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 activity and natural processes at a rate greater than
would occur because of the natural process alone.
AGRICULTURAL ACTIVITIES
Activities associated with agriculture such as agricultural
cultivation, agricultural operation, and animal-heavy use areas. This
includes the work of producing crops, tillage, land clearing, plowing,
disking, harrowing, planting, harvesting crops, or pasturing and raising
of livestock and installation of conservation measures. The construction
of new buildings or impervious areas, filling and excavating, road
maintenance, maintenance and/or construction of fixed structures involving
earth disturbance activity, and the moving, depositing, stockpiling,
or storing of soil, rock or earth materials shall not be included
in the definition of "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;
changing of surface conditions by causing the surface to be more or
less impervious; land disturbance.
APPLICANT
A landowner, developer, or other person who has filed an
application for approval to engage in any regulated activities at
a project site within the Township of Derry.
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: "nonstructural"
or "structural". "Nonstructural" BMPs are measures referred to as
operational and/or behavior-related practices that attempt to minimize
the contact of pollutants with stormwater runoff whereas "structural"
BMPs are measures 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 wet 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.
BMP MANUAL
The Pennsylvania Stormwater Best Management Practices Manual
as published by the Department of Environmental Protection, Bureau
of Watershed Management, Document No. 363-0300-002, effective date:
December 30, 2006, and as revised.
CHANNEL EROSION
The widening, deepening, and headward cutting of small channels
and waterways, due to erosion caused by moderate to large floods.
CISTERN
An underground reservoir or tank used for storing rainwater.
CONSERVATION DISTRICT
The Dauphin County Conservation District (DCCD). The Dauphin
County Conservation District has the authority under a delegation
agreement executed with the Department of Environmental Protection
to administer and enforce all or a portion of the regulations promulgated
under 25 Pa. Code Chapter 102.
CULVERT
A structure with appurtenant works that carries a stream
and/or stormwater runoff under or through an embankment or fill.
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.
DESIGNEE
The agent of the Township of Derry 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.
DESIGN STORM
The magnitude and temporal distribution of precipitation
from a storm event measured in probability of occurrence (e.g., a
twenty-five-year storm) and duration (e.g., 24 hours), used in the
design and evaluation of stormwater management systems. Also see "return
period."
DETENTION BASIN
An impoundment structure designed to manage stormwater runoff
by temporarily storing the runoff and releasing it at a predetermined
rate.
DETENTION VOLUME
The volume of runoff that is captured and released during
or after a storm event into waters of the commonwealth at a controlled
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.
DEVELOPMENT SITE (SITE)
The specific tract of land for which a regulated activity
is proposed. Also see "project site."
DISTURBED AREA
An unstabilized land area where an earth disturbance activity
is occurring or has occurred.
DOWNSLOPE PROPERTY LINE
That portion of the property line of the lot, tract, or parcels
of land being developed located such that all overland or piped flow
from the site would be directed toward it.
DRAINAGE CONVEYANCE FACILITY
A stormwater management facility designed to convey stormwater
runoff and shall include streams, channels, swales, pipes, conduits,
culverts, storm sewers, etc.
DRAINAGE EASEMENT
A right granted by a landowner to a grantee, allowing the
use of private land for stormwater management, drainage, or conveyance
purposes.
DRAINAGEWAY
Any natural or artificial watercourse, trench, ditch, pipe,
swale, channel, or similar depression into which surface water flows.
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
plowing or tilling, timber harvesting activities, road maintenance
activities, mineral extraction, and the moving, depositing, stockpiling,
or storing of soil, rock, or earth materials.
EROSION
The movement of soil particles by the action of water, wind,
ice, or other natural forces.
EXCEPTIONAL VALUE WATERS
Surface waters of high quality, which satisfies Pa. Code
Title 25, Environmental Protection, Chapter 93, Water Quality Standards,
§ 93.4b(b) (relating to antidegradation).
EXISTING CONDITIONS
The initial condition of a project site prior to the proposed
construction. If the initial condition of the site is not forested
or undeveloped land, the land use shall be considered as "meadow"
unless the natural land cover is documented to generate lower curve
numbers or rational "C" coefficients, such as forested lands.
FEMA
The Federal Emergency Management Agency.
FLOODPLAIN
For the purposes of this chapter, any land area susceptible to inundation by water from any natural source or delineated by applicable Department of Housing and Urban Development, Federal Insurance Administration Flood Hazard Boundary, mapped as being a special flood hazard area. Included are lands adjoining a river or stream that have been or may be inundated by a one-hundred-year flood. Also included are areas that comprise Group 13 Soils, as listed in
Appendix A of the Pennsylvania Department of Environmental Protection (PADEP) Technical Manual for Sewage Enforcement Officers (as amended or replaced from time to time by PADEP).
FLOODWAY
The channel of a river or other watercourse and the adjacent
land areas that must be reserved in order to discharge the base flood
without cumulatively increasing the water surface elevation more than
one foot.
FOREST MANAGEMENT/TIMBER OPERATIONS
Planning and 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, site preparation, and reforestation.
FREEBOARD
A vertical distance between the elevation of the design high
water and the top of a dam, levee, tank, basin, or diversion ridge.
The space is required as a safety margin in a pond or basin.
GRADE
A slope, usually of a road, channel, or ground surface specified
in percent and shown on plans as specified herein.
(TO) GRADE
To finish the surface of a roadbed, top of embankment, or
bottom of excavation.
HEC-HMS MODEL CALIBRATED
(Hydrologic Engineering Center-Hydrologic Modeling System)
A computer-based hydrologic modeling technique adapted to the watersheds
in Dauphin County for the Act 167 Plan. The model has been calibrated
by adjusting key model input parameters.
HIGH QUALITY WATERS
Surface water having quality, which exceeds levels necessary
to support propagation of fish, shellfish, and wildlife and recreation
in and on the water by satisfying Pa. Code Title 25, Environmental
Protection, Chapter 93, Water Quality Standards, § 93.4b(a).
HYDROLOGIC SOIL GROUP (HSG)
Infiltration rates of soils vary widely and are affected
by subsurface permeability as well as surface intake rates. Soils
are classified into one of four HSGs (A, B, C, and D) according to
their minimum infiltration rate, which is obtained for bare soil after
prolonged wetting. The Natural Resource Conservation Service (NRCS)
of the U.S. 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 interest may be identified
from a soil survey report from the local NRCS office or the DCCD.
IMPERVIOUS COVER (a.k.a. IMPERVIOUS SURFACE AND IMPERVIOUS AREA)
A surface of a lot that has been compacted or covered with
material to the extent that it is highly resistant to infiltration
by water. Impervious cover (surfaces or areas) shall include, but
is not limited to: conventional impervious surfaces such as paved
streets, roofs, compacted stone, and sidewalks. Impervious cover shall
consist of the following surfaces when used by motor vehicles or pedestrians:
graveled areas, paver blocks (including voids), bricks, and cobblestone.
The water area of swimming pools shall not be considered to be impervious
surfaces if the overflow system of the pool is connected to a sanitary
sewer system. Decks are not counted as impervious areas if they do
not prevent infiltration. Any surface areas consisting of gravel,
crushed stone, or other porous material shall be assumed to be impervious,
unless designed and approved as an infiltration BMP.
INFILTRATION BMP
Any best management practice stormwater facility designed,
approved, and maintained or used to direct runoff into the ground.
INFILTRATION STRUCTURE
A structure designed to direct runoff into the ground (e.g.,
French drains, seepage pits, seepage trench, etc.).
INLET
A surface connection to a closed drain; a structure at the
diversion end of a conduit; and/or the upstream end of any structure
through which water may flow.
KARST
A type of topography or landscape characterized by surface
depressions, sinkholes, rock pinnacles/uneven bedrock surface, steep-sided
hills, underground drainage, and caves. Karst is formed on carbonate
rocks, such as limestone or dolomites and sometimes gypsum.
LAND DEVELOPMENT or DEVELOPMENT
(1)
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.
[2]
The addition of 2,500 square feet of floor area to a nonresidential
building or residential building, except single-family detached, two-family
detached, single-family semidetached, and single-family attached dwellings.
[3]
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, buildings, groups, or other features.
(2)
Exceptions. The following shall not be construed as land development
activities:
(a)
The conversion of an existing single-family detached dwelling
or single-family semidetached dwelling into not more than three residential
units, unless such units are intended to be a condominium.
(b)
The addition of an accessory building, including farm buildings,
on a lot of an existing principal building.
(c)
The conversion of buildings or rides within the confines of
an enterprise which would be considered an amusement park. For the
purposes of this subsection, an amusement park is defined as a tract
or area used principally as a location for permanent amusement structures
or rides. This exclusion shall not apply to newly acquired acreage
by an amusement park until initial plans for the expanded area have
been approved by the Township.
LIMIT OF DISTURBANCE
A line provided on the SWM site plan that indicates the total
area to be disturbed during a proposed earth disturbance activity.
MAIN STEM (MAIN CHANNEL)
Any stream segment or other runoff conveyance facility used
as a reach in the Dauphin County Act 167 watershed hydrologic model(s).
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.
NOAA ATLAS 14
Precipitation-Frequency Atlas of the United States, Atlas
14, Volume 2, U.S. Department of Commerce, National Oceanic and Atmospheric
Administration, National Weather Service, Hydrometeorological Design
Studies Center, Silver Spring, Maryland (2004) or latest edition.
NOAA's Atlas 14 can be accessed at Internet address: http://hdsc.nws.noaa.gov/hdsc/pfds/.
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.
NRCS
Natural Resource Conservation Service [previously Soil Conservation
Service (SCS)].
OPEN CHANNEL
A drainage element in which stormwater flows with an open
surface. Open channels include, but shall not be limited to, natural
and man-made drainageways, swales, streams, ditches, canals, and pipes
not under pressure.
OUTFALL
i) The point where water flows from a conduit, stream, or
drain; ii) "point source" as described in 40 CFR § 122.2,
the point where the Township's storm sewer system discharges
to surface waters of the commonwealth.
OUTLET
Points of water disposal from a stream, river, lake, tidewater,
or artificial drain.
PADEP
The Pennsylvania Department of Environmental Protection.
PARKING LOT STORAGE
The use of impervious parking areas as temporary impoundments
with controlled release rates during rainstorms.
PEAK DISCHARGE
The maximum rate of stormwater runoff from a specific storm
event.
PERSON
An individual, partnership, public or private association
or corporation; or a governmental unit, public utility, or any other
legal entity whatsoever which is recognized by law as the subject
of rights and duties.
PIPE
A culvert, closed conduit, or similar structure (including
appurtenances) that conveys stormwater.
POINT SOURCE
Any discernible, confined, or 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 § 92.1.
PROBABLE MAXIMUM FLOOD (PMF)
The flood that may be expected from the most severe combination
of critical meteorological and hydrologic conditions that are reasonably
possible in any area. The PMF is derived from the probable maximum
precipitation (PMP) as determined on the basis of data obtained from
the National Oceanographic and Atmospheric Administration (NOAA).
PROJECT SITE
The specific area of land where any regulated activities
in the Township 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.
REDEVELOPMENT
Earth disturbance activities on land which has previously
been developed.
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 predevelopment peak rate of runoff from
a site or subwatershed area to which the postdevelopment peak rate
of runoff must be reduced to protect downstream areas.
RELEASE RATE DISTRICT
Those subwatershed areas in which postdevelopment flows must
be reduced to a certain percentage of predevelopment flows as required
to meet the plan requirements and the goals of Act 167.
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 average interval, in years, within which a storm event
of a given magnitude can be expected to recur. For example, the probability
of a twenty-five-year storm occurring in any one given year is 0.04
(i.e., a four-percent chance).
RIPARIAN BUFFER
A vegetated area bordering perennial and intermittent streams
and wetlands that serves as a protective filter to help protect streams
and wetlands from the impacts of adjacent land uses.
RISER
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.
ROAD MAINTENANCE
Earth disturbance activities within the existing road right-of-way,
such as grading and repairing existing unpaved road surfaces, cutting
road banks, cleaning or clearing drainage ditches, and other similar
activities. Road maintenance activities that do not disturb the subbase
of a paved road such as milling and pavement overlays are not considered
earth disturbance activities.
ROOFTOP DETENTION
Temporary ponding and gradual release of stormwater falling
directly onto flat roof surfaces by incorporating controlled-flow
roof drains into building designs.
RUNOFF
Any part of precipitation that flows over the land surface.
RUNOFF CAPTURE VOLUME
The volume of runoff that is captured (retained) and not
released into surface waters of the commonwealth during or after a
storm event.
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 the movement of water.
SEDIMENT BASIN
A barrier, dam, or detention basin located and designed to
retain rock, sand, gravel, silt, or other material transported by
stormwater runoff.
SEDIMENT POLLUTION
The placement, discharge, or any other introduction of sediment
into waters of the commonwealth occurring from the failure to properly
design, construct, implement, or maintain control measures and control
facilities in accordance with the requirements of this chapter.
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 ground.
SENSITIVE ENVIRONMENTAL AREAS
Sensitive environmental areas shall consist of the following:
(1)
Land areas having slopes in excess of 20% which are not the
result of man-made changes to the natural terrain.
(3)
Areas of quarries, streams, lakes, dams, or ponds and all areas
within 50 feet of such features.
(4)
Cemeteries and all areas within 50 feet of a cemetery.
(5)
Landfills and areas within 50 feet of a landfill.
SEPARATE STORM SEWER SYSTEM
A conveyance or system of conveyances (including roads with
drainage systems, Township streets, catch basins, curbs, gutters,
ditches, man-made channels, or storm drains) primarily used for collecting
and conveying stormwater runoff.
SHEET FLOW
Runoff that flows over the ground surface as a thin, even
layer, not concentrated in a channel.
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).
SPILLWAY (EMERGENCY)
A depression in the embankment of a pond or basin, or other
overflow structure, that is used to pass peak discharges greater than
the maximum design storm controlled by the pond or basin.
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 including, but not limited to:
(1)
Each stream segment in Pennsylvania has a "designated use,"
such as "cold-water fishery" 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
of whether they have been designated in Chapter 93. 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 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.
(4)
Protection and maintenance of water quality in special protection
streams pursuant to 25 Pa. Code, Chapter 93.
STORAGE INDICATION METHOD
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.
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 also "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
Drainage runoff from the surface of the land resulting from
precipitation; or snow or ice melt.
STORMWATER HOTSPOT
A land use or activity that generates higher concentrations
of hydrocarbons, trace metals, or toxicants than are found in typical
stormwater runoff.
STORMWATER MANAGEMENT FACILITIES
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 basins, wet ponds, open channels, storm
sewers, pipes, roof leaders, and infiltration facilities.
STORMWATER MANAGEMENT PLAN
The Dauphin County Stormwater Management Plan for managing
stormwater runoff in Dauphin County as required by the Act of October
4, 1978, P.L. 864, (Act 167) and known as the "Stormwater Management
Act."
STREAM ENCLOSURE
A bridge, culvert, or other structure in excess of 100 feet
in length upstream to downstream which encloses regulated waters of
the commonwealth.
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, easement of access, or any residential
dwelling, shall be exempted.
SUBWATERSHED AREA
The smallest drainage unit of a watershed for which stormwater
management criteria has been established in the stormwater management
plan.
SUPERVISORS
The Board of Supervisors of the Township of Derry, Dauphin
County, PA.
SWALE
A low-lying stretch of land that gathers or carries surface
water runoff.
TIME OF CONCENTRATION (Tc)
The time for surface runoff to travel from the most hydraulically
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.
TOWNSHIP
Township of Derry, Dauphin County, Pennsylvania.
USDA
The United States Department of Agriculture.
WATERCOURSE
A channel or conveyance of surface water, such as a stream
or creek, having defined bed and banks, whether natural or artificial,
with perennial or intermittent flow.
WATERSHED
Region or area drained by a river, watercourse, or other
surface water, whether natural or artificial.
WATERS OF THE COMMONWEALTH
Rivers, streams, creeks, rivulets, impoundments, ditches,
watercourses, storm sewers, lakes, dammed water, wetlands, ponds,
springs, and other bodies or channels of conveyance of surface and
underground water, or parts thereof, whether natural or artificial,
within or on the boundaries of the Commonwealth of Pennsylvania.
WETLANDS
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, and which may be identified as jurisdictional
wetlands using methods described in the current edition of the "Federal
Manual for Identifying and Delineating Jurisdictional Wetlands."