000.000537.00
33,041.00017,570.00052,711.2018,411.000.000538.00
42,460.0009,419.00056,512.1419,267.000.000538.50
52,310.0009,850.00059,099.7120,136.000.000539.00
62,598.00010,288.00061,729.2521,020.000.000539.50
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM A
Return Event: 0 yearsSubsection: Outlet Input Data
Requested Pond Water Surface Elevations
ft536.00Minimum (Headwater)
ft0.50Increment (Headwater)
ft539.50Maximum (Headwater)
Outlet Connectivity
E2
(ft)
E1
(ft)
OutfallDirectionOutlet IDStructure Type
539.50537.50CulvertForwardRiserInlet Box
539.50536.00CulvertForwardSiphonOrifice-Circular
539.50531.00TWForwardCulvertCulvert-Circular
539.50538.50TWForwardWeirRectangular Weir
(N/A)(N/A)TailwaterTailwater Settings
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM A
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Culvert
Structure Type: Culvert-Circular
1Number of Barrels
in24.0Diameter
ft50.00Length
ft50.01Length (Computed Barrel)
ft/ft0.020Slope (Computed)
Outlet Control Data
0.013Manning's n
1.00Ke
0.01Kb
0.00Kr
ft0.00Convergence Tolerance
Inlet Control Data
Form 1Equation Form
0.0098K
2.0000M
0.0398C
0.6700Y
0.00T1 ratio (HW/D)
1.29T2 ratio (HW/D)
-1.00Slope Correction Factor
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 & T2...
ft531.00T1 Elevation ft³/s15.550T1 Flow
ft533.57T2 Elevation ft³/s17.772T2 Flow
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM A
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Riser
Structure Type: Inlet Box
1Number of Openings
ft537.50Elevation
ft²16.000Orifice Area
1.00Orifice Coefficient
ft16.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
1.00K Reverse
0.00Manning's n
0.00Kev, Charged Riser
FalseWeir Submergence
FalseOrifice H to crest
Structure ID: Siphon
Structure Type: Orifice-Circular
1Number of Openings
ft536.00Elevation
in2.3Orifice Diameter
1.00Orifice Coefficient
Structure ID: Weir
Structure Type: Rectangular Weir
1Number of Openings
ft538.50Elevation
ft20.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
Structure ID: TW
Structure Type: TW Setup, DS Channel
Free OutfallTailwater Type
Convergence Tolerances
30Maximum Iterations
ft0.01Tailwater Tolerance
(Minimum)
ft0.50Tailwater Tolerance
(Maximum)
ft0.01Headwater Tolerance
(Minimum)
ft0.50Headwater Tolerance
(Maximum)
ft³/s0.001Flow Tolerance (Minimum)
ft³/s10.000Flow Tolerance (Maximum)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM A (IN)
Return Event: 0 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft536.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s5.249Flow (Peak In) min187.00Time to Peak (Flow, In)
ft³/s0.139Flow (Peak Outlet) min363.00Time to Peak (Flow, Outlet)
ft536.49Elevation (Water Surface,
Peak)
ft³7,219.498Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³8,468.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³6,377.000Volume (Total Outlet
Outflow)
ft³1,957.000Volume (Retained)
ft³-133.000Volume (Unrouted)
%1.6Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 2 yearLabel: SCM A (IN)
Return Event: 2 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft536.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s31.578Flow (Peak In) min186.00Time to Peak (Flow, In)
ft³/s5.456Flow (Peak Outlet) min208.00Time to Peak (Flow, Outlet)
ft537.65Elevation (Water Surface,
Peak)
ft³26,748.161Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³46,121.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³35,814.000Volume (Total Outlet
Outflow)
ft³10,254.000Volume (Retained)
ft³-52.000Volume (Unrouted)
%0.1Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 25 yearLabel: SCM A (IN)
Return Event: 25 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft536.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s72.193Flow (Peak In) min186.00Time to Peak (Flow, In)
ft³/s45.382Flow (Peak Outlet) min191.00Time to Peak (Flow, Outlet)
ft538.64Elevation (Water Surface,
Peak)
ft³45,088.230Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³124,943.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³114,565.000Volume (Total Outlet
Outflow)
ft³10,325.000Volume (Retained)
ft³-53.000Volume (Unrouted)
%0.0Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Facility ID:SCM A
INPUT DATA
Inside Length =4.00 ft
Inside Width =4.00 ft
Wall Thickness =6.00 in
Standard Base Length =5.00 ft
Standard Base Width =5.00 ft
Standard Base Thickness =6.00 in
Inside Height of Riser =6.50 ft
Concrete Unit Weight =142.00 pcf Unit weight of manhole concrete is 142 pcf per NC Products
Outside Diameter of Barrel =30.00 in
Drain Pipe (if present) =6.00 in
TRASH RACK DISPLACEMENT
Bottom Length / Width =7.00 ft Calculation for truncated square pyramid
Top Length / Width =1.00 ft
Height =2.00 ft
Trash Rack Displacement =38.000 cf
CONCRETE PRESENT IN RISER STRUCTURE
Riser Walls =58.500 cf
Standard Base of Riser =12.500 cf
Less Opening for Barrel =2.454 cf
Less Opening for Drain Pipe =0.098 cf
Total Concrete Less Openings =68.447 cf
Weight of Concrete =9,720 lbs
AMOUNT OF WATER DISPLACED BY RISER STRUCTURE
Displacement by Concrete =68.447 cf
Displacement by Open Air =104.000 cf
Displacement by Trash Rack =38.000 cf
Total Water Displaced =210.447 cf
Weight of Water Displaced =13,132 lbs
RISER ANTI-FLOTATION CALCULATION
AMOUNT OF CONCRETE TO ADD TO RISER STRUCTURE
Safety Factor =1.15 Recommend 1.15 or higher
Add'l Weight for Bouyancy =5,382 lbs
Bouyant Weight of Concrete =79.60 pcf
Bouyant Weight w/ SF =69.22 pcf
Add'l Concrete to Add =77.757 cf
Less Standard Base =12.500 cf
New Base Design Required =90.257 cf
ANTI FLOTATION BLOCK DESIGN CALCULATIONS
AF Block Length =8.00 ft
AF Block Width =8.00 ft
AF Block Thickness =20.00 in
AF Block Provided =106.667 cf
Total Concrete Present =162.614 cf
Total Concrete Present =23,091 lbs
Project Name: Encore at Streamside Date: 12/11/2020
Project Number: DWH-19010 Calculated By: S. Woodard, PE
Facility ID: SCM A
DESIGN OF RIPRAP OUTLET PROTECTION
Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual.
Flow, Q10-yr =33.00 cfs
Slope =2.04 %
Pipe Diameter, Do =24 in
=2.00 feet
Number of pipes =1
Pipe separation =0.00 feet
Manning's n =0.013
Zone from graph above =2
Outlet pipe diameter =24 in Length =12.00 ft
Outlet flowrate =33.00 cfs Width =6.00 ft
Outlet velocity =11.74 ft/sec Stone diameter =6.00 in
Material =Class B Thickness =22.00 in
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x Do 3 x Do
2 Class B 6 22 6 x Do 3 x Do
3 Class I 13 22 8 x Do 3 x Do
4 Class I 13 22 8 x Do 3 x Do
5 Class II 23 27 10 x Do 3 x Do
6 Class II 23 27 10 x Do 3 x Do
7 Study Required
RIPRAP OUTLET PROTECTION
11.74 ft/sec
0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9 10Velocity (ft/sec)Pipe diameter (ft)
Figure 8.06.b.1
Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6 Zone 7
ENCORE AT STREAMSIDE
DWH-19010
DESIGN OF STORMWATER CONTROL
MEASURE B
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Above NP
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
519.00 0.00 10,239
519.50 0.50 12,388 11314 5657 5657 0.51
520.00 1.00 13,063 12726 6363 12020 1.00
520.50 1.50 13,753 13408 6704 18724 1.48
521.00 2.00 14,456 14105 7052 25776 1.98
522.00 3.00 15,906 15181 15181 40957 2.99
523.00 4.00 17,412 16659 16659 57616 4.07
1.11366035 9.398757542
12073.37075
KS = 12073
b =1.1137
y = 12073x1.1137
R² = 0.9997
0
10000
20000
30000
40000
50000
60000
70000
0.00 1.00 2.00 3.00 4.00 5.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Main Pool
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - MAIN POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
513.00 -1.00 3,031
514.00 0.00 3,528
516.00 2.00 4,622 4075 8150 8150 2.01
518.00 4.00 5,844 5233 10466 18616 3.96
518.50 4.50 6,171 6008 3004 21620 4.48
519.00 5.00 7,628 6900 3450 25070 5.06
*surface area and volume used for avg. depth calculation
1.214609062 8.160226809
3498.980115
KS = 3499
b =1.2146
Sediment Storage
y = 3499x1.2146
R² = 0.9995
0
5000
10000
15000
20000
25000
30000
0.00 1.00 2.00 3.00 4.00 5.00 6.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Forebay
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - FOREBAY
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
514.00 -1.00 490
515.00 0.00 696
518.00 3.00 1,485 1091 3272 3272 3.01
518.50 3.50 1,641 1563 782 4053 3.48
519.00 4.00 2,248 1945 972 5025 4.02
1.489399615 6.451854431
633.876684
KS = 633.9
b =1.4894
Sediment Storage
y = 633.88x1.4894
R² = 0.9982
0
1000
2000
3000
4000
5000
6000
0.00 1.00 2.00 3.00 4.00 5.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Volume Calculation
S. Woodard, PE
01/08/2020
TOTAL VOLUME OF FACILITY
Volume of Main Pool below Normal Pool=25,070 cf
Volume of Forebay below Normal Pool=5,025 cf
Total Volume Below Normal Pool =30,095 cf
Total Volume Above Normal Pool=57,616 cf
Total Volume of Facility =87,711 cf
FOREBAY PERCENTAGE OF PERMANENT POOL VOLUME
approximately 15-20% of the main pool volume.
Total Main Pool Volume =25,070 cf
Provided Forebay Volume =5,025 cf
Provided Forebay Volume % =20%
AVERAGE DEPTH OF MAIN POOL
Main Pool Volume at Normal Pool =25,070 cf
Main Pool Area at Normal Pool =7,628 sf
Average Depth =3.29 ft
Per NCDEQ Minimum Design Criteria, the forebay volume should equal
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Surface Area Calculation
S. Woodard, PE
01/08/2020
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics ==>
9.95 acres
4.94 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond, not just the impervious
surface from on-site development.
Drainage area =9.95 acres @ 49.7%impervious
Estimate the surface area required at pond normal pool elevation ==>
Wet Detention Basins are based on an minimum average depth of =3.29 feet (Calculated)
3.0 3.29 4.0
Lower Boundary =>40.0 1.51 1.24
Site % impervious =>49.7 1.78 1.70 1.50
Upper Boundary =>50.0 1.79 1.51
Therefore, SA/DA required =1.70
Surface area required for main pool at normal pool = 7,373 ft2
=0.17 acres
Surface area provided for main pool at normal pool = 7,628 ft2
Total drainage area to pond =
Total impervious area to pond =
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Calculation
S. Woodard, PE
01/08/2020
DETERMINATION OF WATER QUALITY VOLUME
WQ V = (P)(R V )(A)/12
where,
WQV = water quality volume (in acre-ft)
RV = 0.05+0.009(I) where I is percent impervious cover
A = area in acres
P = rainfall (in inches)
Input data:
Total area, A =9.95 acres
Impervious area =4.94 acres
Percent impervious cover, I =49.7 %
Rainfall, P =1.00 inches
Calculated values:
RV = 0.50
WQV = 0.41 acre-ft
=17957 cf.
ASSOCIATED DEPTH IN POND
WQV = 17957 cf.
Stage / Storage Data:
Ks =12073
b =1.114
Zo =519.00
Volume in 1" rainfall =17957 cf.
Calculated values:
Depth of WQv in Basin =1.43 ft
=17.14 inches
Elevation =520.43 ft
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Drawdown Calculation
S. Woodard, PE
01/08/2020
DRAWDOWN ORIFICE DESIGN
D orifice =2 inch
# orifices =1
Ks =12073
b =1.1137
Cd orifice =0.60
Normal Pool Elevation =519.00 feet
Volume @ Normal Pool =0 cf
Orifice Invert =519.00 feet
WSEL @ 1" Runoff Volume =520.43 feet
WSEL Vol. Stored Orifice Flow Avg. Flow Incr. Vol.Incr. Time
(feet)(cf)(cfs)(cfs)(cf)(sec)
520.43 17957 0.122
520.30 16219 0.116 0.119 1738 14636
520.18 14500 0.110 0.113 1719 15239
520.05 12802 0.103 0.107 1699 15941
519.93 11126 0.096 0.100 1676 16775
519.80 9476 0.089 0.093 1650 17791
519.68 7854 0.081 0.085 1621 19069
519.55 6266 0.072 0.077 1588 20752
519.43 4719 0.062 0.067 1547 23130
519.31 3222 0.049 0.056 1497 26917
519.18 1796 0.033 0.041 1427 34737
Drawdown Time =2.37 days
Storm Event: 1 inchLabel: SCM B
Return Event: 0 yearsSubsection: Elevation-Area Volume Curve
Volume (Total)
(ft³)
Volume
(ft³)
A1+A2+sqr
(A1*A2)
(ft²)
Area
(ft²)
Planimeter
(ft²)
Elevation
(ft)
0.0000.0000.0010,239.000.000519.00
5,648.0005,648.00033,889.3612,388.000.000519.50
12,010.0006,362.00038,172.0213,063.000.000520.00
18,713.0006,703.00040,219.5613,753.000.000520.50
25,765.0007,052.00042,309.1214,456.000.000521.00
40,940.00015,175.00045,525.6815,906.000.000522.00
57,594.00016,653.00049,959.9717,412.000.000523.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM B
Return Event: 0 yearsSubsection: Outlet Input Data
Requested Pond Water Surface Elevations
ft519.00Minimum (Headwater)
ft0.50Increment (Headwater)
ft523.00Maximum (Headwater)
Outlet Connectivity
E2
(ft)
E1
(ft)
OutfallDirectionOutlet IDStructure Type
523.00520.80CulvertForwardRiserInlet Box
523.00519.00CulvertForwardSiphonOrifice-Circular
523.00514.00TWForwardCulvertCulvert-Circular
523.00521.60TWForwardWeirRectangular Weir
(N/A)(N/A)TailwaterTailwater Settings
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM B
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Culvert
Structure Type: Culvert-Circular
1Number of Barrels
in24.0Diameter
ft100.00Length
ft100.00Length (Computed Barrel)
ft/ft0.010Slope (Computed)
Outlet Control Data
0.013Manning's n
1.00Ke
0.01Kb
0.00Kr
ft0.00Convergence Tolerance
Inlet Control Data
Form 1Equation Form
0.0098K
2.0000M
0.0398C
0.6700Y
1.15T1 ratio (HW/D)
1.30T2 ratio (HW/D)
-1.00Slope Correction Factor
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 & T2...
ft516.30T1 Elevation ft³/s15.550T1 Flow
ft516.59T2 Elevation ft³/s17.772T2 Flow
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM B
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Riser
Structure Type: Inlet Box
1Number of Openings
ft520.80Elevation
ft²16.000Orifice Area
1.00Orifice Coefficient
ft16.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
1.00K Reverse
0.00Manning's n
0.00Kev, Charged Riser
FalseWeir Submergence
FalseOrifice H to crest
Structure ID: Siphon
Structure Type: Orifice-Circular
1Number of Openings
ft519.00Elevation
in2.0Orifice Diameter
1.00Orifice Coefficient
Structure ID: Weir
Structure Type: Rectangular Weir
1Number of Openings
ft521.60Elevation
ft20.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
Structure ID: TW
Structure Type: TW Setup, DS Channel
Free OutfallTailwater Type
Convergence Tolerances
30Maximum Iterations
ft0.01Tailwater Tolerance
(Minimum)
ft0.50Tailwater Tolerance
(Maximum)
ft0.01Headwater Tolerance
(Minimum)
ft0.50Headwater Tolerance
(Maximum)
ft³/s0.001Flow Tolerance (Minimum)
ft³/s10.000Flow Tolerance (Maximum)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM B (IN)
Return Event: 0 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft519.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s5.162Flow (Peak In) min186.50Time to Peak (Flow, In)
ft³/s0.123Flow (Peak Outlet) min363.00Time to Peak (Flow, Outlet)
ft519.60Elevation (Water Surface,
Peak)
ft³6,835.748Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³8,033.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³6,109.000Volume (Total Outlet
Outflow)
ft³1,802.000Volume (Retained)
ft³-121.000Volume (Unrouted)
%1.5Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 2 yearLabel: SCM B (IN)
Return Event: 2 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft519.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s27.982Flow (Peak In) min186.00Time to Peak (Flow, In)
ft³/s3.992Flow (Peak Outlet) min212.50Time to Peak (Flow, Outlet)
ft520.97Elevation (Water Surface,
Peak)
ft³25,400.262Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³40,864.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³30,296.000Volume (Total Outlet
Outflow)
ft³10,534.000Volume (Retained)
ft³-34.000Volume (Unrouted)
%0.1Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 25 yearLabel: SCM B (IN)
Return Event: 25 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft519.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s62.027Flow (Peak In) min186.00Time to Peak (Flow, In)
ft³/s43.629Flow (Peak Outlet) min189.50Time to Peak (Flow, Outlet)
ft521.81Elevation (Water Surface,
Peak)
ft³37,884.337Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³107,938.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³97,288.000Volume (Total Outlet
Outflow)
ft³10,617.000Volume (Retained)
ft³-33.000Volume (Unrouted)
%0.0Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Facility ID:SCM A
INPUT DATA
Inside Length =4.00 ft
Inside Width =4.00 ft
Wall Thickness =6.00 in
Standard Base Length =5.00 ft
Standard Base Width =5.00 ft
Standard Base Thickness =6.00 in
Inside Height of Riser =6.80 ft
Concrete Unit Weight =142.00 pcf Unit weight of manhole concrete is 142 pcf per NC Products
Outside Diameter of Barrel =30.00 in
Drain Pipe (if present) =6.00 in
TRASH RACK DISPLACEMENT
Bottom Length / Width =7.00 ft Calculation for truncated square pyramid
Top Length / Width =1.00 ft
Height =2.00 ft
Trash Rack Displacement =38.000 cf
CONCRETE PRESENT IN RISER STRUCTURE
Riser Walls =61.200 cf
Standard Base of Riser =12.500 cf
Less Opening for Barrel =2.454 cf
Less Opening for Drain Pipe =0.098 cf
Total Concrete Less Openings =71.147 cf
Weight of Concrete =10,103 lbs
AMOUNT OF WATER DISPLACED BY RISER STRUCTURE
Displacement by Concrete =71.147 cf
Displacement by Open Air =108.800 cf
Displacement by Trash Rack =38.000 cf
Total Water Displaced =217.947 cf
Weight of Water Displaced =13,600 lbs
RISER ANTI-FLOTATION CALCULATION
AMOUNT OF CONCRETE TO ADD TO RISER STRUCTURE
Safety Factor =1.15 Recommend 1.15 or higher
Add'l Weight for Bouyancy =5,537 lbs
Bouyant Weight of Concrete =79.60 pcf
Bouyant Weight w/ SF =69.22 pcf
Add'l Concrete to Add =79.994 cf
Less Standard Base =12.500 cf
New Base Design Required =92.494 cf
ANTI FLOTATION BLOCK DESIGN CALCULATIONS
AF Block Length =8.00 ft
AF Block Width =8.00 ft
AF Block Thickness =20.00 in
AF Block Provided =106.667 cf
Total Concrete Present =165.314 cf
Total Concrete Present =23,475 lbs
Project Name: Encore at Streamside Date: 12/11/2020
Project Number: DWH-19010 Calculated By: S. Woodard, PE
Facility ID: SCM B
DESIGN OF RIPRAP OUTLET PROTECTION
Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual.
Flow, Q10-yr =31.68 cfs
Slope =1.00 %
Pipe Diameter, Do =24 in
=2.00 feet
Number of pipes =1
Pipe separation =0.00 feet
Manning's n =0.013
Zone from graph above =2
Outlet pipe diameter =24 in Length =12.00 ft
Outlet flowrate =31.68 cfs Width =6.00 ft
Outlet velocity =7.97 ft/sec Stone diameter =6.00 in
Material =Class B Thickness =22.00 in
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x Do 3 x Do
2 Class B 6 22 6 x Do 3 x Do
3 Class I 13 22 8 x Do 3 x Do
4 Class I 13 22 8 x Do 3 x Do
5 Class II 23 27 10 x Do 3 x Do
6 Class II 23 27 10 x Do 3 x Do
7 Study Required
RIPRAP OUTLET PROTECTION
7.97 ft/sec
0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9 10Velocity (ft/sec)Pipe diameter (ft)
Figure 8.06.b.1
Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6 Zone 7
ENCORE AT STREAMSIDE
DWH-19010
DESIGN OF STORMWATER CONTROL
MEASURE C
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Above NP
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
513.00 0.00 39,924
513.50 0.50 45,608 42766 21383 21383 0.50
514.00 1.00 47,344 46476 23238 44621 1.00
515.00 2.00 50,858 49101 49101 93722 1.98
516.00 3.00 54,428 52643 52643 146365 2.99
516.50 3.50 56,234 55331 27666 174031 3.51
517.00 4.00 58,055 57145 28572 202603 4.04
1.080082191 10.71120938
44855.85395
KS = 44856
b =1.0801
y = 44856x1.0801
R² = 0.9999
0
50000
100000
150000
200000
250000
0.00 1.00 2.00 3.00 4.00 5.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Main Pool
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - MAIN POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
507.00 -1.00 17,303
508.00 0.00 18,926
509.00 1.00 20,580 19753 19753 19753 1.00
512.00 4.00 25,734 23157 69471 89224 3.96
512.50 4.50 26,668 26201 13101 102325 4.49
513.00 5.00 30,584 28626 14313 116638 5.06
*surface area and volume used for avg. depth calculation
1.096781818 9.889346774
19719.17465
KS = 19719
b =1.0968
Sediment Storage
y = 19719x1.0968
R² = 0.9999
0
20000
40000
60000
80000
100000
120000
140000
0.00 1.00 2.00 3.00 4.00 5.00 6.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
SSFxn Forebay
S. Woodard, PE
01/08/2020
STAGE-STORAGE FUNCTION - FOREBAY
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
508.00 -1.00 3,288
509.00 0.00 3,953
512.00 3.00 6,294 5124 15371 15371 3.01
512.50 3.50 6,734 6514 3257 18628 3.48
513.00 4.00 8,520 7627 3814 22441 4.01
1.313721972 8.193661949
3617.946756
KS = 3617.9
b =1.3137
Sediment Storage
y = 3617.9x1.3137
R² = 0.999
0
5000
10000
15000
20000
25000
0.00 1.00 2.00 3.00 4.00 5.00Storage (CF)Stage (feet)
Storage vs. Stage
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Volume Calculation
S. Woodard, PE
01/08/2020
TOTAL VOLUME OF FACILITY
Volume of Main Pool below Normal Pool=116,638 cf
Volume of Forebay below Normal Pool=22,441 cf
Total Volume Below Normal Pool =139,079 cf
Total Volume Above Normal Pool=202,603 cf
Total Volume of Facility =341,681 cf
FOREBAY PERCENTAGE OF PERMANENT POOL VOLUME
approximately 15-20% of the main pool volume.
Total Main Pool Volume =116,638 cf
Provided Forebay Volume =22,441 cf
Provided Forebay Volume % =19%
AVERAGE DEPTH OF MAIN POOL
Main Pool Volume at Normal Pool =116,638 cf
Main Pool Area at Normal Pool =30,584 sf
Average Depth =3.81 ft
Per NCDEQ Minimum Design Criteria, the forebay volume should equal
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
Surface Area Calculation
S. Woodard, PE
01/08/2020
WET DETENTION BASIN SUMMARY
Enter the drainage area characteristics ==>
39.08 acres
20.62 acres
Note The basin must be sized to treat all impervious surface runoff draining into the pond, not just the impervious
surface from on-site development.
Drainage area =39.08 acres @ 52.8%impervious
Estimate the surface area required at pond normal pool elevation ==>
Wet Detention Basins are based on an minimum average depth of =3.81 feet (Calculated)
3.0 3.81 4.0
Lower Boundary =>50.0 1.79 1.51
Site % impervious =>52.8 1.87 1.64 1.58
Upper Boundary =>60.0 2.09 1.77
Therefore, SA/DA required =1.64
Surface area required for main pool at normal pool = 27,854 ft2
=0.64 acres
Surface area provided for main pool at normal pool = 30,584 ft2
Total drainage area to pond =
Total impervious area to pond =
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Calculation
S. Woodard, PE
01/08/2020
DETERMINATION OF WATER QUALITY VOLUME
WQ V = (P)(R V )(A)/12
where,
WQV = water quality volume (in acre-ft)
RV = 0.05+0.009(I) where I is percent impervious cover
A = area in acres
P = rainfall (in inches)
Input data:
Total area, A =39.08 acres
Impervious area =20.62 acres
Percent impervious cover, I =52.8 %
Rainfall, P =1.00 inches
Calculated values:
RV = 0.52
WQV = 1.71 acre-ft
=74467 cf.
ASSOCIATED DEPTH IN POND
WQV = 74467 cf.
Stage / Storage Data:
Ks =44856
b =1.080
Zo =513.00
Volume in 1" rainfall =74467 cf.
Calculated values:
Depth of WQv in Basin =1.60 ft
=19.19 inches
Elevation =514.60 ft
Encore at Streamside
DWH-19010
STORMWATER CONTROL MEASURE
WQV Drawdown Calculation
S. Woodard, PE
01/08/2020
DRAWDOWN ORIFICE DESIGN
D orifice =4.75 inch
# orifices =1
Ks =44856
b =1.0801
Cd orifice =0.60
Normal Pool Elevation =513.00 feet
Volume @ Normal Pool =0 cf
Orifice Invert =513.00 feet
WSEL @ 1" Runoff Volume =514.60 feet
WSEL Vol. Stored Orifice Flow Avg. Flow Incr. Vol.Incr. Time
(feet)(cf)(cfs)(cfs)(cf)(sec)
514.60 74467 0.700
514.46 67403 0.664 0.682 7063 10354
514.32 60395 0.626 0.645 7009 10867
514.18 53446 0.585 0.605 6949 11477
514.04 46564 0.541 0.563 6882 12220
513.89 39756 0.494 0.517 6807 13155
513.75 33034 0.441 0.467 6722 14385
513.61 26413 0.381 0.411 6621 16114
513.47 19914 0.309 0.345 6499 18830
513.33 13571 0.202 0.255 6343 24830
513.19 7447 0.088 0.145 6124 42368
Drawdown Time =2.02 days
Storm Event: 1 inchLabel: SCM C
Return Event: 0 yearsSubsection: Elevation-Area Volume Curve
Volume (Total)
(ft³)
Volume
(ft³)
A1+A2+sqr
(A1*A2)
(ft²)
Area
(ft²)
Planimeter
(ft²)
Elevation
(ft)
0.0000.0000.0039,924.000.000513.00
21,367.00021,367.000128,203.4645,608.000.000513.50
44,604.00023,237.000139,419.8947,344.000.000514.00
93,694.00049,091.000147,271.5550,858.000.000515.00
146,327.00052,633.000157,898.7354,428.000.000516.00
173,992.00027,664.000165,985.6356,234.000.000516.50
202,563.00028,571.000171,426.2558,055.000.000517.00
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM C
Return Event: 0 yearsSubsection: Outlet Input Data
Requested Pond Water Surface Elevations
ft513.00Minimum (Headwater)
ft0.50Increment (Headwater)
ft517.00Maximum (Headwater)
Outlet Connectivity
E2
(ft)
E1
(ft)
OutfallDirectionOutlet IDStructure Type
517.00514.70CulvertForwardRiserInlet Box
517.00513.00CulvertForwardSiphonOrifice-Circular
517.00511.00TWForwardCulvertCulvert-Circular
517.00516.00TWForwardWeirRectangular Weir
(N/A)(N/A)TailwaterTailwater Settings
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM C
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Culvert
Structure Type: Culvert-Circular
1Number of Barrels
in36.0Diameter
ft50.00Length
ft50.01Length (Computed Barrel)
ft/ft0.020Slope (Computed)
Outlet Control Data
0.013Manning's n
1.00Ke
0.01Kb
0.00Kr
ft0.00Convergence Tolerance
Inlet Control Data
Form 1Equation Form
0.0098K
2.0000M
0.0398C
0.6700Y
1.14T1 ratio (HW/D)
1.29T2 ratio (HW/D)
-1.00Slope Correction Factor
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 & T2...
ft514.42T1 Elevation ft³/s42.851T1 Flow
ft514.86T2 Elevation ft³/s48.973T2 Flow
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM C
Return Event: 0 yearsSubsection: Outlet Input Data
Structure ID: Riser
Structure Type: Inlet Box
1Number of Openings
ft514.70Elevation
ft²25.000Orifice Area
1.00Orifice Coefficient
ft20.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
1.00K Reverse
0.00Manning's n
0.00Kev, Charged Riser
FalseWeir Submergence
FalseOrifice H to crest
Structure ID: Siphon
Structure Type: Orifice-Circular
1Number of Openings
ft513.00Elevation
in4.8Orifice Diameter
1.00Orifice Coefficient
Structure ID: Weir
Structure Type: Rectangular Weir
1Number of Openings
ft516.00Elevation
ft60.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
Structure ID: TW
Structure Type: TW Setup, DS Channel
Free OutfallTailwater Type
Convergence Tolerances
30Maximum Iterations
ft0.01Tailwater Tolerance
(Minimum)
ft0.50Tailwater Tolerance
(Maximum)
ft0.01Headwater Tolerance
(Minimum)
ft0.50Headwater Tolerance
(Maximum)
ft³/s0.001Flow Tolerance (Minimum)
ft³/s10.000Flow Tolerance (Maximum)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 1 inchLabel: SCM C (IN)
Return Event: 0 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft513.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s9.560Flow (Peak In) min187.50Time to Peak (Flow, In)
ft³/s0.387Flow (Peak Outlet) min362.50Time to Peak (Flow, Outlet)
ft513.36Elevation (Water Surface,
Peak)
ft³14,923.711Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³18,569.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³15,625.000Volume (Total Outlet
Outflow)
ft³2,774.000Volume (Retained)
ft³-170.000Volume (Unrouted)
%0.9Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 2 yearLabel: SCM C (IN)
Return Event: 2 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft513.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s86.251Flow (Peak In) min186.50Time to Peak (Flow, In)
ft³/s6.799Flow (Peak Outlet) min241.50Time to Peak (Flow, Outlet)
ft514.87Elevation (Water Surface,
Peak)
ft³87,001.853Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³126,844.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³104,313.000Volume (Total Outlet
Outflow)
ft³22,494.000Volume (Retained)
ft³-37.000Volume (Unrouted)
%0.0Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Storm Event: 25 yearLabel: SCM C (IN)
Return Event: 25 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft513.00Elevation (Water Surface,
Initial)
ft³0.000Volume (Initial)
ft³/s0.000Flow (Initial Outlet)
ft³/s0.000Flow (Initial Infiltration)
ft³/s0.000Flow (Initial, Total)
min0.50Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s217.360Flow (Peak In) min186.00Time to Peak (Flow, In)
ft³/s96.913Flow (Peak Outlet) min194.50Time to Peak (Flow, Outlet)
ft516.29Elevation (Water Surface,
Peak)
ft³162,455.401Volume (Peak)
Mass Balance (ft³)
ft³0.000Volume (Initial)
ft³371,541.000Volume (Total Inflow)
ft³0.000Volume (Total Infiltration)
ft³348,284.000Volume (Total Outlet
Outflow)
ft³23,207.000Volume (Retained)
ft³-49.000Volume (Unrouted)
%0.0Error (Mass Balance)
12/11/2020DWH-19010.ppc
J. Mattingly, EIBelshire Subdivision
Project Name:Encore at Streamside Date:12/11/2020
Project Number:DWH-19010 Calculated By:S. Woodard, PE
Facility ID:SCM C
INPUT DATA
Inside Length =5.00 ft
Inside Width =5.00 ft
Wall Thickness =6.00 in
Standard Base Length =6.00 ft
Standard Base Width =6.00 ft
Standard Base Thickness =6.00 in
Inside Height of Riser =3.70 ft
Concrete Unit Weight =142.00 pcf Unit weight of manhole concrete is 142 pcf per NC Products
Outside Diameter of Barrel =36.00 in
Drain Pipe (if present) =6.00 in
TRASH RACK DISPLACEMENT
Bottom Length / Width =8.00 ft Calculation for truncated square pyramid
Top Length / Width =1.00 ft
Height =2.00 ft
Trash Rack Displacement =48.667 cf
CONCRETE PRESENT IN RISER STRUCTURE
Riser Walls =40.700 cf
Standard Base of Riser =18.000 cf
Less Opening for Barrel =3.534 cf
Less Opening for Drain Pipe =0.098 cf
Total Concrete Less Openings =55.068 cf
Weight of Concrete =7,820 lbs
AMOUNT OF WATER DISPLACED BY RISER STRUCTURE
Displacement by Concrete =55.068 cf
Displacement by Open Air =92.500 cf
Displacement by Trash Rack =48.667 cf
Total Water Displaced =196.234 cf
Weight of Water Displaced =12,245 lbs
RISER ANTI-FLOTATION CALCULATION
AMOUNT OF CONCRETE TO ADD TO RISER STRUCTURE
Safety Factor =1.15 Recommend 1.15 or higher
Add'l Weight for Bouyancy =6,262 lbs
Bouyant Weight of Concrete =79.60 pcf
Bouyant Weight w/ SF =69.22 pcf
Add'l Concrete to Add =90.471 cf
Less Standard Base =18.000 cf
New Base Design Required =108.471 cf
ANTI FLOTATION BLOCK DESIGN CALCULATIONS
AF Block Length =8.00 ft
AF Block Width =8.00 ft
AF Block Thickness =22.00 in
AF Block Provided =117.333 cf
Total Concrete Present =154.401 cf
Total Concrete Present =21,925 lbs
Project Name: Encore at Streamside Date: 12/11/2020
Project Number: DWH-19010 Calculated By: S. Woodard, PE
Facility ID: SCM C
DESIGN OF RIPRAP OUTLET PROTECTION
Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual.
Flow, Q10-yr =52.34 cfs
Slope =2.00 %
Pipe Diameter, Do =36 in
=3.00 feet
Number of pipes =1
Pipe separation =0.00 feet
Manning's n =0.013
Zone from graph above =3
Outlet pipe diameter =36 in Length =24.00 ft
Outlet flowrate =52.34 cfs Width =9.00 ft
Outlet velocity =13.72 ft/sec Stone diameter =13.00 in
Material =Class I Thickness =22.00 in
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x Do 3 x Do
2 Class B 6 22 6 x Do 3 x Do
3 Class I 13 22 8 x Do 3 x Do
4 Class I 13 22 8 x Do 3 x Do
5 Class II 23 27 10 x Do 3 x Do
6 Class II 23 27 10 x Do 3 x Do
7 Study Required
RIPRAP OUTLET PROTECTION
13.72 ft/sec
0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9 10Velocity (ft/sec)Pipe diameter (ft)
Figure 8.06.b.1
Zone 1
Zone 2
Zone 3
Zone 4
Zone 5
Zone 6 Zone 7