HomeMy WebLinkAboutLot Certifications - 11/20/2001 (10)AIRES
ASSOCIATES
November 20, 2001
Mr. Jay Barber
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Re:. Detention Pond Certification for Building E, Lot 6A, Collindale Business Park Third Filing.
Dear Jay,
We recently surveyed and developed topography for the two detention ponds located within Lot
6A, Collindale Business Park Third Filing to verify whether the grading met the intent of the
approved grading and drainage plan. In the grading and drainage plan, the two ponds are
referred to as Pond 1 and Pond 2. Pond 1 is a small pond located in the northeast corner of the
development.. Pond 2 is a larger pond located in the center open -space of the development.
The following paragraphs compare the designed to as -built conditions for the two ponds.
Pond 1 is a small pond located in the northeast corner of the development. The design volume
for the pond was 3,466 cubic feet, at elevation 4954.49. The design volume of 3,466 cubic feet
is met in the as -built pond at elevation 4954.79. The spillway was designed at.elevation 4955.6,
and was built at exactly that elevation. Pond 1, as graded meets the design intent, has
adequate volume and has freeboard prior to discharge through the spillway section.
Pond 2 is a larger detention pond constructed in the central open space of the .development.
The design volume for the pond was 16,204 cubic feet at elevation of 4957.49. The as -built
storage at elevation 4957.7 is 16,220 cubic feet. The eastern berm for the pond was raised at
or above elevation 4957.7 to provide adequate detention volume. Pond 2, as graded meets the
design intent and has adequate volume to provide active storage for the 100-year event.
It is my recommendation that the detention ponds for this property be accepted, since the
Contractor graded them to meet design guidelines. If you have any questions, please call.
Sincerely,
Chlrrsftop YL. CToherty, ai SIM
Project ngineer
CLD:sp
Enclosure
Owen Ayres &.Associates, Inc.
Engineers/Scientists/Su rveyors
3665 JFK Parkway, Building 2, Suite 200, P.O. Box 270460, Fort Collins, CO 80527
(970) 223-5556, Denver Metro (303) 572-1806, FAX (970) 223-5578 BARBIIG.DOC
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Collindale Business Park 3rd Filing Lot 6A
As -Built Detention Pond Grading Cerification
Ayres Associates, November 2001
Detention Pond 1
ELEV. AREA
ft. s .ft.
DEPTH
ft.
SURFACE
AREA
Acres
DELTA
VOLUME
Acre-feet
CUM.
VOLUME
Acre-feet
cu. Ft.
4953.1
0
0.00
0.000
0.005
0.000
0
4953.5
1654
0.40
0.038
0.024
0.005
221
4954.0
2601
0.90
0.060
0.064
0.029
1275
4955.0
2935
1.90
0.067
0.093
4042
V (1-2) _((A1+A2+(A1*A2)A1/2)/3)*(EL2-EL1)
Detention Pond 2
ELEV. AREA
ft. sq.ft.
DEPTH
ft.
SURFACE
AREA
Acres
DELTA
VOLUME
Acre-feet
CUM.
VOLUME
Acre-feet
cu. Ft.
4954.8
0
0.00
0.000
0.000
0.000
0
4955.0
224
0.20
0.005
0.047
0.000
15
4956.0
4855
1.20
0.111
0.062
0.047
2056
4956.5
5975
1.70
0.137
0.081
0.109
4758
4957.0
8155
2.20
0.187
0.182
0.190
8277
4957.7
14874
2.90
0.341
0.372
16220
V (1-2) _ ((A1+A2+(A1*A2)A1/2)/3)*(EL2-ELi)
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