As used in this chapter, 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 of a rate greater than would occur
because of the natural process alone.
AGRICULTURAL OPERATION
An enterprise that is actively and continuously engaged in the commercial
production and preparation for market of crops, livestock and livestock products
and in the production, harvesting and preparation for market or use of agricultural,
agronomic, horticultural, silvicultural and aquacultural crops and commodities.
The term includes an enterprise that implements changes in production practices
and procedures or types of crops, livestock, livestock products or commodities
produced consistent with practices and procedures that are normally engaged
by farmers or are consistent with technological development within the agricultural
industry excluding the construction of buildings, structures and impervious
surfaces.
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, 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 an application for a drainage
permit and a drainage plan or filed an application for approval to engage
in any regulated activities as defined in §
126-4 of this chapter.
BEST MANAGEMENT PRACTICES (BMP)
Stormwater structures, facilities and techniques to control, maintain
or improve the quantity and quality of surface runoff.
CHANNEL EROSION
The widening, deepening and headward cutting of small channels and
waterways due to erosion caused by moderate to large floods.
CISTERN
A reservoir or tank for storing rainwater.
CULVERT
A structure with appurtenant works which carries a stream or stormwater
runoff 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.
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.
DESIGNEE
The agent of the Antrim Township Planning Commission and/or agent
of the Antrim Township Board of Supervisors involved with the administration,
review or enforcement of any provisions of this chapter by contract or memorandum
of understanding.
DETENTION BASIN
A structure designed to temporarily detain surface runoff for a period
of time sufficient to reduce the velocity and rate of surface flows leaving
a site. Detention basins drain fully after rainfall has ceased.
DETENTION STRUCTURE
A vegetated pond, swale or other structure designed to drain completely
after storing runoff only for a given storm event and release it at a predetermined
rate; also known as a "dry pond."
DEVELOPER
Any landowner, agent of such landowner or tenant with the permission
of such landowner who makes or causes to be made a subdivision of land, a
land development or any of the regulated activities as defined in §
126-4.
DEVELOPMENT SITE
The specific tract of land for which a regulated activity is proposed.
DIFFUSED DRAINAGE DISCHARGE
Drainage discharge not confined to a single point location or channel,
such as sheet flow or shallow concentrated flow.
DOWNSLOPE PROPERTY LINE
That portion of the property line of the lot, tract or parcels of
land being developed located such that all or most of the overland or pipe
flow from the site would be directed towards it.
DRAINAGE CONVEYANCE FACILITY
A stormwater management facility designed to transmit stormwater
runoff and shall include streams, channels, swales, pipes, conduits, culverts,
storm sewers, stormwater detention/retention facilities, etc.
EARTH DISTURBANCE
Any activity which alters, disturbs and exposes the existing land
surface.
EASEMENT
A right granted for the use of private land for certain public, quasi-public
or private purpose; also, the land to which such right pertains.
ENERGY DISSIPATER
A device used to slow the velocity of stormwater, particularly at
points of concentrated discharge such as pipe outlets.
EROSION
The movement of soil particles by the action of water, wind, ice
or other natural forces.
EXCEPTIONAL VALUE WATERS
Surface waters of high quality which satisfy Pennsylvania Code Title
25 Environmental Protections, Chapter 93 Water Quality Standards, Section
93.4b(b) (relating to antidegradation).
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, mapped as being a
special flood hazard area. Also included are areas that comprise Group 13
soils, as listed in Appendix A of the Pennsylvania Department of Environmental
Protection (PA DEP) Technical Manual for Sewage Enforcement Officers (as amended
or replaced from time to time by PA DEP).
FLOODWAY
The channel of the watercourse and those portions of the adjoining
floodplains which 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 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
FREEBOARD
The difference between the design flow elevation in the emergency
spillway of a basin and the top of the basin embankment, and the difference
between the design flow elevation of a swale and the top of a the swale embankment.
GRADE
A slope, usually of a road, channel or natural ground, specified
in percent and shown on plans as specified herein. (To) grade: to finish the
surface of a roadbed, top of embankment or bottom of excavation.
GRASSED WATERWAY (SWALE)
A natural or man-made drainageway of parabolic, trapezoidal, rectangular
or triangular cross section shaped to required dimensions and vegetated with
erosion-resistant grasses for conveyance of runoff.
HIGH QUALITY WATERS
Surface waters having quality which exceeds levels necessary to support
propagation of fish, shellfish, and wildlife and recreation in and on the
water by satisfying Pennsylvania Code Title 25, Environmental Protection,
Chapter 93 Water Quality Standards, § 93.4b(a).
IMPERVIOUS SURFACE
A surface that prevents or impedes the percolation of water into
the ground.
INFILTRATION FACILITY
A structure or other man-made feature designed to collect runoff
and direct it into the ground.
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.
LAND DEVELOPMENT
Any of the following activities:
A.
The improvement of one 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.
(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.
"Land development" does not include development which involves:
(1)
The conversion of an existing single-family detached dwelling or single-family
semidetached dwelling into not more than three residential units, unless such
units are intended to be condominiums.
(2)
The addition of an accessory building, including farm buildings, on
a lot or lots subordinate to an existing principal building.
(3)
The addition or conversion of buildings or rides within the confines
of an enterprise which would be considered an amusement park. For the purpose
of the subsection, an amusement park is defined as a tract or areas used principally
as a location for permanent amusement structures or rides. This exclusion
shall not apply to newly acquired acreage by an amusement park until initial
plans for the expanded area have been approved by the proper authorities.
MANNING'S EQUATION (in Manning's 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
Township of Antrim, Franklin County, Pennsylvania.
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.
NRCS
Natural Resource Conservation Service (previously SCS).
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, and canals.
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.
PEAK DISCHARGE
The maximum rate of stormwater runoff from a specific storm event
and location.
PERCOLATION TEST
A procedure to determine the absorption rate of the soil in an area
proposed as the installation site for an on-lot septic system or stormwater
infiltration facility, to be carried out according to the requirements of
the Pennsylvania Department of Environmental Protection.
PIPE
A culvert, closed conduit, or similar structure (including appurtenances)
that conveys stormwater.
REGULATED ACTIVITIES
Actions or proposed actions that have an impact on stormwater runoff
and that are specified in this chapter.
RELEASE RATE
The rate at which runoff is released from a site or subarea measured
in cubic feet per second.
RETENTION BASIN
A reservoir, formed from soil or other material, which is designed
to retain permanently a certain amount of stormwater which also may be designed
to temporarily detain surface runoff for a period of time sufficient to reduce
the velocity and rate of surface flows leaving a site. Retention basins also
may receive fresh water from year-round streams. Retention basins always contain
water, and thus may be considered man-made lakes or ponds.
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 of once every 25
years.
RISER
A vertical pipe or inlet structure extending from the bottom of a
pond that is used to control the discharge rate from the pond for a specified
design storm.
RUNOFF
Any part of precipitation that flows over the land surface.
SEDIMENTATION
The process by which mineral or organic matter is accumulated or
deposited by moving wind, water or gravity. Once this matter is deposited
(or remains suspended in water), it is usually referred to as "sediment."
SEDIMENT BASIN
A temporary dam or barrier constructed across a waterway or at other
suitable locations to intercept the runoff and to trap and retain the sediment.
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 in the ground.
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 the Natural Resources Conservation Service,
formerly the Soil Conservation Service, 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 which is used to
pass peak discharge greater than the maximum design storm controlled by the
pond.
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."
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
facilities.
STORMWATER MANAGEMENT PLAN
The plan prepared by the developer or his representative indicating
how stormwater runoff will be managed at the particular site of interest according
to this chapter.
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, partition by the court for distribution to heirs or devisees, 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 dwelling,
shall be exempted.
SWALE
See "grassed waterway."
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.
TOWNSHIP
Antrim Township, Franklin County, Pennsylvania.
TOWNSHIP ENGINEER
A professional engineer licensed as such in the Commonwealth of Pennsylvania
or any other professional consultant designated by the Board of Supervisors
to perform the duties of an engineer on behalf of the Township.
WATERCOURSE
A permanent stream, intermittent stream, river, brook, creek channel
or ditch for water, whether natural or man-made.
WETLAND
Those areas that are inundated or saturated by surface water 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, including swamps, marshes, bogs, fens and similar areas.