HomeMy WebLinkAboutDrainage Reports - 03/08/2016 (2)"MAl�ooii-llgh'k�o;�1..Sura:��
City of Fort Collins Approved Plans
North Star ApprovedabT.tdesign Date:
700 Automation Drive, Unit I
Windsor, CO 805510
Phone: 970-686-6939
Fax:970-686-1188
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March 7, 2016
Dan Mogen
City of Fort Collins Utilities
700 Wood Street
Fort Collins, CO 80522-0580
RE; Drainage letter update for Final Drainage and Erosion Control Study for
Oakridge Business Park, Thirty -Fifth Filing
Oakridge Business Park Plaza
Mr., Mogen:
This letter is intended as an update to the previously approved drainage report for "Final
Drainage and Erosion Control Study for Oakridge Business Park, Thirty -Fifth Filing,
Oakridge Business Park Plaza" completed by North Star Design,, Inc: dated October 1, 2001.
The site layout is proposed to be modified slightly to remove-3 parking stalls and replace that
asphalt area -with a concrete patio on the south side of the existing building (refer to the modified
site plan submitted for the minor amendment for details). It appears that the amount of
imperviousness on site has been maintained or slightly reduced.. In modifying'the curb and
adding the patio area, some of the grades have been modified but the general drainage concept
has been maintained.
The modification to the grading and the parking lot causes a change in volume for the detention
pond in the uppermost portions of the pond. The stage storage table has.been updated and is
attached for reference. The changes in the stage storage values are not significant and caused an
increase of the 100 year watersurface elevation of 0.01' which is insignificant therefore, no
other drainage calculations were updated:.
0
I appreciate your time and consideration in reviewing this drainage update. Please call if you
have. anyquestions.•- _'�jb
Sincerely,
Patricia Kroetch, P.E.
-�0 03/07/16 .
.............
NAL,
OAKRIDGE BUSINESS PARK PLAZA
Proposed Detention / Water Quality Pond - Stage/Storage
LOCATION:
Oakridge Business Park Thirty Fifth Filing
PROJECT NO:
137-01
COMPUTATIONS BY:
PPK
SUBMITTED BY:
NORTH STAR DESIGN, INC.
DATE:
3/7/2016
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
Water Quality Volume Required = 0.068 Acre -Feet
Detention Volume Required = 0.47 Acre -Feet
Total Volume Required = 0.538 Acre -Feet
WQCV
10 YR WSEL
100 YR WSEL
Overflow elev
detention REV.xls
Stage
(ft)
Surface
Area
(ft`)
Incremental
Storage
(ac-ft)
Total
Storage
(ac-ft)
72.41
0
73
3961
0.02
0.02
73.37
7964
0.05
0.068
74.00
14780
0.20
0.22
74.08
16098
0.03
0.248
74.70
25408
0.32
0.539
75.00
29963
0.50
0.72
75.12