Definitions. As used in this Part 2, the following terms shall have
the meanings indicated:
ACT
The Stormwater 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).
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, land clearing,
plowing, disking, harrowing, planting, 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 or developer (including his/her heirs, successors
and assigns), as defined by the Pennsylvania Municipalities Planning
Code, Act 247 of 1968, as amended by Act 170 of 1988, as further amended
by Act 209 of 1990 and Act 131 of 1992, who has filed an application
for development within the Borough of Baldwin.
BOROUGH ENGINEER
A professional engineer registered in the Commonwealth of
Pennsylvania specializing in civil engineering and appointed by the
Borough of Baldwin.
CHANNEL
A 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.
COUNTY
Allegheny County, Pennsylvania.
CULVERT
A closed conduit for the free passage of surface drainage
under a highway, railroad, canal or other embankment.
DEPARTMENT
The Allegheny County Planning Department.
DESIGN CRITERIA
(1)
Engineering guidelines specifying construction details and materials.
(2)
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 recurrence (e.g., twenty-five-year storm) and duration
(e.g., 24 hours), and used in computing stormwater management control
systems.
DETENTION
The slowing, dampening, or attenuating of runoff entering
the natural drainage pattern or storm drainage system by temporarily
holding water on a surface area such as detention basins, reservoirs,
on roof tops, in streets, parking lots, or within the drainage system
itself, and releasing the water at a desired rate of discharge.
DETENTION BASIN
A basin designed to retard stormwater runoff by temporarily
storing the runoff and releasing it at a predetermined rate. A "detention
basin" can be designed to drain completely after a storm event, or
it can be designed to contain a permanent pool of water, in which
case it is called a "retention basin."
DEVELOPMENT
Any activity, construction, alteration, change in land use
or similar action that affects stormwater runoff characteristics.
DEVELOPMENT SITE
A lot, parcel or tract of land on which development is taking
place or is proposed.
DISCHARGE
Rate of flow, specifically fluid flow; a volume of fluid
flowing from a conduit or channel, or being released from detention
storage, per unit of time; commonly expressed as cubic feet per second
(cfs), million gallons per day (mgd), gallons per minute (gpm). See
also "rate of runoff".
DRAINAGE
Interception and removal of excess surface water or groundwater
from land by artificial or natural means.
DRAINAGE AREA
The contributing land area to a single drainage basin, expressed
in acres, square miles, or other units of area; also called a "catchment
area", "watershed", or "river basin"; the land area served by a drainage
system or by a watercourse receiving storm and surface water, also
called "subarea".
DRAINAGE BASIN
The land area from which water is carried off by a natural
drainage system; also called a "watershed" or "catchment area".
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, glaciers, winds
and waves.
EROSION CONTROL
The application of measures to reduce erosion of land surfaces.
FLOODPLAIN
A normally dry land area adjacent to stream channels that
is susceptible to inundation by overbank stream flows. For regulatory
purposes, the Pennsylvania Flood Plain Management Act (Act of October
4, 1978, P.L. 851, No. 166) and regulations pursuant to the Act define the floodplain
as the area inundated by a one-hundred-year flood and delineated on
a map by FEMA (Federal Emergency Management Agency) or by the applicant
in accordance with Borough ordinance requirements.
FOREST MANAGEMENT or TIMBER OPERATIONS
Planning and activities necessary for the management of forestland.
These include conducting a timber inventory, preparation of forest
management plans, silvicultural treatment, cutting budgets, logging
road design and construction, timber harvesting, site preparation,
and reforestation.
GROUND WATER
Subsurface water occupying the saturation zone, from which
wells and springs are fed.
GROUND WATER RECHARGE
Replenishment of ground water naturally by precipitation
or runoff or artificially by spreading or injection.
HYDRAULICS
The branch of science concerned with the mechanics of fluids,
especially liquids. As applied in stormwater management, the study
of the characteristics of water flow in, and conveyance capacity of,
a watercourse, considering such factors as depth, velocity and turbulence.
HYDROGRAPH
A graph showing the quantity of runoff at a specific point
in time during a rainfall event.
HYDROLOGIC SOIL GROUP
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into four HSGs (A, B, C, and D) according to their
minimum infiltration rate, which is obtained for bare soil after prolonged
wetting. The NRCS defines the four groups and provides a list of most
of the soils in the United States and their group classification.
The soils in the area of the development site may be identified from
a soil survey report that can be obtained from local NRCS offices
or conservation district offices. Soils become less pervious as the
HSG varies from A to D (NRCS).
HYDROLOGY
The science dealing with the waters of the earth and their
distribution and circulation through the hydrosphere (above, on or
within the earth). Engineering hydrology deals with the application
of hydrologic concepts to the design of projects for use and control
of water, as well as the calculation of the rates of stormwater runoff.
INFILTRATION
(1)
The flow or movement of water through the interstices or pores
of a soil or other porous medium.
(2)
The absorption of liquid by the soil.
LAND DEVELOPMENT
Any of the following activities:
(1)
The improvement of one lot or two or more contiguous lots, tracts
or parcels or land for any purpose involving:
(a)
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
(b)
The division or allocation of land or space, whether initially
or cumulatively, between or among two or more existing or prospective
occupants by means or, for the purpose of streets, common areas, leaseholds,
condominiums, building groups or other features.
LAND DISTURBANCE
Any activity involving grading, tilling, digging or filling
or stripping of vegetation; or any other activity which causes land
to be exposed to the danger of erosion or changed water flow characteristics.
MAINTENANCE
The upkeep necessary for efficient operation of stormwater
structures and facilities.
MUNICIPALITY
The Borough of Baldwin, Allegheny County, Pennsylvania.
NATURAL STORM WATER RUNOFF REGIME
A watershed where natural surface configurations, runoff
characteristics and defined drainage conveyances have attained the
conditions of equilibrium.
OUTFALL
The points at which stormwater runoff leaves streams, storm
sewers, swales, or other well defined natural or artificial drainage
features, as well as areas of dispersed overland flows within the
site and/or leaving the site.
OUTLET STRUCTURE
A structure designed to control the volume of stormwater
runoff from a detention or retention facility during a specific length
of time.
OWNER
The person or association which is responsible for the care
of the structure(s) described.
PADEP
Pennsylvania Department of Environmental Protection.
PERFORMANCE STANDARD
A standard which establishes an end result or outcome which
is to be achieved but does not prescribe specific means for achieving
it. A specification standard, in contrast, is one which prescribes
the exact characteristics to be used, leaving little choice to the
applicant. The allowable release rate is an example of a performance
standard; the design standards for storm sewers are specifications
standards.
PERSON
An individual, partnership, public or private association
or corporation, firm, trust, estate, municipality, government unit,
public utility or any legal entity whatsoever which is recognized
by law as the subject of rights and duties.
PERVIOUS MATERIAL
Material which permits the passage or entrance of water or
other liquid. (i.e., grass, earth, stone, and trees).
POINT OF INTEREST
A point of hydrologic and/or hydraulic concern such as a
bridge, culvert, or channel section, for which the rate of runoff
is computed or measured.
PROJECT SITE
The specific area of land where any regulated earth disturbance
activities in the municipality are planned, conducted or maintained.
RATE OF RUNOFF
Instantaneous measurement of water flow expressed as a unit
of volume per unit of time, also referred to as discharge. Usually
stated in cubic feet per second (cfs) or gallons per minute (gpm).
REGULATED EARTH DISTURBANCE ACTIVITY
Earth disturbance activity one acre or more with a point
source discharge to surface waters or the municipality's storm
sewer system, or five acres or more regardless of the planned runoff.
This includes earth disturbance on any portion of, part, or during
any stage of, a larger common plan of development. This only includes
road maintenance activities involving 25 acres or more or earth disturbance.
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 BASIN
A type of detention basin designed to contain a permanent
pool of water.
RETURN PERIOD
The average interval in years over which an event of a given
magnitude can be expected to recur.
ROUTING
Using an inflow hydrograph to simulate the water flow through
a storage facility creating storage data and an outflow hydrograph.
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 manmade landscape
alterations.
SCS
Soil Conservation Service, United States Department of Agriculture.
SEDIMENT
Solid material, both mineral and organic, that is in suspension,
is being transported, or has been removed from its site or origin
by air, water, gravity, or ice and has come to rest on the earth's
surface.
SEDIMENTATION
The process by which mineral or organic matter is accumulated
or deposited by moving water, wind or gravity.
SOIL-COVER COMPLEX METHOD
A method of runoff computation developed by the United States
Soil Conservation Service and specifically found in its publication,
Urban Hydrology for Small Watersheds, Technical Release No. 55, SCS
(or most current edition). There are several runoff models which implement
this methodology and it is not limited to the TR-55.
STORM SEWER
A pipe, culvert or underground open channel that carries
intercepted surface runoff, street water, and other wash waters, or
drainage, but excludes domestic sewage and industrial wastes.
STORMWATER COLLECTION/CONVEYANCE SYSTEM
Natural or engineered structures which 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 appurtenance
features, canals, channels, ditches, streams, culverts, streets and
pumping stations.
STORMWATER MANAGEMENT SITE PLAN
The plan prepared by the developer or his representative
indicating how stormwater runoff will be managed at the development
site in accordance with this Part 2. Stormwater management site plan
will be designated as SWM site plan throughout this Part.
STORMWATER RUNOFF
Waters resulting from snow melt or precipitation within a
drainage basin, flowing over the surface of the ground, collected
in channels and conduits, and carried by receiving streams.
SUBAREA
A portion of the watershed that has similar hydrological
characteristics and drains to a common point. Also called a drainage
area.
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 devises, transfer of 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.
UPLAND
The higher parts of a region or tract of land.
VOLUME OF STORMWATER RUNOFF
Quantity of water normally measured cubic feet or acre-feet,
measured or determined analytically from runoff coefficients; rainfall/runoff
ratios; and areas underneath hydrographs.
WATERCOURSE (WATERWAY)
Any channel of conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
WATERS OF THIS COMMONWEALTH
Rivers, streams, creeks, rivulets, impoundments, ditches,
watercourses, storm sewers, lakes, dammed water, wetlands, ponds,
springs and other bodies or channels of conveyance of surface water,
or parts thereof, whether natural or artificial, within or on the
boundaries of this Commonwealth. (Source: The Clean Streams Law).
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 PaDEP and approved by the Environmental Quality
Board as one for which the county is required to prepare a watershed
stormwater management plan in accordance with the Pennsylvania Stormwater
Management Act. Also called a drainage basin.
WETLANDS
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 adopted for life in saturated soil conditions, including
swamps, marshes, bogs and similar areas. The term includes, but is
not limited to, wetland area listed in the State Water Plan, the United
States Fish and Wildlife Service Wetlands Inventory Maps, and the
Pennsylvania Coastal Zone Management Plan and any wetland area designated
by a river basin commission.