HomeMy WebLinkAboutSW4211102_Design Calculations_20220110Project No. 1104.01
STORE -IT -SAFE SELF -STORAGE
STORMWATER CALCULATIONS
Snow Camp, NC
Alamance County
January 7, 2022
Design Engineers:
Stoltzfus Engineering Inc.
Civil Engineering Consultants
Stoltzfus En ineering, Inc.
823 Gran Street
Kernersville, NC 27284
(336) 904-0207
Developer:
Aiken Keppler
721 Ancient Oaks Drive
Holly Springs, NC 27540
Table of Contents
ProjectNarrative...........................................................................................................................................1
SandFilter Design...........................................................................................................................2
Runoff Curve Nuinbers for SCS Method......................................................................................... 3
RainfallData....................................................................................................................................4
Hydrographs..................................................................................................................................... 5
Project Narrative
A commercial site -development is proposed within Alamance County on S NC-87 Hwy.
The proposed site layout is shown on the construction drawings prepared by Stoltzfus Engineering,
Inc (SEI). The proposed site contains 1.70 acres of total area. The project is a two (2) building
self -storage facility. The project site is owned and will be developed by Aiken Keppler.
Prior to construction, the site was vacant with no existing built -upon area. The
plans as proposed for the project show 1.32 Ac of total built -upon area which is 77.7% of the
total site. The sand filter drainage area is 1.37 Ac. Upon completion the impervious percentage
for the total drainage area received by the sand filter will be 96.4%. The project site is located in
the Jordan Reservoir Watershed and is subject to Phase II Post -Construction SW. As such, the
sand filter is designed in accordance with the water quality standards stated in 15A NCAC
02H .1003 of the North Carolina Administrative Code.
Runoff from the self -storage facility, pavement, and parking areas will be directed to the
sand filter through a series of curb inlets, and grate inlets. Stormwater discharge from this site
drains from the proposed sand filter into an outlet pipe which drains into an existing 24-inch
culvert.
The site drains to an existing NCDOT ditch which is located within the right-of-way for
highway NC-87. The proposed BMP treats all impervious drainage (1.32 Ac) for the
development. 1.23 Ac of drainage area will be bypassed through the site via piping and a clean
water diversion Swale.
BUA Summary:
Total Parcel Area = 1.70 AC.
On -Site BUA 57,650 SF (1.32 Ac, 77.7%)
-Pavement: 28,747 SF (0.66 Ac, 38.75%)
-Sidewalk: 353 SF (0.01 Ac, 0.48%)
-Buildings: 28,550 SF (0.66 Ac, 38.49%)
Total Proposed BUA: 57,650 SF (1.32 Ac, 77.7%)
STORE -IT -SAFE SELF -STORAGE
SAND FILTER DESIGN
1/7/2022
Design Data
Design Period: First
1.00
inch of rainfall (Rd)
Drainage Area:
1.37
ac
Impervious Area:
1.32
ac
Impervious:
96.35
Rv:
0.917
WQV:
4561.08
cf
WQVADJ:
3420.81
cf
hA:
1.50
ft
Sediment Basin A,MIN: 301.56 sf
Sand Filter AFMIN: 392.52 sf
dF: 1.50 ft (Per NCDENR min 1.5 FT)
k: 3.50 ft/day (Coefficient of permeability for the sand filter bed)
t: 1.66 day
hmaxfilt.,:
WQVADJ•
AS+AF
2.00
3420.81
1710.40
3.00
3420.81
1140.27
4.00
3420.81
855.20
5.00
3420.81
684.16
6.00
3420.81
570.13
As
Af
As + AF
516.00
525.00
1041.00
(As + AF) x hma. -_ WQVADJ
SITE ACTUAL
3421.00
5305
[240*R,*ADI*RD
ASMIN-
(WQV)(d F)
AFMIN-
(k)(fl(h,+d,)
NCDENR STAGE STORAGE VOLUME CONTOUR METHOD
STORAGE VOLUME ABOVE SAND FILTER
FOREBAY STORAGE VOLUME
ELEVATION
SURFACE AREA
(sf)
INCREMENTAL
VOLUME (cf)
CUMULATIVE
VOLUME (cf)
ELEVATION
SURFACE AREA (sf)
INCREMENTAL
VOLUME (cf)
CUMULATIVE
VOLUME (cf)
92
1090
-
-
90
33
SED. STORAGE
SED. STORAGE
94
1699
2789
2789
91
203
118
118
95.3
2172
2516.15
5305.15
92
516
359.5
TOTAL (cf)
477.5
477.5
TOTAL (cf)
5305.15
FOREBAY AREA
FILTER
FORBAY DIMENSIONS
AT WEIR LEVEL
DIMENSIONS AT
FILTER AREA AT
AT WEIR LEVEL (ft)
WEIR LEVEL (sf)
(sf)
WEIR LEVEL (ft)
See Plan
516
See Plan
525
UNDER DRAIN CALCULATIONS
TOTALVOLUME
hma.fllte
TOTALVOLUME
PROV. ABOVE
TOTAL AREA
TOTAL AREA
REQ'D ABOVE
PRIMARY
REQ'D (sf)
PROV. (sf)
PRIMARY WEIR (cf)
WEIR(cf)
3.00
3420.81
5305
694.08
1041
SURFACE
HEIGHT OF
HYDRAULIC
AREA OF
DRAW DOWN
QSF
Draw Down Time
Maximum Draw
DEPTH OF SAND
WATER/ DEPTH
CONDUCTIVITY
CHAMBER
RATE "Q" (cfs)
fo
(Hours)
Down Time
OF SAND (f/day)
(Hours)
HEIGHT OF WATER (ft)
(ft)
OF SAND
(sf)
3.00
1.5
2.00
3.50
525
0.043
0.425
29.8
40.0
QSF
"n"
NUMBER OF
DIAMETER OF
fo
MANNING'S
SLOPE OF PIPE
REQUIRED D
PIPES'.N"
PIPE "D" (in)
0.425
0.011
1.00 %
5.07
2
6
Yl40QL11RJR 0117F 03ARMI
Chapter 2 Estimating Runoff Technical Release 55
Urban Hydrology for Small Watersheds
Table 2-2a Runoff curve numbers for urban areas _v
Curve numbers for
-------------------------- Cover description ------------------------
------hydrologic
soil group -------
Average percent
Cover type and hydrologic condition impervious area zi
A
B
C
D
Fully developed urban areas (vegetation established)
Open space (lawns, parks, golf courses, cemeteries, etc.) 3/:
Poor condition (grass cover < 50%)..........................................
68
79
86
89
Fair condition (grass cover 50% to 75%)..................................
49
69
79
84
Good condition (grass cover > 7596).........................................
39
61
74
80
Impervious areas:
Paved parking lots, roofs, driveways, etc.
(excluding right-of-way).............................................................
98
98
98
98
Streets and roads:
Paved; curbs and storm sewers (excluding
right-of-way)................................................................................
98
98
98
98
Paved; open ditches (including right-of-way) ..........................
83
89
92
93
Gravel (including right -of -way) .................................................
76
85
89
91
Dirt (including right -of -way) ......................................................
72
82
87
89
Western desert urban areas:
Natural desert landscaping (pervious areas only) At .....................
63
77
85
88
Artificial desert landscaping (impervious weed barrier,
desert shrub with 1- to 2-inch sand or gravel mulch
and basin borders)......................................................................
96
96
96
96
Urban districts:
Commercial and business.................................................................
85
89
92
94
95
Industrial.............................................................................................
72
81
88
91
93
Residential districts by average lot size:
1/8 acre or less (town houses)..........................................................
65
77
85
90
92
1/4 acre................................................................................................
38
61
75
83
87
1/3 acre................................................................................................
30
57
72
81
86
1/2 acre................................................................................................
25
54
70
80
85
1 acre...................................................................................................
20
51
68
79
84
2 acres..................................................................................................
12
46
65
77
82
Developing urban areas
Newly graded areas
(pervious areas only, no vegetation) 6i................................................................ 77 86 91 94
Idle lands (CN's are determined using cover types
similar to those in table 2-2c).
1 Average runoff condition, and Ia = 0.2S.
2 The average percent impervious area shown was used to develop the composite CN's. Other assumptions are as follows: impervious areas are
directly connected to the drainage system, impervious areas have a CN of 98, and pervious areas are considered equivalent to open space in
good hydrologic condition. CN's for other combinations of conditions may be computed using figure 2-3 or 2-4.
3 CN's shown are equivalent to those of pasture. Composite CN's may be computed for other combinations of open space
cover type.
4 Composite CN's for natural desert landscaping should be computed using figures 2-3 or 2-4 based on the impervious area percentage
(CN = 98) and the pervious area CN. The pervious area CN's are assumed equivalent to desert shrub in poor hydrologic condition.
5 Composite CN's to use for the design of temporary measures during grading and construction should be computed using figure 2-3 or 2-4
based on the degree of development (impervious area percentage) and the CN's for the newly graded pervious areas.
(210-VI-TR-55, Second Ed., June 1986) 2-5
NOAA Atlas 14, Volume 2, Version 3
' Location name: Graham, North Carolina, USA*
Latitude: 35.9064*, Longitude:-79.3071*
Elevation: 520.66 ft**
' source: ESRI Maps A
** source: USGS '
POINT PRECIPITATION FREQUENCY ESTIMATES
G.M. Bonnin, D. Martin, B. Lin, T. Parcybok, 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)1
Average recurrence interval (years)
1
2
5
10
25
50
100
200
500
1000
5-min
4.86
(4.44-5.33)
5.76
(5.28-6.32)
6.70
1 (6.12-7.33)
7.32
(6.68-8.00)
8.00
(7.26-8.74)
8.44
(7.63-9.22)
8.83
1 (7.96-9.65)
9.14
(8.18-10.00)
9.46
1 (8.40-10.3)
9.67
(8.52-10.6)
3.88
4.61
5.36
5.86
6.38
6.72
7.01
7.24
7.48
7.61
10-min
(3.55-4.25)
(4.22-5.05)
(4.90-5.87)
(5.34-6.40)
(5.79-6.96)
(6.08-7.34)
(6.32-7.66)
(6.49-7.92)
(6.64-8.18)
(6.70-8.33)
3.24
3.86
4.52
4.94
5.39
5.68
5.91
6.09
6.28
6.37
15-min
(2.96-3.54)
(3.54-4.24)
(4.134.95)
(4.50-5.40)
(4.89-5.88)
(5.13-6.19)
(5.32-6.46)
(5.46-6.66)
(5.57-6.86)
(5.61-6.97)
2.22
2.67
3.21
3.58
3.99
4.27
4.53
4.74
5.00
5.16
30-min
(2.03-2.43)
(2.44-2.92)
(2.93-3.51)
(3.26-3.91)
(3.62-4.36)
(3.874.66)
(4.08-4.94)
(4.25-5.19)
(4.43-5.46)
(4.54-5.64)
1.38
1.67
2.06
2.33
2.66
2.90
3.12
3.33
3.58
3.77
60-min
(1.26-1.51)
(1.53-1.84)
(1.88-2.25)
(2.13-2.55)
(2.41-2.90)
(2.62-3.16)
(2.81-3.41)
(2.98-3.64)
(3.18-3.92)
(3.32-4.12)
0.820
0.995
1.23
1.41
1.63
1.79
1.95
2.11
2.30
2.45
2-hr
(0.750-0.901)
(0.910-1.09)
1 (1.13-1.35)
1 (1.28-1.54)
11 (1.47-1.78)
1 (1.61-1.96)
1 (1.74-2.13) 11
(1.87-2.30)
(2.02-2.52)
(2.13-2.69)
0.583
0.708
0.879
1.01
1.17
1.30
1.42
1.54
1.70
1.82
3-hr
(0.534-0.639)
(0.649-0.776)
(0.805-0.963)
(0.919-1.10)
(1.06-1.28)
1 (1.17-1.41)
1 (1.27-1.55) 11
(1.37-1.68)
1 (1.49-1.86)
1 (1.58-1.99)
0.353
0.427
0.531
0.610
0.716
0.798
0.881
0.965
1.08
1.17
6-hr
(0.325-0.386)
(0.394-0.467)
(0.487-0.580)
(0.558-0.665)
(0.650-0.778)
(0.719-0.867)
(0.788-0.956)
(0.854-1.05)
(0.940-1.17)
(1.00-1.27)
12-hr
0.191---0 227
0.231---0 275
0.28 0 343
0.332-0 397
0.391---0 468
0.436-0 525
0.48 -0 584
0.526-0 646
0.586-0..732
0.63 -0 802
0.122
0.147
0.183
0.212
0.250
0.280
0.311
0.342
0.385
0.419
24-hr
(0.114-0.130)
(0.138-0.157)
(0.172-0.196)
(0.198-0.226)
(0.232-0.268)
(0.260-0.300)
(0.287-0.334)
(0.315-0.368)
(0.353-0.415)
(0.382-0.453)
0.071
0.086
0.106
0.122
0.142
0.159
0.175
0.192
0.214
0.232
2iiay
(0.067-0.076)
(0.080-0.092)
(0.099-0.114)
(0.114-0.130)
(0.133-0.153)
(0.147-0.170)
(0.162-0.188)
(0.177-0.207)
(0.196-0.232)
(0.212-0.252)
0.050
0.060
0.074
0.085
0.100
0.111
0.123
0.135
0.151
0.163
3�iay
(0.047-0.054)
(0.057-0.065)
(0.070-0.080)
(0.080-0.091)
(0.093-0.107)
(0.103-0.119)
(0.114-0.132)
(0.124-0.145)
(0.138-0.163)
(0.149-0.177)
0.040
0.048
0.059
0.067
0.079
0.088
0.097
0.106
0.119
0.129
aiiay
(0.037-0.043)
(0.045-0.051)
(0.055-0.063)
(0.063-0.072)
(0.073-0.084)
(0.081-0.094)
(0.089-0.104)
(0.098-0.114)
(0.109-0.129)
(0.117-0.140)
7iiay
0.025-0 028
0.029-0.033
0. 35-0 040
0.040-0 046
0.047--0 053
0.05 -0 059
0.057--0.066
0. 6 -0 072
0. 69-0 081
0.074-0.088
0.021
0.025
0.030
0.033
0.039
0.043
0.047
0.051
0.057
0.061
10-day
(0.020-0.022)
(0.023-0.026)
(0.028-0.031)
(0.031-0.036)
(0.036-0.041)
(0.040-0.045)
(0.044-0.050)
(0.047-0.055)
(0.052-0.061)
(0.056-0.066)
0.014
0.016
0.019
0.022
0.025
0.027
0.030
0.033
0.036
0.039
20-day
(0.013-0.015)
(0.015-0.017)
(0.018-0.020)
(0.020-0.023)
(0.023-0.026)
(0.026-0.029)
(0.028-0.032)
(0.030-0.035)
(0.033-0.039)
(0.036-0.042)
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)
(0.018-0.021)
(0.020-0.022)
(0.022-0.024)
(0.023-0.026)
(0.025-0.029)
(0.027-0.031)
0.010
0.011
0.013
0.014
0.016
0.017
0.019
0.020
0.021
0.023
45-day
(0.009-0.010)
(0.011-0.012)
(0.012-0.014)
(0.014-0.015)
(0.015-0.017)
(0.016-0.018)
(0.017-0.020)
(0.019-0.021)
(0.020-0.023)
(0.021-0.024)
60-day
0. 08-0 009
0.010-0 011
0.01100.012
0.01 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
Hydrograph 1-yr Summary
Hydroloqy Studio v 3.0.0.20
Project Name:
01-07-2022
Hyd.
No.
Hydrograph
Type
Hydrograph
Name
Peak
Flow
(Cfs)
Time to
Peak
(hrs)
Hydrograph
Volume
(Cult)
Inflow
Hyd(s)
Maximum
Elevation
(ft)
Maximum
Storage
(Cuft)
1
NRCS Runoff
Post Sand Filter Drainage
5.069
11.93
11,056
----
2
Pond Route
Post Pond Routing
1.457
12.07
11,044
1
95.42
5,666
3
NRCS Runoff
Pre Sand Filter Drainage
1.394
11.97
2,925
----
Hydrograph Report
Hydrology Studio v 3.0.0.20
Pre Sand Filter Drainage
Project Name:
01-07-2022
Hyd. No. 3
Hydrograph Type = NRCS Runoff Peak Flow = 1.394 cfs
Storm Frequency = 1-yr Time to Peak = 11.97 hrs
Time Interval = 2 min Runoff Volume = 2,925 cuft
Drainage Area = 1.37 ac Curve Number = 69
Tc Method = User Time of Conc. (Tc) = 5.0 min
Total Rainfall = 2.92 in Design Storm = Type II
Storm Duration = 24 hrs Shape Factor = 484
Qp = 1.39 cfs
2
77
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Time (hrs)
Hydrograph Report
Hydrology Studio v 3.0.0.20
Post Sand Filter Drainage
Project Name:
01-07-2022
Hyd. No. 1
Hydrograph Type
= NRCS Runoff
Peak Flow
= 5.069 cfs
Storm Frequency
= 1-yr
Time to Peak
= 11.93 hrs
Time Interval
= 2 min
Runoff Volume
= 11,056 cuft
Drainage Area
= 1.37 ac
Curve Number
= 95
Tc Method
= User
Time of Conc. (Tc)
= 5.0 min
Total Rainfall
= 2.92 in
Design Storm
= Type II
Storm Duration
= 24 hrs
Shape Factor
= 484
Qp = 5.07 cfs
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25
Time (hrs)
Hydrograph Report
Hydrology Studio v 3.0.0.20
Post Pond Routing
Project Name:
01-07-2022
Hyd. No. 2
Hydrograph Type
= Pond Route
Peak Flow
= 1.457 cfs
Storm Frequency
= 1-yr
Time to Peak
= 12.07 hrs
Time Interval
= 2 min
Hydrograph Volume = 11,044 cuft
Inflow Hydrograph
= 1 - Sand Filter Drainage
Max. Elevation
= 95.42 ft
Pond Name
= Sand Filter
Max. Storage
= 5,666 cuft
Pond Routing by Storage Indication Method
Center of mass detention time = 10.47 hrs
Qp = 1.46 cfs
6-
5-
4-
3-
2-
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
30 32 34 36 38 40
42 44 46 48
Time (hrs)
— Sand Filter Drainage — Pond Routing
Pond Report
Hydrology Studio v 3.0.0.20
Sand Filter
Project Name:
01-07-2022
Stage -Storage
User Defined Contours
Description Input
Stage / Storage Table
Stage
Elevation
Contour Area
Incr. Storage
(ft)
(ft)
(sgft)
(cuft)
Bottom Elevation, ft 92.00
0.00
92.00
1,090
0.000
Voids (%) 100.00
3.30
95.30
2,172
5,383
Volume Calo Ave End Area
1 4.40
96.40
2,620
2,636
Stage -Storage
Total Storage
(cuft)
0.000
5,383
8,018
97 - 5
96 4
95 3
h
� rD
w h
94 oeo�2
93 1
0000
92 0
0 1000 2000 3000 4000 5000 6000 7000 8000
Total Storage (cuft)
— Contours — Top of Pond
Pond Report
Project Name:
Hydrology Studio v 3.0.0.20 01-07-2022
Sand Filter Stage -Discharge
Culvert / Orifices
Rise, in
Span, in
No. Barrels
Invert Elevation, ft
Orifice Coefficient, Co
Length, ft
Barrel Slope, %
N-Value, n
Weirs
Shape / Type
Crest Elevation, ft
Crest Length, ft
Angle, deg
Weir Coefficient, Cw
'Routes through Culvert "Rate applied to contours
95
aU
ai 94
93
Culvert
0.000
Riser"
Circular
1
1
Cipoletti
95.3
10
Orifices
Perforated Riser
2 3
Hole Diameter, in
No. holes
Invert Elevation, ft
Height, ft
Orifice Coefficient, Co
Weirs
2 3 Ancillary
Exfiltration, in/hr 1.65**
3.3
Stage -Discharge
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38
Discharge (cfs)
Top of Pond — Cipoletti — Exfil —Total Q
4
3
v1
zJ
La
M
2 h
11
Pond Report
Hydrology Studio v 3.0.0.20
Sand Filter
Project Name:
01-07-2022
Stage -Storage -Discharge Summary
Stage
(ft)
Elev.
(ft)
Storage
(cult)
Culvert
(cfs)
Orifices, cfs
Riser
(cfs)
Weirs, cfs
Pf Riser
(cfs)
Exfil
(cfs)
User
(cfs)
Total
(cfs)
1
2
3
1
2
3
0.00
92.00
0.000
0.000
0.000
0.000
3.30
95.30
5,383
0.000
0.083
0.083
4.40
96.40
8,018
38.07
0.100
38.17
Suffix key. is = inlet control, oc = outlet control, s = submerged weir
Pond Report
Hydrology Studio v 3.0.0.20
Sand Filter
Stage (ft)
Project Name:
01-07-2022
Pond Drawdown
Ln M N O
N
O
N
n
N
(\J
Ln
N
N
M
N
N
N
N
O
N
O
F—
r)
>_
L
� �
� 0
N
LE
O
O
Ln
M
N
O
lD Ln M N
M 0" cn M a) M
(11) n013