The proposed streets shall be considered in their relation to
existing and planned streets, topographic and geologic conditions,
public convenience and safety, and for safe vehicular travel. Due
consideration shall also be given by the developer to the attractiveness
of the street layout in order to obtain the maximum amenity of the
subdivision and to avoid excessive cut and fills. Long straight roadway
sections should be avoided. The maximum length of a straight segment
on a residential or secondary street shall be 500 feet. In addition,
the proposed streets shall provide for appropriate continuation and
connection of existing primary and secondary streets, and the extension
of primary and secondary streets onto adjoining land.
A. Location.
(1) All streets in the subdivision shall be designed so that they will
provide safe vehicular travel. Due consideration shall also be given
to the attractiveness of the street layout in order to obtain the
maximum livability and amenity of the subdivision.
(2) Streets shall be continuous and in alignment with existing streets
as far as is practicable.
(3) If adjoining property is not subdivided, proper provision for extending
streets shall be made.
(4) Reserve strips prohibiting access to streets or adjoining property
will not be permitted except where, in the opinion of the Planning
Board, such strips are in the public interest.
(5) Street intersections shall be at least 400 feet apart on collector
streets and at least 150 feet apart on other streets.
B. Alignment.
(1) Streets shall intersect at 90° where possible, and at not less
than 60° in other cases.
(2) The minimum center line radius of any curve shall be 75 feet on a
lane, 125 feet on a minor street, and 200 feet on a collector street
or where gradient exceeds 5%. The Planning Board may require a greater
radius where deemed necessary for the public safety.
(3) All intersections and approaches to intersections shall be cleared
of any obstructions to the motorist's view and maintained clear.
Street lines at intersections shall be cut back to provide for pavement
radii of not less than 30 feet if involving a collector street, or
not less than 20 feet at other intersections.
(4) Sight distances of at least 200 feet in each direction shall be provided
at intersections, except that 400 feet sight distance shall be provided
at intersections with state-numbered highways or collector streets
or other streets having high-speed traffic. At such intersections,
intersection designs shall allow for longer turning radii, and safe
acceleration and deceleration, potentially involving increased street
width, increased curb radii, and use of traffic islands for channelization.
At other locations, minimum sight distance shall be as follows:
(c)
Collector street: 275 feet.
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The Police Safety Officer shall be given an opportunity to corroborate
sight distances in the field.
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(5) Center-line offsets for intersecting streets shall not be less than
150 feet.
C. Single-access roadways.
(1) Dead-end streets shall provide access to no more than 12 potential
dwelling units, unless, in the opinion of the Board, serving a greater
number is necessitated by topography or other local conditions, and
shall be no shorter than 100 feet measured from the center of the
turnaround to the intersecting street side line.
(2) Dead-end streets shall be provided at the closed end with a cul-de-sac
as determined by the Planning Board, provided that the cul-de-sac
provides adequate turnaround for fire apparatus.
(3) Culs-de-sac.
(a)
Culs-de-sac shall not have a diameter smaller than 80 feet and
property line diameter of 100 feet, or an alternative turnaround designed
for a vehicle of thirty-foot length, eight-foot width, and having
an outside turning radius of 57 feet.
(b)
Alternate cul-de-sac designs may include one-way loop streets
with naturally vegetated islands and/or "hammerhead" turnarounds.
(c)
Culs-de-sac may have a landscaped islands to reduce impervious
surface and runoff. Landscaping should be either existing natural
materials or long-lived perennials. Small dimensional culs-de-sac
may have interior pervious materials instead of landscaped islands
as determined by the Planning Board.
D. Width.
(1) Minimum street widths shall be as follows:
Type of Street
|
Right-of-Way
(feet)
|
Pavement
(feet)
|
---|
Collector street
|
60
|
30
|
Minor street
|
50
|
26
|
Lane
|
40
|
22
|
(2) The center line of the paved surface shall normally coincide with
the right-of-way center line.
(3) The Planning Board may require slope easements where retention cannot
be adequately handled within the required right-of-way.
(4) The Planning Board may reduce the width of the right-of-way and pavement
if the applicant can demonstrate that the road can adequately accommodate
traffic, safety and stormwater management to the Planning Board's
satisfaction.
E. Grades.
(1) Grades of gutter line of all streets shall not be less than 0.5%.
Grades of center line of cul-de-sac shall not be less than 1.6% to
maintain a gutter line grade of not less than 0.5%.
(2) The maximum grades for streets shall be as follows:
Type of Street
|
Maximum Grade
(percent)
|
---|
Collector street
|
8%
|
Minor street
|
8%
|
Lane
|
8%
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(3) Grades shall not exceed 4% within 50 feet of an intersecting street.
(4) All changes in grade exceeding 2% shall be connected by vertical curves of sufficient length to afford a passing sight distance as required at Subsection
B(4), unless drainage considerations for sag vertical curves dictate otherwise.
(5) The street surface shall have a cross slope of 3/8 inch per foot
on each side of the center line or such other slope as may be determined
adequate to ensure proper drainage by the Board's engineer and/or
DPW.
(6) Center line profiles shall normally be at least three feet above
the grade of adjacent wetlands.
(7) Street grades shall be so designed that the volume of cuts and fills
made within the right-of-way approximately balance, except to offset
peat, boulders, or other unusable materials to be removed.
(8) Proposed center line grade shall not be more than seven feet above
or below the existing center line grade unless specifically authorized
by the Board in unusual circumstances.
(9) No slopes resulting from grading of streets shall exceed one foot
vertical to three feet horizontal in fill, one foot vertical to two
feet horizontal in cut, or one foot horizontal to 3/4 foot vertical
in ledge. Slope easements or retaining walls shall be used where slopes
cannot be contained within street sidelines. Driveway entrances and
land between the outside of the layout and the street pavement shall
be so graded as to prevent surface water on the street from draining
onto private land except at designated ponding areas or at appropriate
drainage easements.
(a)
Low impact development projects shall have a minimum slope of
one foot vertical to three feet horizontal, which may at the discretion
of the Planning Board be adjusted to better fit existing conditions
and/or topography.
(b)
Outside the right-of-way the slope shall be maintained at three
feet vertical to one foot horizontal.
(c)
Slopes should not create runoff into a roadway.
F. Construction.
(1) Surface preparation. Clearing and grubbing shall be performed to
remove stumps, brush, roots, boulders and like material from the area
of the traveled way, shoulders, sidewalks and utility trenches, but
elsewhere wherever feasible existing vegetation shall be preserved.
(2) Forming the subgrade.
(a)
All topsoil, subsoil, rocks, ledge and other unsuitable material
shall be excavated to pervious material (virgin soil). Unless a permit
is granted by the Town for the removal of loam and topsoil, said material
shall be stockpiled on the premises for final landscaping of roadway
shoulders and adjacent house lots. The depth of excavation may be
reduced by written authorization of the Planning Board or its agent
if the existing base is clean gravel suitable for roadway foundation.
(b)
A greater depth of excavation may be required in any area where
the subgrade material will not support the roadway, or drainage conditions
require more gravel to establish a firm foundation. Prior to placement
of the gravel base course, the entire subgrade surface shall be thoroughly
compacted by means of a three-wheel roller weighing not less than
10 tons or equivalent pneumatic tired or vibratory compactors. After
compacting, the surface shall show no deviation in excess of two inches
from the grades indicated on the drawings. No gravel base course shall
be placed in any subgrade area until said area has been inspected
and approved by the Planning Board or its agent. Any dust created
by crushing, grading or construction activity must be contained within
the property boundary.
(3) Placing and compacting base course materials.
(a)
Base course gravel shall be placed in maximum lifts of eight
inches compacted depth. Each lift is to be thoroughly compacted with
a three-wheel roller weighing not less than 10 tons, or equivalent
pneumatic tired or vibrator compactors. The final lift is to be a
finer gradation with no stones larger than three inches in diameter.
The base course gravel shall be placed not less than two months prior
to surfacing. All drainage and utilities are to be installed prior
to placing base course gravel. The base course gravel, once approved,
is not to be disturbed by digging without written authorization of
the Planning Board or its agent.
(b)
Roads shall have 95% compaction and shall be tested by an outside
soils engineer or Planning Board agent at subbase and base at two-hundred-foot
intervals.
(4) Conditioning of base course prior to surfacing.
(a)
The surface of the base course will be inspected and tested
for tolerances by the Department of Public Works or its agent. Any
deviations in excess of the required tolerances shall be corrected
by the subdivider as directed. Any ruts or soft yielding areas in
the base course shall be corrected by removing unsuitable material,
adding suitable material, reshaping and recompacting as directed.
The base course, immediately before surfacing, shall be fine-graded
to a distance below final grade equal to the total depth of hot mix
asphalt to be installed. Hot mix asphalt depths are shown on the cross
sections and the applicable cross section for each project must appear
on the definitive plan, with the grades of the street surface properly
marked on grade stakes set no further apart than 50 feet. Grading
shall be by means of a self-propelled road grader and such hand labor
as may be required. Compaction will be by an approved type roller
weighing not less than eight tons. The surface shall show no deviation
in excess of 1/4 inch from the grades indicated on the definitive
plan.
(b)
Immediately prior to application of the subsequent course of
hot mix asphalt, the prior course shall be cleaned of all loose or
foreign matter, and coated with bituminous tack coat applied in accordance
with MassDOT application rates.
(c)
Asphalt shall be inspected for thickness and temperature.
(5) Application of permanent surface.
(a)
Pavement of Class I bituminous concrete, Type I-1, shall be
placed in strict accordance with the MassDOT Highway Division Standard
Specifications for Highways and Bridges (MHDS). Said pavement shall
be laid in three courses, as shown on the cross section contained
in these regulations. If the top course is not installed within 24 hours of
the completion of the intermediate base course, an additional layer
of machine-applied tack coat shall be placed on top of the leveling
course prior to installation of the top course. Material specifications
for Class I bituminous concrete, Type I-1, appear in MHDS Material
Section M.3.11.04 Mineral Aggregate, M.3.11.05 Mineral Filler, and
M3.11.06 Bituminous Materials; construction specifications appear
in Section 460.62; tack coat material specifications for the tack
coat appear in MHDS Material Section M.3.03.3; protective seal coat
emulsion and construction specifications appear in Section 460 Class
I Bituminous Concrete, Type I-1.
(b)
No permanent surface shall be applied after November 1 unless
authorized in writing by the Planning Board or its agent, and no final
pavement shall be applied until all trenches within the proposed traveled
way have weathered one winter, and all utilities have been tested
and accepted.
(c)
If the top pavement has not been completed in a timely fashion and the base pavement has weathered, cracked or deteriorated, the base pavement shall be repaired by cutting out the unacceptable sections and installing a patch of new hot mix Type I-1 binder pavement. The hot mix pavement patch shall be installed in accordance with MHDS. All joints between patch pavement and the original base pavement shall be sealed with a material meeting MHDS Material Section M.3.03.3 Protective Seal Coat Emulsion. The joint sealing material shall be the same material that will be used as the tack coat noted in Subsection
F(5)(a) above.
G. Berms.
(1) Bituminous concrete berms or curbs shall be installed on both sides
of all roadways in conformity with the Typical Cross Section appended
hereto, except when waived by the Board where open drainage systems
are being relied upon, or where use of precast concrete or granite
is necessitated by traffic or parking conditions. The berms shall
be installed on top of the final course of pavement to ensure that
a minimum of four-inch curb reveal exists when work is completed.
Bituminous concrete curbs shall be used when sidewalks directly abut
the curb. All bituminous concrete berms and curbs must meet the MHDS
requirements and shapes.
(2) Where applicable in low impact development projects, the bituminous
concrete berm or curb may, at the discretion of the Planning Board,
be omitted and grass shoulders or filters utilized. If curbs are necessary
to stabilize the roadway edge, invisible curbs, periodic curb cuts
or perforated curbs may be used to allow stormwater to run off the
roadway edge.
H. Driveways. All driveways extending from the completed road surface
to the lot line must have a topping of at least two inches of bituminous
concrete. All driveway slopes must end at the street right-of-way,
then continue forward to the completed road surface in the same grade
as the sidewalk strip and/or shoulder in order to allow proper drainage
of surface water. At a minimum, driveway aprons will be constructed
so that the elevation of the driveway apron at the end of the street
right-of-way is six inches higher than the elevation of the roadway
pavement where the apron connects to the roadway surface.
I. Permanent private ways for up to three lots. For streets to be maintained
as private ways for up to three lots/dwelling units, the following
guidelines are applicable:
(1) Minimum sight distance: 125 feet.
(2) Minimum center line radius of curve: 75 feet.
(6) Streetlighting: not required.
J. Mailboxes. Mailbox stations shall be separated from the road by a
pull-off that is paved and can be plowed. The mailbox station must
appear in the design for the roadway layout and be within the proposed
public right-of-way or within a proposed easement.
Reasonable provisions shall be made for extension of streets
and utilities to adjoining properties, including installation of water
gates and manholes, if necessary. The developer shall not deny others
connection to the water system, drainage, or cable utilities, provided
that they pay all costs of such connection, and comply with all applicable
requirements of the Town of Bellingham.