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Home My WebLink About250408 Resp to 1st SWReview - - 135 COACHMANS LANE Apri18,2025 North Andover Planning Board Attn: Jean Enright,Planning Director WILLIAMS North Andover Planning Department W-41111 77-� � ��-++ ,L-1GE 120 Main Street SPAJtSS North Andover, MA 01845 ENGINEERS ' SCIENTi5T5 ' SURVEYORS Re: 135 Coachman's Lane Peer Review Response Watershed Special Permit Application Dear Jean, As you are aware, our office submitted a Watershed Special Permit on behalf of the property owners, William&Ann Belanger, to expand their existing garage and expand a portion of the first floor of the existing dwelling. We are in receipt of the peer review comments provided by Horsley Witten Group, Inc. dated April, 2025. The following is a list of their comments and our responses: 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. The plan has been revised to show the mulch sock extending further up the eastern edge of the driveway to aid in preventing any sediment transported by construction equipment across the existing driveway. The mulch sock has been extended up past the footprint of the garage and where disturbance is likely to occur. The area to the north of the house slopes up before sloping back down towards Coachman's Lane,which our topographic mapping did not entirely capture.A few spot elevations are shown in this area, which show a rise in the existing grade.No runoff would reach Coachman's Lane in this area of the project,so we do not believe it is necessary to extend the erosion controls further north along the existing tree line in this area. 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. Williams&Sparages I Engineers•Scientists•Surveyors 189 North Main Street I Suite 101 1 Middleton, MA (978)539-8088 1 www.wsengineers.com Page 11 YV- c T S The plan has been revised to show construction matting within the portion of the construction entrance along the existing driveway. Earthwork and access with heavy machinery along this construction access would likely only occur over the course of a day or two and involve excavation of the foundation and backfilling once the foundation is set. This area of lawn also gently slopes towards the lawn areas away from the driveway. 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. Runoff from the front of the property and driveway would continue to flow down the driveway towards the rear of the property during construction. We therefore agree that keeping the driveway clean during construction is the most important aspect of the project to reduce any potential impacts on the downgradient wetland resource areas. Project note#3 has been added to ensure the driveway is swept at the end of each workday and prior to any rain events. The applicant has also agreed to utilize a rubber track machine for any earth work, and will also pump the concrete for both of the foundations from the existing driveway further reducing any disturbance of lawn areas.We believe that a staked 12"mulch sock is adequate in containing sediment from construction activities associated with the garage and driveway expansion and small dwelling expansion. Excavation and earthwork is a diminutive amount of overall disturbance(875 s.f.). The existing foundation of the garage is set to remain,further reducing the amount of overall disturbance. The applicant would be amenable to placing haybales along the upslope side of the garage to direct water towards the easternmost potion of the driveway away from construction activities,however the surface flow towards the garage does not appear to be of significant concern in our opinion. The applicant would also be amenable to a condition of approval that if runoff becomes an issue during construction, a mechanism to divert water around any disturbed areas would be provided. This project will be monitored weekly by a qualified professional as well. 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. See Project note#2 regarding measures to maintain infiltration capacity of existing soils where infiltration is proposed. 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, Williams&Sparages I Engineers•Scientists•Surveyors 189 North Main Street I Suite 101 1 Middleton, MA (978)539-8088 1 www.wsengineers.com Page 12 YV- c T S 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. Storwmater calculations are provided on the revised plan.Both infiltration trenches were conservatively sized knowing that the proposed infiltration trench along the existing driveway would also capture runoff from the existing driveway. The proposed infiltration trench along the dwelling expansion is sized to recharge both the existing and proposed roof 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. The Operations and Maintenance Plan has been revised to include an inspection and maintenance log (see attached). 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. No comment. If you should have any questions regarding this information, or require any additional information,please do not hesitate to contact our office. �, 1inoeYPIV Thorsen Akerley,P.W.S.,R.S. Project Manager,Williams& Sparages LLC cc: William&Ann Belanger, 135 Coachman's Lane,North Andover, MA Janet Carter Bernardo,P.E.,Horsley Witten Group,Inc. Enclosures Williams&Sparages I Engineers•Scientists•Surveyors 189 North Main Street I Suite 101 1 Middleton, MA (978)539-8088 1 www.wsengineers.com Page 13 YV- c T S March 12, 2025 Revised April 7, 2025 135 Coachman's Lane I North Andover, MA Operations&Maintenance Plan Operations &Maintenance Plan:135 Coachman's Lane,North Andover,MA System Owner: William&Ann Belanger 135 Coachman's Lane North Andover MA 01845 Stone Infiltration Trench This Operations &Maintenance Plan has been prepared to comply with the provisions set forth in the Massachusetts Department of Environmental Protection (DEP)Stormwater Management Standards. Structural Best Management Practices (BMPs)require periodic maintenance to ensure proper function and efficiency in pollutant removal from Stormwater discharges that would otherwise reach wetland resource areas untreated. Maintenance schedules found below are recommended in Department of Environmental Protection's Massachusetts Stormwater Handbook and as recommended in the manufacturer's specifications. The stormwater management system owner and the party responsible for maintenance of the stormwater management system shall be the property owner and their designated employees. • Inspect and clean every six months and after every major storm event of 0.5 inches in a 24- hour period (See inspection and maintenance log below). • Remove accumulated sediment,trash,debris,leaves and grass clippings. • Remove tree seedlings before they become firmly established. • Inspect the trench 24 hours or several days after a rain event to look for ponded water. If there is ponded water at the surface of the trench,it is likely that the trench surface is clogged. • To address surface clogging,remove and replace the first layer of stone aggregate and filter fabric. If the water is ponded inside the trench,it may indicate that the bottom of the trench has failed. • To rehabilitate a failed trench, all accumulated sediment must be stripped from the bottom, the bottom of the trench must be scarified and tilled to induce infiltration,and all of the stone aggregate and filter fabric or media must be removed and replaced. Williams&Sparages I Engineers•Scientists•Surveyors 189 North Main Street I Suite 101 1 Middleton, MA (978)539-8088 1 www.wsengineers.com Page 11 YV- c T S March 12, 2025 Revised April 7, 2025 135 Coachman's Lane I North Andover, MA Operations&Maintenance Plan Inspection and Maintenance Form To be completed within 24 hours of a rainfall event of 0.5 inches or greater Inspector: Date: Days Since last Rainfall: Amount of last Rainfall: Structural Controls: Crushed stone infiltration trenches Structure Debris Vegetation SedimentOverall Identification Location Present Present Buildup Condition (inches) Southwesterly corner of Yes Yes Poor Driveway dwelling No No Fair Good House Southern limit of paved Yes Yes Poor Expansion driveway No No Fair Good Maintenance Required: Williams&Sparages I Engineers•Scientists•Surveyors 189 North Main Street I Suite 101 1 Middleton, MA (978)539-8088 1 www.wsengineers.com Page J 2 YV- c T S