Sand Filter Calculations-Updated 12.12.18

Sand Filter Design Project: WU-2019 Student Housing
Section 11 NCDENR BMP Manual Location: Wingate NC /
Date: 7/11/2018 Rev 12/12/18 ✓
Designer: Clint Lawrence, PE, PLS
Flow to Basin Data
Composite CN after development:
4.13 ac.
Impervious Area
CN= 98
Soil Type:
0 ac.
Roof area
CN=
SCS Soil Group:
0 ac.
Gravel
CN= 89
B Soils
1.12 ac.
Grassed Area
CN= 61
C Soils
0.95 ac.
Grassed Area
CN= 74
6.20 ac.
Total Area
CN=
Composite CN
87.639
Volumetric Runoff Cofficient, Rv:
Rv=.05+.009(I) % Impervious Area
Rv 0.649516
Water Qualitv Protection Volume, WQv:
WQv=1.ORvA/12
WQv 0.34 Ac-Ft
14,618 c.f
WQv ADJ 10,964 c.f. 75% reduction of WQv
WQv 0.487137 in. of runoff
Modified CN
66.61
CN=1000/[10+5P+10WQv-10(WQV^2+1.25WQVP)^.51
P 1
Modified CN 93.70027
Sand Filter Volume
SF Vol =WQv ADJ*0.5
5481.754 c.f.
Sand Filter Area
Af =SF Vol/ponding depth
Af 3,655 sf Required

3,830 sf Provided
Sand Filter Media Stage -Storage:
Qo=Af(K)(hf+df)/(df)(Cf)
Use Af 3830 sf
k 3.5 ft/day
df 1.5 ft
ha 0.75 ft
Underdrain Capacity:
D=16((Q* n)/(s^0.5))A(3/8))
IF D is less than 7.84 use (2) 6' Pipes
BMP section 5.7
Underdrain Capacity:
2# of 6" dia. Underdrains
139 ft Length of underdrains
256 # of 3/8 dia. Performations assuming 50% clogged
Elev
528.5
0.155150463
529
0.258584105
530
0.465451389
531
0.672318673
532
0.879185957
533
1.086053241
5.977757
(2) 6" Undergrounds Proposed
0.009501 cfs Capacity of one perforation=CA(2gh)A.5
1.216117 cfs Capacity of all performations assuming 50% clogged
0.789 cfs Capacity of all 6" dia. PVC pipes by Manning Eq
0.394 cfs Capacity assuming 50% clogged
OK underdrain capcity greater than max. media capacity
Anti -Flotation Base:
Boyant force=Weight of water displace by outlet structure
5.33 ft
5.33 ft
10ft
9,500 Ibs Wt of water displaced=Volume of structure*62.4 Ib/cf
19,150 Ibs Wt of four 8" thick walls at 145 Ib/cf (Pre Cast Structure)
2 Factor of Saftey
None Req Wt. of base required at 145lb/cf
0 c.f. concrete required at 145 Ib/cf
0 ft min, square concrete base, 12" thick

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Hydraflow Table of Contents
SCM 12.12.18.gpw
Hydraflow Hydrographs by Intelisolve v9.2
2 - Year
Wednesday, Dec 12, 2018
SummaryReport................................................................................................................. 1
HydrographReports........................................................................................................... 2
Hydrograph No. 1, SCS Runoff, Pre................................................................................. 2
TR-55 Tc Worksheet.................................................................................................... 3
Hydrograph No. 2, SCS Runoff, Post............................................................................... 4
Hydrograph No. 3, Reservoir, Dry Pond........................................................................... 5
PondReport - SCM...................................................................................................... 6
10 -Year
SummaryReport................................................................................................................. 7
HydrographReports........................................................................................................... 8
Hydrograph No. 1, SCS Runoff, Pre................................................................................. 8
Hydrograph No. 2, SCS Runoff, Post............................................................................... 9
Hydrograph No. 3, Reservoir, Dry Pond......................................................................... 10
25 - Year
SummaryReport............................................................................................................... 11
HydrographReports......................................................................................................... 12
Hydrograph No. 1, SCS Runoff, Pre............................................................................... 12
Hydrograph No. 2, SCS Runoff, Post............................................................................. 13
Hydrograph No. 3, Reservoir, Dry Pond......................................................................... 14
50 - Year
SummaryReport............................................................................................................... 15
HydrographReports..........................................................�.............................................. 16
Hydrograph No. 1, SCS Runoff, Pre............................................................................... 16
Hydrograph No. 2, SCS Runoff, Post............................................................................. 17
Hydrograph No. 3, Reservoir, Dry Pond......................................................................... 18
100 -Year
SummaryReport............................................................................................................... 19
HydrographReports......................................................................................................... 20
Hydrograph No. 1, SCS Runoff, Pre............................................................................... 20
Hydrograph No. 2, SCS Runoff, Post............................................................................. 21
Hydrograph No. 3, Reservoir, Dry Pond......................................................................... 22
OFReport........................................................................... ■ ............................ an 23

3
TR55 Tc Worksheet
Hydraflow Hydrographs by Intelisolve v9.2
Hyd. No. 1
Pre
Description
A
B
C
Totals
Sheet Flow
Manning's n-value
= 0.150
0.150
0.011
Flow length (ft)
= 150.0
150.0
0.0
Two-year 24-hr precip. (in)
= 3.64
3.64
0.00
Land slope (%)
= 1.00
7.00
0.00
Travel Time (min)
= 16.77 +
7.70 +
0.00 =
24.47
Shallow Concentrated Flow
Flow length (ft)
= 20.00
0.00
0.00
Watercourse slope (%)
= 7.00
0.00
0.00
Surface description
= Unpaved
Paved
Paved
Average velocity (ft/s)
= 4.27
0.00
0.00
Travel Time (min)
= 0.08 +
0.00 +
0.00 =
0.08
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope (%)
= 0.00
0.00
0.00
Manning's n-value
= 0.015
0.015
0.015
Velocity (ft/s)
= 0.00
0.00
0.00
Flow length (ft)
= 0.0
0.0
0.0
Travel Time (min)
= 0.00 +
0.00 +
0.00 =
0.00
TotalTravel Time, Tc..............................................................................
24.50 min

Pond Report s
Hydraflow Hydrographs by Intelisolve v9.2
Wednesday, Dec 12, 2018
Pond No. 1 - SCM
Pond Data
Contours - User -defined contour areas. Conic
method used for
volume calculation. Begining
Elevation = 528.50 ft
Stage / Storage Table
Stage (ft) Elevation (ft) Contour area (sqft)
Incr. Storage (cuft)
Total storage (cuft)
0.00 528.50
4,030
0
0
0.50 529.00
6,400
2,585
2,585
1.00 529.50
9,275
3,896
6,481
1.50 530.00
12,150
5,340
11,820
2.00 530.50
13,750
6,470
18,291
2.50 531.00
15,350
7,271
25,561
3.00 531.50
17,500
8,206
33,767
3.50 532.00
18,750
9,060
42,827
4.00 532.50
20,000
9,685
52,512
4.50 533.00
21,300
10,322
62,834
5.00 533.50
22,625
10,978
73,812
5.50 534.00
23,950
11,641
85,453
6.00 534.50
25,325
12,316
97,769
6.50 535.00
26,700
13,003
110,773
Culvert / Orifice Structures
Weir Structures
[A]
[B]
[C]
[PrfRSr]
[A]
[B]
[C]
[D]
Rise (in)
= 24.00
0.00
0.00
0.00
Crest Len (ft)
= 16.00
1.00
6.00
15.00
Span (in)
= 24.00
0.00
0.00
0.00
Crest El. (ft)
= 535.00
530.50
533.25
533.75
No. Barrels
= 1
0
0
0
Weir Coeff.
= 3.33
3.33
3.33
2.60
Invert El. (ft)
= 523.75
0.00
0.00
0.00
Weir Type
= Riser
Rect
Rect
Broad
Length (ft)
= 62.00
0.00
0.00
0.00
Multi -Stage
= Yes
Yes
Yes
No
Slope (%)
= 1.20
0.00
0.00
n/a
N-Value
= .013
.013
.013
n/a
Orifice Coeff.
= 0.60
0.60
0.60
0.60
Exfil.(in/hr)
= 0.000 (by
Contour)
Multi -Stage
= n/a
No
No
No
TW Elev. (ft)
= 0.00
Stage (ft)
7.00
5.00
3.00
Note: Culvert/Orifice outflows are analyzed under inlet (ic) and outlet (oc) control. Weir risers checked for orifice conditions (ic) and submergence (s).
Stage / Discharge
Elev (ft)
535.50
534.50
533.50
532.50
.�. _w..._. a._.�.w _.. 531.50
530.50
529.50
528.50
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0
Discharge (cfs)
-� Total Q

Hydrograph Summary Report
Hydraflow Hydrographs by Intelisolve v9.2
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
SCS Runoff
16.92
2
728
62,251
----
------
------
Pre
2
SCS Runoff
34.53
2
720
92,448
----
------
------
Post
3
Reservoir
7.956
2
734
74,138
2
532.29
48,389
Dry Pond
SCM 12.12.18.gpw
Return Period: 10 Year
Wednesday, Dec 12, 2018

Hydrograph Report
Hydraflow Hydrographs by Intelisolve v9.2
Wednesday, Dec 12, 2018
Hyd. No. 1
Pre
Hydrograph type
= SCS Runoff
Peak discharge
= 16.92 cfs
Storm frequency
= 10 yrs
Time to peak
= 728 min
Time interval
= 2 min
Hyd. volume
= 62,251 cuft
Drainage area
= 6.200 ac
Curve number
= 76*
Basin Slope
= 0.0 %
Hydraulic length
= 0 ft
Tic method
= TR55
Time of conc. (TO
= 24.50 min
Total precip.
= 5.33 in
Distribution
= Type II
Storm duration
= 24 hrs
Shape factor
= 484
* Composite (Area/CN) = [(0.680 x 98) + (1.450 x 60) + (0.320 x 89) + (2.120 x 79) + (1.630 x 73)] / 6.200
Q (cfs)
18.00
15.00
12.00
3.00
Pre
Hyd. No. 1 -- 10 Year
Q (cfs)
18.00
15.00
12.00
3.00
0.00 ' ' ' ' ' ' ' 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560
Hyd No. 1 Time (min)

Hydrograph Report
E
Hydraflow Hydrographs by Intelisolve v9.2
Hyd. No. 2
Post
Hydrograph type
= SCS Runoff
Storm frequency
= 10 yrs
Time interval
= 2 min
Drainage area
= 6.200 ac
Basin Slope
= 0.0 %
Tc method
= USER
Total precip.
= 5.33 in
Storm duration
= 24 hrs
Wednesday, Dec 12, 2018
Peak discharge = 34.53 cfs
Time to peak
= 720 min
Hyd, volume
= 92,448 cuft
Curve number
= 88*
Hydraulic length
= 0 ft
Time of conc. (Tc)
= 10.00 min
Distribution
= Type II
Shape factor
= 484

Hydrograph Report
10
Hydraflow Hydrographs by Intelisolve v9.2
Hyd. No. 3
Dry Pond
Hydrograph type
= Reservoir
Storm frequency
= 10 yrs
Time interval
= 2 min
Inflow hyd. No.
= 2 - Post
Reservoir name
= SCM
Storage Indication method used.
Q (cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
Wednesday, Dec 12, 2018
Peak discharge = 7.956 cfs
Time to peak = 734 min
Hyd. volume = 74,138 cuft
Max. Elevation = 532.29 ft
Max. Storage = 48,389 cuft
Dry Pond
Hyd. No. 3 -- 10 Year
........
_......_.
...
Q (cfs)
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00, y.,: 0.00
0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 1680
Time (min)
Hyd No. 3 - Hyd No. 2 Total storage used = 48,389 cult