The following supplementary studies and plans shall be reviewed
in conjunction with the review of preliminary and/or final plans.
They shall be determining factors in the acceptance or rejection of
the plans, and shall include, but not be limited to, the following
sections.
The conservation plan shall show the total tract and be clearly
and legibly drawn to the same size and scale as that of the preliminary
and final plan and shall be in the form of an overall plan.
A.
Contour lines at vertical intervals of not more than two feet.
B.
Location and elevation of the bench mark to which contour elevations
refer. Where reasonable and practical, datum used shall be USGS from
a known, established bench mark. All subdivisions and/or land developments
shall have actual field run or aerial topography.
C.
Location and ownership of all existing watercourses, floodplain areas,
wetlands, tree masses, specimen trees, soil types and other significant
natural or man-made features within the proposed subdivision and within
50 feet of the boundaries of the proposed subdivision.
[Amended 7-22-2002 by Ord. No. 2002-5]
D.
Location and results of soil percolation tests whenever on-site disposal
of sewage is planned.
E.
Location and type of all erosion and sedimentation control measures, including, but not limited to, tire cleaners, retention basins, silt fences and hay bales; proposed dates when such measures shall be in effect, and supporting data assuring compliance with the erosion and sedimentation control standards set forth in Chapter 80, Erosion, Sediment Control and Grading. A note shall be added to the plans indicating that the applicant is responsible for installation and maintenance of all soil and erosion control measures until closeout of the escrow account.
F.
Notations indicating all significant site vegetation, trees or portions
of tree masses proposed to be cleared as part of the proposed subdivision
or development plan. Notations shall be included indicating all proposed
alterations of the natural grade, whether by cut or by fill, exceeding
five feet, together with reasons for such alterations.
G.
Chapter 80, Erosion, Sediment Control and Grading, is hereby made a part of this chapter and all of its requirements are applicable to any subdivision or land development as defined in this chapter. The applicant shall take whatever measures are necessary to ensure that no silt or mud leaves the property being developed up to dedication and/or closeout of the escrow account.
The landscape plan shall show the entire tract, be clearly and
legibly drawn to the same size and scale as that of the preliminary
and final plans, shall be in the form of an overall plan and shall
include:
A.
A key map as described in § 149-602B(6).
B.
Tract boundaries and the zoning classification of all abutting properties.
C.
Floodplain areas within and adjacent to the tract.
D.
All bodies of water, waterways and drainage swales, showing the direction
of flow within the tract.
E.
All existing tree masses and specimen trees shall be noted and sufficiently
labeled.
F.
The location and type of all proposed landscaping and/or ground cover
in buffer areas, common open space and entrances shall be shown.
G.
A full plantings list showing the proper and common name along with
the size and grade shall be provided.
A.
Storm drainage. Storm drainage facilities shall be constructed by
the applicant to control runoff from street and/or any other area
that could impair public safety or cause physical damage to adjacent
lands. The facilities may consist of a storm sewer collection system,
swales and basins.
B.
The stormwater management plan shall consist of written material,
calculations and topographical plan drawn to the same scale as the
preliminary and/or final plan. The stormwater management plan shall
include, but not be limited to:
(1)
General requirements. For all subdivision and land development
proposals, a stormwater management plan and report shall be submitted
containing, but not limited to, the following:
(a)
A suitable map of the total watershed (a USGS quadrangle map
is sufficient).
(b)
Suitable maps and drawings showing all existing and proposed
drainage systems attributable to the subdivision or land development.
(c)
A plan of the proposed stormwater drainage system attributable
to the subdivision or land development.
(d)
The design computations for the stormwater drainage systems
including storm drainpipes and inlets, runoff control measures, and
culverts and drainage channels.
(e)
A plan of the grading of the subject subdivision or land development.
(f)
A plan of the erosion and sedimentation procedures to be utilized.
(g)
Notation of ownership and responsibility for maintenance of
stormwater management structures.
[Amended 7-22-2002 by Ord. No. 2002-5]
[1]
The stormwater management plan shall include a plan stating
the proposed methods and schedules of maintenance of stormwater facilities
to ensure their proper operation. The method of ownership and maintenance
responsibilities of stormwater facilities shall be subject to approval
by the Board of Supervisors.
[2]
At its discretion, the Township may require that stormwater
facilities be dedicated to the Township for maintenance. However,
the Township is under no obligation to accept dedication or maintenance
responsibilities. If the Township accepts maintenance responsibilities,
it may require the developer to fund an account to pay for ongoing
maintenance.
[3]
The Township may require that maintenance responsibilities be
handled through a property owners' association with all owners
legally obligated to fund their share of the costs.
[4]
If stormwater facilities that require proper maintenance are
to be privately owned, legal mechanisms shall be established prior
to property conveyance to require the owner and his/her successor
and assigns to properly maintain the facilities in a safe, functional
and attractive manner in accordance with the approved maintenance
schedule.
[5]
If stormwater facilities will not be municipally owned, the
developer shall establish a legal right of the Township to access
the facilities for periodic inspections and maintenance at the Township's
discretion. However, the Township is under no obligation to perform
such inspections and maintenance. The Township may require that the
entity responsible for maintenance of stormwater facilities reimburse
the Township for costs of maintenance and repair of stormwater facilities
if that entity fails to perform its duties.
(2)
Design criteria. The criteria behind the design of stormwater
management facilities is that "the peak rate of runoff after development
shall not exceed the peak rate prior to development." The stormwater
system design shall be based on the following methodology:
(a)
Design shall be by Modified Rational Method or Soil Conservation
Service (Technical Release No. 55) Urban Hydrology for Small Watersheds.
(b)
Storm sewers shall be designed to carry a storm of twenty-five-year
frequency. An overflow system shall be provided to carry flow to the
detention basin when the capacity of the storm drain pipe system is
exceeded. The overflow system shall have sufficient capacity to carry
the difference between the one-hundred-year and the twenty-five-year
peak flow rates.
(c)
Detention and retention basins shall be designed to control
the peak flow of storms of two-, five-, ten-, twenty-five-, fifty-
and one-hundred-year frequency and of twenty-four-hour duration.
(d)
Basins shall be designed to pass a storm of one-hundred-year
frequency through the outlet structure without failure of the basin
embankment.
(e)
The entire contributory drainage area shall be taken into account
in basin design.
(3)
Storm sewer system.
(a)
Storm sewer design shall meet the requirements of PennDOT 408
Standards.
[Amended 7-22-2002 by Ord. No. 2002-5]
(b)
Storm sewers shall be reinforced concrete when constructed within
rights-of-way of streets.
(c)
All inlets shall be precast concrete, PennDOT type and shall
have bicycle-safe type grater.
[Amended 7-22-2002 by Ord. No. 2002-5]
(d)
Inlets shall have a two-inch drop from inlet to outlet.
(e)
Storm sewer design shall take into account the time of concentration.
(f)
Calculations shall be provided to show the flow in the system,
pipe size, allowable flow, actual flow and velocity.
(g)
Storm sewers shall have a minimum grade of 0.5% and a minimum
inside diameter of 15 inches.
(h)
Storm sewers shall have a minimum cover of 24 inches.
(4)
Detention/retention basins. All basins shall be constructed
to include, but not be limited to, the following standards:
(a)
Berm constructed of earth of a clay base with no topsoil and
a cutoff trench key continuous along the berm base.
(b)
The top of the berm shall be a minimum of 10 feet. The sides
shall have a maximum slope of three horizontal to one vertical (3:1).
(c)
The bottom of the basin shall have a minimum slope of 2% and
any channel shall have a minimum slope of 0.5%.
(d)
The riser shall be precast concrete, box inlet or equivalent
with grate top and shall be built into the berm whenever possible.
(e)
The barrel shall be concrete pipe with anti-seep collars with
a minimum projection of two feet beyond the pipe.
(f)
Emergency spillway shall be constructed of concrete/grass pavers.
Pavers shall extend down the basin slopes at the spillway location.
[Amended 7-22-2002 by Ord. No. 2002-5]
(g)
Basin barrel outfall shall have an end wall or flared end section
with properly designed rip-rap or energy dissipators.
(5)
Retention basins shall be designed with provisions for draining
the permanent pond.
(6)
Inground retention basins/recharge systems shall be required
for all subdivisions and land developments and shall be designed to
recharge the increased volume of runoff from all additional impervious
areas for a two-year storm event. The systems shall be designed in
accordance with the following criteria:
[Amended 7-22-2002 by Ord. No. 2002-5]
(a)
A sump shall be provided between the impervious area and the
inground facility to collect and trap sediment and debris before reaching
the inground facility.
(b)
The storage volume provided by the inground facility shall be
equal to 210 cubic feet of volume per 1,000 square feet of impervious
area.
(c)
Runoff into the facility shall be evenly distributed through
a series of perforated PVC or HDPE pipes with Class 2 perforations.
(d)
The distribution pipe shall be encased in a bed of AASHTO No.
1 coarse aggregate completed envelope (top, sides and bottom) by PennDOT
Class 1 geotextile.
(e)
The facility shall be designed to completely drain within 24
hours, and percolation rates used to design the facility shall be
determined by field testing conducted in accordance with PA DEP criteria
for on-site septic system design.
(f)
The facility shall be provided with an emergency overflow device.
An operations and maintenance program shall be developed for the facility
and provided to the homeowner for implementation.
(7)
Individual berms or inground basins may be used where practical
but title plan shall contain a note that facilities are permanent
and shall be maintained by the property owner.
(8)
Landscaping; drainage channels and retention areas. All storm
drainage channels and retention areas whether existing or proposed
shall be graded and planted to effectively naturalize areas so as
to become an integral and harmonious part of the landscape by contour
and type of plant material employed.
(9)
Best Management Practices. This subsection shall apply in addition to § 149-803B(6). Where determined by the Township Engineer to be feasible considering soil conditions, the Board of Supervisors may require that a subdivision or land development include Best Management Practices to promote groundwater recharge and to minimize pollutants in runoff. These measures should take into account the manual entitled "Best Management Practices for Developing Areas in Pennsylvania" that is available through the County Conservation District. Where required, the applicant shall submit construction details of the measures. Such measures shall include, but not be limited to the following:
[Added 7-22-2002 by Ord. No. 2002-5]
The following supplementary studies, when required by the Township,
shall be reviewed in conjunction with the review of the preliminary
and/or final plans. They shall be determining factors in the acceptance
or rejection of the plans and shall include, but not be limited to,
the following:
A.
Traffic impact study. A traffic impact study shall be required for
any subdivision or land development that is expected to generate more
than 250 total average weekday trip-ends after build-out. The traffic
impact study shall include, but not be limited to, the following:
[Amended 7-22-2002 by Ord. No. 2002-5]
(3)
Existing conditions and uses of roads and intersections adjacent
to the property, accessing the property and in the vicinity of the
property.
(a)
Right-of-way widths.
(b)
Number of travel lanes.
(c)
Width of travel lanes.
(d)
Shoulder/parking lane widths.
(e)
Intersection turning movements for the peak hour of travel.
(f)
Average annual daily traffic counts.
(g)
Peak hour traffic counts (Thursday and Friday during any month
from April to November).
(4)
Calculation of capacity of all approaches to all intersections
in the vicinity of the development. It is strongly suggested that
the capacity analysis be based on the procedure established in the
1985 Highway Capacity Manual, Special Report 209, Transportation Research
Board. This standardized methodology is formulated around the following
factors:
(5)
Estimate of potential peak hour trip generation based on procedures
established in the Trip Generation Manual, Institute of Transportation
Engineers (I.T.E.), latest published edition, 1987, and shall be formulated
around the following factors:
(6)
Distribution of traffic. Assign traffic to particular access points, streets and intersections using marketing studies, work trip (origin-destination data or traffic simulation models). See also Subsection A(5) above.
(7)
Comparison of existing peak hour counts and existing capacities
of each intersection.
(8)
Comparison of existing peak hour counts plus traffic generated by the development plus assumed annual increase in traffic and existing capacities of each intersection. See also Subsection A(6) above.
(9)
Description of necessary improvements to accommodate future traffic [if Subsection A(8) above shows an unacceptable level of service].
(10)
Cost estimates.
(11)
Implementation strategy.
|
NOTE: For all capacity analyses, Westtown shall be considered
a residential area for "location within metropolitan area" and "metropolitan
area population" shall be 75,000.
|
B.
Water study. The water study shall include but not be limited to
the following, and, where applicable, plans shall be drawn to the
same scale and be of the same size as that of the corresponding preliminary
plan:
(1)
The following information shall be supplied in a combination
of drawn plans and written material for both on-site and community
system applicants:
(a)
Scope and nature of the entire proposed development, including:
[1]
Acreage of total tract and size of all individual lots and parcels.
[2]
Location of tract showing use and size of all abutting and adjacent
properties.
[3]
Intended uses of all lots, parcels and structures along with
the total number of structures and total population within the development
at the time of full build-out.
(2)
Complete description of existing conditions found within and
surrounding the proposed development, including:
(a)
Location and size of all waterways and bodies of water (including
underground within the tract and abutting and adjacent properties).
(b)
Location and size of all floodplain areas within the tract.
(c)
Topography and geology data including soil types, strata and
elevations within the tract showing a certified geologist's report
as to the expected rate and/or supply from the particular water supply
strata.
(d)
Existing water supplies, distribution and sewage treatment facilities
servicing the tract and all abutting and adjacent properties to the
tract.
(3)
Complete description of both existing and proposed fire protection facilities within the tract, and where applicable within all abutting properties. Specifications shall comply with those found in §§ 149-917 and 149-918 of this chapter and shall show:
(a)
Full plan of existing and proposed fire hydrant locations.
(b)
Source, capacity and pressure for all existing and proposed
hydrants and/or other fire protection water sources.
(c)
Proposed commercial and industrial developments shall also show:
[1]
Use and/or storage of all chemicals and other flammable materials
per structure.
[2]
Water needs other than for domestic use that would affect water
pressure needed for fire protection per structure.
[3]
Plans for and use of sprinkler systems per structure.
[4]
Effect of all proposed systems on existing systems.
(4)
The following information shall be supplied in a combination
of drawn plans and written materials, for all on-site water supply,
distribution and/or sewage facilities.
(a)
All applicable specifications cited in this chapter, and any
other ordinances of Westtown Township, shall be clearly demonstrated,
including types of materials and equipment to be used.
(b)
Plans for placement of all wells and sewage systems shall be
clearly shown for verification of safe sewage disposal.
(c)
Verification shall be shown that all wells shall be double cased,
group sealed into bedrock, at least 50 gallons per minute based on
a twenty-four-hour pump test of potable drinking water.
(5)
Verification shall be shown as to the potability and chemical
makeup of the water supply in accordance with standards set by the
Chester County Health Department.
(6)
The following information shall be supplied in a combination
of drawn plans and written material for all central water supply,
distribution and/or sewage facilities:
(a)
All applicable specifications cited in this chapter shall be
clearly demonstrated, including types of materials and equipment to
be used.
(c)
Complete description of company(ies) existing system, including
location and size of mains, storage, wells and sewage facilities in
the area.
(d)
Complete description of proposed system and facilities within
the tract.
(e)
Complete description of projected expansion of the company(ies)
services within the next five years.
(f)
Verification of monitoring and maintenance services of the company(ies)
in reference to drawdown, well(s) and storage capacity(ies).
