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 human activities and natural processes at a rate greater
than would occur because of natural processes alone.
BEST MANAGEMENT PRACTICE (BMP)
Activities, facilities, measures or procedures used to manage stormwater quantity and quality impacts from the regulated activities listed in §
225-5 to meet state water quality requirements, to promote groundwater recharge and to otherwise meet the purposes of this chapter.
BIORETENTION
Densely vegetated, depressed features that store stormwater
and filter it through vegetation, mulch, planting soil, etc. Ultimately
stormwater is evapotranspirated, infiltrated, or discharged. Optimal
bioretention areas mimic natural forest ecosystems in terms of species
diversity, density, distribution, use of native plants, etc.
BOROUGH
Borough of Catasauqua, Lehigh County, Pennsylvania. Also
"Borough" or "Catasauqua."
BUFFER
(1)
STREAMSIDE BUFFERA zone of variable width located along a stream that is vegetated and is designed to filter pollutants from runoff.
(2)
SPECIAL GEOLOGIC FEATURE BUFFERA required isolation distance from a special geologic feature to a proposed BMP needed to reduce the risk of sinkhole formation due to stormwater management activities.
CAPTURE/REUSE
Stormwater management techniques such as cisterns and rain
barrels which direct runoff into storage devices, surface or subsurface,
for later reuse, such as for irrigation of gardens and other planted
areas. Because this stormwater is utilized and no pollutant discharge
results, water quality performance is superior to other noninfiltration
BMPs.
CARBONATE BEDROCK
Rock consisting chiefly of carbonate minerals, such as limestone
and dolomite; specifically a sedimentary rock composed of more than
50% by weight of carbonate minerals that underlies soil or other unconsolidated,
superficial material.
CISTERN
An underground reservoir or tank for storing rainwater.
CLOSED DEPRESSION
A distinctive bowl-shaped depression in the land surface.
It is characterized by internal drainage, varying magnitude, and an
unbroken ground surface.
CONSTRUCTED WETLANDS
Constructed wetlands are similar to wet ponds (see below)
and consist of a basin which provides for necessary stormwater storage
as well as a permanent pool or water level, planted with wetland vegetation.
To be successful, constructed wetlands must have adequate natural
hydrology (both runoff inputs as well as soils and water table which
allow for maintenance of a permanent pool of water). In these cases,
the permanent pool must be designed carefully, usually with shallow
edge benches, so that water levels are appropriate to support carefully
selected wetland vegetation.
CULVERT
A pipe, conduit or similar structure including appurtenant
works which carries surface water.
DAM
An artificial barrier, together with its appurtenant works,
constructed for the purpose of impounding or storing water or another
fluid or semifluid or a refuse bank, fill or structure for highway,
railroad or other purposes which does or may impound water or another
fluid or semifluid.
DEP
The Pennsylvania Department of Environmental Protection.
DESIGN STORM
The depth and time distribution of precipitation from a storm
event measured in probability of occurrence (e.g., one-hundred-year
storm) and duration (e.g., twenty-four-hour) and used in computing
stormwater management control systems.
DETENTION BASIN
A basin designed to retard stormwater runoff by temporarily
storing the runoff and releasing it at the appropriate release rate.
DEVELOPER
A person, partnership, association, corporation or other
entity, or any responsible person therein or agent thereof, that undertakes
any regulated activity of this chapter.
DRAINAGE EASEMENT
A right granted by a land owner to a grantee allowing the
use of private land for stormwater management purposes.
DRAINAGE PLAN
The documentation of the proposed stormwater quantity and quality management controls to be used for a given development site, including a BMP operations and maintenance plan, the contents of which are established in §
225-21.
EARTH DISTURBANCE ACTIVITY
A construction or other human activity which disturbs the
surface of the land, including, but not limited to, clearing and grubbing,
grading, excavations, embankments, road maintenance, building construction
and the moving, depositing, stockpiling or storing of soil, rock or
earth materials.
EROSION
The removal of soil particles by the action of water, wind,
ice, or other geological agents.
EXISTING USES
Those uses actually attained in the water body on or after
November 28, 1975, whether or not they are included in the water quality
standards (25 Pa. Code Chapter 93.1).
FILL
Man-made deposits of natural soils or rock products and waste
materials.
FREEBOARD
The incremental depth in a stormwater management structure,
provided as a safety factor of design, above that required to convey
the design runoff event.
HARDSHIP WAIVER REQUEST
A written request for a waiver alleging that the provisions
of this chapter inflict unnecessary hardship upon the applicant. A
hardship waiver does not apply to and is not available from the water
quality provisions of this chapter and should not be granted.
HYDROLOGIC SOIL GROUP (HSG)
Soils are classified into four HSGs (A, B, C and D) to indicate
the minimum infiltration rates, which are obtained for bare soil after
prolonged wetting. The Natural Resources Conservation Service (NRCS)
of the US Department of Agriculture defines the four groups and provides
a list of most of the soils in the United States and their group classification.
The soils in the area of 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 permeable as the
HSG varies from A to D.
HOT SPOT LAND USES
A land use or activity that generates higher concentrations of hydrocarbons, trace metals or other toxic substances than typically found in stormwater runoff. These land uses are listed in §
225-15P.
INFILTRATION PRACTICE
A practice designed to direct runoff into the ground, e.g.,
french drain, seepage pit, seepage trench or bioretention area.
KARST
A type of topography or landscape characterized by depressions,
sinkholes, limestone towers and steep-sided hills, underground drainage
and caves. Karst is usually formed on carbonate rocks, such as limestones
or dolomites and sometimes gypsum.
LAND DEVELOPMENT
Any of the following activities:
(1)
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.
(3)
Development in accordance with Section 503(1.1)
of the Pennsylvania Municipalities Planning Code.
LOADING RATE
The ratio of the land area draining to the system, as modified by the weighting factors in §
225-18B, compared to the base area of the infiltration system.
LOW-IMPACT DEVELOPMENT
A development approach that promotes practices that will
minimize postdevelopment runoff rates and volumes, thereby minimizing
needs for artificial conveyance and storage facilities. Site design
practices include preserving natural drainage features, minimizing
impervious surface area, reducing the hydraulic connectivity of impervious
surfaces and protecting natural depression storage.
MAINSTEM (MAIN CHANNEL)
Any stream segment or other conveyance used as a reach in
the Catasauqua Creek hydrologic model.
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.
MARYLAND STORMWATER DESIGN MANUAL
A stormwater design manual written by the Maryland Department
of the Environment and the Center for Watershed Protection. As of
January 2004, the manual can be obtained through the following website:
www.mde.state.md.us.
MINIMUM DISTURBANCE/MINIMUM MAINTENANCE PRACTICES (MD/MM)
Site design practices in which careful limits are placed
on site clearance prior to development allowing for maximum retention
of existing vegetation (woodlands and other), minimum disturbance
and compaction of existing soil mantle and minimum site application
of chemicals postdevelopment. Typically, MD/MM includes disturbance
setback criteria from buildings as well as related site improvements
such as walkways, driveways, roadways, and any other improvements.
These criteria may vary by community context as well as by type of
development being proposed. Additionally, MD/MM also shall include
provisions (e.g., deed restrictions, conservation easements) to protect
these areas from future disturbance and from application of fertilizers,
pesticides, and herbicides.
NO-HARM OPTION
The option of using a less restrictive runoff quantity control
if it can be shown that adequate and safe runoff conveyance exists
and that the less restrictive control would not adversely affect health,
safety and property.
NPDES
National Pollutant Discharge Elimination System.
NRCS
Natural resources conservation service - U.S. Department
of Agriculture. (Formerly the Soil Conservation Service.)
OIL/WATER SEPARATOR
A structural mechanism designed to remove free oil and grease
(and possibly solids) from stormwater runoff.
OUTFALL
"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.
OWNER
One with an interest in and often dominion over a property.
PEAK DISCHARGE
The maximum rate of flow of stormwater runoff at a given
location and time resulting from a specified storm event.
PENN STATE RUNOFF MODEL (PSRM)
The computer-based hydrologic modeling technique adapted
to each watershed for the Act 167 Plans. The model was calibrated
to reflect actual flow values by adjusting key model input parameters.
PERSON
An individual, partnership, public or private association
or corporation, firm, trust, estate, Borough, governmental unit, public
utility or any other legal entity whatsoever which is recognized by
law as the subject of rights and duties.
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.
PRELIMINARY SITE INVESTIGATION
The determination of the depth to bedrock, the depth to the
seasonal high-water table and the soil permeability for a possible
infiltration location on a site through the use of published data
and on-site surveys. In carbonate bedrock areas, the location of special
geologic features must also be determined along with the associated
buffer distance to the possible infiltration area. See Appendix G.
PUBLIC WATER SYSTEM
A system which provides water to the public for human consumption
which has at least 15 service connections or regularly serves an average
of at least 25 individuals daily at least 60 days out of the year.
(See 25 Pa. Code Chapter 109.)
RATIONAL METHOD
A method of peak runoff calculation using a standardized
runoff coefficient (rational 'c'), acreage of tract and rainfall intensity
determined by return period and by the time necessary for the entire
tract to contribute runoff. The rational method formula is stated
as follows: Q = ciA, where "Q" is the calculated peak flow rate in
cubic feet per second, "c" is the dimensionless runoff coefficient
(see Appendix C), "i" is the rainfall intensity in inches per hour, and
"A" is the area of the tract in acres.
REACH
Any of the natural or man-made runoff conveyance channels
used for watershed runoff modeling purposes to connect the subareas
and transport flows downstream.
RECHARGE VOLUME (REv)
The portion of the water quality volume (WQv) used to maintain groundwater recharge rates at development sites. (See §
225-15J).
REGULATED ACTIVITIES
Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this chapter as specified in §
225-5.
REGULATED EARTH DISTURBANCE ACTIVITY
Earth disturbance activity other than agricultural plowing
or tilling of one acre or more with a point source discharge to surface
waters or to the Borough's storm sewer system or earth disturbance
activity of five acres or more regardless of the planned runoff. This
includes earth disturbance on any portion of, part or during any stage
of a larger common plan of development.
RELEASE RATE
The percentage of the predevelopment peak rate of runoff
for a development site to which the postdevelopment peak rate of runoff
must be controlled to avoid peak flow increases throughout the watershed.
RETURN PERIOD
The average interval in years over which an event of a given
magnitude can be expected to recur. For example, the twenty-five-year-return-period
rainfall or runoff event would be expected to recur on the average
once every 25 years.
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.
RUNOFF
That part of precipitation which flows over the land.
SEDIMENT TRAPS/CATCH BASIN SUMPS
Chambers which provide storage below the outlet in a storm
inlet to collect sediment, debris and associated pollutants, typically
requiring periodic cleanout.
SEEPAGE PIT/SEEPAGE TRENCH
An area of excavated earth filled with loose stone or similar
material and into which surface water is directed for infiltration
into the ground.
SEPARATE STORM SEWER SYSTEM
A conveyance or system of conveyances (including roads with
drainage systems, municipal streets, catch basins, curbs, gutters,
ditches, man-made channels or storm drains) primarily used for collecting
and conveying stormwater runoff.
SHEET FLOW
Stormwater runoff flowing in a thin layer over the ground
surface.
SOIL-COVER-COMPLEX METHOD
A method of runoff computation developed by NRCS which is
based upon relating soil type and land use/cover to a runoff parameter
called a "curve number."
SPECIAL GEOLOGIC FEATURES
Carbonate bedrock features, including but not limited to
closed depressions, existing sinkholes, fracture traces, lineaments,
joints, faults, caves, pinnacles, and geologic contacts between carbonate
and noncarbonate bedrock which may exist and must be identified on
a site when stormwater management BMPs are being considered.
SPILL PREVENTION AND RESPONSE PROGRAM
A program that identifies procedures for preventing and,
as needed, cleaning up potential spills and makes such procedures
known and the necessary equipment available to appropriate personnel.
STATE WATER QUALITY REQUIREMENTS
As defined under state regulations, protection of designated
and existing uses (see 25 Pa. Code Chapters 93 and 96), including:
(1)
Each stream segment in Pennsylvania has a designated
use, such as cold-water fishes or potable water supply, which is listed
in Chapter 93. These uses must be protected and maintained under state
regulations.
(2)
Existing uses are those attained as of November
1975, regardless whether they have been designated in Chapter 93.
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.
(3)
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 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.
STORAGE INDICATION METHOD
A method of routing or moving an inflow hydrograph through
a reservoir or detention structure. The method solves the mass conservation
equation to determine an outflow hydrograph as it leaves the storage
facility.
STORM DRAINAGE PROBLEM AREAS
Areas which lack adequate stormwater collection and/or conveyance
facilities and which present a hazard to persons or property. These
areas are either documented in Appendix B of this chapter or identified by the Borough or Borough Engineer.
STORM SEWER
A system of pipes or other conduits which carries intercepted
surface runoff, street water and other wash waters or drainage, but
excludes domestic sewage and industrial wastes.
STORMWATER
The surface runoff generated by precipitation reaching the
ground surface.
STORMWATER FILTERS
Any number of structural mechanisms such as multichamber
catch basins, sand/peat filters, sand filters, and so forth which
are installed to intercept stormwater flow and remove pollutants prior
to discharge. Typically, these systems require periodic maintenance
and clean out.
STORMWATER MANAGEMENT PLAN
The plan for managing stormwater runoff adopted by Lehigh
and/or Northampton County for the Catasauqua Creek Watershed as required
by the Act of October 4, 1978, P.L. 864, (Act 167), as amended, and
known as the "Stormwater Management Act."
SUBAREA
The smallest unit of watershed breakdown for hydrologic modeling
purposes for which the runoff control 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, impoundments,
ditches, watercourses, storm sewers, lakes, dammed water, wetlands,
ponds, springs and all other bodies or channels of conveyance of surface
water, or parts thereof, whether natural or artificial, within or
on the boundaries of this Commonwealth.
SWALE
A low-lying stretch of land which gathers or carries surface
water runoff. See also "vegetated swale."
TRASH/DEBRIS COLLECTORS
Racks, screens or other similar devices installed in a storm
drainage system to capture coarse pollutants (trash, leaves, etc.).
VEGETATED BUFFERS
Gently sloping areas that convey stormwater as sheet flow
over a broad, densely vegetated earthen area, possibly coupled with
the use of level spreading devices. Vegetated buffers should be situated
on minimally disturbed soils, have low-flow velocities and extended
residence times.
VEGETATED ROOFS
Vegetated systems installed on roofs that generally consist
of a waterproof layer, a root-barrier, drainage layer (optional),
growth media, and suitable vegetation. Vegetated roofs store and eventually
evapotranspirate the collected rooftop rainfall; overflows may be
provided for larger storms.
VEGETATED SWALES
(1)
Vegetated earthen channels designed to convey
stormwater. These swales are not considered to be water quality BMPs.
(2)
Broad, shallow, densely vegetated, earthen channels
designed to treat stormwater while slowly infiltrating, evapotranspirating,
and conveying it. Swales should be gently sloping with low-flow velocities
to prevent erosion. Check dams may be added to enhance performance.
WATERCOURSE
Any channel of conveyance of surface water having defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
WATER QUALITY INSERTS
Any number of commercially available devices that are inserted
into storm inlets to capture sediment, oil, grease, metals, trash,
debris, etc.
WATERSHED
The entire region or area drained by a river or other body
of water, whether natural or artificial.
WET DETENTION PONDS
Basins that provide for necessary stormwater storage as well
as a permanent pool of water. To be successful, wet ponds must have
adequate natural hydrology (both runoff inputs as well as soils and
water table which allow for maintenance of a permanent pool of water)
and must be able to support a healthy aquatic community so as to avoid
creation of mosquito and other health and nuisance problems.