The Conservation Design Overlay District is intended to provide
greater design flexibility, efficiency and options for conserving
open land and areas containing unique and sensitive natural features
and reducing the infrastructure needs of development. The district
regulations implement adopted objectives in the Upper Allen Comprehensive
Plan, as amended, and the Upper Allen Comprehensive Recreation and
Open Space Plan, as amended, including:
A. To create new residential development and neighborhoods that are
harmonious with the landscape and preserve tree cover and other important
natural amenities found within the Township.
B. To preserve natural amenities, such as streams, floodplains, wetlands
and wooded areas, and incorporate these features into development
plans to serve as open space and greenways and to provide a link to
other similar areas.
C. To work with landowners and developers to explore alternatives to
conventional residential subdivisions.
D. To preserve and enhance scenic qualities along and from major roadways.
E. To encourage the design of new development to complement the Township's
scenic and historic character.
F. To establish low- and moderate-growth land uses with cluster development
to preserve open space, promote sustainable agriculture, and protect
natural resources.
G. To promote a greenway system along stream corridors, to enhance flood
control and water quality that would interconnect with a county greenway
system, if developed, and adjoining municipality parks, to the extent
possible.
Signs shall be permitted in accordance with Article
XVIII, Signs, of this chapter.
Off-street parking and access requirements shall be provided in accordance with Article
XVII, Off-Street Parking and Loading, of this chapter.
Applicants shall use one of two methods to determine the minimum
conservation area in the case of the A District or a greenway area
for other districts; the maximum development area and the permitted
residential building density for conservation subdivisions: the adjusted
tract area approach or the yield plan approach.
A. Adjusted tract area approach. The adjusted tract area equals the
gross tract area minus the constrained land (described below).
(1)
Constrained land equals the sum of the following:
(a)
All land within the rights-of-way of existing public streets
or highways.
(b)
All land under existing private streets.
(c)
Wetlands: Multiply the acreage of designated wetlands by 0.80.
(d)
Floodway: Multiply the acreage within the floodway by 1.00.
(e)
Floodplains: Multiply the nonwetland portion of the one-hundred-year
floodplain by 0.50.
(f)
Steep slopes from 15% to 25%: Multiply the acreage of land with
natural ground slopes of 15% to 25% by 0.25.
(g)
Steep slopes greater than 25%: Multiply the acreage of land
with natural ground slopes exceeding 25% by 0.80.
(h)
Extensive rock outcroppings: Multiply the total area of rock
outcrops and boulder-fields more than 1,000 square feet by 0.90.
(i)
Scenic River Corridor: Multiply the acreage of land within the
corridor by 1.00.
(2)
If a portion of the tract is underlain by more than one natural
feature subject to a density factor, that acreage shall be subject
to the most restrictive density factor.
(3)
Since acreage that is contained within the public or private
rights-of-way, access easements or access strips is excluded from
developable lot area, any portion of these items that also contains
a natural feature subject to a deduction from the total tract acreage
should not be included when calculating the adjusted tract area.
(4)
Minimum required conservation area or greenway area. The minimum
required conservation area or greenway area equals the adjusted tract
area times the open space percentage for selected option in the underlying
district plus all constrained land.
(5)
Maximum development area. The maximum development area is the
total tract area minus the conservation or greenway area.
(6)
Permitted dwelling units. The maximum number of permitted dwelling
units equals the adjusted tract area divided by the density factor
for the selected option in the underlying district. See Table XI-1
to calculate maximum number of permitted dwellings.)
Table XI-1
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Adjusted Tract Area Calculation Worksheet
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A
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B
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C
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D
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Description of Constraint
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Area of Site Constraint
(acres)
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Multiplier
(resource protection factor)
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Constrained Lands
(acres)
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Rights-of-way of existing public streets
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1.00
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Overhead utility rights-of-way, existing or proposed
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1.00
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Land under existing private streets
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1.00
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Wetlands
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0.80
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Floodways
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1.00
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One-hundred-year floodplain (excluding floodways or wetlands
within floodplains)
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0.50
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Steep slopes from 15% to 25%
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0.25
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Steep slopes greater than 25%
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0.80
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Rock outcrops and boulder fields
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0.90
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Scenic river overlay
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1.00
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Totals
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NOTES:
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1.
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Delineate and calculate the site area of the described constraint
(see Existing Resource and Site Analysis Plan in the Upper Allen Township
Subdivision and Land Development Ordinance, Conservation Subdivision
Plat Procedures).
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2.
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Calculate total constrained land:
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•
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Insert site acreage for each factor in Column B (area of site
constraint).
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•
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Take factor acreage in Column B x Column C (resource protection
factor) to find Column D (constrained land).
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•
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Add all constrained lands in Column D to find total constrained
land.
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3.
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To calculate the Adjusted Tract Area (ATA):
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ATA = Gross Tract Area - Total Constrained Land
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4.
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Calculate permitted density:
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Permitted density = ATA/density factor
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5.
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Calculate the minimum conservation/greenway area:
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Required Conservation/Greenway Area = Total Constrained Land
+ (ATA x Open Space Percentage)
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6.
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Calculate the maximum development area:
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Maximum Development Area = Gross Tract Area - Minimum Required
Greenway Area
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B. Yield plan approach. Determination of density or maximum number of
permitted dwelling units shall be based upon the density factor of
the chosen option applied to the gross tract acreage, as demonstrated
by an actual yield plan. Yield plans shall meet the following requirements:
(1)
Yield plans must be prepared as conceptual layout plans in accordance
with the standards of the Subdivision Ordinance, containing proposed lots, streets, rights-of-way and other
pertinent features. Although it must be drawn to scale, it need not
be based on a field survey. However, it must be a realistic layout
reflecting a development pattern that could reasonably be expected
to be implemented, taking into account the presence of wetlands, floodplains,
steep slopes, existing easements or encumbrances and, if unsewered,
the suitability of soils for subsurface sewage disposal.
(2)
The yield plan must identify and demonstrate that wetlands,
floodplains, steep slopes and rock outcrops could be successfully
absorbed in the development process without disturbance by allocating
this area to proposed single-family dwelling lots.
(a)
On sites not served by central sewage disposal, density shall
be further determined by evaluating the number of homes that could
be supported by individual septic systems on conventional lots. The
applicant shall be required to provide evidence that 10% of lots at
various locations distributed throughout the tract meet the standards
for an individual septic system in order to be granted the full density
determined by the yield plan. Should any of the lots in a sample fail
to meet the standard for individual septic system, those lots shall
be deducted from the yield plan.
(b)
Yield plan dimensional standards. The following dimensional
standards shall be used in the development of yield plans for Option
1 and 2 subdivisions in the A District. The yield plan shall use the
density factor of Options 1 and 2 in the R-1 and R-2 Districts as
minimum lot area plus the standards of the underlying districts for
other dimensional requirements. These minimum dimensions are exclusive
of all wetlands, slopes greater than 25%, and land under high-tension
electrical transmission lines (69kV or greater). No more than 25%
of the minimum required lot area may consist of land within the one-hundred-year
floodplain, and only then if it is free of wetlands.
District/Option
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Lot Area
(square feet)
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Street Frontage (minimum)
(feet)
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Lot Depth
(feet)
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Agriculture District
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Option 1
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80,000
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150
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300
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Option 2
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60,000
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125
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250
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Options 1, 2, and 3 conservation subdivisions. The required
conservation area or greenway land shall be subject to permanent conservation
easements prohibiting future development other than permitted or conditional
uses.