HomeMy WebLinkAboutDrainage Reports - 10/12/1988FINAL STORM DRAINAGE REPORT
MEDICAL CENTER OF FORT COLLINS, P.U.D.
STEWART & ASSOCIATES, INC.
214 NORTH HOWES
FORT COLLINS, COLORADO 80521
STE AIART&ASSocIATES
Consulting Engineers and Surveyors
October 12, 1988
Mr. Glen Schlueter
Storm Drainage Utility
City of Fort Collins
P 0 Box 580
Fort Collins, CO 80522
Dear Glen:
The Medical Center of Fort Collins, P.U.D., is located at the
Northeast corner of Prospect Road and Lemay Avenue. It is an amended
planned unit development that consists of Prospect/Lemay Office-P.U.D.
and a former Chevron Oil Company station. The site is in the Spring
Creek Drainage Basin.
The former Prospect/Lemay Office P.U.D. had two existing buildings
of its proposed three buildings and its two parking areas were fully
developed. The station site was fully developed and consisted of nearly
100% impervious ground cover.
The Prospect/Lemay Office P.U.D. has existing onsite storm water
detention. The North parking lot has an existing detention volume of
0.18 acre feet and a release rate of 0.3 cubic feet per second according
to the Storm Drainage Table shown on Sheet 1 of 2 of the Utility Plans
by Parsons and Associates and dated April 1982. The South parking area
has an existing detention volume of 0.59 acre feet and a release rate
of 0.8 cubic feet per second. The Parsons and Associates Final Plan .
is included as a part of this report.
The station site was built prior to the requirement for onsite
detention. The runoff from the station site and from the two parking
lot detention ponds is carried in the existing curb and gutter Southerly
on Lemay Avenue and Easterly on Prospect Road to three existing double
inlets on the North side of Prospect Road at Welch Street.
The Medical Center of Fort Collins P.U.D. has the two existing
buildings and a revised building for the third pad in the original P.U.D.
and a new office building on the old station site. The North parking 9
lot is being enlarged by approximately 3,900 square feet and the
additional parking area will continue to drain to the detention pond. ? yr" eotoo
The South parking lot is being enlarged by approximately 12,000 squar %
feet and it will also continue to drain to the detention pond. The
proposed new building coverage on the Prospect/Lemay Office P.U.D. is
being reduced by approximately 2,500 square feet. The building on the
station site will reduce the impervious area by approximately 2,900 square
feet. Approximately one half of that building will drain to the existing
James H. Stewart
and Associates, Inc.
214 N. Howes Street
P.O. Box 429
Ft. Collins, CO80522
3031482-9331
detention pond and the other half will drain to Lemay Avenue and Prospect
Road. The net result is an increase of approximately.10,500 square feet
of impervious area. However, the original P.U.D. used a runoff factor
of 0.85 because of the use and it actually had a runoff coefficient of
0.68. The runoff coefficient for Medical Center of Fort Collins as
proposed is 0.75 which is below the design coefficient.
Because the parking areas are only being altered and not being
totally torn out, it would be very difficult and costly to enlarge the
detention ponds. We are therefore not proposing to increase the detention
volumes. We feel this is justified because of the larger than required
design coefficient and because. of the close proximity of the site to
Spring Creek.
A copy of the new grading plan is also enclosed as a part of this
report. If you have any questions concerning this matter, please call.
Sincerely,
�
C/n:wlua�-�
Richard A. Rutherford, E. & L.S.
President
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CONSULTING ENGINEERS 47051221-2400
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