As used in this chapter, the following terms shall have the
meanings indicated:
ACT
The Storm Water Management Act (Act of October 4, 1978, P.L.
864, No. 167; 32 P.S. §§ 680.1 through 680.17, as amended
by Act of May 24, 1984, No. 63).
APPLICANT
A landowner or developer who has filed an application for
development, including his/her heirs, successors and assigns.
CHANNEL
A perceptible natural or artificial waterway which periodically
or continuously contains moving water or which forms a connecting
link between two bodies of water. It has a definite bed and banks
which confine the water.
CISTERN
An underground reservoir or tank for storage of rainwater.
CULVERT
A closed conduit for the free passage of surface drainage
under a highway, railroad, canal or other embankment.
DESIGN CRITERIA
A.
Engineering guidelines specifying construction details and materials.
B.
Objectives, results or limits which must be met by a facility,
structure or process in performance of its intended functions.
DESIGN STORM
The magnitude of precipitation from a storm event measured
in probability of occurrence (e.g., fifty-year storm) and duration
(e.g., twenty-four-hour), and used in computing stormwater management
control systems.
DESIGNEE
Unless otherwise noted, the official designee of the Borough
for action on behalf of the Borough under the terms of this chapter
shall be the Borough Engineer.
DETENTION
The slowing, dampening or attenuating of runoff flows entering
the natural drainage pattern or storm drainage system by temporarily
holding water on a surface area in a detention basin or within the
drainage system.
DETENTION POND
A pond or reservoir, usually small, constructed to impound
or retard surface runoff temporarily.
DEVELOPER
The person, persons or any corporation, partnership, association
or other entity or any responsible person therein or agent therefor
that undertakes the activities associated with changes in land use.
The term "developer" is intended to include, but not necessarily be
limited to, the terms "subdivider," "owner" and "builder" even though
the individuals involved in successive stages of the project may vary.
DEVELOPMENT
Any activity, construction, alteration, change in land use
or practice that affects stormwater runoff characteristics.
DISCHARGE
The flow or rate of flow from a canal, conduit, channel or
other hydraulic structure.
DIVERSION
A channel and a ridge constructed to a predetermined grade
across a slope and designed to collect and/or divert runoff from slopes
which are subject to erosion.
DRAINAGE
In general, the removal of surface water from a given area;
commonly applied to surface water and groundwater.
DRAINAGE AREA
A.
The area of a drainage basin or watershed, expressed in acres,
square miles or other unit of area. Also called catchment area, watershed,
river basin.
B.
The area served by a sewer system receiving stormwater and surface
water or by a watercourse.
DRAINAGE EASEMENT
A right granted by a landowner to a grantee allowing the
use of private land for stormwater management purposes.
ENCROACHMENT
Any structure or activity which in any manner changes, expands
or diminishes the course, current or cross section of any watercourse,
floodway or body of water.
EROSION
Wearing away of the lands by running water, winds and waves.
EROSION CONTROL
The application of measures to reduce erosion of land surfaces.
GROUNDWATER
Subsurface water occupying the saturation zone, from which
wells and springs are fed.
GROUNDWATER RECHARGE
Replenishment of groundwater naturally by precipitation or
runoff or artificially by spreading or injection.
HYDRAULIC GRADE LINE
A line joining points whose vertical distance from the center
of the cross section of the fluid flowing in a pipe are proportional
to the pressure in the pipe at the point.
IMPERVIOUS
Not allowing or allowing only with great difficulty the movement
of water; impermeable.
INFILTRATION
A.
The flow or movement of water through the interstices or pores
of a soil or other porous medium.
B.
The absorption of liquid by the soil.
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.
LAND DISTURBANCE
Any activity involving the changing, grading, transportation,
fill and any other activity which causes land to be exposed to the
danger of erosion.
MAINTENANCE
The upkeep necessary for efficient operation of physical
properties.
MUNICIPALITY
The Borough of Wilmerding, Allegheny County, Pennsylvania.
NATURAL STORMWATER RUNOFF REGIME
A watershed where natural surface configurations, runoff
characteristics and defined drainage conveyances have attained the
conditions of equilibrium.
NRCS
U.S. Department of Agriculture, Natural Resources Conservation
Service (formerly SCS).
OUTFALL
A.
The point, location or structure where drainage discharges from
a sewer, drain or other conduit.
B.
The conduit leading to the ultimate discharge point.
OUTLET CONTROL STRUCTURE
The means of controlling the relationship between the headwater
elevation and the discharge, placed at the outlet or downstream end
of any structure through which water may flow.
PEAK DISCHARGE
The maximum rate of flow of water at a given point and time
resulting from a specified storm event.
PERFORMANCE STANDARD
Standard which establishes an end result or outcome which
is to be achieved but does not prescribe specific means for achieving
it.
PRIVATE ENTITY
A partnership, corporation, homeowners' association, condominium
association or any other similar association as distinguished from
an individual lot owner.
RATIONAL FORMULA
A rainfall-runoff relation used to estimate peak flow, expressed
by the following formula:
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Where:
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Q
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=
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peak runoff rate in cfs (cubic feet per second)
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C
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=
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runoff coefficient
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I
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=
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design rainfall intensity (inches/hour) lasting for a critical
time, Tc, or longer
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|
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Tc
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=
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time of concentration
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|
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A
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=
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drainage area in acres
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RECURRENCE INTERVAL
The average interval of time, stated in years, within which
a given storm event will be equaled or exceeded once.
RELEASE RATE PERCENTAGE
The watershed factor determined by comparing the maximum
rate of runoff from a subbasin to the contributing rate of runoff
to the watershed peak rate at specific points of interest.
RETENTION POND
A basin, usually enclosed by artificial dikes, that is used
to retard stormwater runoff by temporarily storing the runoff and
releasing it at a predetermined rate.
RETURN PERIOD
The average interval in years over which an event of a given
magnitude can be expected to recur.
RUNOFF
That part of precipitation which flows over the land.
RUNOFF CHARACTERISTICS
The surface components of any watershed which affect the
rate, amount and direction of stormwater runoff. These may include,
but are not limited to, vegetation, soils, slopes and man-made landscape
alterations.
SEDIMENT
Mineral or organic solid material that is being transported
or has been moved from its site of origin by air, water or ice and
has come to rest.
SEDIMENTATION
The process by which mineral or organic matter is accumulated
or deposited by moving water, wind or gravity.
SEEPAGE TANK
A subsurface concrete tank surrounded by stone, into which
surface water is directed for infiltration into the ground.
SEMIPERVIOUS SURFACE
A surface such as stone, rock or other materials which permits
some vertical transmission of water.
SOIL-COVER-COMPLEX METHOD
A method of runoff computation developed by the Coil Conservation
Service (now NRCS), and found in its publication "Urban Hydrology
for Small Watersheds," Technical Release No. 55, January 1975, revised
1986.
STORM FREQUENCY
The average interval in years over which a storm event of
a given precipitation volume can be expected to occur.
STORM SEWER
A sewer that carries intercepted surface runoff, street water
and other drainage but excludes domestic sewage and industrial waste.
STORMWATER
That portion of precipitation which runs over the land.
STORMWATER COLLECTION SYSTEM
Natural or man-made structures that collect and transport
stormwater through or from a drainage area to the point of final outlet,
including, but not limited to, any of the following: conduits and
appurtenant features, canals, channels, ditches, streams, culverts,
streets and pumping stations.
STORMWATER MANAGEMENT PLAN
The plan for managing stormwater runoff adopted by Allegheny
County and Westmoreland County as required by the Storm Water Management
Act.
STORMWATER STRUCTURES
Basins, pipes, swales, terraces, etc., designed and installed
to collect, transport, detain and/or retain stormwater.
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
A low-lying stretch of land which gathers or carries surface
water runoff.
TIME OF CONCENTRATION
The time, in hours, surface stormwater runoff takes to travel
from the hydraulically most distant point in the drainage basin to
the point under design consideration. This time is the combined total
of overland flow time and flow time in pipes or channels, if any.
WATERCOURSE
Any channel for conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
WATERSHED
The entire region or area drained by a river or other body
of water, whether natural or artificial. A "designated watershed"
is an area delineated by the Pennsylvania DEP and approved by the
Environmental Quality Board, for which counties are required to develop
watershed stormwater management plans.
WATERSHED STORMWATER MANAGEMENT PLAN
The plan for managing stormwater runoff throughout a designated
watershed adopted by Allegheny County and Westmoreland County as required
by the Pennsylvania Storm Water Management Act.