2013-10-07_PERMIT FILE - C1981025A ‎(6)‎

• Permit No: C1981025A
• IBM Index Class Name: Permit File
• Doc Date: 10/7/2013
• Doc Name: Final Engineering Calculations
• Section_Exhibit Name: 4.0 Appendix 4-B
• Media Type: D
• Archive: Yes

• Sediment Pond 9, P-9
The above calculations show there is adequate
water storage, 0.41 AF, for the 10-Yr 24-Hr event.
The run-off from the 10-Yr 24-Hr event calculated
above is 0.35 AF.
The pond is oversized because the reclaimed areas do
not yield the run-off that the disturbed areas did.
The storage volume below the principle spillway, 0.74 AF
is allotted to sediment storage and seepage water
treatment as explained in pages 4-66h and 4-66i.
The existing 18" CMP will be capped and a 3" diameter
hole provided in the cap to form the principle spillway.
The emergency spillway will be constructed over the
existing 18" CMP. See drawings D-4-5 & D-4-6 for
details.
Check the capability of the 3" dewatering device
to dewater the pond. Volume of water to decant
will be that in storage from elevation 6513.5 to
6511.5.
DISCHARGE UNDER FALLING HEAD
• Area of pond must be constant with varying height.
Use area at maximum pool elevation, 6513.5.
AREA OF POND = A 9687.0 SQUARE FEET
DIAMETER OF PIPE 3.0 INCHES
AREA OF PIPE = a 0.0491 SQUARE FEET
C = LOSS COEFFICIENT 0.750
H1 = BEGINNING HEAD 2.000 FEET
H2 = ENDING HEAD 0.000
t = time to lower the surface level of the pond (H1-H21.
t = 2A*(H1".5 - H2".51/C*a*(2G1".5
t = 92786 SECONDS
t = 1.07 DAYS
Reference Civil Engineering Handbook.
Urquhart, Fourth Edition, Page 4-34.

P-9-4 New 7-11-91