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HomeMy WebLinkAbout2012-11-20 Planning Board Supplemental Materials (41) Eggleston Environmental 32 Old Framingham Rd Unit 29 Sudbury MA 01776 tel 508.259.1137 fax 866.820.7840 November 6, 2012 North Andover Planning Board 1600 Osgood Street North Andover, MA 01845 Attn: Judy Tymon, Town Planner RE: 1018 Osgood Street Watershed Protection District Applicability Dear Ms. Tymon and Board Members: I am in receipt of the October 19, 2012 Special Permit Application Packet for the proposed Dunkin Donuts project at 1018 Osgood Street and, per your request, have reviewed the request for determination of Watershed Protection District applicability included with the application packet. According to the Town’s zoning map, the Lake Cochichewick drainage basin boundary is located just offsite to the north of the subject property; hence the entire parcel is included in the Watershed Protection District. The request letter from Mark Gross, P.E. of MHF Design Consultants, Inc. states that the proposed project should not be subject to the requirements of the Watershed Protection Zone on the basis that the on-site wetlands are not tributary to Lake Cochichewick and the drainage from the site will not be conveyed to the lake. My comments on this request are outlined below: 1. Based on surface topography, the southwest portion of the lot (Area 1S on the pre-development drainage plan) drains in a southerly direction (toward Osgood Street and the lake), while the remainder of the lot drains toward the small bordering vegetated wetland (BVW) in the northeast corner of the lot. 2. The September 15, 2012 memorandum from Epsilon Associates submitted in support of the request specifically addresses the drainage from the onsite BVW, not the site as a whole. It is also lacking in the detail necessary to substantiate the findings, specifically maps or figures showing the offsite wetlands and the drainage structures referenced in the memo. I would also point out that the fact that the rim elevation of a catchbasin in Osgood Street is higher than the pipe on the north side of the street does not necessarily indicate the direction of flow; the inverts of the pipe at both locations will determine the slope. 3. If it can be adequately documented that the onsite wetland drains away from the lake (and it appears that it does), I would concur that the portion of the lot that drains to the wetland (Area 2S) should be excluded from the Watershed Protection District since it would be outside of the Lake Cochichewick watershed. The southwestern portion of the lot, however, is a different matter, as it is topographically still within the Lake Cochichewick watershed. Surface runoff from the lot will likely be diverted into the drainage system in Osgood Street in most storm events; it remains unclear where that drainage goes and whether any 1018 Osgood Street, WPD Applicability 2 November 6, 2012 of it is discharged towards the lake. However, runoff from storm events that exceed the capacity of the drainage system will still drain toward the lake and, more importantly, the groundwater beneath that portion of the property likely also flows toward the lake, since the topography of the land surface usually also determines the general direction of groundwater flow. As stated in Section 4.136 of the Watershed Protection District regulations, they are specifically “intended to preserve the purity of the ground water, the lake and its tributaries; to maintain the ground water table, and to maintain filtration and purification functions of the land”. Hence, the protections afforded by the Watershed Protection District regulations should not be waived within the watershed, regardless of whether a portion of the surface runoff is diverted elsewhere. Based on setbacks from a tributary wetland on the south side of Osgood Street, it is my opinion that a portion of the property at 1018 Osgood Street is within the Non-Discharge Zone of the Watershed Protection District. 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.