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HomeMy WebLinkAboutConsultant Review - 41 SECOND STREET 12/6/2012 Eggleston Envirorimental December 6, 2012 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: Stormwater Review—41 Second Street Dear Ms. Tymon and Board Members: Per your request, I have reviewed the November 26, 2012 Site Plan Special Permit Application packet for the above-referenced project. Included in the materials I received and reviewed for the project were the following: • Drainage Study, 41 Second Street, prepared for Gene Espinola by Andover Consultants, Inc. and dated November 20, 2012. • Site Plan, 41 Second Street, prepared for George Espinola by Andover Consultants and dated November 20, 2012. • Landscape Plan, 41 Second Street, prepared for George Espinola by Weinmayr/Jay Associated and dated July 12, 2012. • Special Permit— Site Plan Review Application, 41 Second Street, signed by Gene Espinola • Community&Traffic Impact, 41 Second Street, dated November 7, 2012. The proposed project calls for demolishing an existing house to construct a new 3-unit residential building and 8-space parking lot. The 14,005 sf project site currently has no drainage infrastructure, and runoff from the site flows overland toward the properties to the north and east of the site. As proposed, runoff from the pavement area will be collected in a deep sump catchba s in and discharged onsite to a stone infiltration bed beneath the parking lot. Roof runoff from the front of the new building will also be discharged to the infiltration bed. My comments on the application are outlined below: 1. The Site Plan Review regulations require that runoff from the site be mitigated to zero for the 2, 10 and 100-yr storm events. Based on the drainage calculations submitted, the proposed plan will reduce the peak rate of runoff toward the property to the north, and will result in an overall decrease in the volume of runoff discharged from the site. I do note, however, that the calculations indicate an approximately 10 to 25 percent increase in the peak rate of runoff toward the property to the east of the site (Colby Commons). I also note that the proposed grading on the east side of the proposed building calls for a steep slope aimed directly at the abutting property. I recommend that the grading in this area be revised to retain more of the runoff onsite. 32 Otd Frarningliarn Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 41 Second Street, Technical Review 2 December 6, 2012 2. As proposed, only the roof drainage from the fi•ont of the building will be directed to the infiltration system. It is not clear from the plan whether the back of the building will have gutters and, if so, where they will discharge. 3. Based on the soil data submitted, the proposed infiltration bed has two feet of separation to the estimated high groundwater elevation and is adequately sized to capture and infiltrate the 100-year storm event. The ongoing functionality and longevity of the system will depend on how well the proposed catchbasin functions to prevent sediment from entering the infiltration bed. Provision should be made for regular inspection and cleaning of the catchbasin and periodic sweeping of the parking lot, particularly in areas of snow stockpiling. I appreciate the opportunity to assist the North Andover Planning Board with the review of this project, and hope that this information is suitable for your needs. Please feel free to contact me if you or the applicants have any questions regarding the issues addressed herein. Sincerely, EGGLESTON ENVIRONMENTAL Lisa D. Eggleston,P.E.