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NORFOLK <br /> RAM GROUP <br /> ENGINEERING : ENVIRONMENT <br /> May 12, 2004 <br /> Mr. Bruce Garrett <br /> Vice President <br /> Volta Oil Company <br /> One Roberts Road <br /> Plymouth, Massachusetts 02360 <br /> Re: Mashpee Zoning Board of Appeals <br /> 414 Nathan S. Highway <br /> Response to Review Comments <br /> Norfolk Proiect No. 101.44.2 <br /> Dear Bruce: <br /> Norfolk Ram Group LLC (Norfolk) has reviewed Charles L. Rowley & Associates <br /> (Rowley) letter dated May 12, 2004 to the Mashpee Zoning Board of Appeals. <br /> Based on a review of the letter Norfolk offers the following comments and <br /> responses: <br /> Prior to our addressing each comment, Rowley is accurate that the rainfall <br /> distribution should be Type III. Norfolk has revised our calculations accordingly. <br /> The result is the peak flows for each storm flow have been reduced. This <br /> revision has impact on the remaining responses. <br /> Drainage Calculations <br /> 1. Recently, Norfolk completed three test pits on a different part of the site as <br /> part of the onsite sewage disposal system design. The percolation tests <br /> indicate that the receiving soil is sand has a percolation rate of 2 minutes <br /> per inch. However, a layer of silt clay was found at approximately four feet <br /> below grade and ranged in thickness from approximately 2.5-feet to 4-feet. <br /> In the event that this material is encountered in the area of the infiltration <br /> chambers it will be excavated and replaced with Title 5 sand. <br /> 2. Norfolk has taken a second look at the groundwater depths at the site <br /> from the two monitoring wells closest to the infiltration field. Depth to <br /> groundwater readings were obtained over a five year period from 1995 <br /> through 1999. A total of sixteen readings were obtained, with three of the <br /> readings resulting in a separation of 1.5, 1.8, and 2.8 feet. Because the <br /> 100-year flow has been reduced by using the correct Rainfall Distribution, <br /> the infiltration field will be modified. The modification includes a 2-foot <br /> deep concrete infiltration chamber (current design calls for 4-feet) and <br /> ONE Romsst:rs Rote• PLY-MOUTI-1,MAssACHUSETTs 02360. (508)747-7900 P1IONE. (508)747-3658 FAX <br /> 100 KUN1110120. HOLLISTON, MAssACHUSFI-rs 01746. (508)822-5500 i,LtoNF 0 (508)822-1611 FAX <br /> W VW.NOI:EOLKRAN4.COM <br />