HomeMy WebLinkAboutSite Certifications - 08/26/2008--I -North Star
I*&Aw design, inc.
July 27, 2008
Jay Barber
City of Fort Collins
700 Wood Street
Fort Collins, CO 80522
Dear Jay,
This letter is to certify the detention and water quality pond at Fossil Lake 4`h Filing. The
approved stage -storage table for the pond is attached with the as -built volumes for the
pond at the bottom of the sheet. The information presented is based on topographic
survey of the detention ponds provided by Northern Engineering (copy attached).
The volume achieved in the pond appears to meet the requirements set forth in the
approved drainage report and plans within acceptable construction tolerances. The water
quality volume (0.157 acre feet) is achieved at an elevation of 10.52 compared to a
design elevation of 10.25 and the total volume of 1.30 acre-feet is achieved at an
elevation of 14.13, compared to a design elevation of 14.00, as shown in the drainage
report.
The sizes of all orifice openings and water quality outlet holes have been verified and are
within acceptable construction tolerances.
Please call me if you have any questions or if you need any additional information.
S
Patricia roetch, P:
700 Automation Drive, Unit I Windsor, Colorado 80550 I
970-686-6939 Phone 970-686-1 188 Fax
vH'o8°QA19
LOCATION:
PROJECT NO:
COMPUTATIONS BY:
SUBMITTED BY:
DATE:
WQ VOLUME
100 YEAR DET
BERM
Detention Pond - Stage/Storage
FOSSIL LAKE 4TH FILING, FIRST REPLAT
296-01
PPK
NORTH STAR DESIGN
7/29/2008
V = 1 /3 d (A + B + sgrt(A*B))
where V = volume between contours, ft3
d = depth between contours, ft
A = surface area of contour
WQ 0.157 AC -FT
100 DET 1.143 AC -FT
TOTAL 1.300 AC -FT
Stage
(ft)
Surface
Area
(ft)
Incremental
Storage
(ac-ft)
Detention
Storage
(ac-ft)
Total
Storage
(ac-ft)
8.5
0
9.0
1453
0.01
0.01
10.0
8351
0.10
0.11
10.25
8974
0.05
0.00
0.157
11.0
10841
0.17
0.17
0.33
12.0
12998
0.27
0.44
0.60
13.0
15373
0.33
0.77
0.93
14.00
17925
0.38
1.15
1.308
15.0
20912
0.45
1.60
1.753
ASBUILT POND VOLUME
WQ VOLUME
100 YEAR DET
BERM
Stage
(ft)
Surface
Area
(ft)
Incremental
Storage
(ac-ft)
Detention
Storage
(ac-ft)
Total
Storage
(ac-ft)
8.87
0
9.0
63
0.00
0.00
10.0
7150
0.06
0.06
10.52
8968
0.10
0.00
0.157
11.0
10620
0.11
0.11
0.26
12.0
13026
0.27
0.38
0.53
13.0
15460
0.33
0.70
0.86
14.00
17922
0.38
1.09
1.244
14.13
18204
0.06
0.00
1.300
15.0
20912
0.45
1.53
1.690
DET POND asbuilt.XLS
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