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; words
of masculine gender include feminine gender, and words of feminine gender
include masculine gender.
B.
The words “includes” or “including” shall not limit the term to
the specific example but are 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, 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.”
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Accelerated
Erosion - The removal of the surface of the land through the combined action
of man’s activity and the natural processes at a rate greater than would occur
because of the natural process alone.
Accessory
Structure
- A structure detached from a principal building located on the same lot and
customarily incidental and subordinate to the principal building or use.
Agricultural
Activities
- The work of producing crops and raising livestock including tillage, plowing,
disking, harrowing, pasturing, and installation of conservation measures.
Construction of new buildings or impervious area is not considered an
agricultural activity.
Alteration
- As applied to land, a change in topography as a result of the moving of soil
and rock from one location or position to another; also, the changing of surface
conditions by causing the surface to be more or less impervious; land
disturbance.
Applicant
- A landowner or developer who has submitted a drainage plan or filed an
application for approval to engage in any regulated activities as defined in
Section 104 of this Ordinance.
As-built
Drawings - A
set of engineering or site drawings that delineates the specific permitted
stormwater management facility as actually constructed.
BMP
(Best Management Practice) -
Stormwater structures, facilities, and techniques to maintain or improve the
water quality of surface runoff. Pennsylvania
Handbook of Best Management Practices for Developing Areas, Spring 1998.
Buffer-
see
Riparian Buffer
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 for storing rainwater.
Combined
Sewers
- A sewerage system that carries both sanitary sewage and stormwater runoff.
Conservation
District
- The Delaware and Chester County Conservation Districts as appropriate for the
individual Municipality within the Chester Creek watershed.
Culvert
- A structure with appurtenant works that carries a stream 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.
Deed
Restriction
- See Restrictive Covenant
Design
Storm
- The magnitude and temporal distribution of precipitation from a storm event
measured in probability of occurrence (e.g., a 5-year storm) and duration (e.g.,
24 hours), used in the design and evaluation of stormwater management systems.
Designee
- The agent of the Delaware County Planning Department or the Chester County
Planning Commission and/or agent of the Commissioners involved with the
administration, review, or enforcement of any provisions of this Ordinance by
contract or memorandum of understanding.
Detention
Basin
- An impoundment structure designed to manage stormwater runoff by temporarily
storing the runoff and releasing it at a predetermined rate.
Detention
District
- Those subareas in which some type of detention is required to meet the plan
requirements and the goals of Act 167.
Developer
- A person, partnership, association, corporation, or other entity, or any
responsible person therein or agent thereof, that undertakes any regulated
activity of this Ordinance.
Development
- See Land Development
Development
Site
- The specific tract of land for which a regulated activity is proposed.
Discharge
Easement
- The grant of a property right to allow runoff in excess of the previous
quantity and/or rate of flow.
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 pipe flow from the site would be
directed towards it.
Drainage
Conveyance Facility
- A stormwater management facility designed to transmit stormwater runoff,
including 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 purposes.
Drainage
Permit
- A permit issued by the Municipality after the drainage plan has been approved.
Said permit is issued prior to or with the final municipal approval.
Drainage
Plan
- The documentation of the stormwater management system, if any, to be used for
a given development site, the contents of which are established in Section 304.
Earth
Disturbance
- Any activity including, but not limited to, construction, mining, timber
harvesting, and grubbing which alters, disturbs, and exposes the existing land
surface.
Easement
-
A right-of-way granted, but not dedicated, for limited use of private land
for a public or quasi-public purpose (e.g., utility lines) and within which the
owner of the property shall not erect any permanent structures.
Ephemeral
Streams -
Streams that carry only surface runoff and are dry except during precipitation
events. The groundwater table is
generally located below the bottom of ephemeral streams.
Erosion
- The movement of soil particles by the action of water, wind, ice, or other
natural forces.
Erosion
and Sediment Pollution Control Plan
- A plan that is designed to minimize accelerated erosion and sedimentation.
Said plan must be submitted to and approved by the Delaware or Chester
County Conservation Districts of the appropriate Municipality before
construction can proceed.
Existing
Conditions
- The initial condition of a project site prior to the proposed construction.
If the initial condition of the site is undeveloped land, the land use
shall be considered as “meadow” on “B” soils unless the natural land
cover is proven to generate lower curve numbers or Rational “C” value, such
as forested lands.
Flood
- A general but temporary condition of partial or complete inundation of
normally dry land areas from the overflow of streams, rivers, and other waters
of this Commonwealth.
Floodplain
- 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 Map as being a special flood
hazard area.
Floodway
- The channel of the watercourse and those portions of the adjoining floodplains
that are reasonably required to carry and discharge the 100-year frequency
flood. Unless otherwise specified,
the boundary of the floodway is as indicated on maps and flood insurance studies
provided by the Federal Emergency Management Agency (FEMA).
In an area where no FEMA maps or studies have defined the boundary of the
100-year frequency floodway, it is assumed - absent evidence to the contrary -
that the floodway extends from the stream to fifty (50) feet from the top of the
bank of the stream.
Forest
Management/Timber Operations
- Planning and activities necessary for the management of forest land.
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 natural ground, 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.
Grassed
Waterway
- A natural or constructed waterway, usually broad and shallow, covered with
erosion-resistant grasses, used to conduct surface water from cropland.
Groundwater
Recharge
- Replenishment of existing natural underground water supplies.
Impervious
Surface
– A surface that has been compacted or covered with material to the extent
that it is highly resistant to infiltration by water, including, but not limited
to, conventional impervious surfaces such as paved streets, roofs, compacted
stone, and sidewalks. In addition, the following shall be considered impervious
surfaces when used by motor vehicles: graveled
areas, paver blocks, bricks, and cobblestone.
Impoundment
- A retention or detention basin designed to retain stormwater runoff and
release it at a controlled rate.
Infiltration
Structures
- A structure designed to direct runoff into the ground (e.g., French drains,
seepage pit, and seepage trench).
Inlet
- A surface connection to a closed drain. A
structure at the diversion end of a conduit.
The upstream end of any structure through which water may flow.
Intermittent
Streams - Streams
which flow only during wet seasons. The groundwater table generally is at or
above the bottom of intermittent streams during wet seasons but drops below the
stream bottom during dry seasons. Stream flow in intermittent streams is
primarily due to precipitation but does have some groundwater contribution
during wet seasons.
Land
Development
- (i) 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; (ii) any subdivision of land;
(iii) development in accordance with Section 503(1.1) of the PA Municipalities
Planning Code.
Land/Earth
Disturbance
- Any activity involving grading, tilling, digging, or filling of ground or
stripping of vegetation or any other activity that causes an alteration to the
natural condition of the land.
Main
Stem (Main Channel)
- Any stream segment or other runoff conveyance facility used as a reach in the
Chester Creek hydrologic model.
Manning
Equation in (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.
Municipality
– Aston Township, Delaware County,
Pennsylvania.
Nonpoint
Source Pollution
- Pollution that enters a watery body from diffuse origins in the watershed and
does not result from discernible, confined, or discrete conveyances.
NRCS
- Natural Resource Conservation Service (previously the 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 flowing partly full.
Outfall
- Point where water flows from a conduit, stream, or drain.
Outlet
- Points of water disposal from a stream, river, lake, tidewater, or artificial
drain.
Parking
Lot Storage
- Involves 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.
Penn
State Runoff Model
(calibrated) - A computer-based hydrologic modeling technique.
Perennial
Streams -
Streams that flow year round. Perennial streams derive their flow from both groundwater and
runoff, and the groundwater table never drops below the streambed.
Pipe
- A culvert, closed conduit, or similar structure (including appurtenances) that
conveys stormwater.
Planning
Commission
- The Planning Commission of Aston Township.
PMF
- Probable Maximum Flood
- The flood that may be expected from the most severe combination of critical
meteorologic and hydrologic conditions that are reasonably possible in any area.
The PMF is derived from the probable maximum precipitation (PMP) as
determined based on data obtained from the National Oceanographic and
Atmospheric Administration (NOAA).
Rational
Formula
- A rainfall-runoff relation used to estimate peak flow.
Redevelopment
- Reconstruction of an existing improved, developed property, as of the date of
adoption of this Ordinance.
Regulated
Activities
- Actions or proposed actions that have an impact on stormwater runoff and that
are specified in Section 104 of this Ordinance.
Release
Rate
- The percentage of pre-development peak rate of runoff from a site or subarea
to which the post-development peak rate of runoff must be reduced to protect
downstream areas.
Restrictive
Covenant
- A restriction on the use of land usually set forth in the deed.
Restrictive covenants (a.k.a. deed restrictions) usually run with the
land and are binding upon subsequent owners of the property.
Retention
Basin
- An impoundment in which stormwater is stored and not released during the storm
event. Stored water may be released
from the basin at some time after the end of the storm.
Return
Period
- The average interval, in years, within which a storm event of a given
magnitude can be expected to recur. For example, the 25-year return period rainfall would be
expected to recur on the average once every twenty-five (25) years.
This is more specifically a probability of occurrence.
A 25-year storm has a 4% likelihood of happening in any given year.
Riparian
Buffer
- A vegetative strip paralleling the banks of a perennial or intermittent stream
or other water body (including wetlands and ponds).
The buffer shall contain appropriate native vegetation throughout its
width with the exception of a minimum five-foot wide strip of land maintained in
meadow grass or forbs at its outer boundary.
See also Appendix C, Riparian Buffer Technical Reference Guide.
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.
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.
Sediment
Basin
- A barrier, dam, or retention or detention basin located and designed to retain
rock, sand, gravel, silt, or other material transported by water.
Sediment
Pollution
- The placement, discharge, or any other introduction of sediment into the
waters of the Commonwealth occurring from the failure to design, construct,
implement, or maintain control measures and control facilities in accordance
with the requirements of this Ordinance.
Sedimentation
- The process by which matter is accumulated or deposited by the movement of
water.
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.
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).
Soil
Group, Hydrologic
- A classification of soils by SCS into four runoff potential groups.
The groups range from ‘A’ soils, which are very permeable and produce
little runoff, to ‘D’ soils, which are not very permeable and produce much
more runoff.
Spillway
- A depression in the embankment of a pond or basin that is used to pass the
peak discharge which is greater than the maximum design storm controlled by the
pond.
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
“Return Period.”
Storm
Sewer
- A system of pipes and/or open channels that conveys intercepted runoff and
stormwater from other sources but excludes domestic sewage and industrial
wastes.
Stormwater
- The total amount of precipitation reaching the ground surface.
Stormwater
Management Facility
- Any structure, natural or man-made, that, due to its condition, design, or
construction, conveys, stores, or otherwise affects stormwater runoff.
Typical stormwater management facilities include, but are not limited to,
detention and retention basins, open channels, storm sewers, pipes, and
infiltration structures.
Stormwater
Management Plan
- The plan for managing stormwater runoff in the Chester Creek watershed adopted
by Delaware and Chester Counties as required by the Act of October 4, 1978, P.L.
864, (Act 167), and known as the “Act 167 Stormwater Management Plan, Chester
Creek Watershed.”
Stormwater
Management Site Plan
- The plan prepared by the applicant or his representative indicating how
stormwater runoff will be managed at the particular site of interest according
to this Ordinance.
Stream
Enclosure
- A bridge, culvert, or other structure in excess of one hundred (100) feet in
length upstream to downstream which encloses a regulated water of this
Commonwealth.
Subarea
- The smallest drainage unit of a watershed for which stormwater management
criteria have been established in the Stormwater Management Plan.
Subdivision
- The division or re-division 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, 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 ten (10) acres not involving any new street or easement of access or
any residential dwellings shall be exempt.
Swale
- A low-lying stretch of land that gathers or carries surface water runoff.
Timber
Operations
- See Forest Management
Time
of Concentration (Tc)
- The time 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.
TR-20
- The computer-based hydrologic modeling technique adapted to the Chester Creek
watershed for the Act 167 plan. The model has been “calibrated” to reflect actual
recorded flow values by adjusting key model input parameters.
TR-55
- A method for determining runoff volumes and rates developed by NRCS.
Watercourse
- A 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, 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.
Wetland
- Those 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.