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HomeMy WebLinkAbout2012-04-03 Planning Board Supplemental Materials (51) Eggleston Environmental 32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 March 26, 2012 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: Stormwater Review – 498 Chickering Road Dear Ms. Tymon and Board Members: Per your request, I have reviewed the February 27, 2012 Special Permit Application for packet for the above-referenced project. Included in the materials I received and reviewed were the following: · Application for Site Approval, Lowell Five, 498 Chickering Road, prepared by Merrimack Engineering Services, Inc. and dated February 27, 2012. · Project Drainage Report, Proposed Bank Facility, 498 Chickering Road, prepared by Merrimack Engineering Services, Inc. and dated February 16, 2012. · Site Plan (5 Sheets), Proposed Bank Facility, 498 Chickering Road, prepared by Merrimack Engineering Services, Inc. and dated January 20, 2012. The proposed project is a bank facility to be constructed on the site of a former Mobil gas station. The project site currently has no drainage infrastructure, and runoff from the site flows overland to the northeast, toward Franklin Street. As proposed, the project will result in a net decrease in impervious cover on the site and will include a drainage collection system with deep sump catchbasins to collect runoff. The closed drainage system would discharge to a grassed swale extending into and terminating within the Franklin Street right-of-way. My comments on the application are outlined below: 1. In accordance with the Site Plan Review requirements, the proposed plan will not increase either the rate or volume of runoff from the site. It will concentrate the discharge at a single point within the Franklin Street ROW; however it appears to be at a suitable location given that it is immediately adjacent to an existing outlet from the Town drain in Chickering Road. (I presume, therefore, that that portion of Franklin Street will remain a paper street.) 2. The addition of deep sump catchbasins and the outlet swale will also provide some degree of water quality treatment of the flow discharged from the project site. Provision should be made for periodic maintenance of these facilities on an ongoing basis. 498 Chickering Road, Technical Review 2 March 26, 2012 3. The project site is subject to a Sensitive Use Restriction on the Deed, presumably due to subsurface contamination from the former gas station. Among other things, the restriction calls for engineering controls to prevent the migration of vapors and/or liquids containing Hazardous Materials into any underground utilities or stormwater ponds, including vapor installation systems, vapor barriers, sealed sumps and the like. It also calls for specific measures to be taken in any common areas, including gardens, yards and open space areas. No such control measures are identified on the Site Plan for the proposed project, e.g. with respect to the drainage infrastructure and the proposed landscaping, and there is no reference on the plan to the Sensitive Use Restriction. 4. Erosion and sediment control measures employed on the site during construction should also take into account the possible contamination of exposed soils. 5. There are no gutters or roof drains shown on the project plans, therefore it appears that roof runoff will sheet off the building directly to the ground below. To the maximum extent possible the roof runoff should be directed toward pervious ground surfaces where it can infiltrate, rather than running across the parking lot to the closed drainage system. 6. The proposed project calls for sprinklers and drip irrigation to maintain landscaped areas of the site. Consideration should be given to using a cistern to capture roof runoff for reuse on the site. 7. I note that the architectural plan calls for copper roof elements on the proposed building. The Planning Board should be aware that recent studies have shown that when exposed to acid rain, the runoff from copper roofs can carry levels of ionic copper that are potentially toxic to aquatic life. Filtration of the runoff through natural soils or through iron filings will generally convert the ionic copper to a less toxic form. 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.