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Home My WebLink AboutHARMONY SAFEWAY MARKETPLACE, LOT 6, FUEL FACILITY - PDP - 33-94F - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTa W 0 a J Z N N Qi Z W Q kA >- >- V) Q Z z Ox O 0 a2i 3N17Mi O�11b� 31j/O yd NOINn W �a W F- 00 N 3AV "V431 VI W Q W C.� W J J O U O t- 0 APPENDIX provided through the installation of a water quality outlet designed to handle both the WQCV and twenty percent increase to account for sedimentation. The details and calculations for the outlet structure have been provided on the drainage plan and within the Appendix Section of this report. To provide permanent stabilization measures, landscaping will be installed throughout 46.0% of the site. The permanent landscaping shall include a wide variety of deciduous and evergreen trees and shrubs. Before any site runoff enters the public storm sewer, grass will be installed within the detention pond. These measures will intercept and settle out sediments before they reach the outlet structure of the detention pond and public storm sewer. These permanent stabilization measures shall be installed prior to the removal of any temporary erosion control devices utilized during construction. References 1. Storm Drainage Design Criteria and Construction Standards, City of Fort Collins, May 1984 (with current revisions). 2. Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District, March, 1986 (with current revisions). N rl Erosion Control Temporary erosion control for this site consists of silt fence, hay bales and vehicular tracking control devices. Silt fencing is to be placed around the entire site except at the construction entrance where there is a vehicular tracking control measure. The exact location of the gravel entrance shall be coordinated with the construction manager and the City public inspector. Prior to initiating the overlot grading, all silt fence shall be installed in accordance to the approved Erosion Control Plan. Curb inlet gravel filters shall be placed in front of the two inlet structures. Please refer to the Grading, Drainage and Erosion Control Plans for specific location of erosion control devices and notes. The erosion control measures will be inspected weekly during construction. Silt fences will be cleaned of excessive sediment and replaced if necessary. Straw bale barriers and curb inlet filters will be checked for sabotage and bypass and replaced or increased as necessary. In areas where building construction has not begun, bare soils will be mulched and checked regularly and areas where it was lost or damaged will be remulched within seven working days when necessary. 9 During construction, stormwater runoff will be directed through straw bale barriers to filter sediments prior to entering the access road and the grass lined swale. All runoff leaving the site will be limited to non -erosive velocity to limit land disturbance. The perimeter controls will be installed prior to any site grading. The intent of the erosion control measures listed above and a described in this report shall be strictly adhered to during all construction. Erosion Control measures for this site can be found in the Appendix of this report. Storm Water Quality Control Water Quality Capture Volume (WQCV) has been calculated for the detention facility based upon the criteria listed in Volume 3 of the Urban Storm Drainage Criteria Manual. This has been r %I detention pond located in the western portion of the lot. Discharges for the 10-year and 100-year -� storms were calculated to be 1.60 cfs and 4.16 cfs, respectively. i Basin OS-S1, 0.401 acres consisting of landscaping, flows predominantly from the west to the i east via a grass lined swale and then offsite. Discharges for the 10-year and 100-year storms were ;i calculated to be 0.22 cfs and 0.57 cfs, respectively. , Basin OS-S2, 0.070 acres consisting of landscaping and paving, flows predominantly from the ' northwest to the southeast to the inlet located just north of the access to the overall site. Discharges for the 10-year and 100-year storms were calculated to be 0.12 cfs and 0.31 cfs, respectively. Basin OS-N1, 0.112 acres consisting of landscaping and paving, flows predominantly from the �I south to the north into and existing inlet on the access road. Discharges for the 10-year and 100- y year storms were calculated to be 0.28 cfs and 0.71 cfs, respectively. N Basin OS-N2, 0.173 acres consisting of landscaping and paving, flows predominantly from the south to the north into and existing inlet on the access road. Discharges for the 10-year and 100- year storms were calculated to be 0.49 cfs and 1.19 cfs, respectively. Detention An overall development detention pond is provided for the northern portion of the site, basins l OS-N1 and OS-N2. A grass lined swale is provided on the south portion of the site to cant' flows IJ to the Golden Meadows Regional detention pond. As mentioned in the Final Drainage Report j for Harmony Safeway Marketplace P. U.D., a release rate of 4.74 cfs per acre is allowed for the I� S-2 drainage basin. The portion of the proposed site that lies in the S-2 basin is 0.965 acres (basins S-A & OS-S1). By multiplying 4.74 cfs/acre times 0.965 acres, this results in an allowed runoff from the proposed 2 basins (S-A & OS-S1) of 4.57 cfs. Proposed basins OS-S2, OS-N1 and OS-N2 drain into the existing basins as designed in the above mentioned report. The C I 0 4 I Report nage Report for Com an Date Wyatt & Associates 3/97 Marketplace rSafeway eport and Plans) 2. Golden Meadows fifth Stewart & Associates, Inc. 12/80 Filing Storm Drainage Report 3 Drainage Criteria Manual, Wright -McLaughlin 3/69 Urban Drainage and Flood Engineers Control District Hydrologic Criteria Runoff for the minor storm, 10-year frequency, and the major storm, 100-year frequency, were calculated using the rational method. Where applicable, composite runoff coefficients were calculated for the individual basins by using the recommended runoff coefficients as indicated in Table 3-3 and Table 3-4 of the Storm Draina e Desi n Criteria and Construction Standards, City of Fort Collins. Times of concentration were calculated using the overland/travel time and urbanized basin method with the minimum time used for subsequent calculations. Rainfall intensities were derived from the City of Fort Collins Rainfall Intensity Duration Curve and Tables, 1999. Runoff Coefficients, applicable charts and graphs are included in the Appendix of this report. Drainage Plan General Concept The proposed site will be subdivided into five major basins, S-A, OS-S1, OS-S2, OS-Nl, AND OS-N2. The site is composed of paved, roofed, and landscaped areas. Specific Details ng of roofed, pavement and landscaped surface characteristics, Basin S-A, 0.564 acres consisti flows predominantly from the north portion of the basin toward the south, via a chase drain to the 3 The site is unimproved, void of trees, and consists of native grasses and weed vegetation. The north portion of the site is relatively flat and the south portion of the site is a developed grass lined swale which conveys runoff from the southern lots of the subdivision offsite to the Golden Meadows Regional detention pond. A small portion of the site will drain northerly to the Harmony Safeway Marketplace detention pond, which then flows to the Golden Meadows Regional detention pond. Existing improvements surrounding the site consist of landscaping on the west, south and east sides and parking/access road on the north. The site to the north detains runoff into two inlets on the access road which flows to the developed detention pond for the overall site, therefore there will not be any off -site runoff from the north. The off -site runoff from the sites to the west will pass through the site via the grass lined swale provided on the southern portion of the site. Drainage Patterns Through Property The existing site currently is flat on the northern portion and slopes to the south on the southern portion. Outfalls Downstream from Property The runoff from this property is conveyed via a grass lined swale on the south side of the site and also via the existing storm sewer system to the overall drainage pond. Both. of these flows are conveyed via several other systems to the Golden Meadows Regional detention pond. All of the above mentioned conveyance systems are located within existing drainage easements. Desilln Criteria This report was prepared using criteria as outlined in the City of Fort Collins "Storm Drainage Design & Technical Criteria" and the Urban Drainage and Flood Control District's (UDFCD) "Urban Storm Drainage Criteria Manual". Several plans and reports for this site and the surrounding sites were reviewed. Below is a list of this information. 2 Introduction This final drainage report is being prepared for Safeway, Inc., the developer of the site, to fulfill the drainage requirements of the City of Fort Collins, State of Colorado. This report is to establish the site's final drainage characteristics. The report analyzes onsite runoff for the minor i (10-year frequency) and major (100-year frequency) storms and routes these flows through the isite. Specific details are contained within this study and are shown on the final grading and final drainage plan. Location Safeway Fueling Facility at Harmony Safeway Marketplace is a 1.32 acre site located in the southwest one -quarter. of Section 31, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado, also known as Lot 6, Harmony Safeway Marketplace P.U.D. Plan. The site is bounded on the west by landscaping, on the north by parking, on the south by Harmony Road, and on the east by the Safeway Marketplace access road. The site is north of Harmony Road between Wheaton Drive and McMurray Avenue. ( Proposed Development The proposed site will consist of two phases. Phase I will be to construct the canopy, install 5 multi -product dispensers, construct a kiosk, and install perimeter landscaping including sodding the Phase II area. Phase II will consist of removing the kiosk and replacing it with a sixth multi- product dispenser, construct the c-store, paint parking spaces, and construct the sidewalk in front of the c-store with connection to the existing sidewalk to the south. The developed site will j� consist of 46.9% (composite) impervious area. Historic Drainage Overall Basin Description i� The site is located within the Fox Meadows Drainage Basin. The site has been addressed as a portion of the Golden Meadows Fifth Filing Storm Drainage Report, by Stewart and Associates, I� dated December 22, 1980, and also addressed in the Final Drainage Report for Harmony r Safeway Marketplace P. U.D., by Wyatt and Associates, revised March 7, 1997. TABLE OF CONTENTS SECTION PAGE NO. INTRODUCTION 1 HISTORIC DRAINAGE DRAINAGE CRITERIA 2 DRAINAGE PLAN 3 CONCLUSION 5 REFERENCES 7 APPENDIX A-1 Vicinity Map A-2 Runoff Coefficients m A-3 Overland Time of Flow Curves A-4 Estimate of Average Flow Velocity A-5 Intensity -Duration -Frequency Curves A-6 Intensity -Duration -Frequency Tables A-7 Developed Runoff Calculations A-8 Allowable Release Rate A-9 Detention Storage Volumes 100-year A-10 Detention Pond Stage Storage Calculations A-11 Detention Pond Orifice Calculations A-12 Water Quality Capture Volume Calculations A-13 Water Quality Outlet Detail A-14 Figure EDB-2 Water Quality Capture Volume Curves A-15 Figure EDB-3 Water Quality Outlet Sizing A-16 Figure 5 Orifice Plate Perforation Sizing A-17 Chase Drain Calculations A-18 Structure Outlet Pipe Calculations A-19 Erosion Control Rainfall Performance Standard Evaluation A-20 Erosion Control Effectiveness Calculations A-21 Construction Sequence A-22 Erosion Control Escrow Calculation A-23 Excerpts from Final Drainage Report for Harmony Safeway Marketplace P.U.D. Final Drainage Plan — Back Pocket of Report Erosion Control Plan — Back Pocket of Report I' Date: Project Name: Project Number: June 25, 2000 Safeway Fueling Facility — Harmony Safeway Marketplace SA06.GRA ENGINEER'S STATEMENT: The enclosed drainage report and exhibits were prepared by me or under my direct supervision and is correct to the best of my knowledge and belief. Said drainage report has been prepared in accordance with the applicable City of Fort Collins criteria and is in conformance with the master plan of drainage for the effected area. L- G. ��L David A. Guetig, P.E. Date Registered Professional Engineer State of Colorado No. 30020 Galloway Romero & Associates Design Engineering Planning Final Drainage Report for Safeway Fueling Facility Lot 6, Harmony Safeway Marketplace P.U.D. APPROVED FOR ONE YEAR FROM THIS DATE Director of Public Works Director of Utilities Date: June 25, 2000 Prepared for: Safeway, Inc. 6900 South Yosemite Street Englewood, CO 80112-1412 Phone: (303) 843-7600 Prepared by: Galloway, Romero & Associates 5350 DTC Parkway Englewood, CO 80111 (303)770-8884 (Fax) 770-3636 Attn: Lisa C. Johnson Date Date IIWO O L