A. 
Subdivision plans shall comply with the following minimum design standards. Applicants are encouraged to exceed these minimum standards whenever possible.
B. 
It is difficult to create design standards appropriate to all types and sizes of subdivisions. While the standards included here are applicable to the vast majority of cases, there may be limited instances where different standards may apply, particularly for commercial and large-scale development. For this reason, applicants are urged to discuss their proposals with the Planning Board staff and Board members early in the concept stage of planning, before money is spent on the final design, in order to determine if any different or additional standards would apply due to the unique character of the proposal. The Planning Board reserves the right to require design standards above the minimum standards described herein when a finding is made by the Board that the purposes of the Subdivision Control Law would be better served by doing so.
A. 
Monuments shall be installed on both sides of the street:
(1) 
At all intersections;
(2) 
At all points in change of direction or curvature; and
(3) 
No less frequently than one monument every 500 feet for straight sections.
B. 
Monuments shall be installed at each lot corner along the street.
C. 
All monuments shall be of reinforced concrete, five inches by five inches by 30 inches. Monuments to be set shall be shown on "as built" plans as a solid box.
A. 
Street width shall depend on the street's functional classification, as follows:
(1) 
A minor subdivision street which, in the opinion of the Board, provides access to abutting lots, and is not intended for use by through traffic, shall be paved to a width of not less than 20 feet and shall be designed and constructed in conformance with Part 5, Specifications for Construction of Required Improvements, and as shown on Plate No. 5 in Appendix A.[1]
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
(2) 
A secondary subdivision street which, in the opinion of the Board, carries traffic from minor streets to major streets or community facilities shall be paved to a width of not less than 22 feet and shall be designed and constructed in conformance with Part 5, Specifications for Construction of Required Improvements, and as shown on Plate No. 5 in Appendix A.
B. 
Street intersections shall be laid out as nearly as possible at right angles. No street shall intersect any other street at less than 60°.
C. 
Changes in grading exceeding 0.5 of 1% shall be connected by vertical curves of sufficient length.
D. 
Sight distances for subdivision roads intersecting major Island roads shall not be less than 300 feet.
E. 
Design standards.
(1) 
The following design standards for streets shall apply:
Minimum Design Standards for Streets
Type of Street
Width of Layout
(feet)
Width of Roadway
(feet)
Minimum Center-line Radius
(feet)
Maximum Center-line Grade
Minimum Center-line Grade
Minimum* Curb Radius at Street Intersection
(feet)
Secondary
40
22
300
6%
0.5%
25
Minor
40
20
200
10%
0.5%
15
*
Right-of-way shall be symmetrical with curbline radii of the street.
(2) 
These design specifications represent minimum standards. More stringent design criteria may be required by the Board.
A. 
Dead-end streets shall not be longer than 1,000 feet unless, in the opinion of the Board, a greater length is necessitated by topography or other local conditions.
B. 
Dead-end streets shall be provided at the closed end with a turnaround having an exterior layout radius of at least 60 feet. The roadway shall have an exterior radius of at least 50 feet. An island suitably landscaped with grass, ground cover, trees, natural rock and/or elements blending with the surroundings shall be provided in the center of the turnaround with a radius of at least 30 feet. The island shall be enclosed with vertical granite curbing with six-inch reveal from the roadway pavement. (See Appendix A, Plate Nos. 1 and 2, for turnaround and island plan.) An island shall not be required in a temporary turnaround; however, the turnaround shall be paved. When the dead-end street is extended, the turnaround easement shall terminate and the applicant shall be required to remove, regrade and restore the turnaround area to the satisfaction of the Planning Board. Alternate turnarounds are contained in Appendix A, Plate Nos. 3 and 4. The temporary turnaround shall conform to Appendix A, Plate Nos. 1, 2, 3 and 4.[1]
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
All subdivision streets shall be constructed of an approved roadway pavement as specified within Part 5, Specifications for Construction of Required Improvements.
A. 
Rural road alternative. In certain cases, where approval is sought for a subdivision on land of a rural or sensitive nature, the Board may, at its discretion, waive strict compliance with the requirements of § 358-2.25 in order to allow roads more in keeping with the character of the rural landscape. In such cases, the Board will consider the following factors before granting a waiver of the standard road requirements:
(1) 
Zoning and density of land use.
(2) 
Number of lots and probable traffic volume in the proposed subdivision.
(3) 
Applicable covenants restricting future density increase (e.g., one dwelling per lot).
(4) 
Projected future development likely to use road.
(5) 
Other public uses of the road (e.g., beach access).
(6) 
Road length.
(7) 
Design of the road and of the development with respect to preservation of open space, scenic amenity, and other conservation measures.
B. 
The following standards shall apply to rural roads:
(1) 
Rural roads shall be designed with consideration for the natural contours of the landscape, and should provide adequate natural drainage at all points, while minimizing erosion both on and beside the road. Depressions should be filled to a grade above that of the adjacent roadside and, where possible, natural drainage measures (i.e., swales and retention ponds) shall be employed rather than storm sewers and catch basins. Where natural drainage is used, drainage easements shall be provided to permit maintenance and to countenance possible water accumulation. Appropriate measures should be taken to reduce siltation and to preserve and restore roadside vegetation.
(2) 
Rural roads shall provide adequate access for emergency vehicles and normal traffic through the provision of turnouts at appropriately spaced intervals.
(3) 
Design and construction of rural roads shall conform to the specifications of Type 8 pavement (stabilized gravel base) described in § 358-2.54 and Appendix A.[1] Reductions in the width of the traveled way may be permitted, but in no case shall this way be less than 12 feet in width. A standard forty-foot-wide layout shall be maintained throughout.
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
(4) 
When the rural road alternative is approved, the applicant shall be required to establish a road maintenance endowment fund, of a sum to be specified by the Board, to ensure the proper long-term maintenance of the road(s). This fund shall be administered by a homeowner's association, with the Planning Board named as a third-party enforcing agent, and shall be used for road reconstruction and its supporting engineering review and inspection. The Planning Board shall devise a maintenance schedule prior to approval, and this schedule shall be incorporated into the documents creating the fund.
C. 
The Board reserves the right to require applicants to use this rural road alternative where it deems appropriate, notwithstanding the submission of an application expressly requesting use of any of the other roadway specifications outlined in § 358-2.54.
A. 
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. The subdrain shall consist of at least one longitudinal drain for each side of the paved roadway. 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 drain system or otherwise disposed of in a manner satisfactory to the Board.
B. 
Storm drains. A complete storm drain system shall be designed for each street of the subdivision to the satisfaction of the Board 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, and to be completely compatible with the existing Town municipal services and waterways. Those conditions which result from a twenty-five-year storm shall be assumed as a basis for design of the street drains. The storm drain system shall include gutters, catch basins, manholes, culverts, drain lines, concrete headwalls and such other items as may be required to complete the system to the satisfaction of the Board.
(1) 
Catch basins shall be located in pairs, one on each side of the roadway, at all low points or sag curves in the roadway, at intervals of not more than 300 feet on continuous grades of the roadway, at or near the corners of the roadway at intersecting streets, and at the end of turnarounds. Invert and frame elevations shall be shown.
(2) 
Manholes shall be located at all changes in direction, either horizontally or vertically, of a drain line or at the intersection of two or more drain lines, or so located that no drain line greater than 500 feet in length would exist without either a catch basin or manhole. Invert and frame elevations shall be shown.
(3) 
At least one leaching basin shall be annexed to each pair of catch basins proposed. Leaching basins shall be placed in accordance with the above Subsection B(1) and (2) and shall conform to the specifications contained within § 358-2.52. (See Appendix A, Plate No. 12.[1])
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
(4) 
All roadway drain pipes shall be a minimum of 10 inches in diameter and be laid on a slope of not less than 0.5%. The designed maximum velocity shall not exceed 12 feet per second. All outfalls shall extend to, and be compatible with, either a natural waterway or an existing drainage system. The ground elevation of all outfall pipes, swales, channels or drainage ditches discharging to a stream, brook, pond, marsh or other wetland should be 0.5 foot to one foot above mean water elevation, or at higher elevations if required by the Planning Board because of special local situations based on consultation with the Conservation Commission. Provision 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 above grade, or over the land of others unless a drainage easement is obtained. Where adjacent property is not subdivided, provision shall be made for extensions of the system by continuing appropriate drains to the boundary of the subdivision at such size and grade as will allow their proper projection.
(5) 
Gas and oil separators shall be installed as required by the Planning Board. (See Appendix A, Plate 13.[2])
[2]
Editor's Note: Appendix A is included as an attachment to this chapter.
(6) 
Drainage systems within the Public Wellhead Recharge District (as designated in Chapter 139, Zoning, § 139-12B, of the Code of the Town of Nantucket) shall be designed in conformance with the publication entitled "Artificial Recharge: Evaluation and Guidance to Municipalities: A Guide to Stormwater Infiltration Practices in Public Water Supply Areas of Massachusetts," prepared by the Pioneer Valley Planning Commission.
C. 
Open drainage systems.
(1) 
Open drainage systems of swales, ridges, and slopes shall be designed to fit the natural contour of the land as much as possible. Disturbed land shall be landscaped to conform to the surrounding area and planted to eliminate the possibility of erosion and siltation. In no case shall side slopes in disturbed areas be greater than 25%. Swales and drainage channels shall have a minimum grade of 0.5% and a maximum grade of 5%, although for small areas draining not more than 0.5 acre, grades of up to 10% are permissible. The ground shall be sloped so that there is no stagnant water or artificial pools on the site attributable to the open drainage system. Drainage channels and swales shall be provided with easements which shall also permit access by the Town of Nantucket for maintenance purposes. Easements shall conform to § 358-2.29 of these rules and regulations. Drainage channels and swales shall be shown on all plans.
(2) 
Where the Planning Board determines that the public interest and best interests of the Town and the subdivision will be served by extension of the drainage system outside the boundaries of the subdivision, the Planning Board may require the applicant, at its own expense, to continue the layout and construction of the drainage system to a point outside the boundaries of the subdivision where the drainage system may be connected to, and be compatible with, either a natural waterway or an existing public drainage system.
Easements for utilities, bicycle paths and pedestrian paths outside of street rights-of-way shall be provided and recorded as required and shall be at least 20 feet wide for water mains, sanitary sewers and storm drains, 10 feet wide for underground electrical, telephone and cable TV lines, and 15 feet wide for bicycle and pedestrian paths. Slope easements and site and/or scenic easements may be required where deemed necessary. Where a subdivision is transversed by a watercourse, drainageway, channel, other stream or wetland, the Board may require the provision of an easement of adequate width to conform substantially to the line of such watercourse, drainageway, channel, stream or wetland and to provide for the possibility of flood, protection of banks, future maintenance or construction and other necessary purposes.
No subdivision shall be approved which does not have adequate access to the site. The applicant shall show to the satisfaction of the Board:
A. 
Adequate vehicular access to the subdivision has been provided by a way, or ways, having sufficient width, suitable grades and adequate construction to provide for vehicular traffic and to ensure direct ingress and a rapid response time for emergency vehicles. The Board may require that secondary access be provided for reasons of public safety and convenience. Said vehicular access shall meet the Town's specifications for paved roads described in Part 5. Access roads may, at a minimum, meet the Town's specification for stabilized gravel roads (see Appendix A[1]), provided that the maximum number of lots permitted under current zoning density requirements does not exceed six lots.
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
B. 
Adequate utility access from existing utility lines to the subdivision designed to deliver underground electrical and telephone service to serve the land and buildings erected or to be erected thereon.
C. 
The legal right to pass and repass over such access way or ways and the legal right to install underground utilities in the proposed location.
A. 
Pitched shoulders shall extend four feet immediately outside the treated surface, and the slopes joining the sideline of the right-of-way to natural grade shall not be steeper than two horizontal to one vertical.
B. 
The four-foot shoulder shall be spread with four inches of loam and seeded with grass seed. The remaining area disturbed during the construction program shall be cleared of rocks, stones, or other debris and also spread with four inches of loam and seeded with grass seed. The plane of the loam on the strip between the sideline of the right-of-way and the shoulder shall be two inches above the plane of the loam and the seeded shoulder. (See Appendix A, Plate No. 5, for typical cross-section.[1])
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
Street signs conforming in design to the pattern in use by the Town and bearing the names of the intersecting streets as indicated on the definitive plan shall be installed at all intersections of streets in the subdivision. Street sign design shall be subject to the approval of the Historic District Commission. Street names shall appear on both sides of the sign if placed on a post.
[1]
Editor's Note: See also Ch. 340, Signs, § 340-28, of the Town Regulations.
Water pipes and related equipment such as hydrants, main shut-offs and laterals, including shut-offs, to serve each lot in the subdivision shall be constructed in accordance with the regulations and requirements of the Massachusetts Department of Public Health, the Nantucket Fire Department, and, where applicable, the local municipal or private water company. All water lines shall be offered for acceptance to the local municipal water company. A central water supply for more than six units must be approved by the State Department of Public Health and Public Utilities.
Dry sewer lines shall be installed to service all lots in the subdivision with laterals running to the low points of the property line. Sewer lines and related equipment shall be constructed in accordance with the following specifications:
A. 
Minimum velocity: two feet per second.
B. 
Design flow: 750 gallons per day per lot.
C. 
Tight joint pipe.
D. 
Lift stations and treatment plant to be approved by the Massachusetts Department of Public Health and the Nantucket Department of Public Works.
A. 
Power lines shall be placed underground in accordance with the rules and regulations of the Nantucket Electric Company, provided that they are no less stringent than the Massachusetts Department of Public Utilities regulations. A letter from the Nantucket Electric Company shall be submitted stating that a person qualified to do so and acting on behalf of the Nantucket Electric Company has reviewed the proposed power line installation and that said installation meets with its approval.
B. 
All lines shall be placed in conduits in all locations where these lines pass under roadway surfaces. A flag shall be erected to mark each conduit location.
A. 
All telephone lines shall be placed underground in accordance with the rules and regulations of the New England Telephone Company. A letter from the telephone company addressed to the Nantucket Planning Board shall be submitted stating that a person qualified to do so and acting on behalf of the New England Telephone Company has reviewed the proposed telephone installation and that said installation meets with its approval.
B. 
All lines shall be placed in conduits in all locations where these lines pass under roadway surfaces. A flag shall be erected to mark each conduit location.
A. 
A landscape plan shall be presented as part of each subdivision plan. This plan shall clearly show:
(1) 
The location and size of all proposed trees and other plantings; and
(2) 
The location and size of all existing trees and other vegetation on the site which are to be preserved.
B. 
The following standards shall apply:
(1) 
Existing vegetation shall be preserved wherever possible on every site. All existing trees over three-inch caliper, as well as any tree which has been flagged by the Planning Board or its designee, shall be shown on the landscape plan.
(2) 
New trees shall be planted on subdivision lots in order to provide shade, visual- and wind-screening, habitat for birds and other wildlife, and visual amenity for future residents. Planting requirements for new trees and other vegetation shall be determined according to zoning and the density of the proposed subdivision. In general, the following guidelines shall apply:
Zone
Planting Requirement
ROH, R-1, R-10, R-20, RC, RC-2, LC
One tree of 4" caliper per each proposed lot, planted in the layout or in the front or side setbacks
LUG-1
LUG-2
LUG-3
MMD
Any combination of planting of new species and preservation of existing vegetation which will demonstrate to the satisfaction of the Board that: 1) future dwellings will be suitably screened from roads and from each other; and 2) the entire subdivision, including lot and road siting and landscape plantings, has been planned with attention to the topography of the site so that the natural character of the landscape has been preserved and enhanced.
(3) 
New tree plantings shall be of a type which is resistant to breakage and is long-lived, clean, and appropriate to the local landscape and growing conditions. Guidelines for species suitable to different local conditions are found below.
(4) 
All new trees shall have a diameter of four inches or greater, and shall be planted in a good loam and peat moss mixture, and guyed, wrapped, irrigated and otherwise maintained as necessary to ensure their survival.
(5) 
The subdivider shall be responsible to ensure the survival of all new trees and plantings for a period of one year from the date of their installation. A security, in an amount deemed sufficient by the Board, shall be held by the Board and released upon its certification that the landscaping requirements, including survival of all new plantings, have been met.
Recommended Tree Species for New Plantings
d = deciduous
e = evergreen
Open Areas
d
Plane tree (Platanus occidentalis)
d
Gingko (Gingko biloba)
d
Sycamore maple (Acer pseudoplatanus)
d
Thornless honey locust (Gleditsia triacanthus)
d
Japanese pagoda tree (Sophora japonica)
d
Seedless ash (Fraxinus pennsylvatica lanceolata)
e
Red cedar (Juniperus virginiana)
e
Japanese black pine (Pinus thunbergii)
e
Pitch pine (Pinus rigida)
e
Spruce varieties (Picea sp.)
e
White fir (Abies concolor)
e
Arbor vitae (Thuja orientalis)
e
Holly (Ilex opaca)
e
Cryptomeria (Cryptomeria japonica)
e
Sawara false cypress (Chamecyparis)
Sheltered Areas
Any of the above species and, in addition:
d
Black tupelo (Nyssa sylvatica)
d
Elms (Ulmus carpinifolia, U chinensis, U americana)
d
Sweet gum (Liquidambar styraciflua)
d
Flowering ash (Fraxinus ornus)
d
Linden (Tilia americana)
d
Gray birch (Betula populifolia)
d
Washington thorn (Cratagaeus phaenopyrum)
e
Holly (Ilex opaca)
d
Crabapple (Malus sp.)
d
White poplar (Populus alba)
d
Niobe weeping willow (Salix niobe hort.)
d
Oaks (Quercus rubra, Q. alba, Q. stellata)
d
Black locust (Robinia pseudoacacia)
d
Honeylocust (Gleditsia triacanthos)
A. 
Fire alarm systems shall be required where applicable; installation and design shall be approved by the Chief or the Superintendent of Fire Alarms of the Nantucket Fire Department.
B. 
All lines shall be placed in conduits in all locations where these lines pass under roadway surfaces. A flag shall be erected to mark each conduit location.
C. 
Subdivisions not served by a public water system shall be provided with an emergency water supply system or, where a natural pond exists, a dry hydrant system, in accordance with the National Fire Code Manual, NFPA 1142, current edition, upon the recommendation of the Nantucket Fire Department. The location, installation and final testing for said systems shall be subject to the approval of the Nantucket Fire Department and shall be of a design capacity as the fire load for the development may require.
D. 
A natural pond proposed to be used as a backup source for water for fire fighting shall have adequate access to such pond to accommodate the weight and size of a fire pumper truck.
A. 
Sidewalks, having a width of not less than four feet, constructed of either brick or Portland cement concrete shall be installed on both sides of the roadway along each way in a subdivision. Sidewalks shall be constructed in accordance with the latest revision of the rules and regulations of the Massachusetts Architectural Access Board (521 CMR).
B. 
The final decision as to the requirement and type of sidewalks will be at the Board's discretion, with due consideration being given to size and number of lots in the subdivision, population density of the subdivision, and location of the subdivision in regard to walking distance to both existing and future schools, shopping districts, etc.
A. 
Bicycle paths shall be required and shall be designed as follows:
(1) 
Designed to maximize the safety of path users.
(2) 
Minimum width: eight feet.
(3) 
Materials: bituminous concrete over gravel foundation (Appendix A, Plate No. 11[1]).
[1]
Editor's Note: Appendix A is included as an attachment to this chapter.
B. 
The Board may require that bicycle paths be constructed as necessary to connect the proposed subdivision with the Town's network of major bicycle paths.
All streets shall have bituminous concrete "Cape Cod berm," vertical granite, or precast concrete curbing at the discretion of the Board, which shall be placed on both sides of all roadways. In the case where granite or precast concrete is used, the curbing shall extend along the entire circumference of curves plus six feet at all intersections from the point of tangency along the side of each roadway. The Board may waive "Cape Cod berm" in places where the road's design grade is less than 3%.
Soil surveys to establish the suitability of the land for the proposed storm and sanitary drainage installations shall be required for all subdivision submissions. Standard Massachusetts Soil Evaluator Forms shall be submitted, signed by a licensed soil evaluator. The frequency of soil samples required and types of the soil test required will be determined by the Board or its agent.
A. 
Driveway aprons of cobblestone, Belgian block, concrete, brick, or asphalt shall be provided for each lot in the subdivision. Aprons shall extend from the traveled way to two feet beyond the outer edge of any on-site sidewalk/bicycle path or two feet beyond the lot line, whichever is farther. Turning radii shall be provided at each apron's intersection with the traveled way, and apron width may not be less than 10 feet.
B. 
The Board may require that common aprons be provided for adjoining lots. The Board may modify these requirements to meet local topographical conditions.