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Home My WebLink AboutFORT COLLINS VOLUNTEERS OF AMERICA, ELDERLY HOUSING - PDP - 14-01 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTVICINITY MAP VICINITY MAP i REFERENCES 1. "1997 Foothills Master Drainage Plan Update and Westfield Park P.U.D. Regional Detention Pond Analysis", Fort Collins, Colorado, Faucett Engineering Services, December 1997. 2. "Final Report for Hydrologic Model Update for the Foothills Basin Master Drainage Plan", Fort Collins, Colorado, Anderson Engineering, revised December 1, 1999. 3. "City of Fort Collins Storm Drainage Design Criteria and Construction Standards", City of Fort Collins, Revised April 12, 1999. Fort Collins VOA, Elderly Housing Project — Drainage & Erosion Control Report 5 IRRIGATION DITCHES AND LATERALS ' To the west of the proposed site is an irrigation ditch owned by the Pleasant Lake & Valley Irrigation Ditch Company. Three headgates control flows heading east to the Skyline Acres Subdivision via shallow open ditch laterals. Redesign and relocation of these laterals has been coordinated with the ditch company and has received approval from the homeowners of Skyline Acres. The northern lateral will be relocated into a closed concrete channel adjacent to the Horsetooth right -of way. The irrigation lateral crossing the middle of the site will be redesigned to be a partially covered open concrete channel, and the lateral to the south will not be disturbed. All properties currently served by the three laterals will be served by the redesigned lateral system. STORMWATER MANAGEMENT FLAN Erosion control features will be established prior to onsite construction. All erosion control measures, proposed and existing, will be maintained until the completion of �! the project and until vegetation is established. Vehicle tracking control will be used u at the site construction entrance off West Horsetooth Road. Straw bale inlet protection and channel protection BMP's will be included on the construction plans for onsite inlets. A silt fence will be installed at the eastern property boundary. Non- structural erosion controls including project schedule, and other pollution prevention measures are specified in this plan (refer to Erosion Control Plan in Construction Documents). The erosion control notes, and specifications will be included on the construction drawings. U The stormwater management plan will be included in the Erosion Control Plan and detail sheets within the bid document package for the site construction with all Il structural BMP's shown as required. U CONCLUSIONS U All developed conditions at the proposed site will be directed to the onsite detention pond, the sub -basin to the south will remain in historic condition and runoff from the parcel will not be detained. Developed conditions and release are in conformance �i with the current master plan. Calculations and other reference materials used are �J attached in Appendix A. Excerpts from the master drainage plan reports are included in Appendix B and have been incorporated into the calculations in Appendix A. The j referenced Developed Drainage Map depicts the drainage design points and configuration of the proposed storm drainage system. The recommendations of this report are in conformance with all applicable storm drainage regulations ,and criteria of the City of Fort Collins. Fort Collins VOA, Elderly Housing Project — Drainage & Erosion Control Report 4 Istorm sewer system. Flows from these sub -basins are conveyed to the onsite y detention pond at design point 15, the collection point for sub -basin O. The Brook Drive Right -of -Way was identified as an emergency drainage overflow conveyance path for the Westfield. Park subdivision located west of the proposed project. The designed conveyance path for Brook Drive has a calculated carrying capacity of 58.5 cfs at a flow depth of 0.5 feet (See Appendix). Calculated flows for Westfield Park and the proposed site were modeled at 38.1 cfs conveying through Brook Drive required at a curb depth of 0.41-feet. The curb depth for the Brook Drive has been designed at 0.5-feet. Flows greater than the 58.5 cfs will overtop the curb and create a wider channel profile. The 38.1 cfs volume modeled for the emergency overflow will not enter any housing complexes. HYDROLOGIC METHOD AND DESIGN STORM FREQUENCIES The Rational Method (Q=CIA) was used to determine the storm runoff (Q) from this site, with composite runoff coefficients (C) and contributing areas (A) given for design points in sub -basins. Intensities (1) were calculated for the initial storm event at 2-year interval for all sub -basins and at the 100-year interval for the major basins, using the Rainfall Intensity versus Time Curves (Figure 3-1 of the City of Fort Collins Storm Drainage Design Criteria and Construction Standards; see Appendix A). Post development Time of Concentration calculations for each sub -basin, corresponding rainfall intensities, composite runoff coefficients, and storm flows for the 2-year and 100-year storms for each sub -basin are provided in the Appendix. Routed storm flows through each sub -basin using the Rational Method procedure, are also provided in the Appendix. . Pipe sizing, flow capacities and velocities were estimated using computer program, Flowmaster v5.0, by Haestad Methods, Inc. d RUNOFF AND DETENTION Runoff rates for the various design points have been shown on the included Developed Drainage Map. Calculations showing how the runoff rates were determined are shown in the Rational Method procedure (See Appendix). The onsite detention pond volume of 1.25 acre-ft (54,000 cubic feet) and release rate of 1.5 cfs was calculated using an inflow hydrograph (See Appendix). At these volumes. the required one -foot freeboard has been provided. Proposed flows from this pond are in conformance with the "1999 Final Report for Hydrologic Model Update for the Foothills Basin Master Drainage Plan" STREETS, OPEN CHANNEL FLOW, AND CULVERTS No street flows are anticipated to enter the site from the drainage on West Horsetooth Road with the installation of an intersection crosspan. Runoff from the site will flow overland across parking lots, via gutters into the pond or via grass swales, and into proposed storm sewers then to the onsite detention pond. Fort Collins VOA, Elderly Housing Project — Drainage & Erosion Control Report 3 ' PROPOSED (DEVELOPED) DRAINAGE ' DRAINAGE DESIGN CRITERIA All proposed inlets have been designed to convey the initial storm with a majority I handling the 100-year event flows. The detention pond has been designed with sufficient storage volume to limit the 100-year release rate to 1.5 cfs as designated in the "1999 Final Report for Hydrologic Model Update for the Foothills Basin Master ' Drainage Plan" 2. The onsite drainage and storm sewer system has been designed according to the "City ' of Fort Collins Storm Drainage Design Criteria and Construction Standards."3 The attached Developed Drainage Map shows the resulting drainage and stormsewer system, including sub -basin designations and design points. (For calculations, See ' Appendix A) BASINS AND SUB -BASINS The proposed site has been divided into a single major drainage basin as well as several sub -basins. Please refer to the Developed Drainage Map (See Figure 1). The major basin drains into the onsite detention pond. Sub -basin boundaries were established based on watershed tributary areas. Runoff from the site will flow overland across parking lots, via gutters into the pond or via grass swales, and into proposed storm sewers to the onsite detention pond. Sub -basins A, B, and D each flow overland through grass across a parking lot to 4' Type R inlets. Flows from each of these inlets are routed into the storm sewer network connecting sub -basins C, E, F, G and H. Sub -basins C and G capture overland flows between the irrigation ditch top of bank and the grass area behind each building in area inlets. Piped flows from sub -basins D, E, and F enter the storm sewer network at design point 7, the collection point for sub basin G. Sub -basins E and F collect Kunz Court street flows in 4' Type R inlets and combine with flows from sub -basin D in the storm sewer system. Flows from sub -basins D, E, and F enter the storm sewer network at design point 7, the collection point for sub basin G. Sub -basins H captures overland flow from between the irrigation ditch top of bank and the grass areas behind each building in an area drain. Flows combine with piped flows from sub -basins A, B, C, D, E, F, and G at design point 8, where they are conveyed to the onsite detention pond at design point 15, the collection point for sub - basin O. Sub -basins I and K each flow overland through grass across a parking lot to 4' Type R inlets. Flows from each of these inlets are routed into the storm sewer network connecting sub -basins J, L, M and N. Sub -basins J, L, M and N collect Kunz Court street flows in 4' Type R inlets. Drainage from these sub —basins combine with flows from sub -basins I and K in the Fort Collins VOA, Elderly Housing Project— Drainage & Erosion Control Report 2 DRAINAGE & EROSION CONTROL REPORT INTRODUCTION GENERAL LOCATION AND DESCRIPTION The Fort Collins Volunteers of America propose to construct several four and six -unit elderly multi -family housing units in the City of Fort Collins. Construction will include widening of Horsetooth Road, a cul-de-sac providing access within the site, I overlot grading for residential construction, parking lots, sidewalks, utility infrastructure work and a detention pond. The 8.69-acre parcel is located south of the intersection of West Horsetooth Road and I Seneca Street. The property is bounded to the north by West Horsetooth Road, west and Westfield Park Subdivision, and east by Skyline Acres Subdivision. Zoning for the site is low density mixed use. IThe site slopes generally from west to east, and varies in elevation from 5103 to 5096 feet. Currently the site is native farmland with trees and open pasture. I PROPOSED PROJECT The proposed onsite development consists of 11 multi -family housing structures and a community center with dedicated City street access ending in a cul-de-sac. Site construction consists of parking lots, detached sidewalks, water and sewer mains, and a private storm sewer network including detention. In conjunction with site development, West Horsetooth Road will be widened incorporating a detached sidewalk as part of the design. Easements for the proposed public improvements will be granted as required by the City of Fort Collins. HISTORIC DRAINAGE Historic drainage is described in the "1997 Foothills Master Drainage Plan Update and Westfield Park PUD Regional Detention Pond Analysis" '(See Appendix B). The master plan update depicted the proposed site as the Burr property and incorporated it into the MODSWMM computer model, an updated version of Denver Urban Storm Drainage and Flood Control District's Storm . Water Management Model (UDSWM2PC). 'Due to constriction in the downstream storm sewer piping, this model determined that the 100-year release rate for the Burr property could not exceed 1.5 cubic feet per second (cfs). A storm sewer line was run east across the Burr property to connect the Westfield Park detention pond to the Skyline Acres Subdivision storm sewer system. This storm sewer provided adequate capacity for the maximum discharge of 1.5 cfs allowed for the Burr property. Fort Collins VOA, Elderly Housing Project — Drainage & Erosion Control Report CONTENTS DRAINAGE & EROSION CONTROL REPORT Contents...............................................................................................................1 Introduction.........................................................................................................1 Historic Drainage............................................................ ......:........... ................... 1 Proposed (Developed) Drainage....................................................................2 Irrigation Ditches and Laterals..........................................................................4 Stormwater Management Plan........................................................................4 Conclusions..........................................................................................................4 References...........................................................................................................5 APPENDIX A APPENDIX B Fort Collins VOA, Elderly Housing Project — Drainage & Erosion Control Report Drainage & Erosion Control Report Volunteers of America Elderly Housing Project in Fort Collins, Colorado JVA, Inc. Consulting Engineers 1319 Spruce Street Boulder, CO 80302 (303) 444-1951 I fax (303) 444-1957 JVA Project No. 1084c I July, 2001 This report (plan) amending the 1997 Foothills Master Drainage Plan Update and Westfield Park PUD Regional Detention Pond Analysis was prepared by me (or under my direct supervision) in accordance with the provisions of City Of Fort Collins Storm Drainage Design Criteria and Construction Standards, and was designed to comply with the provisions thereof. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. Kevin A. Tone Registered Professional Engineer State of Colorado No. 28699 If you have any questions regarding this submission, please give me a call. Very truly yours,. NA, Inc. Curtis Kostecki Project Engineer I cc: Robert A. Donahue - TSP Five Architects .....MMMMM�� - JVA. Incorporated JI 1%%;FN,%;'1' 1319 Spruce Street Boulder, CO 80302 Ph: 303.444.1951 Fax 303.444.1957 July 24, 2001 Toll Free: 877.444.1951 Mr.Glen Schlueter, P.E. Web site: City of Fort Collins, Civil Engineer www.jvajva.com 700 Wood Street E-mailinfo@jvajva.com Fort Collins, CO 80522-0580 RE: Drainage Study for the Fort Collins VOA Elderly Housing Project Principals JVA Job # 1084c Robert B. Hunnes David M. Houdeshell Dear Glen: Thomas S. Soell JVA has completed the design of the storm drainage system for the Fort Collins Structural Engineering VOA Elderly Housing Project off West Horsetooth Road across from Seneca Street. ChristopherJ. Chop The proposed site is located within Basin G as designated in the Foothills Basin Mark C. Cormier Master Plan. The 1997 Foothills Master Drainage Plan Update and Westfield Park Lara Hirsch PUD Regional Detention Pond Analysis analyzed Basin G with a SWMM model, Michael R. Hope referencing the proposed site as the Burr Property, and determined a maximum 100- Nancy R. Hudson year release rate from the site of 1.5 cfs. JVA has designed the detention facility Ron L. Lindburg with enough volume for the 100-year release rate of 1.5 cfs with 1-foot freeboard as Natalie A. Mozer-Reno required by the City of Fort Collins. The site requirements for this restricted release Oliver W. Rice rate have drastically increased the detention volume required and limited the area Thomas P. Skinner available for site development and usable landscaped areas. On behalf of the VOA, Sarah E. Watts JVA requests that the required water quality capture volume of 3484 cubic feet (.08 Charles B. Wilkerson acre-feet) be included in the required 100-year detention volume provided. A water quality outlet will be installed at this pond and connected to the storm sewer crossing Civil Engineering the site. Kevin A. Tone Michael R. Kramer The overflow from the Westfield Park detention pond is routed east across the VOA site through parking areas. After crossing the site, overflow runoff enters into the Office Manager Brook Drive right of way, the historic overflow location for the Westfield Park Cindera L. Ward Detention Pond. West of the VOA site is the Pleasant Lake & Valley Irrigation Ditch. Presently, three laterals from this ditch cross the site heading eastward and feed irrigation ditches located within the Skyline Acres Subdivision. Redesign and relocation of the laterals supplying irrigation water to the eastern properties has been coordinated with the ditch company and residents of Skyline Acres. The following Drainage and Erosion Control Report, and attached drainage map for the above referenced project, have been produced in accordance with the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, and complies with provisions thereof. It is our understanding that the information provided herein will be all that is required to complete your review of the drainage calculations for this project. B 0 U L D E R I F 0 R T C 0 L L I N S I W I N T E R P A R K MARCH,,2001