Plans shall adequately describe the proposed activity and its effect on wetlands and related water resources and adjoining upland resource areas. Pre-project and post-project hydrology should remain fundamentally the same as it pertains to protecting wetlands functions and values. Some minor degree of change in hydrology is inevitable in any engineering/construction project, and within reasonable limits the Commission shall permit such variation when, in its judgment, such changes will not produce a significant impact on wetlands functions and values. The use of aboveground vegetated swales, infiltration methods, and other low-impact drainage designs will be given preference over subsurface drainage structures. The Commission encourages the replacement of new impervious surfaces with pervious areas or other methods to maintain the original hydrology.
The following items are a minimum standard and are not intended to represent a complete presentation of what a plan would show. The applicant may submit or be required to submit to the Commission, any additional information which would assist in review and which is deemed necessary to determine the proposed effect on the interests protected by the Bylaw.
Any revised plans shall be submitted, in both hard copy and electronically, no later than 12:00 p.m. one week prior to a scheduled continuance of a public hearing. All revised plans shall be sent to the Department of Environmental Protection regional office at the same time for additional review and comment.
All applications shall include:
A. General information.
(1) All drawings shall be drawn with the title designating the name of the project, location, and names of the person(s) preparing the drawings and the date prepared, including the latest revision date. The Commission may require that plans and calculations be prepared and stamped by a registered professional engineer (PE) or other registered professional when it deems that the complexity warrants such certification. Registered professional engineers shall indicate the engineering discipline in which they are certified. Plans depicting proposed drainage systems must be certified by a registered professional civil engineer.
(2) An 8 1/2" x 11" photocopy of the U.S.G.S. quadrangle sheet showing the location of the proposed project.
(3) An 8 1/2" x 11" section of the Tax Assessors map on which the site of the proposed activity is outlined in red.
B. Site plan. The applicant shall submit a site plan at a scale of one inch equals not more than 40 feet, showing the following:
(1) When excavation, fill, or other construction is proposed, existing and proposed contours (in contrasting symbols) shall be shown in feet above sea level or relative to a datum with intervals no greater than two feet; date of ground survey shall be given.
(2) Delineation of all wetlands, lands subject to flooding, water bodies, waterways, ditches, creeks, rivers, streams, and ponds, whether natural or manufactured, continuously or intermittently flowing. The upland boundary of all bordering vegetated wetlands. The 100-year flood elevation.
(3) A delineation of the 100-foot and 200-foot (if required by §
147-4A) buffer zones.
(4) A delineation of all alterations proposed in or having an impact on wetlands.
(5) Existing stone walls, buildings, rock ridges and outcroppings.
(6) Location, extent, and area of all existing and proposed structures, roadways, paved areas, septic systems, wells, tanks, and utility easements.
(7) Proposed lowest elevation of cellars or floors.
(8) Existing and proposed location, rim elevation, and invert elevation of all catch basins, drains, culverts, and other drainage structures immediately upstream and downstream of the site, as well as those on-site.
(9) Details and locations for all temporary erosion controls proposed.
(10) Proposed permanent pollution control devices on-site, such as hooded catch basins, flow dissipaters, or vegetative buffers.
(11) Cross-sections showing existing and proposed slope, elevations, bank, and bottom conditions of each watercourse to be altered. Locations of cross sections shall be specified.
(12) Proposed location of any fill material that will be stored on site.
(13) The "limit of work" line.
(14) All plans submitted to the Commission for review shall be in color or highlighted with transparent marker pen as follows:
(b) Green: fifty-foot setback from wetland line;
(c) Yellow: seventy-five-foot setback from wetland line;
(d) Pink: 100-foot (and 200-foot, if required) setback from wetland line;
(e) Orange: siltation barrier.
C. Stormwater management. A compliance evaluation is required to demonstrate how the proposed project meets the applicable stormwater management standards identified in this section of the regulations, when triggered. No resource area other than buffer zone, riverfront area, bordering land subject to flooding, or isolated land subject to flooding may be altered or filled for the impoundment, detention, or retention of stormwater and the applicable performance standards for these resource areas under these regulations shall apply to any such alteration or fill. Except as expressly provided in § 147-14C(1) or (2) below, stormwater runoff from all industrial, commercial, institutional, office, residential, and transportation projects that are subject to regulation under the Bylaw including site preparation, construction, and redevelopment and all point source stormwater discharges from said projects within any resource area shall be provided with stormwater best management practices to attenuate peak rate and volume of runoff, attenuate pollutants, and to provide a set back from receiving waters and wetlands in accordance with the applicable standards below and the Massachusetts Stormwater Handbook. In project design, the applicant shall consider environmentally sensitive site design and low impact development techniques to manage stormwater.
(1) The stormwater management regulations set forth at 310 CMR 10.05(6)(k) to (q) shall apply to any project pursuant to said regulations where any work is proposed within any Bylaw resource area or where a stormwater discharge is proposed within any resource area, including the buffer zone. In addition to meeting the 10 stormwater management standards at 310 CMR 10.05(6)(k), stormwater best management practices shall be provided to reduce by at least 5% match or improve the peak runoff rates and volumes under proposed conditions compared to existing conditions for the two- and ten-year frequency storm events, and peak runoff rates and volumes under proposed conditions compared to existing conditions shall not exceed existing peak runoff rates and volumes for the fifty- and 100-year frequency storm events. Drainage calculations must include existing and proposed runoff rates and volumes for the two-, ten-, fifty-, and 100-year frequency storm events to all site design points with a narrative summary and summary table and be stamped and signed by a registered professional engineer. Such calculations shall be conducted in accordance with standard recognized engineering practices using rainfall data from the "Extreme Precipitation in New York & New England" (www.precip.net) developed by Northeast Climate Research Center at Cornell University or other methods approved by the Commission. The specific rainfall data to be used in such calculations under these regulations are from Harvard Center and are 3.05 inches for the two-year, twenty-four-hour event, 4.54 inches for the ten-year, twenty-four-hour event, 6.75 inches for the fifty-year, two-hour event 8.02 inches for the 100-year, twenty-four-hour event.
(2) Projects that do not trigger the stormwater management regulations cited in § 147-14C(1) above shall, at a minimum, meet the following stormwater management standards when the proposed project would result in greater than a 5% increase in impervious surfaces on the site:
(a) There shall be no new stormwater conveyances that discharge untreated stormwater directly to or cause erosion within Bylaw resource areas;
(b) Peak runoff rates and volumes under proposed conditions must be reduced by at least 5% compared to existing conditions for the two- and ten-year frequency storm events and must not exceed existing peak runoff rates and volumes for the fifty- and 100-year frequency storm events. Drainage calculations must include existing and proposed runoff rates and volumes for the two-, ten-, fifty-, and 100-year frequency storm events using the rainfall data provided in § 147-14C(1) above to all site design points with a narrative summary and summary table and be stamped and signed by a registered professional engineer;
(c) Loss of recharge to the groundwater shall be minimized by infiltration measures, including, but not limited to environmentally sensitive site design, low impact development techniques, stormwater best management practices, and good operations and maintenance. This standard shall be met when the stormwater management system is designed to infiltrate the required recharge volume based upon soil type in accordance with the Massachusetts Stormwater Handbook. There shall be pretreatment of stormwater runoff from any impervious surface other than a non-metal roof prior to infiltration. Documentation from soil test pit(s) excavated in the area of any proposed infiltration system shall be included in the filing to demonstrate a minimum of two feet of separation from the bottom of the proposed system and seasonal high groundwater, and to confirm the soil type used in the infiltration calculations. In the case where two feet of separation cannot be achieved or when the soils do not support infiltration, other stormwater management options including low impact development techniques shall be considered;
(d) Site and stormwater management design shall consider the presence of critical areas. Critical areas are recharge areas for public water supplies as defined at 310 CMR 22.02 (i.e., Zone I, Zone II, and Interim Wellhead Protection Areas for groundwater sources and Zone A for surface water sources), Outstanding Resource Waters and Special Resource Waters as designated at 314 CMR 4.06, bathing beaches as defined at 105 CMR 445.000, and cold-water fisheries as defined at 314 CMR 9.02 and 310 CMR 10.04. A discharge within Zone II of a public water supply or within or near any other critical area requires the use of specific source control and pollution prevention measures and the use of specific structural stormwater best management practices identified for such areas in the Massachusetts Stormwater Handbook. A discharge is near a critical area if there is a strong likelihood of a significant impact occurring to said area, considering site-specific factors. Stormwater discharges to critical areas shall be removed from or set back from receiving waters or wetlands and shall receive the highest and best practical method of treatment commensurate with the scope of the proposed project. There shall be no stormwater discharges to Zone I of a public water supply well unless essential to the operation of the public water supply;
(e) A construction period erosion and sedimentation control plan commensurate in scope with the proposed project and its potential to affect resource areas shall be provided for review and implemented during construction; and
(f) An operations and maintenance plan commensurate in scope with the proposed project shall be provided for review and implemented post-construction which identifies the responsible party and provides the inspection and maintenance requirements for all proposed stormwater system components.