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HomeMy WebLinkAboutEAST RIDGE - FDP - 33-98F - SUBMITTAL DOCUMENTS - ROUND 1 - VARIANCE REQUESTTST TST, INC. CONSULTING ENGINEERS 748 Whalers Way Fort Collins, CO 80525 970.226.0557 metro 303.595.9103 fax 970.226.0204 January 23, 2008 Ms. Susan Joy . City of Fort Collins Engineering Department 281 N. College Ave. PO Box 580 Fort Collins, CO 80522-0580 Re: East Ridge Vertical Curve Length Variance Request Project No. 0983.0007.00 Dear Susan, A variance for the minimum vertical curve lengths for crest and sag curves along Sykes Drive is being requested. The specific criteria for which the variance is being requested is from the Larimer County Urban Area Street Standards (LCUASS) Chapter 7, Section 7.4.1, BA.a (Minimum Length Crest and Sag). This section references Figures 7-17 and 7-18 to determine the minimum curve lengths. Due to street drainage capacity and grade issues, numerous low points were needed along Sykes Drive. With narrow lot frontages (typically 50') it was necessary to place the Type `R' inlets at lotlines to allow room for driveways, water and sewer services and "shallow" utilities. To accomplish this, vertical curve criteria for a local street section were used. The difference in curve length for the majority of the curves is 30' (design curves are 30' shorter than criteria). TST looked at trying to use the minor collector criteria for vertical curve lengths, but found that the low points and inlets would have to be placed along lot frontages and not on lot lines. The vertical difference in the high and low points between the local and minor collector curve lengths was found to be generally hundredths of afoot to a tenth. In two cases the difference was approximately .2-.3' (24"). TST does not believe that this vertical difference at the high and low points will noticeably affect the drivability of the roadway. This variance will not impact construction or maintenance costs for the City. There is no perceived or anticipated risk to the health and safety of the public due to this variance from the design criteria. Please feel free to contact me with any questions or to discuss this request further. Sincerely, TST, IqC. CONSULTING ENGINEERS �. Spencer . Smith, P.E. SMS/mgf info@tstinc.com I i w .tstinc.com TST, INC. CONSULTING ENGINEERS ITST 748 Whalers Way Fort Collins. CO 80525 970.226.0557 metro 303.595 . 9103 fax 970.226.0204 January 23, 2008 Ms. Susan Joy City of Fort Collins Engineering Department 281 N. College Ave. PO Box 580 Fort Collins, CO 80522-0580 Re: East Ridge storm sewer bury depth variance request Project No. 0983.0007.00 Dear Susan, A variance for the minimum depth of bury for storm sewer pipes is being requested for the East Ridge project. The specific criteria for which the variance is being requested is from the Larimer County Urban Area Street Standards (LCUASS) Chapter 12, Section 12.2.2 (Minimum Depth). This criteria states that all utilities shall be located at least 2 feet below the scarified subgrade elevation. Constraints on the storm drainage system prevent the storm sewer system from being lowered. To achieve the 2 foot minimum depth over all of the storm sewer would require an exceptional amount of fill over a large portion of the site. TST was notified that per Rick Richter at the City of Fort Collins that the City would accept 1.5 feet from subgrade to top of pipe. All of the East Ridge storm sewer meets this criteria, with most areas exceeding it. TST believes that if the contractor properly installs and backfills the storm sewer pipe, there should be no issues with excessive settlement that would cause damage to street paving. This variance will not impact construction or maintenance costs for the City. There is no perceived or anticipated risk to the health and safety of the public due to this variance from the design criteria. Please feel free to contact me with any questions or to discuss this request further. Sincerely, TST, NBC. CONSULTING ENGINES 1/V\_ Spencer M. Smith, P.E. SMS/mgf info@tstinc.com I i w .tstinc.com L J