HomeMy WebLinkAboutDrainage Reports - 11/08/2018NORTHERN
ENGINEERING
Drainage Letter Report
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8703NA158
Date.: October 23, 2018
Project: Collindale Industrial Park- Minor Amendment
Fort Collins, Colorado
City "Or'
Collins Approved Plans
Approved by.
Date. i1 2ofg
Project No. 1281-001
Attnt " Mr, Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
Dear Wes:
This letter serves to address the stormwater impacts of the above referenced project. This project is located at
the.southwestcorner of the intersection of Timberline Road and Danfield Court. The site currently consists of
rooftop, concrete walks and patio, asphalt parking areas, trees, and other vegetation. The site presently drains
west to east via overland flow into :a series of areaandcurb inlets located in the center of the parking lot -and
drive aisles. Only one inlet is getting relocated -which .is:in the landscaping area to the,west.side of the building. -
It's going to be. placed within the new flowline, but the historic flows will still be getting routed to it. The rest of
the inlets are going to remain exactly where they are and at the same elevation to preserve historic drainage
patterns. The inlets release into the City's storm sewer system within Timberline Road. Historic drainage
patterns will generally be preserved. The total impervious area within the project boundary of the existing site is
approximately 247,996 square-feetwith a composite percent impervious of 97%.
The.proposed redevelopment will be removing some parking islands, an associated storage building, a portion of
some sidewalks, and some asphalt associated with the parking lots. The new project is proposing to modify the
parking lot to increases parking count.as well as adding some additional: sidewalks and associated landscaping
amenities. The new project intends to maintain existing drainage patterns as well as utilizing all the existing -
storm infrastructure except for relocating one inlet.. The total impervious area within the project boundary of the
,proposed redevelopment is roughly 241,181 square -feet with a composite percent impervious of 97%.
Therefore, these improvements are reducing the overall impervious area for the site. Due to the reduction in
impervious area there will not be any detention or water quality provided with this improvement. For additional
clarification on these calculations please see the attached Runoff Coefficient Calculations at the back of this
letter.
Northern Engineering was unable to locate any previous drainage. reports associated with the existing
development. However, existing percent impervious and drainage patters were maintained so no adverse
impacts will occur with downstream infrastructure. Therefore, no additional drainage analysis or infrastructure is
needed for this minor amendment. If there are -any concerns or questions, please give Northern Engineering a
call.
Cody N. Snowdon, PE
Project Manager
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Blaine Mathisen, El
Project Engineer
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