As used in this chapter, the following terms shall have the
meanings indicated:
AGRICULTURAL ACTIVITY
Activities associated with agriculture such as agricultural
cultivation, agricultural operation, and animal heavy use areas. This
includes the work of producing crops including tillage, plowing, disking,
harrowing, planting or harvesting crops; or pasturing and raising
of livestock; and installation of conservation measures. Construction
of new buildings or impervious area is not considered an agricultural
activity.
APPLICANT
A landowner, developer, or other person who has filed an
application to the Township for approval to engage in any regulated
activity as defined in this chapter.
AS-BUILT PLANS (DRAWINGS)
Engineering or site plans or drawings that document the actual locations, dimensions and elevations of the improvements, and building components, and changes made to the original design plans. The final version of these documents, or a copy of same, are signed and sealed by a qualified licensed professional and submitted to the Township at the completion of the project, as per the requirements of §
270-34I of this chapter as "final as-built plans."
BANKFULL
The channel at the top-of-bank or point from where water
begins to overflow onto a floodplain.
BASEFLOW
Portion of stream discharge derived from groundwater; the
sustained discharge that does not result from direct runoff or from
water diversions, reservoir releases, piped discharges, or other human
activities.
BMP (BEST MANAGEMENT PRACTICE)
Activities, facilities, designs, measures, or procedures
used to manage stormwater impacts from regulated activities, to provide
water quality treatment, infiltration, volume reduction, and/or peak
rate control, to promote groundwater recharge, and to otherwise meet
the purposes of this chapter. Stormwater BMPs are commonly grouped
into one of two broad categories or measures: "structural" or "nonstructural."
In this chapter, nonstructural BMPs or measures include certain low-impact
development and conservation design practices used to minimize the
contact of pollutants with stormwater runoff. These practices aim
to limit the total volume of stormwater runoff and manage stormwater
at its source by techniques such as protecting natural systems and
incorporating existing landscape features. Nonstructural BMPs include,
but are not limited to, the protection of sensitive and special value
features such as wetlands and riparian areas, the preservation of
open space while clustering and concentrating development, the reduction
of impervious cover, and the disconnection of rooftops from storm
sewers. Structural BMPs are those that consist of a physical system
that is designed and engineered to capture and treat stormwater runoff.
Structural BMPs include, but are not limited to, a wide variety of
practices and devices from large-scale retention ponds and constructed
wetlands to small-scale underground treatment systems, infiltration
facilities, filter strips, bioretention, wet ponds, permeable paving,
grassed swales, riparian buffer, sand filters, detention basins, and
manufactured devices. Structural and nonstructural stormwater BMPs
are permanent appurtenances to the site. [See also "stormwater management
facility" and "stormwater control measure (SCM)."]
BOARD
The Board of Supervisors of West Whiteland Township.
CFS
Cubic feet per second.
CHANNEL
A natural or artificial open drainage feature that conveys,
continuously or periodically, flowing water and through which stormwater
flows. Channels include, but shall not be limited to, natural and
man-made drainageways, swales, streams, ditches, canals, and pipes
flowing partly full.
CONSERVATION DESIGN
A series of holistic land development design goals that maximize
protection of key land and environmental resources, preserve significant
concentrations of open space and greenways, evaluate, and maintain
site hydrology, and ensure flexibility in development design to meet
community needs for complimentary and aesthetically pleasing development.
Conservation design encompasses the following objectives: conservation/enhancement
of natural resources, wildlife habitat, biodiversity corridors, and
greenways (interconnected open space); minimization of environmental
impact resulting from a change in land use (minimum disturbance, minimum
maintenance); maintenance of a balanced water budget by making use
of site characteristics and infiltration; incorporation of unique
natural, scenic and historic site features into the configuration
of the development; preservation of the integral characteristics of
the site as viewed from adjoining roads; and reduction in maintenance
required for stormwater management practices. Such objectives can
be met on a site through an integrated development process that respects
natural site conditions and attempts, to the maximum extent possible,
to replicate or improve the natural hydrology of a site.
CONSERVATION PLAN
A plan written by a planner certified by NRCS that identifies
conservation practices and includes site-specific BMPs for agricultural
plowing or tilling activities and animal heavy use areas.
CONSERVATION PRACTICES
Practices installed on agricultural lands to improve farmland,
soil and/or water quality which have been identified in a current
conservation plan.
CONVEYANCE
A natural or man-made, existing or proposed stormwater management
facility, feature or channel used for the transportation or transmission
of stormwater from one place to another. For the purposes of this
chapter, conveyance shall include pipes, drainage ditches, channels
and swales (vegetated and other), gutters, stream channels, and like
facilities or features.
DESIGN STORM
The magnitude and temporal distribution of precipitation
from a storm event measured in probability of occurrence (e.g., a
five-year storm) and duration (e.g., 24 hours), used in the design
and evaluation of stormwater management systems. Also see "return
period."
DETENTION BASIN
An impoundment designed to collect and retard stormwater
runoff by temporarily storing the runoff and releasing it at a predetermined
rate. Detention basins are designed to drain completely shortly after
any given rainfall event.
DETENTION or TO DETAIN
Capture and temporary storage of runoff in a stormwater management
facility for release at a controlled rate.
DETENTION VOLUME
The volume of runoff that is captured and released into the
waters of the commonwealth at a controlled rate.
DEVELOPER
A person, company or organization who seeks to undertake
any regulated activities at a site in the Township.
DIAMETER AT BREAST HEIGHT (DBH)
The outside bark diameter of a tree at breast height which
is defined as 4.5 feet (1.37 meters) above the forest floor on the
uphill side of the tree.
DISTURBED AREA
Land area disturbed by or where an earth disturbance activity
is occurring or has occurred.
DRAINAGE AREA
That land area contributing runoff to a single point (including
but not limited to the point/line of interest used for hydrologic
and hydraulic calculations) and that is enclosed by a natural or man-made
ridgeline.
EARTH DISTURBANCE or EARTH DISTURBANCE ACTIVITY
A construction or other human activity which disturbs the
surface of the land, including, but not limited to, clearing and grubbing;
grading; excavations; embankments; road maintenance; land development;
building construction; and the moving, depositing, stockpiling, or
storing of soil, rock, or earth materials.
EASEMENT
A right of use granted by a landowner to allow a grantee
the use of the designated portion of land for a specified purpose,
such as for stormwater management or other drainage purposes.
EROSION
The process by which the surface of the land, including water/stream
channels, is worn away by water, wind, or chemical action.
EROSION AND SEDIMENT (E&S) CONTROL PLAN
A plan required by the Conservation District or the Township
to minimize accelerated erosion and sedimentation, and that must be
prepared and approved per the applicable requirements.
EVAPOTRANSPIRATION (ET)
The combined processes of evaporation from the water or soil
surface and transpiration of water by plants.
FEMA
Federal Emergency Management Agency.
FLOOD
A temporary condition of partial or complete inundation of
land areas from the overflow of streams, rivers, and other waters
of this commonwealth.
FLOODPLAIN
Any land area susceptible to inundation by water from any
natural source or delineated by applicable FEMA maps and studies as
being a special flood hazard area.
FLOODWAY
The channel of the watercourse and those portions of the
adjoining floodplains that are reasonably required to carry and discharge
the 100-year flood (also called the base flood or 1% annual chance
flood). Unless otherwise specified, the boundary of the floodway is
as indicated on maps and flood insurance studies provided by FEMA.
In an area where no FEMA maps or studies have defined the boundary
of the floodway, it is assumed, absent evidence to the contrary, that
the floodway extends from the center line of the stream and to 50
feet beyond the top of the bank of the stream on both sides.
FOREST MANAGEMENT/TIMBER OPERATIONS
Planning and activities necessary for the management of forest
lands. These include timber inventory, preparation of forest management
plans, silvicultural treatment, cutting budgets, logging road design
and construction, timber harvesting, site preparation, and reforestation.
FREEBOARD
A vertical distance between the design high-water elevation
and the elevation of the top of a dam, levee, tank, basin, swale,
or diversion berm. The space is required as a safety margin in a pond
or basin.
GEOTEXTILE
A fabric manufactured from synthetic fiber that is used to
achieve specific objectives, including infiltration, separation between
different types of media (i.e., between soil and stone), or filtration.
GRADE/GRADING
1. (noun) A slope, usually of a road, channel, or natural
ground, specified in percent and shown on plans as specified herein.
2. (verb) To finish the surface of a roadbed, the top of an embankment,
or the bottom of an excavation.
GREEN INFRASTRUCTURE
Systems and practices that use or mimic natural processes
to infiltrate, evapotranspire, or reuse stormwater on the site where
it is generated.
GROUNDWATER
Water that occurs in the subsurface and fills or saturates
the porous openings, fractures and fissures of underground soils and
rock units.
GROUNDWATER RECHARGE
The replenishment of existing natural groundwater supplies
from infiltration of rain or overland flow.
HEC-1
The U.S. Army Corps of Engineers, Hydrologic Engineering
Center (HEC) hydrologic runoff model.
HEC-HMS
The U.S. Army Corps of Engineers, Hydrologic Engineering
Center (HEC) - Hydrologic Modeling System (HMS).
HIGH TUNNEL
A structure which meets the following:
A.
Is used for the production, processing, keeping, storing, sale
or shelter of an agricultural commodity as defined in section 2 of
the Act of December 19, 1974 (P.L. 973, No. 319), known as the "Pennsylvania
Farmland and Forest Land Assessment Act of 1974," or for the storage
of agricultural equipment or supplies; and
B.
Is constructed with all the following:
(1)
Has a metal, wood, or plastic frame;
(2)
When covered, has a plastic, woven textile, or other flexible
covering; and
(3)
Has a floor made of soil, crushed stone, matting, pavers, or
a floating concrete slab.
HOTSPOT
Area where prior or existing land use or activities can potentially
generate highly contaminated runoff with concentrations of pollutants
in excess of those typically found in stormwater.
HYDROLOGIC REGIME
The hydrologic system, cycle or balance that sustains the
quality and quantity of stormwater, stream baseflow, storage, and
groundwater supplies under natural conditions.
HYDROLOGIC SOIL GROUP (HSG)
A classification of soils by the Natural Resources Conservation
Service (NRCS) into four runoff potential groups. The groups range
from A soils, which are very permeable and produce little runoff,
to D soils, which are not very permeable and produce much more runoff.
IMPERVIOUS SURFACE
A surface that has been compacted or covered with a layer
of material so that it prevents or is resistant to infiltration of
water, including but not limited to: structures such as roofs, buildings,
storage sheds; other solid, paved or concrete areas such as streets,
driveways, sidewalks, parking lots, patios, tennis or other paved
courts; or athletic playfields comprised of synthetic turf materials.
For the purposes of determining compliance with this chapter, compacted
soils or stone surfaces used for vehicle parking and movement shall
be considered impervious. Surfaces that were designed to allow infiltration
(i.e., pavers and areas of porous pavement) will be considered on
a case-by-case basis by the Township as advised by the Township Engineer.
For the purposes of this chapter, swimming pool water surfaces shall
not be considered impervious.
INFILTRATION
Movement of surface water into the soil, where it is absorbed
by plant roots, evaporated into the atmosphere, or percolated downward
to recharge groundwater.
INFILTRATION FACILITY
A stormwater BMP designed to collect and discharge runoff
into the subsurface in a manner that allows infiltration into underlying
soils and groundwater (e.g., french drains, seepage pits, or seepage
trenches, etc.).
INTERMITTENT STREAM
A defined channel in which surface water is absent during
a portion of the year, in response to seasonal variations in precipitation
or groundwater discharge.
INVERT
The lowest surface, the floor or bottom of a culvert, pipe,
drain, sewer, channel, basin, BMP or orifice.
KARST
A type of topography that is formed over limestone or other
carbonate rock formations by dissolving or solution of the rock by
water, and that is characterized by closed depressions, sinkholes,
caves, a subsurface network of solution conduits and fissures through
which groundwater moves, and no perennial surface drainage features.
LAND DEVELOPMENT
Any of the following activities:
A.
The improvement of one lot or two or more contiguous lots, tracts,
or parcels of land for any purpose involving:
(1)
A group of two or more residential or nonresidential buildings,
whether proposed initially or cumulatively, or a single nonresidential
building on a lot or lots regardless of the number of occupants or
tenure; or
(2)
The division or allocation of land or space, whether initially
or cumulatively, between or among two or more existing or prospective
occupants by means of, or for the purpose of, streets, common areas,
leaseholds, condominiums, building groups, or other features;
C.
Development in accordance with § 503(1.1) of the Pennsylvania
Municipalities Planning Code (as amended);
D.
Development of additional paved areas greater than 2,000 square feet in area; development of any additional paved area not in compliance with or resulting in noncompliance with the impervious cover limits of Chapter
325, Zoning; and development of any additional paved area in excess of the maximum permissible under a previously approved stormwater management plan;
E.
Any earthmoving activity, clearing, grubbing, cutting or removal
of mature trees, or grading for the purpose of layout, construction,
or opening to public or common use of or in connection with any street,
driveway, path or trail, parking area, utility main or facility, stormwater
management facility, buffer screening or landscaping, or other common
private, public, or quasi-public improvement(s).
LANDOWNER
The legal or beneficial owner or owners of land including
the holder of an option or contract to purchase (whether or not such
option or contract is subject to any condition), a lessee if they
are authorized under the lease to exercise the rights of the landowner,
or other person having a proprietary interest in the land.
LICENSED PROFESSIONAL
A Pennsylvania registered professional engineer, or registered
professional geologist, or any other person licensed by the Pennsylvania
Department of State and qualified by law to perform the work required
by the chapter within the Commonwealth of Pennsylvania.
LIMITING ZONE
A soil horizon or condition in the soil profile or underlying
strata that includes one of the following:
A.
A seasonal high-water table, whether perched or regional, determined
by direct observation of the water table or indicated by other subsurface
or soil conditions.
B.
A rock with open joints, fracture or solution channels, or masses
of loose rock fragments, including gravel, with insufficient fine
soil to fill the voids between the fragments.
C.
A rock formation, other stratum, or soil condition that is so
slowly permeable that it effectively limits downward passage of water.
LOW-IMPACT DEVELOPMENT (LID)
Site design approaches and small-scale stormwater management
practices that promote the use of natural systems for infiltration,
evapotranspiration, and reuse of rainwater. LID can be applied to
new development, urban retrofits, and revitalization projects. LID
utilizes design techniques that infiltrate, filter, provide evapotranspiration
and store runoff close to its source. Rather than rely on costly large-scale
conveyance and treatment systems, LID addresses stormwater through
a variety of small, cost-effective landscape features located on-site.
MAINTENANCE
The action taken to restore or preserve the as-built functional
design of any stormwater management facility or system.
MFEMP
Mushroom Farm Environmental Management Plan.
MPC
Act of July 31, 1968, P.L. 805, No. 247, 53 P.S. § 10101
et seq., as amended, the Pennsylvania Municipalities Planning Code,
Act 247.
MS4
Municipal separate storm sewer system.
MUNICIPAL ENGINEER or TOWNSHIP ENGINEER
A professional engineer licensed as such in the Commonwealth
of Pennsylvania, duly appointed as the engineer for a municipality,
planning agency, or joint planning commission.
MUNICIPALITY
West Whiteland Township, Chester County, Pennsylvania.
NEW DEVELOPMENT
Any regulated activity involving placement or construction
of new impervious surface or grading over existing pervious land areas
not classified as redevelopment as defined in this chapter.
NOAA
National Oceanic and Atmospheric Administration.
NONPOINT SOURCE POLLUTION
Pollution that enters a water body from diffuse origins in
the watershed and does not result from discernible, confined, or discrete
conveyances.
NONSTORMWATER DISCHARGES
Water flowing in stormwater collection facilities, such as
pipes or swales, which is not the result of a rainfall event or snowmelt.
NPDES
National Pollutant Discharge Elimination System, the federal
government's system for issuance of permits under the Clean Water
Act, which is delegated to PADEP in Pennsylvania.
NRCS
Natural Resource Conservation Service (previously Soil Conservation
Service, SCS), an agency of the U.S. Department of Agriculture.
PADEP
Pennsylvania Department of Environmental Protection.
PARENT TRACT
The parcel of land from which a land development or subdivision
originates, determined from the date of Township adoption of this
chapter.
PEAK DISCHARGE
The maximum rate of stormwater runoff from a specific storm
event.
PennDOT
Pennsylvania Department of Transportation.
PLANNING COMMISSION
The Planning Commission of West Whiteland Township, Chester
County, Pennsylvania.
POINT SOURCE
Any discernible, confined, and discrete conveyance including,
but not limited to, any pipe, ditch, channel, tunnel, or conduit from
which stormwater is or may be discharged, as defined in state regulations
at 25 Pa. Code § 92.1.
POST-CONSTRUCTION
Period after construction during which disturbed areas are
stabilized, stormwater controls are in place and functioning, and
all proposed improvements approved by the Township are completed.
PREDEVELOPMENT
Land cover conditions assumed to exist within the proposed
disturbed area prior to commencement of the regulated activity for
the purpose of calculating the predevelopment water quality volume,
infiltration volume, and peak flow rates as required in this chapter.
PRETREATMENT
Techniques employed in stormwater BMPs to provide storage
or filtering, or other methods to trap or remove coarse materials
and other pollutants before they enter the stormwater system, but
may not necessarily be designed to meet the entire water quality volume
requirements of this chapter.
RECHARGE
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
REDEVELOPMENT
Any regulated activity that involves demolition, removal,
reconstruction, or replacement of existing impervious surface(s).
REGULATED ACTIVITY
Any earth disturbance activity(ies) or any activity that
involves the alteration or development of land in a manner that may
affect stormwater runoff.
REGULATED IMPERVIOUS SURFACE
Proposed impervious surface as part of a current proposed
activity and all existing impervious surfaces installed after October
8, 2014 as part of previous activity.
RETENTION BASIN
An impoundment that is designed to temporarily detain a certain
amount of stormwater from a catchment area and which may be designed
to permanently retain stormwater runoff from the catchment area; retention
basins always contain water.
RETENTION or TO RETAIN
The prevention of direct discharge of stormwater runoff into
surface waters or water bodies during or after a storm event by permanent
containment in a pond or depression; examples include systems which
discharge by percolation to groundwater, exfiltration, and/or evaporation
processes and which generally have residence times of less than three
days.
RETENTION VOLUME/REMOVED RUNOFF
The volume of runoff that is captured and not released directly
into the surface waters of the commonwealth during or after a storm
event.
RETURN PERIOD
The average interval, in years, within which a storm event
of a given magnitude can be expected to occur one time. For example,
the twenty-five-year return period rainfall would be expected to occur
on average once every 25 years; or, stated in another way, the probability
of a twenty-five-year storm occurring in any one year is 0.04 (i.e.,
a 4% chance).
RIPARIAN
Pertaining to anything connected with or immediately adjacent
to the banks of a stream or other body of water.
RIPARIAN BUFFER
An area of land adjacent to a body of water and managed to
maintain vegetation to protect the integrity of stream channels and
shorelines, to reduce the impact of upland sources of pollution by
trapping, filtering, and converting sediments, nutrients, and other
chemicals, and to supply food, cover and thermal protection to fish
and other aquatic species and wildlife.
RUNOFF
Any part of precipitation that flows over the land surface.
SALDO
See "Subdivision and Land Development Ordinance."
SCS
Soil Conservation Service, now known as the Natural Resources
Conservation Service.
SEDIMENT
Soil or other materials transported by, suspended in or deposited
by surface water as a product of erosion.
SEPARATE STORM SEWER SYSTEM
A conveyance or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters,
ditches, man-made channels, or storm drains) primarily used for collecting
and conveying stormwater runoff.
SHEET FLOW
A flow process associated with broad, shallow water movement
on sloping ground surfaces that is not channelized or concentrated.
SITE
Total area of land in the Township where any proposed regulated
activity, as defined in this chapter, is planned, conducted, or maintained
or that is otherwise impacted by the regulated activity.
SOIL COVER COMPLEX METHOD
A method of runoff computation developed by NRCS that is
based on relating soil type and land use/cover to a runoff parameter
called "curve number (CN)."
STATE WATER QUALITY REQUIREMENTS
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Pennsylvania Code Title 25 and the
Clean Streams Law.
STORMWATER
Drainage runoff from the surface of the land resulting from
precipitation or snow or ice melt.
STORMWATER CONTROL MEASURE
Physical features used to effectively control, minimize,
and treat stormwater runoff. [See "best management practice (BMP)"].
STORMWATER MANAGEMENT (SWM) SITE PLAN
The plan prepared by the applicant or its representative, in accordance with the requirements of Article
IV of this chapter, indicating how stormwater runoff will be managed at a particular site in accordance with this chapter, and including all necessary design drawings, calculations, supporting text, and documentation to demonstrate that chapter requirements have been met, herein referred to as "SWM site plan." All references in this chapter to "final" or "approved" SWM site plans shall incorporate the approved SWM site plan and all subsequent approved revisions thereto.
STORMWATER MANAGEMENT FACILITY
Any feature, natural or man-made, that, due to its condition,
design, or construction, conveys, stores, or otherwise affects stormwater
runoff quality, rate or quantity, including best management practices
and stormwater control measures. Typical stormwater management facilities
include, but are not limited to, detention and retention basins, open
channels, storm sewers, pipes, and infiltration facilities.
SUBDIVISION
The division or redivision of a lot, tract, or parcel of
land as defined in The Pennsylvania Municipalities Planning Code,
Act of July 31, 1968, P.L. 805, No. 247, as amended.
SWALE
An artificial or natural waterway or low-lying stretch of
land that gathers and conveys stormwater or runoff, and is generally
vegetated for soil stabilization, stormwater pollutant removal, and
infiltration.
TOP-OF-BANK
Highest point of elevation of the bank of a stream or channel
cross section at which a rising water level just begins to flow out
of the channel and into the floodplain.
TOWNSHIP
West Whiteland Township, Chester County, Pennsylvania.
USDA
United States Department of Agriculture.
WATER TABLE
The uppermost level of saturation of pore space or fractures
by groundwater. "Seasonal high-water table" refers to a water table
that rises and falls with the seasons due either to natural or man-made
causes.
WATERCOURSE
A channel or conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
WATERS OF THE COMMONWEALTH
Any and all rivers, streams, creeks, rivulets, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs, and all other bodies or channels of conveyance of
surface and underground water, or parts thereof, whether natural or
artificial, within or on the boundaries of the commonwealth.
WATERSHED
Region or area drained by a river, watercourse, or other
body of water, whether natural or artificial.
WETLAND
Those areas that are inundated or saturated by surface- or
groundwater at a frequency and duration sufficient to support, and
that under normal circumstances do support, a prevalence of vegetation
typically adapted for life in saturated soil conditions. Wetlands
generally include swamps, marshes, bogs, fens, and similar areas.
WOODS
Any land area of at least 1/4 acre with a natural or naturalized
ground cover (excluding manicured turf grass) and that has an average
density of two or more viable trees per 1,500 square feet with a DBH
of six inches or greater and where such trees existed at any time
within three years of the time of land development application submission
of the proposed project. The land area to be considered woods shall
be measured from the outer driplines of the outer trees.