HomeMy WebLinkAboutSPRADLEY BARR FORD EXPANSION - BASIC DEVELOPMENT REVIEW - BDR180025 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE RELATED DOCUMENT1218 W. ASH, STE. A, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
August 7, 2018
Mr. Shane Boyle
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80522
Re: Spradley Barr Ford Subdivision – Storm Drainage Letter
Dear Shane,
We are pleased to submit for your review and approval this drainage letter showing the drainage
impacts from the proposed redevelopment at the Spradley Barr Ford site.
The project is located at 4809 South College Avenue and currently has an existing structure and
an asphalt parking lot on the site. The project will build a 12,000 square foot addition to the
existing structure for a body shop. This new structure will be mostly over existing paved areas
and major site reconfiguration is not proposed. The proposed improvements will increase the
existing impervious area by 945 square feet. The area of the site that will be improved is
approximately 0.7 acres.
The City of Fort Collins requires a drainage letter along with a grading and erosion control plan
if the increase in impervious area is greater than 350 square feet and less than 1,000 square feet.
Therefore, the existing and proposed imperviousness of the project area was compared as a part
of this study. Exhibits are attached which show that the existing imperviousness area is 30,464
sf while the proposed improvements will increase the imperviousness area to 31,409 sf. The
total project area is 31,658 sf; therefore, the proposed improvements will increase the impervious
area by 945 square feet.
Because the increase in impervious area is less than 1,000 square feet, the City of Fort Collins
does not require water quality treatment nor additional onsite detention. The four-step process
for selecting structural BMPs is also not required and will not be presented in this letter.
Today the area sheets to existing area inlets and storm system that drains east to an existing
detention pond adjacent to College Avenue. With the addition of the body shop, flows will
continue to sheet in the same direction. The storm system and inlets will be rerouted away from
the proposed addition but will tie-into the same existing system. Overland relief is available in
the drive aisle in the event the storm sewer becomes plugged or overwhelmed.
Mr. Shane Boyle
August 7, 2018
Page 2 of 2
1218 W. ASH, STE. C, WINDSOR, COLORADO 80550
TEL. 970.674.3300 – FAX 970.674.3303
We appreciate your time and consideration in reviewing this submittal. If you have any
questions or need additional information please feel free to call at any time (970) 460-8471.
Sincerely,
Michael Oberlander, P.E.
Colorado Professional Engineer 34288
Interwest Consulting Group
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