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Home My WebLink AboutADVANCE AUTO PARTS - FDP - 26-07/A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTr` "F P Final Drainage Report Advance Auto Parts Fort Collins, Colorado 6.0 CONCLUSIONS This final drainage report has been prepared in compliance with Reference 4. The drainage improvements designed in this report will transport runoff to an onsite detention and water _J quality facility that will release flows to City storm sewer which drains to the Poudre River. .. With the exception of the variance request regarding the building finished floor elevation, this development is in compliance with Chapter 10 of the City Code, regarding floodplain regulations. , 9 Final Drainage Report Advance Auto Parts Fort Collins, Colorado Erosion Control Cost and Quantity Estimates Method of Erosion Control Quantity Cost Silt fence 484 LF $2/lf Inlet protection 1 EA $150/ea Sediment Trap 1 EA $300/ea Vehicle tracking control 1 EA 500/ea Total: $1,918 Escrow = Total x 1.5 = $2,877 E 9 Final Drainage Report Advance Auto Parts Fort Collins, Colorado 5.0 EROSION CONTROL MEASURES Vehicle Tracking Control A stabilized construction entrance will be provided at the access to the North College Avenue, with base material consisting of 6" coarse aggregate. Construction vehicles are prohibited from tracking mud or debris onto City roads and the contractor shall be responsible for immediate correction of any such violation. Any sediment by runoff or by vehicles tracking onto the paved surface shall be removed by shoveling or sweeping and be transported to a controlled sediment disposal area. Erosion Control Measures Sedimentation will be controlled on -site by use of inlet protection, sediment fence, and a temporary sediment trap. The contractor shall periodically remove sediment from and around the barriers as is necessary to maintain their proper functioning. Sediment fence shall be installed in all areas where the off -site area is lower in elevation than the adjacent on -site area. This will be done to keep sediment from leaving the construction site. Disturbed areas not to be covered by asphalt, concrete, or approved landscaping will be reseeded with an approved seeding mixture. Inlet protection will be provided to keep a majority of the sediment carried with the runoff out of the storm sewer system. A temporary sediment trap shall be constructed within the water quality facility. All temporary and permanent erosion and sediment control practices shall be maintained and repaired by the owner during the construction phase and until final stabilization has been achieved as needed to assure continued performance of their intended function. All facilities must be inspected by the owner or owner's representative following each heavy precipitation or snowmelt event that results in runoff. Erosion control effectiveness calculations are provided in the Appendix to this report. 7 Final Drainage Report Advance Auto Parts Fort Collins, Colorado The proposed water quality facility will provide 5,729 ft3 of storage. An outlet structure designed in compliance with city criteria will release regulated flows to an existing storm sewer along the east side of College Avenue. Said storm sewer outfalls to the Poudre River. 6 .N w� Final Drainage Report r- vnr' Advance Auto Parts Fort Collins Colorado Specific Details Basin A (0.16 Acres) contains the proposed building. The basin will drain east to the detention and water quality facility at Design Point 1. The 5-year and 100-year flow rates at Design Point 1 are Q5= 0.5 and Qioo= 1.3 cfs, respectively. Basin B (0.33 acres) contains the majority of the parking area. The basin will drain to the inlet at Design Point 2. The 5-year and 100-year flow rates at Design Point 2 are Q5= 0.9 and Qioo= 2.6 cfs, respectively. Basin C (0.05 acres) contains the detention and water quality facility. The basin will drain to an outlet structure at Design Point 3. The 5-year and 100-year flow rates at Design Point 3 are Q5= 1.4 and Qioo= 4.2 cfs, respectively. Basin D (0.04 acres) covers the west edge of the site. The basin could not be drain to the detention and water quality facility. Therefore, it will sheetflows to the alley at Design Point 4. The 5-year and 100-year flow rates at Design Point 2 are Q5= 0.1 and Qioo= 0.2 cfs, respectively. Basin E (0.01 acres) contains the southeast corner. The basin will drain to the curb and ggutter in North College Avenue at Design Point 5. The 5-year and 100-year now rates at Design Point 2 are Q5= 0.1 and Qioo= 0.1 cfs, respectively. The water quality capture volume is based upon a tributary area of 0.54 acres. The detention volume is based on then entire site area of 0.58 acres. Total provided detention and water quality volumes are as follows: WQCV 786 CF Elevation = 66.75 WQCV + 100-yr detention volume 5,729 CF Elevation = 69.30 The pond will release at a peak rate of 0.11 cfs during the 100-year event. The flow will be released through an 18" RCP to the existing storm sewer in North College Avenue. An emergency overflow weir with a spillway elevation of 69.30 has been provided adjacent to gNorth College Avenue. The building is more than one foot above the overflow elevation. 5 Final Drainage Report Advance Auto Parts Fort Collins Colorado 4.0 SITE DRAINAGE DESIGN General Concept The site grading has been designed to divert runoff away from the building and into an onsite detention pond, valley pans and curb and gutter. A majority of onsite runoff will be carried on the surface to an inlet on the south side of the site. Storm sewer will convey flows to the detention and water quality facility. Flood Details As previously mentioned, according to FEMA flood insurance rate map 08069C0977 F, dated December 19, 2006 this site is located in an area defined as, "special. flood hazard areas subject to inundation by the 1% chance flood." The BFE line on the FEMA map at the south boundary of the project site is 4975, based on NAVD88 datum. This is incorrect. The FEMA profile actually shows the BFE at that location to be at 4972.8 (NAVD88). City of Fort Collins datum and the project benchmark are based on the NGVD29 datum. When converted to project elevations this results in a BFE of 4969.8. This lead to a BFE of 4970 at the upstream edge of the building. Therefore, the building top of foundation as well as HVAC and electrical items have been located above elevation 4971.0 (BFE + 12"). City regulations require the building foundation be placed above BFE + 18". Therefore, we are requesting a variance from this regulation. No other structures will be located within the 100-year floodplain. No floatable materials will be located onsite and the trash enclosure will be bolted down. A floodplain use permit will be required for each structure and each site construction element in the floodplain. A FEMA elevation certificate will be completed and approved before the CO is issued. The building foundation will be a slab on grade. 10 All chemicals being used have been shown to not be hazardous, flammable, explosive, toxic and/or water reactive. MSDS sheets will be submitted for the chemicals to be used. This 19 site will not be considered a critical facility. 4 Final Drainage Report Advance Auto Parts Fort Collins, Colorado 3.0 DRAINAGE DESIGN CRITERIA Development Criteria Reference and Constraints No previous drainage reports were found which affect the project site. No wetlands have been found on the project site. City code requires detention and water quality be provided for the project site The detention facility shall have a single release rate of 0.2 cfs per acre. Hydrologic and Hydraulic Criteria =� The hydrologic analysis and hydraulic design for the site are based on the criteria established by the Urban Storm Drainage Criteria Manual (Urban Drainage and Flood Control District, 2005/2006) and the City of Fort Collins Storm Drainage Design and Technical Criteria. Basin imperviousness was obtained from Table RO-3, runoff coefficients were obtained from Table RO-5, rainfall intensity was obtained from FigureRA-2, and runoff velocities were obtained from Figure RO-1. Times of concentration were determined using form SF-2, and runoff flowrates were determined using form SF-3. The rational method was used to compute the 5-year and 100-year developed flowrates as required by City criteria. The detention volume was calculated per City criteria. 3 Final Drainage Report Advance Auto Parts Fort Collins, Colorado 2.0 DRAINAGE BASINS AND SUB -BASINS Major Basin Description The site currently sheetflows southwesterly to the 20' alley and is tributary to Cache La Poudre River, which is located approximately 0.2 miles to the south. There are no visible irrigation facilities associated with the site, and no off -site drainage impacts the project site. There are no known wetlands on the project site. According to FEMA flood insurance rate map 08069CO977 F, dated December 19, 2006 this site is located in an area defined as, "base flood elevations determined special flood hazard areas subject to inundation ,by the 1% chance flood" (Figure 2). See Section 4.0 for a discussion of flood details. Sub -Basin Description The project site has been divided into the follow 5 sub -basins for analysis: Basin A consists of the proposed building. It drains to the proposed detention pond. Basin B consists of the majority of the parking area. It drains to a proposed onsite storm inlet. Basin C consists of the detention and water quality facility. It drains to the outlet structure. Basin D consists of the west edge of the site. It sheetflows to the alley. Basin E consists of the southeast corner of the site. It sheetflows to North College Avenue. 1 A Final Drainage Report Advance Auto Parts Fort Collins, Colorado 1.0 GENERAL LOCATION AND SITE DESCRIPTION Advance Auto Parts is located in the City of Fort Collins, Larimer County, Colorado, southwest of the intersection of Hemlock Street and North College Avenue, 'in the southeast one quarter of Section 2, Township 7 North, Range 69 West, of the 6tb Principal Meridian. The 0.64 acre site is bounded on the north by Hemlock Street, on the east by North College Avenue, on the south by Lot 7, Block 3, Riverside Park and on the west by an alley. The site currently sheetflows primarily southwest to the alley at slopes of approximately 0.7% The lot is currently undeveloped. Proposed development consists of a proposed building, along with a paved parking lot, detention pond and landscaped areas. According to the Soil Survey of Larimer County, Colorado, prepared by the U.S. Department of Agriculture Soil Conservation Service, the type of soil that underlies the parcel is Nunn Clay Loam and it belongs to the hydrological soil group C. 1 " Final Drainage Report Advance Auto Parts Fort Collins, Colorado CERTIFICATIONS ENGINEER This report for the final drainage design of Advance Auto Parts was prepared by me (or under my direct supervision) in accordance with the provisions of the City of Fort Collins Storm Drainage Design Criteria and Construction Standards and Urban Storm Drainage Criteria Manual (Urban Drainage and Flood Control District, 2004/2005), 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 design by others. p0 R� oPN Brian Krombein, P.E. �6 Colorado Registered Professional Enginee 34294 For and on behalf of Jones Engineering AsIAn ii TABLE OF CONTENTS Final Drainage Report Advance Auto Parts Fort Collins. Colorado Page 1.0 GENERAL LOCATION AND SITE DESCRIPTION.....................................................1 2.0 DRAINAGE BASINS AND SUB-BASINS.....................................................................2 3.0 DRAINAGE DESIGN CRITERIA..................................................................................3 4.0 SITE DRAINAGE DESIGN............................................................................................4 5.0 EROSION CONTROL MEASURES..............................................................................6 6.0 CONCLUSIONS..............................................................................................................8 7.0 REFERENCES................................................................................................................9 i 4 FINAL DRAINAGE REPORT ADVANCE AUTO PARTS FORT COLLINS, COLORADO Prepared by Jones Engineering Associates, Inc. 2120 W. Littleton Blvd., Suite 205 Littleton, Colorado 80120 (303) 738-0283 October 26, 2007 Project No. 7023