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• MEAD & HUNT Engineers - Architects Scientists - Planners December 13, 1994 Rodney J. Ripley Rayovac Corporation 601 Rayovac Drive Madison, WI 53744-4960 Dear Mr. Ripley: We have completed our engineering analysis of the size and type of culvert needed under your driveway at your proposed residence along Tonto Trail in the Town of Verona. Our analysis shows that you need a 60-inch corrugated metal pipe, with approximately 2.5 feet of cover (from the top of the pipe to the bottom of the road), to convey the 2-year flow of 200 cubic feet per second (cfs). The purpose of this letter is to document the assumptions, methodology, and results of this culvert sizing study. Assumptions The following assumptions were made for this study: • Two-Year Design Frequency. According to the attached table published by the Denver Regional Council of Governments, Urban Storm Drainage Criteria Manual, a residential driveway culvert should have a 2-year design storm frequency (i.e; the culvert must have capacity to convey peak runoff from the 2-year storm.) This design criteria means that over the long term, the culvert capacity may be expected to be exceeded on the average of once every two years. • Future Fully Developed Land Condition Used. The hydrologic analysis (described below) utilized the future fully developed land use in the upstream tributary drainage area. In a telephone conversation with Paul Woodard of the City of Fitchburg, the proposed land use for this area is predominantly 1/4-acre residential. Methodology The hydrologic method used to generate the 2-year peak runoff rate was the Soil Conservation Service (SCS) Technical Release 55 (TR-55) Urban Rainfall Runoff Model. This method is a recognized standard for urban hydrology used by many municipalities, including the City of Madison. MEAD Si.HUNT,inc. 6501 Watts Road,Suite 101 Madison,Wisconsin 53719-2700 Telephone(608) 273-6380 Facsimile(608) 273-6391 Founded in 1900 R129A001/R129-94A ll