HomeMy WebLinkAbout010-84 S College Hills Grading Plan.2io lobo
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HEADWALL - 6K DETAIL.
816.
GRADING-PLAN1 ": 3 0'
�T
HEADWALL
DETAIL 1.
N.T.S.
PREDEVE1,010ENT R'JN-OFF
TOTAL SF = 39,000
IMPROVED SF - 19,3
UNIMPROVED SF - 23
ASSUME THERE IS A? -
wDURATION:
DURATION:
ASSUME THERE IS A t-5 INCHES HOUR RATE
FOR THE 10 YEAR RA:!.
ASSUME .9 RUNOFF COFFICIENT FOR
-----
IMPROVF.O 'iRFAQ
ASSUME .288 RUNOFF COEFFICIENT FOR
UNIMPROVED AREAS
IMPROVED RAINFALL CALCULATIONS
20 MIN/60 MIN/HP x 4.5 INCHES/HOUR x
t
19,300 SF x 12 INCHES/FOOT - 3,485 FT3.
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8 19.3 0 \
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VILLAGE \\\\ 4
PANTRY
IV
F.F. 821.0
820 .44
Q'r I
820.37�� p
.819,36 \ �'
4
819.45 819.91
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91
HEADWALL - 6K DETAIL.
816.
GRADING-PLAN1 ": 3 0'
�T
HEADWALL
DETAIL 1.
N.T.S.
PREDEVE1,010ENT R'JN-OFF
TOTAL SF = 39,000
IMPROVED SF - 19,3
UNIMPROVED SF - 23
ASSUME THERE IS A? -
wDURATION:
DURATION:
ASSUME THERE IS A t-5 INCHES HOUR RATE
FOR THE 10 YEAR RA:!.
ASSUME .9 RUNOFF COFFICIENT FOR
IMPROVF.O 'iRFAQ
ASSUME .288 RUNOFF COEFFICIENT FOR
UNIMPROVED AREAS
IMPROVED RAINFALL CALCULATIONS
20 MIN/60 MIN/HP x 4.5 INCHES/HOUR x
19,300 SF x 12 INCHES/FOOT - 3,485 FT3.
UNIMPROVED RAINFALL CALCULATIONS
20 MIN/60 MIN/HR x 6.5 INCHES/HOUR x
23,150 SF x 12 INCHES/FOOT = 4,179 FT3.
TOTAL RUNOFF IN 20 MIN. OF MAXIMUM
RAIN FALL (10 YEAR) - 4,179 t 3,485 =
7,664 FT3.
AFTER DEVELOPMENT RUNOFF
TOTAL SF = 39,000
IMPROVED SF - 23,606
UNIMPROVED SF - 15,394
ASSUME THERE IS A MAXIMUM OF 20 MINUTE
DURATION:
ASSUME THERE IS A 8.5 INCHES/HOUR RATF.
FOR THE 100 YEAR RAIN
IMPROVLD AREAS
ASSUME .288 RUNOFF COEFFICIENT FOR
UNIMPROVED AREAS
IMPROVED RAINFALL CALCULATIONS
20 MIN/60 MIN/HR x 8.5 INCHES/HOUR x
23,606 SF x 12 INCHES/FOOT = 5,573 FT3.
UNIMPROVED RAINFALL CALCULATIONS
20 MIN/60 MIN/HR x 8.5 INCHES/HOUR x
15,394 SF x 12 INCHES/FOOT = 3,634 FT3.
TOTAL RUNOFF IN 20 MIN. OF MAXIMUM
RAIN FALL (100 YEAR) = 9,207 FT3.
PREDEVELOP14ENT MAX;MUM RUNOFF: 7,664 FT3.
AFTER DEVELOPMENT MAXIMUM RUNOFF: 9,207 FT3.
WE MUST RETAIN 1,543 FT3. TO MEET THE 100 YEAR RAIN
AFTER DEVELOPMENT 1EQUIREMENT IN RUNOFF AS COMPARED TO
THE 10 YEAR RAIN PREDEVELOPMENT.
MAXIMUM RUNOFF ALLOWABLE IN SHOWN BELOW-
7664 FT3/20 MINUTES OR
383.2 FT3/INCHES OF
383,2 FT3/INCHF,S rjvTnFn Av A0 SFrOND/TNCHFS
5.39 �T3/SFON"
ASSUME THE WATER IS RUNNING AT 18' THEREFORE H = 2'
BETWEEN TOP OF R£7ENTION AND WATER FLOWING IN MAIN LINE.
d = (2,159 On) 3/8 Q - av = 6.39 FT3/SECOND
5 1/2 n - .015
55' x 44' = 2,475 3F AT 1' AVERAGE DEPTH OR HAVE 2,475
FT3 STORAGE
Date
s`
7.25•,
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