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HomeMy WebLinkAbout250403_HW_1stSWReview - - 135 COACHMANS LANE Horsley Witten GroupSustainable Environmental Solutions 112 Water Street-611 Floor»Boston„MA 02109 857-263-8193•horsleywitten.corn fJ1JD19JI�%�%' April 3, 2025 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Re: Initial Stormwater Peer Review Proposed Improvements— 135 Coachman's Lane North Andover, Massachusetts Dear Ms. Enright and Board Members: The Horsley Witten Group, Inc. (HW) is pleased to provide the North Andover Planning Board with this report summarizing our initial review of the Watershed Special Permit Application for the proposed improvements at 135 Coachman's Lane in North Andover, MA. The plans were prepared by Williams & Sparages on behalf of William &Ann Belanger(Applicant). The project proposes a 225.5 square foot (sf) expansion of the dwelling and a 337.7 sf expansion of the garage, as well as a 310 sf expansion of the paved driveway, and the relocation of a brick walkway and stairs from within the 325 foot"Non-Discharge Buffer Zone"to Bordering Vegetated Wetlands (BVW). The stormwater management for the proposed improvements includes a 24-inch wide by 24-inch-deep crushed stone infiltration trench along the southern edge of the driveway and a 24-inch wide by 24-inch-deep crushed stone infiltration trench along the first-floor expansion. The existing footprint of the house is 2,489 sf. The proposed footprint of the expanded house is 2,714.5 sf. A total of approximately 873.2± square feet (sf) of additional impervious surface area is proposed within the 44,358-sf parcel. It appears that the total land disturbance will be less than 43,560 sf. The residential lot is located within the Watershed Protection District and was created in 1965, before October 24, 1994. The lot is located within the urbanized area and the area of disturbance is less than 1 acre. The project is proposed within the 325-foot Non-Discharge Buffer Zone from the edge of two BVWs. One BVW is located along the northerly side of Coachman's Lane on 134 Coachman's Lane. The other BVW lies to the south along the 12 Carriage Chase property. The closest point of the proposed garage expansion to the BVW is approximately 147.8 feet. The closest point of any construction activity is the addition of the stone infiltration trench along the existing driveway approximately 122.4 feet from the southern BVW. The proposed limit of disturbance is greater than 100 feet from the wetland resource area. In accordance with §195-4.19 B.(2)(a) of the North Andover Zoning Bylaws, any surface or subsurface discharge of stormwater within the Non- Discharge Buffer Zone is only allowed after a special permit has been granted by the North Andover Planning Board. The following documents and plans were received by HW: • Watershed Special Permit Application, 135 Coachman's Lane, North Andover, MA, prepared by Williams & Sparages, dated March 12, 2025 (13 pages); and I-Inr leyWitlen.cor (i�)H o rspeyWitfe GrouP IM H o rs&ey Wiffen GMUP, IIC. Town of North Andover April 3, 2025 Page 2 of 3 • Permit Site Plan, 135 Coachman's Lane, North Andover, MA, prepared by Williams & Sparages, dated March 9, 2025 (1 sheet). Stormwater Management Design Peer Review In accordance with §195-4.19.B.(4)All construction in the Watershed Protection District shall comply with best management practices for erosion, siltation, and stormwater control in order to preserve the purity of the groundwater and the lake; to maintain the groundwater table; and to maintain the filtration and purification functions of the land. HW has the following comments and recommendations regarding the proposed stormwater management design. 1. The Applicant has included erosion controls on the Plan and has shown where the stockpiles will be located during construction. The Applicant has also included a 12-inch mulch sock along the southern limit of construction. HW recommends that the erosion controls be added along the tree line parallel to the eastern property line to protect the wetland from sediment transported by construction equipment onto the existing driveway. HW further recommends that erosion controls be extended along the tree line to the north of the house to protect the area from sediment transported by construction equipment using the proposed construction access. 2. The Applicant has proposed a construction access around the west side of the house. HW recommends that the Applicant consider construction matting or other measures to minimize the tracking of sediment onto the driveway and offsite per§250-25.E.(13) of the North Andover Code. 3. HW recommends that the Applicant provides a path and mechanism to divert uncontaminated water around the disturbed areas per§250.25.E(10)and §250-26.A.(27) of the North Andover Code. 4. HW recommends that the Applicant provides measures to maintain infiltration capacity of existing soils where infiltration is proposed per§250-25.E.(12) of the North Andover Code. 5. The Applicant has provided crushed stone trenches to manage the additional impervious cover from the proposed project. It is not clear how these trenches were sized and whether the existing property has any stormwater management practices that are currently managing the roof or driveway runoff. It appears that stormwater that falls on the existing driveway flows south and will be intercepted by the proposed infiltration trench. It would be beneficial to confirm that this trench can manage all the stormwater flowing into it. Similarly, if some portion of the southern half of the roof runoff, as suggested in the narrative, will be directed into the proposed infiltration trench placed along the dwelling expansion, HW recommends that the Applicant confirm that the stone trench is adequately sized to manage this runoff. 6. HW recommends that the Applicant include an inspection and maintenance log as part of the O&M plan for use by the homeowner. Town of North Andover April 3, 2025 Page 3 of 3 7. HW concurs with the Applicant that the increase in impervious cover is minimal and that if the stone trenches are adequately sized, the type of mitigation proposed should be appropriate for the proposed project. Conclusions HW recommends that the North Andover Planning Board discuss the above comments with the Applicant as part of its review process. We appreciate the opportunity to assist the Town of North Andover with this project review. Please contact Janet Bernardo at 508-833-6600 or at ibernardoCaD-horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. Janet Carter Bernardo, P.E. Principal