For the purposes of this Part 2, 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 words "shall" and "must" are mandatory; the words "may" and "should"
are permissive.
As used in this Part 2, 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 at a rate greater
than that which would occur because of natural process alone.
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.
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, developer or other person who has filed an application
to the Municipality for approval to engage in any regulated activity
at a project site in the Municipality.
Engineering or site drawings maintained by a developer to
show the actual locations of building components and changes from
the original contract documents. These documents, or a copy of same,
are turned over to the Municipality 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 groundwater recharge and to otherwise meet the purposes of this Part 2. Stormwater BMPs are commonly grouped into one of two broad categories or measures: "structural" or "nonstructural." In this Part 2, nonstructural BMPs or measures refer to operational and/or behavior-related practices that attempt to minimize the contact of pollutants with stormwater runoff, or to provide other environmental or aesthetic benefits such as low-impact designs, riparian or forested buffers; 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, bioretention, wet ponds, permeable paving, grassed swales, sand filters, detention basins, and manufactured devices. Structural stormwater BMPs are permanent appurtenances to the project site.
Pennsylvania Stormwater Best Management Practices Manual,
No. 363-0300-002, as amended from time to time.
The area of land immediately adjacent to any stream, measured
perpendicular to and horizontally from the top-of-bank on both sides
of a stream (see "top-of-bank").
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.
A conservation district, as defined in Section 3(c) of the
Conservation District Law [3 P.S. § 851(c)], that has the
authority under a delegation agreement executed with DEP to administer
and enforce all or a portion of the regulations promulgated under
25 Pa. Code Chapter 102.
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 that impounds or may impound
water or another fluid or semifluid.
The Pennsylvania Department of Environmental Protection.
The magnitude and temporal distribution of precipitation
from a storm event measured in probability of occurrence that such
magnitude will be equaled or exceeded in any one year (e.g., the twenty-percent
chance, or so-called five-year (recurrence interval) 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 soon after
a rainfall event, and to become dry until the next rainfall event.
The volume of runoff that is captured and released into the
waters of the commonwealth at a controlled rate.
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, and site alteration such as embankments,
dredging, grubbing, grading, paving, parking or storage facilities,
excavation, filling, stockpiling, or clearing.
See "project site."
The outside bark diameter at breast height which is defined
as 4.5 feet (1.37m) 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.
An impervious or impermeable surface that is directly connected
to a stormwater drainage or conveyance system, leading to direct runoff,
decreased infiltration, decreased filtration, and decreased time of
concentration.
An impervious or impermeable surface that is disconnected
from any stormwater drainage or conveyance system, and is redirected
or directed to a pervious area, which allows for infiltration, filtration,
and increased time of concentration.
See "earth disturbance."
An 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.
See "stormwater management site plan."
A construction or other human activity which disturbs the
surface of land including, but not limited to, clearing and grubbing,
grading, filling, excavations, embankments, land development, agricultural
plowing or tilling, timber harvesting activities, road maintenance
activities, mineral or fluid extraction, and 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 natural process by which the surface of the land is worn
away by water, wind or chemical action.
A plan that is designed to minimize accelerated erosion and
sedimentation.
Surface waters having quality that satisfy one or more of the conditions established in Pennsylvania Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(b).
The dominant land cover during the five-year period immediately
preceding a proposed regulated activity. If the initial condition
of the site is undeveloped land, the land use shall be considered
as "meadow" unless the Municipality determines that the natural land
cover has a lower Curve Number (CN) or Rational "c" value, such as
forested lands.
Federal Emergency Management Agency.
A temporary condition of partial or complete inundation of
land areas from the overflow of streams, rivers, and other waters
of the commonwealth.
Any land area susceptible to inundation by water from any
natural source or delineated by applicable FEMA maps and studies as
being a special flood hazard area. Included are lands adjoining a
river or stream that have been or may be expected to be inundated
by a one-hundred-year flood, i.e., the flood of magnitude that has
a one-percent chance of being equaled or exceeded in any given year.
The channel of a 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 Flood Insurance Rate Maps
(FIRMs) 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 50 feet from the top-of-bank on each side
of the stream.
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, site preparation,
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.
Either of the following:
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 within the saturated zone of soil and rock.
The replenishment of existing natural underground water supplies
from precipitation 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 Wissahickon Creek Watershed during the Act 167 plan development and is the basis for the standards and criteria of this Part 2.
Surface waters having quality that satisfy one or more of the conditions established by 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 at
a selected point in the drainage system.
The hydrologic cycle or balance that sustains quality and
quantity of stormwater, baseflow, storage, and groundwater supplies
under natural conditions.
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 classifications.
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).
A surface that prevents the infiltration of water into the
ground. Impervious surfaces (or areas) shall include, but not be limited
to, roofs, additional indoor living spaces, patios, garages, storage
sheds and similar structures, swimming pools, and any new streets
or sidewalks. Decks, parking areas, and driveway areas are not counted
as impervious areas if they do not prevent infiltration.
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
Development that occurs on smaller parcels that has remained
undeveloped, but is 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 shallow impoundment that is designed to infiltrate stormwater
into the soil. Infiltration basins are believed to have a high pollutant
removal efficiency, and can also help recharge the groundwater, thus
restoring baseflows to stream systems. Infiltration basins can be
problematic at many sites because of stringent soil requirements.
A structure designed to direct runoff into the underground
water (e.g., French drains, seepage pits, seepage trenches, or infiltration
galleries).
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.
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.
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 PA Municipalities
Planning Code.[1]
A soil horizon or condition in the soil profile or underlying
a stratum 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 sufficient 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 the Wissahickon Creek Watershed hydrologic model.
A method for calculation of velocity of flow (e.g., feet
per second) and flow or discharge 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 (PE) licensed as such in the Commonwealth
of Pennsylvania, duly appointed as the Engineer for a Municipality,
planning agency, or joint planning commission.
Whitpain Township, Montgomery County, Pennsylvania.
Pre-development 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 waterbody 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 are 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,[2] which is delegated to DEP in Pennsylvania.
Natural Resource Conservation Service of the U.S. Department
of Agriculture [previously the Soil Conservation Service (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 Part 2.
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.
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
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 control requirements (WQv) of § 125-69. For example, any inlets draining to an infiltrating system should be sumped and trapped to prevent the system from becoming clogged with excess sediment.
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 this Part 2.
A BMP that is a planted depression or shallow hole that collects
stormwater runoff from impervious areas, such as roofs, driveways,
hardscaping and paved parking lots. Rain gardens are designed, constructed
and maintained for the purpose of providing infiltration or recharge
of stormwater into the soil and/or underground aquifer. A rain garden
shall have a maximum ponding depth of one foot and shall be in conformance
with the Pennsylvania DEP BMP guidelines, as amended from time to
time.
[Amended 9-20-2016 by Ord. No. 350]
A rainfall-runoff relation used to estimate peak flow; Q
= CiA.
Any stream segment or other runoff conveyance used in the
Wissahickon Creek Watershed hydrologic model.
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
The volume of stormwater, in cubic feet, required to be infiltrated
on site, where practicable and appropriate.
Demolition and subsequent rebuilding of impervious surface.
Construction drawings revised to represent the as-built conditions.
See "return period."
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 disturbance activities or any activities that involve
the alteration or development of land in a manner that may affect
stormwater runoff.
Activity involving earth disturbance subject to regulation
under 25 Pa. Code Chapter 92, 25 Pa. Code Chapter 102, or the Clean
Streams Law.[3]
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.
Replacement of an impervious surface that does not involve
reconstruction of an existing paved (impervious) surface (e.g., addition
of a new layer of asphalt over an existing paved surface).
Reconstruction of and full replacement of an existing paved
(impervious) surface (e.g., demolition and removal of surface layer,
foundation, and base course; and subsequent reconstruction of the
entire sequence).
The volume of runoff that is captured and not released directly
into the surface waters of the commonwealth during or after a storm
event.
The average interval, in years, within which a storm event
of a given or greater 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, or conversely would have a
four-percent chance of occurrence or exceedance in any given year.
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.
A type of riparian buffer that consists of permanent vegetation
that is predominantly native trees, shrubs, and forbs along surface
waters that is maintained in a natural state or sustainably managed
to protect and enhance water quality, stabilize stream channels and
banks, and separate land use activities from surface waters.
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.[4]
Soils or other materials transported by surface water as
a product of erosion.
The process by which mineral or organic matter is accumulated
or deposited by the movement of water or air.
A barrier, dam, or retention or detention basin located and
designed in such a way as to retain rock, gravel, sand, silt, clay
or other material transported by water during construction.
The placement, discharge, or any other introduction of sediment
into the waters of the commonwealth.
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 zones through which contaminants, if present, are likely
to migrate and reach drinking water wells or surface water intakes.
A conveyance that is used to pass the peak discharge of the
maximum design storm that is controlled by the stormwater facility.
The permit required to be issued by the Municipality before
any grading activities are allowed to commence on a site within the
Municipality. Such permits typically require information including,
but not limited to, a contour map of the site showing existing and
proposed contours, a plot plan showing streams and drainage courses
on or within 50 feet of the site, drainage structures, neighboring
streets and alleys, trees, and floodplain zones on or within 50 feet
of the site, soil classifications.
The regulatory requirements to protect, maintain, reclaim,
and restore water quality under Title 25 of the Pennsylvania Code
and the Clean Streams Law.[5]
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.
The number of times that a given storm event occurs or is
exceeded on average in a stated period of years (see "return period").
A system of pipes and/or open channels that convey intercepted
runoff and stormwater from other sources but exclude domestic sewage
and industrial wastes.
Drainage runoff from the surface of the land resulting from
precipitation or 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 infiltration basins,
open channels, storm sewers, pipes, and infiltration structures.
The watershed plan, known as the "Wissahickon Creek Watershed
Act 167 Stormwater Management Plan," for managing those land use activities
that will influence stormwater runoff quality and quantity, and that
would impact the Wissahickon Creek Watershed adopted by Montgomery
and Philadelphia Counties as required by the Act of October 4, 1978,
P.L. 864 (Act 167).
The plan prepared by the applicant or the applicant's representative indicating how stormwater runoff will be managed at project site to meet the requirements of this Part 2. Small project SWM site plans may be prepared for certain projects.
A natural watercourse.
The land area adjacent to each side of a stream essential
to maintaining water quality (see "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. As defined in the Pennsylvania Municipalities
Planning Code, Act of July 31, 1968, P.L. 805, No. 247.[6]
Perennial and intermittent streams, rivers, lakes, reservoirs,
ponds, wetlands, springs, natural seeps, and estuaries, excluding
water at facilities approved for wastewater treatment, such as wastewater
treatment impoundments, cooling water ponds, and constructed wetlands
used as part of a wastewater treatment process.
A low-lying stretch of land that gathers or carries surface
water runoff.
See "forest management."
The time required for surface runoff to travel from the most
remote point of a watershed to the watershed outlet.
Highest point of elevation in a stream channel cross-section
at which a rising water level just begins to flow outside of the channel
and over the floodplain.
Natural condition (see also "pre-development condition").
United States Department of Agriculture.
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.
Rivers, streams, creeks, rivulets, impoundments, ditches,
watercourses, storm sewers, lakes, dammed water, 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.
Region or area drained by a river, watercourse or other surface
water of the commonwealth.
(See § 125-69.) The storage capacity, in acre-feet, required to capture and treat a portion of stormwater runoff from the developed or redeveloped areas of the site.
Either one of the following:
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, including
swamps, marshes, bogs, and similar areas.
A natural groundcover with more than one viable tree of a
DBH of six inches or greater per 1,500 square feet which existed for
a minimum of three consecutive years.
