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Home My WebLink About2025/07/07 - 1st Stormwater Peer Review - - 364 JOHNSON STREET %�. Horsley Wiften Group 0 SUStainable, Ehvirownental Solutions 112 W'at r `tr t-61 Floor-Boston,MBA 02109 .......... 5 -2 1 ho,r 1 ten July 7, 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—364 Johnson 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 report summarizing our initial review of the Watershed Special Permit Application for the proposed improvements at 364 Johnson Street in North Andover, MA. The plans were prepared by John J. McDonnell, MSCE, PE, PLS on behalf of Gergory and Melissa Buitkus (Applicant). The project proposes a 376 square foot (sf) expansion of the existing two-story dwelling within the 325- foot"Non-Discharge Buffer Zone" to Bordering Vegetated Wetlands (BVW). The stormwater management for the proposed improvements includes a 160-gallon mini drywell and a subsurface system for infiltration on the east side of the existing building. The existing footprint of the house is 890 sf. The proposed footprint of the expanded house is 1,266 sf. A total increase of approximately 376± sf of impervious surface area is proposed within the 26,571-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 1964, 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 a BVW. The BVW is located along the western side of the roadway at 365 Johnson Street. The closest point of the proposed expansion to the BVW is approximately 260 feet. 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, 364 Johnson Street, North Andover, MA, prepared by John J. McDonnell, MSCE, PE, PLS, dated May 20, 2025 (12 pages); • Plot Plan of Land, 364 Johnson Street, North Andover, MA, prepared by John J. McDonnell, MSCE, PE, PLS, dated June 13, 2025 (1 sheet); and • Stormwater Management Report, 364 Johnson Street, North Andover, MA, prepared by John J. McDonnell, MSCE, PE, PLS, dated June 25, 2025 (15 sheets). Town of North Andover July 7, 2025 Page 2of3 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 provided a Plot Plan of Land. HW recommends adding a north arrow to the plan and providing a legible signed and stamped copy of the plan to the Planning Board. 2. The Applicant has called out erosion controls and notes on the Plan. A callout for a silt sock is noted but it is unclear where it is located. It is also unclear where stockpiling onsite will occur and the limits of the disturbance for work. HW recommends showing the limits of disturbance and locations of silt sock in addition to where the stockpiles will be located during 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. 3. HW recommends that the Applicant callout a defined construction access point to the work onsite. HW recommends that the Applicant consider construction matting or other measures to minimize the tracking of sediment offsite per§250-25.E.(l 3) of the North Andover Code. 4. HW recommends that the Applicant provides a path and mechanism to divert uncontaminated water around the disturbed areas per§250.25.E.(l 0) and §250-26.A.(27)of the North Andover Code. 5. HW recommends that the Applicant includes measures to maintain the infiltration capacity of the existing soils where infiltration is proposed per§250-25.E.(l 2) of the North Andover Code. The USDA soil maps list the soil type for this site as hydrologic soil groups `C' and `D' which are poor for infiltration. HW also recommends that the Applicant provide the field permeability tests to confirm the 24 inches/hour infiltration rate documented. 6. The Applicant has provided some results of the HydroCAD report and analysis for the proposed system. HW recommends that the Applicant provide the entire HydroCAD output for the 100-year event and include the stage storage tables for the infiltration system that will be used in the drawdown calculations. 7. The Applicant has provided a drywell to provide pretreatment prior to the infiltration system. A drywell also infiltrates water. It is not clear how the drywell serves as a `pre-treatment' to the infiltration rather than additional storage. Furthermore, it appears that any Total Suspended Solids (TSS) being treated in the drywell system would clog the system over time. HW recommends that the Applicant provide a sump for solids to settle within the Town of North Andover July 7, 2025 Page 3of3 drywell or providing a deep sump catch basin instead of a drywell as part of the proposed project. 8. HW notes that the Applicant has described the proposed 376 sf addition in the Watershed Permit Application. HW notes that roof runoff that is being directed to the subsurface chamber system is considered clean and does not need pretreatment. 9. HW further notes that the Applicant has included 900 sf of future paved area in the Stormwater Management Report. However, this area is not shown on the plans or in the Permit Application. The driveway runoff should include pretreatment prior to infiltrating. 10. HW recommends that the Applicant includes the bottom of stone, bottom of chamber, top of chamber, top of stone and proposed surface elevation on the Cultec Recharger Detail provided. 11. HW recommends that the Applicant illustrate the drainage connection from the roof downspouts and from the proposed driveway surface. As shown, it is not obvious how stormwater will get into the drywell or into the Cultec chambers. 12. HW recommends that the Applicant include any proposed grading on the site plan. It appears that the Cultec recharge system proposed will require a change in surface grades. 13. The Applicant has provided an Operation and Maintenance (O&M) Plan as part of the drainage report. HW recommends that the Applicant includes an inspection and maintenance log and a simple sketch that clearly labels the stormwater practices as part of the O&M Plan for use by the homeowner. Conclusions HW recommends that the North Andover Planning Board require the Applicant to address the above comments as part of its permit 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