SW3221004_BUA Design Calculations_20221012

EROSION CONTROL and BUA
CALCULATIONS FOR LOW DENSITY
STORMWATER
For
MOUNT PLEASANT HIGH SCHOOL
SYNTHETIC TURF FIELD PROJECT
Cabarrus County
Lot 0 .N
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SEAL
20165
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Kevin E. Herring
ENGINEERING
18101 SAw Read
0alda p, NC28129
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PROJECT: MOUNT PLEASANT HIGH SCHOOL TURF FIELD
NARRATIVE
Proposed project is the installation of a synthetic turf field inside the existing running
track at Mount Pleasant High School off Walker Rd in Mount Pleasant NC (Cabarrus
County).
The area of work is primarily limited to the natural grass field inside the track perimeter.
The turf field scope of work includes installation of silt fence, inlet protection, removal of
existing organics and soil, compaction of subgrade, installation of perimeter curbing,
stone base, and synthetic turf. Scope of work also includes construction of new concrete
pole vault runway and landing pad outside the track.
High Jump Pad and Long Jump/Pole Vault runways to be reconstructed and surfaced
with synthetic track surfacing.
All spoils to be hauled to designated area on -site.
The total disturbed acreage for this project is 2.50 acres.
Based on USDA Web Soil Survey data the area soils primarily classify as MeD
(Mecklenburg), a loamy soil indicative of hydraulic group C.
STORMWATER NARRATIVE
Project is proposed as LOW DENSITY for the entire site. Total property area is 100.9
ac. There is 1.86 ac of surface water on the property resulting in a total site project area
of 99.04 ac. The existing BUA on the property is 18.80 ac based on aerial data. BUA to
be removed from within the proposed field area is 0.13 ac. The new BUA (Turf Field) to
be added is 2.35 ac for a net increase of 2.22 ac. The new BUA of the overall property
after the project is 21.22% [(18.80-0.13+2.35)/99.04] which is less than 24%.
New BUA will be dispersed into existing field drainage system and site conveyances
with no changes outside of the existing turf field. Artificial turf fields typically provide
reduced peak flows from that of typical impervious surfaces due to increased time of
concentrations. Post time of concentrations are often higher than that of pre -developed
Tc's. The turf system is typically modeled as porous pavement with the flow through the
stone base media as a function of Darcy's equation resulting in a reduction of peak flows
at outlets. This results in negligible peak flow impact to the existing drainage system and
conveyances.
Stream and wetland delineation was provided by Isaac Hinson PWS #1866.

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PROJECT: MOUNT PLEASANT HIGH SCHOOL TURF FIELD
STREAM CLASSIFICATION
Surface Water Classifications:
Stream ind ex
'Strearn Name:
Description:
Classification:
Date o1•Class.:
What does this
Class, mean?
River Bas;n--
zc Gm to
13-17-11-7
Adams Creek
From source to Dutch
Buffalo Creek
C
April 5 1955
More irdo
Yadkin Pee -Dee
tD
,Y

The National Map Advanced Viewer
6/1/2022, 4:28:25 PM
1:24,000
0 0.15 0.3
0 0.28 0.55
Copyright:© 2013 National Geographic Society, i-cubed
0.6 mi
1.1 km
USGS
2021 USGS

BUA CALCULATIONS

SEA
L {
20165 -
S ►s-���
Delineated Exist.
BUA (Google Earth)
Exist BUA = 18.80ac
Project Area
Track Interior
New BUA = 2.35ac
= 1.86ac
Scale 1 "=400'
:'A
Boundary
Main Parcel #5650766035
e
NOW OR LY
CA8ARRUS COUNTY 1
DB 11748, PG 0261. M.T.M.
#565087472, fill
nterior Parcel
f5650862338
krea = 2.06ac (GiS
BUA to be
removed = 0.13ac
'ROPOSED PROJECT (L01N DEiVSETY )
PROPOSED SCOPE: ARTIFICIAL TURF FIELD WITH NEW HIGH JUMP PAD
AND LONG JUMP ANC HIGH JUMP RUNWAYS
PROPOSED LAND DISTURBANCE: 2.5 AC
EXISTING SITE AREA: 4,395,20C SF a 100.90 AC
EXiST. SURFACE WATER AREA: 8j.Q57 17 _ 1 ES A.0 (STREAMS)
TOTAL PROJECT AREA: 4.,314,143 SF — 99.04 AC
EXISTING SITE BUA: BD6,614 SF = 18.52 AC
EXIST NCDOT ROADWAY' BUA: _ 12100 SF = 0,23 AG
TOTAL EXISTING BUA: 818,714 SF o 18.80 AC
NEW BUA ADDED: 102.500 SF = 2,55 AG
EXIST, SITE BUA REMOVED: 5,700 SF — 0.13 AG
NET BUA ADDED: 96,800 SF = 2.22 AC
PROPOSED OVERALL SITE BUA: 915,514 SF 21,02 AC
PROPOSED PROJECT DENSITY; 21.02 AG199.04 AC = 21,22% G 24%

Pro ect area and density information
Total Property Area
4,395,200
sf
Total Surface Water Area
81.057 sf
Considered to include:
• the normal pool of impounded structures,
• the area between the banks orstreams and rivers, and
• the area below the Normal High Water {NHW) line or Mean High Wafer (MHO) tine.
Total Coastal Wetlands Area
0 sf
Considered to include coastal wettands Landward from the NNW (or ARHW) lane.
Total Project Area
4,314.14
sf
Excludes the surface water area and coastal wetland area identified above.
May or may not be the same as Property Area.
Built -Upon Area, (BUA) associated with Existing Development
818,714 sf
"Existing development"meargs those projects that are i)atit or those projects trrat have esfablrshed a
vested nght under North Carolina law as of the effective dare or the state stormwater program Of
applrcabie local government ordinarice to wh;ch the project is subject.
Proposed New BUA
96800 sf
Includes proposed new BUR that is not associated Will, existinq development.
`BUA'is defined in N.C.G.S. 143-214.7(b2). It includes, but is not limited to buildings. roads, Parking
the
areas, sidewalks. and some gravel areas. The design volume of SCA9s must fake into account runoff
from build out from all surfaces draining to the sCAI rn accordance win) 15A NCAC 02H 1050 f 1).
Project Density
w/ Existing Development Project Density = {Ne%v SUA11[70tal Project Area — Existing BUA) x 100 or
21.22
L,//o Existing Development. Project Density = [NeLv 8UAjITotal Project Area] x 100

EROSION CONTROL
CALCULATIONS

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Job: Mount Pleasant High School Job No
Subject: Temporary Sediment Containment
Date 5/30/2022 Sheet
By KEH Chk By
TRAP
DRAINAGE
AREA
(Ac)
DISTURBED
AREA
(Ac)
Runoff
Coeff.
C
Tc
(min)
Intensity
1(10)
(in/hr)
10 YEAR
PEAK
Q(10) cfs
Containment
3.27
2.32
0.70
5
7.28
16.70
Field runoff stays fully within track perimeter. DA includes track area where it slopes inward toward
field. Outside of track slopes away from field.
Intensity taken from NOAA Atlas 14 rainfall data
COMPOSITE RUNOFF "C" BASED ON C(DIST)=0.60 & C(UN-DIST)=0.95 (Track)
DISCHARGE DETERMINED USING RATIONAL METHOD (Q=CIA) REF: NC Erosion & Sediment Control Manual
Figure 8.03d
SEDIMENT
TRAP
DESIGN
Required
Containment Dimensions
@ Top of Inlet Protection Stone
Provided
Surface
Area
Volume
Surface
Area
Volume
Width(ft)
Length(ft)
Depth(ft)
Containment
Q(10)
7265
8370
66.7
X
1000
X
0.25
62900
14153
Reference
Note #1
Note #2
Note #3
Note #4
Note #5
Note #6
Note #7
Notes
Required Determination
1. Surface Area Required(sf) = 435 square feet*Q(10)
2. Volume Required (cf)= 3600 cubic feet per acre disturbed area
Provided Calculation
3. Containment Width based on 0.75% slope of subgrade and 6" depth of stone at inlet protection. 0.5'/0.75%=67' into field
4. Length of storage is distance measure halfway within containment width (1000'+/- Total)
5. Depth of storage = average depth between 6" @ 0' and 0" at 67' = 3" = 0.25'
6. Containment Surface Area Provided (sf) = Width X Length Less Existing HJ Pad
7. Containment Volume Provided (cf) = Area Provided x Depth (less 10% due to area loss around excavation perimeter)

Kevin E. Herring ENGINEERING
Job: MOUNT PLEASANT HIGH SCHOOL Job No. Date 5/30/2022 Sheet
Subject: Typical Sediment Containment Area By KEH Chk By
V
— . 7' +/ - -
( F1}0.7 0/6)
Inlet
Prot.

PROJECT: MOUNT PLEASANT HIGH SCHOOL TURF FIELD
NOAA ATLAS 14 RAINFALL DATA
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Move crosshair or doudla click
hJ Click on station icon
[I Show stations on map
Location information:
°y
Name: [North Camlina. USA`
el
Latitude: 35.4047`
Longitude:-80.4&29`
x
FJe tion: 617.23 B "
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`Source. ESRI Maps
"Source:
USGS

5/30/22, 8:39 PM
Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
' Location name: North Carolina, USA*
Latitude: 35.4047°, Longitude:-80.4829°
. Elevation: 617.23 ft-
'source: ESRI Maps
'%yw
"source: USGS
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parzybok M.Yelda, and D. Riley
NOAA, National Weather Servios, Silver Spring, Maryland
PF tabular I P_gMhD Ical I Mao & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)1
Duretion
recurrence interval
eare0000
�OOOOge
1
2
5
10
25
0
50
0
100
200
500
1000
5-
4: 5-5.23
5.26-620
610--7.21
6.68-27890
7.32-8.68
7: 39.20
8.09 9568
8.40-310.1
8: 0 0.6
8.87- 0.9
10-min
35 5-4.18
4.20-496
4: 8-5.77
5.34fi 31
5.8336.91
616-7.33
6. 3-7.70
6.6638.00
6.88-8.35
6.98956
3.21
3.11
4.1
4.11
5.41
5.72
5.11
1.22
6.46
1.11
15-min
(2 .96-3.48)
(3.52-4.16)
(4.12-4.87)
(4.505.32)
(4.93-5.84)
(5.20-6.19)
(5.425.48)
(5.60-6.74)
(5.77-7.01)
(5.84-7.16)
2.21
2.63
3.11
3.1
4.11
4.31
4.11
4,11
5.14
5.34
30-min
(2.03-2.39)
(2.3-2.87)
(2.93-3.46)
(3.263.86)
(3.65-4.33)
(3.91-4.66)
(4.15-4.97)
(4.36-5.24)
(4.59-5.58)
(4.735.80)
1.37
1.11
2.14
2.32
2.11
2.12
3.11
3.31
3.11
3.11
60-min
(1.26-1.49)
(1.53-1.80)
(1.88-2.22)
(2.13-2.51)
(2.3-2.88)
(2.65-3.16)
(2.863.42)
(3.06-3.68)
(3.29-4.00)
(3.45-4.23)
0.792
0.960
1.19
1.36
1.59
1.75
1.92
2.07
2.28
2.44
2-hr
(0.726-0.866)
(0.878-1.05)
1 (1.09-1.30) 11
(1.24-1.49)
1 (1.44-1.73)
1 (1.58-1.91) 11
(1.72-2.09)
(1.85-2.26)
(2.01-2.49)
(2.13-2.66)
0.564
0.681
0.849
0.978
1.15
1.28
1.12
1.55
1.73
1.87
3-hr
(0.517-0.616)
(0.624-0.745)
(0.778-0.929)
(0.891-1.07)
1 (1.04-1.25)
1 (1.16-1.40) 11
(1.27-1.54)
1 (1.38-1.68) 11
(1.52-1.88) 11
(1.63-2.04)
0.343
0.113
0.515
0.595
0.702
0.786
0.872
0.959
1.08
1.17
6-hr
(0.314-0.375)
(0.39-0.452)
(0.471-0.563)
(0.542-0.649)
(0.635-0.764)
(0.707-0.855)
(0.79-0.948)
1 (0.849-1.04) 11
(0.942-1.17) 11
(1.01-1.27)
0.202
0.244
0.306
0.356
0.423
0.477
0.532
0.590
0.670
0.734
12-hr
(0.186-0.220)
(0.224-0.267)
(0.281-0.334)
(0.325-0.388)
(0.383-0.459)
(0.428-0.517)
(0.474-0.576)
(0.520-0.637)
(0.581-0.722)
(0.628-0.792)
0.120
0.115
0.182
0.211
0.251
0.282
0.311
0.348
0.393
0.129
24-hr
(0.111-0.130)
(0.135-0.157)
(0.169-0.197)
(0.196-0.228)
(0.232-0.271)
(0.260-0.305)
(0.289-0.339)
(0.319-0.376)
(0.359-0.425)
(0.390-0.465)
0.1.1
2-day
0.065-0 076
009-00920098
0.114
0.113-0.0.1132
0.134 0..11550.149-0
1750.166-0
194
0.182 0 214
0.205-0 242
0.222-0264
054
3-day
0.046-0
0056-0064
0069-0.080
00 9-0092
0093 0109
0.104-0.1122
0.1016-0..1135
0.127-0.1149
0.143-0 169
0.155-0 184
4-day
0.037-0042
0044-0051
0054-0.063
0.062-0072
0.0073-0085
0.082-0.095
0091-0.1106
0.100-0.1117
0.1112-0..1132
0.121-0.1144
1.121
1.131
1.11
1.143
1.111
1.11
1.112
1.111
1.177
1.114
7-day
(0.024-0.028)
(0.029-0.033)
(0.035-0.040)
(0.040-0.046)
(0.047-0.054)
(0.053-0.060)
(0.058-0.067)
(0.064-0.073)
(0.071-0.083)
(0.077-0.090)
1.121
1.125
1.11
1.134
1.131
1.11
1.147
1.112
1.11
1.112
10-day
(0.020-0.022)
(0.023-0.026)
(0.028-0.032)
(0.032-0.036)
(0.036-0.041)
(0.040-0.046)
(0.044-0.050)
(0.048-0.055)
(0.053-0.061)
(0.057-0.066)
1.114
1.117
1.111
1.122
1.125
1.11
1.131
1.133
1.131
1.131
20-day
(0.013-0.015)
(0.016-0.017)
(0.018-0.021)
(0.021-0.023)
(0.024-0.026)
(0.026-0.029)
(0.028-0.032)
(0.030-0.034)
(0.034-0.038)
(0.036-0.041)
0.011
0.013
0.016
0.017
0.020
0.021
0.023
0.025
0.027
0.029
30-day
(0.011-0.012)
(0.013-0.014)
(0.015-0.016)
(0.016-0.018)
(0.019-0.021)
(0.020-0.022)
(0.022-0.024)
(0.023-0.026)
(0.0250.028)
(0.027-0.030)
0.010
0.011
0.013
0.014
0.016
0.017
0.018
0.019
0.021
0.022
45-day
(0.009-0.010)
(0.011-0.012)
(0.012-0.013)
(0.013-0.015)
(0.015-0.016)
(0.016-0.018)
(0.017-0.019)
(0.018-0.020)
(0.020-0.022)
(0.021-0.023)
0.009
0.010
0.011
0.012
0.014
0.015
0.016
0.017
0.018
0.019
60-day
(0.008-0.009)
(0.010-0.010)
(0.011-0.012)
(0.012-0.013)
(0.013-0.014)
(0.014-0.015)
(0.015-0.016)
(0.016-0.017)
(0.017-0.019)
(0.018-0.019)
Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS).
r a
Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimaLrsn(_
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 a
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.
Back to Top
PF graphical
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=35.4047&Ion=-80.4829&data=intensity&units=english&series=pds 1/3

N
35o 24' 22" N
M
93
N
93
1
93
1
93
0
93
35o 24' 15" N
546890 546910 546930 546950 546970
N Map Scale: 1:926 if printed on A portrait (8.5" x 11") sheet.
$ N Meters
0 10 ZO 40 60
Feet
0 45 90 180 270
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
usoA Natural Resources Web Soil Survey
Conservation Service National Cooperative Soil Survey
Hydrologic Soil Group—Cabarrus County, North Carolina
(Mount Pleasant High School)
546890 546910 546930 546950 546970
547010
35o 24' 22" N
M
93
N
93
1
93
1
93
0
°3 35o 24' 15" N
547010
in
5/9/2022
Pagel of 4

Hydrologic Soil Group—Cabarrus County, North Carolina
(Mount Pleasant High School)
MAP LEGEND
Area of Interest (AOI)
0
Area of Interest (AOI)
Soils
Soil Rating
Polygons
0
A
0
A/D
0
B
0
B/D
C
0
C/D
0
D
0
Not rated or not available
Soil Rating
Lines
r 0
A
r 0
A/D
B
B/D
N 0
C
r 0
C/D
r 0
D
r 0
Not rated or not available
Soil Rating
Points
0
A
0
A/D
0
B
0
B/D
❑ C
0 C/D
0 D
❑ Not rated or not available
Water Features
Streams and Canals
Transportation
— Rails
­0 Interstate Highways
US Routes
Major Roads
Local Roads
Background
D6 Aerial Photography
MAP INFORMATION
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Cabarrus County, North Carolina
Survey Area Data: Version 21, Jan 21, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Oct 28, 2018—Oct
30, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
usoA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Group—Cabarrus County, North Carolina
Mount Pleasant High School
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
CuB2
Cullen clay loam, 2 to 8
percent slopes,
moderately eroded
B
0.3
13.0%
MeD
Mecklenburg loam, 8 to
15 percent slopes
C
2.1
87.0%
Totals for Area of Interest
2.4
100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Cabarrus County, North Carolina
Mount Pleasant High School
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 5/9/2022
Conservation Service National Cooperative Soil Survey Page 4 of 4