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Home My WebLink AboutIMPORT AUTO SALES, TOWING & STORAGE - PDP - 15-02B - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTEast Willox Lane Weld c Q LMN G 0 U °• r Bristlecone Drive o a............ z d o O. CN y n O O• U p I i d tln OS N Hickory Street v m Conifer Street SITE POLm CCN MMN I RL VICINITY MAP SCALE: 1 "= 1000' N d d 0 0 3 v m D: LMN VII. APPENDICES 1. Vicinity Map Soils Data FIRMette 2. Historic Storm Drainage Calculations 3. Proposed Storm Drainage Calculations 4. Detention Pond Calculations 5. Proposed Drainage Plan (insert) R. V1. REFERENCES 1. Urban Storm Drainage Criteria Manual Volumes I and 2, Urban Drainage and Flood Control District, June 2001, and Volume 3, September 1999. 2. City of Fort Collins Storm Drainage Design Criteria and IConstruction Standards, Department of Public Works and Water Utilities, Storm Drainage Division, May, 1984. 3. Soil Survey ofLarimer County Area, Colorado, U.S. r Department of Agriculture, Soil Conservation Service and 1 Forest Service, December, 1980. 4. Flood Insurance Rate Map No. 08069C0977F, Federal Emergency Management Agency, National Flood Insurance Program, December 19, 2006. VA USDCM. No adverse affects to surrounding properties are anticipated from the development of this site. The design, if properly maintained and constructed, conveys, releases and protects the quality of storm water runoff up to and including the 100-year storm event in a safe manner to protect life and limit damage to property. n 3. Design Storms a. Minor 10-year b. Major 100-year 4. Detention/ Storage Method Modified FAA C. Hydraulic Criteria The necessary pond volume was calculated utilizing Urban Drainage spreadsheets and the Modified FAA method. Water Quality will be provided, with the Catchment Volume being considered a portion of the total 100-year volume. The total required volume is 0.17 acre- feet. Release from the pond will be 0.22 cfs (0.2 cfs per tributary acre). IV. DRAINAGE FACILITY DESIGN Existing drainage patterns will. be maintained and utilized as practicality permits. The general pattern of flow is toward the west for Basin A and to the southeast for Basin B, to the pond. The outlet structure will be designed with a water quality catchment plate, 10- year weir, and 100-year top opening. Release will be at the allowable rate — 0.2 cfs per tributary acre. The proposed drainage and detention facilities will be privately owned and maintained. Erosion control measures will be utilized to mitigate erosion and control sediment. Standard Best Management Practices may include, but are not limited to, perimeter silt fencing, vehicle tracking control, and inlet/outlet protection. V. CONCLUSIONS The analysis and design of the storm drainage system for this project was prepared in accordance with the criteria set forth in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards and the W Flows will be carried via this swale to the gutter at Conifer Street, then east to the same inlet that currently receives historic flows from this portion of the Site. Appropriate drainage and construction easements will be acquired for the proposed swale, as the owner of this Site also owns the properties that bound it to the south and east. Outfall remains to Dry Creek. Developed Sub -basins The sub -basin delineation for the proposed site is the same as that done for historic calculations. Runoff from sub -basin A will be released undetained to Red Cedar Circle. Because the inlet that receives these flows is only 120' to the south, runoff from the Site will not increase the peak discharge to the inlet from the surrounding area. Runoff from sub -basin B will be captured in the on -site drainage system and detained prior to release into the proposed swale at the southeast corner of the Site. As previously stated these flows will be carried south to Conifer Street, east to an inlet in Conifer Street and then southeasterly in storm pipe to Dry Creek. M. DRAINAGE DESIGN CRITERIA A. Regulations The analysis and design of the storm drainage system for this project was prepared in accordance with the criteria set forth in the City of Fort Collins Storm Drainage Design Criteria and Construction Standards and the Urban Drainage and Flood Control District's Urban Storm Drainage Criteria Manual (USDCM. B. Hydrological Criteria 1. Design Rainfall 2. Runoff Method City of Fort Collins Rainfall Intensity -Duration -Frequency Table for the Rational Method (Figures 3-la and 3-1b) Rational 4 1 II. DRAINAGE BASINS AND SUB -BASINS A. Major Basin Description I This site lies within the Dry Creek drainage basin of the City of Ft. Collins. A portion of the Site is currently within the floodplain boundary, as evidenced by the FEMA Flood Insurance Rate Map — Community Panel Number 08069 0977 F dated December 19, 2006 (See FIRMette in Appendix). Per Glen Schlueter of the City of Fort Collins Stormwater Department, the Site is expected to be completely removed from the floodplain when the Dry Creek Physical Map Revision is approved by FEMA (expected in June, 2008). Until that 6 time, a floodplain use permit will be required for any work done in the FEMA 100-year floodplain. The use of auto storage is allowed in the floodplain. B. Sub -Basin Description The historic drainage patterns for this site are those that currently exist, as the Site is undeveloped. Existing and proposed drainage conditions and surface runoff are shown on the provided Drainage Plan. The entire Site ultimately drains to Dry Creek. Historical Basin A is the western portion of the Site that drains to the west onto Red Cedar Circle, as well as the east half of that street from the north to south property lines. Those flows are carried southward to an inlet at the intersection of Red Cedar Circle and Conifer Street approximately 120 feet away. Flows to that inlet are then carried via storm pipe east in Conifer Street and then South to Dry Creek. Basin B includes the remainder of the Site, which drains southeasterly and onto the adjacent vacant lot. Those flows eventually drain onto Conifer Street east to an inlet that feeds the same storm pipe and drains to Dry Creek. The Site receives no offsite flows. There is currently no onsite detention provided for the Site. With the proposed development, a detention pond will be constructed along the eastern boundary of the property to detain onsite developed runoff from Basin B. Runoff will be conveyed overland to the detention pond, and released at the allowable rate (0.2 cfs/acre) to a swale at the southeast corner of the Site. This proposed swale will be constructed along the eastern boundary line of the lot that lies south of the Site. 3 I. GENERAL LOCATION AND DESCRIPTION A. Location Import Auto Sales Towing and Storage (Project Site) is located in the northwest quarter of Section 1, Township 7 North, Range 69 West of the 6t' Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. It includes Lots 7 and 8, Block 4, Replat Number One of Evergreen Park in Fort Collins. The Site is bounded on the west by Red Cedar Circle and on the north, south and east by other industrial properties. The properties to the south and east are undeveloped at this time. The Site lies approximately 145 feet north of Conifer Street and approximately 600 feet east of North College Avenue. A Vicinity Map is provided in the Appendix. B. Description of Property The total Site area is 60,000 square feet or approximately 1.38 acres. It is currently vacant and is zoned I — Industrial District. Approximately 115 of the Site along its western boundary drains westward to Red Cedar Circle. The remainder of the Site drains in a southeasterly direction onto the adjacent vacant lot. Slopes range from 0-3% throughout most of the Site; however, the western portion that drains to Red Cedar Circle has slopes as great as 33%. This project proposes to erect a fence around the majority of the Site, enclosing a towing and storage lot that will be covered in recycled asphalt. A grass -covered area will also be included to provide onsite detention. The owner has tentative plans to pave the lot at some point, and the detention area will be sized to accommodate the amount of runoff created by that amount of impervious area. Soil classification for the majority of the Site is Nunn Clay loam (0- 1% slopes). See the Soil Conservation map and description provided in the Appendix. These soils belong to the hydrologic soil group C, as assigned by the Natural Resources Conservation Service. They are deep and well drained, with slow permeability. Runoff is slow, and the hazard of erosion is slight. 2 TABLE OF CONTENTS PAGE I. GENERAL LOCATION AND DESCRIPTION A. SITE LOCATION 2 B. DESCRIPTION OF PROPERTY 2 II. DRAINAGE BASINS AND SUB -BASINS A. MAJOR BASIN DESCRIPTION 3 B. SUB -BASIN DESCRIPTION 3-4 III. DRAINAGE DESIGN CRITERIA A. REGULATIONS 4 B. HYDROLOGICAL CRITERIA 4-5 C. HYDRAULIC CRITERIA 5 IV. DRAINAGE FACILITY DESIGN 5 VI. CONCLUSIONS 5-6 VII. REFERENCES 7 VIII. APPENDICES 8 i F i I CERTIFICATION I hereby certify that this report for the preliminary drainage design of Import Auto Sales, Towing and Storage was prepared by me (or under my direct supervision) for the owners thereof and meets or exceeds the criteria in the City of Fort Collins' Storm Drainage Design Criteria and Construction Standards for the owners thereof. Kevin Forbes Registered Professional Engineer State of Colorado No. 35265 I PRELIMINARY DRAINAGE STUDY FOR IMPORT AUTO SALES,TOWING AND STORAGE September 20, 2007 Prepared for: Randolph Milan 1402 Catalpa Ct. Fort Collins, CO 80521 Prepared by: Mary Mateo, EI Stewart & Associates, Inc. PO Box 429 103 S. Meldrum St. Fort Collins, CO 80521 Phone: (970) 482-9331 Fax: (970)482-9382