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Home My WebLink About240221_Rev_SWPeerReview_115WinterStreet - - 115 WINTER STREET Horsley Witten GroupSustainable Environmental Solutions 112 Wafer street•80"Floor•Boston,AAA 02109 „ 857-263-8193•horsleywit¢en.com February 21, 2024 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 — 115 Winter Street 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 letter report summarizing our initial review of the Watershed Special Permit Application and Zoning Variance Application for the proposed swimming pool project at 115 Winter Street in North Andover, MA. The plans were prepared by Williams & Sparages on behalf of Adrianne and Adam Ramos (Applicant). The project proposes the installation of an 18 foot by 38 foot in-ground swimming pool, with a concrete patio, paver walkway and chain link fence. The stormwater management for the proposed improvements includes a 24-inch wide, 2-foot-deep infiltration trench along two sides of the patio to allow 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 684 square foot (sf) permanent structure. The footprint of the existing house is approximately 3,200 sf. A total of approximately 1,600 sf of additional impervious area including the pool, patio and walkway is proposed within the 4.13-acre parcel. The residential lot is located within the Watershed Protection District and was created after October 24, 1994. The project is proposed within a portion of the Non-Discharge Zone from the edge of a wetland resource area located to the south of the existing house. The closest point of the proposed patio adjacent to the pool is approximately 134 feet from the resource area to the south. The proposed limit of disturbance is greater than 100 feet from the wetland resource area. In accordance with §195-4.19 B. (2) 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. A portion of the project area is also located within the 150-foot Non-Disturbance Zone. In accordance with §195-4.19 C. (2)(c) the proposed project also requires the granting of a variance by the Zoning Board of Appeals. The Applicant has applied for the variance from the ZBA. The following documents and plans were received by HW: • Watershed Special Permit Application &Zoning Variance Application, proposed Swimming Pool - 115 Winter Street, North Andover, Massachusetts, prepared by Williams & Sparages, dated January 31, 2024 (15 pages); and • Permit Site Plan, 115 Winter Street, North Andover, Massachusetts, prepared by Williams & Sparages, dated January 24, 2024 (1 sheet). Horsley%tMen.com 6 Horslley%ttenGrou Horsley Witten Group, Inc. Town of North Andover February 21, 2024 Page 2 of 2 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 regarding the proposed stormwater management design. 1. The Applicant is subject to the requirements of§195-4.19 B., "Non-Discharge Buffer Zone." §195-4.19 B refers to §195-4.19 C (3)for Prohibited Uses except as allowed by§195-4.19 C (2)which includes (f) "construction of any accessory structure or expansion of any existing structure by less than 25% of the gross floor area if the existing structure exceeds 2,500 square feet." The existing house at 3,300 sf has a footprint that exceeds 2,500 sf, and the proposed accessory structure (swimming pool at 684 sf) is less than 25% of the gross floor area. No further action required. 2. The Applicant has included erosion controls on the Plan and has shown where the stockpiles will be located during construction. HW recommends that the Applicant include an additional mulch sock or silt fence surrounding the stockpiling area for erosion protection. 3. The Applicant has proposed a construction access around the west and south side of the house. HW recommends that the Applicant include construction matting to limit the tracking of sediment offsite or onto the driveway. 4. The Applicant proposes that the swimming pool be equipped with a non-backwash filtration system. HW recommends that the Applicant include a checklist log that includes inspecting the filtration system as part of the Operations and Maintenance Plan. 5. The Applicant has noted in the O&M Plan that when during normal dewatering following storm events, the pool water shall be pumped into the infiltration trench. HW notes that the pool water should be dechlorinated prior to being pumped to the infiltration system. 6. HW agrees that the infiltration trench surrounding the patio will provide adequate stormwater management for the additional impervious surface. No action required. Conclusions HW recommends that the North Andover Planning Board require the Applicant to address these recommendations 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 jbernardoCa)horsleywitten.com if you have any questions regarding these comments. Sincerely, HORSLEY WITTEN GROUP, INC. Janet Carter Bernardo, P.E. Associate Principal �'I8 1 c,an or Nk)d,h 10 MA,,'Y g5 Win9kn ^,ta, a,��,i.'��1;��,aroi °�Yk�'�q , 11lP�+ ,��r�',, a� ^�...I,I,VVire9nrS"a c d.d,"rcx