HomeMy WebLinkAboutSW5210702_Plansheet - Misc. Detail_20210708 (2)STORMWATER NARRATIVE:
LOUISBURG ANNEX
Prepared for
GFD MANAGEMENT INC.
6350 Quadrangle Drive
Suite 205
Chapel Hill, NC 27517
Bohler Project #: NCR211056
1st Submittal: July 2, 2021
t
SEAL -
485
Charlie Yowell, PE
H LER//
BOHLER ENGINEERING NC, PLLC
4130 Parklake Avenue, Suite 130, Raleigh, NC 27612
NCBELS # P-1132 I P: 919-578-9000 1 F: 919-703-2665
www.bohlerengineering.com
TABLE OF CONTENTS
1. DESCRIPTION............................................................................................................................1
1.1 General Project Description.....................................................................................................1
1.2 Stormwater Summary..............................................................................................................1
1.3 Erosion Control Summary........................................................................................................2
APPENDIX A SUPPORTING DOCUMENTS
APPENDIX B STORMWATER NETWORK DESIGN
APPENDIX C PRE/POST DEVELOPMENT DRAINAGE MAPS
BOHLER
BOHLER ENGINEERING NC, PLLC
1. DESCRIPTION
1.1 General Project Description
GFD Management Inc. is proposing to develop a commercial back office building on a pad ready
graded site located at in the Louisburg Plaza, in Louisburg, NC. The new development proposes
to construct one commercial back office building with associated utility, stormwater, fine grading,
and landscaping improvements to support the development. The site will utilize an existing offsite
stormwater network and SCM wetpond. The site is cleared and has been previous disturbed as
part of the Louisburg Plaza master plan.
I
Figure 1: Aerial View of Site
1.2 Stormwater Summary
Drainage flows from the North to South and the post -development drainage pattern closely
matches the existing drainage area and discharge locations. The proposed development will
have 1.18 acres of impervious area over the 2.29-acre site for a BUA of 51.5%. The existing
stormwater network and wetpond have been sized to handle 2.08 acres, which is above what
this development is proposing.
Runoff from the building, parking lots, and driveways will be collected by storm inlets and piped
to the existing storm network in the access road. Stormwater runoff will be from commercial
uses. The development will not adversely impact the existing network, wetpond, nor the
adjacent properties. Refer to Appendix D for additional information.
BOHLERI
BOHLER ENGINEERING NC, PLLC
Page I 1
1.3 Erosion Control Summary
The site is subject to NCDEQ erosion control standard and specifications as the project is above
1 acre of disturbance. This project will have a 2-stage erosion control sequence. Stage 1 will
propose silt fence, silt fence outlets, and inlet protection for fine grading activities. Stage 2 will
consist of installation of storm drainage and utilities, paving operations, and the construction of
the building.
BOHLERI
BOHLER ENGINEERING NC, PLLC
Page 1 2
APPENDIX A ISUPPORTING DOCUMENTS
BOHLERI
BOHLER ENGINEERING NC, PLLC
Hydrologic Soil Group —Franklin County, North Carolina
(Louisburg Annex Soils Map)
741330 741350 741370 741390 741410 741430
741450
36o 4' 57" N
I I * I I I I
"
36o 4' 57" N
r 4 1 rr
F
•5
M
'
aD
of
36o 4' 51" N
Soil MaN may not he valiel at this scale.
36o 4' 51" N
741330 741350 741370 741390 741410 741430
741450 741470
Map Scale: 1:957 if printed on A portrait (8.5" x 11") sheet.
En
01
Meters
o
N 0 10 20 40 60
Feet
0 45 90 1� 270
Map projection: Web Mercator Conermordinates: WGS84 Edge tics: lfrM Zone 17N WGS84
USDA
Natural Resources Web Soil Survey
7/2/2021
0111111111111111
Conservation Service National Cooperative Soil Survey
Pagel of 4
Hydrologic Soil Group —Franklin County, North Carolina
(Louisburg Annex Soils Map)
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
0
C
0
C/D
0
D
0
Not rated or not available
Soil Rating
Lines
r 0
A
r 0
A/D
B
r
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
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: Franklin County, North Carolina
Survey Area Data: Version 23, Jun 4, 2020
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: May 25, 2016—Nov
17, 2017
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.
USDA Natural Resources Web Soil Survey 7/2/2021
Conservation Service National Cooperative Soil Survey Page 2 of 4
Hydrologic Soil Group —Franklin County, North Carolina
Louisburg Annex Soils Map
Hydrologic Soil Group
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
WbD
Wake-Wateree-
B
0.1
2.8%
Wedowee complex, 8
to 15 percent slopes,
rocky
WeB
Wedowee sandy loam, 2
B
1.8
87.6%
to 6 percent slopes
WeC
Wedowee sandy loam, 6
B
0.2
9.6%
to 10 percent slopes
Totals for Area of Interest
2.0
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 7/2/2021
Conservation Service National Cooperative Soil Survey Page 3 of 4
Hydrologic Soil Group —Franklin County, North Carolina
Louisburg Annex Soils Map
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff.- None Specified
Tie -break Rule: Higher
USDA Natural Resources Web Soil Survey 7/2/2021
Conservation Service National Cooperative Soil Survey Page 4 of 4
NORiA
AROUNA
Quami Aru1 LE LOCATIOM
1 KittreU
1 2 3 2ingleside
3 Gold Sand
4 5 4 Franklinton
5 Justice
G Rolesrille
6 7 8 7 Bunn West
8 Bunn East
ADJORIM QUADRARGLE5
ROAD CLASSIFICATION
Expressway I Local Connector
Secondary Hwy Local Road
Ramp 4WD
■ Interstate Route C3 US Route O State Route
LOUISBURG, NC
2019
Precipitation Frequency Data Server
Page 1 of 4
NOAA Atlas 14, Volume 2, Version 3
Location name: Louisburg, North Carolina, USA"
Latitude: 36.0827°, Longitude:-78.3189°
Elevation: 306.39 ft-
* source: ESRI Maps 'ate
** 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 I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hour)'
Average
recurrence interval (years)
Duration
���
10
25
50
100
200
500
1000
4.90
5.68
6.42
7.26
8.08
8.76
9.36
9.90
10.5
11.1
5-min
(4.49-5.36)
1 (5.21-6.19)
1 (5.88-7.00)
1 (6.65-7.92)
1 (7.36-8.81)
1 (7.93-9.55)
(8.42-10.2)
1 (8.86-10.8)
1 (9.32-11.5)
1 (9.73-12.1)
10-min
3.91
4.54
5.14
5.81
6.44
6.98
7.44
7.85
8.30
8.71
(3.59-4.28)
(4.16-4.95)
(4.71-5.60)
(5.31-6.33)
(5.86-7.01)
(6.32-7.61)
(6.70-8.10)
(7.02-8.57)
(7.37-9.08)
(7.67-9.55)
3.26
3.80
4.34
4.90
5.44
5.89
6.27
6.60
6.96
7.29
15-min
(2.99-3.57)
(3.49-4.15)
(3.97-4.73)
(4.48-5.34)
(4.95-5.93)
(5.33-6.42)
(5.64-6.83)
(5.90-7.21)
(6.18-7.62)
(6.42-7.99)
30-min
2.24
2.63
3.08
3.55
4.03
4.43
4.80
5.14
5.54
5.90
(2.05-2.45)
(2.41-2.87)
(2.82-3.36)
(3.25-3.87)
(3.67-4.39)
(4.02-4.84)
(4.32-5.23)
(4.60-5.61)
(4.92-6.06)
(5.19-6.47)
1.39
1.65
1.97
2.31
2.68
3.00
3.31
3.60
3.98
4.31
60-min
(1.28-1.53)
(1.51-1.80)
(1.81-2.15)
(2.11-2.52)
(2.44-2.92)
(2.72-3.28)
(2.98-3.60)
(3.22-3.93)
(3.53-4.35)
0.822
0.974
1.18
1.40
1.65
1.87
2.09
2.32
2.61
2.88
2-hr
(0.748-0.904)
(0.888-1.07)
(1.07-1.29)
(1.27-1.53)
(1.48-1.80)
(1.68-2.05)
(1.86-2.28)
(2.05-2.53)
(2.29-2.85)
(2.50-3.16)
0.582 IF
0.691 IF
0.838 IF
1.00
1.19
1.37
1.54
1.72
1.97
2.20
3-hr
(0.528-0.645)
(0.629-0.763)
(0.762-0.927)
(0.905-1.10)
1 (1.07-1.31)
1 (1.22-1.50)
1 (1.36-1.69)
1 (1.51-1.89)
1 (1.71-2.16)
1 (1.89-2.42)
0.349
0.414
0.504
0.602
0.719
0.829
0.939
1.06
1.21
1.36
6-hr
(0.317-0.387)
(0.377-0.458)
(0.457-0.557)
(0.545-0.664)
(0.647-0.791)
(0.741-0.911)
(0.832-1.03)
(0.926-1.16)
1 (1.05-1.33)
0.204
0.242
0.296
0.355
0.428
0.497
0.566
0.641
0.745
0.844
12-hr
(0.187-0.225)
(0.222-0.266)
(0.270-0.326)
(0.323-0.390)
(0.387-0.469)
(0.446-0.542)
(0.503-0.617)
(0.563-0.699)
(0.644-0.812)
(0.719-0.922)
0.121
0.146
0.184
0.214
0.255
0.289
0.323
0.360
0.411
0.452
24-hr
(0.113-0.130)
(0.137-0.157)
(0.172-0.197)
(0.199-0.229)
(0.237-0.273)
(0.267-0.310)
(0.298-0.347)
(0.330-0.387)
(0.374-0.443)
(0.409-0.489)
0.070
0.085
0.106
0.122
0.145
0.164
0.183
0.203
0.230
0.252
2-day
(0.066-0.075)
(0.080-0.090)
(0.099-0.113)
(0.114-0.131)
(0.135-0.155)
(0.152-0.175)
(0.169-0.195)
(0.186-0.217)
(0.210-0.248)
(0.229-0.273)
0.050
0.060
0.074
0.086
0.101
0.114
0.127
0.141
0.160
0.175
3-day
(0.047-0.053)
(0.056-0.064)
(0.070-0.079)
(0.080-0.091)
(0.095-0.108)
(0.106-0.122)
(0.118-0.136)
(0.130-0.151)
(0.146-0.172)
(0.159-0.188)
0.039
0.047
0.058
0.067
0.080
0.089
0.100
0.110
0.125
0.137
4-day
(0.037-0.042)
(0.044-0.050)
(0.055-0.062)
(0.063-0.071)
(0.074-0.084)
(0.083-0.095)
(0.092-0.106)
(0.101-0.117)
(0.114-0.133)
(0.124-0.146)
0.026
0.031
0.038
0.044
0.051
0.057
0.064
0.070
0.079 7
0.086
7-day
(0.025-0.028)
(0.029-0.033)
(0.036-0.040)
(0.041-0.046)
(0.048-0.054)
(0.053-0.061)
(0.059-0.068)
(0.065-0.075)
(0.072-0.085)
(0.078-0.093)
0.021
0.025
0.030
0.034
0.039
0.044
0.048
0.053
0.059
0.064
10-day
(0.020-0.022)
(0.023-0.026)
(0.028-0.032)
(0.032-0.036)
(0.037-0.042)
(0.041-0.046)
(0.045-0.051)
(0.049-0.056)
(0.054-0.063)
(0.058-0.068)
0.014
0.016
0.020
0.022
0.025
0.028
0.031
0.033
0.037
0.040
20-day
(0.013-0.015)
(0.016-0.017)
(0.018-0.021)
(0.021-0.023)
(0.024-0.027)
(0.026-0.030)
(0.029-0.032)
(0.031-0.035)
(0.034-0.039)
(0.037-0.043)
0.012
0.014
0.016
0.018
0.020
0.022
0.024
0.025
0.028
0.030
30-day
(0.011-0.012)
(0.013-0.014)
(0.015-0.017)
(0.017-0.019)
(0.019-0.021)
(0.020-0.023)
(0.022-0.025)
(0.024-0.027)
(0.026-0.029)
(0.028-0.032)
0.010
0.011
0.013
0.014
00-1 6-1
FOUR7
0.019
0.020
0.022
0.023
45-day
(0.009-0.010)
(0.011-0.012)
(0.012-0.014)
(0.014-0.015)
(0.015-0.017)
(0.017-0.018)
(0.018-0.020)
(0.019-0.021)
(0.020-0.023)
(0.022-0.024)
0.009
0.010
o--0-1 2-1
Fomfi3
0.014
0.015
0.016
0.017
0.018
0.019
60-day
(0.008-0.009)
(0.010-0.011)
(0.011-0.012)
(0.012-0.013)
(0.013-0.015)
(0.014-0.016)
(0.015-0.017)
(0.016-0.018)
(0.017-0.019)
(0.018-0.020)
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.
Back to Top
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=36.0827&lon=-78.3189&data... 7/1/2021
APPENDIX B ISTORMWATER NETWORK DESIGN
BOHLERI
BOHLER ENGINEERING NC, PLLC
Start Node
Stop Node
Invert (Start) (ft)
Invert (Stop) (ft)
Length (Unified) (ft)
Upstream Inlet C
Upstream Inlet Area (acres)
System Intensity (in/h)
Flow (cfs)
Capacity (Full Flow) (cfs)
Velocity (ft/s)
Slope (Calculated) (%)
110
EX-1
282.89
282
29.6
0.76
0.29
7.133
5.78
14.54
11.17
3
111
110
293.35
283.5
151.9
0.93
0.25
7.26
1.7
21.39
10.41
6.49
120
110
287.18
283.21
132.3
0.89
0.17
7.204
2.63
14.54
8.99
3
130
120
290
287.4
86.7
0.89
0.36
7.26
1.38
14.54
7.46
3
150
EX-2
293.79
293.45
67.2
0.58
0.26
7.073
1.74
5.94
4.21
0.5
160
150
294.51
293.89
125
0.55
0.17
7.26
0.68
5.94
3.22
0.5
c
0
m
LU
295.00
290.00
285.00
280.00
Profile Report
Engineering ProR/e - 01-130 (NCR211506 - Louisburg Annex stsw)
130
p: ,.,., . Or) A 1 1 w
-0+50 0+00 0+50 1+00 1+50 2+00 2+50 3+00
Station (ft)
StormCAD
NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04]
7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1
755-1666
Profile Report
Engineering Profile ® 110 111 (NCR211506 ® Louisburg Annex. stsw)
300.00
295.00
f••1 11
285.00
f•:1 11
111
-0+50 0+00 0+50 1+00 1+50 2+00
Station (ft)
StormCAD
NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04]
7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1
755-1666
W
300.00
295.00
290.00
DIX11
Profile Report
Engineering Profile - ®Z - 160 (NCR211606 - Louisburg Annex stsw)
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Station (ft)
HKiIIIJ
1 +50
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Rim: 298.24 ft
Invert:294.51 fi
N11111
StormCAD
NCR211506 - Louisburg Annex.stsw Bentley Systems, Inc. Haestad Methods Solution Center [10.03.02.04]
7/2/2021 27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203- Page 1 of 1
755-1666