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STEWART&ASSOCATES
Consulting Engineers and Surveyors `
November 25, 1996
Mr. Basil Hamdan
Storm Water Utility
City of Fort Collins
P.O. Box 580
Fort Collins, CO 80522
Dear Basil,
This is regarding the storm drainage for Dellenbach Chevrolet Auto Storage Lot that is
proposed on the southeast comer of Swallow Road and McClelland Drive. The site is a part of
Lot 3, Swallow Subdivision, that was developed in 1984. There were three building sites
proposed at that time. Parcel "A" and Parcel "B" were completed in 1984. Both parcels have
two office buildings, Parcel "C" was not built on in 1984. The entire Lot 3 was to have a
common parking area and a common storm water detention pond. The detention pond was built
in the portion of the lot that has been completed. The discharge pipe and concrete pan have been
in operation since 1984.
The required volume was calculated using a mass diagram, and it was 9,972 cubic feet. The
allowable release rate was 0.42 cubic feet per second, and the discharge pipe was a four -inch
P. V.C. pipe through a headwall. The "C" coefficient of imperviousness that was used was 0.95.
The upper 35 lineal feet of the detention pond will be on Auto Storage Lot's east end of their
portion of the parking lot. I do not believe that "As Built" surveys were required in 1984. We
can do an "As Built" survey of the entire pond at the time the City desires to insure that the
required detention is available.
The site at this time has a good cover of weeds and grass; however, most of the site will be
disturbed. The parking lot will be graded and the base material will be placed as soon as possible.
The asphalt will be laid in March or April 1997. A silt fence will be placed along the east property
line to protect the offices and the existing asphalt parking lot.
The grading plan for the site and the water calculations from 1984 are enclosed as a part of
this report. If you need further information for this project, please call.
Sincerely,
Richard A Rutherford, P.E. & L.S.
President
' rrc James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
' Ft. Collins, CO 80522
970/482-9331
Fax 970/482-9382
INDEX
1 Cover letter and text of report
2 Vicinity Map
3-6 original Calculations for a Part of Lot 3 (including this site)
7 Foothills Basin plan
8 Stormwater Runoff Quantities
9-11 Erosion Control Calculations
12 Erosion Control Collateral
Pocket Utility, Grading & Drainage Plan
STORM DRAINAGE REPORT
FOR
DELLENBACH CHEVROLET AUTO STORAGE LOT
r A PART OF LOT 39 SWALLOW SUBDIVISION
LOCATED IN THE FOOTHII.LS DRAINAGE BASIN
:J
NOVEMBER 259 1996
PREPARED BY
STEWART & ASSOCIATES, INC.
103 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
970/482-9331