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;
masculine, feminine, or nongender pronouns shall be used interchangeably.
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."
F.
These definitions do not necessarily reflect the definitions contained
in pertinent regulations or statutes, and are intended for this chapter
only.
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 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 Borough for approval to engage in any regulated
activity at a project site in the Borough.
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 Borough 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
commonwealth 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.
The Pennsylvania Stormwater Best Management Practices Manual,
drafted by the Pennsylvania Department of Environmental Protection.
No. 363-0300-002 (December 2006), as amended and updated.
The Borough of Narberth, Montgomery County, Pennsylvania.
The professional engineer licensed in the commonwealth of
Pennsylvania, duly appointed as the engineer for the Borough of Narberth.
The appointed Manager of the Borough of Narberth, or a representative
assigned by the Manager to address matters under this chapter.
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 bank full flows.
An underground reservoir or tank for storing rainwater.
As defined under state regulations, protection of designated
and existing uses (see 25 Pennsylvania Code Chapters 93 and 96), including:
Each stream segment in Pennsylvania has a designated use, such
as cold-water fishery or potable water supply, which is listed in
Chapter 93.[1] These uses must be protected and maintained under commonwealth
regulations.
"Existing uses" are those attained as of November 1975, regardless
of whether they have been designated in Chapter 93.[2] Regulated earth disturbance activities must be designed
to protect and maintain existing uses and maintain the level of water
quality necessary to protect those uses in all streams and to protect
and maintain water quality in special protection streams.
Water quality involves the chemical, biological, and physical
characteristics of surface water bodies. After regulated earth disturbance
activities are complete, these characteristics can be impacted by
the addition of pollutants such as sediment and changes in habitat
through increased flow volumes and/or rates as a result of changes
in land surface area from those activities. Therefore, permanent discharges
to surface waters must be managed to protect the stream bank, streambed,
and structural integrity of the waterway to prevent these impacts.
The 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 human-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.
Any person licensed by the Pennsylvania Department of State
or otherwise 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. Also see "return
period."
The agent of the Montgomery County Planning Commission or
Montgomery 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.
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.
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 Borough.
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.
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.
The point of discharge for a stormwater facility.
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 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;
and the moving, depositing, stockpiling, or storing of soil, rock,
or earth materials. Conventional, low-impact gardening activities,
tree planting unrelated to a land development, mulching, or property
maintenance shall not be considered an earth disturbance activity.
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 antidegradation).
The dominant land cover during the five-year period immediately
preceding a proposed regulated activity.
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. Also includes areas that comprise
Group 13 soils, as listed in Appendix A of the Pennsylvania DEP Technical
Manual for Sewage Enforcement Officers (as amended or replaced from
time to time by DEP).
The channel of the watercourse and those portions of the
adjoining floodplains that are reasonably required to carry and discharge
the 100-year flood. Unless otherwise specified, the boundary of the
floodway is as indicated on maps and flood insurance studies provided
by FEMA. In an area where no FEMA maps or studies have defined the
boundary of the 100-year floodway, it is assumed, absent evidence
to the contrary, that the floodway extends from the stream to 50 feet
from the top of the bank of the stream.
The study of landforms associated with river channels and
the processes that form them.
Planning and activities necessary for the management of forestland.
These include conducting a timber inventory, 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.
A natural or man-made waterway, usually broad and shallow,
covered with erosion-resistant grasses used to convey surface water.
Systems and practices that use or mimic natural processes
to infiltrate, evapotranspire, or reuse stormwater on the site where
it is generated including methods of stormwater treatment and control
that use the natural capacities of soil and vegetation to prevent
or reduce stormwater runoff and associated nonpoint source pollution.
Green infrastructure methods may be combined with conventional or
structural stormwater treatment systems, such as separators, ponds,
or underground systems, to create stormwater "treatment trains" that
enhance stormwater treatment and water quality.
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 United States Army Corps of Engineers, Hydrologic Engineering
Center (HEC) - Hydrologic Modeling System (HMS). This model was used
to model the Darby Creek and Cobbs 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, 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 classification.
The soils in the area of the development site may be identified from
a soil survey report that can be obtained from local NRCS offices
or conservation district offices. Soils become less pervious as the
HSG varies from A to D. (NRCS)
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 an impervious
surface. Swimming pools and other water features shall be regarded
as impervious surfaces, regardless of whether they are above or below
ground. Porous asphalt or concrete, grid/lattice systems, paving blocks
and similar materials deemed to be less than 100% impervious may be
given partial consideration as pervious surfaces if installed and
maintained in accordance with Borough specifications and approved
by the Borough Engineer.
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.
A type of topography or landscape characterized by surface
depressions, sinkholes, rock pinnacles/uneven bedrock surface, underground
drainage, and caves. Karst is formed on carbonate rocks, such as limestone
or dolomite.
Inclusive of any or all of the following meanings:
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.
Site design approaches and small-scale stormwater management
practices that promote the use of natural systems for infiltration,
evapotranspiration, and reuse of rainwater. LID can be applied to
new development, urban retrofits, and revitalization projects. LID
utilizes design techniques that infiltrate, filter, evaporate, and
store runoff close to its source. Rather than rely on costly large-scale
conveyance and treatment systems, LID addresses stormwater through
a variety of small, cost-effective landscape features located on site.
See Appendix E[4] for LID practices.
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.
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.
National Pollutant Discharge Elimination System, the federal
government's system for issuance of permits under the Clean Water
Act, which is delegated to DEP in Pennsylvania.
USDA 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 Borough'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 the original, pre-amended
adoption of this chapter, March 9, 2005.
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.
Any area not defined as impervious.
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
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 § 92a.2.
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 established under this chapter.
The specific area of land where any regulated activities
in the Borough 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
chapter.
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 disturbance activities or any activities or proposed
activities that involve the alteration or development of land in a
manner that may affect stormwater runoff, including but not limited
to the activities specified under this chapter.
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 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.
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 retention basin must infiltrate
stored water in four days or less.
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 magnitude can be expected to occur one time. For example,
the twenty-five-year return period rainfall would be expected to occur
on average once every 25 years; or stated in another way, the probability
of a twenty-five-year storm occurring in any one year is 0.04 (i.e.,
a 4% chance).
A permanent area of trees, shrubs, or other vegetation located
adjacent to streams, lakes, ponds and wetlands.
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.
Any part of precipitation that flows over the land.
The Subdivision and Land Development Ordinance[7] for the Borough of Narberth, as amended.
Soils 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 DEP 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.
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 or snow or ice melt.
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.
The watershed plan, known as the "Darby and Cobbs Creeks
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 Darby and Cobbs Creeks watershed
adopted by Delaware County, Chester County, Montgomery County, and
Philadelphia County as required by the Act of October 4, 1978, P.L.
864 (Act 167).[8]
The plan prepared by the developer or his representative
indicating how stormwater runoff will be managed at the development
site in accordance with this chapter. "Stormwater management site
plan" may be designated as "SWM site plan" throughout this chapter.
A natural watercourse.
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.
As defined in the Pennsylvania Municipalities Planning Code,
Act of July 31, 1968, P.L. 805, No. 247.[9]
A low-lying stretch of land that gathers or carries surface
water runoff.
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.
Natural condition (see also "predevelopment 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.
Any and all rivers, streams, creeks, rivulets, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs, and all other bodies or channels of conveyance of
surface and underground water, or parts thereof, whether natural or
artificial, within or on the boundaries of this commonwealth.
Region or area drained by a river, watercourse, or other
surface water of the commonwealth.
A structure built over a well or the source of water for
a well.
Pond for urban runoff management that is designed to detain
urban runoff and always contains water.
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 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.
[3]
Editor's Note: See 53 P.S. § 10503(1.1).
[4]
Editor's Note: Appendix E is included as an attachment to this chapter.
[5]
Editor's Note: Chapter 92 of Title 25 of the Pennsylvania
Code was reserved 10-8-2010, effective 10-9-2010. It was replaced
by Chapter 92a, National Pollutant Discharge Elimination System (NPDES)
Permitting, Monitoring and Compliance.
[6]
Editor's Note: See 35 P.S. § 691.1 et seq.
[8]
Editor's Note: See 32 P.S. § 680.1 et seq.
[9]
Editor's Note: See 53 P.S. § 10101 et seq.
