As used in this chapter, the following terms shall have the
meanings indicated:
American Association of State Highway and Transportation
Officials. The website home page for AASHTO is https://www.transportation.org/
Allegheny County Conservation District.
Allegheny County Health Department.
The Storm Water Management Act (Act of October 4, 1978, P.L.
864 No. 167; 32 P.S. §§ 680.1 to 680.17, as amended).
The plan for managing stormwater runoff throughout a designated
watershed adopted by Allegheny County as required by the Pennsylvania
Storm Water Management Act.
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.
A landowner, developer or other person who has filed an application
for approval to engage in any regulated activity at a project site
in the municipality.
A geologic formation, group of formations, or part of a formation
that contains sufficient saturated, permeable material to yield useful
quantities of groundwater to wells and springs.
To reduce the magnitude of the flow rate by increasing the
time it takes to release a specified volume of runoff (for example,
the one year, twenty-four-hour storm event). Attenuation is a method
of reducing the peak flow rates for post-development compared to the
peak flow rates in predevelopment.
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.
Activities, facilities, designs, measures or procedures used
to manage stormwater impacts from regulated activities, to meet state
water quality requirements, 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 refer
to operational and/or behavior-related practices that attempt to minimize
the contact of pollutants with stormwater runoff whereas structural
BMPs or measures are those that consist of a physical device or practice
that is installed 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, low-impact design, bioretention, wet ponds, permeable
paving, grassed swales, riparian or forested buffers, sand filters,
detention basins, and manufactured devices. Structural stormwater
BMPs are permanent appurtenances to the project site.
Cubic feet per second.
A natural or artificial watercourse that conveys continuously
or periodically flowing water.
Surface runoff from rainfall events, which converges and
flows primarily through water conveyance features such as swales,
gullies, waterways, channels or storm sewers and which exceeds the
maximum specified flow rates of filters or perimeter controls intended
to control sheet flow.
A series of holistic land development design practices 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 complementary 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.
A conservation district, as defined in section 3(c) of the
Conservation District Law [3 P.S. § 851(c)], which has the
authority under a delegation agreement executed with the Department
to administer and enforce all or a portion of the erosion and sediment
control program in this commonwealth.
The Pennsylvania Department of Environmental Protection.
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."
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 and are dry until the next rainfall event.
The prevention of, or to prevent, the discharge, directly
or indirectly, of a given volume of stormwater runoff into surface
waters by temporary storage.
See "project site."
(Verb) To release of water from a project, site, aquifer,
drainage basin or other point of interest. (Noun) The rate and volume
of flow of water such as in a stream, generally expressed in cubic
feet per second (volume per unit of time).
An unstabilized land area where an earth disturbance is occurring
or has occurred.
An artificial waterway for irrigation or stormwater conveyance.
That land area contributing runoff to a single point and
that is enclosed by a ridgeline.
All facilities and natural features used for the movement
of stormwater through and from a drainage area, including, but not
limited to, any and all of the following: conduits, pipes and appurtenant
features; channels, ditches, flumes, culverts, streets, swales, gutters
as well as all watercourses, water bodies and wetlands.
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; building construction;
the moving, depositing, stockpiling or storing of soil, rock or earth
materials.
A right of use of a specified portion of land of another
for a specified purpose.
A professional engineer duly appointed as the engineer for
municipality.
Environmental Protection Agency.
The wearing away of land surface by water or wind which occurs
naturally from weather or runoff but is often intensified by human
activity.
The dominant land cover during the five-year period immediately
preceding a proposed regulated activity.
Federal Emergency Management Agency.
Uppermost perennial tributary in a watershed that has not
yet confluence with another perennial stream. The confluence of two
first order streams forms a "second" order stream.
Any land area susceptible to inundation by water from any
natural source or delineated by applicable Federal Emergency Management
Agency (FEMA) maps and studies as being a special flood hazard area.
The channel of the watercourse and those portions of the
adjoining floodplains that is reasonably required to carry and discharge
the 100-year 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 100-year 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.
Planning and activities necessary for the management of forestland.
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 is the difference between the elevation of the
design flow in the emergency spillway (usually the 100-year peak elevation)
and the top elevation of the settled basin embankment (that is, top
of berm). The minimum freeboard shall be one foot.
Water that occurs in the subsurface and fills or saturates
the porous openings, fractures and fissures of underground soils and
rock units.
An area where land use or activities generate highly contaminated
runoff, with concentrations of pollutants in excess of those typically
found in stormwater.
A graph of discharge versus time for a selected point in
the drainage system.
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 Natural Resources Conservation Service (NRCS) of the
U.S. Department of Agriculture 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.
The study of the properties, distribution, circulation and
effects of water on the earth's surface, soil and atmosphere.
See "impervious surface."
A surface (area), which has been compacted or covered with
a layer of material so that it is resistant to infiltration by water.
It includes semipervious surfaces such as compacted clayey soils,
as well as most conventionally surfaced streets, roofs, sidewalks,
parking lots, and other similar surfaces. "Net increase of impervious
surface" refers to the difference between the existing impervious
coverage and the total impervious surface proposed.
Movement of surface water into the soil, where it is absorbed
by plant roots, evaporated into the atmosphere, or percolates downward
to recharge groundwater.
The depth of accumulated rainfall per unit of time.
A defined channel in which surface water is absent during
a portion of the year as groundwater levels drop below the channel
bottom.
A type of topography or landscape characterized by surface
depressions, sinkholes, rock pinnacles/uneven bedrock surface, underground
drainage, and caves. Karst is formed on carbonate rocks, such as limestone
or dolomite.
Inclusive of any or all of the following meanings:
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 building; or 2) the division or allocation of land or space 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;
Any subdivision of land;
Development in accordance with Section 503(1.1) of the Pennsylvania
Municipalities Planning Code.[1]
A low earthen berm constructed perpendicular to the direction
of slope and extending across the width of the slope for the purpose
of intercepting surface runoff and spreading it behind the berm to
enhance infiltration and reduce erosion and runoff from the slope.
The purpose of a level spreader is to prevent concentrated, erosive
flows from occurring and to spread out stormwater runoff uniformly
over the ground as sheet flow.
The total amount (generally measured in pounds or kilograms
per acre per year) of material (sediment, nutrients, oxygen-demanding
material, or other chemicals or compounds) brought into a lake, stream
or water body by inflowing streams, runoff, direct discharge through
pipes, groundwater, the air (aerial or atmospheric deposition) and
other sources over a specific period of time (often annually).
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, evaporate, 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.
The action taken to restore or preserve the as-built functional
design of any facility or system.
A natural ground cover with less than one viable tree of
a DBH of six inches or greater per 1,500 square feet within 10 years
of application; a cover condition for which SCS curve numbers have
been assigned or to which equivalent Rational Method runoff coefficients
have been assigned.
Municipal separate storm sewer system.
The Borough of Etna.
Created in 1972 under the Clean Water Act to authorize discharges
to local receiving waters only pursuant to governmental permits, in
an effort to reduce point source and non-point source pollutants.
Any activity regulated by this chapter that is not considered
a redevelopment as defined in this chapter.
National Oceanic and Atmospheric Administration.
Passive site design approaches or regulatory approaches that
positively impact water quality and reduce or minimize the generation
of stormwater runoff without requiring the construction of specific
or discrete stormwater management control structures.
Natural Resources Conservation Service.
Any natural or man-made watercourse or conduit in which water
flows with a free surface.
Also known as swales, grass channels, and biofilters. These
systems are used for the conveyance, retention, infiltration and filtration
of stormwater runoff.
Pennsylvania Association of Conservation Districts.
Pennsylvania Department of Environmental Protection.
A ground cover of grassland or range with continuous forage
for grazing and greater than 75% ground cover and lightly or only
occasionally grazed; a cover condition for which the Natural Resources
Conservation Service curve numbers have been assigned or to which
equivalent Rational Method runoff coefficients have been assigned.
The maximum rate of stormwater runoff from a specific storm
event.
Pennsylvania Department of Transportation.
The rate of movement of water under hydrostatic pressure
through interstices of rock or soil. For stormwater analysis, it is
typically measured as a distance per unit of time (e.g., inches per
hour).
Any area not defined as impervious.
The ground cover assumption used when analyzing the stormwater
runoff characteristics of a drainage area prior to the proposed development.
The specific area of land where any regulated activities
in the municipality are planned, conducted or maintained.
Any person licensed by the Pennsylvania Department of State
or otherwise qualified by law to perform the work required by the
chapter.
The depth of accumulated rainfall per unit of time.
Volume per unit of time.
Any water bodies, watercourses or wetlands into which surface
waters flow.
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
An existing, developed property containing structures and/or
impervious surfaces from prior development as of or after the date
of adoption of this chapter that is proposed for reconstruction activities
involving the demolition or partial demolition of the property. In
the case that these structures and impervious surfaces have been removed,
it must have been legally done within five years prior to the application
being made.
Any earth disturbances or any activities that involve the
alteration or development of land in a manner that may affect post-construction
stormwater runoff.
Activity involving earth disturbance subject to regulation
under 25 Pa. Code Chapters 92a, Chapter 102, or the Clean Streams
Law.
The percentage of predevelopment peak rate of runoff from
a watershed subarea (as delineated in the Act 167 watershed plan),
which defines the allowable post-development peak discharge from any
development site in that subarea.
An impoundment designed to collect and retard stormwater
runoff by temporarily storing the runoff and releasing it at a predetermined
rate. Retention basins may also be designed to permanently retain
additional stormwater runoff. Retention basins are designed to retain
a permanent pool of water during dry weather.
The prevention of direct discharge of stormwater runoff into
receiving waters or water bodies by temporary or 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.
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.
Pertaining to anything connected with or immediately adjacent
to the banks of a stream or other body of water.
An area of land adjacent to a body of water and managed to
maintain the integrity of stream channels and shorelines to: 1) reduce
the impact of upland sources of pollution by trapping, filtering and
converting sediments, nutrients and other chemicals; and 2) supply
food, cover and thermal protection to fish and other wildlife.
"See stormwater."
Soil Conservation Service. Now the Natural Resources Conservation
Service.
Fragmented material that originated from weathering rocks
and decomposing organic material that is transported by, suspended
in, and eventually deposited in the streambed.
Occurs when sediment particles that have been suspended within
flowing water are deposited on the stream bottom or floodplain.
A flow process associated with broad, shallow water movement
on sloping ground surfaces that is not channelized or concentrated.
This model is based on small storm hydrology and pollutant
runoff from urban land uses. Pollutant sources are identified and
both structural and nonstructural stormwater practices can be accounted
for in the model.
Those areas identified by the Federal Emergency Management
Agency (FEMA), Federal Insurance Administration (FIA) as floodway
area (FW), flood fringe area (FF), and general floodplain area (FA);
where determined by the municipality, identified alluvial soils may
be included as well.
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Pennsylvania Code Title 25 and the
Clean Streams Law.
The storm of a specific duration, intensity and frequency.
Abbreviated as SWM BMPs or BMPs throughout this chapter.
The Pine Creek, Deer Creek, Squaw Run, and Girty's Run
Stormwater Management Plan for managing stormwater runoff, adopted
by the County of Allegheny as required by the Act of October 4, 1978,
P.L. 864 (Act 167), as amended, and known as the "Storm Water Management
Act" if municipalities have drainage in these watersheds.
The designed and/or constructed features which infiltrate,
treat, collect, convey, channel, store, inhibit or divert the movement
of stormwater; such practices include structural and nonstructural
practices.
Drainage runoff from the surface of the land resulting from
precipitation or snow or ice melt.
Any measures that require the design and construction of
a facility to help reduce or eliminate a non-point source of pollution
and control stormwater.
Anything constructed or installed with a fixed location on
the ground or attached to something having a fixed location on the
ground.
A portion of the watershed (basin) that has similar hydrological
characteristics and drains to a common point.
As defined in the Pennsylvania Municipalities Planning Code,
Act of July 31, 1968, P.L. 805, No. 247.[2]
The top elevation of graded and compacted earth underlying
roadway pavement.
An artificial or natural waterway which may contain contiguous
areas of standing or flowing water only following a rainfall event,
or is planted with or has stabilized vegetation suitable for soil
stabilization, stormwater treatment and nutrient uptake, or is designed
to take into account the soil erodibility, soil percolation, slope,
slope length, and contributing drainage area so as to prevent erosion
and reduce the pollutant concentration of any discharge.
EPA developed this model for analyzing stormwater quantity
and quality associated with runoff from urban areas. Both single event
and continuous simulation can be performed on catchments having storm
sewers, or combined sewers and natural drainage, for prediction of
flows, stages and pollutant concentrations. Information on SWMM is
available at https://www.epa.gov/waterdata/epas-stormwater-management-model-swmm.
Total area of the parcel(s) being developed.
United States Department of Agriculture.
United States Department of Transportation Federal Highway
Administration.
Any natural or artificial pond, lake, reservoir or other
area which ordinarily or intermittently contains water, and which
has a discernible shoreline and receives surface water flow.
The uppermost level of saturation of pore space or fractures
by subsurface water in an aquifer. "Seasonal high-water table" refers
to a water table that rises and falls with the seasons due either
to natural or man-made causes.
A permanent or intermittent stream or other body of water,
whether natural or man-made, which gathers or carries surface water.
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 this commonwealth.
Region or area drained by a river, watercourse or other surface
water of this commonwealth.
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.
Land areas that are inundated or saturated by surface water
or groundwater with 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 and similar areas); or areas
that are defined and delineated in accordance with the Federal Manual
for Identifying and Delineating Jurisdictional Wetlands, dated January
10, 1989, and as may be amended from time to time; or as further defined
and delineated by the United States Army Corps of Engineers, the United
States Environmental Protection Agency, or the Pennsylvania Department
of Environmental Protection.
A natural ground cover with more than one viable tree of
a DBH (diameter at breast height) of six inches or greater per 1,500
square feet, which existed within 10 years of application; a cover
condition for which SCS curve numbers have been assigned or to which
equivalent Rational Method runoff coefficients have been assigned.
