HomeMy WebLinkAboutVILLAGE COOPERATIVE FORT COLLINS - FDP - FDP170009 - SUBMITTAL DOCUMENTS - ROUND 1 - VARIANCE REQUESTFebruary 22, 2017
City of Fort Collins Development Review
Marc Virata
281 N. College Ave.
Fort Collins, CO 80524
(970) 221-6567
Project # 1284-001
Village Cooperative Utility Plans
Variance Request for Section 12.2.2 Minimum Depth
Variance description:
This is a request for variance to the Standard contained in Section 12.2.2 of the Larimer County Urban
Area Street Standards which pertains to the Minimum Depth of Utilties.
Variance to this standard will allow for the construction of a right turn lane from westbound Horsetooth
Road to northbound Stanford Road.
Technical Design Criteria:
12.2.2 Minimum Depth
All utilities shall be located at least 2 feet below the scarified subgrade elevation, unless specifically
approved to be less by the Local Entity Engineer. Greater depth of cover may be specified by the Local
Entity Engineer.
Variance Justification Criteria:
The professional Engineer must determine and state that the variance will not be detrimental to the
public health, safety and welfare, will not reduce design life of the improvement nor cause the Local
Entity additional maintenance costs. The proposed plan (as varied) must advance the public purpose of
the standard sought to be varies equally well or better than would compliance with such standard.
Identifying the Issue:
An existing large storm sewer junction at the intersection of Horsetooth Road and Stanford Road is a
regional conveyance for the Foothills Drainage Basin. Three 26”x43” RCP Arch pipes enter the junction
structure from the west and three 26”x43” RCP Arch pipes exit the junction structure to the south. The
existing arch pipes under the Horsetooth Road street section are shallow with existing cover depths
between 1’ and 1.5’.
Due to the existing storm sewer junction box, the ultimate improvements of Horsetooth Avenue were
constricted to a narrowed width. This constriction made it impossible to fit both a right turn lane and
bike lane without relocating the existing storm structure or rerouting the right turn lane with a pork
chop. It was determined by City staff that most cost-effective and simple solution was to reroute the
right turn lane around the existing storm structure by utilizing a pork chop island.
Due to the rerouting of the right turn lane, the sump in the curbline was moved and a new 24” storm
pipe will need to be installed to convey stormwater flows from Horsetooth and Stanford to the existing
junction structure. Due to the minimal existing cover depth on the existing storm pipes, the proposed
storm pipe will be similarly deficient in cover. The proposed 24” storm pipe will have cover depths
varying between 13” and 2’ from finished grade.
As this cover is less than the minimum 8” asphalt and 15” aggregate base course pavement section for a
4-lane arterial, a concrete pavement is proposed within this area. The pavement design will be provided
by a geotechnical engineering to obtain the requirements set forth by the Larimer County Urban Area
Street Standards.
Justification:
It is assumed that the LCUASS has adopted this standard on minimum depth for storm sewers in order
to combat challenges in regards to maintenance of the public roads. Additionally, it is assumed that a
storm pipe within the street pavement section is more likely to affect the bearing strength of the
roadway.
This change in pavement type, though more expensive, will provide the similar strength as an asphalt
section. Additionally, maintenance of concrete pavement is generally less often than asphalt pavement.
Lastly, asphalt maintenance and resurfacing within these narrow width areas can be challenging and
more time consuming for municipalities.
With this change in pavement type, the maintenance and strength concerns of the pavement will be
allayed.
We do not feel that this variance will be detrimental to the public health, safety or welfare, nor will it
reduce the design life of any public roadway or cause the City of Fort Collins additional maintenance
costs.
Please call if you have any questions.
Sincerely,
Stephanie Thomas, P.E.
Project Engineer