Article IV Design Standards

The traveled way width, exclusive of curbing, shall be as specified in Figures 1, 2 and 3 and as follows:

(a)

Lane, 22 feet;

(b)

Minor street, 24 feet;

(c)

Collector street, 30 feet;

(d)

Arterial street, pursuant to MassDOT PD and DG for applicable traffic volumes and design speed.

Dead-end streets (a street, extension of a street or system of streets connected to other streets only at a single point) shall not be allowed, except for lanes, unless, in the opinion of the Board, they are necessitated by topography or other local conditions and in no event shall be more than 750 feet, measured from the end of the turnaround to the side line of the first intersecting street not a part of the dead-end street system;

Dead-end streets shall be provided at the closed end with a turnaround having dimensions conforming to AASHTO Exhibit 5-8D. Only circular offset type is allowed. A "T" style hammerhead designed in accordance with the AASHTO Green Book may be permitted by the Board in unusual circumstances, including topography, resources areas, existing or proposed buildings, etc. Either configuration shall be designed to accommodate the turning movements of the fire truck wheelbase dimensions specified by the Littleton Fire Department. Additional consideration shall be given for driveways and snow storage, both of which shall be included on the plans.

The traveled way shall be located as specified in Figures 1, 2 and 3;

The minimum width of street rights-of-way shall be as indicated in Figures 1, 2 and 3. Greater width shall be required by the Board when deemed necessary for present and future utilities or their appurtenances;

(6)

The minimum width of rights-of-way for off-street paths or easements shall be 10 feet. Greater width shall be required by the Board when deemed necessary for access or maintenance.

Horizontal and vertical alignments.

Horizontal alignment shall be designed in accordance with Section 4.2 of the MassDOT PD and DG. Minimum centerline alignment radii based on design speed using MassDOT PD and DG for non-superelevated roadways in Exhibit 4-9. If roads are proposed to be superelevated and a written waiver is granted by the Board allowing superelevation than the horizontal alignment shall be designed in accordance with the AASHTO Green Book using an allowable eMax of 6.0%. Roadway superelevation shall only be allowed by the Board in special circumstances when the use of non-superelevated curves is not feasible;

Profile grades of streets shall be not less than 1%. Grades shall be not more than 5% for collector streets, 8% for minor streets and 10% for lanes;

Vertical curves are required when there is a profile grade change of more than 1.0% between two adjacent tangents. Vertical curves shall be determined considering the existing topography, safety, and the abutting properties. The evaluation shall establish the critical abutting locations such as buildings, driveways, existing roadways and steps. Horizontal and vertical curves shall be designed concurrently to obtain safety, uniform speed, pleasing appearance and efficient traffic operations. Vertical curves shall be designed in accordance with Section 4.3.3 Vertical Curves and 4.4 Combination of Horizontal and Vertical Alignments of the MassDOT PD and DG and with the AASHTO Green Book;

*Table § 249-43.1
Design Controls for Crest Vertical Curves Based on Stopping Sight Distance
Design Speed (MPH)	Stopping Sight Distance, Req'd (feet)	Rate of Vertical Curvature, K^a
Design Speed (MPH)	Stopping Sight Distance, Req'd (feet)	Calculated	Design
15	80	+3.0	3
20	115	6.1	7
25	155	11.1	12
30	200	18.5	19
35	250	29.0	29
40	305	43.1	44

^a	Rate of vertical curvature, K, is the length of curve, per percent algebraic difference in intersecting grades (A), K=L/A
*	This table is excerpted from the 2011 AASHTO Green Book and has been provided for informational purposes only. Use the latest edition of the AASHTO Green Book for all design.

*Table § 249-43.2
Design Controls for Sag Vertical Curves
Design Speed (MPH)	Stopping Sight Distance, Req'd (feet)	Rate of Vertical Curvature, K^a
Design Speed (MPH)	Stopping Sight Distance, Req'd (feet)	Calculated	Design
15	80	9.4	10
20	115	16.5	17
25	155	25.5	26
30	200	36.4	37
35	250	49.0	49
40	305	63.4	64

^a	Rate of vertical curvature, K, is the length of curve, per percent algebraic difference in intersecting grades (A), K=L/A
*	This table is excerpted from the 2011 AASHTO Green Book and has been provided for informational purposes only. Use the latest edition of the AASHTO Green Book for all design.

Minimum stopping sight distance and intersection sight distance shall be provided in accordance with the MassDOT PD and DG and the AASHTO Green book;

All horizontal curves shall be designed to accommodate the minimum sight distances required by the AASHTO Green Book "Sight Distance on Horizontal Curves" section.

Cross section and roadside elements.

Street cross sections shall be designed in accordance with the minimum design requirements of the Typical Sections provided in the appendices for the respective street classification. See Figures 1, 2 and 3 in the appendices. Additional considerations shall be made to site specific uses and conditions, context sensitive design (see the MassDOT PD and DG) as well as Chapter 5 - Cross Sections and Roadside Elements of the MassDOT PD and DG, AASHTO Roadside Design Guide and AASHTO Green Book;

All subdivisions with 10 or more lots located in an area where school busing is provided or is likely to be provided in the future must provide at least one bituminous or cement concrete paved bus waiting area for school children located at the entrances to the subdivision or in the area where the schools determine buses will stop to pick up children who live in the subdivision.

Access control and intersections.

Intersection design shall be guided by Chapter 6 - Intersection Design of the MassDOT PD and DG and pertinent AASHTO and ITE guidelines;

All streets and paths in the subdivision shall be designed so that, in the opinion of the Board, they will provide safe pedestrian and vehicular travel. Due consideration shall also be given to the consequences of the street layout upon the livability, amenity and environmental impact of the subdivision;

Provision satisfactory to the Board shall be made for the proper projection of streets or paths 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 are in the public interest;

New street intersections shall be at least 300 feet apart;

(6)

Street configuration shall be designed, together with reserved open space, to minimize the number of lots having frontage exclusively on collector streets;

(7)

Streets shall be laid out so as to intersect as nearly as possible at right angles. No street shall intersect any other street at less than 60°;

(8)

Any group of 20 or more lots shall be provided with two means of egress;

(9)

Property lines at street intersections shall be rounded or cut back to provide for a radius at the edge of the traveled way of not less than 30 feet at intersections with a collector street and 20 feet for intersections involving only minor streets or lanes;

(10)

Street intersections on all Collector and Arterial Streets, including but not limited to Great Road, King Street, Newtown Road, Shaker Lane, Goldsmith Street, Tahattawan Road, Harvard Road, Harwood Avenue, Foster Street, Taylor Street, and Whitcomb Avenue, shall be spaced not less than 400 feet apart. Refer to the MassDOT Road Inventory for the most current classification of roadways within the Town;

(11)

Pathways connecting existing trails and paths should be preserved or created wherever reasonable, not necessarily following the streets, and should be developed in other locations where indicated by traffic, access to public or recreational facilities or other reasons;

(12)

The nearest line of any driveway shall not be closer than 50 feet from the intersection of any two streets;

(13)

All intersections shall be designed with the minimum sight distances as defined by the AASHTO Green Book for Stopping Sight Distance and Intersection Sight Distance;

(14)

The vertical alignment of all intersection approaches shall be designed in accordance with Table 43.3 and the associated Figure below.

*Table § 249-43.3
Vertical Alignment Design Controls at Intersections
Design Speed (mph)	Maximum Intersection Grade (GI, %)	Maximum Grade Break (GB, %)	Minimum Length of Approach Grade (GA, feet)
15	5	6	20
20	5	5	40
25	5	4	40
30	5	3	60
35	5	2	60
40	4	2	70

*	This table has been excerpted from the 2006 MassDOT Project Development and Design Guide and has been provided for information purposes only. Use the latest edition of the MassDOT PD and DG for all design.

Figure § 249-43.1

Vertical Alignment Design Controls at Intersections

249 Vertical Alignment Design Controls.tif

Landscaping and aesthetics.

Cul-de-sac center islands shall be landscaped. Eight feet width of gravel is required on the perimeter of the cul-de-sac, inside the curb. Low-maintenance groundcover (juniper or similar) shall be planted with topsoil and bark mulch, with trees screening any transformers or electrical equipment. Do not obstruct access;

Maintenance of cul-de-sac inner island shall be the responsibility of the developer, its successors and assigns or a homeowners association;

Street trees shall be required to be planted, at the Applicant's expense, on all streets within the tract to be subdivided. Trees shall be planted on both sides of the street and shall be spaced at intervals of 40 feet on center, unless waived by the Board;

Street trees shall not be permitted within 25 feet of the curb line of the intersection of two streets;

§ 249-44 through § 249-46. (Reserved)

Street tree locations shall be coordinated with all existing and proposed below grade and above grade utilities to avoid current or future conflicts and shall address tree growth and canopy sizes;

(6)

The center of trees shall be a minimum of four feet from edge of pavement and curbs;

(7)

Mature existing trees shall be retained and protected whenever possible. The Applicant may be required to plant trees just where necessary, in view of existing vegetation. Before the trees are planted, a plan showing their proposed location and species shall be submitted to the Planning Board for approval. Adequate sight distances shall be provided and considered when selecting and planting trees and other landscaping. Adequate clearance shall be provided from sidewalks, utilities, overhead wires, etc.;

(8)

Street trees shall be single-stemmed with a single, straight leader. All tree species must meet American Nursery and Landscape Association (ANLA, formerly American Association of Nurserymen Standards) for the types and sizes specified. These standards shall be included on the detail sheets. The species of street trees selected shall be of Zone 6 hardiness and shall be of licensed nursery stock. Existing trees may be preserved as street trees if inspected and approved by the Tree Warden. The Applicant shall seek the advice of the Shade Tree Committee for location and species of tree. Street trees shall be deciduous shade trees. No more than 35% of any one species shall be used throughout the subdivision;

(9)

The minimum size of street trees shall be three inches in caliper, measured four feet from the ground level, and 10 feet in height, in place. Trees to be retained shall not have grade changed over their root areas more than six inches. Street trees shall be clear of stems or branches to a minimum height of six feet;

(10)

The top six inches of tree belt shall consist of good quality loam extending to the right-of-way, screened, raked, and rolled with lawn grass seed applied in sufficient quantity to assure adequate coverage, rolled when the loam is moist;

(11)

Street shade trees shall be on both sides of subdivision streets in the tree belt or within five feet of the right-of-way;

(12)

Clumping or clustering is permitted, using both sides of the sidewalk for tree planting, in order to frame or enhance a view;

(13)

All maintenance of trees outside the right-of-way shall be the responsibility of the property owner;

(14)

The developer shall install the street trees specified on the approved plans prior to the issuance of the final Certificate of Occupancy. Trees shall be guaranteed for two years after acceptance of the road as a public way or, in the case of private ways, after release from subdivision control;

(15)

Planting operations and requirements for street trees shall be shown on the subdivision plans and be in accordance with the ANLA Standards for Planting;

(16)

All unpaved areas within the street layout shall be stabilized with retained vegetation, topsoil and grass, well-rooted low-growing plantings or other organic materials acceptable to the Board.

§ 249-47 Easements.

Utility easements for utilities across lots or centered on rear or side lot lines shall be provided where necessary and shall be at least 20 feet wide.

Where a subdivision is traversed by a watercourse, drainageway, channel or stream, the Board may require that there be provided a stormwater or drainage easement with a width of 20 feet or the width of the watercourse plus 10 feet whichever is greater, to conform substantially to the lines of such watercourse, drainageway, channel or stream and provisions for construction or other necessary purposes.

When in the design of a surface water drainage system, the outlet discharges water that has been collected within the confines of the subdivision in a concentrated stream onto land of others, and this land being located beyond the external boundaries of the subdivision to within reasonable proximity of the subdivision, the Applicant shall be required to obtain an easement, suitable for recording, which would legally allow such surface drainage to flow onto or over such land of others. Proof of such easement shall be provided to the Board. The easement shall be obtained at the Applicant's expense.

Slope easements shall be provided where cut or fill slopes cannot be contained within the street right-of-way.

§ 249-48 through § 249-50. (Reserved)

§ 249-51 Stormwater management.

Stormwater management shall be designed and implemented in conformance with the Stormwater Management Handbook as established by the latest Massachusetts Department of Environmental Protection, as amended except as noted otherwise below. Storm drainage, culverts and related facilities shall be designed to permit the unimpeded flow of all natural watercourses, to ensure adequate drainage of all low points along streets, to control erosion and to intercept stormwater runoff along streets at intervals reasonably related to the extent and grade of the area drained.

It is the intent of these regulations that stormwater shall be recharged wherever recharge is environmentally preferable to discharging to surface water and feasible from an engineering standpoint. If discharge to surface water is used, the developer will be required to demonstrate that one of these conditions is not met. It is recommended that the developer consult with the Planning Board and with the Littleton Water Department before designing a surface discharge system.

All detention or retention structures shall be designed on the basis of the one-hundred-year frequency storm as defined by SCS TR55. Culverts shall be designed on the basis of the fifty-year frequency storm as defined by SCS TR55. Storm sewers shall be designed on the basis of the ten-year frequency storm as defined by SCS TR55.

A catch-basin-to-manhole system of drainage is required with catch basins located on both sides of the roadway at all low points, sags and near the upstream corners of the roadway at intersecting streets. Additional manholes shall be installed at all changes in pipe slope and alignment. Stormwater runoff in street gutters shall not be permitted to flow upon the surface for a distance longer than 300 feet before it enters the underground catch-basin-to-manhole system. In no instances shall catch basins be located along a driveway or sidewalk ramp cut. Catch basins shall not be directly connected to one another but shall rather be manifolded into drain manholes. Roads shall be graded so that surface water does not cross the roadway. An inlet analysis shall be provided demonstrating that gutterline spreads at all inlets meet the requirements of the MassDOT PD and DG. In no case shall the gutterline spread exceed half of the travel lane.

Grading and drainage system design shall protect adjacent properties, drainage facilities and public ways from adverse effects, or, where that is infeasible, the subdivider shall obtain necessary easements and rights, prior to submittal of the Definitive Plan, and the plan shall show necessary off-site improvements.

Runoff calculations shall be performed in accordance with SCS TR55 or TR20, using SCS Type III rainfall distribution, unless prior approval for deviations from these procedures has been obtained from the Planning Board. Such approval will be granted if the engineer satisfies the Board that the nature of the subdivision makes the SCS methods impractical and that the alternate method is of equal or greater reliability. Peak runoff rates shall be estimated for every subcatchment, reach and detention pond provided for the two-, ten-, twenty-five-, fifty- and one-hundred-year frequency storms. The drainage system shall be designed such that there is no increase in the peak rates and total volume of runoff from any of the watershed areas at the discharge point(s) from the site for any of the modeled storms. At drainage discharge points, provision shall be made for velocity reduction using appropriate technologies so as to prevent erosion at the point of discharge and down gradient.

All drainage calculations shall be performed in accordance with Chapter 8 - Drainage and Erosion Control of the MassDOT PD and DG. Drain pipes shall have a minimum inside diameter of 12 inches and shall be constructed of reinforced concrete pipe or ductile iron pipe. In general, pipes shall be designed to flow full with the hydraulic gradient at the crown and minimum pipe velocities of two feet/s and maximum velocities of nine feet/s. A hydraulic grade line analysis shall be performed and provided to the board for review. The analysis shall include a plan of the watershed drainage areas with each area labeled to include number, area, runoff curve number (CN) and time of concentration. In addition, discharge points, topography, existing streams, water bodies and detention basins shall be identified on the plan.

At detention basins and retention basins, the maintenance berm shall be designed in accordance with the Massachusetts Stormwater Handbook, latest edition. The maintenance berm shall be flat and at least 15 feet in width. Detention basins and retention basins shall be designed to control the one-hundred-year frequency storm event and shall comply with the requirements established by the Massachusetts Department of Environmental Protection, as amended. The pipe inlets discharging into the basin shall be at or above the twenty-five-year storm event ponding elevation. Detention basins constructed by berming shall be designed and constructed as a dam. Banks shall be stabilized to prevent seepage. Detention basins shall be designed so that the maximum depth, including freeboard shall not exceed eight feet. A minimum thirty-foot setback as measured from the top of the inside slope to all property lines shall be required.

In situations where development interrupts existing stormwater runoff of a drainage course, the site drainage shall be designed to accommodate the flows and volumes from these sources. In the case of interrupted streams, the site design shall incorporate provisions to reroute flow around the development and back to the existing stream bed prior to flows leaving the property.

Street drainage shall not be channeled into a wetland or water body without first being treated by one or more treatment Best Management Practices (BMPs).

§ 249-52 Erosion and sediment control.

In order to reduce erosion accompanying the installation of ways, utilities and drainage systems, a sediment control plan shall be prepared and implemented. The plan shall comply with the requirements of Chapter 8 - Drainage and Erosion Control of the MassDOT PD and DG and the National Pollution Discharge Elimination System (NPDES) Construction General Permit.

Land shall be developed in increments of workable size which can be completed during a single construction season. Erosion and sediment control measures shall be coordinated with the sequence of grading, development and construction operations. Control measures such as hydroseeding, berms, interceptor ditches, mulching, temporary sodding, terraces, and sediment traps shall be put into effect prior to the commencement of each increment of the development/construction process.

Vegetative cover and runoff characteristics shall be maintained as close as possible to conditions before development by reducing cut and fill and other considerations.

Water resources shall be protected, including but not limited to floodplains, wetlands, aquifer recharge areas, and Town well fields.

Sediment basins (debris basins, desilting basins, or silt traps) shall be installed in conjunction with the initial grading operations and maintained through the development process to remove sediment from runoff waters draining from land undergoing development.

A note on the Erosion Prevention and Sedimentation Control Plan shall state that the Applicant is required to clean up any sand, dirt, or debris which erodes from the subdivision onto any public street or private property, and to remove silt or debris that enters any existing drainage system including catch basin sumps, pipelines, manholes and ditches within 24 hours of being noted by the Town.

Hay bales or Board approved equivalent must be used around the catch basins on the proposed streets to protect them from the eroding soils and provide a check dam to slow runoff during construction.

§ 249-53 through § 249-54. (Reserved)

§ 249-55 Water supply and sewage disposal.

Provisions shall be made for water supply for domestic use and sewage disposal for each lot and for fire protection. Whenever feasible, the water supply shall be from a public water system, in which event the system design shall be satisfactory to the Water Department, evidenced by certification from the Water Department that they approve the design and will permit connection.

Where connection to the public water supply system is not feasible, a subdivision plan shall be approved only upon presentation of evidence satisfactory to the Board, that adequate and suitable groundwater is available and that satisfactory provisions for firefighting acceptable to the Fire Department have been provided.

§ 249-56 through § 249-58. (Reserved)

§ 249-59 Other requirements.

Underground wiring. All wiring, appurtenances of electric power, telephone, cable and fire alarm systems, and other utilities shall be placed underground within the limits of the street right-of-way, except where such underground installation would, in the judgment of the Planning Board, cause undue hardship by reason of topography, subsoil conditions or other site peculiarities or by reason of the existing development pattern.

Other provisions. The developer shall make provisions for the installation of their cables or pipes, during the construction of the roadway by all public utilities (including but not limited to gas, telephone and cable television) serving the Town, unless he/she has received from the utility a signed statement that it does not wish to serve the subdivision and furnished a copy of same to the Board. Notwithstanding such a statement, the developer shall install conduit for future use for cable television.

Written approvals. No Definitive Plan will be approved unless the developer submits written certification of approval of the design by all utilities which are to provide services within the subdivision.

Open spaces. Before approval of a plan, the Planning Board may require that an area be reserved for a possible park or parks and, by appropriate endorsement on the plan, require that no building be erected upon such reserved area without the Board's approval for a period of three years. Such reservation shall be made where particular natural features, abutting public land or the potential neighborhood need for recreation space make later public acquisition appear desirable.

Protection of natural features. Due regard shall be shown for all natural features, such as large trees, watercourses, scenic points, historic spots, existing trails, and similar community assets, which, if preserved, will add attractiveness and value to the subdivision.

Emergency access roads. Emergency access roads shall have a minimum twenty-foot right-or-way, a minimum ten-foot wide paved surface, three foot soft/gravel shoulders, and posts or gates installed at all entrances. Gates must be secured with a Fire Department approved locking system. Emergency access ways do not provide frontage.

Construction management plans. Construction management plans shall ensure and protect the safety of both the public and workers throughout construction. The construction management plans shall include traffic management plans, proposed truck routes and proposed hours of construction operations.

Traffic Management Plans shall be designed in accordance with MUTCD. The plans shall show all construction entrances, advanced construction signage, typical details for proposed lane shifts/closures in accordance with MUTCD and state and local regulation. A more detailed plan showing lane shifts or closures may be required if deemed necessary by the board. If detours are required, all detour routes and associated signage shall be shown in accordance with MUTCD and are subject to approval by the Fire Department and Police Department.

The truck route provided shall show the proposed truck route from the nearest freeway access to all proposed construction entrances. Truck routes shall minimize impacts to local roads, schools, parks, residents and abutters.