HomeMy WebLinkAbout104-Attachment C.pdfDRAINAGE CALCULATION:
JN: 06 -224
Address: Wardell Road Project
Date: 2121107
Pre - Development Stormwater Run -off
Find Q,:
C =0.50
A =6 AC
1=1.60 in (10 yr- 15min)(according to SC County IDF Curve of 20 ")
Q,= C I A = (0.5)(6.0)(1.6 )= 4.8 cfs
Find Q,,:
C =0.50
A =6 AC
I =2.30 in (100 yr- 15mirn)(according to SC County IDF Curve of 20")
Q,= C I A = (0.5)(6.0)(2.3) = 6.9 cfs
Post - Development Stormwater Run -off
Find Q—t:
C =0.40
A =0.50 AC
1 =1.6 in (10 yr- l5min) (according to SC County IDF Curve of 20 ")
Qp..= C I A = (0.40)(0.5)(1.60 )= 0.32 cfs
Find Q,,:
Cw =0.40
A =0.50 AC
I =2.30 in (100 yr- l5m in) (accord ing to SC County TDF Curve of 20 ")
Qp.,,= Cw I A = (0.40)(0.5)(2.3) = 0.46 cfs
Total Qt= Q, + Q,.� =4,8 cfs + 0.32 cfs = 5.12cfs (10 yr- 15min)
Total Qt= Qprc + QRos, =6.9 efs + 0.46 cfs = 7.36efs (100 yr- 15min)
Calculate Existing 15" RCP Capacity:
Legth of Pipe:
294feet
Slope of Pipe (S):
0.75%
Diameter of Pipe (D):
15in
Manning Coef (n):
0.013
Area of Pipe (A):
1.227 t12
Hydraulic Radius (R ^213):
0.4605
Find Qpipe
Qpipe—(1.486/n)A(R^2/3) (S^ 1/2)
= (1.486/0.013)(1,227)(0.4605)(0.0075A 112)
= 5.59cfs
Summary:
The existing 15" RCP in Wardell Road will be able to withstand the increase runoff
created by the private access road on Lot A. Currently, the pipe collects approximate 6.5
aces of water shed; see the Tributary Drainage Area Map. The existing 15" RCP pipe
capacity is 5.59 cfs and the post watershed will produce an approximate 5.12 efs.
Therefore, existing 15" RCP is capable of withstanding a 10 year storm.
J j �f C SteE1
1
, r : - , / j`� �•, � r NO-
Ell
C 7 (rr�
'gK
LOT
1 r
LOT ,c
/r
i i 3 F i I ; �/� 1 A
L0
1l�h 0.5AC�
��I��i is" r''( '� � _ y.�✓. a�,'kt'" �`� ,� � �� it r f` �ll�' � ���I i��(��� `t_ _
T
j5.1 "kP — z "RCP a.aa5
Ll
1;
r �
i i j l le
DATE: 2/19/07 T2IBUTARY DRAINAGE AREA
1 I WARDEL_ ROAD, SARATOGA, CALIFORNIA
1 SCALE 1" =200'
T5 CIVIL ENGINEERING, INC.
DRAWN BY: SK 1776 TECHNOLOGY DRIVE
SAN JOSE, CA 95110
DESIGNED BY: MS
JOB NO 06-224 (VII,
PAGE: 1 OF 1 PH: 408.452.9300 FAX: 408.452.9301