When used in this chapter, the following terms shall be defined
as set forth below:
ACCELERATED EROSION
The removal of the surface of the land through the combined
action of human activity and natural processes at a rate greater than
that which would occur because of the natural process alone.
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).
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;
changing of surface conditions by causing the surface to be more or
less impervious; land disturbance.
APPLICANT
A landowner, developer or other person who has filed an application
for approval to engage in any regulated activities at a project site
within Millcreek Township.
BEST MANAGEMENT PRACTICES (BMPs)
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: "nonstructural"
or "structural." "Nonstructural" BMPs are measures referred to as
operational and/or behavior-related practices that attempt to minimize
the contact of pollutants with stormwater runoff, whereas "structural"
BMPs are measures 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.
CHANNEL EROSION
The widening, deepening, and headward cutting of small channels
and waterways, due to erosion caused by moderate to large floods.
CISTERN
An underground reservoir or tank used for storing rainwater.
CONSERVATION DISTRICT
The Erie County Conservation District, which has the authority under a delegation agreement executed with the PaDEP to administer and enforce all or a portion of the regulations promulgated under 25 Pa. Code Chapter
102.
CULVERT
A structure with appurtenant works that carries a stream
and/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 refuse bank, fill or structure for highway,
railroad or other purposes which does or may impound water or another
fluid or semifluid.
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 and temporal distribution of precipitation
from a storm event measured in probability of occurrence (e.g., a
twenty-five-year storm) and duration (e.g., 24 hours), used in the
design and evaluation of stormwater management systems. Also see "return
period."
DESIGNEE
The agent of the Township and/or agent of the Board of Supervisors
involved with the administration, review or enforcement of any provisions
of this chapter by contract or memorandum of understanding.
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 BASIN
An impoundment structure designed to manage stormwater runoff
by temporarily storing the runoff and releasing it at a predetermined
rate.
DETENTION VOLUME
The volume of runoff that is captured and released into waters
of the commonwealth at a controlled rate.
DEVELOPER
The person(s), corporation, limited liability company, partnership,
association, or other entity or any responsible person therein or
agent therefor that undertakes any regulated activity under this chapter.
DEVELOPMENT
Any activity, construction, alteration, change in land use
or practice that affects stormwater runoff characteristics and/or
constitutes a regulated activity.
DEVELOPMENT SITE (SITE)
The specific tract of land for which a regulated activity
is proposed. Also see "project site."
DISCHARGE
The flow or rate of flow from a canal, conduit, channel or
other hydraulic structure.
DISTURBED AREA
An unstabilized land area where an earth disturbance activity
is occurring or has occurred.
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 toward it.
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," and "river basin."
B.
The area served by a sewer system receiving storm and surface
water, or by a watercourse.
DRAINAGE CONVEYANCE FACILITY
A stormwater management facility designed to convey stormwater
runoff and shall include streams, channels, swales, pipes, conduits,
culverts, storm sewers, etc.
DRAINAGE EASEMENT
A right granted by the owner of property to use private land
of another for stormwater management, drainage or conveyance purposes.
DRAINAGEWAY
Any natural or artificial watercourse, trench, ditch, pipe,
swale, channel or similar depression into which surface water flows.
EARTH DISTURBANCE ACTIVITY
A construction or other human activity which disturbs the
surface of the land, including but not limited to clearing and grubbing,
grading, excavations, embankments, land development, agricultural
plowing or filling, timber harvesting activities, road maintenance
activities, mineral extraction and the moving, depositing, stockpiling
or storing of soil, rock or earth materials.
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
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 Pa. Code Chapter
93, Water Quality Standards, Section 93.4b(b), relating to antidegradation.
EXISTING CONDITIONS
The initial condition of a project site prior to the proposed
construction. If the initial condition of the site is undeveloped
land and not forested, the land use shall be considered as "meadow"
unless the natural land cover is documented to generate lower curve
numbers or Rational "C" coefficient [to the extent these are authorized
by this chapter].
FEMA
The Federal Emergency Management Agency.
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 the commonwealth.
FLOOD FRINGE
The remaining portions of the one-hundred-year floodplain
outside of the floodway boundary.
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. Included are lands adjoining
a river or stream that have been or may be inundated by a one-hundred-year
flood. Also included are areas that comprise Group 13 Soils, as listed
in Appendix A of the PaDEP Technical Manual for Sewage Enforcement
Officers (as amended or replaced from time to time by PaDEP).
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 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 landward 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 tank, pond 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
To finish the surface of a roadbed, top of embankment or
bottom of excavation.
GROUNDWATER
Subsurface water occupying the saturation zone, from which
wells and springs are fed.
HEC-HMS MODEL CALIBRATED
[Hydrologic Engineering Center Hydrologic Modeling System]
A computer-based hydrologic modeling technique adapted to the watershed(s)
in Erie County for the Act 167 Plan. The model has been calibrated
by adjusting key model input parameters.
HIGH QUALITY WATERS
Surface water having quality, which exceeds levels necessary
to support propagation of fish, shellfish, and wildlife and recreation
in and on the water by satisfying Pa. Code Title 25, Chapter 93, Water
Quality Standards, Section 93.4b(a).
HYDROLOGIC SOIL GROUP (HSG)
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into one of four HSG (A, B, C, and D) according to
their minimum infiltration rate, which is obtained for bare soil after
prolonged wetting. The Natural Resource 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 interest may be identified
from a soil survey report from the local NRCS office or the Conservation
District.
IMPERVIOUS
Not allowing or allowing only with great difficulty the movement
of water; impermeable.
IMPERVIOUS SURFACE (IMPERVIOUS AREA)
A surface that prevents the infiltration of water into the
ground. Impervious surface (or areas) include, but is not limited
to: roofs, additional indoor living spaces, patios, garages, storage
sheds and similar structures, parking or driveway areas, and any new
streets and sidewalks. Any surface areas proposed to initially be
gravel or crushed stone shall be assumed to be impervious surfaces.
IMPOUNDMENT
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
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.
INFILTRATION STRUCTURE
A structure designed to direct runoff into the ground (e.g.,
french drains, seepage pits, seepage trench, etc.).
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 (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 buildings; 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.
C.
Development in accordance with Section 503(1.1) of the MPC.
MAIN STEM (MAIN CHANNEL)
Any stream segment or other runoff conveyance facility used
as a reach in the Erie County Act 167 watershed hydrologic model(s).
MAINTENANCE
The upkeep necessary for efficient operation of physical
properties.
MANNING EQUATION (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.
NATURAL STORMWATER RUNOFF REGIME
A watershed where natural surface configurations, runoff
characteristics and defined drainage conveyances have attained the
conditions of equilibrium.
NOAA ATLAS 14
Precipitation-Frequency Atlas of the United States, Atlas
14, Volume 2, U.S. Department of Commerce, National Oceanic and Atmospheric
Administration, National Weather Service, Hydrometeorological Design
Studies Center, Silver Spring, Maryland (2004).
NONPOINT SOURCE POLLUTION
Pollution that enters a water body from diffuse origins in
the watershed and does not result from discernible, confined, or discrete
conveyances.
NRCS
Natural Resource Conservation Service [previously Soil Conservation
Service (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, canals, and pipes
not under pressure.
OUTFALL
A.
Point where water flows from a conduit, stream, or drain;
B.
"Point source" as described in 40 CFR 122.2 at the point where
the municipality's storm sewer system discharges to surface waters
of the commonwealth.
OUTLET
Points of water disposal from a stream, river, lake, tidewater,
or artificial drain.
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.
PaDEP
The Pennsylvania Department of Environmental Protection.
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.
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.
PERSON
An individual, partnership, public or private association
or corporation, limited liability company, firm, trust, estate, municipality,
governmental unit, public utility or any other legal entity whatsoever
which is recognized by law as the subject of rights and duties. Whenever
used in any section prescribing or imposing a penalty, the term "person"
shall include the members of a partnership, the officers, members,
servants and agents of an association, officers, agents and servants
of a corporation, and the officers of a municipality or country, but
shall exclude any department, board, bureau or agency of the commonwealth.
PIPE
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
POINT SOURCE
Any discernible, confined, or discrete conveyance, including,
but not limited to: any pipe, ditch, channel, tunnel, or conduit from
which stormwater is or may be discharged, as defined in state regulations
at 25 Pa. Code § 92a.2.
PREDEVELOPMENT CONDITIONS
Predevelopment conditions shall be assumed to be those which
existed on the site at the time prior to commencement of any development
activities. Where a site has been developed previously and is proposed
to be redeveloped, the predevelopment coefficient for the developed
portion of the site shall be based upon an assumed 50% native land
cover (i.e., grass, trees, etc.) and 50% developed land cover (e.g.,
buildings, pavement, etc.).
PROJECT SITE
The specific area of land where any regulated activities
in the municipality are planned, conducted, or maintained.
QUALIFIED PROFESSIONAL
Any person licensed by the Pennsylvania Department of State
or otherwise qualified by law and meeting requirements of this chapter
to perform the work required by this chapter.
RATIONAL FORMULA
A rainfall-runoff relation used only to estimate peak flow
rates for design of conveyance facilities.
REDEVELOPMENT
Earth disturbance activities on land which has previously
been developed.
REGULATED ACTIVITIES
Any earth disturbance activities or any activities that involve
the alteration or development of land in a manner that may affect
stormwater runoff.
RELEASE RATE
The percentage of predevelopment peak rate of runoff from
a site or subwatershed area to which the postdevelopment peak rate
of runoff must be reduced to protect downstream areas.
RELEASE RATE DISTRICT
Those subwatershed areas in which postdevelopment flows must
be reduced to a certain percentage of predevelopment flows as required
by this chapter to meet the plan requirements and the goals of Act
167.
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.
RETENTION VOLUME/REMOVED RUNOFF
The volume of runoff that is captured and not released directly
into the surface waters of this commonwealth during or after a storm
event.
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; or stated in another way, the probability of a twenty-five-year
storm occurring in any one given year is 0.04 (i.e., a four-percent
chance).
RIPARIAN BUFFER
A vegetated area bordering perennial and intermittent streams
and wetlands, that serves as a protective filter to help protect streams
and wetlands from the impacts of adjacent land uses.
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.
ROAD MAINTENANCE
Earth disturbance activities within the existing road right-of-way,
such as grading and repairing existing unpaved road surfaces, cutting
road banks, cleaning or clearing drainage ditches, and other similar
activities. Road maintenance activities that do not disturb the subbase
of a paved road (such as milling and overlays) are not considered
earth disturbance activities.
ROOFTOP DETENTION
Temporary ponding and gradual release of stormwater falling
directly onto flat roof surfaces by incorporating controlled-flow
roof drains into building designs.
RUNOFF
Any part of precipitation that flows over the land surface.
RUNOFF CAPTURE VOLUME
The volume of runoff that is captured (retained) and not
released into surface waters of the commonwealth during or after a
storm event.
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
Soils or other materials transported by surface water as
a product of erosion.
SEDIMENT BASIN
A barrier, dam, retention or detention basin located and
designed to retain rock, sand, gravel, silt, or other material transported
by stormwater runoff.
SEDIMENT POLLUTION
The placement, discharge, or any other introduction of sediment
into waters of the commonwealth occurring from the failure to properly
design, construct, implement or maintain control measures and control
facilities in accordance with the requirements of this chapter.
SEDIMENTATION
The process by which mineral or organic matter is accumulated
or deposited by the movement of water.
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.
SEPARATE STORM SEWER SYSTEM
A conveyance or system of conveyances (including roads with
drainage systems, Township streets, catch basins, curbs, gutters,
ditches, man-made channels, or storm drains) primarily used for collecting
and conveying stormwater runoff.
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).
SPILLWAY (EMERGENCY)
A depression in the embankment of a pond or basin, or other
overflow structure, that is used to pass peak discharges greater than
the maximum design storm controlled by the pond or basin.
STATE WATER QUALITY REQUIREMENTS
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Title 25 of the Pennsylvania Code
and the Clean Streams Law.
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 also "return
period."
STORM SEWER
A system of pipes and/or open channels that convey intercepted
runoff and stormwater from other sources, but excludes domestic sewage
and industrial wastes.
STORMWATER
Runoff from the surface of the land resulting from precipitation,
snow, or ice melt.
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 HOTSPOT
A land use or activity that generates higher concentrations
of hydrocarbons, trace metals, or toxicants than are found in typical
stormwater runoff.
STORMWATER MANAGEMENT FACILITIES
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 MODEL (SWMM)
A dynamic rainfall-runoff simulation model used for single-event
or long-term (continuous) simulation of runoff quantity and quality
from primarily urban areas.
STORMWATER MANAGEMENT PLAN
The Erie County Stormwater Management Plan for managing stormwater
runoff in Erie County as required by Act 167 of 1978, known as the
Storm Water Management Act.
STREAM ENCLOSURE
A bridge, culvert, or other structure in excess of 100 feet
in length upstream to downstream which encloses a regulated waters
of the commonwealth.
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.
SUB-WATERSHED AREA
The smallest drainage unit of a watershed for which stormwater
management criteria has been established in the stormwater management
plan.
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.
TOWNSHIP ENGINEER
A professional engineer licensed in the Commonwealth of Pennsylvania,
duly appointed by the Township and/or retained by the Township to
assist in implementation of this chapter.
USDA
The United States Department of Agriculture.
WATERCOURSE
A channel or conveyance of surface water, such as a stream
or creek, having defined bed and banks, whether natural or artificial,
with perennial or intermittent flow.
WATERS OF THE 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 and
underground water, or parts thereof, whether natural or artificial,
within or on the boundaries of the Commonwealth of Pennsylvania.
WATERSHED
Area drained by a river, watercourse, or other surface water,
whether natural or artificial.
WETLAND
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 adapted for life in saturated soil conditions, including
swamps, marshes, bogs and similar areas. (The term includes but is
not limited to wetland areas listed in the State Water Plan, the U.S.
Forest Service Wetlands Inventory of Pennsylvania, the Pennsylvania
Coastal Zone Management Plan and a wetland area designated by a river
basin commission. This definition is used by the U.S. Environmental
Protection Agency and the U.S. Army Corps of Engineers.)