Article IV Design Standards and Required Improvements

Efforts shall be taken to maintain the continuity of the natural topography. Cut and fill shall be avoided in all instances possible. Except in areas where terracing is used, when excavation is necessary, grading shall be done in such a way that the resulting contours follow smooth natural curves that conform to the curves of the surrounding landscape. Straight or angular slopes or cuts that interrupt natural topography shall not normally be allowed. Existing contours shall be preserved insofar as it is possible through optimal location of streets and dwellings to the satisfaction of the Planning Board. In any event, no change shall be made in existing contours which adversely affects any land abutting the proposed subdivision.

Street layouts shall generally follow (parallel) the existing contours, or existing stream valley and natural swales, and should be designed with the objective of the preservation of natural features identified on the plan, as required in Subsection A above. All work on the ground hereinafter specified shall be performed by the applicant in accordance with these rules and regulations, in conformity with approved definitive plans and specifications and other construction requirements of the Town agencies concerned, and to the satisfaction of such agencies. In particular, all design, material, and construction specifications of the Marshfield Department of Public Works (DPW) relative to road and utility construction shall be adhered to unless otherwise provided for in these regulations. Where no detail is given under Marshfield DPW or the Department's specifications, reference shall be made to construction details of the Massachusetts Municipal Engineers Association. All streets in the subdivision shall be designed so that, in the opinion of the Board, they shall provide safe vehicular travel.

Location of streets.

In case a tract is subdivided into parcels larger than normal building lots, the Board may decline to approve the plan unless such parcels are arranged so as to allow the opening of proper future ways and logical and proper subdivision.

In case access to a subdivision crosses land in another municipality, the Board may require certification from appropriate authorities that such access is in accordance with the master plan and subdivision requirements of such municipality and that a legally adequate performance bond had been duly posted or that such access is adequately improved to handle prospective traffic.

The Planning Board may require space reserved for future streets (shown on said plan as paper streets) to provide for interconnecting ways and to avoid excessive dead-end streets. All portions of the tract being subdivided shall be taken up in lots, streets, public lands, or other proposed uses, so that remnants and landlocked areas shall not be created.

Provision satisfactory to the Board shall be made for the proper projection of streets, or for access to adjoining property which is not yet subdivided.

Reserve strips prohibiting access to streets or adjoining property shall not be permitted except where, in the opinion of the Board, such strips shall be in the public interest.

Roadways, culs-de-sac, detention facilities, sidewalks, and other required infrastructure or improvements shall not be placed within easements but within the right-of-way or on parcels not buildable for residential, commercial or industrial structures. Sewer, water, and drainage lines may be exempted from this position by the express waiver of the Board. All such land parcels, common land, or waivered easements shall be bounded with concrete bounds at all corners.

Where the street system within the proposed subdivision does not intersect with or have adequate access, in the opinion of the Planning Board, from an existing public way or approved subdivision way, the Board may require, as a condition of approval, that such adequate access be provided by the applicant through physical improvements from the proposed subdivision ways to the nearest public way or approved subdivision way most suitable in terms of width, grade and construction.

Width, alignment and grades of streets.

The following standards shall govern the design of streets:

Type of Street	Width of Way* (feet)	Width of Roadway* (feet)	Minimum Center-Line Radii	Maximum Center-Line Grade	Design Speed (mph)
Secondary	50 to 60	26	200	6%	33
Residential "D"	52	24	100	10%	29
Residential "C"	46	20	100	10%	23
Residential "B"	40	20	100	10%	23
Residential "A"	40	18	100	10%	23

	Type of Street	Minimum Center-Line Grade	Minimum Curb Radius at Street Intersections (feet)	Minimum Length of Tangents Between Reverse Curves (feet)
	Secondary	0.8%	30	100
	Residential**	0.5%	30	—

	NOTES:
	*	The Board may require that the traveled way be separated by a raised median strip with a width, minimum 20 feet, to be determined by the Board. In this case, the traveled way shall consist of two roadways, each with a minimum width of 20 feet or such greater width as the Board may specify.
	**	No area of single access, as defined in Article II, shall provide access for more than eight dwellings total.

Street intersection with center-line offsets of less than 150 feet shall not be permitted without a specific waiver from the Board.

Proposed subdivision streets shall intersect existing and other proposed streets at ninety-degree right angles whenever feasible for a distance of at least 100 feet from the intersecting street lines. Up to a ten-degree variation from the ninety-degree design objective will be allowed by the Board if the applicant demonstrates that a right angle is not feasible or practical.

All changes in grade exceeding 0.5% shall be connected by vertical curves meeting the following criteria for the purpose of ensuring suitable sight distances and to avoid harmful application of road salts and undue acceleration of vehicles and stormwater runoff velocities:

Type of Street	Minimum Stopping and Sight Distance (feet)	Crest Vertical Curve, Minimum K Value	Sag Vertical Curve, K Value
Arterial	275	60	60
Secondary	225	40	50
Collector	200	30	40
Minor residential	156	20	30

No center-line gradient is to exceed 6% on any curve having a center-line radius of less than 500 feet or 8% on one having a center-line radius of more than 500 feet.

Way lines shall be parallel or concentric, and the roadway shall be centered in the layout. Details and dimensions shown in the typical road cross sections in Appendix A shall be complied with.[1]

Editor's Note: Appendix A is included as an attachment to this chapter.

Layout radii concentric with required curb radii shall be required at all street intersections.

(8)

Leveling areas having a maximum slope of 2% for 100 feet at every intersection or terminus of secondary streets shall be provided. Leveling areas having a maximum slope of 2% for 50 feet at the intersection or terminus of a residential street shall be provided.

(9)

Solar access. The Planning Board may require orientation of ways and lots to be designed for preservation of maximum solar access opportunities for future residents of the subdivision, based on information as to existing topography and vegetative cover.

(10)

The above standards are based further on the typical roadway cross sections hereby incorporated as part of these regulations and street design standards as follows.

Dead-end streets.

Dead-end streets shall not be longer than 800 feet unless, in the opinion of the Planning Board, a greater length is necessitated by the topography or other local conditions. In general, maximum lengths are governed by the most stringent of the following performance standards:

[Amended 12-13-2021]

Frequency of vehicular conflicts (passing vehicles): more than eight dwelling units.

Convenience of design speed (to ensure observance of posted speed): 25 miles per hour, 1/4 mile (1,320 feet).

Stagnation of water lines, and user convenience during repair: 800 feet.

Child safety; elementary:

Walkers: 1,320 feet.

Bus pickup: 600 feet.

Dead-end streets shall be provided at the closed end with a turnaround having an outside roadway diameter of at least 120 feet in diameter with a property line diameter of at least 140 feet, the configuration of which is to conform to the typical cul-de-sac detail drawing.[2] The cul-de-sac bulb may be either the "off-set" design as shown in the typical cul-de-sac detail drawing or an "on-center" design.

[Amended 12-13-2021]

Editor's Note: See Appendix B included as an attachment to this chapter.

Upon construction of an extension of a dead-end street, the turnaround shall be removed by the extending applicant.

All culs-de-sac shall include a landscaped center island. A landscape plan for islands shall be provided. The only stormwater management facilities allowed within the center island of a cul-de-sac are landscaped bio-retention areas or a drainage forebay. When a drainage forebay is proposed, the applicant shall provide a landscape design that accommodates for easy of cleaning of the forebay without destruction of the landscaping. The use of cul-de-sac islands for stormwater bio-retention areas is encouraged and should be considered in the design process.

[Amended 12-13-2021]

Construction of roadway.

Construction of the roadway shall conform to the applicable typical cross section as shown and the hereinafter listed requirements.[3]

[3]

Editor's Note: See Appendix A included as an attachment to this chapter.

The entire roadway area shall be cleared and grubbed of all growth, and unsuitable material shall be removed to the required depth and as required by the Planning Board Engineer. Where sidewalks are provided, the grass strips may remain undisturbed. Applicants are not required to clear the entire right-of-way where wooded areas are provided in lieu of grass strips.

All fill and undisturbed soils within four feet of the finished subgrade shall be non-frost-susceptible and shall not contain more than 3% passing the 0.02 millimeter sieve to a minimum depth of four feet below the finished grade.

The roadway shall consist of a minimum of 10 inches of well-graded gravel within the following gradation range as established by the Department of Public Works, topped with a minimum of three inches of dense graded crushed stone (see typical cross section):

[Amended 7-24-2017]

	Sieve Size	Percent Passing by Weight
	3"	100%
	1/2	50% to 85%
	No. 4	40% to 75%
	50	8% to 28%
	200	0% to 8%

The subgrade shall be prepared to required lines and grades, and all fill shall be constructed in six-inch lifts. The subgrade shall be compacted to a minimum of 92% of maximum dry unit weight and at or near optimum moisture content as determined by the ASTM D 1557-66T, Method D. Preparation of the subgrade shall be approved by the Planning Board Engineer before any subsequent construction is permitted. All soil samples for testing purposes must be selected from the subject material by a qualified testing laboratory in a manner and quantity which will permit it to certify that they are representative of the material as a whole. Samples selected by anyone else will not be allowed as valid for the purpose.

After approval of the subgrade, the above-specified base course shall be prepared to lines and grades. Prior to paving of the base course, the project engineer shall certify in writing to the Planning Board that the location of survey controls is accurate and in accordance with the approved plan so as to minimize corrective work and changes required in the as-built plans. The base course shall be constructed in maximum lifts of six-inch lifts and shall be compacted to a minimum of 95% of maximum dry unit weight and at, or near, optimum moisture content as determined by the ASTM D 1557-66T, Method D.

The approved base course shall be paved with a minimum of three inches of Massachusetts Highway Department Type I-1 binder course and 1 1/2 inches of top course to lines and grades as required. The application of the top course shall be delayed for six months after binder course is applied. The pavement shall be placed and constructed in accordance with the specifications of the Marshfield Department of Public Works, shall be compacted to a minimum of 95% of laboratory density, and surface irregularities greater than 1/4 inch as measured with a ten-foot straight edge shall be corrected as determined by the Planning Board Engineer. Paving operations shall not start or continue without permission of the Planning Board Engineer, who will determine whether preparation, weather conditions, etc., are suitable. Notwithstanding, all paving operations are to be concluded for the season by November 20, regardless of weather conditions.

Construction of lots. Lots shall not be clear-cut and shall not be cleared prior to the establishment of a base course of pavement on the roadway. All clearing shall be done in accordance with that shown on the definitive plan and with the approved erosion control and construction management plan.

§ 405-10 Utilities.

General requirements. All utilities, including drainage, ponds, watercourses, swales, and lines, which service more than one dwelling unit must be located within street layouts or on properties set aside expressly for utility purposes rather than on building lots. Such utility areas shall have the boundaries defined by concrete bounds at all corners and shall be furnished with gated vehicle accessway for maintenance purposes to the proposed subdivision roadway or an existing accepted way. Such accessway shall be constructed to the satisfaction of the Planning Board and provided with permanent monumentation to inform abutters of location of said accessway on the ground. All utility line and accessway properties shall be a minimum of 20 feet in width.

Drainage. The applicant shall demonstrate to the satisfaction of the Planning Board that the project is designed to have no measurable or significant impact as to existing vegetation, topography, wetlands, and other natural or man-made features.

Criteria. The applicant shall review best available drainage systems for the appropriate application on the proposed development site. The development suitability of the site shall be based on natural features, such as soil types, slope, vegetative cover, water table, etc. Drainage plans shall be developed in consultation with the Planning Department and the Board's consultants with the following objectives and criteria in mind:

[Amended 7-24-2017]

Protection of surface water and groundwater quality.

Public safety.

Protection of existing abutting homes and septic systems.

Enhancement of and connection to natural drainage systems, including streams, floodplains, and associated wetlands.

Attractiveness of the plan, minimizing disruption to existing features, and successful imitation of natural systems.

(f)

Minimizing of long-term maintenance and/or reconstruction obligations to ensure the natural operation of the system and conserve manpower, energy, and fiscal resources.

Large developments; off-site mitigation. For developments in excess of 50 dwelling units, 50 acres, or which create more than three acres of impervious surfaces of all kinds, the Planning Board may require a storm drainage design analysis for the one-hundred-year storm at the watershed level, from drainage divide to tidal water, which demonstrates the adequacy of existing and proposed structures. If no measurable impact is shown, no off-site mitigation measures will be required by the Board. Said analysis shall include at least the following information: consideration of the entire watershed and the calculations used in designing the drainage system, including area calculations, intensity of rainfall, coefficient of runoff, time of concentration, discharge, pipe coefficients of roughness, and quantity and velocity of flow under design conditions at buildout capacity allowed under current zoning. Additionally, the following information shall be supplied:

Soil map for the sub area watershed.

Topographic map for the sub area watershed.

Land use map for the sub area watershed.

Pre-development drainage patterns on the site.

Post-development drainage patterns on the site.

All developments; on-site mitigation. In addition to the above watershed area analysis, the Planning Board shall require an on-site storm drainage design analysis for all proposed developments that mitigates the ten-, twenty-five-, and one-hundred-year storm events in accordance with the standards contained herein. The following information shall be required:

Calculations of wetland areas on site.

Analysis of soil conditions throughout the site.

Analysis of the square footage and percent of impervious coverage in relation to the square footage and percent of area devoted to drainage proposed.

Considerations of density of development appropriate to the above conditions.

Proposed use and assessment of effectiveness of water pollution and erosion control devices (e.g., absorption pillows, hay bales, swales, etc.).

(f)

Conformance with DPW standards for maintenance and performance.

(g)

Consideration of existing or potential public water supplies on or near the site.

(h)

Design calculations shall be based on the ten-, twenty-five-, and one-hundred-year storm event for all ponding areas and twenty-five-year storm event for pipe sizing.

(i)

TR-55 or TR-20 model calculations as deemed appropriate by the Town Engineer for the project design.

(j)

Demonstration of no increase in the rate of discharge from pre-development to post-development conditions.

(k)

Demonstration that post-development runoff volume shall not exceed pre-development volumes.

On-site drainage systems, including detention areas, must meet the following performance standards: A fifty-foot buffer zone of existing vegetation shall be retained between all detention or siltation structures and adjacent uses or structures for protection of scenic corridors, surface water and wetlands subject to MGL c. 130 and c. 131 and/or local wetland bylaws. A thirty-foot buffer zone of existing vegetation shall be retained between all point source discharges of stormwater and surface waters and wetlands. However, the provision of this subsection shall not prohibit the selective clearing of trees and shrubs, the establishment of new vegetation better suited to the proposed conditions, or the discharge of stormwater across such buffer areas as any of these actions may be permitted by the Conservation Commission under an order of conditions.

Use of retention basins shall not be permitted except in combination with detention facilities and for the express purpose of containing the design storm for a twenty-four to forty-eight-hour period, or in Water Resource Protection Districts where the stormwater management system includes measures to abate the contaminants prior to recharge and where, in the Board's opinion, retention facilities will promote recharge that will benefit surface water or groundwater resources. Detention facilities shall be permitted insofar as such systems are designed to function as natural wetlands, having characteristics of side slopes, gradients, vegetation and topographic location which follow naturally occurring wetland types. Use of such artificial storm drainage systems shall not substitute for proper erosion control measures, including appropriate design for soil and slope conditions. Design of such facilities shall observe the following guidelines:

Side slopes of wetland/detention areas shall be no steeper than 3:1 horizontal to vertical relationship.

A maximum of 2% slope shall be permitted for the bottom of the wetland/basin.

Where clearing and/or regrading of the site may be unavoidable for installation of the basin and necessary structures, vegetation shall be reestablished in conformance with the proposed landscape plan.

The prohibition of undesirable or unnatural accumulation of water shall refer to stagnant, pond waters, but not to wet systems, which are designed to have continuous stream flow through the basin. Ground infiltration by means of leaching pits, leaching catch basins or similar facilities is not allowed as a means of calculating or mitigating stormwater disposal.

Drainage outfalls shall be designed in conformance with this subsection and shall further provide rip-rapped aprons in accordance with typical details shown in the appendix of these regulations,[1] and in every case shall provide a minimum of 30 feet of vegetation swale before the property line and above the high-water line of any stream, swamp, bank or wetlands. As with other drainage structures, detention areas shall have a positive outfall and connection to an existing water body, including wetlands as defined above, except in Water Resource Protection Districts where the stormwater management system includes measures to abate the contaminants prior to recharge and where, in the Board's opinion, retention facilities will promote recharge that will benefit surface water or groundwater resources. Basins and swales shall be incorporated into separate land parcels for this exclusive purpose rather than be shown as easements over areas required for other uses, or required to serve purposes of other bylaws or regulations of the Town of Marshfield.

Editor's Note: See Appendix B included as an attachment to this chapter.

Subsurface drains or subdrains. In areas where the finished grade of the roadway is less than four feet above the water table or in areas where less than four feet of fill is placed above water in swampy places, or any standing water, or in other areas where, in the opinion of the Board, the subgrade must be drained, a system of subdrains shall be designed for such areas. In addition, laterals may be required as directed by the Board in areas in which an undue amount of water could accumulate in the subgrade. The system of subdrains shall be discharged into the storm drainage system or otherwise disposed of in a manner satisfactory to the Board.

(8)

Storm drains.

Storm drainage design is to conform to specifications of the Master Drainage Plan when applicable. Design shall be on the basis of a twenty-five-year storm. A complete storm drain system shall be designed for each street in the subdivision and shall be so laid out and of sufficient size to permit unimpeded flow of all natural waterways, to provide adequate drainage of all portions of the street system so that water does not accumulate thereon, to intercept stormwater runoff from the adjacent lots of the subdivision, and to eliminate undesirable or unnatural accumulation of water on any portion of the subdivision or surrounding property to the satisfaction of the Board. The storm drain system shall include gutters, catch basins, manholes, culverts, drain lines, head walls and such other items as may be required to complete the system to the satisfaction of the Board.

Catch basins and manhole structures shall be preferably reinforced, precast concrete. Structures are not to be backfilled until inspected by the subdivision inspector.

Catch basins shall be located in pairs, one on each side of the road, at all low points or sag curves in the roadway, at intervals of 300 feet for grades up to 4%, 250 feet for grades from 4% to 6% and 200 feet for grades more than 6% and at or near corners of the way at intersecting streets. Catch basins will be in conformance with Marshfield DPW standards. Double-grate catch basins should be provided where warranted by runoff conditions.

Manholes shall be located at all changes in direction, either horizontally or vertically, of a drain line, or so located that no drain line greater than 300 feet in length would exist without either a catch basin or manhole. Manholes shall conform to Marshfield DPW standard.

[Amended 7-24-2017]

Culverts shall be designed on the basis of a one-hundred-year storm and on the assumption that the entire drainage area is built up to the density and in the manner which the applicable section of the Zoning Bylaw allows. The calculations (or a copy thereof) necessary to determine the size of any culvert which carries a brook, stream, river or other natural waterway shall be submitted to the Board for review. Such calculations shall be based on a method (Rational Method or Talbot's Formula) acceptable to the Board for determining the size of waterway openings. All culverts shall have a head wall at each end, and any culvert over 36 inches in diameter shall include additional protection as approved by the Board for the roadway side slopes at the upstream end.

(f)

All the drains shall be a minimum of 12 inches in diameter and shall be laid on a slope of not less than 1/2 of 1%. If the system is designed as a self-cleaning system, the Board may accept a lesser minimum slope for the drain lines. A maximum pipe velocity of 10 feet per second shall be allowed, with a minimum velocity of 2 1/2 feet per second required. All final outfalls within or serving the subdivision shall extend to a natural waterway, or to drainage easements or pipe systems leading to waterways, and such pipe shall have a capacity of 25% greater than required by the calculations. Provisions shall be made for the disposal of surface water intercepted or collected by the system in such a manner that no flow is conducted over Town ways or over the land of others unless a drainage easement is obtained or unless such flow, in essentially the same quantity, previously existed in the same location. Where adjacent property is not subdivided, provision shall be made for extension of the system by continuing appropriate drains to the boundary of the subdivision at such size and grade as will allow their proper projection.

(g)

A head wall with wing walls shall be provided at the outfall end of all drains. Use of pre-formed flared end sections for this purpose is also acceptable.

(h)

No drainage outfall shall discharge at an elevation below the high-water line of a swamp, stream, or body of water as defined in Article II.

(i)

Pipe outfalls shall be located away from dwellings a distance down grade equivalent to the required lot depth in the applicable zone.

(j)

In the event that no specific requirement is given in these regulations, Massachusetts Highway Department standards shall apply.

(9)

Calculations. The calculations (or a certified copy thereof) to determine the sizes of all pipes and culverts in the drainage system shall be submitted to the Board for review Such calculations should be based on the Rational Method and prepared by a registered professional engineer. A drainage analysis map shall show the tributary watershed area and downstream area affected by runoff, and drainage computations shall consider the entire watershed area. Where excessive poor soils or disturbed cover exists, calculations shall give consideration to frozen ground conditions, soil types and cover for all affected areas, including but not limited to lawns, base ground, graveled ways, etc.

Sewer. Sewer pipes and related equipment, such as manholes and connecting Y's, shall be constructed in conformity with Marshfield DPW standards. Sewer pipes shall be installed where sewering is proposed by the Sewerage Master Plan.

Water. Preliminary approval for availability of adequate water supply must be obtained from the Board of Public Works. Design of the proposed installations of water distribution lines and appurtenances must also be approved by that Board. Water pipes and related equipment, such as hydrants and main shutoff valves, and service boxes, shall be installed within the subdivision as necessary to provide all lots on each street with adequate water supply for domestic and fire protection use and in conformity with specifications of the Department of Public Works (Marshfield). Pipe size shall be as specified by the Board of Public Works, but in no case shall be less than eight inches in diameter. The entire cost of installation, including connection to the Town system and wages of the inspector, shall be borne by the owner. The Water Supervisor shall approve all materials. Taps on water mains shall be made and located as directed by the Water Division. Titles to mains and hydrant will not be accepted until at least six months after pressure has been put onto them, all measurements have been turned over to the Water Division, and all lines proven tight, after which 10% of the cost of the entire water installation or a minimum of $500 will be held out for an additional year. No services shall be connected at the property line until an application has been filed at the Water Division office. Final approval of water system specifications shall be given by the Department of Public Works. Water lines in excess of 800 feet shall be required to be looped.

[Amended 7-24-2017]

Pipes.

Sewer, water, gas and other underground utilities, if any, together with all connections to the proposed subdivision lots on both sides of the street, shall be laid after the roadway is subgraded but before application of the gravel base occurs. All such pipes shall be given a definite location as per the typical cross sections contained in the appendix of these rules and regulations.[2]

Editor's Note: See Appendix A included as an attachment to this chapter.

Drainage pipes shall be of not less than 12 inches reinforced concrete, coated corrugated aluminum or plastic construction. All drainpipes shall have a minimum of 2 1/2 feet of cover, except that reduced cover may be permitted at the discretion of the Board if Class V reinforced concrete pipe is specified. Each length shall be laid true to line and grade as shown on the plan. Each length shall have a full firm bearing throughout.

The backfilling of all trenches shall be thoroughly tamped in accordance with Article IV, Design Standards and Required Improvements, and shall not be puddled.

Underground utilities.

All electrical, telephone, cable television and other utility wires shall be placed below ground in every subdivision unless the Board determines that such placement is not feasible or is not in the best interest of the Town. Such utilities shall be constructed according to the information contained in the appendix.

All service connections for utilities shall be clearly marked at the lot line and shall be installed so that electric, telephone, sewer, and water services are located perpendicular to the street at the lot line. Telephone and electric utilities shall be located at alternate side lot lines (at every other lot corner).

Easements. All easements shall comply with the following requirements:

If a waiver is granted allowing utility pipe lines to be placed in easements, said easements shall be 20 feet (or more if deemed necessary) in width and shall be adjacent to or centered on property lines unless otherwise permitted. Concrete bounds shall be set at all corners and angle points for the information of the landowners.

Where a subdivision is traversed by a watercourse, drainageway, wetland, stream, or channel, the Board may require that there be provided a stormwater easement or drainage right-of-way of adequate width to conform substantially to the lines of such watercourse, drainageway, wetland, stream or channel and to provide for construction, maintenance, access or other necessary purposes.

§ 405-11 Erosion control facilities; criteria and objectives.

All easements must be of a form acceptable to the Town Clerk.

Stone walls. Any removal or alteration of trees/stone walls on Town-designated scenic roads shall require an application and public hearing pursuant to the Scenic Road Act.[3]

[3]

Editor's Note: See MGL c. 40, § 15C, and Ch. 250, Streets and Sidewalks, Art. VII, Scenic Roads, of the Town General Bylaws.

As required under § 405-8 above, an erosion control plan shall be submitted which meets the following objectives and criteria:

Keep disturbed areas small. No more than 50 feet wide, 100 feet long, and 20% of a single lot, or five acres of the overall tract, are recommended guidelines. Consideration of topographic, soil, and vegetative characteristics shall be demonstrated through identification of erodible soils, steep slopes, stream banks and drainageways, and measures designed to limit disturbance of these areas.

Stabilize and protect disturbed areas quickly. Exposed areas and stockpiles should be revegetated within 30 to 60 days. Two methods are available for stabilizing disturbed areas, mechanical (or structural) methods and vegetative methods. In some cases, both are combined in order to retard erosion. The selected measure should be identified in a construction management plan submitted with the subdivision application.

Keep stormwater runoff velocities low. Acceptable velocities are in the two to 10 feet per second range. The removal of existing vegetative cover during development and the resulting increase in impermeable surface area after development will increase both the volume and velocity of runoff. These increases must be taken into account when providing for erosion control.

[Amended 7-24-2017]

Protect disturbed areas from stormwater runoff. Conservation measures can be utilized to prevent water from entering and running over the disturbed area. Diversions and other control practices to intercept runoff from higher watershed areas, store or divert it away from vulnerable areas, and direct it toward stabilized outlets should be utilized. Selected measures should be identified in the proposed construction management plan.

Retain sediment within site area. Sediment can be retained by two methods, filtering runoff as it flows and detaining sediment or detaining runoff for a period of time so that the soil particles settle out. The best way to control sediment, however, is to prevent erosion.

§ 405-12 Other facilities.

Sidewalks. The Planning Board shall require sidewalks of such width and construction to be constructed in accordance with the typical cross section.[1] In no case shall sidewalks be less than five feet in width. They shall be of broom-finished portland cement concrete with one-inch-deep score lines spaced five feet apart on centers. Sections shall be a maximum of 30 feet in length, with sections separated from each other and from driveway sections by one-half-inch-thick premolded bitumastic filler. The depth (thickness) of concrete and of filler shall be four inches except at driveways where it shall be six inches. Portland cement concrete driveway aprons from the sidewalk to the gutter line shall be constructed to the same specifications as the sidewalk where it crosses the driveway.

Editor's Note: See Appendix A included as an attachment to this chapter.

Driveways. Proposed driveways shall be shown on the road construction plan and topographic plan and shall be designed to intersect the street at a grade not greater than 3% for a distance of 25 feet back from the edge of the traveled way and shall intersect generally at right angles and in locations having proper sight distances. Curb cuts for driveways shall not be placed within 50 feet of street intersections. Driveways within the lot shall not contain grades greater than 15%.

Vegetation.

Every effort shall be made to preserve the existing trees on the right-of-way and on the lots to be sold. Filling and cutting of roadways shall be done in such a manner as to preserve the trees and existing soil cover whenever possible. The Planning Board shall require that the applicant shall provide and plant suitable shade trees spaced not less than 40 feet apart along the way, variety to be approved by the Planning Board. Trees to be planted shall have a minimum height of 12 feet with eight-foot head clearance and shall be of at least three-inch caliper at the height of 42 inches from ground level. Street trees may be planted within the right-of-way or within a twenty-foot-wide street tree easement shown on both sides of the right-of-way. It is recommended that the street trees be planted a minimum distance of 10 feet from the roadway pavement or sidewalk.

[Amended 12-13-2021]

On slopes along the way where stabilization is required, or where lawn maintenance and moving may be unfeasible, a combination of ground covers and shrub plantings may be required by the Board. The landscape plan shall specify species, quantities and sizes of proposed plantings.

Streetlighting. Streetlighting shall be provided only for the purpose of vehicular and pedestrian safety as recommended by the Police Safety Officer at locations that may present particular hazards, e.g., street intersections. Illumination for general residential purposes or security is not intended in single-family residential areas. The Select Board shall approve proposed streetlighting prior to endorsement of the definitive plan.

[Amended 10-18-2021 STM by Art. 32]

(Reserved)[2]

Editor's Note: Former Subsection E, Fire alarm systems, was repealed 12-13-2021.

Open space and trails. Before approval of the plan by the Board, it may require a trail connection from the roadway or sidewalk to the on-site open space or abutting open space. The Planning Board shall seek comments from the Conservation Commission, the Recreational Trail and Open Space Committees.

[Amended 12-13-2021]

Slope stabilization.

Slope is defined as the ratio of vertical rise over horizontal distance. Upon completion of grading and replacement of topsoil, slopes shall be appropriately stabilized to prevent erosion. Excessive slopes shall not be permitted. The Board shall approve an adequate slope stabilization plan.

The following guide is recommended:

Slopes more than 1 in 2: riprap or terracing. Not allowed where alternative layouts permit lesser slopes.

Slopes of 1 in 8 to 1 in 2: sod or establishing vegetation or seedlings in association with webbing or approved mulch placed over the soil. Not allowed where alternative layouts permit lesser slopes.

Slopes of 2 in 20 to 1 in 8: plant seed in association with webbing or approved mulch placed over the soil.

Appropriate temporary measures should be taken to prevent erosion of bankings and slopes during construction.

Retaining walls.

Wherever retaining walls may be required, design and type of wall construction shall be submitted to the Board for approval prior to installation.

All retaining walls shall be constructed on the line of the street layout.

Retaining wall shall have a maximum individual height of four feet and a total combination of no more than 12 feet in height.