Villas at Murrayville Fitness Center State Stormwater CalculationsShipman Shipman Shipman Shipman Engineering, PLLCEngineering, PLLCEngineering, PLLCEngineering, PLLC
137 Middlegreen Place
Holly Springs, NC 27540
(919) 900-0006 zak@shipmanengineering.com
NCBELS License P-1963
Stormwater Drainage & Erosion
Control Calculations
The Villas at Murrayville Fitness Center
Addition
Cape Fear Township
New Hanover County, North Carolina
February 11, 2020
Prepared for:
Hawthorne Residential Partners
806 Green Valley Road, Suite 311
Greensboro, NC 27408
Shipman Shipman Shipman Shipman Engineering, PLLCEngineering, PLLCEngineering, PLLCEngineering, PLLC
137 Middlegreen Place
Holly Springs, NC 27540
(919) 900-0006 zak@shipmanengineering.com
NCBELS License P-1963
Shipman Shipman Shipman Shipman Engineering, PLLCEngineering, PLLCEngineering, PLLCEngineering, PLLC
137 Middlegreen Place
Holly Springs, NC 27540
(919) 900-0006 zak@shipmanengineering.com
NCBELS License P-1963
Table of Contents
Support Documents
· Stormwater Management Narrative
· Erosion Control Narrative
· USGS Quad Sheet Exhibits
· NRCS Soils Map Exhibit
· NOAA Intensity Duration Frequency Precipitation Data
· NOAA Depth Duration Frequency Precipitation Data
· FEMA Flood Mapping Exhibit
Calculations
· Wet Detention Pond Modification Calculations
· Weighted Curve Number Modification Calculations-Post
Development
Shipman Engineering, PLLC Shipman Engineering, PLLC Shipman Engineering, PLLC Shipman Engineering, PLLC
Shipman Engineering, PLLC 919.900.0006
137 Middlegreen Place zak@shipmanengineering.com
Holly Springs, NC 27540 NCBELS License P-1963
The Villas at Murrayville Fitness Center Addition
Stormwater Management Design Narrative
Project Overview
The Villas at Murrayville is an existing apartment facility with 204 residential apartment units located
near the intersection of North College Road and Murrayville Road in New Hanover County. The property
is approximately 20.60 acres and was constructed in several phases between 2006 and 2015. The
property Owner wishes to construct a new Fitness Center amenity facility located between Buildings 1
and 9 on the western boundary of the site. The new Fitness Center will be approximately 1,195 square
feet in area as shown on the drawings. We are proposing a modification to the existing stormwater
management permit, issued in April, 2015. The existing permit is SW8 060717 and is valid until October
2020.
Stormwater Design Overview
The site drains to a single existing wet detention basin located on the southern tip of the property
adjacent to the I-40 right-of-way. The drainage area includes the entire property area plus area
associated with a single outparcel located immediately north of the property. The property is located in
the Smith Creek watershed (C,SW classification). The existing Wet Detention basin was constructed in
2006 and was originally permitted for 331,818 square feet of BUA on October 26, 2006. A previous
permit modification was issued in April 2015 to increase the allowable BUA to 338,953 square feet (for
construction associated with the permitted outparcel).
The proposed permit modification will increase the allowable BUA to 340,202 square feet to account for
the proposed Fitness Center and associated sidewalk and other site improvements. Note that we are
relocating an existing dumpster pad and removing some existing asphalt parking as shown on the
drawings to make room for the new facility. The net increase in impervious area is proposed to be 1,249
square feet.
The existing wet detention pond should have adequate surface area and volume capacity to
accommodate the increase in BUA. Based on a review of the NCDEQ file, our calculations yield the
following results:
Existing Approved BUA: 338,953 sf
Proposed BUA : 340,202 sf (net increase of 1,249 sf)
Required Water Quality Volume: 29,253 cf
Provided Water Quality Volume: 152,310 cf
Required Surface Area for 90% TSS: 9,309 sf
Provided Surface area: 32,519 sf
Calculated Drawdown Time: 2.65 days with existing 3” orifice
From these results, we observe that the pond has plenty of capacity to incorporate the proposed BUA
into the site.
Additionally, the pond must meet pre/post peak flow attenuation requirements per New Hanover
County regulations. To evaluate this, we used the NRCS Curve Number Method and evaluated the
original post-development CN in comparison to the modified post-development CN. The results
indicate that the original post-development curve number (utilizing the original BUA levels) for Good
Condition is 67. The modified post-development curve number (utilizing the modified BUA levels) is also
67.
Since the curve numbers remain the same, we conclude that pond inflows remain mathematically the
same and so therefore the pre/post development flow routings should remain consistent with the
original design discharge limits.
Since the pond has capacity to absorb the new 1,249 square feet of BUA both from a Water Quality and
peak flow perspective, we conclude that no outlet structure modifications are required as a result of this
project.
Shipman Engineering, PLLC Shipman Engineering, PLLC Shipman Engineering, PLLC Shipman Engineering, PLLC
Shipman Engineering, PLLC 919.900.0006
137 Middlegreen Place zak@shipmanengineering.com
Holly Springs, NC 27540 NCBELS License P-1963
The Villas at Murrayville Fitness Center Addition
Erosion Control Design Narrative
Project Overview
The Villas at Murrayville is an existing apartment facility with 204 residential apartment units located
near the intersection of North College Road and Murrayville Road in New Hanover County. The property
is approximately 20.60 acres and was constructed in several phases between 2006 and 2015. The
property Owner wishes to construct a new Fitness Center amenity facility located between Buildings 1
and 9 on the western boundary of the site. The new Fitness Center will be approximately 1,195 square
feet in area as shown on the drawings. We are proposing to disturb approximately 7,550 square feet
(0.17 acres) during the construction of the project.
Erosion Control Design Overview
Topography of the project site area is relatively flat and disturbance is localized to two separate small
sub-areas as shown on the drawings. The work site will be protected with a combination of silt fence,
gravel outlets, inlet protection, and other measures to prevent sedimentation from leaving the work
area. No sediment basins are proposed due to the small project area.
Drainage from the work area flows to an existing drop inlet located in the drive aisle in front of the work
zone. Accordingly, a silt-sack inlet protection device will be installed in this drop inlet to prevent
sediment from entering the storm drainage system (note this can be achieved with no disturbance so
we have omitted it from the limits).
Lastly, a small diameter ejector pump sewer pressure service line will be installed from the new facility
to an existing manhole located just north of Building 1. The service will be installed via open cut, and
the immediately backfilled and stabilized.
Once construction activity is completed, the site will be stabilized with vegetative seeding, straw, and/or
sod as dictated by the Owner. Erosion control measures will remain in place until a suitable stand of
vegetation is developed. Once the NHC inspector approves, any remaining measures may be removed.
NOAA Atlas 14, Volume 2, Version 3
Location name: Wilmington, North Carolina, USA*
Latitude: 34.2863°, Longitude: -77.8691°
Elevation: 34.58ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1
Duration Average recurrence interval (years)
1251025501002005001000
5-min 6.25
(5.84‑6.73)
7.43
(6.94‑7.99)
8.70
(8.11‑9.34)
9.68
(9.00‑10.4)
10.9
(10.1‑11.7)
11.9
(10.9‑12.7)
12.9
(11.8‑13.8)
13.8
(12.6‑14.8)
15.1
(13.6‑16.2)
16.1
(14.4‑17.3)
10-min 5.00
(4.67‑5.38)
5.94
(5.54‑6.38)
6.97
(6.49‑7.48)
7.75
(7.19‑8.32)
8.72
(8.06‑9.34)
9.46
(8.71‑10.2)
10.2
(9.35‑11.0)
11.0
(9.96‑11.8)
11.9
(10.7‑12.8)
12.7
(11.3‑13.7)
15-min 4.16
(3.89‑4.48)
4.98
(4.65‑5.35)
5.87
(5.48‑6.30)
6.53
(6.07‑7.02)
7.36
(6.82‑7.90)
7.98
(7.35‑8.57)
8.61
(7.88‑9.23)
9.21
(8.38‑9.89)
10.00
(9.00‑10.8)
10.6
(9.46‑11.4)
30-min 2.85
(2.67‑3.07)
3.44
(3.21‑3.70)
4.17
(3.89‑4.48)
4.73
(4.40‑5.08)
5.46
(5.05‑5.85)
6.01
(5.54‑6.45)
6.59
(6.03‑7.07)
7.17
(6.52‑7.70)
7.95
(7.16‑8.57)
8.58
(7.66‑9.25)
60-min 1.78
(1.66‑1.92)
2.16
(2.01‑2.32)
2.67
(2.49‑2.87)
3.08
(2.86‑3.31)
3.63
(3.36‑3.89)
4.07
(3.75‑4.37)
4.54
(4.16‑4.87)
5.03
(4.57‑5.40)
5.71
(5.14‑6.15)
6.26
(5.59‑6.75)
2-hr 1.05
(0.970‑1.15)
1.28
(1.18‑1.40)
1.63
(1.51‑1.78)
1.93
(1.77‑2.10)
2.36
(2.16‑2.56)
2.73
(2.48‑2.96)
3.13
(2.83‑3.40)
3.57
(3.21‑3.87)
4.23
(3.76‑4.60)
4.79
(4.23‑5.23)
3-hr 0.749
(0.693‑0.820)
0.910
(0.840‑0.995)
1.17
(1.08‑1.27)
1.39
(1.27‑1.51)
1.72
(1.57‑1.87)
2.01
(1.82‑2.19)
2.33
(2.10‑2.54)
2.69
(2.40‑2.92)
3.24
(2.86‑3.52)
3.73
(3.25‑4.05)
6-hr 0.466
(0.431‑0.510)
0.566
(0.524‑0.621)
0.726
(0.669‑0.794)
0.866
(0.795‑0.945)
1.08
(0.981‑1.17)
1.26
(1.14‑1.37)
1.47
(1.32‑1.59)
1.70
(1.52‑1.85)
2.06
(1.81‑2.24)
2.38
(2.07‑2.59)
12-hr 0.271
(0.248‑0.299)
0.330
(0.302‑0.362)
0.425
(0.389‑0.467)
0.510
(0.464‑0.558)
0.638
(0.576‑0.697)
0.752
(0.676‑0.820)
0.882
(0.787‑0.961)
1.03
(0.908‑1.12)
1.26
(1.09‑1.37)
1.46
(1.25‑1.59)
24-hr 0.160
(0.145‑0.179)
0.194
(0.177‑0.218)
0.251
(0.228‑0.281)
0.301
(0.273‑0.336)
0.379
(0.339‑0.422)
0.448
(0.397‑0.498)
0.526
(0.462‑0.586)
0.615
(0.532‑0.686)
0.754
(0.639‑0.846)
0.876
(0.729‑0.988)
2-day 0.095
(0.087‑0.105)
0.115
(0.105‑0.128)
0.147
(0.134‑0.164)
0.175
(0.159‑0.195)
0.218
(0.197‑0.243)
0.256
(0.229‑0.286)
0.299
(0.263‑0.334)
0.348
(0.302‑0.390)
0.422
(0.358‑0.476)
0.487
(0.407‑0.552)
3-day 0.068
(0.062‑0.075)
0.082
(0.075‑0.091)
0.104
(0.095‑0.115)
0.123
(0.112‑0.137)
0.152
(0.137‑0.169)
0.178
(0.159‑0.198)
0.206
(0.182‑0.230)
0.238
(0.207‑0.266)
0.286
(0.245‑0.323)
0.329
(0.276‑0.373)
4-day 0.054
(0.049‑0.060)
0.065
(0.059‑0.072)
0.082
(0.075‑0.091)
0.097
(0.088‑0.108)
0.119
(0.107‑0.132)
0.138
(0.123‑0.154)
0.160
(0.141‑0.178)
0.183
(0.160‑0.205)
0.219
(0.188‑0.246)
0.250
(0.211‑0.283)
7-day 0.035
(0.033‑0.039)
0.043
(0.039‑0.047)
0.054
(0.049‑0.059)
0.063
(0.058‑0.069)
0.076
(0.070‑0.084)
0.088
(0.079‑0.096)
0.100
(0.090‑0.110)
0.114
(0.101‑0.125)
0.133
(0.116‑0.148)
0.150
(0.129‑0.168)
10-day 0.028
(0.026‑0.031)
0.034
(0.031‑0.037)
0.042
(0.038‑0.045)
0.048
(0.045‑0.053)
0.058
(0.053‑0.063)
0.066
(0.060‑0.072)
0.075
(0.068‑0.082)
0.085
(0.076‑0.093)
0.099
(0.087‑0.109)
0.110
(0.096‑0.123)
20-day 0.019
(0.018‑0.020)
0.022
(0.021‑0.024)
0.027
(0.025‑0.029)
0.031
(0.029‑0.034)
0.037
(0.034‑0.040)
0.042
(0.038‑0.045)
0.047
(0.043‑0.051)
0.052
(0.047‑0.057)
0.060
(0.053‑0.066)
0.066
(0.058‑0.073)
30-day 0.015
(0.014‑0.016)
0.018
(0.017‑0.020)
0.022
(0.021‑0.023)
0.025
(0.023‑0.027)
0.029
(0.027‑0.031)
0.032
(0.030‑0.035)
0.036
(0.033‑0.038)
0.039
(0.036‑0.042)
0.044
(0.040‑0.048)
0.048
(0.043‑0.052)
45-day 0.013
(0.012‑0.014)
0.015
(0.014‑0.016)
0.018
(0.017‑0.019)
0.020
(0.019‑0.021)
0.023
(0.022‑0.025)
0.026
(0.024‑0.028)
0.028
(0.026‑0.030)
0.031
(0.029‑0.033)
0.035
(0.032‑0.037)
0.037
(0.034‑0.041)
60-day 0.012
(0.011‑0.012)
0.014
(0.013‑0.014)
0.016
(0.015‑0.017)
0.018
(0.017‑0.019)
0.020
(0.019‑0.021)
0.022
(0.021‑0.023)
0.024
(0.022‑0.026)
0.026
(0.024‑0.028)
0.028
(0.026‑0.031)
0.030
(0.028‑0.033)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates
(for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds
are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values.
Please refer to NOAA Atlas 14 document for more information.
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National Weather Service
National Water Center
1325 East West Highway
Silver Spring, MD 20910
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NOAA Atlas 14, Volume 2, Version 3
Location name: Wilmington, North Carolina, USA*
Latitude: 34.2863°, Longitude: -77.8691°
Elevation: 34.58ft**
* source: ESRI Maps
** source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok, M.Yekta, and D. Riley
NOAA, National Weather Service, Silver Spring, Maryland
PF_tabular | PF_graphical | Maps_&_aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration Average recurrence interval (years)
1251025501002005001000
5-min 0.521
(0.487‑0.561)
0.619
(0.578‑0.666)
0.725
(0.676‑0.778)
0.807
(0.750‑0.867)
0.912
(0.843‑0.977)
0.990
(0.911‑1.06)
1.07
(0.981‑1.15)
1.15
(1.05‑1.24)
1.25
(1.13‑1.35)
1.34
(1.20‑1.45)
10-min 0.833
(0.778‑0.896)
0.990
(0.924‑1.06)
1.16
(1.08‑1.25)
1.29
(1.20‑1.39)
1.45
(1.34‑1.56)
1.58
(1.45‑1.69)
1.70
(1.56‑1.83)
1.83
(1.66‑1.96)
1.99
(1.79‑2.14)
2.11
(1.89‑2.28)
15-min 1.04
(0.973‑1.12)
1.24
(1.16‑1.34)
1.47
(1.37‑1.58)
1.63
(1.52‑1.75)
1.84
(1.70‑1.97)
2.00
(1.84‑2.14)
2.15
(1.97‑2.31)
2.30
(2.09‑2.47)
2.50
(2.25‑2.69)
2.65
(2.37‑2.86)
30-min 1.43
(1.33‑1.54)
1.72
(1.60‑1.85)
2.09
(1.95‑2.24)
2.37
(2.20‑2.54)
2.73
(2.52‑2.92)
3.01
(2.77‑3.23)
3.30
(3.02‑3.54)
3.58
(3.26‑3.85)
3.98
(3.58‑4.28)
4.29
(3.83‑4.63)
60-min 1.78
(1.66‑1.92)
2.16
(2.01‑2.32)
2.67
(2.49‑2.87)
3.08
(2.86‑3.31)
3.63
(3.36‑3.89)
4.07
(3.75‑4.37)
4.54
(4.16‑4.87)
5.03
(4.57‑5.40)
5.71
(5.14‑6.15)
6.26
(5.59‑6.75)
2-hr 2.10
(1.94‑2.30)
2.56
(2.36‑2.80)
3.27
(3.01‑3.56)
3.86
(3.55‑4.20)
4.71
(4.31‑5.13)
5.45
(4.96‑5.93)
6.26
(5.67‑6.80)
7.14
(6.42‑7.75)
8.45
(7.51‑9.19)
9.58
(8.45‑10.5)
3-hr 2.25
(2.08‑2.46)
2.73
(2.52‑2.99)
3.50
(3.23‑3.82)
4.17
(3.82‑4.54)
5.16
(4.71‑5.61)
6.03
(5.47‑6.56)
7.00
(6.31‑7.61)
8.09
(7.22‑8.77)
9.74
(8.59‑10.6)
11.2
(9.75‑12.2)
6-hr 2.79
(2.58‑3.06)
3.39
(3.14‑3.72)
4.35
(4.01‑4.75)
5.18
(4.76‑5.66)
6.44
(5.88‑7.00)
7.54
(6.85‑8.20)
8.79
(7.93‑9.54)
10.2
(9.07‑11.1)
12.3
(10.8‑13.4)
14.2
(12.4‑15.5)
12-hr 3.26
(2.99‑3.60)
3.97
(3.64‑4.36)
5.12
(4.69‑5.63)
6.14
(5.60‑6.73)
7.68
(6.94‑8.40)
9.06
(8.14‑9.88)
10.6
(9.48‑11.6)
12.4
(10.9‑13.5)
15.2
(13.2‑16.5)
17.6
(15.1‑19.2)
24-hr 3.84
(3.49‑4.29)
4.66
(4.24‑5.22)
6.03
(5.47‑6.74)
7.23
(6.55‑8.07)
9.09
(8.14‑10.1)
10.7
(9.54‑12.0)
12.6
(11.1‑14.1)
14.8
(12.8‑16.5)
18.1
(15.3‑20.3)
21.0
(17.5‑23.7)
2-day 4.56
(4.16‑5.06)
5.51
(5.03‑6.12)
7.07
(6.44‑7.85)
8.42
(7.65‑9.36)
10.5
(9.44‑11.7)
12.3
(11.0‑13.7)
14.4
(12.6‑16.0)
16.7
(14.5‑18.7)
20.2
(17.2‑22.8)
23.4
(19.5‑26.5)
3-day 4.86
(4.45‑5.40)
5.87
(5.37‑6.52)
7.48
(6.82‑8.31)
8.87
(8.06‑9.85)
11.0
(9.87‑12.2)
12.8
(11.4‑14.2)
14.8
(13.1‑16.6)
17.1
(14.9‑19.2)
20.6
(17.6‑23.2)
23.7
(19.9‑26.8)
4-day 5.17
(4.73‑5.74)
6.24
(5.70‑6.91)
7.90
(7.20‑8.76)
9.32
(8.47‑10.3)
11.4
(10.3‑12.7)
13.3
(11.9‑14.8)
15.3
(13.5‑17.1)
17.6
(15.3‑19.7)
21.0
(18.0‑23.6)
24.0
(20.2‑27.2)
7-day 5.96
(5.50‑6.52)
7.18
(6.63‑7.86)
9.02
(8.31‑9.88)
10.6
(9.70‑11.6)
12.8
(11.7‑14.0)
14.7
(13.3‑16.1)
16.8
(15.1‑18.5)
19.1
(16.9‑21.0)
22.4
(19.6‑24.9)
25.2
(21.7‑28.2)
10-day 6.74
(6.23‑7.33)
8.07
(7.46‑8.79)
10.00
(9.21‑10.9)
11.6
(10.7‑12.7)
14.0
(12.8‑15.2)
15.9
(14.5‑17.4)
18.0
(16.3‑19.7)
20.3
(18.2‑22.3)
23.7
(20.9‑26.2)
26.5
(23.0‑29.5)
20-day 9.03
(8.40‑9.73)
10.7
(10.0‑11.6)
13.1
(12.2‑14.1)
15.0
(14.0‑16.2)
17.8
(16.4‑19.2)
20.1
(18.4‑21.7)
22.5
(20.5‑24.4)
25.1
(22.7‑27.3)
28.7
(25.6‑31.5)
31.7
(27.9‑35.0)
30-day 11.1
(10.4‑11.8)
13.1
(12.3‑14.1)
15.8
(14.8‑16.9)
17.9
(16.8‑19.1)
20.9
(19.5‑22.3)
23.3
(21.6‑24.9)
25.7
(23.7‑27.6)
28.3
(25.9‑30.4)
31.8
(28.7‑34.5)
34.6
(31.0‑37.7)
45-day 13.8
(13.0‑14.7)
16.3
(15.4‑17.4)
19.4
(18.3‑20.6)
21.8
(20.5‑23.2)
25.2
(23.6‑26.8)
27.9
(26.0‑29.7)
30.7
(28.5‑32.7)
33.5
(30.9‑35.9)
37.4
(34.1‑40.2)
40.4
(36.5‑43.8)
60-day 16.6
(15.7‑17.6)
19.5
(18.5‑20.7)
22.8
(21.6‑24.3)
25.5
(24.0‑27.0)
29.0
(27.3‑30.8)
31.8
(29.8‑33.8)
34.5
(32.2‑36.8)
37.3
(34.6‑39.9)
41.0
(37.6‑44.0)
43.8
(40.0‑47.3)
1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency
estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%.
Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP
values.
Please refer to NOAA Atlas 14 document for more information.
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Wet Detention Basin Modification Calculations
Project: Villas at Murrayville
Location: Wilmington, NC
Date 1/17/2020
Pond Number: 1
Total Project Area: 897,168sf or 20.60ac
Total On-Site Drainage Area: 897,168sf or20.60ac
Off-site Drainage Area:0sf or0.00ac
Total: 20.60ac.
On-Site Impervious Area:
Buildings (Existing):90,207sf Originally Approved Imp. Area: 338,953
Parking & Roads (Existing):191,629sf Original Approved % Imp:37.78%
Sidewalks (Existing):35,162sf
New Impervious: 1,249 sf Modified Watershed % Imp: 37.92%
Future Impv. (from Mod): sf(including new Imp. Area)
Outparcel (Existing):21,955sfTotal New Impervious Area: 1,249
Total Impervious Area: 340,202sf or 7.81ac.
Calculate Required Surface Area:
Avg. Perm. Pool Depth: 7.5 feet(per SW8 060717)Interpolated SA/DA for Impervious Percentage:
SA/DA Ratio: 1.038 Imp. PercentageRatio
Lower Limit30.00%0.8
Minimum Required Surface Area: 9309sfUpper Limit40.00%1.1
Actual37.92%1.038
(90% TSS Archived Table from Original Design)
Calculate Original WQv Storage Volume:
Use Simple Method with volume for 1.0" storm (per original pond design):
Rv= 0.05+0.009(I)
Rv= Runoff Coefficient (ratio of runoff to rainfall in inches)
Io= Impervious Percentage-Original
Rv= 0.39
WQv= 3630 x Rd x Rv x ARd= Design Storm= 1.0"
A= Drainage Area
WQv=29253cf WQv= Storage Volume
ElevationContour AreaInc. Volume
Accumulated
Volume Stage
(sf)(cf)(cf)
26.5032519000
27.003354116515165150.5b=1.0638
Calculated S-S Parameters:
28.003548834515510301.5Ks=34523.7212
29.003746936479875082.5
30.0039537385031260113.5Orifice El: 26.50
3141615405761665874.5Overflow El: 27.50
3243845427302093175.5
32.547818229162322336
Overflow Spillway Stage: 1ft
Spillway Crest Length2ft
Storage Below Overflow: 34524 cfS=Ks*Z^b
WQv Stage: 0.86 or Elevation 27.36
Surface Area at WQv Stage: 34212Square Feet
Calculate WQv Drawdown Time:
Drawdown Orifice Diameter:3.00Cross Section Area: 0.04906sf
Orifice Coefficient:0.60Average Head: 0.2917ft
Number of Orifices:1Discharge: 0.1276cfs
WQv Drawdown Time: 63.69hours or 2.65days
Project #NoDate
Project Name
Date
ABCD
68798689
49697984
39617480
Impervious Areas
98989898
83899898
76858991
72828588
Poor Condition45667783
Fair Condition36607379
Good Condition30557077
Drainage Area =20.60 ac
Total Area in "A" Soils =14.42 ac
Total Area in "B" Soils 4.12 ac
Total Area in "C" Soils 0.00 ac
Total Area in "D" Soils =2.06 ac
Poor Fair Good
725748
989898
534540
12.82 ac
7.78 ac
0.00 ac
PoorFair Good
8272 67
Project Data Revisions
2019-037 Description
Villas at Murrayville
2/11/2020
SOIL WEIGHTED CN VALUES
Pre-Developed - Drainage Area No. 1
Curve Numbers for Hydrologic Soil Group
Open Space (Lawns, Parks)
Poor Condition
Fair Condition
Good Condition
BaymeadeA
Parking Lots, Roofs
Paved; Curbs
Paved; Open Ditches
Gravel
Dirt
Woods
Types of Soils with in Drainage Area Soil Area in Drainage Area
Soil NameHydrologic Group
JohnsonD
PantegoB
SeagateA
Use the following CN Values for each Land Use
Open Space =
Impervious Surface =
Wooded Area =
Land Uses in Sub-Basin
Open Space
Impervious
Wooded
Weighted CN Value
Project #NoDate
Project Name
Date
ABCD
68798689
49697984
39617480
Impervious Areas
98989898
83899898
76858991
72828588
Poor Condition45667783
Fair Condition36607379
Good Condition30557077
Drainage Area =20.60 ac
Total Area in "A" Soils =14.42 ac
Total Area in "B" Soils 4.12 ac
Total Area in "C" Soils 0.00 ac
Total Area in "D" Soils =2.06 ac
Poor Fair Good
725748
989898
534540
12.79 ac
7.81 ac
0.00 ac
PoorFair Good
8272 67
Project Data Revisions
2019-037 Description
Villas at Murrayville
2/11/2020
SOIL WEIGHTED CN VALUES
Post-Developed - Drainage Area No. 1
Curve Numbers for Hydrologic Soil Group
Open Space (Lawns, Parks)
Poor Condition
Fair Condition
Good Condition
BaymeadeA
Parking Lots, Roofs
Paved; Curbs
Paved; Open Ditches
Gravel
Dirt
Woods
Types of Soils with in Drainage Area Soil Area in Drainage Area
Soil NameHydrologic Group
JohnsonD
PantegoB
SeagateA
Use the following CN Values for each Land Use
Open Space =
Impervious Surface =
Wooded Area =
Land Uses in Sub-Basin
Open Space
Impervious
Wooded
Weighted CN Value