12/11/2002 ZONING BOARD OF APPEALS Decisions

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! r I Meetinghouse Hill Page five The calculations do not address the sizing of the infiltration system that is located on Lot 12. Neither do they address the potential for ponding of runoff water in the bottom of the drainage easement on Lot 5. Given the difference in proposed grade between the bottom of the drainage easement and the average grade around the proposed dwelling on Lot 1, (4 to 5 feet) it is strongly recommended that calculations be done to confirm that ponding of storm water runoff will not flood the adjacent lot. It may be necessary to confirm soil conditions in the bottom of the drainage area to verify good drainage within the soil profile. Loamy subsoils will prohibit the natural infiltration of runoff and could result in temporary ponding of water. It may also be necessary to construct an infiltration leaching structure in the bottom of the drainage area to assist in storm water control. The Mashpee Zoning By-Law requires that storm water be controlled for quality as well as quantity. For that reason, vegetated swales are encouraged. If the drainage design can incorporate a vegetated swale around the perimeter as it nears the bottom, it will meet the performance standards of the By-Law and can also be used to control the direction of runoff away from the on-site sewage disposal system on Lot 2. A letter from David C. Thulin, PE, PLS dated February 19, 2003 was received along with the plans and drainage calculations. Mr. Thulin indicates that soil testing has been scheduled but was postponed due to weather. The tests to be conducted are to confirm soil conditions and depths to ground water, both significant issues that affect storm water design and control and on-site sewage disposal design and placement. It is not possible to fully determine the adequacy of the storm water design until the soil data has been collected and analized. The Board may consider two options with respect to this important issue. 1. Accept the design subject to confirmation of soil conditions and with the possibility of changes to the design and/or grades of certain portions of the project for the conditions encountered or, 2. Await the receipt of the test information and review the design in its entirety afterward. Thank you for the opportunity to be of assistance to the Mashpee Board of Appeals. If you have any questions regarding this review please feel free to contact me. Very truly yours, 'I Charles L. Rowley, PE, RLS i , Cc Attorney Jay Talerman, Kopelman and Paige, PC Paul C. Glynn, Esq. David C. Thulin, PE, PLS i'