The words "shall" and "must" are mandatory; the words "may" and "should"
are permissive.
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 the natural processes 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, 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.
BEST MANAGEMENT PRACTICE (BMP)
Activities, facilities, measures or procedures used to manage stormwater quantity and quality impacts from the regulated activities listed in §
152-4 of this chapter, 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.
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.
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.
COLLECTOR
Any watercourse, swale, pipe, culvert or other stormwater
control structure receiving runoff from an upstream watershed of 40
acres or less.
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 (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 (formerly
the Pennsylvania Department of Environmental Resources).
DESIGN STORM
The depth and time from a storm event measured in probability
of occurrence (e.g., fifty-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 a predetermined 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.
DIRECT RECHARGE/SUBSURFACE BMP
A BMP designed to direct runoff to groundwater recharge without
providing for vegetative uptake. Examples include infiltration trenches,
seepage beds, drywells and stormwater drainage wells such that nearly
all runoff becomes recharge to groundwater.
DRAINAGE EASEMENT
A right granted by a landowner 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 Operation and Maintenance Plan, the contents of which are established in §
152-15.
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, land development, agricultural
activity, timber harvesting activities road maintenance activities,
mineral extraction, 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 of a stormwater management structure,
provided as a safety factor of design, above that required to control
or 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.
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 Appendix
H of this chapter.
HYDROLOGIC ENGINEERING CENTER-HYDROLOGIC MODELING SYSTEM (HEC-HMS)
The computer-based hydrologic modeling technique developed
by the U.S. Army Corps of Engineers and adapted to the Monocacy Creek
Watershed for the Act 167 Plan Update. The model was "calibrated"
to reflect actual flow values by adjusting key model input parameters.
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. The soils in the area of the development site
may be identified from a web soil survey report that can be accessed
at www.websoilsurvey.sc.egov.usda.gov/App/HomePage.htm.
INFILTRATION PRACTICE
A practice designed to direct runoff into the ground (e.g.,
french drain, seepage pit or seepage trench or bioretention area).
INTERCEPTOR
Any watercourse swale, pipe, culvert or other stormwater
control structure receiving stormwater runoff from an upstream watershed
of over 40 acres.
KARST
A type of topography or landscape characterized by surface
depressions, sinkholes, rock pinnacles and an uneven bedrock structure,
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)
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
(b)
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 MPC.
LOADING RATE
The ratio of the land area draining to the system, as modified by the weighting factors in §
152-9B of this chapter, compared to the base area of the infiltration system.
LOW-IMPACT DEVELOPMENT
A development approach that promotes practices that will
minimize post-development 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 in a single release
rate, dual release rate or conditional no detention I subarea used
as a reach in any DEP approved Act 167 study area hydrologic model.
In conditional no detention II subareas the main channel is the Lehigh
River.
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. The Manual
can be obtained through the following web site: 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 post-development. 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.
MUNICIPALITY
Hanover Township, Northampton County, Pennsylvania.
NO-HARM RUNOFF QUANTITY 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.
NRCS
Natural Resource 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 Township's storm sewer system discharges to waters
of the commonwealth.
OWNER
One with an interest in and often dominion over a property.
PEAK DISCHARGE
The maximum rate of flow of storm runoff at a given location
and time resulting from a specified storm event.
PERSON
An individual, partnership, public or private association
or corporation, firm, trust, estate, municipality, 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 commonwealth
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
of this chapter.
PRETREATMENT
Measures implemented for hot spot land uses designed to reduce
the concentration of hydrocarbons, trace metals and other toxic substances
to levels typically found in stormwater runoff.
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 for peak rate
calculation 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. The rational method formula
for runoff volume calculation is as follows: V = cPA/12 where "c"
and "A" are as noted above, "P" is the total depth of precipitation
for the design event in inches, and "V" is the total runoff volume
in acre-feet.
REACH
Any natural or man-made runoff conveyance channels used for
modeling purposes to connect subareas and transport flows downstream.
REGULATED ACTIVITIES
All activities that may affect stormwater runoff, including
land development and earth disturbance activity, which are subject
to regulation by this chapter.
REGULATED EARTH DISTURBANCE ACTIVITIES
Activity involving earth disturbance, other than agricultural
activity, subject to regulation under 25 Pa. Code 92, 25 Pa. Code
102, or the Clean Streams Law.
RELEASE RATE
The percentage of the predevelopment peak rate of runoff
for a development site to which the post development peak rate of
runoff must be controlled to avoid peak flow increases throughout
the watershed.
RETURN PERIOD
An expression of the intensity of an event based on its statistical
chance of being equalled or exceeded in any given year. An event with
a 1% chance in any given year is stated to have a 100-year return
period. An event with a 50% chance is stated to have a two-year return
period. Over a very long period of record, events might be expected
to recur on average in accordance with their return period.
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.
RUNOFF BMP
A BMP designed for essentially the full volume of runoff
entering the BMP to be discharged off-site.
SCS
The former Soil Conservation Service, U.S. Department of
Agriculture, now known as the "NRCS."
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 clean out.
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 commonwealth regulations, protection of
designated and existing uses (See 25 Pa. Code Chapters 93 and 96),
including:
(1)
Each stream segment in the commonwealth has a designated use,
such as "cold water fishes" or "potable water supply," which is listed
in 25 PA Code 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 25 PA Code 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 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 municipality or Municipal
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 DRAINAGE WELLS
Wells for injection of stormwater to the subsurface that
are regulated by the U.S. Environmental Protection Agency to protect
underground sources of drinking water.
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
Any plan for managing stormwater runoff adopted by Northampton
County for a watershed as required by the Act of October 4, 1978,
P.L. 864 (Act 167), 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
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.
SWALE
A low-lying stretch of land which gathers or carries surface
water runoff.
TIMBER HARVESTING ACTIVITIES
Earth disturbance activities, including the construction
of skid trails, logging roads, landing areas and other similar logging
or silvicultural practices.
TOWNSHIP
Hanover Township, Northampton County.
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. As water quality BMPs, Vegetated
buffers serve to filter pollutants from runoff and promote infiltration.
Vegetated buffers should be situated on minimally disturbed soils,
have low-flow velocities and extended residence times. Vegetated buffers
may be, but are not restricted to, use in riparian (streamside) conditions.
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
Vegetated earthen channels designed to convey and possibly
treat stormwater. As water quality BMPs, these are broad, shallow,
densely vegetated, earthen channels designed to treat stormwater through
infiltration, evapotranspiration and sedimentation. Swales should
be gently sloping with low-flow velocities to prevent erosion. Check
dams may be added to enhance performance.
VEGETATED/SURFACE BMP
A BMP designed to provide vegetative uptake and soil renovation
or surface infiltration of runoff. Capture/reuse BMPs are included
if the captured runoff is applied to vegetated areas. Examples include
bioretention and surface infiltration basins.
WATER QUALITY INSERTS
Any number of commercially available devices that are inserted
into storm inlets to capture sediment, oil, grease, metals, trash,
debris, etc.
WATER QUALITY VOLUME (WQv)
The increase in runoff volume on a development site associated
with a two-year, twenty-four-hour storm event.
WATERCOURSE
Any channel or conveyance of surface water having defined
bed and banks, whether natural or artificial, with perennial or intermittent
flow.
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.
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.