As used in this part, the following terms shall
have the meanings indicated:
ACCELERATED EROSION
The removal of the surface of the land through the combined
action of man's activity and the natural processes at a rate greater
than would occur because of the natural process alone.
ACCESSORY STRUCTURE
A structure detached from a principal building located on
the same lot and customarily incidental and subordinate to the principal
building or use.
AGRICULTURAL ACTIVITIES
The work of producing crops and raising livestock including
tillage, plowing, disking, harrowing, pasturing, and installation
of conservation measures. Construction of new buildings or impervious
area is not considered an agricultural activity.
ALTERATION
As applied to land, a change in topography as a result of
the moving of soil and rock from one location or position to another,
and also, the changing of surface conditions by causing the surface
to be more or less impervious; land disturbance.
APPLICANT
A landowner or developer who has submitted a drainage plan or filed an application for approval to engage in any regulated activities as defined in §
148-36 of this part.
AS-BUILT DRAWINGS
A set of engineering or site drawings that delineates the
specific permitted stormwater management facility as actually constructed.
BMP (BEST MANAGEMENT PRACTICE)
Stormwater structures, facilities, and techniques to maintain
or improve the water quality of surface runoff. Pennsylvania Handbook
of Best Management Practices for Developing Areas, Spring 1998.
CHANNEL EROSION
The widening, deepening, and headward cutting of small channels
and waterways due to erosion caused by moderate to large floods.
CHAPTER 148 PERMIT
A permit issued by the Township after the drainage plan has
been approved. Said permit is issued prior to or contemporaneously
with the final Township approval.
CISTERN
An underground reservoir or tank, both permeable and nonpermeable,
managing rainwater.
COMBINED SEWERS
A sewerage system that carries both sanitary sewage and stormwater
runoff.
CULVERT
A structure with appurtenant works that carries a stream
under or through an embankment or fill.
DAM
An artificial barrier, together with its appurtenant works,
constructed for the purpose of impounding or storing water or another
fluid or semifluid, or a refuse bank, fill, or structure for highway,
railroad, or other purposes which does or may impound water or another
fluid or semifluid.
DESIGNEE
The agent of the Delaware County Planning Department and/or
agent of the governing body involved with the administration, review,
or enforcement of any provisions of this part by contract or memorandum
of understanding.
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.
DETENTION BASIN
An impoundment structure designed to manage stormwater runoff
by temporarily storing the runoff and releasing it at a predetermined
rate.
DETENTION DISTRICT
Those subareas in which some type of detention is required
to meet the plan requirements and the goals of Act 167.
DEVELOPER
A person, partnership, association, corporation, or other
entity, or any responsible person therein or agent thereof, that undertakes
any regulated activity of this part.
DEVELOPMENT SITE
The specific tract of land for which a regulated activity
is proposed.
DISCHARGE EASEMENT
The grant of a property right to allow runoff in excess of
the previous quantity and/or rate of flow.
DOWNSLOPE PROPERTY LINE
That portion of the property line of the lot, tract, or parcels
of land being developed located such that all overland or pipe flow
from the site would be directed towards it.
DRAINAGE CONVEYANCE FACILITY
A stormwater management facility designed to transmit stormwater
runoff, including streams, channels, swales, pipes, conduits, culverts,
storm sewers, etc.
DRAINAGE EASEMENT
A right granted by a landowner to a grantee allowing the
use of private land for stormwater management purposes.
DRAINAGE PLAN
The documentation of the stormwater management system, if any, to be used for a given development site, the contents of which are established in §
148-46.
EARTH DISTURBANCE
Any activity including, but not limited to, construction,
mining, timber harvesting, and grubbing which alters, disturbs, and
exposes the existing land surface.
EASEMENT
A right-of-way granted, but not dedicated, for limited use
of private land for a public or quasi-public purpose (e.g., utility
lines) and within which the owner of the property shall not erect
any permanent structures.
EPHEMERAL STREAMS
Streams that carry only surface runoff and are dry except
during precipitation events. The groundwater table is generally located
below the bottom of ephemeral streams. This may be a water of the
Commonwealth.
EROSION
The movement of soil particles by the action of water, wind,
ice, or other mechanical or natural forces.
EROSION AND SEDIMENT POLLUTION CONTROL PLAN
A plan that is designed to minimize accelerated erosion and
sedimentation. Said plan must be submitted to and approved by the
Delaware County Conservation District and/or Concord Township before
construction can proceed.
EXISTING CONDITIONS
The initial condition of a project site prior to the proposed
construction. If the initial condition of the site is undeveloped
land, the land use shall be considered as "meadow" on B soils unless
the natural land cover is proven to generate lower curve numbers or
Rational C value, such as forested lands.
FLOOD
A general but temporary condition of partial or complete
inundation of normally dry 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 Department of Housing and
Urban Development, Federal Insurance Administration, Flood Hazard
Boundary Map or Concord Township Flood District Map, 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 one-hundred-year frequency flood. Unless otherwise specified,
the boundary of the floodway is as indicated on maps and flood insurance
studies provided by the Federal Emergency Management Agency (FEMA).
In an area where no FEMA maps or studies have defined the boundary
of the one-hundred-year frequency floodway, it is assumed, absent
evidence to the contrary, that the floodway extends from the stream
to 50 feet from the top of the bank of the stream.
FOREST MANAGEMENT/TIMBER OPERATIONS
Planning and activities necessary for the management of forest
land. These include timber inventory and 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 elevation of the design high
water and the top of a dam, levee, tank, basin, or diversion ridge.
The space is required as a safety margin in a pond, berm, or basin.
GRADE
A slope, usually of a road, channel, or natural ground, specified
in percent and shown on plans as specified herein. "To grade" means
to finish the surface of a roadbed, top of embankment, or bottom of
excavation.
GRASSED WATERWAY
A natural or constructed waterway, usually broad and shallow,
covered with erosion-resistant grasses, used to conduct surface water
from cropland.
GROUNDWATER RECHARGE
Replenishment of existing natural underground water supplies.
This is to be the first chosen method of stormwater management.
IMPERVIOUS SURFACE
A surface that has been compacted or covered with material
to the extent that it is highly resistant to infiltration by water,
including, but not limited to, conventional impervious surfaces such
as paved streets, roofs, compacted stone, and sidewalks. In addition,
the following shall be considered impervious surfaces when used by
motor vehicles: graveled areas, paver blocks, bricks, and cobblestone.
IMPOUNDMENT
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
INFILTRATION STRUCTURES
A structure designed to direct runoff into the ground (e.g.,
french drains, seepage pit, and seepage trench) to accomplish groundwater
recharge.
INLET
A surface connection to a closed drain. A structure at the
diversion end of a conduit. The upstream end of any structure through
which water may flow.
INTERMITTENT STREAMS
Streams which flow only during wet seasons. The groundwater
table generally is at or above the bottom of intermittent streams
during wet seasons but drops below the stream bottom during dry seasons.
Stream flow in intermittent streams is primarily due to precipitation
but does have some groundwater contribution during wet seasons. These
streams may be waters of the commonwealth.
LAND DEVELOPMENT
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 PA Municipalities Planning Code.
LAND/EARTH DISTURBANCE
Any activity involving grading, tilling, digging, or filling
of ground or stripping of vegetation or any other activity that causes
an alteration to the natural condition of the land.
MAIN STEM (MAIN CHANNEL)
Any stream segment or other runoff conveyance facility used
as a reach in the Chester Creek hydrologic model.
MANNING EQUATION (IN MANNING FORMULA)
A method for calculation of velocity of flow (e.g., feet
per second) and flow rate (e.g., cubic feet per second) in open channels
based upon channel shape, roughness, depth of flow, and slope. "Open
channels" may include closed conduits so long as the flow is not under
pressure.
MUNICIPALITY
Concord Township, Delaware County, Pennsylvania.
NRCS
Natural Resource Conservation Service [previously the Soil
Conservation Service (SCS)].
NONPOINT SOURCE POLLUTION
Pollution that enters a watery body from diffuse origins
in the watershed and does not result from discernible, confined, or
discrete conveyances.
OPEN CHANNEL
A drainage element in which stormwater flows with an open
surface. Open channels include, but shall not be limited to, natural
and man-made drainageways, swales, streams, ditches, canals, and pipes
flowing partly full.
OUTFALL
Point where water flows from a conduit, stream, or drain.
OUTLET
Points of water disposal from a stream, river, lake, tidewater,
or artificial drain.
PARKING LOT STORAGE
Involves the use of impervious parking areas as temporary
impoundments with controlled release rates during rainstorms.
PEAK DISCHARGE
The maximum rate of stormwater runoff from a specific storm
event.
PERENNIAL STREAMS
Streams that flow year round. Perennial streams derive their
flow from both groundwater and runoff, and the groundwater table never
drops below the streambed. These streams are always waters of the
commonwealth.
PIPE
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
PMF (PROBABLE MAXIMUM FLOOD)
The flood that may be expected from the most severe combination
of critical meteorological and hydrologic conditions that are reasonably
possible in any area. The PMF is derived from the probable maximum
precipitation (PMP) as determined based on data obtained from the
National Oceanographic and Atmospheric Administration (NOAA).
REDEVELOPMENT
Reconstruction of an existing improved, developed property,
as of the date of adoption of this part.
REGULATED ACTIVITIES
Actions or proposed actions that have an impact on stormwater runoff and that are specified in §
148-36 of this part.
RELEASE RATE
The percentage of predevelopment peak rate of runoff from
a site or subarea to which the postdevelopment peak rate of runoff
must be reduced to protect downstream areas.
RESTRICTIVE COVENANT
A restriction on the use of land usually set forth in the
deed. Restrictive covenants (a.k.a. deed restrictions) usually run
with the land and are legally binding upon subsequent owners of the
property.
RETENTION BASIN
An impoundment in which stormwater is stored and not released
during the storm event. Stored water may be released from the basin
at some time after the end of the storm.
RETURN PERIOD
The average interval, in years, within which a storm event
of a given magnitude can be expected to recur. For example, the twenty-five-year
return period rainfall would be expected to recur on the average once
every 25 years.
RIPARIAN BUFFER
A vegetative strip paralleling the banks of a perennial or
intermittent stream or other water body (including wetlands and ponds).
The buffer shall contain appropriate native vegetation throughout
its width with the exception of a minimum twenty-five-foot wide strip
of land maintained in meadow grass or forbs at its outer boundary.
See also Appendix C, Riparian Buffer Technical Reference Guide.
RISER
A vertical pipe extending from the bottom of a pond that
is used to control the discharge rate from the pond for a specified
design storm.
ROOFTOP DETENTION
Temporary ponding and gradual release of stormwater falling
directly onto flat roof surfaces by incorporating controlled-flow
roof drains into building designs in the form of a seepage pit/seepage
trench.
RUNOFF
Any part of precipitation that flows over the land surface.
SEDIMENT BASIN
A barrier, dam, or retention or detention basin located and
designed to retain rock, sand, gravel, silt, or other material transported
by water.
SEDIMENTATION
The process by which matter is accumulated or deposited by
the movement of water.
SEDIMENT POLLUTION
The placement, discharge, or any other introduction of sediment
into the waters of the commonwealth occurring from the failure to
design, construct, implement, or maintain control measures and control
facilities in accordance with the requirements of this part.
SEEPAGE PIT/SEEPAGE TRENCH
An area of excavated earth filled with loose stone or similar
coarse material into which surface water is directed for infiltration
into the ground to accomplish groundwater recharge.
SHEET FLOW
Runoff that flows over the ground surface as a thin, even
layer, not concentrated in a channel.
SOIL-COVER COMPLEX METHOD
A method of runoff computation developed by the NRCS that
is based on relating soil type and land use/cover to a runoff parameter
called curve number (CN).
SOIL GROUP, HYDROLOGIC
A classification of soils by SCS 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.
SPILLWAY
A depression in the embankment of a pond or basin that is
used to pass the peak discharge which is greater than the maximum
design storm controlled by the pond.
STORAGE INDICATION METHOD
A reservoir routing procedure based on solution of the continuity
equation (inflow minus outflow equals the change in storage) with
outflow defined as a function of storage volume and depth.
STORM FREQUENCY
The number of times that a given storm event occurs or is
exceeded on the average in a stated period of years. See "return period."
STORM SEWER
A system of pipes and/or open channels that conveys intercepted
runoff and stormwater from other sources but excludes domestic sewage
and industrial wastes.
STORMWATER
The total amount of precipitation reaching the ground surface.
STORMWATER MANAGEMENT FACILITY
Any structure, natural or man-made, that, due to its condition,
design, or construction, conveys, stores, or otherwise affects stormwater
runoff. Typical stormwater management facilities include, but are
not limited to, detention and retention basins, open channels, storm
sewers, pipes, and infiltration structures.
STORMWATER MANAGEMENT PLAN
The plan for managing stormwater runoff in the Chester Creek Watershed adopted by Delaware and Chester Counties as required by the Act of October 4, 1978, P.L. 864, (Act 167), and known as the "Act 167 Stormwater Management Plan, Chester Creek Watershed," as well as Chapter
148, Part
1, of the Concord Township Code.
STORMWATER MANAGEMENT SITE PLAN
The plan prepared by the applicant or his representative
indicating how stormwater runoff will be managed at the particular
site of interest according to this part.
STREAM ENCLOSURE
A bridge, culvert, or other structure in excess of 100 feet
in length upstream to downstream which encloses a regulated water
of this commonwealth.
SUBAREA
The smallest drainage unit of a watershed for which stormwater
management criteria have been established in the stormwater management
plan.
SUBDIVISION
The division or redivision of a lot, tract, or parcel of
land by any means into two or more lots, tracts, parcels, or other
divisions of land including changes in existing lot lines for the
purpose, whether immediate or future, of lease, transfer of ownership,
or building or lot development; provided, however, that the subdivision
by lease of land for agricultural purposes into parcels of more than
10 acres not involving any new street or easement of access or any
residential dwellings shall be exempt.
SWALE
A low-lying stretch of land that gathers or carries surface
water runoff.
TIME OF CONCENTRATION (TC)
The time for surface runoff to travel from the hydraulically
most distant point of the watershed to a point of interest within
the watershed. This time is the combined total of overland flow time
and flow time in pipes or channels, if any.
TR-20
The computer-based hydrologic modeling technique adapted
to the Chester Creek Watershed for the Act 167 plan. The model has
been calibrated to reflect actual recorded flow values by adjusting
key model input parameters.
TR-55
A method for determining runoff volumes and rates developed
by NRCS.
WATERCOURSE
A channel or conveyance of surface water having defined bed
and banks, whether natural or artificial, with perennial or intermittent
flow.
WATERS OF THE COMMONWEALTH
Any and all rivers, streams, creeks, rivulets, 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 this commonwealth.
WETLAND
Those areas that are inundated or saturated by surface water
or groundwater at a frequency and duration during the growing season
sufficient to support, and that under normal circumstances do support,
a prevalence of vegetation typically adapted for life in saturated
soil conditions, including swamps, marshes, bogs, and similar areas
(hydrophytic regitation).