10/19/2020 Annual Town Meeting - Laserfiche WebLink

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1. For compliance with the Performance Standards of this By -Law, the design of treatment and infiltration practices must meet the current Massachusetts Department of Environmental Protection's Stormwater Management Standards and document compliance based on the Stormwater Handbook as amended, or other federally or State approved BMP design guidance. Projects must also comply with the Post -Construction Stormwater Management Requirements of the current Small MS4 General Permit, whichever is more stringent, using appropriate Stormwater Best Management Practices 2. For new single or two-family residences, recharge shall be attained through site design that incorporates natural drainage patterns and vegetation in order to maintain pre - development stormwater patterns and water quality to the greatest extent possible. Stormwater runoff from rooftops, driveways and other impervious surfaces shall be routed through vegetated water quality swales, as sheet flow over lawn areas or to constructed stormwater wetlands, sand filters, organic filters and/or similar systems capable of removing nitrogen and phosphorous from stormwater. 3. For new subdivision roadways or for lots occupied or proposed to be occupied by uses other than single or two-family homes, a stormwater management plan which; (a) utilizes site planning and building techniques including LID planning and development strategies, such as minimizing impervious surfaces and disturbance of existing natural areas, pervious reserve or overflow parking areas, multi -level buildings, parking structures, "green roofs" and storage and re -use of roof runoff, to minimize runoff volumes and the level treatment required to reduce contaminants, (b) minimizes erosion and runoff from disturbed areas during construction and (c) provides for the following: Artificial recharge or precipitation to groundwater through site design that incorporates natural drainage patterns and vegetation and through the use of constructed (stormwater) wetlands, bio retention facilities, vegetated filter strips, rain gardens, wet (retention) ponds, water quality swales, organic filters or similar -site -appropriate current best management practices capable of removing significant amounts of nitrogen and other contaminants from stormwater. Said stormwater treatment facilities shall be designed and sized to retain up to the first inch of rainfall from their catchment area within the area designed for nitrogen treatment, before any overflow to subsurface leaching facilities and otherwise meet the Stormwater Management Standards and technical guidance contained in the Massachusetts Department of Environmental Protection's Stormwater Management Handbook, as amended, or State -approved BMP guidance, whichever is stricter Volumes 1 and 2, dated March 1997, for the type of use proposed and the soil types present on the site. Such runoff shall not be discharged directly to rivers, streams, other surface water bodies, wetlands or vernal pools. Except for overflow from stormwater treatment facilities as described above and when there are no other feasible alternatives, dry wells shall be prohibited. 11