HomeMy WebLinkAboutSW5200501_SW Report_20201006Stormwater Impact Analysis for
Coolwick Warehouse
80 Weathers Street
Youngsville, North Carolina
May 4, 2020
Revised: October 5, 2020
Prepared for:
Coolwick, LLC
186 Wind Chime Court # 200
Raleigh, North Carolina 27615
PRINT NAME: Josh Crumpler, P.E.
SIGNATURE:
REGISTRATION NO. PE-034994
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CRUMPLER
Consulting Services, PLLC
Prepared by Crumpler Consulting Services, PLLC
2308 Ridge Road, Raleigh, North Carolina 27612
p 1 919.413-1704
CRUMPLER
Consulting Services, PLLC
TABLE OF CONTENTS
1.0 STORMWATER NARRATIVE...............................................................................................2
2.0 DESIGN DATA AND METHODOLOGY................................................................................3
3.0 PRE -DEVELOPMENT STORMWATER RUN-OFF...............................................................4
4.0 POST -DEVELOPMENT STORMWATER RUN-OFF.............................................................5
List of Appendices
Appendix A — IDF Rainfall Data
Appendix B — SCM Sizing Calculations, Supplement EZ Form, and SNAP Tool Calculations
Appendix C — Pre -Development Peak Flow Tables (2-yr, 10-yr, and 100-yr)
Appendix D — Post -Development Peak Flow Tables (2-yr, 10-yr, and 100-yr)
Appendix E — Wetlands and Stream Map
Appendix F — Drainage Area Maps
2308 Ridge Road I Raleigh, NC 27612 1 p: 919-413-1704 1 e: josh@crumplerconsuIting.com
1.0
STORMWATER NARRATIVE
Coolwick, LLC is proposing to construct two warehouses and three storage units on a parcel
totaling 4.80 acres located at 80 Weathers Street, Youngsville, North Carolina that zoned
Industrial (IND). This report represents the stormwater management design and hydrologic model
results for the proposed project.
As part of the stormwater design, Crumpler Consulting is proposing the installation of a wet
detention basin. The wet detention basin has been designed to control and treat the estimated
runoff generated from the first inch of rainfall per the requirements of the Neuse Watershed
Nutrient Management Strategy and the NCDEQ's stormwater management design manual. The
dry detention facility is anticipated to attenuate the peak flow rates for the 2-year, 10-year, and
100-year 24-hour storm events in accordance with NCDEQ's requirements. The nitrogen loading
rates have been evaluated as part of this design and are anticipated to be reduced to acceptable
rates through treatment by the detention facility and buy down methods.
The existing parcel did have minimal existing impervious surfaces that included an existing
driveway which totaled 16,016sf (0.37 acres). The proposed impervious surface consists of the
warehouse building, parking lot, driveways, and sidewalks. The proposed impervious area will
total 64,677sf (1.48 acres). The proposed grading conveys the majority of the runoff to the
southwest corner of the site, where the runoff is collected in a swale which empties into the dry
detention basin that discharges to the south west side of the site. The Post -Development
Drainage Map shows the stormwater grading and drainage plan and associated details.
Page 2 September 15, 2020
2.0
DESIGN DATA AND METHODOLOGY
The design of the proposed stormwater facilities was performed in accordance with the NCDEQ
Stormwater SCM Manual. The site was designed to meet Runoff Treatment by utilizing a wet
detention basin. It was sized using both Parts `B' and `C' of the stormwater design manual along
with the Supplement-EZ form and SNAP tool provided by NCDEQ.
In addition to the NCDEQ Stormwater SCM Manual, the Wet Pond was analyzed using Hydraflow
Hydrographs. This software is a computer modeling software package, was used for the analysis
of stormwater routing and hydrology of the existing and proposed watersheds. The hydrology
calculations were performed using the Modified Ration Method and TR-55 methods. Franklin
County lies within the Type II rainfall distribution. The rainfall amounts for the site were obtained
from National Oceanic and Atmospheric Administration (NOAA) and are included in Appendix A.
The stormwater analyses performed for this project include the 2-year, 10-year, and 100-year,
24-hour storm events.
The Soil Survey of Franklin County, North Carolina, completed by the National Resource
Conservation Service (NRCS), was reviewed for general information on the soils within the site
area.
Page 3 September 15, 2020
3.0
PRE -DEVELOPMENT STORMWATER RUNOFF
The pre -development drainage areas were determined using site visits, visual observations, and
surveyed topographic data. The peak flow rates for the specified storm events are based on
topography, land use cover (such as open space, grass, woods), and soil type. Two drainage
points were selected for analysis.
The existing 3.42-acre watershed was modeled in HydraFlow as one subcatchment, as described
below. Refer to Appendix F of this report for the pre -development watershed map.
• Subcatchment 1
Subcatchment 1 is 3.42 acres and drains to the southwest corner of the property. A time of
concentration was calculated and was found to be approximately 5 minutes. Therefore, 5 minutes
was estimated as the time of concentration for this subcatchment.
The HydroFlow analysis can be found in Appendices. The table below summarizes the hydrologic
model results for pre -development peak flow rates of the existing 3.42-acre watershed.
PRE -DEVELOPMENT STORMWATER RUNOFF
STORM EVENT
PRE -DEVELOPMENT PEAK FLOW
2-YEAR
6.049 CFS
10-YEAR
7.835 CFS
100-YEAR
10.750 CFS
Page 4 September 15, 2020
4.0
POST -DEVELOPMENT STORMWATER RUNOFF
An analysis of the post -development runoff was performed using the same methods, parameters,
and assumptions as described in the pre -development analysis above. Based upon the
calculations, the project reduces the nitrogen loading to acceptable levels for buy -down and does
not create an increase in the peak runoff rate for the 2-year,10-year, and 100-year storm events.
This will be achieved by constructing appropriate SCMs.
The proposed site was divided into two subcatchments for post -development analysis. The
subcatchments are described below. Refer to Appendix F of this report for the post -development
watershed map.
• Drainage Area 1
Drainage Area 1 is 2.13 acres and includes runoff is treated by the dry detention facility.
Runoff that is treated by the dry detention facility is collected in swale and discharged
overland in the southwestern corner of the site. A time of concentration was calculated
and was found to be lower than 5 minutes. Therefore, 5 minutes was estimated as the
time of concentration for this subcatchment.
• Drainage Area 2 (Bypass)
Drainage Area 2 is 1.29 acres and drains offsite to the south bypassing the dry detention
facility. A time of concentration was calculated and was found to be lower than 5 minutes.
Therefore, 5 minutes was estimated as the time of concentration for this subcatchment.
The HydraFlow analysis can be found in Appendices. The follow table summarizes the hydrologic
model results for post -development peak flow rates of the 1.91-acre watershed.
POST -DEVELOPMENT STORMWATER RUNOFF
TOTAL
TOTAL
STORM EVENT
POST -DEVELOPMENT
POST -DEVELOPMENT
PEAK FLOW
PEAK FLOW
WITH OUT SCM
WITH SCM
2-YEAR
9.71 CFS
2.497 CFS
10-YEAR
12.58 CFS
3.273 CFS
100-YEAR
17.25 CFS
4.529 CFS
Page 5 September 15, 2020
APPENDIX A
IDF Rainfall Data
Page 6 September 15, 2020
HPUIfkiilYkel
Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
Location name: Youngsville, North Carolina, USA*
Latitude: 36.0289*, Longitude:-78.4984.
Elevation: 424.95 ft**
*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 I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1
Duration
Average recurrence interval (years)
1
2
5
10
25
50
1 100
100
200
500
1000
0.404
0.470
0.538
0.602
0.667
0.717
0.762
0.801
0.844
0.881
5-min
(0.372-0.440)
(0.433-0.512)
(0.495-0.585)
(0.552-0.654)
(0.609-0.724)
(0.651-0.779)
(0.688-0.827)
(0.719-0.872)
(0.752-0.919)
(0.778-0.961)
0.645
0.752
0.862
0.962
1.06
1.14
1.21
1.27
1.34
1.39
10-min
(0.595-0.702)
(0.693-0.819)
(0.792-0.937)
(0.882-1.05)
(0.970-1.15)
1 (1.04-1.24)
1 (1.09-1.31)
1 (1.14-1.38)
1 (1.19-1.45)
1 (1.23-1.51)
0.807
0.946
1.09
1.22
1.35
1.45
1.53
1.60
1.68
1.74
15-min
(0.744-0.878)
(0.871-1.03)
(1.00-1.19) 1
1 (1.23-1.46)
1 (1.31-1.57)
1 (1.38-1.66)
1 (1.44-1.74)
1 (1.50-1.83)
1 (1.54-1.90)
1.11
1.31
1.55
1.76
2.00
2.18
2.34
2.49
2.67
2.82
30-min
(1.02-1.20)
(1.20-1.42)
(1.42-1.68)
(1.62-1.92)
(1.82-2.17)
(1.98-2.37)
(2.12-2.54)
(2.24-2.71)
(2.38-2.91)
(2.49-3.08)
1.38
1.64
1.99
2.30
2.66
2.95
3.23
3.50
3.84
4.12
60-min
(1.27-1.50) 11
(1.51-1.79) 11
(1.83-2.16) 11
(2.11-2.50)
(2.43-2.89)
(2.68-3.21)
(2.92-3.50)
(3.14-3.81)
(3.42-4.18)
(3.64-4.49)
1.62
1.93
2.36
2.76
3.23
3.64
4.03
4.43
4.94
5.38
2-hr
(1.48-1.77) 11
(1.77-2.11) 11
(2.16-2.58) 1
1 (2.92-3.52)
1 (3.28-3.96)
1 (3.61-4.39)
1 (3.93-4.82)
1 (4.35-5.38)
1 (4.70-5.88)
1.72
2.05
2.52
2.96
3.50
3.98
4.45
4.94
5.59
6.17
3-hr
(1.57-1.90)1
(1.88-2.26)
1 (2.69-3.25) 11
(3.16-3.84)
1 (3.57-4.36)
1 (3.96-4.88)
1 (4.36-5.41)
1 (4.88-6.12)
1 (5.33-6.77)
2.06
2.46
3.02
3.56
4.23
4.83
5.42
6.05
6.89
7.64
6-hr
(1.88-2.28) 11
(2.25-2.71) 11
(2.75-3.33)
(3.24-3.91) 11
(3.82-4.64)
1 (4.33-5.28)
1 (4.83-5.93)
1 (5.33-6.60)
1 (5.99-7.52)
1 (6.56-8.36)
2.43
2.90
3.58
4.24
5.08
5.83
6.60
7.42
8.54
9.55
12-hr
(2.23-2.67) 11
(2.67-3.18) 11
(3.29-3.93)
1 (4.61-5.55)
1 (5.26-6.35)
1 (5.88-7.1 7)
1 (6.54-8.05)
1 (7.41-9.27)
1 (8.16-10.4)
2.87
3.47
4.34
5.02
5.95
6.68
7.43
8.20
9.26
10.1
24-hr
(2.68-3.09)
1 (4.05-4.66)
(4.68-5.39) 11
(5.53-6.38)
1 (6.19-7.17)
1 (6.87-7.98)
1 (7.55-8.81)
1 (8.49-9.95)
1 (9.20-10.9)
3.34
4.01
4.99
5.74
6.76
7.56
8.37
9.21
10.3
11.2
2-day
(3.12-3.58)
(3.76-4.31) 11
(4.66-5.35)
1 (6.28-7.25)
1 (7.01-8.11)
1 (7.74-8.99)
1 (8.48-9.90)
1 (9.47-11.1)
1 (10.2-12.1)
3.53
4.24
5.25
6.03
7.09
7.93
8.78
9.66
10.9
11.8
3-day
(3.31-3.78)
1 (5.63-6.45) 11
(6.60-7.59)
1 (7.36-8.49)
1 (8.13-9.41)
1 (8.90-10.4)
1 (9.95-11.7)
1 (10.8-12.7)
3.73
4.47
5.51
6.32
7.43
8.31
9.20
10.1
11.4
12.3
4-day
(3.49-3.99)
(4.19-4.78)
(5.15-5.88)1
(5.90-6.75) 11
(6.92-7.94)
1 (7.71-8.88)
1 (8.51-9.84)
1 (9.33-10.8)
1 (10.4-12.2)
1 (11.3-13.3)
4.32
5.16
6.27
7.15
8.36
9.31
10.3
11.3
12.6
13.7
7-day
(4.06-4.62) 11
(4.84-5.50)
1 (7.80-8.92)
(8.66-9.94)
1 (9.54-11.0)
1 (10.4-12.1)
1 (11.6-13.6)
1 (12.6-14.8)
4.91
5.85
7.02
7.95
9.19
10.2
11.2
12.2
13.5
14.6
10-day
(4.62-5.24) 11
(5.49-6.23) 11
(6.59-7.48) 11
(7.45-8.46) 11
(8.59-9.79)
1 (9.48-10.8)
1 (10.4-11.9)
1 (11.3-13.0)
1 (12.5-14.5)
1 (13.4-15.6)
6.59
7.77
9.18
10.3
11.8
13.0
14.2
15.4
17.1
18.4
20-day
(6.21-7.00) 1
1 (8.65-9.74) 11
(9.69-10.9) 11
(11.1-12.5)
(12.2-13.8)
(13.2-15.1)
(14.3-16.4)
(15.8-18.2)
(16.9-19.7)
8.17
9.62
11.2
12.4
14.0
15.2
16.4
17.7
19.3
20.5
30-day
(7.73-8.66)
(9.09-10.2) 1
1 (13.2-14.8)
(14.3-16.1)
(15.4-17.5)
(16.5-18.8)
(17.9-20.5)
(19.0-21.9)
10.4
12.2
13.9
15.3
17.1
18.4
19.7
21.0
22.7
24.0
45-day
(9.89-11.0)
(11.6-12.8)
(13.2-14.7)
(14.5-16.1)
(16.2-18.0)
1 (17.4-19.4)
1 (18.6-20.8)
1 (19.8-22.2)
1 (21.3-24.1)
1 (22.4-25.5)
12.5
14.6
16.5
17.9
19.8
21.2
22.5
23.9
25.6
26.8
60-day
(11.9-13.1)
(13.9-15.3)
(15.7-17.3)
(17.0-18.8)
(18.8-20.8)
(20.1-22.3)
(21.3-23.7)
(22.5-25.2)
(24.1-27.0)
(25.2-28.4)
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
PF graphical
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=36.0289&Ion=-78.4984&data=depth&units=english&series=pds 1 /4
4/29/2020 Precipitation Frequency Data Server
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PDS-based depth -duration -frequency (DDF) curves
Latitude: 36.4289", Longitude: -78.4984"
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1 2 5 10 25 50 100 200 500 1000
Average recurrence interval (years)
NOAAAtlas 14, Volume 2, Version 3 Created (GMT): Wed Apr 29 10:51:00 2020
Back to Top
Maps & aerials
Small scale terrain
Average recurrence
mlerva I
{years}
— 1
2
— 5
— 10
— 25
50
100
200
500
1000
Duration
— 6-min —
2-day
— 10-min —
3-day
15-min —
4-dmy
— 30-min —
7-day
— 60-min —
10-day
— 2fir —
20-day
— 3-rr —
30-day
— Sfir —
45-day
— 12-h r —
60-day
24-Mr
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.htmI?Iat=36.0289&Ion=-78.4984&data=depth&units=engIish&series=pds 2/4
HPUIfkiilYkel
Precipitation Frequency Data Server
NOAA Atlas 14, Volume 2, Version 3
Location name: Youngsville, North Carolina, USA*
Latitude: 36.0289*, Longitude:-78.4984.
Elevation: 424.95 ft**
*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 I PF graphical I Maps & aerials
PF tabular
PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches/hourp
Duration
Average recurrence interval (years)
1
2
5
10
25
50
1 100
100
200
500
1000
5-min
4.85
(4.46-5.28)
5.64
(5.20-6.14) 11
6.46
(5.94-7.02)
7.22
8.00
1 (7.31-8.69)
8.60
1 (7.81-9.35)
9.14
1 (8.26-9.92)
9.61
1 (8.63-10.5)
10.1
1 (9.02-11.0)
10.6
1 (9.34-11.5)
3.87
4.51
5.17
5.77
6.38
6.85
7.27
7.61
8.01
8.33
10-min
(3.57-4.21)
1 (5.82-6.92)
1 (6.23-7.44)
1 (6.56-7.88)
1 (6.83-8.29)
1 (7.13-8.72)
1 (7.36-9.08)
3.23
3.78
4.36
4.87
5.39
5.78
6.12
6.40
6.72
6.97
15-min
(2.98-3.51) 11
(3.48-4.12) 11
(4.01-4.74) 11
(4.46-5.29) 11
(4.92-5.85)
1 (5.26-6.28)
1 (5.53-6.64)
1 (5.75-6.97)
1 (5.99-7.32)
1 (6.15-7.60)
2.21
2.61
3.10
3.53
3.99
4.35
4.69
4.99
5.35
5.64
30-min
(2.04-2.41)1
(2.41-2.85) 11
(2.85-3.37) 11
(3.23-3.83) 11
(3.64-4.33)
1 (3.96-4.73)
1 (4.24-5.09)
1 (4.48-5.43)
1 (4.76-5.83)
1 (4.98-6.15)
1.38
1.64
1.99
2.30
2.66
2.95
3.23
3.50
3.84
4.12
60-min
(1.27-1.50) 11
(1.51-1.79) 11
(1.83-2.16) 11
(2.11-2.50) 11
(2.43-2.89)
1 (2.68-3.21)
1 (2.92-3.50)
1 (3.14-3.81)
1 (3.42-4.18)
1 (3.64-4.49)
0.809
F 0.965
1.18
1.38
1.62
1.82
2.02
2.21
2.47
2.69
2-hr
(0.739-0.887)
(0.884-1.05) 11
(1.08-1.29) 11
(1.25-1.51) 11
(1.46-1.76)
1 (1.64-1.98)
1 (1.80-2.19)
1 (1.97-2.41)
1 (2.17-2.69)
1 (2.35-2.94)
0.572
0.683
0.837
0.985
1.17
1.33
1.48
1.65
1.86
2.05
3-hr
(0.521-0.631)
(0.624-0.752)
(0.764-0.923)
(0.895-1.08)
(1.05-1.28)
1 (1.19-1.45)
1 (1.32-1.62)
1 (1.45-1.80)
1 (1.63-2.04)
1 (1.77-2.25)
0.344
0.410
0.504
0.594
0.707
F 0.806
F 0.906
1.01
1.15
1.28
6-hr
(0.314-0.380)
(0.376-0.452)
(0.460-0.555)
(0.541-0.653)
(0.638-0.774)
(0.723-0.882)
(0.806-0.991)
(0.889-1.10)
1 (1.00-1.25)
1 (1.10-1.40)
0.201
0.241
0.297
0.352
0.422
0.484
0.548
0.615
0.708
F 0.793
12-hr
(0.185-0.222)
(0.222-0.264)
(0.273-0.326)
(0.322-0.386)
(0.383-0.461)
(0.436-0.527)
(0.488-0.595)
(0.543-0.668)
(0.615-0.769)
(0.678-0.862)
0.120
0.144
0.181
0.209
0.248
0.278
0.310
0.342
0.386
0.420
24-hr
(0.112-0.129)
(0.135-0.155)
(0.169-0.194)
(0.195-0.224)
(0.230-0.266)
(0.258-0.299)
(0.286-0.332)
(0.315-0.367)
(0.354-0.415)
(0.383-0.452)
0.069
0.084
0.104
0.120
0.141
0.157
0.174
0.192
0.215
0.234
2-day
(0.065-0.075)
(0.078-0.090)
(0.097-0.111)
(0.112-0.128)
(0.131-0.151)
(0.146-0.169)
(0.161-0.187)
(0.177-0.206)
(0.197-0.232)
(0.213-0.252)
0.049
0.059
0.073
0.084
0.099
0.110
0.122
0.134
0.151
0.164
3-day
(0.046-0.053)
(0.055-0.063)
(0.068-0.078)
(0.078-0.090)
(0.092-0.105)
(0.102-0.118)
(0.113-0.131)
(0.124-0.144)
(0.138-0.162)
(0.149-0.176)
0.039
0.047
0.057
0.066
0.077
0.087
0.096
0.105
0.118
0.129
4-day
(0.036-0.042)
(0.044-0.050)
(0.054-0.061)
(0.061-0.070)
(0.072-0.083)
(0.080-0.093)
(0.089-0.103)
(0.097-0.113)
(0.109-0.127)
(0.118-0.138)
0.026
0.031
0.037
0.043
0.050
0.055
0.061
0.067
0.075
0.082
7-day
(0.024-0.027)
(0.029-0.033)
(0.035-0.040)
(0.040-0.045)
(0.046-0.053)
(0.052-0.059)
(0.057-0.065)
(0.062-0.072)
(0.069-0.081)
(0.075-0.088)
0.020
0.024
0.029
0.033
0.038
0.042
0.046
0.051
0.056
0.061
10-day
(0.019-0.022)
(0.023-0.026)
(0.027-0.031)
(0.031-0.035)
(0.036-0.041)
(0.040-0.045)
(0.043-0.050)
(0.047-0.054)
(0.052-0.060)
(0.056-0.065)
0.014
0.016
0.019
0.021
0.025
0.027
0.030
0.032
0.036
0.038
20-day
(0.013-0.015)
(0.015-0.017)
(0.018-0.020)
(0.020-0.023)
(0.023-0.026)
(0.025-0.029)
(0.028-0.031)
(0.030-0.034)
(0.033-0.038)
(0.035-0.041)
0.011
0.013
0.016
0.017
0.019
0.021
0.023
0.025
0.027
0.028
30-day
(0.011-0.012)
(0.013-0.014)
(0.015-0.016)
(0.016-0.018)
(0.018-0.021)
(0.020-0.022)
(0.021-0.024)
(0.023-0.026)
(0.025-0.029)
(0.026-0.030)
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)
(0.012-0.014)
(0.013-0.015)
(0.015-0.017)
(0.016-0.018)
(0.017-0.019)
(0.018-0.021)
(0.020-0.022)
(0.021-0.024)
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)
(0.010-0.011)
(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)
(0.018-0.020)
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
PF graphical
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=36.0289&Ion=-78.4984&data=intensity&units=english&series=pds 1 /4
4/29/2020
I161616I6161
10.000
C
41
1.000
C
GJ
a-�
C
Precipitation Frequency Data Server
PD5-based intensity -duration -frequency (IDF) curves
Latitude: 36.0289`, Longitude: -73-4984'
TT I I I I I T I I I I I I I I I
0.001
t t
Jr t
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N rq
rq
rq
N rq
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Duration
100.000
e
0.100
4-1
49
0.010
0.001 i 1 _ I I I I I
1 2 5 10 25 50 100 200 500 1000
Average recurrence interval (years)
NOAA Atlas 14, Volume 2, Version 3 Created (GMT): Wed Apr 29 10:52:43 2020
Back to Top
Maps & aerials
Small scale terrain
Average recurrence
mlerva I
{years}
— 1
2
— 5
— 10
— 25
50
100
200
500
1000
Duration
— 6-min —
2-day
— 10-min —
3-day
15-min —
4-dmy
— 30-min —
7-day
— 60-min —
10-day
— 2fir —
20-day
— 3-hr —
30-day
— Sfir —
45-day
— 12-h r —
60-day
24-Mr
https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.htmI?Iat=36.0289&Ion=-78.4984&data=intensity&units=english&series=pds 2/4
APPENDIX B
SCM Sizing Calculations, Supplement EZ Form, and SNAP Tool Calculations
Page 7 September 15, 2020
COO( v*,c)L W.,.C,"usc wc. p.J 3
uPbA AttiA
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It•1—k C" = Gct, Gb7Sf
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A)(,uJ (3OA C>/c,,t\ 1J.:,,c — 35, $gZS�- - /GO14 = 111 8,)&
701�1 S:►t_ ���;Ia;,.SS - 25, tioo S+
lo�� = 43G5o s�
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ay.•.0."A >
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4 0.1
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a:e�.r...�i'[•bye- � (oo� 72.oY %3� -� 2.2Z
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215Jc,C 3%3 51,,•.5� '(�blc�
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'3 • Y� f� , 2. -LI 4 -f . S f -� - z -. .2 ft
2SiO'AA6Al7 5roa'16&-
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2-Y RkZ41c•-
/s e_ 5551 cr-
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2 •y47A-05)
Css )
3/3
Impervious" Surface Area
Drainage Area 1(SF)
Buildings
25,400
Streets
16,974
Parking
2,705
Sidewalks
669
Existing BUA
12,633
Total
58,381
MAIN POOL
STORAGE TABLE
Stage
SURFACE AREA (SF)
Volume (CF)
392
2,456
-
393
2,723
2,590
394
2,997
2,860
395
3,280
3,139
396
3,570
3,424
Total
12,013
FOREBAY STORAGE TABLE
Stage
SURFACE AREA (SF)
Volume (CF)
393
629
-
394
738
684
395
855
797
396
979
917
Total
2,397
TEMPORARY POOL STORAGE TABLE
Stage
SURFACE AREA (SF)
Volume (CF)
396
4,548
-
397
6,793
5,633
397.5
7,570
3,589
398
7,608
3,793
iTotal
13,015
DESIGN OF RIPRAP OUTLET PROTECTION - SINGLE PIPE
Single Pipe Outlet
Project Coolwick Warehouse
Date 22-Sep-20
Project No. 19029
Designer Josh C.
Pipe and Flow Data
Outlet ID
CHANNEL 1 INLET
Channel Area
10 in.
Pipe slope
1.00%
Outlet flowrate
2.7 cfs
Source of flowrate data Hydraflow Express
Outlet velocity
4.1 ft/sec
Source of velocity data Hydraflow Express
Outlet pipe downstream inv.
398.00
Tailwater elevation
398.47
Source of TW elev. Hydraflow Express
Zone from graph below =
1
Fieure 8.06.b.1
25
20 Zon 7
V
Y
15
w
V
10 ne 5
0 4 e4 5
3
0 1 2 3 4 5 6 7 Zcpe 2 9 10
Pipe diameter (ft)
NCDOT Class A Riprap - 3.5' L x 2.5' W x 9"Thick
Zone
Material
Diameter
Thickness
Length
Width
1
Class A
3
9
4 x D(o)
3 x D(o)
2
Class B
6
22
6 x D(o)
3 x D(o)
3
Class I
13
22
8 x D(o)
3 x D(o)
4
Class I
1 13
1 22
1 8 x D(o)
3 x D(o)
5
Class II
23
27
10 x D(o)
3 x D(o)
6
Class II
23
27
10 x D(o)
3 x D(o)
7
Special study required
1. Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
Coolwick_Riprap Energy Dissipators.xls
9/22/2020
DESIGN OF RIPRAP OUTLET PROTECTION - SINGLE PIPE
Single Pipe Outlet
Project Coolwick Warehouse
Date 22-Sep-20
Project No. 19029
Designer Josh C.
Pipe and Flow Data
Outlet ID
CHANNEL 1 INLET
Channel Area
21 in.
Pipe slope
1.00%
Outlet flowrate
2.7 cfs
Source of flowrate data Hydraflow Express
Outlet velocity
4.1 ft/sec
Source of velocity data Hydraflow Express
Outlet pipe downstream inv.
398.00
Tailwater elevation
398.47
Source of TW elev. Hydraflow Express
Zone from graph below =
1
Fieure 8.06.b.1
25
20 Zon 7
V
Y
15
w
V
10 ne 5
e4 5
3
0
0 1 2 3 4 5 6 7 Zcpe 2 9 10
Pipe diameter (ft)
NCDOT Class A Riprap - 7' L x 5.25' W x 9"Thick
Zone
Material
Diameter
Thickness
Length
Width
1
Class A
3
9
4 x D(o)
3 x D(o)
2
Class B
6
22
6 x D(o)
3 x D(o)
3
Class I
13
22
8 x D(o)
3 x D(o)
4
Class I
1 13
1 22
1 8 x D(o)
3 x D(o)
5
Class II
23
27
10 x D(o)
3 x D(o)
6
Class II
23
27
10 x D(o)
3 x D(o)
7
Special study required
1. Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
Coolwick_Riprap Energy Dissipators.xls
9/22/2020
DESIGN OF RIPRAP OUTLET PROTECTION - SINGLE PIPE
Single Pipe Outlet
Project Coolwick Warehouse
Date 22-Sep-20
Project No. 19029
Designer Josh C.
Pipe and Flow Data
Outlet ID
Pond Outlet
Pipe diameter
12 in.
Pipe slope
1.00%
Outlet flowrate
0.6 cfs
Source of flowrate data Hydraflow
Outlet velocity
2.0 ft/sec
Source of velocity data Hydraflow
Outlet pipe downstream inv.
389.75
Tailwater elevation
390.10
Source of TW elev. Hydraflow
Zone from graph below =
1
Fieure 8.06.b.1
25
20 Zon 7
V
Y
15
w
V
10 ne 5
5 e4
3
0
0 1 2 3 4 5 6 7 z9pe 2 9 10
Pipe diameter (ft)
NCDOT Class A Riprap - 4' L x Y W x 9"Thick 11
Zone
Material
Diameter
Thickness
Length
Width
1
Class A
3
9
4 x D(o)
3 x D(o)
2
Class B
6
22
6 x D(o)
3 x D(o)
3
Class I
13
22
8 x D(o)
3 x D(o)
4
Class I
1 13
1 22
1 8 x D(o)
3 x D(o)
5
Class II
23
27
10 x D(o)
3 x D(o)
6
Class II
23
27
10 x D(o)
3 x D(o)
7
Special study required
1. Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
Coolwick_Riprap Energy Dissipators.xls
9/22/2020
Project Information
Project Name:
Submission Date:
Project Area (ft):
Disturbed Area (ft):
Development Land Use Type:
Development Activity Type:
Designated Downtown Area?
Project Location/Address:
County:
Local Jurisdiction:
Project Latitude Coordinates:
Project Longitude Coordinates:
Precipitation Station:
Physiographic Region:
Nutrient Management Watershed:
Subwatershed:
Phosphorus Delivery Zone:
Nitrogen Delivery Zone:
Project Designer and Contact Phone
Number / Email:
Part of Common Development Plan?
Project Owner Type:
Project Description:
Coolwick Warehouse
07/16/2020
209,089
145,490
Commercial
Development - New
no
80 Weathers Street
Franklin
Youngsville
36D 01M 45.045
78D 29M 55.235
Neuse
Piedmont
Neuse
Neuse - 03020201
Neuse - Upper
Neuse - Upper
ft2
ft2
N
W
osh Crumpler 919-413-1704 josh@crumplerconsul
no
Private
Construction of two 10,OOOsf wareh,
R = 0.05+(0.009 *1)
where I = percent impervious (%)
Average Annual Pollutant Load, L
L=(Pi *R *(P/12))*(C*A*2.72)
where C = event mean concentration (mg/L)
Project Area Land Cover Characteristics
PROJECT AREA LAND COVERS
Roof _
Roadway
TN TP
EMC EMC
(mg/L) (mg/L)
Post -
Project
Area (ft)
Pre-
Project
Area (ft)
1.18
0.11
0
25,400
1.64
0.34
16,016
Parking/Driveway/Sidewalk
1.42
0.18
0
39,188
Protected Forest
0.97
0.03
193,073
63,599
Other Pervious/Landscaping
2.48
1.07
74,902
CUSTOM LAND COVER 1
CUSTOM LAND COVER 2
CUSTOM LAND COVER 3
LAND TAKEN UP BY SCM
1.18
0.11
0
6,000
LAND COVER AREA CHECK
Net Change of Land Covers (ft): 145,490
Total Project Area Entered (ft): 209,089
Total Pre -Project Calculated Area (ft2): 209,089
Total Post -Project Calculated Area (ft2): 209,089
Equations Used and Proiect Area Calculations
SIMPLE METHOD Stormwater Runoff Volume Generated, V
Runoff Coefficient R V = Pi * Rv * (P/12) * A
where A = drainage area (ft)
Pj = fraction of rain events with runoff
P = average annual rainfall depth (in)
Pre -Project:
Post -Project:
A = 4.8000
ac
A = 4.8000 ac
P =
45.76
in.
P = 45.76
in.
V =
85350
ft3
V = 254941
ft3
1=
8%
1= 34%
R =0.12
R =0.36
Pj =
0.9
Pj = 0.9
CTN =
1.38
mg/L
CTN = 1.36
mg/L
CTP =
0.22
mg/L
CTP = 0.19
mg/L
LTN =
7.35
Ib/yr
LTN = 21.60
Ib/yr
DTP = 1.17
Ib/yr
DTP = 3.03
Ib/yr
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Nutrient Management Strategy Watershed - Nutrient Offset Credit Reporting Form
Please complete and submit the following information to the local government permitting your development project
to characterize it and assess the need to purchase nutrient offset credits. Contact and rule implementation
information can be found online at.
http://deg.nc.gov/about/divisions/water-resources/planning/nonpoint-source-management/nutrient-offset-
information
PROJECT INFORMATION
Applicant Name: Coolwick, LLC
Project Name: Coolwick Warehouse
Project Address: 80 Weathers Street
Date: (mm/dd/yyyy) 1 9/15/2020
County: Franklin
Pre -Project Built -Upon Area %:
Post -Project Built -Upon Area %:
Development Land Use Type: I Commercial
Development Activity Type: Development - New
7.66% Project Latitude:I 36D 01M 45.04S
30.89% Project Longitude:I 78D 29M 55.23S
WATERSHED INFORMATION
Nutrient Management Watershed:
Neuse
N Offsite Threshold Rate (lb/ac/yr): N/A
Subwatershed:
Neuse - 03020201
P Offsite Threshold Rate (lb/ac/yr): N/A
Nitrogen Delivery Zone:
Neuse - Upper
Nitrogen Delivery Factor: 100%
Phosphorus Delivery Zone:
Neuse - Upper
Phosphorus Delivery Factor: 100%
NUTRIENT OFFSET REQUEST
Nitrogen Load Offset Needs
(A)
(B)
(C)
(D)
(E)
(F)
(G)
(H) (L) (Where
Applicable)
Untreated
Treated
Loading Rate
Reduction
Project Size
Offset
Delivery
State Buy Local Gov't
Loading Rate
Loading Rate
Target
Need
(ac)
Duration (yrs)
Factor (k)
Down Amount Buy Down
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs) Amount (Ibs)
B -C
D'E'F'G
0.00
4.50
3.66
4.50
-0.84
4.8000
30
100%
Phosphorus Load Offset Needs
(A)
(B)
(C)
(D)
(E)
(F)
(G)
(H)
(L) (Where
Applicable)
Untreated
Treated Load
Loading Rate
Reduction
Project Size
Offset
Delivery
State Buy
Local Gov't
Load Rate
Rate
Target
Need
(ac)
Duration (yrs)
Factor (k)
Down Amount
Buy Down
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs/ac/yr)
(Ibs)
Amount (Ibs)
B -C
D'E'F'G
0.63
0.52
0.63
-0.11
4.8000
30
100%
0.00
LOCAL GOVERNMENT AUTHORIZATION
Local Government Name: lY
Staff Name:1 1 Phone:) 1
Staff Email:
Local Government Authorizing Signature:
APPENDIX C
Pre -Development Peak Flow Tables (2-yr, 10-yr, and 100-yr)
Page 8 September 15, 2020
Watershed Model Schematic Hydraflow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12
Project: Coolwick-Existing.gpw
Thursday, 04 / 30 / 2020
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
6.049
1
5
3,629
------
------
------
EXISTING CONDITIONS
Coolwick-Existing.gpw
Return Period: 2 Year
Thursday, 04 / 30 / 2020
3
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
EXISTING CONDITIONS
Hydrograph type
= Mod. Rational
Peak discharge
= 6.049 cfs
Storm frequency
= 2 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 3,629 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.38*
Intensity
= 4.655 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(0.150 x 0.95) + (3.270 x 0.35)] / 3.420
Q (cfs)
7.00
5.00
3.00
1.00
EXISTING CONDITIONS
Hyd. No. 1 -- 2 Year
Q (cfs)
7.00
. We
5.00
4.00
3.00
2.00
1.00
0.00 v ' ' ' ' ' ' ' ' ' ' ' ' ' ' A 0.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hyd No. 1 Time (min)
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
7.835
1
5
4,701
------
------
------
EXISTING CONDITIONS
Coolwick-Existing.gpw
Return Period: 10 Year
Thursday, 04 / 30 / 2020
5
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
EXISTING CONDITIONS
Hydrograph type
= Mod. Rational
Peak discharge
= 7.835 cfs
Storm frequency
= 10 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 4,701 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.38*
Intensity
= 6.029 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(0.150 x 0.95) + (3.270 x 0.35)] / 3.420
Q (cfs)
8.00
.M
4.00
rM
0.00 r 1 1
0 1 2
— Hyd No. 1
EXISTING CONDITIONS
Hyd. No. 1 -- 10 Year
3 4 5 6 7 8 9
Q (cfs)
8.00
M
4.00
2.00
A 0.00
10 11 12 13 14 15
Time (min)
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
10.75
1
5
6,449
------
------
------
EXISTING CONDITIONS
Coolwick-Existing.gpw
Return Period: 100 Year
Thursday, 04 / 30 / 2020
7
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
EXISTING CONDITIONS
Hydrograph type
= Mod. Rational
Peak discharge
= 10.75 cfs
Storm frequency
= 100 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 6,449 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.38*
Intensity
= 8.270 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(0.150 x 0.95) + (3.270 x 0.35)] / 3.420
Q (cfs)
12.00
10.00
91011111
.M
4.00
rM
EXISTING CONDITIONS
Hyd. No. 1 -- 100 Year
Q (cfs)
12.00
10.00
M
M
4.00
2.00
0.00 r ' ' ' ' ' ' ' ' ' ' ' ' ' ' X 0.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
— Hyd No. 1 Time (min)
Hydraflow Rainfall Report
0
Hydraflow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12
Return
Period
Intensity -Duration -Frequency Equation Coefficients (FHA)
(Yrs)
B
D
E
(N/A)
1
0.0000
0.0000
0.0000
--------
2
74.0559
13.3000
0.8788
--------
3
0.0000
0.0000
0.0000
--------
5
83.5115
14.8000
0.8514
--------
10
105.7041
16.8000
0.8710
--------
25
118.9249
17.6000
0.8582
--------
50
137.0265
18.6000
0.8630
--------
100
157.1766
19.6000
0.8692
--------
File name: Revised-Raleigh.IDF
Intensity = B / (Tc + D)^E
Thursday, 04 / 30 / 2020
Return
Period
Intensity Values (in/hr)
(Yrs)
6 min
10
16
20
26
30
36
40
46
60
66
60
1
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
2
5.76
4.65
3.92
3.40
3.01
2.70
2.45
2.25
2.08
1.93
1.81
1.70
3
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
5
6.57
5.43
4.64
4.07
3.63
3.28
3.00
2.76
2.57
2.40
2.25
2.12
10
7.22
6.03
5.19
4.57
4.09
3.71
3.40
3.13
2.91
2.72
2.56
2.41
25
8.19
6.90
5.98
5.29
4.75
4.32
3.97
3.67
3.41
3.20
3.01
2.84
50
8.95
7.59
6.60
5.86
5.27
4.80
4.41
4.08
3.81
3.57
3.36
3.17
100
9.71
8.27
7.22
6.42
5.79
5.28
4.86
4.50
4.20
3.93
3.70
3.50
Tc = time in minutes. Values may exceed 60.
Precip. file name: Sample.pcp
Storm
Rainfall Precipitation Table (in)
Distribution
1-yr
2-yr
3-yr
6-yr
10-yr
26-yr
60-yr
100-yr
SCS 24-hour
0.00
2.20
0.00
3.30
4.25
5.77
6.80
7.95
SCS 6-Hr
0.00
1.80
0.00
0.00
2.60
0.00
0.00
4.00
Huff-1 st
0.00
1.55
0.00
2.75
4.00
5.38
6.50
8.00
Huff-2nd
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Huff-3rd
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Huff-4th
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Huff-Indy
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Custom
0.00
1.75
0.00
2.80
3.90
5.25
6.00
7.10
APPENDIX D
Post -Development Peak Flow Tables (2-yr, 10-yr, and 100-yr)
Page 9 September 15, 2020
Watershed Model Schematic Hydraflow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12
Project: Coolwick-Proposed Without BMPs.gpw
Thursday, 04 / 30 / 2020
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
9.710
1
5
5,826
------
------
------
PROPOSED WITHOUT BMP
Coolwick-Proposed Without BMPs.gpw
Return Period: 2 Year
Thursday, 04 / 30 / 2020
3
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
PROPOSED WITHOUT BMP
Hydrograph type
= Mod. Rational
Peak discharge
= 9.710 cfs
Storm frequency
= 2 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 5,826 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.61 *
Intensity
= 4.655 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(1.480 x 0.95) + (1.940 x 0.35)] / 3.420
Q (cfs)
10.00
4.00
PROPOSED WITHOUT BMP
Hyd. No. 1 -- 2 Year
Q (cfs)
10.00
We
4.00
2.00
0.00 r ' ' ' ' ' ' ' ' ' ' ' ' ' ' A 0.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
— Hyd No. 1 Time (min)
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
12.58
1
5
7,547
------
------
------
PROPOSED WITHOUT BMP
Coolwick-Proposed Without BMPs.gpw
Return Period: 10 Year
Thursday, 04 / 30 / 2020
5
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
PROPOSED WITHOUT BMP
Hydrograph type
= Mod. Rational
Peak discharge
= 12.58 cfs
Storm frequency
= 10 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 7,547 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.61 *
Intensity
= 6.029 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(1.480 x 0.95) + (1.940 x 0.35)] / 3.420
Q (cfs)
14.00
12.00
10.00
.M
4.00
PROPOSED WITHOUT BMP
Hyd. No. 1 -- 10 Year
Q (cfs)
14.00
12.00
10.00
M
4.00
2.00
0.00 r ' ' ' ' ' ' ' ' ' ' ' ' ' ' A 0.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
— Hyd No. 1 Time (min)
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
17.25
1
5
10,352
------
------
------
PROPOSED WITHOUT BMP
Coolwick-Proposed Without BMPs.gpw
Return Period: 100 Year
Thursday, 04 / 30 / 2020
7
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Thursday, 04 / 30 / 2020
Hyd. No. 1
PROPOSED WITHOUT BMP
Hydrograph type
= Mod. Rational
Peak discharge
= 17.25 cfs
Storm frequency
= 100 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 10,352 cuft
Drainage area
= 3.420 ac
Runoff coeff.
= 0.61 *
Intensity
= 8.270 in/hr
Tc by User
= 5.00 min
IDF Curve
= Revised-Raleigh.IDF
Storm duration
= 2.0 x Tc
Target Q
=n/a
Est. Req'd Storage
=n/a
Composite (Area/C) = [(1.480 x 0.95) + (1.940 x 0.35)] / 3.420
Q (cfs)
18.00
15.00
12.00
•M
.M
3.00
PROPOSED WITHOUT BMP
Hyd. No. 1 -- 100 Year
Q (cfs)
18.00
15.00
12.00
M
M
3.00
0.00 r ' ' ' ' ' ' ' ' ' ' ' ' ' ' A 0.00
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hyd No. 1 Time (min)
Watershed Model Schematic Hydraflow Hydrographs Extension for AutoCADO Civil 3DO 2018 by Autodesk, Inc. v12
1
3
4
Project: Coolwick-Proposed.gpw Tuesday, 09 / 15 / 2020
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
7.069
1
5
4,241
------
------
------
PROPOSED POND
2
Reservoir
0.000
1
n/a
0
1
396.75
4,241
Proposed Pond
3
Mod. Rational
2.497
1
5
1,498
------
------
------
PROPOSED POND
4
Combine
2.497
1
5
1,498
2,3
------
------
COMBINED SITE
Coolwick-Proposed.gpw
Return Period: 2 Year
Tuesday, 09 / 15 / 2020
3
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Tuesday, 09 / 15 / 2020
Hyd. No. 4
COMBINED SITE
Hydrograph type
= Combine
Peak discharge
= 2.497 cfs
Storm frequency
= 2 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 1,498 cuft
Inflow hyds.
= 2, 3
Contrib. drain. area
= 1.290 ac
Q (cfs)
3.00
rM
1.00
0.00
0 1 2
— Hyd No. 4
COMBINED SITE
Hyd. No. 4 -- 2 Year
3 4 5 6
Hyd No. 2
7 8 9 10 11
Hyd No. 3
12 13 14
Q (cfs)
3.00
2.00
1.00
V 0.00
15
Time (min)
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
9.265
1
5
5,559
------
------
------
PROPOSED POND
2
Reservoir
0.000
1
n/a
0
1
396.99
5,559
Proposed Pond
3
Mod. Rational
3.273
1
5
1,964
------
------
------
PROPOSED POND
4
Combine
3.273
1
5
1,964
2,3
------
------
COMBINED SITE
Coolwick-Proposed.gpw
Return Period: 10 Year
Tuesday, 09 / 15 / 2020
5
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Tuesday, 09 / 15 / 2020
Hyd. No. 4
COMBINED SITE
Hydrograph type
= Combine
Peak discharge
= 3.273 cfs
Storm frequency
= 10 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 1,964 cuft
Inflow hyds.
= 2, 3
Contrib. drain. area
= 1.290 ac
Q (cfs)
4.00
3.00
rM
1.00
0.00 -9
0
COMBINED SITE
Hyd. No. 4 -- 10 Year
Q (cfs)
4.00
3.00
2.00
1.00
I I I I I I I I I I I I I I V 0.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Time (min)
Hyd No. 4 Hyd No. 2 Hyd No. 3
Hydrograph Summary Report HydraflowHydrographsExtension for AutoCAD®Civil 3D®2018byAutodesk,Inc. v12
Hyd.
No.
Hydrograph
type
(origin)
Peak
flow
(cfs)
Time
interval
(min)
Time to
Peak
(min)
Hyd.
volume
(cuft)
Inflow
hyd(s)
Maximum
elevation
(ft)
Total
strge used
(cuft)
Hydrograph
Description
1
Mod. Rational
12.82
1
5
7,692
------
------
------
PROPOSED POND
2
Reservoir
0.632
1
15
265
1
397.28
7,643
Proposed Pond
3
Mod. Rational
4.529
1
5
2,718
------
------
------
PROPOSED POND
4
Combine
4.529
1
5
2,982
2,3
------
------
COMBINED SITE
Coolwick-Proposed.gpw
Return Period: 100 Year
Tuesday, 09 / 15 / 2020
7
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2018 by Autodesk, Inc. v12
Tuesday, 09 / 15 / 2020
Hyd. No. 4
COMBINED SITE
Hydrograph type
= Combine
Peak discharge
= 4.529 cfs
Storm frequency
= 100 yrs
Time to peak
= 5 min
Time interval
= 1 min
Hyd. volume
= 2,982 cuft
Inflow hyds.
= 2, 3
Contrib. drain. area
= 1.290 ac
Q (cfs)
5.00
4.00
3.00
R 11
1.00
0.00
0 2 4
— Hyd No. 4
COMBINED SITE
Hyd. No. 4 -- 100 Year
6 8 10 12 14
Hyd No. 2
Q (cfs)
5.00
4.00
3.00
2.00
1.00
—" 0.00
16 18 20 22 24 26 28 30
Time (min)
Hyd No. 3
APPENDIX E
Wetland and Stream Map
Page 10 September 15, 2020
APPENDIX F
Drainage Area Maps
Page 11 September 15, 2020
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