NCS000402_29_Compass Pointe Pond Calculations-Revised

Compass Pointe Wet Detention Pond 01-24-2014.xls
PERMANENT WET DETENTION POND DESIGN - RISER/BARREL
PROJECT:
NC119 Project
Proposed Wet Detention Pond
INDEX NO:
CHECKED BY:
AIRS
LOCATION:
Mebane, NC
DATE:
1/24/2014 Revised
REVISED:
TOTAL SITE AREA =
6.93 acres
5.54 acres
0.00 acres
WATERSHED =
PROPOSED BUILT UPON AREA =
CLASSIFICATION: WS -
EXISTING BUILT UPON AREA =
(GWA/WCA) _
TOTAL ON -SITE BUILT UPON AREA =
5.54 acres
PERCENT BUILT -UPON =
80.00%
Actual Proposed is around 78.21 % or 5.42 Ac.
ON -SITE DRAINAGE AREA TO POND =
6.93 acres
ON -SITE BUA TO POND =
5.54 acres
ONSITE % BUA FOR POND SUB -BASIN =
80.0%
OFF -SITE DRAINAGE AREA TO POND =
0.00 acres
OFF -SITE BUILT -UPON AREA =
0.00 acres
TOTAL WATERSHED AREA TO POND =
6.93 acres
6.93 acres
Y
DISTURBED AREA =
TEMP. SED. STOR. USED (Y/N)
TEMPORARY SEDIMENT STORAGE 0.5 acre -inch per disturbed acre
PERMANENT SEDIMENT STORAGE 0.125 acre -in per total drainage area
PERMANENT WATER QUALITY
COMPOSITE B.U. % = 80.0 percent
DEPTH (minimum 3 feet) 3.83 feet (Ave.)
SA/DA (Figure 10-1) 3.962 percent (90% TSS)
TEMPORARY WATER QUALITY 1.0 Inch rainfall to be controlled
TYPE X corrugated aluminum
reinforced concrete
DESIGN STORM 10 year
RAINFALL INTENSITY 6.87 inches per hour
RUNOFF COEFFICIENT 0.85
TYPE X grass lined
rip rap lined
DESIGN STORM 100 year
RAINFALL INTENSITY 8.31 inches per hour
RUNOFF COEFFICIENT 0.85
ELEV. @ BOT. OF POND =
626
SURFACE AREA =
5788 SF
ELEV.@ BOT. OF PSS =
626
SURFACE AREA =
5788 SF
ELEV. @ BOT. OF PWQ =
627
SURFACE AREA =
6730 SF
ELEV. @ NORMAL POOL =
632
SURFACE AREA =
14465 SF
ELEV. @ TOP. OF RISER =
634.3
SURFACE AREA =
19924 SF
ELEV. @ EMER. SPILLWAY =
635.3
ELEV. @ TOP OF DAM =
636.8
INVERT OF BARREL =
627
ELEV. @ BOT. OF POND= 626.00 SURFACE AREA = 5788 Square Feet
ELEV. @ NORMAL POOL = 632.00 SURFACE AREA = 14465 Square Feet
ALLOW 75% OF BASIN VOLUME TO WQ ORIFICE = 45569 Cubic Feet
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Compass Pointe Wet Detention Pond 01-24-2014.xls
ELEV. @ BOT. OF PSS =
626.00
SURFACE AREA =
5788 Square Feet
ELEV. @ BOT. OF PWQ =
627.00
SURFACE AREA =
6730 Square Feet
VOLUME PROVIDED =
6259 Cubic Feet
OK
PERMANENT WATER QUALITY SURFACE AREA REQ'C
11960 Square Feet
NORMAL POOL ELEVATION =
632.00
SURFACE AREA PROVIDED =
14465 Square Feet
OK
TEMPORARY WATER QUALITY STORAGE REQUIRED
Rv=
0.770 in/in
VOLUME REQUIRED =
19370 Cubic Feet
TOTAL =
19370 Cubic Feet
VOLUME PROVIDED
ELEV. @ BOT. OF TWQ =
632.00
SURFACE AREA =
14465 Square Feet
ELEV. @ TOP OF TWQ =
634.30
SURFACE AREA =
18604 Square Feet
VOLUME PROVIDED =
41104 Cubic Feet
OK
PRINCIPAL SPILLWAY
DESIGN STORM PEAK FLOW =
40.5 CFS
1.00 ft
634.30
HEAD ABOVE TOP OF RISER =
ELEVATION AT TOP OF RISER =
BARREL:
BARREL SIZE USED (in) =
36.00 in. dia.
ELEVATION AT TOP OF RISER =
634.30
ELEVATION OF BARREL INVERT =
627
Hw PROVIDED =
7.30 ft
Hw/D PROVIDED=
2.43
1.42
4.26 ft
Hw/D REQ'D. FOR DESIGN STORM (FROM CHART) =
Hw REQUIRED =
CHECK CULVERT (INLET CONTROL)=
OK
Q (FROM CHART) AT Hw/D PROVIDED=
81.9 CFS
77
RISER:
RISER(AREA) =1.5 TIMES AREA OF:
36.00 in. dia.
MIN. RISER DIA. =
44.09 in. dia.
RISER DIA.USED =
54 in. dia.
WEIR EQUATION:
Qw =
47.1 CFS
OK
ORIFICE EQUATION:
Qo =
76.6 CFS
OK
Qw CONTROLS =
47.1 CFS
PRINCIPAL SPILLWAY SYSTEM:
RISER CONTROLS
47.1 CFS
PRINCIPAL SPILLWAY SYSTEM:
OK
WATER QUALITY RELEASE HOLE
ELEV. @ BOT. OF WATER QUALITY RELEASE HOLE =
632.00
MAXIMUM RELEASE RATE =
2 Days
MINIMUM RELEASE RATE =
5 Days
MAXIMUM HOLE SIZE =
0.052732023
3.11 in. dia.
MINIMUM HOLE SIZE =
0.021092809
1.97 in. dia.
Use 2.50" Dia Hole Size
EMERGENCY SPILLWAY
ELEV. @ EMER. SPILLWAY =
635.3
DESIGN STORM PEAK FLOW =
Rational
49.0 CFS
FLOW THROUGH EMER. SPILLWAY =
1.9 CFS
EMER. SPILLWAY SIDE SLOPES (ie 3 if 3:1, 0 if vertical) =
3
FLOW DEPTH =
0.50 ft
BOTTOM WIDTH REQUIRED =
1.77 ft
Use 12' Spillway
FLOTATION OF RISER
ELEV. @ TOP OF RISER
1
634.30
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Compass Pointe Wet Detention Pond 01-24-2014.xls
ELEV. @ BOT. OF RISER =
627.00
H =
7.30 ft
AREA OF RISER =
15.9 SF
VOLUME OF RISER =
116.1 Cubic Feet
AREA OF BARREL =
7.1 SF
10.00 ft
70.7 Cubic Feet
EXPOSED LENGTH =
VOLUME OF BARREL =
WEIGHT OF WATER DISPLACED =
11655.53 Ib
FACTOR OF SAFETY (10%)
12821.08 Ib
VOLUME OF CONCRETE ANCHOR =
146.4 Cubic Feet
Use Tx Tx3'
FULL POND DESIGN DATA
Description
Elevation
Surface Area
Incremental Volume
Pond Bottom
626
5788
Top of Sediment Storage
627
6730
6,259
Top of Foreba s Excludes Baffles
631
11178
35,816
Top of Forebays (Surface Area Used for
Depth Calculation between top of forebays
and Bottom of Shelf)
631
11625
Bottom of Shelf
631.5
12083
5,927
Normal Pool
632
14465
6,637
Top of Shelf
632.5
17005
7,868
Top of Riser
634.3
19924
33,236
Invert of Emergency Spillway
635.3
21251
20,588
Top of Dam
636.8
23115
33,275
Bottom Area of Main Pond
627
6021
Depth (Ave. for Calculations)
3.83
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