A.
Design guidelines. All subdivisions shall be designed and improvements made by the developer consistent with the requirements of Article IV, Design and construction shall do the following:
(1)
Reduce, to the extent reasonably possible:
(a)
Volume of cut and fill.
(b)
Area over which existing vegetation will be disturbed; especially
if within 200 feet of a river, pond, or stream, or having a slope
of more than 15%.
(c)
Number of mature trees removed.
(d)
Extent of waterways altered or relocated.
(e)
Visual prominence of man-made elements not necessary for safety
or orientation.
(f)
Erosion and siltation.
(g)
Flood damage.
(h)
Number of driveways exiting onto existing streets.
(i)
Disturbance of important wildlife habitats, outstanding botanical
features, and scenic or historic environs.
(2)
Increase, to the extent reasonably possible:
(a)
Vehicular use of collector streets to avoid traffic on streets
providing house frontages.
(b)
Visual prominence of natural features of the landscape.
(c)
Legal and physical protection of views from public ways.
(d)
Street layout facilitating south orientation of houses.
(e)
Use of curvilinear street patterns.
B.
Conformance with zoning. Lots shall comply with all requirements of the Zoning Bylaw, Chapter 123 of the Code of the Town of Blackstone, as amended.
C.
Conformance with Master Plan. The street layout and utilities in
all plans shall conform to the proposals of the Blackstone Master
Plan where applicable.
D.
Referenced standards.
(1)
Standards of construction. Standards of construction for subdivision
improvements not otherwise specified hereunder shall comply with the
requirements of the MassDOT Standard Specifications for Highways and
Bridges, current edition.
(2)
Standards for analysis and design of streets. Standards for analysis
and design of streets not otherwise specified hereunder shall comply
with the requirements of the American Association of State Highway
and Transportation Officials (AASHTO), A Policy on Geometric Design
of Highways and Streets, current edition.
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.
|
Table 4-1 — Roadway Design Criteria
| ||||
|---|---|---|---|---|
|
Classification
|
Lane
|
Minor Street
|
Collector Street
| |
|
General
| ||||
|
Design speed (miles per hour)
|
20
|
30
|
40
| |
|
Posted speed or travel speed (miles per hour)
|
15
|
25
|
35
| |
|
Required stopping sight distance on level ground (feet)
|
115
|
200
|
305
| |
|
Horizontal alignment
| ||||
|
Minimum center-line radius (feet)
|
125
|
275
|
500
| |
|
Intersection rounding at edge of pavement (feet)
|
15
|
20
|
20
| |
|
Intersection rounding at right-of-way (feet)
|
N/A
|
8
|
5
| |
|
Vertical alignment
| ||||
|
Minimum center-line grade (percent)
|
1
|
1
|
1
| |
|
Maximum center-line grade (percent)
|
10
|
8
|
6
| |
|
Minimum intersection leveling area length (feet)
|
50
|
100
|
200
| |
|
Maximum intersection leveling area grade (percent)
|
3
|
2
|
2
| |
|
Minimum "K" for crest vertical curves
|
7
|
19
|
44
| |
|
Minimum "K" for sag vertical curves
|
17
|
37
|
64
| |
|
Width
| ||||
|
Minimum right-of-way width (feet)
|
50
|
50
|
60
| |
|
Minimum traveled way (pavement) width (feet)
|
20
|
26
|
30
| |
B.
Alignment.
(1)
Streets shall intersect at 90° where possible, and not less than
60° in other cases.
(2)
The minimum stopping sight distance for level road segments shall
comply with Table 4-1. For center-line downgrades steeper than 4%,
the minimum stopping sight distance shall be increased in accordance
with requirements for stopping sight distance set forth in AASHTO.
(Note: American Association of State Highway and Transportation Officials,
A Policy on Geometric Design of Highways and Streets, current edition.)
The minimum stopping sight distance shall be increased for downgrades
on lanes as follows: 117 feet for a four downgrade, 120 feet for a
six downgrade, 123 feet for an eight downgrade, and 127 feet for a
10 downgrade. The minimum stopping sight distance shall be increased
for downgrades on minor streets as follows: 208 feet for a four downgrade,
215 feet for a six downgrade, and 222 feet for an eight downgrade.
The minimum stopping sight distance shall be increased for downgrades
on collector streets as follows: 333 feet for a four downgrade and
346 feet for a six downgrade.
(3)
All intersections and approaches to intersections shall be cleared
of any obstructions to the motorist's view and maintained clear.
The edge of pavement and the right-of-way at intersections shall be
rounded based upon the minimum radii provided in Table 4-1.
(4)
The minimum center-line grade is provided in Table 4-1. The maximum
center-line grade is provided in Table 4-1.
(5)
Leveling areas shall be provided on all approaches at all intersections.
Leveling areas shall comply with the minimum intersection leveling
area lengths and with maximum intersection leveling area grades of
Table 4-1.
(6)
Vertical curves shall be provided at all changes of grade greater
than 1/2%. The minimum K value for crest vertical curves and for sag
vertical curves shall comply with Table 4-1 where K is the length
of the vertical curve in feet divided by the algebraic difference
of the intersecting grades in percent.
(7)
Sight distances at least equal to the minimum stopping sight distance of Table 4-1 and Subsection B(2) above shall be provided on all intersection approaches, 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.
(8)
Intersection sight distance triangles shall be kept clear of obstructions
on all approaches at all intersections. Intersection sight distance
triangles shall extend 25 feet perpendicular to the edge of traveled
way of the major street. Intersection sight distance triangles shall
extend along the major street for distances based upon the observed
85th percentile travel speed on the major street or the minimum design
speed for the roadway classification of the major street whichever
is greater as follows: 280 feet for 25 miles per hour, 390 feet for
35 miles per hour, 500 feet for 45 miles per hour, and 610 feet for
55 miles per hour.
(9)
Center-line offsets for intersecting streets shall not be less than
300 feet for intersections on minor streets and shall not be less
than 500 feet on collector streets.
C.
Dead-end streets.
(1)
Dead-end streets shall neither be longer than 500 feet nor shorter
than 150 feet, measured from the center of the turnaround to the sideline
of the street providing two means of access to the public street system
of the Town.
(2)
No system of dead-end streets shall have a cumulative length longer
than 500 measured along the center line of the dead-end street and
along the center lines of any dead-end streets to which it is connected
measured from the center of the most remote turn around to the sideline
of the street providing two means of access to the public street system
of the Town.
(3)
Dead-end streets whether temporary or permanent shall be provided
at the closed end with a cul-de-sac having a right-of-way diameter
of 120 feet. Culs-de-sac on minor streets shall have a pavement diameter
of 96 feet and cul-de-sac on lanes shall have a pavement diameter
of 90 feet or may have a hammerhead layout designed for a vehicle
of thirty-foot length, 8.5 feet in width, and having an outside turning
radius of 57 feet. Lots fronting on temporary cul-de-sac shall comply
with requirements of the Zoning Bylaw[1] both including and excluding land within the temporary
culs-de-sac and the lot shall comply with requirements for frontage
and lot width with the lot frontage at the required right-of-way excluding
the culs-de-sac.
(4)
Except for dead-end streets that the Planning Board determines are
permanent in nature, the subdivision plan shall provide a right-of-way
extending from the cul-de-sac on the dead end street to the subdivision
boundary. The alignment of the right-of-way shall comply with the
width and design standards for the class of street being extended
and the alignment of the right-of-way shall accommodate connection
to the nearest street, to dead-end streets on abutting properties,
to landlocked parcels, and to abutting undeveloped land.
D.
Width.
(1)
Minimum width of right-of-way and the minimum width of traveled-way
(pavement) shall comply with Table 4-1.
(2)
The center line of the paved surface shall coincide with the right-of-way
center line.
(3)
Slope easements shall be provided where the proposed back of sidewalk
grade differs from existing grade by more than five feet.
F.
Cut and fill.
(1)
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 unsuitable materials to be removed.
(2)
The proposed center-line grade shall not deviate from existing (pre-developed)
grades by more than seven feet at any point and the average of the
absolute value of the difference between the proposed center-line
grade and existing (pre-developed) grade shall not be more than four
feet for any roadway.
G.
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 a minimum depth of 15 1/2 inches below
finished grade within the traveled way, 12 1/2 inches below finished
grade for shoulders, and 10 inches below finished grade for sidewalks.
Unless a permit is granted by the Town for the removal of loam and
top soil, 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 Subdivision
Inspection Agent if the existing base is clean gravel suitable for
roadway or sidewalk foundation.
(b)
Excavation below normal depth shall be provided to remove and
replace unsuitable materials with granular backfill. Unsuitable materials
include clay, silt, organic soil, stumps, roots, and organic matter.
Granular backfill shall consist of gravel borrow (Standard Specifications
M1.03.0 Type b) and shall be placed in one-foot lifts and compacted
to not less than 95% of the maximum dry density (AASHTO Standard Method
of Test T99, Method C at optimum moisture content). Prior to placement
of the gravel base course, the entire sub-grade surface shall be compacted
to 95% of maximum dry density. After compacting, the surface shall
show no deviation in excess of two inches from the grades required
to establish the finished grades indicated on the drawings. No gravel
base course shall be placed in any sub-grade area until said area
has been inspected by the Subdivision Inspection Agent.
(3)
Placing and compacting base course materials. Gravel base course
complying with Section 405 of the Standard Specifications (M1.03.0
Type b) shall be placed in maximum lifts of six inches' compacted
depth. Each lift shall be compacted to not less than 95% of the maximum
dry density (AASHTO Standard Method of Test T99, Method C at optimum
moisture content). The gravel base course shall be placed not less
than two months prior to surfacing. All drainage and utilities are
to be installed prior to placing gravel base course. The gravel base
course, once approved, is not to be disturbed by digging without written
authorization of the Subdivision Inspection Agent.
(4)
Conditioning of base course prior to surfacing.
(a)
The surface of the base course will be inspected and tested
for tolerances by the Subdivision Inspection Agent. Any deviations
in excess of the required tolerances shall be corrected by the subdivider.
The applicant shall furnish the services of a testing laboratory to
provide gradation and compaction tests of the subgrade. As a minimum
three compaction tests plus per roadway plus one additional compaction
test for each 200 foot of roadway length shall be provided. Additional
compaction tests shall be furnished if required by the Subdivision
Inspection Agent. Any areas not meeting the minimum compaction requirements
shall be repaired. Immediately before surfacing, the base course shall
be fine-graded to 3 1/2 inches below finished grade of the traveled
way and 2 1/2 inches below finished grade of the sidewalk as
indicated on the definitive plan. Finished grade of the pavement shall
be properly marked on grade stakes set no further apart than 50 feet.
The surface of the gravel base shall show no deviation in excess of
1/4 inch from the grades indicated on the definitive plan.
(b)
The fine-graded base course shall be treated with a prime coat
of cut-back type asphalt (MC-70) applied at the rate of 4/10 gallon
per square yard.
(c)
The primed surface shall then be allowed to remain undisturbed
by traffic for a period of 48 hours, after which time it shall be
inspected by the Subdivision Inspection Agent who shall determine
whether or not a cover of screened sand will be required to blot up
the excess bitumen. Following said inspection and application of cover,
if required, the surface shall be rolled with a tandem-type roller
weighing not less than eight tons.
(d)
Immediately prior to application of the Class I Bituminous Concrete
Pavement Type I-1 (Standard Specifications M3.11.03 Top Course), the
base course shall be swept clean of all loose sand and all foreign
matter.
(5)
Pavement shall consist of Class I Bituminous Concrete Pavement, Type
I-1, which shall comply with requirements of the MassDOT Standard
Specifications (Sections 460.0 through 460.62), current edition. The
bituminous concrete pavement shall be installed in two courses, consisting
of Class I Bituminous Concrete Pavement Type I-1 (Standard Specifications
M3.11.03 Binder Course) and Class I Bituminous Concrete Pavement Type
I-1 (Standard Specifications M3.11.03 Top Course). The completed pavement
for the traveled way shall have a uniform compacted thickness of 3 1/2
inches consisting of a two-inch-thick binder course and a one-and-one-half-inch-thick
top course. The completed pavement for sidewalks shall have a uniform
compacted thickness of 2 1/2 inches consisting of a one-and-one-half-inch-thick
binder course and a one-inch-thick top course. Bituminous concrete
pavement shall not be installed between November 15 and April 15 unless
authorized in writing by the Subdivision Inspection Agent.
H.
Sidewalks.
(1)
Sidewalks five feet wide shall be provided on both sides of all streets
within the subdivision and along any frontage where the subdivision
fronts on existing public ways.
(2)
All materials shall be removed for the full width of the sidewalk
to a subgrade 10 inches below the finished grade as shown on the cross
section; and excavation below normal depth and backfill with gravel
borrow (Standard Specifications M1.03.0 Type b) shall be provided
to remove unsuitable soil. This excavated area then shall be filled
with eight inches of gravel borrow and rolled with a pitch toward
the curb of 3/8 inch per foot. Two and one-half inches of compacted
bituminous concrete shall be provided consisting of a one-inch-thick
Class I Bituminous Concrete Pavement Type I-1 (Standard Specifications
M3.11.03 Binder Course) and a one-and-one-inch Class I Bituminous
Concrete Pavement Type I-1 (Standard Specifications M3.11.03 Top Course);
provided, however, that if a granolithic surface is required by the
Board, it shall have granite aggregate and shall otherwise comply
with requirements of MassDOT Standard Specifications for Highways
and Bridges, current edition for portland cement concrete pavement.
(3)
Accessible ramps shall be provided at all street intersections, at
the termini of sidewalks, and elsewhere as appropriate in compliance
with Massachusetts Architectural Access Board requirements. Six ramps
shall be provided at "T" intersections and eight ramps shall be provided
at four-way intersections.
I.
Shoulders. Shoulders shall pitch towards the curb or swale at between
3/8 inch and two inches per foot. The shoulder shall have an eight-inch
gravel foundation, and four inches of topsoil (after rolling).
J.
Curbs. Vertical granite curbing complying with Section 504 of the
Standard Specifications (M9.04.1 Type VA4) shall be installed on both
sides of all roads in accordance with the specifications of the MassDOT
(Section 501), with a seven-inch reveal. Curb inlets shall be provided
at all catchbasins, and corner radii at all curb cuts. Curbing set
on a radius of 160 feet or less shall be cut to the curve required.
At street intersections, curbing shall be constructed to provide accessible
ramps from each sidewalk to the roadway in accordance with Massachusetts
Architectural Access Board requirements.
K.
Driveways.
(1)
Driveway locations shall be indicated on the plan and shall be constructed
contemporaneously with the subdivision street.
(2)
All driveways extending from the edge of traveled way to the lot
line must have Class I Bituminous Concrete Pavement Type I-1 (Standard
Specifications M3.11.03 Binder Course) and gravel base course complying
with Section 405 of the Standard Specifications (M1.03.0 Type b) complying
with requirements specified for pavement and base of the traveled
way. 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.
A.
General. The stormwater management system shall collect, convey,
treat, and recharge stormwater in a manner which will ensure provision
of adequate drainage for streets and lots, protection of property,
preservation of water resources, minimization of environmental impacts,
maintain unimpeded flow in watercourses, and protection of public
and environmental health by providing adequate protection against
pollution, flooding siltation and other problems caused by poor drainage.
The stormwater management system shall comply with the following:
(1)
Adhere to standard engineering practice;
(3)
Maintain pre-development drainage patterns and pre-development hydrological
conditions in groundwater and surface waters;
(4)
Include strategies for source control and best management practices
(BMPs);
(5)
Recharge runoff from pervious surfaces;
(6)
Recharge roof water in separate facilities;
(7)
Provide treatment train for the water quality volume that reduces
the contaminant burden in stormwater using best management practices
(BMPs);
(8)
Maintain or enhance surface water quality and groundwater quality;
(10)
Utilize low-impact design where practicable;
(11)
Collect and convey surface water for applicable design storms;
(12)
Avoid any increase in the peak rate or volume of stormwater
discharge at the property boundary for each storm event specified
hereinafter;
(13)
Implement an operation and maintenance (O&M) plan that complies
with DEP guidelines and ensures proper function of the stormwater
management system; and
(14)
Minimize sedimentation and erosion during construction.
B.
Design of the stormwater management system shall be prepared by a
Massachusetts registered professional engineer and all submitted plans,
calculations, and reports shall bear the engineer's signature
and seal. Deep hole observations shall be conducted under the direction
of a Massachusetts licensed soil evaluator.
C.
Submissions shall include the following:
(1)
A stormwater management report including calculations and a detailed
narrative describing pre-development and post-development conditions,
the design and function of the stormwater management system, and the
procedures and methods used for analysis.
(2)
Pre-development and post-development watershed plans showing existing
and proposed buildings, surface grades, surface treatments, catchbasins
and culverts, watercourses, watershed and catchment boundaries, flow
lines, Natural Resources Conservation Service (NRCS) soil boundaries
and hydrologic soil groups.
(3)
Pipe flow calculations based upon the Rational Formula providing
pipe diameter, inverts, slope, velocity (flowing full), length, capacity,
design flow, and v/c ratio.
(4)
Stormwater basin design calculations shall be provided based upon
TR-20.
(5)
Logs of soil borings or deep observation holes.
(6)
Soil permeability test data.
(7)
Groundwater monitoring data.
(8)
Plans showing the limits of all resource areas subject to regulation
under the WPA based upon a field survey of points established pursuant
to an order of resource area delineation or an order of conditions
issued within two years of the date of submission.
(9)
An operation and maintenance plan.
(10)
Organization documents for the party responsible for operation
and maintenance of the stormwater management system which shall include
details of the mechanism used to provide funding in perpetuity.
D.
Standards. The stormwater management system shall comply with the
standards set forth hereinafter:
(1)
Standard 1. No new stormwater conveyances (e.g., outfalls) may discharge
untreated stormwater directly to or cause erosion in wetlands or waters
of the Town of Blackstone.
(2)
Standard 2. Stormwater management systems shall be designed so that
post-development peak discharge rates do not exceed pre-development
peak discharge rates.
(3)
Standard 3. Loss of annual recharge to ground water shall be eliminated
or minimized through the use of infiltration measures including environmentally
sensitive site design, low-impact development techniques, stormwater
best management practices and good operation and maintenance. At a
minimum, the annual recharge from the post-development site shall
approximate the annual recharge from the pre-development conditions
based on soil type. This standard is met when the stormwater management
system is designed to infiltrate the required recharge volume as determined
in accordance with the Massachusetts Stormwater Handbook.
(4)
Standard 4. Stormwater management systems shall be designed to remove
80% of the average annual post-construction load of total suspended
solids (TSS). This standard is met when:
(a)
Suitable practices for source control and pollution prevention
are identified in a long-term pollution prevention plan and thereafter
are implemented and maintained;
(b)
Structural stormwater best management practices are sized to
capture the required water quality volume determined in accordance
with Massachusetts Stormwater Handbook; and
(c)
Pretreatment is provided in accordance with the Massachusetts
Stormwater Handbook.
(5)
Standard 5. For land uses with higher potential pollutant loads,
source control and pollution prevention shall be implemented in accordance
with the Massachusetts Stormwater Handbook to eliminate or reduce
the discharge of stormwater runoff from such land uses to the maximum
extent practicable. If through source control and/or pollution prevention,
all land uses with higher potential pollutant loads cannot be completely
protected from exposure to rain, snow, snow melt and stormwater runoff,
the proponent shall use the specific structural stormwater BMPs as
provided in the Massachusetts Stormwater Handbook. Stormwater discharges
from land uses with higher potential pollutant loads shall also comply
with the requirements of the Massachusetts Clean Waters Act, MGL c.
21, §§ 26 through 53, and the regulations promulgated
thereunder at 314 CMR 3.00, 314 CMR 4.00 and 314 CMR 5.00.
(6)
Standard 6. Stormwater discharges within the Zone II or interim wellhead
protection area of a public water supply and stormwater discharges
near or to any other critical area require the use of the specific
source control and pollution prevention measures and the specific
structural stormwater best management practices determined by the
Department to be suitable for managing discharges to such area as
provided in the Massachusetts Stormwater Handbook. A discharge is
near a critical area if there is a strong likelihood of a significant
impact occurring to said area, taking into account site-specific factors.
Stormwater discharges to outstanding resource waters and special resource
waters shall be removed and set back from the receiving water or wetland
and receive the highest and best practical method of treatment. A
"storm water discharge" as defined in 314 CMR 3.04(2)(a)1 or (b) to
an Outstanding Resource Water or Special Resource Water shall comply
with 314 CMR 3.00 and 314 CMR 4.00. Stormwater discharges to a Zone
I or Zone A are prohibited, unless essential to the operation of the
public water supply.
(7)
Standard 7. A redevelopment project is required to meet the following
stormwater management standards only to the maximum extent practicable:
Standard 2, Standard 3, and the pretreatment and structural stormwater
best management practice requirements of Standards 4, 5 and 6. Existing
stormwater discharges shall comply with Standard 1 only to the maximum
extent practicable. A redevelopment project shall also comply with
all other requirements of the stormwater management standards and
improve existing conditions.
(8)
Standard 8. A plan to control construction-related impacts including
erosion, sedimentation and other pollutant sources during construction
and land disturbance activities (construction period erosion, sedimentation
and pollution prevention plan) shall be developed and implemented.
(9)
Standard 9. A long-term operation and maintenance plan shall be developed
and implemented to ensure that the stormwater management system functions
as designed.
(10)
Standard 10. All illicit discharges to the stormwater management
system are prohibited.
E.
Geotechnical testing.
(1)
Deep observation hole test logs or soil boring logs shall be provided
to classify soils within proposed surface stormwater basins and subsurface
absorption systems and throughout the drainage study area. Logs of
deep observation holes or soil borings shall be provided within surface
stormwater basins and subsurface absorption systems a minimum of one
deep observation hole or soil boring log shall be provided for each
5,000 square feet of basin area or a minimum of two deep observation
hole logs per basin, whichever is greater. Deep observation hole or
soil boring logs shall extend to a depth of 10 feet below existing
grade or four feet below the design elevation of the bottom of the
stormwater basin, whichever is deeper. Additional deep observation
hole or soil boring logs shall be provided to classify soils throughout
the drainage study area, particularly in locations where available
National Resources Conservation Service mapping is indeterminate or
classifies soils as Udorthents. Deep observation hole logs shall be
prepared by a Massachusetts licensed soil evaluator and shall be witnessed
by the Subdivision Inspection Agent. Soil boring logs shall be prepared
by a qualified driller or geotechnical engineer and witnessed by Subdivision
Inspection Agent. Logs shall show soil classifications, observed groundwater,
and for deep observation holes, the estimated seasonal groundwater
through soil mottling.
(2)
Field permeability tests shall be provided within surface stormwater
basins and subsurface absorption systems. A minimum of one permeability
test shall be provided for each location. For larger surface stormwater
basins and subsurface absorption systems additional permeability tests
may be required as determined by the Board. Permeability testing in
excavations shall be conducted by a Massachusetts licensed soil evaluator
and shall be witnessed by the Subdivision Inspection Agent. Borehole
permeability tests shall be conducted by a qualified driller or geotechnical
engineer and shall be witnessed by the Subdivision Inspection Agent.
(3)
A minimum of one monitoring well shall be installed within each stormwater
basin. Monitoring wells shall extend to a depth of 10 feet below existing
grade or four feet below the design elevation of the bottom of the
stormwater basin whichever is deeper.
(4)
The elevation of groundwater shall be recorded by a Massachusetts
licensed soil evaluator, professional engineer, or professional land
surveyor once in each of three consecutive months. When observations
are taken during the months of May through December, the design groundwater
elevation shall be adjusted to reflect spring high groundwater conditions
using the Frimpter Method.
F.
Design requirements.
(1)
The drainage study area shall encompass the project site and all
tributary upgradient areas. The boundary of the drainage study area
and the analysis points shall be the same for the pre-development
condition and the post-development condition. Drainage calculations
shall be based upon full buildout of all tributary areas in accordance
with applicable zoning.
(2)
Pre-development and post-development plans of the drainage study
area shall show existing and proposed buildings, paved areas, and
surface treatment for all open areas. The plans shall show existing
and proposed elevations based upon one-foot contour intervals. The
plans shall show existing and proposed catchbasins and culverts, watercourses,
watershed and catchment boundaries, and flow lines, Natural Resources
Conservation Service (NRCS) soil boundaries and hydrologic soil groups.
(3)
Times of concentration shall be determined based upon distance, slopes,
and surface materials. A minimum time of concentration to be used
shall be 0.1 hour.
(4)
Pipe flow calculations shall be provided for the closed drain system
based upon the Rational Formula as follows:
|
Rational Formula Q = CIA
|
|
where:
| ||||
|
Q
|
=
|
Peak rate of flow
| ||
|
C
|
=
|
Coefficient of runoff
| ||
|
I
|
=
|
Rainfall intensity in inches per hour
| ||
|
A
|
=
|
Area of watershed in acres
| ||
|
A weighted coefficient of runoff "C" is to be determined for
each incremented drainage area based on the following minimum values:
|
|
Roofs and pavement
|
0.90
| |
|
Lawns
|
0.20 to 0.30
| |
|
Woodland
|
0.20
| |
|
Wetlands, ponds, basins
|
0.90
|
(5)
Inlets shall provide capacity to accommodate the design storm. Spread
shall not encroach on travel lanes of streets or the top of curbs
or berms.
(6)
Stormwater basin analysis shall be based upon Technical Release 20
(TR-20) as follows:
|
Rainfall
| ||
|
Two-year-frequency storm event – 3.2 inches
| ||
|
Ten-year-frequency storm event – 4.8 inches
| ||
|
Twenty-five-year-frequency storm event – 5.5 inches
| ||
|
Fifty-year-frequency storm event – 6.2 inches
| ||
|
One-hundred-year-frequency storm event – 6.8 inches
| ||
|
Curve number (CN)
| ||
|---|---|---|
|
Weighted curve numbers shall be calculated using the following
values. For cover types not stated, refer to TR-20.
| ||
|
Hydrologic soils group
|
A
|
B
|
C
|
D
| |
|---|---|---|---|---|---|
|
Lawns poor
|
68
|
79
|
86
|
89
| |
|
Lawns fair
|
49
|
69
|
79
|
84
| |
|
Lawns good
|
39
|
61
|
74
|
80
| |
|
Impervious areas, pavement, roofs
|
98
|
98
|
98
|
98
| |
|
Woods poor
|
45
|
66
|
77
|
83
| |
|
Woods fair
|
36
|
60
|
73
|
79
| |
|
Woods good
|
30
|
55
|
70
|
77
| |
|
Wetlands, ponds, basins
|
98
|
98
|
98
|
98
|
|
Curve numbers for conditions not included in the above shall
be obtained from TR-20 documentation.
|
(7)
Stormwater runoff shall be analyzed for the two-year-frequency storm
event, ten-year-frequency storm event, twenty-five-year-frequency
storm event, fifty-year-frequency storm event, and one-hundred-year-frequency
storm event.
(8)
The design storm for all components of the closed stormwater collection
system including catchbasin grates and other inlets, drainlines, and
the bypass capacity of separator structures is the twenty-five-year-frequency
storm event.
(9)
The design storm for cross culverts and devices protecting occupied
buildings is the one-hundred-year-frequency storm event. Streets shall
remain passable and drainage shall not enter buildings during the
one-hundred-year-frequency storm event.
(10)
The runoff for design of surfaces providing sheet flow, swales,
and drainage ditches that convey runoff to surface stormwater basins
and subsurface absorption systems is the excess runoff resulting from
storm events greater than the twenty-five-year-frequency storm event
but less than the one-hundred-year-frequency storm event.
(11)
The required recharge volume is the volume resulting from multiplying
the factors set forth below times the total post-development impervious
surface within the project area for each National Resources Conservation
Service Hydrologic Soil Group as set forth hereinafter.
|
Hydrologic Soil Group
|
Required Recharge
| |
|---|---|---|
|
HSG A Soil
|
0.60 inch of runoff
| |
|
HSG B Soil
|
0.35 inch of runoff
| |
|
HSG C Soil
|
0.25 inch of runoff
| |
|
HSG D Soil
|
0.10 inch of runoff
|
(12)
The water quality volume to be treated is 1.0 inch of runoff
multiplied by the total post-development impervious surface within
the project area for discharges to critical areas and 0.5 inch of
runoff multiplied by the total post-development impervious surface
within the project area for discharges to all other areas. Discharges
to critical areas include systems accommodating runoff from land uses
with higher potential pollutant lands, discharges to areas with infiltration
rates greater than 2.4 inches per hour, and discharges to a designated
Zone II.
G.
Stormwater collection system.
(1)
The closed stormwater collection system shall accommodate the design
storm without surcharging and shall provide a free discharge to stormwater
basins above the maximum one-hundred-year storm elevation. All components
of the system shall accommodate the design storm including catchbasin
grates and other inlets, drainlines, and the bypass components of
water quality structures.
(2)
Cross culverts and devices protecting occupied buildings shall accommodate
the design storm event without surcharging.
(3)
Surface stormwater basins and subsurface absorption systems shall
have the volume to accommodate runoff providing for no increase in
the peak rate of discharge or the volume of discharge at the project
boundary for the two-year-frequency storm event, ten-year-frequency
storm event, twenty-five-year-frequency storm event, fifty-year-frequency
storm event, and one-hundred-year-frequency storm event. Base flow
from underdrains shall be included in the design flow. Inflow volume
shall not be decreased based upon runoff captured by roofwater recharge
systems.
(4)
Surfaces providing sheet flow, swales, and drainage ditches conveying
excess runoff to surface stormwater basins and subsurface absorption
systems shall accommodate runoff from storm events exceeding the capacity
of the closed stormwater collection system but less than the one-hundred-year-frequency
storm event.
(5)
Recharge facilities accommodating runoff from paved surfaces shall
be provided over broad areas of the site and shall recharge the design
storm within 72 hours following cessation of precipitation. Separate
roofwater recharge facilities shall be provided in proximity to the
building served to promote recharge over broad areas of the site and
shall recharge the design storm within 72 hours following cessation
of precipitation. Recharge facilities accommodating runoff from paved
surfaces in combination with recharge facilities accommodating runoff
from building roofs shall accommodate the required recharge volume.
(6)
Water quality components shall be provided to remove 80% of the total
suspended solids (TSS) for the water quality volume. Water quality
components include deep catchbasin sumps, water quality structures,
and sediment forebays.
(7)
Inflows and outflows across the project boundary shall be maintained.
There shall be no concentration of flow at any point on the project
boundary nor any piped, channeled, or altered flow across the project
boundary unless a downgradient permanent drainage easement is provided
extending to an existing watercourse or wetland.
(8)
There shall be no new point source discharge within 100 feet of a
bordering vegetated wetland. Surface stormwater basins and subsurface
absorption systems shall not be located within bordering vegetated
wetlands. Stormwater basin discharges shall be above any one-hundred-year
jurisdictional flood elevation. Surface stormwater basins and subsurface
absorption systems shall not be located within floodplains unless
compensatory storage is provided.
H.
Construction requirements.
(1)
The closed stormwater collection system shall consist of precast
concrete drain manholes, precast concrete catchbasins, precast concrete
water quality structures connected by straight segments of drainline.
Catchbasin to manhole connections shall be provided.
(2)
Cross culverts shall consist of straight segments of reinforced concrete
pipe with gasketed joints.
(3)
The velocity of drainlines shall be determined based upon Manning's
equation:
|
V
|
=
|
1,486
|
R2/3
|
S1/2
| |
|---|---|---|---|---|---|
|
n
| |||||
|
where:
| ||
|
V is the cross-sectional average velocity (ft/s)
| ||
|
k is a conversion constant equal to 1.486 for US customary units
| ||
|
n is the Manning coefficient of roughness (independent of units)
| ||
|
R is the hydraulic radius (feet)
| ||
|
S is the slope of the drainline (feet/foot)
| ||
(4)
The capacity of drainlines shall be based upon the discharge formula:
|
Q = AV
| ||
|
where:
| ||
|
Q is the volume of flow in cubic feet per second
| ||
|
A is the cross section area of the pipe
| ||
|
V is the cross-sectional average velocity (ft/s)
| ||
(5)
The coefficient of roughness (Manning's n) for reinforced concrete
pipe shall be 0.013.
(6)
The minimum velocity (flowing full) for all drainlines shall be 2.5
feet per second and the maximum velocity (flowing full) shall be 12.0
feet per second flowing full. Velocities in vegetated swales shall
limit any erosion and shall not exceed five feet per second.
(7)
Drainlines shall be Class IV reinforced concrete pipe with O-ring
seal joints conforming to ASTM C443. Pipe shall have the structural
strength to accommodate depth of bury or surface loads. All drains
shall have a minimum of two feet of cover. The minimum pipe size shall
be 12 inches in diameter. In instances where pipe diameter increases,
the change shall be provided at a manhole and the crown of the inflow
pipe shall match the crown of the outflow pipe.
(8)
Catchbasins shall be four-foot inside diameter and shall have a minimum
four-foot-deep sump. Catchbasins shall be provided at intervals not
to exceed 300 feet on center. Catch basin rims shall be temporarily
set at the binder course grade, then readjusted to finish grade following
installation of the top course of pavement.
(9)
Leaching catchbasins are prohibited.
(10)
Separator structures having capacity to treat the water quality
volume shall be provided upgradient of all surface stormwater basins
and subsurface absorption systems and shall have a bypass capability
for larger storms. Separator structures shall accommodate cleaning
by a clamshell bucket. Separator structures that require cleaning
with vacuum equipment are not allowed.
(11)
All drainage structures shall accommodate AASHTO HS20-44 loadings.
(12)
Underdrains shall be provided where necessary to maintain groundwater
below the gravel base of pavement. Underdrains shall be located approximately
24 inches behind the curbline.
I.
Roofwater recharge systems.
(1)
Roofwater recharge systems, surface stormwater basins and subsurface
absorption systems shall be located in areas of permeable soil where
there is a minimum of four feet of naturally occurring permeable soil
between the bottom of the separate roofwater recharge system, surface
stormwater basin, or subsurface recharge system and impervious soils
or bedrock. A minimum separation of two feet shall be provided the
bottom of the separate roofwater recharge system, surface stormwater
basin, or subsurface recharge system and seasonal high groundwater.
(2)
Design infiltration rates for roofwater recharge systems, surface stormwater basins and subsurface absorption systems shall be either the value obtained from permeability tests of § 191-11E or the values set forth in the following table, whichever is less.
|
Table 2-1 Infiltration Rates for Various Soil Textures
| |||
|---|---|---|---|
|
Texture Class
|
NRCS Hydrologic Soils Group
|
Design Infiltration Rate
(inches/hour)
| |
|
Sand
|
A
|
8.27
| |
|
Loamy sand
|
A
|
2.41
| |
|
Sandy loam
|
B
|
1.02
| |
|
Loam
|
B
|
0.52
| |
|
Silt loam
|
C
|
0.27
| |
|
Sandy clay loam
|
C
|
0.17
| |
|
Clay loam
|
D
|
0.09
| |
|
Silty clay loam
|
D
|
0.06
| |
|
Sandy clay
|
D
|
0.05
| |
|
Silty clay
|
D
|
0.04
| |
|
Clay
|
D
|
0.02
| |
(3)
Separate roofwater recharge systems shall be provided having sufficient
volume to accommodate one inch of runoff from roofs. Roofwater recharge
systems shall be located in areas of permeable soil. Where roofwater
recharge facilities are located within hydrologic soils group (HSG)
D soils, drywells at the same elevation interconnected with equalizing
pipes or linear systems of galleys shall be used.
J.
Stormwater basins.
(1)
Surface stormwater basins including retention basins, detention basins,
and basins providing both retention and detention shall be designed
with the following objectives to be considered: hydraulic function,
safety, maintenance, aesthetics, and when required, water quality.
(2)
Surface stormwater basin(s) shall be designed for aesthetics as well
as function by proving a naturalistic freeform layout and attractive
plantings.
(3)
Surface stormwater basins may be designed as detention basins, retention
basins, or combined detention/retention basins provided that the design
requirement that there be no increase in the peak rate of stormwater
discharge and no increase in the volume of stormwater discharge at
the property line is achieved by the overall stormwater management
system. All detention basins, retention basins, or combined detention/retention
basins shall be located in areas of pervious soil and shall be designed
to empty such that the required design volume is available within
72 hours following the cessation of precipitation.
(4)
The design elevation of the bottom of the basins shall be set to
provide a minimum two-foot separation between the bottom of the basin
and spring high groundwater. A minimum of four or more feet of naturally
occurring permeable soil shall be provided between the bottom of the
basin and impervious soil or bedrock. The detention basin must be
constructed below the existing grade, and may not be constructed on
fill material.
(5)
Details of inlet and outlet control structures and the infiltration
system at the bottom of the basin shall be provided. The downstream
end of the inflow pipe and discharge pipes shall be suitably protected
against scour. The invert of the outlet control device shall be set
a minimum of 0.5 foot above the bottom of the basin and the outlet
control device shall have a trash grate or comparable device.
(6)
One foot of freeboard shall be provided above the one-hundred-year
design elevation of the basin.
(7)
An emergency spillway above the one-hundred-year design elevation
of the basin shall be provided for all basins that provides an unencumbered
hydraulic connection and directs excess flow in a manner that avoids
damage to public and private property and wetland resource areas.
(8)
Stormwater basin side slopes shall have a maximum slope of a three
horizontal to one vertical (three to one). The Board reserves the
right to limit the depth of basins to the twenty-five-year design
water surface to four feet maximum. The Board reserves the right to
require forty-eight-inch-high non-climbable fencing surrounding the
basin for safety based upon the nature of on-site and neighboring
land uses. A twelve-foot-wide gate for maintenance vehicle access
shall be provided with a key provided to the Town of Blackstone. However,
if the detention facility has slopes not exceeding one on five and
a maximum water depth of not more than 2.5 feet, an alternative barrier,
such as a hedge, may be allowed. Guardrail shall be provided for basins
in proximity to vehicular areas.
(9)
Basin embankments having a height of greater than four feet between
the required freeboard elevation and finished grade exterior to the
basin shall require geotechnical testing and an embankment design
prepared by a Massachusetts geotechnical professional engineer. Sections
through such embankments shall be provided and shall show slopes,
impervious cores, and surface armoring.
(10)
The basin side slopes and bottom shall be provided with four
inches of loam and shall have a vigorous growth of perennial turf
grass.
(11)
Infiltration systems within detention/retention basins are required
in the bottom of basins. Frames and grates shall be placed six inches
above the basin floor to allow sediment to settle.
(12)
Surface stormwater basins including surrounding maintenance
access berms shall be provided on separate lots not part of any building
lot. A fifteen-foot-wide minimum access and maintenance easement shall
extend from the public way to the stormwater basin lot.
(13)
A vehicle accessible level berm for maintenance access shall
be provided surrounding each surface retention/detention basin or
underground leaching structure. The level berm shall extend for a
minimum of 15 feet beyond the required freeboard line on the side
slope of surface retention/detention basins.
(14)
Stormwater basins shall be screened using a single row of evergreen
trees planted at 15 feet on center with either a row of evergreen
shrubs planted at six feet on center reaching a height of six feet
at maturity or a six-foot-high opaque fence. Trees shall be spruce
or fir and have a minimum height of eight feet in height at the time
of planting.
(15)
The edge of surface stormwater basins shall be measured at the
required freeboard elevation. Surface stormwater basins shall comply
with minimum setbacks as follows:
|
Property lines
|
25 feet
| |
|
Front setback
|
100 feet
| |
|
Slab on grade buildings
|
25 feet
| |
|
Building cellars or basements
|
100 feet
|
(16)
Subsurface absorption systems are limited to systems for recharge
of roofwater. Subsurface recharge systems for runoff from pavement
and landscaped areas are prohibited.
|
Inflow pipe invert shall be high enough that there will not
be substantial backwater in the pipe with the detention basin at maximum
depth.
|
K.
Mounding.
(1)
A mounding analysis is required when the vertical separation from
the bottom of an exfiltration system to seasonal high groundwater
is less than four feet and the recharge system is proposed to attenuate
the peak discharge from a ten-year or higher twenty-four-hour storm.
The mounding analysis must demonstrate that the required recharge
volume is fully dewatered within 72 hours. The mounding analysis must
also show that the groundwater mound that forms under the recharge
system will not break out above the land or increase the water elevation
in bordering vegetated wetlands, open water areas within the seventy-two-hour
evaluation period.
(2)
A mounding analysis is also required when recharge is proposed at
or adjacent to a site classified as contaminated, was capped in place,
or has an activity and use limitation (AUL) that precludes inducing
runoff to the groundwater, pursuant to MGL Chapter 21E and the Massachusetts
Contingency Plan 310 CMR 40.0000; or is a solid waste landfill pursuant
to 310 CMR 19.000; or groundwater from the recharge location flows
directly toward a solid waste landfill or 21E site. In this case,
the mounding analysis must determine whether infiltration of the required
recharge volume will cause or contribute to groundwater contamination.
(3)
The Hantush (Note: Hantush 1967 - See Reference for Standard 3.)
or other equivalent method may be used to conduct the mounding analysis;
however, the Planning Board may require use of a numeric model for
larger systems or where required to accurately model groundwater conditions.
L.
Off-site discharge.
(1)
In instances where no lots can be developed within a subdivision because no naturally occurring soils are found within the project site which would allow recharge of stormwater within 72 hours, the applicant may petition to allow off-site discharge of stormwater. The Planning Board may waive applicable requirements of § 191-11 provided that after due consideration that waiver of strict compliance with the provisions of § 191-11 is in the public interest.
(2)
Runoff may be conveyed to surface stormwater basins on contiguous
properties having sufficient capacity to attenuate the increase in
peak rate and volume. The hydrologic analysis shall establish a design
point at the outlet of the surface stormwater basins or subsurface
absorption systems. Permanent easements shall be furnished encompassing
all off-site stormwater management facilities and providing proper
access for maintenance.
(3)
Runoff may be discharged to the municipal stormdrain system provided
that the off-site connection conforms to the requirements set forth
herein. Detention basins are provided on the project site having sufficient
capacity to limit the post-development peak rate of stormwater discharge
to the municipal system such that it is no greater pre-development
peak rate of stormwater discharge to the municipal system. Any increase
in the volume of stormwater runoff discharged to the municipal storm
drain system will not cause erosion or increase flooding or ponding
of water in a manner that would damage properties or wetland resource
areas. All off-site components of the receiving municipal stormdrain
system shall have sufficient excess capacity such that they can accommodate
runoff from the project site plus all runoff from full build out of
all properties in its existing service area for the twenty-five-year-frequency
storm event without surcharging. The Board of Selectmen may allow
the connection and may as a condition of allowing the connection impose
a user fee to be paid by the applicant.
M.
Operation and maintenance plan.
(1)
A detailed operation and maintenance plan shall be provided addressing
construction phase and long-term operation and maintenance. The operation
and maintenance plan shall incorporate all applicable Massachusetts
Department of Environmental Protection standards and technical guidance.
Maintenance of the stormwater management system including pipe and
structure cleaning, and stormwater basin maintenance shall be the
responsibility of a homeowners' association or other means entailing
no expense to the Town.
A.
Installation. All components of the sanitary sewer, water distribution,
telephone, electric and CATV cable systems shall be installed underground
before roadway base course installation.
B.
Water.
(1)
Whenever feasible, the water supply shall be from a public water
supply system. In such cases, the water supply system will be considered
adequate only if it is capable of providing gravity service to each
proposed fire hydrant with a flow of 500 gallons per minute at 20
pounds per square inch residual pressure for single-family detached
residential developments, or meeting Insurance Safety Office (ISO)
requirements for other developments, and only if capable of providing
gravity service to each proposed lot with static pressure of 40 pounds
per square inch at street grade. Where any part of any lot is at elevation
300 feet above mean sea level or higher, the applicant shall submit
engineering analysis documenting adequacy.
(2)
If connection to a public water system is proposed but it is determined
by the Board that the above standards will not be met in part or all
of the subdivision for reasons beyond the reasonable responsibility
of the developer, the Board may nevertheless approve the plan subject
to a condition that any lot not adequately served shall not be built
upon until service has been made adequate or, if sooner, 24 months
have elapsed from the date of plan approval in order to allow time
to remedy system deficiencies.
(3)
Water system design, equipment, materials and construction shall
meet the specifications of the Water and Sewer Commission.
(4)
Hydrant assemblies shall comply with Figure 4-6.[1] Hydrant assemblies shall be provided at intervals not
to exceed 500 feet on center. Hydrants shall be provided at all high
points, all low points, and at the terminus of any watermain. Plans
indicating hydrant locations shall be submitted to the Fire Department
and the number and location of fire hydrants shall comply with requirements
established by the Fire Department.
[1]
Editor's Note: Figure 4-6 is included at the end of these
regulations.
(5)
Permanent dead-end water mains shall not normally be allowed. Easements
shall be provided where necessary to allow for extension or looping
of mains through subsequent development.
(6)
Where connection to an adequate public water system is infeasible,
the Planning Board shall approve a subdivision only upon its determination,
following consultation with the Fire Department, that reserved access
to a fire pond or other provisions will adequately provide for fire
safety, and upon its determination, following consultation with the
Board of Health, that wells on each lot are likely to be able to provide
a sustained yield of five gallons per minute with water quality meeting
DEP's Drinking Water Regulations of Massachusetts, as amended
from time to time. One test well may be required of the applicant
per 10 potential lots, or the Planning Board's determination
may be based upon the written statement of a hydrogeologist following
his analysis of well records on nearby premises, subsurface conditions,
and the effects of this subdivision and other potential sources of
contamination.
C.
Sewerage.
(1)
Provisions shall be made for Town sewerage to serve all lots which
potentially can be so served by gravity connections. Extension of
existing sewerage will be required at the developer's expense
to meet this requirement unless that would require greater expenditures
for facilities outside the subdivision and not abutting it than for
those within or abutting the subdivision, including house connection
or would require acquisition of easements across property of others.
(2)
Public sewers shall be at least eight inches' diameter, and
designed for a minimum flow of 2 1/2 feet per second.
(3)
Manholes shall be located at every change in grade, pipe size, or
horizontal alignment, but not more than 300 feet apart. Manholes shall
support HS20-44 loading.
D.
Cable utilities.
(1)
Conduit and structures. Underground conduit, structures, and appurtenances
shall be installed along each roadway segment for electrical, telephone,
cable television, and fire alarm systems. Electrical, telephone, cable
television service shall be provided to each subdivision lot. Underground
electrical, telephone, cable television conduits and house services
shall be installed for all lots prior to compaction of roadway or
sidewalk gravel base. Installation shall comply in all respects with
applicable regulations and codes and with utility company requirements.
(2)
Poles and any above grade structures shall comply with Planning Board
requirements. Police and fire alarm boxes shall be provide in accordance
with Police and Fire Department requirements.
(3)
Streetlighting. Streetlighting shall be installed at each intersection,
cul-de-sac, or other road hazard, with light spacing not exceeding
350 feet. The quantity, type, and location of lights within a proposed
subdivision shall be subject to Planning Board approval and shown
on the street plan. Normally fixtures shall be 8,000 lumen mercury
vapor, with 9,600 lumen sodium vapor at intersections involving collector
streets.
A.
Plantings.
(1)
Slopes outside the back of sidewalk shall be graded to meet existing
grades on contiguous lots using a slope of not more than one foot
vertical to two feet horizontal in cut sections and not more than
one foot vertical to three feet horizontal in fill sections. Slopes
exceeding 12 feet in height shall be benched. Those areas shall be
covered with at least four inches of good quality topsoil (after rolling)
and thickly seeded with drought-tolerant perennial grass mixture consisting
of at least 70% fine fescues or other planting materials approved
by the Board.
(2)
Suitable existing trees within the right-of-way, if larger than four
inches' caliper and located outside the shoulders, shall be preserved.
Trees to be retained shall not have grade changed over their root
areas more than 12 inches. Where suitable trees do not exist within
25 feet of the back of sidewalk located at intervals of less than
40 feet on center, new street trees shall be provided with a maximum
spacing of 40 feet on center.
(3)
Street trees shall be well-branched, nursery-grown stock at least
2.5 inches in caliper, and shall be free of injury, harmful insects,
and diseases. Street trees shall include the species listed in Table
4-2. Additional long-lived species adapted to the local environment
and approved by the Planning Board provided that any species listed
in the Massachusetts Department of Agricultural Resources Massachusetts
Prohibited Plant List are prohibited.
|
Table 4-2 - Street Trees
| |||
|---|---|---|---|
|
Botanical Name
|
Common Name
|
Varieties
| |
|
Aesculus octandra (flava)
|
Yellow buckeye
|
Aesculus octandra (flava)
| |
|
Aesculus x carnea
|
Red horsechestnut
|
Aesculus x carnea
| |
|
Celtis occidentalis
|
Common hackberry
|
Celtis occidentalis
| |
|
Cercidiphyllum japonicum
|
Katsuratree
|
Cercidiphyllum japonicum
| |
|
Cornus kousa
|
Japanese flowering kousa dogwood
| ||
|
Cornus x stellar
|
Stellar pink dogwood
| ||
|
Cornus x rutgan
|
Stellar pink
|
Hybrid dogwood pink
| |
|
Crataegus x lavallei
|
Lavalle hawthorn
| ||
|
Crataegus phaenopyrum
|
Washington hawthorn
| ||
|
Crataegus viridis 'Winter King'
|
Winter King hawthorn
| ||
|
Fraxinus pennsylvanica 'Marshall's Sdls.'
|
Marshall's seedless green ash
| ||
|
Ginkgo biloba 'Sentry'
|
Sentry ginkgo
| ||
|
Gleditsia triacanthos inermis
|
Thornless honeylocust
| ||
|
Gleditsia tri. in. 'Shademaster'
|
Shademaster honeylocust
| ||
|
Koelreuteria paniculata
|
Goldenrain tree
| ||
|
Liquidambar styraciflual
|
Sweetgum
| ||
|
Phellodendron amurense
|
Amur cork tree
| ||
|
Platanus x acerifolia
|
London plane tree
| ||
|
'Bloodgood'
| |||
|
Pyrus calleryana
|
Callery pear
|
'Aristocrat,'
'Chanticleer,'
'Redspire'
| |
|
Quercus coccinea
|
Scarlet oak
| ||
|
Quercus palustris
|
Pin oak
| ||
|
Quercus robur
|
English oak
| ||
|
Quercus rubra
|
Red oak
| ||
|
Sophora japonica
|
Japanese scholar tree
| ||
|
Tilia americana 'Redmond'
|
Redmond American linden
| ||
|
Tilia cordata
|
Littleleaf linden
| ||
|
Tilia tomentosa
|
Silver linden
| ||
|
Ulmus
|
Elm
|
'Homestead', 'Pioneer,' 'Urban
| |
|
Urban elm parvifolia
|
Elm,' 'parvifolia'
| ||
B.
Street signs. As soon as a street is paved, street signs conforming
to those placed by the Town shall be erected at each end of the street.
The word "Private" shall be lettered on a separate sign placed under
the street sign. This separate sign shall be removed when the street
is accepted by the Town.
C.
Monuments.
(1)
Monuments shall be installed at all street intersections; at all
points of change in direction of curvature of the streets; at each
lot corner along the street; and as necessary to locate any easements
to be deeded to the Town.
(2)
Monuments must be granite or reinforced concrete and set to a bottom
depth of not less than four feet below finished grade and with top
flush with finished grade. Reference points are to be drilled in the
top of each monument.
A.
Open space.
(1)
The Planning Board may require the plan to show a potential park
or parks suitably located for recreational purposes or for providing
light and air. The park or parks shall not be unreasonable in area
in relation to the land being subdivided and to the prospective uses
of the land, normally not exceeding 5% of plan area.
(2)
The Board may by appropriate endorsement on the plan require that
no building be erected upon such park or parks for a period of not
more than three years without its approval. This land shall be made
available for purchase by the Town. Failure to purchase within three
years shall free the owners from restrictions.
B.
Earth removal. Any area within the subdivision used for the extraction
of gravel or borrow shall be regraded, loamed, and in sod before final
release is granted by the Planning Board.
C.
Maintenance. The entire area within the right-of-way shall be properly
maintained by the developer until accepted by the Town. Immediately
prior to such acceptance, all catch basins shall be cleaned, streets
swept, and the remainder of the right-of-way and any other areas to
be deeded to the Town shall be cleared, mowed, or otherwise put in
first-class order. Snow removal and sanding of the streets shall be
the responsibility of the developer until such acceptance.
D.
Cleaning up. Before sale of a lot, the subdivider shall clean up
any debris thereon caused by construction of public improvements.
E.
Easements.
(1)
Easements for utilities across lots or centered on rear of side lot
lines shall be provided where necessary and shall be at least 20 feet
wide.
(2)
Where a subdivision is traversed by a water course, drainage way,
detention area, channel or stream, there shall be provided a storm
water easement or drainage right-of-way of adequate width to conform
substantially to the lines of such water course, drainage way, detention
area, channel or stream and to provide for construction or other necessary
purposes (such as maintenance).
F.
Protection of natural features. Due regard shall be shown for all
natural features such as large trees, water courses, scenic points,
historic spots and similar community assets, which if preserved, will
add attractiveness and value to the subdivision.
G.
Record plans. Upon completion of construction, and before release
of the performance guaranty, the subdivider shall have prepared and
submitted record plans at one equals 40 feet, which shall indicate
the actual location of all of the following:
H.
Certification. A professional civil engineer retained by the developer
shall certify that all construction was executed in conformance with
the subdivision regulations and with all requirements agreed upon
as a condition to plan approval.
I.
Village Overlay District. Within the Village Overlay District as
shown on the Zoning Map of the Blackstone zoning bylaw the following
shall be observed.
(1)
Contrary to § 191-9A(2)(e), curvilinear streets are not to be encouraged.
(2)
Pavement radii at corners may be five feet shorter than specified at § 191-10B(3).
(3)
Notwithstanding § 191-10D(1), street right-of-way and pavement widths need be no wider than that of the street from which they are accessed.
A.
Request for release. Upon completion of the foregoing requirements,
security for the performance of which was given by bond, deposit,
or covenant, or upon the performance of any covenant with respect
to any lot, the applicant may request and agree on terms of release
with said Planning Board.
B.
Completion requirements. To assist in determining whether satisfactory
completion has been made, the Planning Board shall receive a properly
completed Inspection Form (Form I) from the subdivider.[1] The required improvements will not be considered complete
until:
(2)
Grassed areas have been mown at least twice; all landscaping and
plantings have been through a winter; all other above-ground improvements
such as paving and side walks have been installed for at least 12
months subsequent to their final inspection; and all underground utilities
and appurtenances such as water and sewer lines have been installed
for at least 24 months subsequent to their final inspection. Street
acceptance by Town Meeting prior to these periods having elapsed shall
not be reason for release of the portion of security being held to
assure integrity of improvements.
[1]
Editor's Note: Form I is included at the end of these
regulations.
