In addition to the purposes and community development objectives discussed in Article I, the primary purposes of this article are as follows:
A.
To recognize that most of the significant undeveloped tracts within
Thornbury Township contain significant amounts of land covered by
natural resources such as floodplains, wetlands, and steep slopes.
B.
To recognize that disturbance of these natural resources may result
in negative impacts to the public health, safety and welfare by causing
greater soil erosion, siltation and sedimentation, flooding, and degradation
of water quality.
C.
To recognize that the carrying capacity of any given tract is directly
related to how great a portion of the tract consists of natural resources
and how great a portion is free of such areas.
D.
To require evaluation of potential environmental impacts associated
with subdivision and land development applications.
E.
To require protection of natural resources to the greatest extent
possible by minimizing disturbance of these areas.
F.
To require protection of natural resources which are described and/or
mapped in the Open Space, Recreation and Environmental Resources Plan
and the Comprehensive Plan.
A.
The provisions of this article shall supplement the provisions of
the underlying zoning district. In the event that the provisions of
the underlying zoning district and the provisions of this article
are in conflict, the more restrictive provisions shall apply.
B.
In the event that two or more natural resource areas identified in
this article overlap, the resource with the most restrictive standard
(the least amount of alteration, regrading, clearing, or building)
shall apply to the area of overlap.
C.
Submission, review, and approval of the following permits and applications
shall be contingent upon consistency with the requirements of this
section:
D.
Where disturbance of a natural resource is permitted, it shall not
take place until it has been determined that such disturbance is consistent
with the provisions of this article and other applicable ordinance
provisions.
E.
Restrictions to disturbance of resources shall apply whether or not
construction is proposed on a site and, where proposed, before, during,
and after the construction takes place.
Any land disturbance and/or construction proposed for any area containing a floodplain and/or floodway shall be subject to the provisions set forth under Chapter 83, Floodplain Management.
B.
Exceptional value, high quality, or impaired streams. Any watercourse
that has been designated by the Pennsylvania Department of Environmental
Protection as Exceptional Value (EV), High Quality (HQ), or impaired
shall have a protected riparian buffer extending 50 feet to either
side of the top of bank of the channel. This area shall not be disturbed,
cleared, regraded, filled, built upon or otherwise altered, except
for restoration of the riparian buffer to its natural state, including
activities such as the removal of nonnative, invasive species of vegetation,
or the replanting of appropriate species as specified by a landscape
architect or similarly qualified professional.
A.
General provisions.
(1)
For the purposes of calculating moderate slopes (15% to 25%)
and steep slopes (>=25%), the percent of slope is determined by dividing
the total amount of vertical rise or fall by the horizontal distance
over which the rise or fall occurs.
(2)
Areas of moderate and steep slope less than 500 square feet
in horizontal area shall be exempt from regulations pertaining to
moderate and steep slopes herein.
(3)
Finished driveways in steep slope areas shall cross the slope
with the least disturbance reasonably possible.
B.
Buildings and foundations shall be setback a minimum of 100 feet
from the top of any steep slope that has a grade differential from
top to bottom of at least 10 feet. There shall be no disturbance of
such slopes except under the following circumstance:
(1)
Roads necessary to provide required access to the site may cross
steep slopes if the following criteria are met:
(2)
The burden of proof to demonstrate the criteria listed in § 155-1404A(1) have been met rests solely with the applicant.
C.
Disturbance of moderate slopes.
(1)
Disturbance for building area, access, or other infrastructure
shall be limited to 60% of the total area of moderate slopes on any
given lot or tract.
(2)
Within proposed subdivisions, disturbance of moderate slopes
may be greater than 60% on individual lots, provided that there would
be no more than 60% disturbance of such slopes on the original tract
as a whole.
(3)
Disturbance of moderate slopes, to a maximum of 70%, may be
allowed if the applicant demonstrates to the satisfaction of the Township
Engineer that the result would cause less environmental degradation
(such as impacts to wetlands, riparian buffers, and woodlands) than
would result under strict adherence to the 60% standard.
D.
Disturbance of steep slopes.
(1)
No more than 10% of steep slope areas shall be altered, regraded,
cleared, built upon, or otherwise altered or disturbed. The maximum
impervious surface coverage of such area shall be 2%. Areas within
street rights-of-way, either public or private, shall be considered
as a lot for the purposes of these protection standards. Maximum disturbance
and impervious surface coverage percentages shall apply on a per lot
basis.
A.
Resource protection standards
(1)
Any applicant proposing a use, activity, or improvement which
would entail the regrading or placement of fill in wetlands shall
provide the Township with proof that the Pennsylvania Department of
Environmental Protection (Bureau of Dams and Waterway Safety and Bureau
of Water Quality Management) and the U.S. Army Corps of Engineers
have been contacted to determine the applicability of state and federal
wetland regulations.
(2)
Wetlands shall not be regraded, filled, piped, diverted, removed,
built upon, or otherwise altered or disturbed except where state and
federal permits have been obtained.
(3)
Relocated/replaced wetlands and wetland margins, when permitted,
shall be at least as large as the original wetlands, of the same composition,
within Thornbury Township, and as close to the original site as possible,
all subject to Township approval.
(4)
There shall be no building, impervious surface, or disturbance
of earth or vegetation within 100 feet of any wetland margin.
B.
Delineation. The applicant shall delineate the limits of the wetlands and lakes and ponds on the site or within 100 feet of the site in accordance with § 155-704C(1)(c). In addition, the following information shall be provided:
(1)
A full wetland report conducted by a qualified wetland biologist,
or other professional of demonstrated qualifications, shall be submitted
to the Township.
(2)
Such a professional shall certify that the methods used correctly
reflect currently accepted technical concepts, including identification
and analysis of wetland vegetation, hydric soils, and hydrologic indicators.
(3)
The wetland report shall include a determination of whether
wetlands are present on site and a full delineation, area measurement
(in square feet), and description of any wetlands determined to be
present. The study shall be approved by the Township Board of Supervisors
on the recommendation of the Township Engineer.
(4)
Where applicable, evidence that the contacts required by § 155-1405A(1) above have been made.
(5)
If no wetlands are found on the site, or within 100 feet of
the site, a note shall be added to the preliminary and final plans,
and on other applicable plans or permits, stating that, "This site
has been examined by (name and address with a statement of submitted
qualifications), and no wetlands as defined by the U.S. Army Corps
of Engineers Wetlands Delineation Manual, Technical Report Y-87-1,
January 1987, were found to exist."
(6)
The Township, at its discretion, may require a Jurisdictional
Determination from the U.S. Army Corps of Engineers.
Resource protection standards. Woodland areas and specimen trees shall be preserved to the greatest extent possible. Protected trees shall be subject to the standards set forth under Chapter 129, Trees. Disturbance of these areas shall be subject to the following restrictions:
A.
No specimen tree(s) shall be removed from any lot or tract except where the applicant demonstrates that such removal is essential to eliminate hazardous conditions or otherwise permit lawful use of the lot or tract; where permitted, removal of specimen vegetation shall be minimized. Specimen trees to be retained shall protected by the use of a tree protection zone and shall be credited toward any tree replacement required under Subsection A(4), below. Tree removal shall be limited to terminally diseased or dead trees and those trees located within the following:
(1)
The ultimate right-of-way of a proposed street or other public
improvement along with the minimum associated grading necessary.
(2)
Fifteen feet from the foundation of a proposed building or structure
and minimum associated grading necessary.
(3)
Utility easements and individual property services along with
minimum associated grading necessary.
(4)
A driveway.
(5)
Soil erosion control devices and minimum associated grading
necessary.
(6)
Stormwater management facilities and minimum associated grading
necessary.
B.
Where permitted, woodland disturbance, including the alteration or removal of any hedgerows, shall not involve more than 10,000 square feet of existing area of woodland or hedgerow on any lot or tract, without required woodland replacement in accordance with Subsection A(4), below. For purposes of this section, the extent of any area of woodland disturbance shall be measured to include the entire area within the drip line of any tree where any part of the area within the drip line of said tree is subject to woodland disturbance.
C.
Where possible, woodlands which remain undisturbed shall interconnect
with existing woodlands on adjacent properties to preserve continuous
woodland corridors and allow for the natural migration of wildlife
and the dispersion of native vegetation.
D.
Where woodland disturbance involves more than the maximum area permitted under Subsection A(2) above, tree replacement shall be required as follows:
(1)
Each tree with a diameter of eight inches or more, which is
to be removed, shall be replaced with a like-kind tree as approved
by the Township. Species of replacement plantings may be substituted
at the discretion of the Township on the basis of existing and proposed
site conditions, specific functional and design objectives of the
plantings, maintenance issues and native species/biodiversity considerations.
(2)
Replacement trees shall be planted on the site to mitigate for
the removal of existing trees and shall be in addition to other landscaping
requirements. All specimen trees to be retained on a tract shall be
credited toward any tree replacement requirement at a ratio of three
trees credited for each individual specimen tree retained.
(3)
If the site cannot accommodate the required replacement trees,
the Board of Supervisors may allow the applicant to locate some or
all of the replacement trees on public lands or accept an equivalent
fee in lieu of plantings, at the Board's discretion.
E.
Tree protection zone. In order to prevent injury to trees which have
been designated for retention, a tree protection zone shall be established.
In this zone, the following standards shall apply:
(1)
Prior to construction, trees within a designated tree protection
zone shall be clearly marked at breast height. This marking shall
be maintained until construction and other work has been completed.
(2)
During construction, trees within a tree protection zone shall
be clearly delineated with a proper barrier and signage to the limits
of the tree protection zone to ensure that there is no encroachment
and/or compaction of soil or roots within this zone by:
(3)
Sediment, retention, and detention basins shall not be located
within or discharged into a tree protection zone.
(4)
Trees which are scheduled to be removed may be left standing
adjacent to the trunks of trees within the tree protection zone to
further protect them from the limits of grading.
(5)
When roots from trees within a tree protection zone must be
trimmed as a result of disturbance outside of the tree protection
zone, they shall be cut by a backhoe or similar equipment aligned
radially to the tree. This method reduces the lateral movement of
the remaining roots, reducing the possibility of damage to the intertwined
roots of surrounding trees and other vegetation.
(6)
Trees that are to be removed shall not be felled, pushed, or
pulled into a tree protection zone.
(7)
No toxic materials shall be stored within 100 feet of a tree
protection zone, including petroleum-based and derived products.
The continuation of adequate topsoil on the land within the
Township is considered necessary for the general welfare of the Township.
The permanent removal of topsoil from the land within the Township
shall, therefore, be prohibited. This prohibition shall not be construed
to render unlawful the temporary removal of topsoil for the purpose
of construction of a building or buildings and the regrading of the
land following construction.
For any building lot that contains protected areas, the following
standards shall apply:
A.
Conventional development.
(1)
Those lots for which individual on-site sewage disposal systems
are proposed must include at least 30,000 square feet of contiguous
area that is free of any protected area and to which access can be
gained without crossing any protected area. All structures, impervious
surface and required lawn areas must be contained within this unconstrained
(free of protected area) area. The sewage system for the lot must
be completely contained within the 30,000 square foot area.
(2)
Those lots which will be connected to a community sewer must
include at least 10,000 square feet of contiguous area that is free
of any protected area and to which access can be gained without crossing
any protected area. All structures, impervious surface and required
lawn areas must be contained within this unconstrained (free of protected
area) area.
B.
Cluster development.
(1)
For development utilizing the small tract, Cluster Residential Development option (Article XII), no development may occur within protected areas. Where individual building lots are proposed, no portion of such lots may be within any protected area.
(2)
For development utilizing the large tract, Cluster Residential Development option (Article XII), disturbance to scenic lands shall be minimized to preserve the open, rural character of the Township and to maintain the quality of the existing scenic landscape. As a result, the following standards shall apply:
(a)
Moderate slopes. No more than 80% disturbance shall be permitted
to the total combined areas of moderate slopes.
(b)
Steep slopes. No more than 35% disturbance shall be permitted
to the total combined areas of steep slopes.
(c)
Woodlands. No more than 60% disturbance shall be permitted to
the total combined areas of woodland areas or specimen trees, The
Board of Supervisors may require additional landscaping or other site
improvements to mitigate any negative effects, as determined by the
Board of Supervisors, to the appearance of the site and near and distant
viewsheds. Proposed mitigation measures may include earth-form, plant
materials or other elements and shall be prepared by a landscape architect
registered by the Commonwealth of Pennsylvania.
(d)
Wetlands. No residential dwelling shall be located within 100
feet of any wetland margin. This requirement shall not supersede permits
or requirements of the Department of Environmental Protection or the
United States Army Corps of Engineers.
A.
Purpose. The purpose of this section is to protect natural and environmental
resources through the calculation of the appropriate density for development
within the Township.
B.
General standards. On any tract that contains any protected area as outlined in Article XIV, the following steps must be followed to determine the maximum allowable number of lots for any subdivision, maximum number of residential units for any residential development not involving subdivision, or maximum floor area for any nonresidential development:
(1)
Determination of developable area, protected area, and base site area. Per § 115-29 of Chapter 115, plans submitted for subdivision or land development on a tract containing any protected areas must:
(a)
Clearly identify all existing and proposed road rights-of-way
and utility rights-of-way and indicate the total area of these rights-of-way.
(b)
Subtract this total right-of-way area from the total site area
to determine base site area.
(c)
Clearly identify and delineate all protected areas by type and
indicate the area of each protected area and of the total protected
area for the site.
(d)
Calculate the percentage of the base site area represented by
the total protected area.
(2)
Determination of development factor. The development factor,
consisting of a percent credit, to be used in computing the number
of lots or dwelling units or the maximum allowable nonresidential
floor area for a protected area is derived from the following table:
|
TOTAL PROTECTED LAND
| ||||
|
Step 1
|
Enter Base Site Area (as described above)
|
_____ ac.
| ||
|
Step 2
|
Measure the acreage of all natural resources in the base site
area and enter in the Acres Measured column 2. For overlapping resources,
measure the resource with the highest resource protection ratio. Multiply
by Resource Protection Percentage for column 3 and insert result in
column 4.
| |||
|
Natural Resource
|
Acres Measured Column 2
|
Resource Protection Percentage Column 3
|
Protected Land Column 4
| |
|
Floodplain
|
1
| |||
|
Riparian buffer
|
1
| |||
|
Moderate slopes (15-25%)
|
0.4
| |||
|
Steep slopes (< 25%)
|
0.9
| |||
|
Wetland
|
1
| |||
|
Woodland
|
0.6
| |||
|
Historic
|
See Article XIII
| |||
|
Step 3
|
Sum of Step 2 column equals Protected Area
| |||
|
Step 4
|
Development Factor equals sum of Protected Land
column.
| |||
(3)
Calculation of allowed density/intensity.
(a)
Subdivision of land.
[1]
Allowed density per acre is determined by dividing
43,560 (square feet per acre) by the minimum required lot size in
the following formula:
|
43,560 ÷ (minimum lot size) = Allowed density per acre
|
[2]
Maximum allowed number of developable lots is determined
by using the following formula:
|
Developable Area (acres) x Allowed Density
|
=
|
"A"
|
|
Protected Area (acres) x Allowed Density x Development Factor
|
=
|
"B"
|
|
Maximum Allowed Number of Developable Lots (round down)
|
=
|
"A + B"
|
(b)
Residential and commercial development (no subdivision).
[1]
Maximum allowable square footage is determined
by using the following formula:
|
Developable Area (sq. ft.) x Allowed Floor Area Ratio (FAR)
|
=
|
"A"
|
|
Protected Area (sq. ft.) x Allowed FAR x Development Factor
|
=
|
"B"
|
|
Maximum Allowed Floor Area
|
=
|
"A + B"
|
(c)
Residential development (no subdivision).
[1]
Maximum allowed number of units is determined by
using the following formula:
|
Developable Area (acres) x Allowed Density (units/acre)
|
=
|
"A"
|
|
Protected Area (acres) x Allowed Density (units/acre)x Development
Factor
|
=
|
"B"
|
|
Maximum Allowed Number of Units (round down)
|
=
|
"A + B"
|
