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Home My WebLink About251104_HW_1st_SWPeerReview_243 Great Pond Road - - 243 GREAT POND ROAD Horsley Witten GroupSustainable Environmental Solutions 112 Wafer Street•80"Floor•Boston,AAA 02109 „ 857-263-8193•horsleywit¢en.com November 4, 2025 Ms. Jean Enright, Planning Director Planning Department Town of North Andover 120 Main Street North Andover, Massachusetts 01845 Re: Initial Stormwater Peer Review 243 Great Pond Road 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 243 Great Pond Road in North Andover, MA. The plans were prepared by Patriot Engineering LLC on behalf of Stephen Boyko (Applicant). The project proposes the removal of an existing sports court area to accommodate a proposed 24-foot x 36-foot greenhouse structure. The stormwater management for the proposed improvements includes a 2-foot wide by 2- feet deep stone trench drip edge to capture and infiltrate the roof runoff from the proposed greenhouse. The Applicant has noted on Sheet C-3 that the existing impervious area of the site is 9,473± square feet (sf). The total impervious area to be removed is 1,801± square feet, and the total proposed impervious area to be constructed is 1,243± square feet. A total reduction of 558± square feet of impervious surface area is proposed within the 2.47-acre parcel. It appears that the total land disturbance is approximately 26,000 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. Most of the project area is within the 200-foot Riverfront Area of an unnamed perennial stream. The limit of work is within the 50-foot No Build Zone from the edge of a bordering vegetated wetland (BVW) to the west of the parcel. A second BVW, including a potential ephemeral pool, is located on the northern side of the parcel. The closest point of the proposed greenhouse to the western BVW is approximately 100 feet. The closest point of any construction activity is the proposed Construction Fence along the proposed limit of work, which is approximately 25 feet from the western BVW. The proposed limit of disturbance is greater than 25 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 proposed project is within the jurisdiction of the North Andover Conservation Commission. The following documents and plans were received by HW: • Watershed Special Permit Application, 243 Great Pond Road, North Andover, MA, prepared by Patriot Engineering LLC (3 pages); Horsiey%tMen.com 6 Horslley%ttenGrou Horsley Witten Group, Inc. Town of North Andover November 4, 2025 Page 2 of 3 • Stormwater Analysis and Calculations, 243 Great Pond Road, North Andover, MA, prepared by Patriot Engineering LLC, dated October 29, 2025 (39 pages). and • Greenhouse Site Plan, 243 Great Pond Road, North Andover, MA, prepared by Patriot Engineering, dated October 29, 2025: o Cover Sheet Sheet C-1 o Construction Management Plan Sheet C-2 o Conservation Site Plan Sheet C-3 o Construction Management Plan (details) Sheet C-4 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 including proposed construction fencing and a 12-inch filtermitt on the Construction Management Plan and has shown where the stockpiles will be located during construction. 2. The Applicant has proposed a temporary construction entrance around the south 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. It appears that the earthwork proposed will be contained to the area of the existing basketball court and the construction of the proposed greenhouse. HW recommends that the Applicant confirm that the area surrounded by the proposed post& rail fence will not be altered. 4. The Stormwater Analysis and Calculations report does not include an existing drainage area figure. The Applicant has provided an existing conditions catchment area 2S with a total area of 24,908 sf. The paved area includes 4,340 sf. HW could not confirm the limits of the catchment area and could not determine if any of the existing house was included as part of the paved parking area. HW recommends that the Applicant provides an existing catchment area figure to confirm the values listed in the HydroCAD model for catchment area 2S. 5. The Applicant has not included a proposed catchment area figure. It has listed proposed catchment area 5S as having 24,908 sf. The paved parking area includes 3,691 sf. The Applicant has also included proposed catchment area 3S with a proposed DRIVE area of 890 sf. HW assumes that catchment area 3S is associated with the proposed greenhouse and agrees that the area modeled is reasonable. However, HW believes that the catchment area modeled as 3S should be subtracted from the catchment area modeled as 5S. HW recommends that the Applicant provides a proposed catchment area figure to confirm the values listed in the HydroCAD model for catchment area 3S and 5S. Town of North Andover November 4, 2025 Page 3 of 3 6. HW recommends that the Applicant clarify the total impervious area to be removed and the total proposed impervious area to be constructed. We could not confirm the values provided on Sheet C-3. 7. The Applicant has modeled the existing and proposed soil conditions as hydrologic soil group (HSG)A. In accordance with the Natural Resources Conservation Service (NRCS)the soils are HSG B or B/D. HW recommends that the Applicant revise the HydroCAD model accordingly. 8. The Applicant has included an exfiltration rate of 1.02 inches per hour(iph) in the HydroCAD model for the Stone Trench. HW recommends that the Applicant provide soil testing or other documentation to confirm the exfiltration rate used. 9. The HydroCAD model for the Stone Trench includes a 20 foot long by 1.0-foot-wide broad crested weir at elevation 155.95. HW recommends that the Applicant clarify where this is proposed on the site plans. HW notes that the plans include a proposed 156 contour grade line around the Greenhouse, HW further notes that during a 100-year storm event the stone trench will overtop the proposed weir. 10. HW recommends that the Applicant clarify if any existing trees will be removed as part of the proposed project. 11. HW notes that the Erosion and Sedimentation Control Measures narrative lists the Town of Lexington. HW recommends that the Applicant revise this to read North Andover. 12. HW notes that the Applicant mentions a subsurface infiltration system in the narrative numerous times. It is HW's understanding that the proposed stormwater practice is a drip edge stone trench to manage the roof runoff from the proposed greenhouse. HW recommends that the Applicant modify the narrative to avoid confusion or provide the design information for the subsurface system. Conclusions HW recommends that the North Andover Planning Board requires that the Applicant provides a written response to the above comments. 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. "�".�'w^^m.�.."'ti��,,. a„„r»„�� ,.� m��.wR.,.n..++�"'4V'p✓'._r�a'a::a / rv�!° l""r../tt Cvh.., Janet Carter Bernardo, P.E. Chelsea Yuan Principal Staff Engineer