Ways shall be continuous and in alignment with existing ways, as far practicable, and shall compose a convenient system with connections adequate to ensure free movement of vehicular travel.
If adjoining property is not yet subdivided , the applicant shall provide, in a manner acceptable to the Planning Board, a way or ways to said adjoining property. The plans should show such access as an extension of a right-of-way. The Planning Board may require that the extension be paved.
Proposed development of applicant's other contiguous land. The Planning Board may decline to approve a plan if the applicant owns land contiguous to that shown on the plan and fails to furnish sufficient data to enable the Planning Board to relate the proposed plan to the applicant's remaining land. Such data shall include the lines of proposed ways and lots in general manner and approximate grades, and such other details as the Planning Board may reasonably require.
No block shall exceed 1,000 feet in length in a residential subdivision.
In cases where, in the opinion of the Planning Board, soil conditions warrant, the Planning Board may require the subdivider to take borings at such locations as the Planning Board may deem necessary to provide adequate disclosure of subsurface conditions.
A dead-end street shall not be longer than 500 linear feet in combined total length unless, in the opinion of the Planning Board, a greater length is necessitated by topography or other local conditions, excluding financial considerations, or there are clear and compelling benefits to the Town for granting a greater length. For the purpose of these subdivision rules and regulations, a "dead-end street" is defined as any street, extension of a street, or systems of streets, connected to a through street only at a single point. Any such street shall be considered a dead-end street regardless of size or internal circulation patterns. Any street, segment of street, or system of streets which intersects only with a dead-end street shall be deemed to be an extension of the dead-end street. The length of a dead-end street shall be measured along its center-line from the edge of the pavement of the intersecting through street to the midpoint of the circular turnaround.
The number of dwelling units served by a dead-end street shall not exceed (10). Subdivisions containing more than 10 lots shall provide a minimum of two means of vehicular access to and from the subdivision onto previously existing public ways.
All intersections of ways shall be at an angle of 90° or radial to curves. Street lines at intersections shall be cut back to provide for radii of not less than 25 feet in residential subdivisions and not less than 35 feet in industrial and commercial subdivisions.
The number of ways converging at an intersection shall be kept to a minimum. The centerlines of said streets shall intersect at one common point.
Grades at intersection shall be designed to be no greater than 2% for the first 40 feet and no greater than 4% for the next 30 feet. Adequate sight lines for vehicles and pedestrians shall be provided for and maintained at all street intersections.
The intersection of centerlines of streets shall occur not less than 200 feet apart.
The grading at the intersection of ways shall be so designed as to be safe and convenient for travel and to direct the flow of surface water in a suitable manner.
The Planning Board will not approve any plans having so-called reservation strips which would prevent further extension of ways.
Where applicable proper connections shall be made with existing sewers, drains and water mains. Where, in the opinion of the Planning Board, after consultation with the appropriate town department, the capacity of an existing sewer, drain or water main is inadequate to accommodate the entire subdivision, only that portion thereof which, in their opinion can be adequately accommodated, shall be so connected.
Where adjacent property is not subdivided, provisions shall be made for extension of the utility systems by continuing appropriate sewers, drains and water mains to the exterior boundaries of the subdivision, at such size and grade as will allow for their proper projection.
Design analysis. A design analysis shall be submitted with each definitive plan submitted for approval. The design analysis shall include at least the following information:
Sanitary sewer system.
The calculations used in designing the sewerage system, including the method of estimating average flows (including infiltration allowances), the peaking factor used and the hydraulic design of the system, including quantity and velocity of flow under both average and peak flow conditions, shall be included.
Sanitary sewers shall be such as to ensure a flow of not less than two feet per second nor more than 10 feet per second.
Interceptor drains must be installed as conditions require.
A stormwater management plan shall be designed in accordance with the guidelines established in the publication entitled "Stormwater Management: Volume One: Stormwater Policy Handbook"; and "Volume Two: Stormwater Technical Handbook," prepared by the Department of Environmental Protection (DEP) and the Office of Coastal Zone Management (CZM), dated March 1997. This publication is hereby incorporated by reference.
The plan shall include a detailed design certified by a professional engineer registered in the Commonwealth of Massachusetts that will adequately dispose of surface water. Drainage improvements shall be designed so that there will be no adverse effects created by the proposed rates of runoff for the two-year, ten-year, and one-hundred-year storms. The location of the proposed development site within the regional watershed, and the hydrologic characteristics of the regional watershed shall be considered in the design and evaluation of the stormwater management system. Calculations shall be performed using the USDA SCS TR20 or'I'R55 methodologies. Predevelopment and postdevelopment drainage divides shall be shown on a diagram incorporated within the calculations. Off-site runoff entering the subdivision shall be properly considered and shall be calculated based on existing conditions, assuming all culverts and other restrictions are functioning properly. To the maximum extent feasible, stormwater shall be recharged rather than piped to surface water.
All surface retention and detention facilities shall be integrated into the grading and landscaping plan so as to minimize the visual impacts.
Infiltration or recharge.
Infiltration measures to recharge groundwater shall be designed to control increased peak rates of runoff due to development conditions. Infiltration basins, infiltration trenches, dry wells and vegetated swales shall be used as appropriate.
Design shall be based upon storage and infiltration of the increase in runoff due to the proposed development based upon the ten-year frequency storm as determined by SCS methodology.
The bottom of infiltration measures shall be a minimum of two feet above average high groundwater.
Design of infiltration measures shall provide for controlling the excess runoff from storms greater than the design storm up to and including the one-hundred-year storm event. The overflow shall be directed so that no increase in flooding of adjacent properties occurs or that access to roadways is made impassable.
Design shall be based upon the methodologies of the Standards and Specifications for Infiltration Practices, developed by the State of Maryland Department of the Environment, dated February 1984. Runoff volumes shall be determined using the SCS methodology.
Detention basins. Head-vs-discharge calculations shall be furnished for the detention outlet control. The outlet control shall be designed to minimize the possibility of clogging and shall permit reasonable access for cleaning. The detention basins shall have an emergency overflow provision in case of clogged outlet, or greater than one-hundred-year storm. The detention basin shall have 3:1 maximum side slope, finished with a six-inch layer of loam, and seeded.
Best management practices (BMP) for urban runoff quality should be implemented wherever possible in order to minimize the impact development will have on the quality of runoff.
The development should incorporate as many individual treatment devices as practicable. The use of vegetated swales and overland flows is encouraged where appropriate in order to reduce the amount of directly connected impervious surfaces throughout the proposed development.
Following is a list of BMP's which may be utilized and minimum guidelines for their design.
Vegetated swales. Swales should have side slopes equal to or greater than three feet horizontal to one foot vertical and be constructed at minimum slopes to reduce flow velocities and encourage infiltration. The swales should only hold water during and immediately after rainfall events and should be planted with vegetation suitable for soil stabilization, stormwater treatment and nutrient uptake. The water quality benefits provided by swales are limited due to short residence times.
Retention areas may be designed to infiltrate the first flush volume of stormwater. They should be designed to retain the first 1/2 inch of runoff or the runoff created by one inch of rainfall, whichever is greater.
Retention areas should have grassed bottoms and sides to reduce maintenance and maintain soil infiltration properties. A minimum of two feet should be maintained between the bottom of the basin and the seasonal high groundwater table.
Retention facilities should be located off-line, meaning only runoff from small storms and the first flush volume of large storms should be directed to and stored in the facility. The system must be designed in a manner which prevents large storm volumes from damaging the basin or resuspending previously settled pollutants.
Wet detention. Wet detention ponds consist of a permanent water pool, a zone where stormwater runoff is temporarily stored and treated, and a shallow littoral zone for biological quality enhancement. The basin should be designed to provide extended detention times of 24 to 48 hours for small storm events (first 1/2 inch of runoff or the runoff generated by one inch of rainfall, whichever is greater). Approximately 30% of the pond surface area shall be littoral with bottom slopes of 6:1 or flatter and planted with appropriate aquatic vegetation. The littoral zone shall be established around a minimum of 50% of the pond perimeter. The flow length between inlets and the pond outlet should be maximized to prevent short circuiting. A length-to-width ratio of at least 3:1 is recommended, diversion baffles, dikes or peninsulas may be utilized to increase the flow length. The outlet structure of the pond should be designed to retain oil, grease and floatable pollutants in the pond.
These recommendations are presented as guidelines only and are not intended to limit the innovation or implementation of new technology and designs. The burden shall be upon the engineer to demonstrate the effectiveness of the system in improving the quality of stormwater runoff quality.
Where access to a state highway is necessary, evidence of state permission must be presented to the Board with submission of the preliminary plan or definitive plan, as the case may be.
Where the street system within a subdivision does not connect with or have, in the opinion of the Board, adequate access from a Town, county or state (public) way, the Board may require, as a condition of approval of a plan, that such adequate access be provided by the subdivider and/or that the subdivider make physical improvements to and within such a way of access, in accord with the provisions of Article IV and Article V of these regulations, from the boundary of the subdivision to a Town, county or state way.
Where the physical condition or width of a public way from which a subdivision has its access is considered by the Board to be inadequate to carry the traffic expected to be generated by such subdivision, the Board may require the subdivider to dedicate a strip of land for the purpose of widening the abutting public way to a width at least commensurate with that required within the subdivision and to make physical improvements to and within such public way to the same standards required within the subdivision. Any such dedication of land for purpose of way and any such work performed within such public way shall be made only with permission of the governmental agency having jurisdiction over such way, and all costs of any such widening or construction shall be borne by the subdivider.
The Planning Board will not approve a subdivision of land where sole access to the subdivision tract in Westminster is through another town, unless the access is through an accepted public way at the time the subdivision is submitted. In general, lot lines should be laid out so as not to cross municipal boundaries.
Before approval of a plan, the Planning Board may require the plan to show a park or parks suitably located for playground or recreation purposes or for providing light and air. The park or parks shall not be unreasonable in area in relation to the land being subdivided and to the prospective uses of the land. The Board may, by appropriate endorsement on the plan, require that no building be erected upon such park or parks for a period of not more than three years without its approval. This land shall be made available for purchase by the Town. Failure to purchase within three years shall free the owners from restrictions.
Due regard shall be shown for all natural features, such as large trees, watercourses, scenic points, historic spots, and similar community assets, which, if preserved, will add attractiveness and value to the subdivision, and protect the natural resources of the Town.
Existing contours shall be preserved insofar as it is practical to do so. No change shall be made in the contour of the land that adversely affects the land abutting the proposed subdivision.
To be more attractive and economical, subdivisions shall closely adhere to the topography of the land, with streets designed so as to minimize the necessity for excessive cut and fill.
Building envelopes which restrict the placement of buildings within approved lots will be required when necessary to protect significant natural features or scenic viewpoints which might otherwise be adversely impacted from construction.
Street names shall be submitted to the Historical Commission for comment and be approved by the Fire Department to prevent duplication or close similarity to names of existing streets and to provide names in keeping with the character of the Town. Names reflecting geographic, natural or historical features are preferred to names of persons.
Prior to plan endorsements, lot numbers, as assigned by the Fire Department, shall be shown on the plan.
Lots shall be prepared and graded in such a manner that development of one lot does not cause detrimental drainage onto another lot, on areas outside the subdivision, onto roadways, or onto wetlands.