For the purposes of this chapter, certain terms and words used
herein shall be interpreted as follows:
A.
Words used in the present tense include the future tense; the singular
number includes the plural, and the plural number includes the singular;
words of masculine gender include feminine gender; and words of feminine
gender include masculine gender.
B.
The word "includes" or "including" shall not limit the term to the
specific example, but is intended to extend its meaning to all other
instances of like kind and character.
C.
The word "person" includes an individual, firm, association, organization,
partnership, trust, company, corporation, unit of government, or any
other similar entity.
D.
The words "shall" and "must" are mandatory; the words "may" and "should"
are permissive.
E.
The words "used" or "occupied" include the words "intended, designed,
maintained, or arranged to be used, occupied, or maintained."
As used in this chapter, the following terms shall have the
meanings indicated:
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 processes alone.
The work of producing crops and raising livestock including
tillage, plowing, disking, harrowing, pasturing, nursery and sod operations,
excluding greenhouse structures, and installation of conservation
measures. Construction of new buildings or impervious area is not
considered an agricultural activity.
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.
A landowner or other person who has filed an application to the municipality for approval to engage in any regulated activity defined in § 257-5 of this chapter.
Engineering or site drawings maintained by the contractor
as he constructs the project and upon which he documents the actual
locations of the building components and changes to the original contract
documents. These documents, or a copy of same, are turned over to
the Municipal Engineer at the completion of the project.
The channel at the top-of-bank or point from where water
begins to overflow onto a floodplain.
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.
A stormwater retention area that utilizes woody and herbaceous
plants and soils to remove pollutants before infiltration occurs.
Activities, facilities, designs, measures, or procedures
used to manage stormwater impacts from regulated activities, to meet
state water quality requirements, to promote infiltration, 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.
See "riparian buffer."
An open drainage feature through which stormwater flows.
Channels include, but shall not be limited to, natural and man-made
drainageways, swales, streams, ditches, canals, and pipes flowing
partly full.
The widening, deepening, or headward cutting of channels
and waterways caused by stormwater runoff or bankfull flows.
An underground reservoir or tank for storing rainwater.
The Delaware County Conservation District.
A facility or structure used for the transportation or transmission
of something from one place to another.
A structure with its appurtenant works, which carries water
under or through an embankment or fill.
A man-made barrier, together with its appurtenant works,
constructed for the purpose of impounding or storing water or another
fluid or semifluid. A dam may include a refuse bank, fill, or structure
for highway, railroad, or other purposes which impounds or may impound
water or another fluid or semifluid.
The Pennsylvania Department of Environmental Protection.
The agent of the Delaware County Planning Commission, Delaware
County Conservation District, and/or agent of the governing body involved
with the administration, review, or enforcement of any provisions
of this chapter by contract or memorandum of understanding.
A Pennsylvania registered professional engineer, registered
landscape architect, registered professional land surveyor trained
to develop SWM site plan, or any person licensed by the Pennsylvania
Department of State or qualified by law to perform the work required
by this chapter.
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.
The prevention of, or to prevent, the discharge, directly
or indirectly, of a given volume of stormwater runoff into surface
waters by temporary storage.
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 soon after
a rainfall event and become dry until the next rainfall event.
A person who seeks to undertake any regulated earth disturbance
activities at a project site in the municipality.
Any human-induced change to improved or unimproved real estate,
whether public or private, including, but not limited to, land development,
construction, installation, or expansion of a building or other structure,
land division, street construction, drilling, and site alteration
such as embankments, dredging, grubbing, grading, paving, parking
or storage facilities, excavation, filling, stockpiling, or clearing.
As used in this chapter, development encompasses both new development
and redevelopment.
The specific tract or parcel of land where any regulated activity set forth in § 257-5 is planned, conducted, or maintained.
The outside bark diameter at breast height which is defined
as 4.5 feet (1.37 meters) above the forest floor on the uphill side
of the tree.
Drainage discharge that is not confined to a single point
location or channel, including sheet flow or shallow concentrated
flow.
The point of discharge for a stormwater facility.
Unstabilized land area where an earth disturbance activity
is occurring or has occurred.
A man-made waterway constructed for irrigation or stormwater
conveyance purposes.
That portion of the property line of the lot, tract, or parcels
of land being developed, located such that overland or pipe flow from
the project site would be directed towards it by gravity.
A stormwater management facility designed to transport stormwater
runoff that includes channels, swales, pipes, conduits, culverts,
and storm sewers.
A right granted by a landowner to a grantee allowing the
use of private land for stormwater management purposes.
A permit issued by the municipality after the stormwater
management site plan has been approved.
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 conveyance area that is used to pass peak discharge greater
than the maximum design storm controlled by the stormwater facility.
A structure or activity that changes, expands, or diminishes
the course, current, or cross-section of a watercourse, floodway,
or body of water.
The process by which the surface of the land, including water/stream
channels, is worn away by water, wind, or chemical action.
A plan that is designed to minimize accelerated erosion and
sedimentation. Said plan must be submitted to and approved by the
appropriate conservation district before construction can begin.
Surface waters of high quality which satisfy Pennsylvania
Code Title 25, Environmental Protection, Chapter 93, Water Quality
Standards, § 93.4b(b) (relating to anti-degradation).
The initial condition of a project site prior to the proposed
alteration. If the initial condition of the site is undeveloped land,
the land use shall be considered as "meadow" unless the natural land
cover is proven to generate a lower curve number or Rational "c" value,
such as forested lands.
Federal Emergency Management Agency.
A situation where the greatest possible profit cannot be
fully realized from development/redevelopment on a given parcel of
land due to added costs or burdens associated with the design, construction,
and/or maintenance of stormwater structures, facilities, buffers and/or
setbacks.
A temporary condition of partial or complete inundation of
land areas from the overflow of streams, rivers, and other waters
of this commonwealth.
Any land area susceptible to inundation by water from any
natural source or as delineated by the applicable Department of Housing
and Urban Development, Federal Insurance Administration Flood Hazard
Boundary Map, as being a special flood hazard area.
The channel of a 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-bank.
The study of landforms associated with river channels and
the processes that form them.
Planning and associated activities necessary for the management
of forest lands. These include timber inventory and preparation of
forest management plans, silvicultural treatment, cutting budgets,
logging road design and construction, timber harvesting, and reforestation.
A vertical distance between the elevation of the design high
water and the top of a dam, levee, tank, basin, swale, or diversion
berm. The space is required as a safety margin in a pond or basin.
A natural or man-made waterway, usually broad and shallow,
covered with erosion-resistant grasses used to convey surface water.
Water beneath the earth's surface that supplies wells
and springs and is often between saturated soil and rock.
The replenishment of existing natural underground water supplies
from rain or overland flow.
The U.S. Army Corps of Engineers, Hydrologic Engineering
Center (HEC) - Hydrologic Modeling System (HMS). This model was used
to model the Darby-Cobbs and Crum Creek watersheds during the Act
167 plan development and was the basis for the standards and criteria
of this chapter.
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).
Areas where land use or activities generate highly contaminated
runoff with concentrations of pollutants in excess of those typically
found in stormwater.
A graph representing the discharge of water versus time for
a selected point in the drainage system.
The hydrologic cycle or balance that sustains quality and
quantity of stormwater, base flow, storage, and groundwater supplies
under natural conditions.
A classification of soils by the Natural Resources Conservation
Service (NRCS), formerly the Soil Conservation Service (SCS), 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.
A surface that prevents the infiltration of water into the
ground. Impervious surfaces include, but are not limited to, streets,
sidewalks, pavements, driveway areas, or roofs. Any surface areas
designed to be gravel or crushed stone shall be regarded as impervious
surfaces.
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
Development that occurs on smaller parcels that remain undeveloped
but are within or in very close proximity to urban or densely developed
areas. Infill development usually relies on existing infrastructure
and does not require an extension of water, sewer, or other public
utilities.
Movement of surface water into the soil, where it is absorbed
by plant roots, evaporated into the atmosphere, or percolated downward
to recharge groundwater.
A structure designed to direct runoff into the underground
water (e.g., French drains, seepage pits, or seepage trenches).
The flow entering the stormwater management facility and/or
BMP.
The upstream end of any structure through which water may
flow.
A stream that flows only part of the time. Flow generally
occurs for several weeks or months in response to seasonal precipitation
or groundwater discharge.
The lowest surface, the floor or bottom of a culvert, drain,
sewer, channel, basin, BMP, or orifice.
Any of the following activities:
The improvement of one lot or two or more contiguous lots, tracts,
or parcels of land for any purpose involving:
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
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;
A subdivision of land;
Development in accordance with Section 503(1.1) of the Pennsylvania
Municipalities Planning Code.[1]
A soil horizon or condition in the soil profile or underlying
strata that includes one of the following:
A seasonal high water table, whether perched or regional, determined
by direct observation of the water table or indicated by soil mottling.
A rock with open joints, fracture or solution channels, or masses
of loose rock fragments, including gravel, with insufficient fine
soil to fill the voids between the fragments.
A rock formation, other stratum, or soil condition that is so
slowly permeable that it effectively limits downward passage of water.
A designated parcel, tract, or area of land established by
a plat or otherwise as permitted by law and to be used, developed,
or built upon as a unit.
Any stream segment or other runoff conveyance used as a reach
in watershed-specific hydrologic models.
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.
The maximum (largest) design storm that is controlled by
the stormwater facility.
A professional engineer licensed as such in the Commonwealth
of Pennsylvania, duly appointed as the engineer for a municipality,
planning agency, or joint planning commission.
Township of Marple, Delaware County, Pennsylvania.
Predevelopment condition.
See "hydrologic regime."
Undisturbed surface area or depression where stormwater collects
and a portion of which infiltrates and replenishes the underground
and groundwater.
Pollution that enters a water body from diffuse origins in
the watershed and does not result from discernible, confined, or discrete
conveyances.
Water flowing in stormwater collection facilities, such as
pipes or swales, which is not the result of a rainfall event or snowmelt.
Methods of controlling stormwater runoff quantity and quality,
such as innovative site planning, impervious area and grading reduction,
protection of natural depression areas, temporary ponding on site,
and other techniques.
National Pollutant Discharge Elimination System, the federal
government's system for issuance of permits under the Clean Water
Act, which is delegated to PADEP in Pennsylvania.
Natural Resource Conservation Service (previously SCS).
A conveyance channel that is not enclosed.
"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.
The flow exiting the stormwater management facility and/or
BMP.
Points of water disposal to a stream, river, lake, tidewater,
or artificial drain.
The parcel of land from which a land development or subdivision
originates, determined from the date of municipal adoption of this
chapter.
Involves the use of parking areas as temporary impoundments
with controlled release rates during rainstorms.
The maximum rate of stormwater runoff from a specific storm
event.
The Best Management Practices Manual published by the Pennsylvania
Department of Environmental Protection. The manual is to supplement
federal and state regulations and the Department of Environmental
Protection's Comprehensive Stormwater Management Policy that
emphasizes effective site planning as the preferred method of managing
runoff while also providing numerous examples of BMPs that can be
employed in Pennsylvania to further avoid and minimize flooding and
water resource problems.
Any area not defined as impervious.
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
The Planning Commission of Marple Township.
Any discernible, confined, and 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 Pennsylvania Code § 92.1.
Period after construction during which disturbed areas are
stabilized, stormwater controls are in place and functioning, and
all proposed improvements in the approved land development plan are
completed.
Prior to commencing construction activities.
Undeveloped/natural condition.
Techniques employed in stormwater BMPs to provide storage or filtering to trap coarse materials and other pollutants before they enter the system, but not necessarily designed to meet the water quality volume requirements of § 257-15.
The specific area of land where any regulated activities
in the municipality are planned, conducted, or maintained.
See "design professional (qualified)."
A rainfall-runoff relation used to estimate peak flow.
Any stream segment or other runoff conveyance used in the
watershed-specific hydrologic models.
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
Demolition and subsequent rebuilding of impervious surface.
Original documents revised to suit the as-built conditions
and subsequently provided by the engineer to the client. The engineer
reviews the contractor's as-builts against his/her own records
for completeness, then either turns these over to the client or transfers
the information to a set of reproducibles, in both cases for the client's
permanent records.
Any development that requires demolition or removal of existing
structures or impervious surfaces at a site and replacement with new
impervious surfaces. Maintenance activities such as top-layer grinding
and repaving are not considered to be redevelopment. Interior remodeling
projects and tenant improvements are also not considered to be redevelopment.
Any earth disturbances activities or any activities that
involve the alteration or development of land in a manner that may
affect stormwater runoff, including redevelopment.
Activity involving earth disturbance subject to regulation
under 25 Pennsylvania Code, Chapters 92, Chapter 102, or the Clean
Streams Law.[2]
The percentage of existing conditions peak rate of runoff
from a site or subarea to which the proposed conditions peak rate
of runoff must be reduced to protect downstream areas.
Resurfacing of the impervious surface that does not involve
reconstruction of an existing paved (impervious) surface.
Reconstruction of and full replacement of an existing paved
(impervious) surface.
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, and/or evaporation processes and which
generally have residence times of less than three days.
A structure in which stormwater is stored and not released
during the storm event. Retention basins are designed for infiltration
purposes and do not have an outlet.
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.
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:
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.
Earth disturbance activities within the existing road cross-section,
such as grading and repairing existing unpaved road surfaces, cutting
road banks, cleaning or clearing drainage ditches, and other similar
activities.
A drainage conduit or pipe that collects water runoff from
a roof and leads it away from the structure.
The temporary ponding and gradual release of stormwater falling
directly onto flat roof surfaces using controlled-flow roof drains
in building designs.
Any part of precipitation that flows over the land surface.
Subdivision and Land Development Ordinance.[3]
Soil or other materials transported by surface water as a
product of erosion.
A barrier, dam, or retention or detention basin located and
designed in such a way as to retain rock, sand, gravel, silt, or other
material transported by water during construction.
The placement, discharge, or any other introduction of sediment
into the waters of the commonwealth.
The process by which mineral or organic matter is accumulated
or deposited by the movement of water or air.
An area of excavated earth filled with loose stone or similar
coarse material into which surface water is directed for infiltration
into the underground water.
A conveyance or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters,
ditches, man-made channels, or storm drains) primarily used for collecting
and conveying stormwater runoff.
Stormwater runoff flowing in shallow, defined ruts prior
to entering a defined channel or waterway.
A flow process associated with broad, shallow water movement
on sloping ground surfaces that is not channelized or concentrated.
A method of runoff computation developed by NRCS that is
based on relating soil type and land use/cover to a runoff parameter
called curve number (CN).
The zone through which contaminants, if present, are likely
to migrate and reach a drinking water well or surface water intake.
Watersheds that have been designated by PADEP as EV or HQ
waters.
A conveyance that is used to pass the peak discharge of the
maximum design storm that is controlled by the stormwater facility.
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Pennsylvania Code Title 25 and the
Clean Streams Law.
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.
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").
A system of pipes and/or open channels that conveys intercepted
runoff and stormwater from other sources but excludes domestic sewage
and industrial wastes.
Drainage runoff from the surface of the land resulting from
precipitation, snow, or ice melt.
Those subareas of a watershed in which some type of detention
is required to meet the plan requirements and the goals of Act 167.
Any structure, natural or man-made, that, due to its condition,
design, or construction, conveys, stores, or otherwise affects stormwater
runoff quality, rate, or quantity. Typical stormwater management facilities
include, but are not limited to, detention and retention basins, open
channels, storm sewers, pipes, and infiltration structures.
The watershed plan for managing stormwater runoff for a watershed,
adopted by Delaware and Chester Counties as required by the Act of
October 4, 1978, P.L. 864 (Act 167), as amended, and known as the
"Stormwater Management Act." See also "Watershed Stormwater Management
Plan."
The plan prepared by the applicant or his representative
indicating how stormwater runoff will be managed at the particular
site of interest according to this chapter, and including all necessary
design drawings, calculations, supporting text, and documentation
to demonstrate that chapter requirements have been met, hereafter
referred to as "SWM site plan."
A natural watercourse.
The land area adjacent to each side of a stream essential
to maintaining water quality (see also "riparian buffer").
A bridge, culvert, or other structure in excess of 100 feet
in length upstream to downstream which encloses a regulated water
of the commonwealth.
The smallest drainage unit of a watershed for which stormwater
management criteria have been established in the stormwater management
plan.
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.
Any and all rivers, streams, creeks, rivulets, ditches, watercourses,
storm sewers, lakes, dammed water, wetlands, ponds, springs, and all
other bodies or channels of conveyance of surface waters, or parts
thereof, whether natural or artificial, within or on the boundaries
of the commonwealth.
A low-lying stretch of land that gathers or carries surface
water runoff.
See "stormwater management site plan."
See "forest management."
The time required 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.
Highest point of elevation in a stream channel cross-section
at which a rising water level just begins to flow out of the channel
and over the floodplain.
United States Department of Agriculture.
Natural condition (see also "predevelopment condition").
Seasonal depressional wetlands that are covered by shallow
water for variable periods from winter to spring but may be completely
dry for most of the summer and fall.
A channel or conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
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 the commonwealth.
Region or area drained by a river, watercourse, or other
body of water, whether natural or artificial.
A watershed plan for managing stormwater runoff for a watershed,
adopted by Delaware and Chester Counties as required by the Act of
October 4, 1978, P.L. 864 (Act 167), as amended, and known as the
"Stormwater Management Act" (e.g., Chester Creek, Ridley Creek, Crum
Creek, Darby-Cobbs Creeks). See also "stormwater management plan."
The surface and subsurface area surrounding a water supply
well, well field, or spring supplying a public water system through
which contaminants are reasonably likely to move toward and reach
the water source.
Pond for urban runoff management that is designed to detain
urban runoff and always contains water.
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. Wetlands
generally include swamps, marshes, bogs, fens, and similar areas.
A natural ground cover with more than one viable tree of
a DBH of six inches or greater per 1,500 square feet which existed
within three 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.
