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Home My WebLink AboutSAVE MOR SELF STORAGE PUD PRELIMINARY AND FINAL - 27 93 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTREFERENCES 1. Storm Drainage Design Criteria and Construction Standards, City of Fort Collins, May 1984. 2. Topography, Northwest Quarter Section 12, Township 7 North, Range 69 West, ARIX. 3. Drainage Report - Catholic Community Services - Tract A - Linden Tech Center, CDS Engineering Corporation, July 21, 1988. CONCLUSIONS AND RECOMMENDATIONS After reviewing the existing drainage information and site conditions, the following conclusions can be made. 1. Runoff from this site will fall off the centerline of each building, through a drain pipe, into the two -foot concrete pan. The pan drainage system will convey the flow to designated concentration points. 2. No on -site detention is necessary for developments within the Poudre River drainage basin. The majority of stormwater runoff will flow into the Coy ditch. All outlets to Coy Ditch will be protected to assure minimal damage to the canal's embankment. 3. Only a portion of this site is in the 100-year flood plain of the Poudre River. All buildings in this area are greater than 18" above the 100-year flood water surface elevations. Figure 1 shows the 100-year flood plain and water surface elevations from the FIRM (July 1979). A cross sectional detail of the flood fringe is shown on the drainage plans. sill FA Oft EROSION CONTROL This project is located within an area of low wind and moderate rainfall erosion potential as identified by the City of Fort Collins wind and rainfall erodibility maps. Wind Erosion No wind erosion protection measures need to be taken since the site will be completely covered by buildings and asphalt driveways. The site will also be protected by fences and landscaping around the perimeter. Water Erosion Net effectiveness calculations attached show that no erosion control measures need to be taken. However, it is suggested that silt fences be placed along the northern boundary of Basin D and the western boundary of Basin A. This will prevent the flow of sediment into Coy Ditch and minimize erosion of the fill slope material onto the bike path. The landscaped areas and fences will also act as buffers to control erosion caused by stormwater runoff after construction. All erosion control calculations and a cost estimate are shown in Appendix C of this report. -9- D is broken down into four subbasins which flow directly into the Coy ditch. The respective design points are 6, 7, 8 and 9 which outlet from concrete pans down ripraped embankments to the ditch. All pertinent drainage calculations are located in Appendix A of .this report. -7- 1 6) (6) lows entering the Poudre River upstream at Linden Street bridge. No on -site detention is ' required for this site as per the master plan, and the majority of runoff from this site will flow into the Coy ditch. Permission to drain stormwater runoff into Coy Ditch was agreed upon ' on June 20, 1980. The agreement letter is shown in Appendix A. 1 DRAINAGE UNDER DEVELOPED CONDITIONS The development of the fourteen storage units will significantly impact the runoff from this site. The majority of the site will be covered by buildings and asphalt driveways which increases the runoff coefficient from 0.20 to 0.95. The driveways in between each of the storage units will be inverted with a two foot concrete pan at the thalweg(low point). The entire area will be graded to allow for positive drainage away from each storage unit. The concrete pans will convey the runoff to various concentration points that outlet onto Linden Center Drive or the Coy ditch. A complete drainage and erosion control plan is available in the Back Pocket of this report, please refer to this sheet for the following discussion. 1 The drainage for the, existing site is broken down into four basins. Basin A concentrates at the west central portion of the basin, design point 1. The flow from this point will outlet into an .6" ADS pipe under the existing bike path. The runoff from Basin B will concentrate at design point 2 which will flow south onto Linden Center Drive. Basin C is broken down into three subbasins which all flow east onto Linden Center Drive. The respective design points are 3, 4 and 5 which will flow out 2' metal sidewalk culverts. Basin ASPHALT BIKE PATH PM so 2W LINDEN TECH CENTER.'' DRAINAGE SCHEMATIC E HISTORIC DRAINAGE Adjacent properties include a storage -unit facility(similartothis proposed development), a Catholic Community Services Center, and Fort Ram Nightclub. These properties will not contribute any off -site flow to this project. A power substation occupies the property immediately to the west of the site. Off -site flows from this area are contained and directed to. Linden Center Drive via the asphalt access road. The Coy ditch, an open irrigation channel, runs along the northern and eastern boundaries of the Linden Tech Center. This proposed development is relatively flat and supports a low grass ground cover. A runoff coefficient of 0.2 was chosen for historic conditions. The surface drainage for basin "A" flows to the northeast into the Poudre River (see figure 2). Runoff from basin "B" flows to the southeast onto Linden Center Drive. Drainage basin "C" flows to the northeast into Coy ditch. Grades of approximately 0.5% are common across the drainage basins with increasingly steep grades of 1 - 10% in the most westerly section of basin "A". MASTER DRAINAGE This site is located within the Poudre River drainage basin. The Coy ditch diverts flows from the Poudre River near the intersection of Vine Street and College Avenue with return -4- r� 1 (1.21 acres). The existing site is covered with native prairie grass. A railroad siding runs east - west through parcel B and will be abandoned as part of this project. The site is located in the Northwest Quarter of Section 12, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, Larimer County, Colorado. (See Figure 1) IThis site is zoned General Industrial (I-G) and is in an area of minimal activity. The area is permeable except for a 40' X 30' asphalt access road for a power substation west of Parcel C. Based on field verified topography, there is a railroad spur track and subgrade which forms a drainage boundary that runs east and west, to divide Parcel A from Parcel C. The portion of land containing the spur track is in Parcel B which historically splits the site into two main basins (See Figure 2). The southwestern portion of the site (Parcel D) is very flat with the exception of the most westerly 60' of Parcel D which slopes off at 10% to a pedestrian path and the Gustav -Swanson natural area along the Poudre River. DRAINAGE CRITERIA This runoff from each of the subbasins was determined from the Rational Method. The Rational Formula is a widely accepted predictor of runoff from basins less than 200 acres. Flow capacities for open channels are determined from Manning's equation. All runoff and roughness coefficients are derived from the City of Fort Collins' Storm Drainage Design Criteria and Construction Standards Manual. 0 Ik11 it PROJECT SITE VICINITY MAP N. T. S. FI&WZE 1 FINAL DRAINAGE & EROSION CONTROL REPORT FOR SAVE MOR SELF STORAGE FORT COLLINS, COLORADO INTRODUCTION The purpose of this drainage report is to provide drainage information for the development of a fourteen unit self storage complex and office along the west side of Linden Street between Linden Center Drive and the Coy ditch. This report was prepared to provide information for on and off -site drainage. All design specifications are prepared in accordance with the City. of Fort Collins Storm Drainage Design Criteria and Construction Standards. SITE DESCRIPTION The proposed site for the self -storage facility is located on North Linden Street on 4 parcels of land described as follows: a) Parcel A - a lot measuring 138,604 square feet (3.18 acres); b) Parcel B - a lot measuring 34,293 square feet (.79 acres); c) Parcel C - a lot measuring 81,746 square feet (1.88 acres); d) Parcel D - a lot measuring 52,827 square feet -1- E TABLE OF CONTENTS Introduction 1 Site Description 1 Drainage Criteria 3 Historic Drainage 4 Master Drainage 4 Drainage Under Developed Conditions 6 Erosion Control 9 Conclusions and Recommendations 10 Drainage and Erosion Control Back Pocket Figure 1 Vicinity Map 2 Figure 2 Drainage Schematic (Historic) 5 Appendix A Coy Ditch Discharge Agreement Appendix B Drainage Calculations Appendix C Erosion Control Calculations Ll FINAL DRAINAGE & EROSION CONTROL REPORT FOR SAVE MOR SELF STORAGE 26 APRIL 1993 PREPARED FOR: DARRELL KNUDSEN P.O. BOX 1001 TUSTIN, CA 92681 PREPARED BY: PARSONS & ASSOCIATES CONSULTING ENGINEERS 432 LINK LANE PLAZA FORT COLLINS, COLORADO 80524 (303) 221-2400 PROJECT NUMBER: 93.03 LTC 4