HomeMy WebLinkAboutRIDGEWOOD HILLS - FDP230019 - SUBMITTAL DOCUMENTS - ROUND 2 - Responses (14)
5265 Ronald Reagan Blvd., Suite 210
Johnstown, CO 80534
970.800.3300 • GallowayUS.com
August 16, 2023
Engineering Development Review
City of Fort Collins
281 N College Avenue
Fort Collins, CO 80524
RE: Ridgewood Hills Filing No. 5 - Variance Request to Stormwater Development Construction
Standards
Please find this letter as our formal request for an administrative variance to the requirements set forth
within the Fort Collins Utilities Stormwater Development Construction Standards as they relate to
depth of cover over proposed storm sewer pipes. The project, Ridgewood Hills Filing No. 5, is located
at the southwest corner of the intersections of Triangle Drive and US 287 in the City of Fort Collins.
The project proposes a network of proposed storm sewer to convey runoff generated on-site to a
series of water quality and detention ponds before that runoff is discharged into the adjacent public
storm sewer system. Various other utilities, including public sanitary sewer, public water, and a private
irrigation ditch, are proposed with the development as well. Storm Sewer Line B is proposed to convey
captured runoff that is detained in Detention Pond B to the site’s outfall into the public storm sewer
system. This portion of storm sewer runs from Pond B to the north within Strasburg Drive and
discharges into the Robert Benson Lateral at the northeast corner of the site. Portions of the proposed
storm sewer pipe have less than 3’ of cover from top of pipe to finished grade within Strasburg Drive.
We would like to request a variance to Stormwater Development Construction Standards to allow for
the reduced depth of cover on the proposed storm sewer pipe. The vertical profile of Strasburg Drive
is constrained between its connection point in Triangle Drive and its southern terminus at the property
line. Storm Sewer Line B is proposed to meet minimum pipe size (15”) and slope requirements (0.5%)
for stormwater utilities within the Right-of-Way. These minimum pipe constraints allow for adequate
conveyance while still providing at least 30” of cover on top of the pipe, with the exception of
approximately 15’ where the pipe first passes under Strasburg Drive. In this area cover will not be less
than 24”. Further, the proposed profile of the Storm Sewer Line B is restricted due to conflicts with
other portions of the storm sewer system that it crosses. Minimum clearances must be maintained
across these utility crossings that prevent a minimum of 3’ of cover. Particularly, the crossing of Storm
Sewer Line B with Storm Sewer Line A-11, prevents Line B from achieving 3’ of cover. A hydraulic
analysis of Storm Sewer Line A-11, which only meets minimum profile slope requirements, determined
that adjustments of this line to lower the crossing and achieve more cover for Line B is not feasible.
According to Fill Heigh Tables developed by the American Concrete Pipe Association, Class III 15”
Reinforced Concrete Pipe is suitable for a 2’ minimum depth of cover. In lieu of the 3’ depth of cover,
it is proposed to increase the pipe class material to Class IV Reinforced Concrete Pipe. This increase
in pipe class will provide an extra measure of safety against failure of the structural pipe. Therefore, it
is not anticipated that the proposed limitations on depth of cover would pose any additional detriment
to safety or the design life or maintenance costs of the proposed storm sewer.
Goodwin Knight
Ridgewood Hills Fifth Filing
August 16, 2023
Galloway & Company, Inc. Page 2 of 2
Thank you for your consideration of this variance request. Should you have any questions, please do
not hesitate to contact me 970.800.3300.
Sincerely,
GALLOWAY
James E Prelog, P.E.
Civil Engineering Project Manager
970.800.3300
JamesPrelog@GallowayUS.com
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