As used in this chapter, the following terms shall have the
meanings indicated:
ACCELERATED EROSION
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 process alone.
AGRICULTURAL ACTIVITY
Activities associated with agriculture, such as agricultural
cultivation, agricultural operation, and animal heavy-use areas. This
includes the work of producing crops, including tillage, land clearing,
plowing, disking, harrowing, planting, and 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.
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;
also the changing of surface conditions by causing the surface to
be more or less impervious as the result of changing the land cover,
including the water, vegetation and bare soil.
APPLICANT
A person who has filed an application for approval to engage in any regulated activity defined in §
157-5 of this chapter.
AS-BUILT DRAWINGS
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 Township Engineer at the completion of the project.
BANKFULL
The channel at the top-of-bank or point from where water
begins to overflow onto a floodplain.
BASE FLOW
The 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.
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:
"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.
BIORETENTION
A stormwater retention area that utilizes woody and herbaceous
plants and soils to remove pollutants before infiltration occurs.
CHANNEL
An open drainage feature through which stormwater flows.
Channels include but shall not be limited to natural and man-made
watercourses, swales, streams, ditches, canals, and pipes that convey
continuously or periodically flowing water.
CISTERN
An underground reservoir or tank for storing rainwater.
CULVERT
A structure, with its appurtenant works, which carries water
under or through an embankment or fill.
CURVE NUMBER
A value used in the Soil Cover Complex Method. It is a measure
of the percentage of precipitation which is expected to run off from
the watershed and is a function of the soil, vegetative cover, and
tillage method.
DAM
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.
DEPARTMENT
The Pennsylvania Department of Environmental Protection (PADEP).
DESIGNEE
The agent of Bucks County, the Bucks County Conservation
District, and/or the agent of Warwick Township involved with the administration,
review, or enforcement of any provisions of this chapter by contract
or memorandum of understanding.
DESIGN PROFESSIONAL (QUALIFIED)
A Pennsylvania registered professional engineer, registered
landscape architect or registered professional land surveyor trained
to develop stormwater management plans.
DESIGN STORM
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.
DETENTION BASIN
An area of land and/or structure designed to collect and
retard stormwater runoff, temporarily storing the runoff and releasing
it at a predetermined rate.
DEVELOPER
Any landowner, agent of such landowner or tenant with the
permission of such landowner who makes or causes to be made a subdivision
of land or land development or, as used in this chapter, a regulated
activity.
DEVELOPMENT
Any man-made change to improved or unimproved real estate,
including but not limited to buildings or other structures, the placement
of mobile homes, streets and other paving, utilities, mining, dredging,
filling, grading, excavation or drilling operations and the subdivision
of land. As used in this chapter, “development” encompasses
both new development and redevelopment.
DEVELOPMENT SITE
The specific tract or parcel of land where any regulated
activity is planned, conducted or maintained.
DISCHARGE
A.
(verb) To release water from a project, site, aquifer, drainage
basin or other point of interest.
B.
(noun) The rate and volume of flow of water, such as in a stream,
generally expressed in cubic feet per second. See also "peak discharge."
DISCONNECTED IMPERVIOUS AREA (DIA)
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 as specified in Appendix F, Disconnected
Impervious Area (DIA).
DISTURBED AREAS
Unstabilized land area where an earth-disturbance activity
is occurring or has occurred.
DITCH
A man-made waterway constructed for irrigation or stormwater
conveyance purposes.
DRAINAGE EASEMENT
A right granted by a landowner to a grantee, allowing the
use of private land for stormwater management purposes.
DRAINAGE PERMIT
A permit issued by Warwick Township after the SWM site plan
has been approved.
EARTH-DISTURBANCE ACTIVITY
A construction or other human activity that disturbs the
surface of land, including but not limited to clearing and grubbing,
grading, excavations, embankments, land development, agricultural
plowing or tilling, timber harvesting activities, road maintenance
activities, mineral extraction, and the moving, depositing, stockpiling,
or storing of soil, rock or earth materials. Activity involving earth
disturbance is subject to regulation under 25 Pa. Code § 92,
25 Pa. Code § 102, or the Clean Streams Law.
EMERGENCY SPILLWAY
A conveyance area that is used to pass peak discharge greater
than the maximum design storm controlled by the stormwater facility.
ENCROACHMENT
A structure or activity that changes, expands or diminishes
the course, current or cross section of a watercourse, floodway or
body of water.
EROSION
The removal of surface materials by the action of natural
elements.
EROSION AND SEDIMENT CONTROL PLAN
A site-specific plan identifying BMPs to minimize accelerated
erosion and sedimentation. For agricultural plowing or tilling activities,
the erosion and sediment control plan is that portion of a conservation
plan identifying BMPs to minimize accelerated erosion and sedimentation.
EXCEPTIONAL VALUE WATERS
Surface waters of high quality which satisfy Pennsylvania
Code Title 25, Environmental Protection, Chapter 93, Water Quality
Standards, § 93.4b(b) (relating to antidegradation).
EXISTING RECHARGE AREA
Undisturbed surface area or depression where stormwater collects
and a portion of which infiltrates and replenishes the groundwater.
FLOOD
A temporary condition of partial or complete inundation of
land areas from the overflow of streams, rivers, and other waters
of the commonwealth.
FLOODPLAIN
A.
FLOODWAYThat portion of the floodplain, including the watercourse channel and adjacent land areas, which must be reserved to carry the one-hundred-year-storm without cumulatively increasing the flood elevation more than one foot.
B.
FLOOD FRINGEThat portion of the floodplain which is outside the floodway.
FOREST MANAGEMENT/TIMBER OPERATIONS
Planning and associated 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, and reforestation.
FREEBOARD
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.
GRADE
A.
(noun) A slope, usually of a road, channel or natural ground,
specified in percent and shown on plans as specified herein.
B.
(verb) To finish the surface of a roadbed, the top of an embankment,
or the bottom of excavation.
GROUNDWATER
Water beneath the earth's surface that supplies wells and
springs and is often between saturated soil and rock.
GROUNDWATER RECHARGE
The replenishment of existing natural underground water supplies
from rain or overland flow.
HEC-HMS
The United States Army Corps of Engineers' Hydrologic Engineering
Center (HEC) - Hydrologic Modeling System (HMS). This model was used
to model the Neshaminy Creek watershed during the Act 167 plan development
and was the basis for the standards and criteria of this chapter.
HIGH QUALITY WATERS
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).
HOT SPOT
An area where land use or activity generates highly contaminated runoff, with concentrations of pollutants in excess of those typically found in stormwater. Typical pollutant loadings in stormwater may be found in Chapter 8, Section 6, of the Pennsylvania Stormwater Best Management Practices Manual, Pennsylvania Department of Environmental Protection (PADEP) No. 363-0300-002 (2006). Additional information concerning hot spots may be found in §
157-15A of this chapter.
HYDROGRAPH
A graph representing the discharge of water versus time for
a selected point in the drainage system.
HYDROLOGIC REGIME
The hydrologic cycle or balance that sustains quality and
quantity of stormwater, base flow, storage, and groundwater supplies
under natural conditions.
HYDROLOGIC SOIL GROUP
A classification of soils by the Natural Resources Conservation
Service, formerly the Soil Conservation Service, 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.
IMPERVIOUS SURFACE
Those surfaces which do not absorb water. All buildings,
parking areas, driveways, roads, sidewalks, swimming pools, and any
areas in concrete, asphalt, and packed stone shall be considered impervious
surfaces within the definition. In addition, other areas determined
by the Township Engineer to be impervious within the meaning of this
definition will also be classed as impervious surfaces.
IMPOUNDMENT
A retention or detention basin designed to retain stormwater
runoff and release it at a controlled rate.
INFILTRATION
Movement of surface water into the soil, where it is absorbed
by plant roots, evaporated into the atmosphere, or percolated downward
to recharge groundwater.
INFILTRATION STRUCTURE
A structure designed to direct runoff into the underground
water (e.g., French drains, seepage pits, or seepage trenches).
INITIAL ABSTRACTION (IA)
The value used to calculate the volume or peak rate of runoff
in the Soil Cover Complex Method. It represents the depth of rain
retained on vegetation plus the depth of rain stored on the soil surface
plus the depth of rain infiltrated prior to the start of runoff.
INLET
The upstream end of any structure through which water may
flow.
INTERMITTENT STREAM
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.
KARST
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.
LAND DEVELOPMENT
Any of the following activities:
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 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, including any additions to existing nonresidential buildings
or conversions of residential to nonresidential buildings with additions;
(2)
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; or
(3)
Any increase in impervious surface(s) on nonresidential properties.
LIMITING ZONE
A soil horizon or condition in the soil profile or underlying
strata that includes one of the following:
A.
A seasonal high-water table, whether perched or regional, determined
by the direct observation of the water table or indicated by soil
mottling.
B.
A rock with open joints, fractures or solution channels, or
masses of loose rock fragments, including gravel, with insufficient
fine soil to fill the voids between the fragments.
C.
A rock formation other stratum or soil condition that is slowly
permeable so that it effectively limits downward passage of effluent.
LOT
A parcel of land, used or set aside and available for use
as the site of one or more buildings and any building accessory thereto
or for any other purpose, in one ownership and not divided by a street,
nor including any land within the right-of-way of a public street
upon which said lot abuts, even if the ownership to such right-of-way
is in the owner of the lot. A lot, for the purpose of this chapter,
may or may not coincide with a lot of record. A lot shall front on
a public street.
LOW-IMPACT DEVELOPMENT (LID) PRACTICES
Practices that will minimize proposed conditions' runoff
rates and volumes, which will minimize needs for artificial conveyance
and storage facilities.
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.
MUNICIPAL ENGINEER
A professional engineer licensed as such in the Commonwealth
of Pennsylvania, duly appointed as the Engineer for Warwick Township.
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.
NONSTORMWATER DISCHARGES
Water flowing in stormwater collection facilities, such as
pipes or swales, which is not the result of a rainfall event or snowmelt.
NONSTRUCTURAL BEST MANAGEMENT PRACTICES
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.
NPDES
The National Pollutant Discharge Elimination System, the
federal government's system for issuance of permits under the Clean
Water Act, which is delegated to the PADEP in Pennsylvania.
NRCS
The Natural Resources Conservation Service (previously Soil
Conservation Service).
OUTFALL
"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 to a stream, river, lake, tidewater
or artificial drain.
PEAK DISCHARGE
The maximum rate of stormwater runoff from a specific storm
event.
PERENNIAL STREAM
A stream which contains water at all times except during
extreme drought.
PERVIOUS SURFACE
A surface that allows the infiltration of water into the
ground.
PIPE
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
POINT SOURCE
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 Pa. Code § 92.1.
POST-CONSTRUCTION
The 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.
PRETREATMENT
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 volume
requirements of this chapter.
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 to perform the work required by this
chapter.
RECHARGE
The replenishment of groundwater through the infiltration
of rainfall, other surface waters, or land application of water or
treated wastewater.
RECORD DRAWINGS
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-built drawings 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. Record drawings are not the same as record plans
submitted for recording with the county in accordance with the Pennsylvania
Municipalities Planning Code (Act 247).
REDEVELOPMENT
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. Utility trenches
in streets are not considered redevelopment.
[Amended 10-17-2022 by Ord. No. 2022-05]
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 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.
REPAVING
Replacement of the impervious surface that does not involve
reconstruction of an existing paved (impervious) surface.
REPLACEMENT PAVING
Reconstruction of and full replacement of an existing paved
(impervious) surface.
RETENTION BASIN
A stormwater storage area which has a controlled release
rate and maintains a constant water level while not in use for flood
storage.
RETENTION VOLUME/REMOVED RUNOFF
The volume of runoff that is captured and not released directly
into the surface waters of the commonwealth during or after a storm
event.
RETURN PERIOD
The probability an event will occur in any given year; typically
displayed as a whole number, e.g., twenty-five-year event, and represents
the inverse of the frequency of that event. For example, the twenty-five-year
return-period rainfall gives the probability, 1/25 or 4%, which that
size storm will occur in any given year.
ROAD MAINTENANCE
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.
ROOF DRAIN
A drainage conduit or pipe that collects water runoff from
a roof and leads it away from the structure.
RUNOFF
The surface water discharge or rate of discharge after a
fall of rain or snow that does not enter the soil but runs off the
surface of the land.
SALDO
The Subdivision and Land Development Ordinance.
SEDIMENT
Soils or other materials transported by surface water as
a product of erosion.
SEDIMENTATION
The process by which mineral or organic matter is accumulated
or deposited by wind, water or gravity. Once this matter is deposited
or remains suspended in water, it is usually referred to as "sediment."
SEDIMENT POLLUTION
The placement, discharge of any other introduction of sediment
into the waters of the commonwealth.
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 underground water. More information on seepage pits may be
found in the Pennsylvania BMP Manual, December 2006, Chapter 6, Section
4.
SEPARATE STORM SEWER SYSTEM
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.
SHALLOW CONCENTRATED FLOW
Stormwater runoff flowing in shallow, defined ruts prior
to entering a defined channel or waterway.
SHEET FLOW
A flow process associated with broad, shallow water movement
on sloping ground surfaces that is not channelized or concentrated.
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).”
SPECIAL PROTECTION SUBWATERSHEDS
Watersheds that have been designated in Pennsylvania Code
Title 25, Environmental Protection, Chapter 93, Water Quality Standards,
as exceptional value (EV) or high quality (HQ) waters.
SPILLWAY
A conveyance that is used to pass the peak discharge of the
maximum design storm that is controlled by the stormwater facility.
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.
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 "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
The surface runoff generated by precipitation reaching the
ground surface.
STORMWATER MANAGEMENT FACILITY
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.
STORMWATER MANAGEMENT PLAN
The watershed plan, known as the "Neshaminy 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 Neshaminy Creek Watershed, adopted by Bucks and Montgomery
Counties as required by the Act of October 4, 1978, P.L. 864 (Act
167).
STORMWATER SWM SITE 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.
STREAM
A flow of water in a natural channel or bed, as a brook,
rivulet, or a small river.
STREAM BUFFER
The land area adjacent to each side of a stream, essential
to maintaining water quality.
[Amended 10-17-2011 by Ord. No. 2011-10]
STREAM ENCLOSURE
A bridge, culvert, or other structure in excess of 100 feet
in length, upstream to downstream, which encloses a regulated water
of the commonwealth.
SUBAREA (SUBWATERSHED)
The smallest drainage unit of a watershed for which stormwater
management criteria have been established in the stormwater management
plan.
SUBDIVISION
The division or redivision of a lot, tract, or parcel of
land by any means into two or more lots, tracts, parcels, or other
divisions of land, including changes in existing lot lines for the
purpose, whether immediate or future, of lease, partition by the court
for distribution to heirs or 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.
SURFACE WATERS OF THE COMMONWEALTH
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.
SWALE
A low-lying stretch of land that gathers or carries surface
water runoff.
SWM SITE PLAN
The documentation of the stormwater management system to be used for a given development site, the contents of which are established in §
157-19.
TIME OF CONCENTRATION (Tc)
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. The Tc shall be representative
of the developed area, i.e., a long Tc shall not be used if the majority
of the proposed development is within close proximity to the detention
facility, as determined by the Township Engineer, for those sites
having unique circumstances.
TOP-OF-BANK
The 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.
VEGETATED SWALE
A natural or man-made waterway, usually broad and shallow,
covered with erosion-resistant grasses, used to convey surface water.
VERNAL POOL
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.
WATERCOURSE
A channel or conveyance of surface water having a defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
WATERSHED
A region or area drained by a river, watercourse, or other
body of water, whether natural or artificial.
WATERS OF THE COMMONWEALTH
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 and underground
water, or parts thereof, whether natural or artificial, within or
on the boundaries of the commonwealth.
WELLHEAD PROTECTION AREA
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.
WET BASIN
A pond for urban runoff management that is designed to detain
urban runoff and always contains water.
WETLANDS
These areas of hydric soils supporting wetland vegetation
where the water table is at or near the surface or where shallow water
covers the site due to permanent or seasonal inundation of surface
water or groundwater, including swamps, marshes, bogs or other areas
meeting the wetland criteria established by the Department of Environmental
Protection or the United States Army Corps of Engineers.