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HomeMy WebLinkAbout250130_1stSWPeerReview_75CoachmansLane - - 75 COACHMANS LANE Horsley Witten GroupSustainable Environmental Solutions 112 Wafer street•80"Floor•Boston,AAA 02109 „ 857-263-8193•horsleywit¢en.com January 30, 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 Swimming Pool — 75 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 swimming pool project at 75 Coachman's Lane in North Andover, MA. The plans were prepared by Williams & Sparages on behalf of Thomas and Amanda Lough (Applicant). The project proposes the installation of a 36 foot by 16 foot in-ground swimming pool, with a paver patio. The stormwater management for the proposed improvements includes a 12-inch-wide, 18-inch-deep infiltration trench along the perimeter of the patio, that is approximately 111 feet long, allowing stormwater from the patio to infiltrate into the ground during a storm event. In addition, the swimming pool will be equipped with a non-backwash filtration system. The proposed pool is a 576 square foot (sf) permanent structure. The footprint of the existing house is approximately 2,622 sf. A total of approximately 1,420 sf of additional impervious surface area, including the pool and paver patio, is proposed within the 45,654-sf parcel. The residential lot is located within the Watershed Protection District and was created in 1965, before October 24, 1994. The project is proposed within the 325-foot Non-Discharge Buffer Zone from the edge of a Bordering Vegetated Wetland (BVW) located to the east of the existing house across Coachman's Lane. The closest point of the proposed patio adjacent to the pool is approximately 230 feet from the BVW to the east. 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. Because the proposed project does not take place within the Non-Disturbance Buffer Zone, the provisions of§195-4.19 C.(2)(f) do not apply. The following documents and plans were received by HW: • Watershed Special Permit Application, 75 Coachman's Lane, North Andover, MA, prepared by Williams & Sparages, dated January 22, 2025 (25 pages); and • Permit Site Plan, 75 Coachman's Lane, North Andover, MA, prepared by Williams & Sparages, dated January 22, 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 Horsley%tMen.com 6 Horslley%tten rou Horsley Witten Group, Inc. Town of North Andover January 30, 2025 Page 2 of 2 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 6-inch mulch sock along the perimeter of the construction access for additional erosion protection. HW notes that the North Andover Conservation Agent has requested that the erosion controls be added to the easterly side of Coachman's Lane to protect the wetland from any transport of dirt or sediment from construction equipment passing back and forth from the site. The Planning Board may choose to include this request as a condition of approval, the suggested location is within the Town's right of way. 2. The Applicant has proposed a construction access around the north side of the house. HW recommends that the Applicant consider construction matting to limit the tracking of sediment offsite or onto the driveway. 3. The Applicant proposes that the swimming pool be equipped with a non-backwash filtration system. HW recommends that the Applicant includes a checklist log that specifies the frequencies of inspecting the filtration system as part of the Operations and Maintenance (O&M) Plan. 4. The Applicant has noted in the O&M Plan that during normal dewatering following storm events, the pool water shall first be dechlorinated and then pumped into the infiltration trench. No further action is requested. 5. HW agrees that the infiltration trench surrounding the patio will provide adequate stormwater management for the additional impervious patio surface, provided that the property owners follow the proper inspection and maintenance protocol as outlined in the O&M Plan. Maintenance of the stormwater management system is the responsibility of the property owners. No further action is requested. 6. HW notes that the Applicant has illustrated the approximate location of the Zone A Federal Emergency Management Agency (FEMA)flood line. FEMA is in the process of updating the flood maps in North Andover. The line as illustrated is consistent with the 2023 zoning map. No further action is requested. 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 jbernardo(a-)horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. Janet Carter Bernardo, P.E. Principal