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HomeMy WebLinkAboutVariance Requests - 06/12/2024 5265 Ronald Reagan Blvd., Suite 210 Johnstown, CO 80534 970.800.3300 • GallowayUS.com June 12, 2024 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 (with Louden Irrigation Ditch) 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 as they relate to depth of cover over proposed irrigation 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. Utilities, including public sanitary sewer, public water, a private irrigation ditch, and roadway improvements are proposed with the development. A portion of the Louden Irrigation Ditch bisects the existing project site. The ditch enters the site at the south property boundary, where it meanders across the property, generally from south to north. The ditch enters a culvert near the north property line at Triangle Drive where it passes under the street and resumes open-channel flow north of Triangle Drive. The Ridgewood Hills Fifth Filing project requires the relocation of the ditch. The ditch will still enter the site at the south property boundary where it will continue in its current configuration to a point north and west of the large existing wetland at the southwest corner of the site. There, the ditch will be intercepted and conveyed via an underground pipe system to the northeast. The ditch then resumes open-channel flow as it crosses onto a neighboring property to the east. It is then intercepted again with an underground pipe system as it re-enters the site further north and continues toward the culvert at Triangle Drive via a combined open channel and underground piping system. A portion of the open-channel conveyance north of Castle View Drive will be within the existing ditch before being intercepted again by an underground piping system directed to the culvert at Triangle Drive. The ditch continues its current conveyance pattern north of the Triangle Drive culvert. This is location where the ditch does not meet the 3’ cover requirements stated Per detail D-1 of the City of Fort Collins Stormwater Construction Details and LCUASS 12.2.2 Minimum Depth which states 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. We would like to request a variance to Stormwater Development Construction Standards to allow for the reduced depth of cover on the proposed irrigation pipe A. The vertical profile of Strasburg Drive is constrained between its connection point in Triangle Drive and its southern terminus at the property line. Irrigation A is proposed to exceed minimum pipe size (15”) and slope requirements (0.5%) for 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, except for approximately 100’ where the pipe first passes under Strasburg Drive. In this area cover will be less than 24” therefore 52” steel sleeving will be provided from right-of-way to right-of-way. Further, the proposed profile of Irrigation A is limited by the north tie in point of the Louden Irrigation Ditch. Goodwin Knight Ridgewood Hills Fifth Filing June 12, 2024 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 cc: 5265 Ronald Reagan Blvd., Suite 210 Johnstown, CO 80534 970.800.3300 • GallowayUS.com June 12, 2024 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 asphalt finished grade within Strasburg Drive. Per detail D-1 of the City of Fort Collins Stormwater Construction Details and LCUASS 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. 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 1 5” 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 June 12, 2024 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 cc: