HomeMy WebLinkAboutCASEY'S CAR WASH - MAJOR AMENDMENT - 23-09 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTL
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Existing Conditions
Description
Area ft2
Cvalue
Building
3178.44
0.95
Concrete
3769.30
0.95
-- Asphalt
15733.80
0.95
Landscape
3621.65
0.15
Total =
26303.2
1 0.84
Proposed Conditions
Description
Area ftz
Cvalue
Building
3178.44
0.95
Concrete
3481.38
0.95
Asphalt
16019.72
0.95
Landscape
3623.66
0.15
Total =
1 26303.2
0.84
additions proposed.
project. If you have
(970) 491-9888.
Sincerely,
JR Engineering
Prepared b
Derek Patterson
We greatly appreciate your time and consideration in reviewing this
any questions or require additional information, please contact us at
Reviewed
Timothy J. Halopoff, P.E.
Design Engineer Land Development Manager
April 10, 2009
Wes Lamarque
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Casey's Carwash — Drainage Letter
Dear Wes,
We are pleased to submit for your review, this letter, which outlines the revised drainage
design for the proposed addition to the Casey's Carwash site. This letter references the
design originally approved by James H. Stewart and Associates, entitled "Troutman
P.U.D. Phase Two" dated July 12, 1983 and the previous study by JR Engineering,
entitled "Casey's Carwash-Drainage Letter" dated July 28, 2008. All computations in
this report have been completed in compliance with the City of Fort Collins Storm
Drainage Criteria, dated May 1984, revised April 1997.
The revised layout of the site includes remodeling a few of the existing self -wash bays
for use as a fast food restaurant. Additionally, the existing asphalt parking area along the
north side of the proposed remodel will be modified into a landscaping and patio seating
area for the Casey's Cafe. The parking configuration and pedestrian facilities will also be
modified. In order to anticipate possible retrofit issues that might have impacted the
design, JR Engineering met with a city Stormwater representative last year, and it is our
understanding that the originally approved design will be grand fathered in as it exists
today and has for more than 20 years, with the caveat that the runoff from the site cannot
be increased. To this end, the design proposes to replace the former parking area located
north of the Casey's Cafd with landscaping. Calculations included at the end of the
report indicate that the replacement in these areas with more pervious materials serve to
keep the runoff coefficient of the site to its existing condition.
The criteria set forth in the city's manual was utilized to determine all necessary runoff
coefficients for the revised site. The results were then averaged using typical area -
weighted methods. The results, included at the back of the report, demonstrate that
runoff from the site will remain as it exists today. Thus, the proposed additions will have
no negative effects to the existing drainage conditions.
In summary, the proposed design meets or exceeds the applicable criteria established by
the manual as well as the requirements established previously by the city's Stormwater
Department. Since the design serves to maintain the volume and peak runoff rate leaving
the site, no negative impacts are anticipated downstream. Therefore, the design proposed
in this letter and corresponding construction documents is assumed adequate to serve the