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Volta Oil Co. <br /> 414 Nathan S. Ellis Highway, Mashpee <br /> page two <br /> Other drainage issues <br /> 1. It is not clear from the tables provided at the back of the drainage report how the <br /> infiltration rate was calculated. The rate of outflow is quite high in comparison to <br /> the surface area provided. A sample infiltration calculation would be helpful <br /> 2. The drainage calculations were done using Type II rainfall criteria. A Type III <br /> rainfall criteria should be used for the Cape Cod area. (Ref. SCS Rainfall <br /> Distribution Map from TR-55) <br /> Plans <br /> The plan content is consistent with the information that is expected for site plan <br /> review. Existing conditions and proposed conditions are all shown. There is a separate <br /> landscaping plan and a plan for site details. The detail sheet should be corrected for the <br /> following: <br /> 1. Deep sumps for catch basins should be 4' instead of 2'-6" in order to comply for <br /> sediment control and storm water management requirements. <br /> 2. The detail for concrete curb suggests that it may not be properly anchored with <br /> cement concrete depending on when it is set. It is recommended that the curb <br /> should be set after the base course of pavement is in place so that cement <br /> concrete will be used to anchor the curb. <br /> 3. The "Barnstable" type elbow used in the catch basins should be a minimum of <br /> 12" long below the flow line of the pipe. <br /> 4. It is recommended that cement concrete collars be placed around all manhole <br /> and catch basin frames after pavement binder is in place. The top course of <br /> paving would be placed over the cement concrete collar and would seal the joint. <br /> Operation and Maintenance Plan <br /> The plan suggests the inspections that would be done on a regular basis to <br /> insure that the drainage system is functioning as designed. However on page one of <br /> the project description reference is made to Catch Basin 1 being equipped with a metal <br /> cover to be used when gas tanks are filled. How is this to be monitored so that it will be <br /> done routinely and how will the basin be made watertight for the cover to be effective? <br /> I have done an overview of the project and have not looked at each and every <br /> detail. I am assuming that the project would be subject to site plan review and that your <br /> purposes are more with respect to special permit/variance issues. If a complete review <br /> is required please feel free to contact me. <br /> Very truly yours, <br /> J <br /> Charles L. Rowley, PE, RLS <br /> Cc Michael Clark, PE, Norfolk Ram Group <br /> r <br />