As used in this chapter, the following terms shall have the meanings indicated:
ACCELERATED EROSIONRemoval of the surface of the land through the combined action of man's activities and natural processes at a rate greater than would occur from natural processes alone.
AGRICULTURAL ACTIVITIESThe work of producing crops and raising livestock including tillage, plowing, disking, harrowing, pasturing, nursery, and sod operations, excluding greenhouse structures, and installation of conservation measures. Construction of new buildings or impervious area is not considered an agricultural activity.
ALTERATIONAs 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.
APPLICANTA landowner or other person who has filed an application to the Municipality for approval to engage in any regulated activity defined in §
292-5 of this chapter.
Engineering or site drawings maintained by the contractor as he constructs the project and upon which he documents the actual locations of the building components and changes to the original contract documents. These documents, or a copy of same, are turned over to the Municipal Engineer at the completion of the project.
BANKFULLThe channel at the top-of-bank or point from where water begins to overflow onto a floodplain.
BASEFLOWPortion of stream discharge derived from groundwater; the sustained discharge that does not result from direct runoff or from water diversions, reservoir releases, piped discharges, or other human activities.
BIORETENTIONA stormwater retention area that utilizes woody and herbaceous plants and soils to remove pollutants before infiltration occurs.
BMP (BEST MANAGEMENT PRACTICE)Activities, facilities, designs, measures, or procedures used to manage stormwater impacts from regulated activities, to meet state water quality requirements, to promote infiltration, and to otherwise meet the purposes of this chapter. Stormwater BMPs are commonly grouped into one of two broad categories or measures: "structural" or "nonstructural." In this chapter, nonstructural BMPs or measures include certain low-impact development practices used to minimize the contact of pollutants with stormwater runoff. These practices aim to limit the total volume of stormwater runoff and manage stormwater at its source by techniques such as protecting natural systems and incorporating existing landscape features. Nonstructural BMPs include, but are not limited to, low-impact development practices such as the protection of sensitive and special value features such as wetlands and riparian areas, the preservation of open space while clustering and concentrating development, the reduction of impervious cover, and the disconnection of rooftops from storm sewers. Structural BMPs are those that consist of a physical to capture and treat stormwater runoff. Structural BMPs include, but are not limited to, a wide variety of practices and devices, from large-scale retention ponds and constructed wetlands to small-scale underground treatment systems, infiltration facilities, filter strips, bioretention, wet ponds, permeable paving, grassed swales, riparian buffers, sand filters, detention basins, and manufactured devices. Structural and nonstructural stormwater BMPs are permanent appurtenances to the project Site.
CHANNELAn open drainage feature through which stormwater flows. Channels include, but shall not be limited to, natural and man-made drainageways, swales, streams, ditches, canals, and pipes flowing partly full.
CHANNEL EROSIONThe widening, deepening, or headward cutting of channels and waterways caused by stormwater runoff or bankfull flows.
CISTERNAn underground reservoir or tank for storing rainwater.
CONVEYANCEA natural or man-made, existing, or proposed stormwater management facility, feature or channel used for the transportation or transmission of stormwater from one place to another. For the purposes of this chapter, "conveyance" shall include pipes, drainage ditches, channels, and swales (vegetated and other), gutters, stream channels, and like facilities or features.
CULVERTA structure with its appurtenant works, which carries water under or through an embankment or fill.
DAMA man-made barrier, together with its appurtenant works constructed for the purpose of impounding or storing water or another fluid or semi-fluid. A dam may include a refuse bank, fill, or structure for highway, railroad, or other purposes which impounds or may impound water or another fluid or semi-fluid.
DEPARTMENTThe Pennsylvania Department of Environmental Protection. Also referred to as "DEP," "PA DEP," or "PADEP."
DESIGN PROFESSIONAL (QUALIFIED)A Pennsylvania registered professional engineer, registered landscape architect, registered professional land surveyor trained to develop SWM site plan, or any person licensed by the Pennsylvania Department of State or qualified by law to perform the work required by the chapter.
DESIGN STORMThe magnitude and temporal distribution of precipitation from a storm event measured in probability of occurrence (e.g., a five-year storm) and duration (e.g., 24 hours), used in the design and evaluation of stormwater management systems.
DESIGNEEThe agent of the Delaware County Planning Department, Delaware County Conservation District, and/or agent of the governing body involved with the administration, review, or enforcement of any provisions of this chapter by contract or memorandum of understanding.
DETENTION BASINAn impoundment designed to collect and retard stormwater runoff by temporarily storing the runoff and releasing it at a predetermined rate. Detention basins are designed to drain completely soon after a rainfall event and become dry until the next rainfall event.
DETENTION or TO DETAINThe prevention of, or to prevent, the discharge, directly or indirectly, of a given volume of stormwater runoff into surface waters by temporary storage.
DEVELOPERAny landowner, equitable owner, or authorized agent of such landowner who makes or causes to be made a subdivision of land or a land development.
DEVELOPMENT SITEThe specific tract or parcel of land where any regulated activity set forth in §
292-5 of this chapter is planned, conducted, or maintained.
Any man-made change to improved or unimproved real estate, including but not limited to the construction, reconstruction, renovation, repair, expansion, or alteration of buildings or other structures; the placement of manufactured homes; streets, and other paving; utilities; filling, grading and excavation; mining; dredging; drilling operations; storage of equipment or materials; and the subdivision of land.
DIFFUSED DRAINAGE DISCHARGEDrainage discharge that is not confined to a single point location or channel, including sheet flow or shallow concentrated flow.
DISCHARGE1) (verb) To release water from a project, site, aquifer, drainage basin, or other point of interest; 2) (noun) The rate and volume of flow of water such as in a stream, generally expressed in cubic feet per second (see "peak discharge").
DISTURBED AREAUnstabilized land area where an earth disturbance activity is occurring or has occurred.
DITCHA man-made waterway constructed for irrigation or stormwater conveyance purposes.
DOWNSLOPE PROPERTY LINEThat portion of the property line of the lot, tract, or parcels of land being developed, located such that overland or pipe flow from the project site would be directed towards it by gravity.
DRAINAGE EASEMENTA right-of-way granted to use private land to facilitate the flow of water as deemed necessary by the Township within which the owner shall erect no permanent structures but may use the land in any other way not inconsistent with the grantee's rights.
DRAINAGE FACILITYAny trench, ditch, swale, gutter, pipe, culvert, storm sewer or other similar depression or structure designed, intended or constructed for the purpose of controlling stormwater runoff within a subdivision or groundwater within and away from a subdivision, land development area or contiguous areas.
DRAINAGE PERMITA permit issued by the Municipality after the stormwater management site plan has been approved.
EARTH DISTURBANCE ACTIVITYA 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; the moving, depositing, stockpiling, or storing of soil, rock, or earth materials.
EMERGENCY SPILLWAYA conveyance area that is used to pass peak discharge greater than the maximum design storm controlled by the stormwater facility.
ENCROACHMENTA structure or activity that changes, expands, or diminishes the course, current, or cross-section of a watercourse, floodway, or body of water.
EROSIONThe process by which the surface of the land, including water/stream channels, is worn away by water, wind, or chemical action.
EROSION AND SEDIMENT (E&S) CONTROL PLANA plan that is designed to minimize accelerated erosion and sedimentation. Said plan must be submitted to and approved by the appropriate Conservation District before construction can begin.
EVAPOTRANSPIRATION (ET)The combined processes of evaporation from the water or soil surface and transpiration of water by plants.
EXCEPTIONAL VALUE (EV) WATERSSurface waters of high quality which satisfy Pennsylvania Code Title 25 Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(b) (relating to anti-degradation).
EXISTING CONDITIONSThe initial condition of a project site prior to the proposed alteration. If the initial condition of the site is undeveloped land, the land use shall be considered as "meadow" unless the natural land cover is proven to generate a lower curve number or rational "c" value, such as forested lands.
FEMAFederal Emergency Management Agency.
FINANCIAL HARDSHIPA situation where the greatest possible profit cannot be fully realized from development/redevelopment on a given parcel of land due to added costs or burdens associated with the design, construction, and/or maintenance of stormwater structures, facilities, buffers and/or setbacks.
FLOODA temporary condition of partial or complete inundation of land areas from the overflow of streams, rivers, and other waters of this Commonwealth.
FLOODPLAINAny land area susceptible to inundation by water from any natural source or as delineated by the applicable Department of Housing and Urban Development, Federal Emergency Management Agency (FEMA) maps and studies as being a special flood hazard area.
FLOODWAYThe channel of a watercourse and those portions of the adjoining floodplains which are reasonably required to carry and discharge the 100-year frequency flood (also called the base flood or 1% annual chance flood). Unless otherwise specified, the boundary of the floodway is as indicated on maps and flood insurance studies provided by FEMA. In an area where no FEMA maps or studies have defined the boundary of the 100-year frequency floodway, it is assumed, absent evidence to the contrary, that the floodway extends from the stream to 50 feet from the top-of-bank.
FLUVIAL GEOMORPHOLOGYThe study of landforms associated with river channels and the processes that from them.
FORESTRY (FOREST MANAGEMENT/TIMBER OPERATIONS)The management of forests and timberlands when practiced in accordance with accepted silvicultural principles, through developing, cultivating, harvesting, transporting and selling trees for commercial purposes, which do not involve any land development.
FREEBOARDA vertical distance between the elevation of the design high-water and the top of a dam, levee, tank, basin, swale, or diversion berm. The space is required as a safety margin in a pond or basin.
GRADE1) (noun) A slope, usually of a road, channel, or natural ground, specified in percent and shown on plans as specified herein. 2) (verb) To finish the surface of a roadbed, the top of an embankment, or the bottom of an excavation.
GRASSED WATERWAYA natural or man-made waterway, usually broad and shallow, covered with erosion-resistant grasses used to convey surface water.
GREEN INFRASTRUCTURESystems and practices that use or mimic natural processes to infiltrate, evapotranspire, or reuse stormwater on the site where it is generated. Also referred to as "green stormwater infrastructure (GSI)."
GROUNDWATERWater beneath the earth's surface that supplies wells and springs and is often between saturated soil and rock.
GROUNDWATER RECHARGEReplenishment with water within rock or soil interstices which have the capacity to store water, or which permit the transfer of water to a geologic storage area.
HIGH QUALITY (HQ) WATERSSurface waters having quality which exceeds levels necessary to support propagation of fish, shellfish, and wildlife and recreation in and on the water by satisfying Pennsylvania Code Title 25 Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(a).
HIGH TUNNELA structure which meets the following:
A. Is used for the production, processing, keeping, storing, sale or shelter of an agricultural commodity as defined in section 2 of the Act of December 19, 1974 (P.L. 973, No. 319), known as the "Pennsylvania Farmland and Forest Land Assessment Act of 1974," or the storage of agricultural equipment or supplies; and
Is constructed with all the following:
(1) Has a metal, wood, or plastic frame;
When covered, has a plastic, woven textile, or other flexible covering; and
Has a floor made of soil, crushed stone, matting, pavers, or a floating concrete slab.
HOTSPOTSAreas where land use or activities generate highly contaminated runoff with concentrations of pollutants in excess of those typically found in stormwater.
HYDROGRAPHA graph representing the discharge of water versus time for a selected point in the drainage system.
HYDROLOGIC REGIMEThe hydrologic cycle or balance that sustains quality and quantity of stormwater, baseflow, storage, and groundwater supplies under natural conditions.
HYDROLOGIC SOIL GROUPA classification of soils by the Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service (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.
IMPERVIOUS SURFACEA surface that prevents the infiltration of water into the ground. Impervious surfaces shall include, but are not limited to, streets, sidewalks, pavements, additional indoor living spaces (dwellings), patios, garages, storage sheds, and similar structures, driveway areas, roofs, tennis or other paved courts, swimming pools, artificial turf fields or coverings, and porous pavement or similar surface materials. For the purposes of determining compliance with this chapter, compacted soils or stone surfaces used for vehicle parking and movement shall be considered impervious. Uncompacted gravel areas with no vehicular traffic shall be considered pervious per review by the Municipal Engineer. Surfaces that were designed to allow infiltration (i.e., pavers and areas of porous pavement) may be considered to function as a BMP per review by the Municipal Engineer. Additionally, for the purposes of determining compliance with this chapter, the total horizontal projection area of all ground-mounted and free-standing solar collectors, including solar photovoltaic cells, panels, and arrays, shall be considered pervious so long as the Municipal Engineer determines that the area underneath the solar photovoltaic cells, panels, and arrays is maintained as a vegetated pervious surface.
IMPOUNDMENTA retention or detention basin designed to retain stormwater runoff and release it at a controlled rate.
INFILLDevelopment that occurs on smaller parcels that remain undeveloped but are within or in very close proximity to urban or densely developed areas. Infill development usually relies on existing infrastructure and does not require an extension of water, sewer, or other public utilities.
INFILTRATIONMovement of surface water into the soil, where it is absorbed by plant roots, evaporated into the atmosphere, or percolated downward to recharge groundwater.
INFILTRATION STRUCTURESA structure designed to direct the flow of rain into storage in geologic structures where soils are proven to accommodate the proposed infiltration.
INFLOWThe flow entering the stormwater management facility and/or BMP.
INLETThe upstream end of any structure through which water may flow.
INTERMITTENT STREAMA stream that flows only part of the time. Flow generally occurs for several weeks or months in response to seasonal precipitation or groundwater discharge.
INVERTThe lowest surface, the floor or bottom of a culvert, drain, sewer, channel, basin, BMP, or orifice.
LAND DEVELOPMENTAny 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; 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.
LIMITING ZONEA soil horizon or condition in the soil profile or underlying strata that includes one of the following:
A. A seasonal high-water table, whether perched or regional, determined by direct observation of the water table or indicated by soil mottling.
A rock with open joints, fracture or solution channels, or masses of loose rock fragments, including gravel, with insufficient fine soil to fill the voids between the fragments.
A rock formation, other stratum, or soil condition that is so slowly permeable that it effectively limits downward passage of water.
LOTA contiguous area of land held or to be held in one ownership and not divided by a street, not including any land within the limits of a street right-of-way upon which said lot abuts, even if such right-of-way is maintained by the owner of the lot; a designated parcel, tract or area of land established by a plan and to be used, developed or built upon as a unit.
LOW-IMPACT DEVELOPMENT (LID)Site design approaches and small-scale stormwater management practices that promote the use of natural systems for infiltration, evapotranspiration, and reuse of rainwater. LID can be applied to new development, urban retrofits, and revitalization projects. LID utilizes design techniques that infiltrate, filter, evaporate, and store runoff close to its source. Rather than rely on costly large-scale conveyance and treatment systems, LID addresses stormwater through a variety of small, cost-effective landscape features located on-site.
MAIN STEM (MAIN CHANNEL)Any stream segment or other runoff conveyance used as a reach in watershed-specific hydrologic models.
MANAGED RELEASE CONCEPT (MRC)A post-construction stormwater management (PCSM) strategy that comprises the collection, management, and filtration of captured runoff from the contributing drainage area through a best management practice (BMP) that is preferably vegetated and includes release of a portion of the captured runoff through an underdrain within the BMP. If the MRC BMP is not vegetated, then pretreatment is required to meet water quality requirements. MRC is intended to be used for project areas or subareas where infiltration is considered infeasible to meet regulatory requirements. Refer to the "Managed Release Concept" Version 1.2 (August 25, 2020) guidance document or latest guidance from PA DEP.
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.
MAXIMUM DESIGN STORMThe maximum (largest) design storm that is controlled by the stormwater facility.
MUNICIPAL ENGINEERA professional engineer licensed as such in the Commonwealth of Pennsylvania, duly appointed as the Engineer for a Municipality, planning agency, or joint planning commission.
MUNICIPALITYEdgmont Township, Delaware County, Pennsylvania.
NATURAL RECHARGE AREAUndisturbed surface area or depression where stormwater collects and a portion of which infiltrates and replenishes the underground and groundwater.
NONPOINT SOURCE POLLUTIONPollution that enters a waterbody from diffuse origins in the watershed and does not result from discernible, confined, or discrete conveyances.
NONSTORMWATER DISCHARGESWater flowing in stormwater collection facilities, such as pipes or swales, which is not the result of a rainfall event or snowmelt.
NONSTRUCTURAL BEST MANAGEMENT PRACTICE (BMPs)Methods of controlling stormwater runoff quantity and quality, such as innovative site planning, impervious area and grading reduction, protection of natural depression areas, temporary ponding on site, and other techniques.
NPDESNational Pollutant Discharge Elimination System, the federal government's system for issuance of permits under the Clean Water Act, which is delegated to PADEP in Pennsylvania.
NRCSNatural Resource Conservation Service (previously SCS).
OUTFALL"Point source" as described in 40 CFR § 122.2 at the point where the Municipality's storm sewer system discharges to surface waters of the Commonwealth.
OUTFLOWThe flow exiting the stormwater management facility and/or BMP.
OUTLETPoints of water disposal to a stream, river, lake, tidewater, or artificial drain.
PARENT TRACTThe parcel of land from which a land development or subdivision originates, determined from the date of municipal adoption of this chapter.
PARKING LOT STORAGEInvolves the use of parking areas as temporary impoundments with controlled release rates during rainstorms.
PEAK DISCHARGEThe maximum rate of stormwater runoff from a specific storm event.
PETA domesticated animal (other than a disability assistance animal) kept for amusement or companionship.
PIPEA culvert, closed conduit, or similar structure (including appurtenances) that conveys stormwater.
POINT SOURCEAny discernible, confined, and discrete conveyance including, but not limited to, any pipe, ditch, channel, tunnel, or conduit from which stormwater is or may be discharged, as defined in state regulations at 25 Pennsylvania Code § 92.1.
POST-CONSTRUCTIONPeriod after construction during which disturbed areas are stabilized, stormwater controls are in place and functioning, and all proposed improvement in the approved land development plan are completed.
PRETREATMENTTechniques employed in stormwater BMPs to provide storage or filtering to trap coarse materials and other pollutants before they enter the system, but not necessarily designed to meet the water quality volume requirements of §
292-19.
The specific area of land where any regulated activities in the Municipality are planned, conducted, or maintained.
REACHAny stream segment or other runoff conveyance used in the watershed-specific hydrologic models.
RECHARGEThe replenishment of groundwater through the infiltration of rainfall, other surface waters, or land application of water or treated wastewater.
RECONSTRUCTIONDemolition and subsequent rebuilding of impervious surface.
RECORD DRAWINGSOriginal documents revised to suit the as-built conditions and subsequently provided by the engineer to the client. The engineer reviews the contractor's as-builts against his/her own records for completeness, then either turns these over to the client or transfers the information to a set of reproducibles, in both cases for the client's permanent records.
REDEVELOPMENTAny development that requires demolition or removal of existing structures or impervious surfaces at a site and replacement with new impervious surfaces. Maintenance activities such as top layer grinding, and repaving are not considered to be redevelopment. Interior remodeling projects and tenant improvements are also not considered to be redevelopment.
REGULATED ACTIVITIESAny earth disturbances activities or any activities that involve the alteration or development of land in a manner that may affect stormwater runoff, including redevelopment.
REGULATED IMPERVIOUS SURFACEProposed impervious surface as part of a current proposed activity and all existing impervious surfaces installed after August 22, 2012, as part of a previous activity.
RELEASE RATEThe percentage of existing conditions peak rate of runoff from a site or subarea to which the proposed conditions peak rate of runoff must be reduced to protect downstream areas.
REPAVINGResurfacing of the impervious surface that does not involve reconstruction of an existing paved (impervious) surface.
REPLACEMENT PAVINGReconstruction of and full replacement of an existing paved (impervious) surface.
RETENTION BASINA reservoir, formed from soil or other material, which is designed to retain permanently a certain amount of stormwater from a catchment area and which also may be designed to detain temporarily additional stormwater runoff from the catchment area. Retention basins also may receive fresh water from year-round streams. Retention basins always contain water and thus may be considered man-made lakes or ponds.
RETENTION or TO RETAINThe prevention of direct discharge of stormwater runoff into receiving waters or water bodies by temporary or permanent containment in a pond or depression; examples include systems which discharge by percolation to groundwater, and/or evaporation processes and which generally have residence times of less than three days.
RETURN PERIODThe average interval, in years, within which a storm event of a given magnitude can be expected to recur. For example, the twenty-five-year return period rainfall would be expected to recur on the average of once every 25 years.
RIPARIANPertaining to anything connected with or immediately adjacent to the banks of a stream or other body of water.
RIPARIAN BUFFERAn area of land adjacent to a body of water, including, without limitation, a perennial or intermittent stream, wetlands, and ponds, and managed to maintain the integrity of stream channels and shorelines to reduce the impact of upland sources of pollution by trapping, filtering, and converting sediments, nutrients, and other chemicals; and to supply food, cover, and thermal protection to fish and other wildlife.
RISERA 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 MAINTENANCEEarth 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.
ROOF DRAINSA drainage conduit or pipe that collects water runoff from a roof and leads it away from the structure.
ROOFTOP DETENTIONThe temporary ponding and gradual release of stormwater falling directly onto flat roof surfaces using controlled-flow roof drains in building designs.
RUNOFFAny part of precipitation that flows over the land surface.
SALDOSubdivision and land development ordinance.
SEDIMENTDeposited silt or other matter that is being or has been moved from its site of origin by water or other means of erosion.
SEDIMENT BASINA barrier, dam, or retention or detention basin located and designed in such a way as to retain rock, sand, gravel, silt, or other material transported by water during construction.
SEDIMENT POLLUTIONThe placement, discharge, or any other introduction of sediment into the waters of the Commonwealth.
SEDIMENTATIONThe process by which mineral or organic matter is accumulated or deposited by the movement of water or air.
SEEPAGE PIT/SEEPAGE TRENCHAn area of excavated earth filled with loose stone or similar coarse material into which surface water is directed for infiltration into the underground water.
SEPARATE STORM SEWER SYSTEMA 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 FLOWA flow process associated with broad, shallow water movement on sloping ground surfaces that is not channelized or concentrated.
SOIL COVER COMPLEX METHODA method of runoff computation developed by NRCS that is based on relating soil type and land use/cover to a runoff parameter called curve number (CN).
SPILLWAYA conveyance that is used to pass the peak discharge of the maximum design storm that is controlled by the stormwater facility.
STATE WATER QUALITY REQUIREMENTSThe regulatory requirements to protect, maintain, reclaim, and restore water quality under Pennsylvania Code Title 25 and the Clean Streams Law.
STORAGE INDICATION METHODA 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 FREQUENCYThe 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 SEWERA pipe or conduit that carries intercepted surface runoff, street wash and other wash waters or drainage, but excludes domestic sewage and industrial wastes.
STORMWATERDrainage runoff from the surface of the land resulting from precipitation, snow, or ice melt.
STORMWATER CONTROL MEASUREPhysical features used to effectively control, minimize, and treat stormwater runoff. Also may be referred to as "stormwater management practice (SMP)." [See "best management practice (BMP)"].
STORMWATER MANAGEMENT (SWM) SITE PLANThe plan prepared by the applicant or his representative indicating how stormwater runoff will be managed at the particular site of interest according to this chapter, and including all necessary design drawings, calculations, supporting text, and documentation to demonstrate that chapter requirements have been met, hereafter referred to as "SWM site plan."
STORMWATER MANAGEMENT DISTRICTThose subareas of a watershed in which some type of detention is required to meet the plan requirements and the goals of Act 167.
STORMWATER MANAGEMENT FACILITYAny structure, natural or man-made, that, due to its condition, design, or construction, conveys, stores, or otherwise affects stormwater runoff quality, rate, or quantity, including best management practices and stormwater control measures. Typical stormwater management facilities include, but are not limited to, detention and retention basins, open channels, storm sewers, pipes, and infiltration structures.
STORMWATER MANAGEMENT PLANThe watershed plan for managing stormwater runoff for a watershed, adopted by Delaware and Chester Counties as required by the Act of October 4, 1978, P.L. 864 (Act 167), as amended, and known as the "Storm Water Management Act." See also "watershed stormwater management plan."
STREAM BUFFERThe land area adjacent to each side of a stream essential to maintaining water quality (see also "riparian buffer").
STREAM ENCLOSUREA bridge, culvert, or other structure in excess of 100 feet in length upstream to downstream which encloses a regulated water of the Commonwealth.
SUBAREA (SUBWATERSHED)The smallest drainage unit of a watershed for which stormwater management criteria have been established in the stormwater management plan.
SUBDIVISIONThe 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, conveyance or other 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 COMMONWEALTHAny 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 waters, or parts thereof, whether natural or artificial, within or on the boundaries of the Commonwealth.
SWALEAn elongated depression in the ground which collects and channels surface water runoff.
TIME-OF-CONCENTRATION (Tc)The time required for surface runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed. This time is the combined total of overland flow time and flow time in pipes or channels, if any.
TOP-OF-BANKHighest point of elevation in a stream channel cross-section at which a rising water level just begins to flow out of the channel and over the floodplain.
USDAUnited States Department of Agriculture.
VERNAL PONDSeasonal depressional wetlands that are covered by shallow water for variable periods from winter to spring but may be completely dry for most of the summer and fall.
WATERCOURSEA channel or conveyance of surface water having a defined bed and banks, whether natural or artificial, with perennial or intermittent flow.
WATERS OF THE COMMONWEALTHAny and all rivers, streams, creeks, rivulets, impoundments, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs, and all other bodies or channels of conveyance of surface and underground water, or parts thereof, whether natural or artificial, within or on the boundaries of the Commonwealth.
WATERSHEDRegion or area drained by a river, watercourse, or other body of water, whether natural or artificial.
WATERSHED STORMWATER MANAGEMENT PLANA watershed plan for managing stormwater runoff for a watershed, adopted by Delaware and Chester Counties as required by the Act of October 4, 1978, P.L. 864 (Act 167), as amended, and known as the "Storm Water Management Act" (e.g., Chester Creek, Ridley Creek, Crum Creek, Darby-Cobbs Creeks). See also "stormwater management plan."
WELLHEADA. A structure built over a well;
The source of water for a well.
WELLHEAD PROTECTION AREAThe surface and subsurface area surrounding a water supply well, well field, or spring supplying a public water system through which contaminants are reasonably likely to move toward and reach the water source.
WET BASINPond for urban runoff management that is designed to detain urban runoff and always contains water.
WETLANDAreas with hydric soils that are inundated or saturated by surface and/or groundwater which support hydrophytic vegetation, such as swamps, bogs, marshes and the like, such areas being regulated by the U.S. Army Corps of Engineers and/or the PA DEP.
WOODSA natural groundcover with more than one viable tree of a DBH of six inches or greater per 1,500 square feet which existed within three years of application; a cover condition for which SCS curve numbers have been assigned or to which equivalent Rational Method runoff coefficients have been assigned.