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HomeMy WebLinkAbout2010/11/04 - 1st Eggleston Environmental Stormwater Management Review - 1801 Turnpike Street � uuuuuu°uuuu ,. uuuuuupVVVI IIII IVuI.,III IVuI. m rums IlVuum �"'It u uuum�um u Illlllmlllllllll�� I November 4, 2010 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: Stormwater Management Review Sutton Hill Center, 1801 Turnpike St. Dear Ms. Tymon and Board Members: Per your request, I have conducted an initial technical review of the October 14, 2010 Submission for Site Plan Approval for the above-referenced project. Included in the materials I received and reviewed were the following: ■ October 14, 2010 Cover Letter to Judith Tymon, Town Planner from Norman Hill, P.E. of Land Planning, Inc. ■ Drainage Analysis, Sutton Hill Center, prepared for Genesis Health Ventures, Inc. by Land Planning, Inc. and dated October 13, 2010. ■ Site Development Plans (Sheets 1-3 of 3) for Facility Expansion of Sutton Hill Center, prepared for Genesis Health Ventures, Inc. by Land Planning, Inc. and dated October 13, 2010. The proposed project is a 2,800 square foot expansion of the existing health care facility, with associated parking. As proposed, roof runoff from the building addition would drain to a subsurface infiltration system located beneath the new parking area. Runoff from the new parking area would undergo pretreatment in a Stormceptor unit prior to discharge to the subsurface infiltration system. Overflow from the infiltration system would be discharged toward an existing isolated vegetated wetland on the site and then to an offsite bordering vegetated wetland to the north. The proposed project is subject to regulation under the Massachusetts Wetlands Protection Act and the North Andover Wetlands Bylaw, and will therefore need to comply with the Massachusetts Stormwater Standards. It is my understanding that a Notice of Intent has not yet been filed with the Conservation Commission. The focus of my review is on the proposed stormwater management aspects of the project and its compliance with the Site Plan Review requirements (Section 8.3) of the North Andover Zoning Bylaw. My comments are as follows: 1. In accordance with the Site Plan Review requirements, the drainage analysis indicates that the peak runoff rates from the project site would not be increased under 2-, 10- and 100-yr design storm conditions as a result of the proposed expansion. The rate of runoff to the existing isolated vegetated wetland on the site 515 II o11 I o it (m�m h S ,i I I L IIII mu Io I all IIIIIIIIII1I1Q1 u11 �II 01 11 011113 w13 8 616 I6 illlV 8 I 6111 111111 IIIII I I I I IIII II I u� ul u I�IIIIiIpIil��.gyp�V '.� would, however, be increased under post-development conditions; it is storage within the wetland that would attenuate the rate of discharge from the site. It is not clear whether use of the wetland for this purpose would be allowed by the Conservation Commission, since it would likely impact the hydrology of the resource area. Further, since the analysis does not take into account all of the flow to the isolated wetland (it appears that a portion of the property to the west of the project site also drains to the wetland), it may not actually have the available storage assumed in the calculations. 2. Ongoing maintenance of the proposed drainage structures will be needed to ensure that the system continues to perform as designed. An O&M Plan was not included in the materials I reviewed. 3. The Site Plan Review Criteria call for an Erosion & Sediment Control Plan and protection of any steep slopes on the site. Except for a single row of staked haybales, this has not been addressed in the plans submitted. 4. I encourage the Board to also consider whether the existing drainage system on the project site has been adequately maintained, and whether this project provides any opportunity to improve the stormwater management on the site. 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 r uvw m� rl r Lisa D. Eggleston, P.E.