ACCELERATED EROSIONThe removal of the surface of the land through the combined action of man's activity and the natural processes at a rate greater than that which would occur because of natural process alone.
AGRICULTURAL ACTIVITIESActivities 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.
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, developer or other person who has filed an application to the municipality for approval to engage in any regulated activity at a project site in the municipality.
AS-BUILT DRAWINGSEngineering or site drawings maintained by a developer to show the actual locations of building components and changes from the original contract documents. These documents, or a copy of same, are turned over to the municipality 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 groundwater recharge 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 refer to operational and/or behavior-related practices that attempt to minimize the contact of pollutants with stormwater runoff, or to provide other environmental or aesthetic benefits such as low-impact designs, riparian or forested buffers; whereas structural BMPs or measures are those 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 retention ponds and constructed wetlands, to small-scale underground treatment systems, infiltration facilities, filter strips, bioretention, wet ponds, permeable paving, grassed swales, sand filters, detention basins, and manufactured devices. Structural stormwater BMPs are permanent appurtenances to the project site.
BMP MANUALPennsylvania Stormwater Best Management Practices Manual, No. 363-0300-002 (December 2006).
BUFFERThe area of land immediately adjacent to any stream, measured perpendicular to and horizontally from the top-of-bank on both sides of a stream (see "top-of-bank").
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.
CONSERVATION DISTRICTA conservation district, as defined in Section 3(c) of the Conservation District Law [3 P.S. § 851(c)], that has the authority under a delegation agreement executed with DEP to administer and enforce all or a portion of the regulations promulgated under 25 Pa. Code Chapter 102.
CONVEYANCEA facility or structure used for the transportation or transmission of something from one place to another.
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 semifluid. A dam may include a refuse bank, fill, or structure for highway, railroad, or other purposes that impounds or may impound water or another fluid or semifluid.
DEP (or PADEP)The Pennsylvania Department of Environmental Protection.
DESIGN STORMThe magnitude and temporal distribution of precipitation from a storm event measured in probability of occurrence that such magnitude will be equaled or exceeded in any one year (e.g., the twenty-percent chance, or so-called five-year (recurrence interval) storm), and duration (e.g., twenty-four hours), used in the design and evaluation of stormwater management systems. Also see "return period."
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 to become dry until the next rainfall event.
DETENTION VOLUMEThe volume of runoff that is captured and released into the waters of the commonwealth at a controlled rate.
DEVELOPERA person who seeks to undertake any regulated earth disturbance activities at a project site in the municipality.
DEVELOPMENTAny human-induced change to improved or unimproved real estate, whether public or private, including, but not limited to, land development, construction, installation, or expansion of a building or other structure, land division, street construction, and site alteration such as embankments, dredging, grubbing, grading, paving, parking or storage facilities, excavation, filling, stockpiling, or clearing.
DIAMETER AT BREAST HEIGHT (DBH)The outside bark diameter at breast height which is defined as 4.5 feet (1.37m) above the forest floor on the uphill side of the tree.
DIFFUSED DRAINAGE DISCHARGEDrainage discharge that is not confined to a single point location or channel, including sheet flow or shallow concentrated flow.
DIRECTLY CONNECTED IMPERVIOUS AREA (DCIA)An impervious or impermeable surface that is directly connected to a stormwater drainage or conveyance system, leading to direct runoff, decreased infiltration, decreased filtration, and decreased time of concentration.
DISCONNECTED IMPERVIOUS AREA (DIA)An impervious or impermeable surface that is disconnected from any stormwater drainage or conveyance system, and is redirected or directed to a pervious area, which allows for infiltration, filtration, and increased time of concentration.
DISTURBED AREAAn unstabilized 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 CONVEYANCE FACILITYA stormwater management facility designed to transport stormwater runoff that includes channels, swales, pipes, conduits, culverts, and storm sewers.
DRAINAGE EASEMENTA right granted by a landowner to a grantee allowing the use of private land for stormwater management purposes.
EARTH DISTURBANCE ACTIVITYA construction or other human activity which disturbs the surface of land including, but not limited to, clearing and grubbing, grading, filling, excavations, embankments, land development, agricultural plowing or tilling, timber harvesting activities, road maintenance activities, mineral or fluid extraction, and 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 natural process by which the surface of the land is worn away by water, wind or chemical action.
EXCEPTIONAL VALUE WATERSSurface waters having quality that satisfy one or more of the conditions established in Pennsylvania Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(b).
EXISTING CONDITIONThe dominant land cover during the five-year period immediately preceding a proposed regulated activity. If the initial condition of the site is undeveloped land, the land use shall be considered as "meadow" unless the municipality determines that the natural land cover has a lower Curve Number (CN) or Rational "c" value, such as forested lands.
FEMAFederal Emergency Management Agency.
FLOODA temporary condition of partial or complete inundation of land areas from the overflow of streams, rivers, and other waters of the commonwealth.
FLOODPLAINAny land area susceptible to inundation by water from any natural source or delineated by applicable FEMA maps and studies as being a special flood hazard area. Included are lands adjoining a river or stream that have been or may be expected to be inundated by a one-hundred-year flood, i.e., the flood of magnitude that has a one-percent chance of being equaled or exceeded in any given year.
FLOODWAYThe channel of a watercourse and those portions of the adjoining floodplains that are reasonably required to carry and discharge the one-hundred-year frequency flood. Unless otherwise specified, the boundary of the floodway is as indicated on Flood Insurance Rate Maps (FIRMs) and flood insurance studies provided by FEMA. In an area where no FEMA maps or studies have defined the boundary of the one-hundred-year frequency floodway, it is assumed, absent evidence to the contrary, that the floodway extends 50 feet from the top-of-bank on each side of the stream.
FLUVIAL GEOMORPHOLOGYThe study of landforms associated with river channels and the processes that form them.
FOREST MANAGEMENT/TIMBER OPERATIONSPlanning and associated activities necessary for the management of forest lands. 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.
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.
GROUNDWATERWater beneath the earth's surface that supplies wells and springs and is within the saturated zone of soil and rock.
GROUNDWATER RECHARGEThe replenishment of existing natural underground water supplies from precipitation or overland flow.
HEC-HMSThe U.S. Army Corps of Engineers, Hydrologic Engineering Center (HEC) — Hydrologic Modeling System (HMS). This model was used to model the Wissahickon Creek Watershed during the Act 167 plan development and is the basis for the standards and criteria of this chapter.
HIGH QUALITY WATERSSurface waters having quality that satisfy one or more of the conditions established by Pennsylvania Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(a).
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 at 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 GROUP (HSG)Infiltration rates of soils vary widely and are affected by subsurface permeability as well as surface intake rates. Soils are classified into four HSGs (A, B, C, and D) according to their minimum infiltration rate, which is obtained for bare soil after prolonged wetting. The NRCS defines the four groups and provides a list of most of the soils in the United States and their group classifications. 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 pervious as the HSG varies from A to D (NRCS).
IMPERVIOUS SURFACE (IMPERVIOUS AREA)A surface that prevents the infiltration of water into the ground. Impervious surfaces (or areas) shall include, but not be limited to, roofs, additional indoor living spaces, patios, garages, storage sheds and similar structures, swimming pools, and any new streets or sidewalks. Decks, parking areas, and driveway areas are not counted as impervious areas if they do not prevent infiltration.
IMPOUNDMENTA retention or detention basin designed to retain stormwater runoff and release it at a controlled rate.
INFILLDevelopment that occurs on smaller parcels that have remained undeveloped, but is 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 BASINA shallow impoundment that is designed to infiltrate stormwater into the soil. Infiltration basins are believed to have a high pollutant removal efficiency, and can also help recharge the groundwater, thus restoring baseflows to stream systems. Infiltration basins can be problematic at many sites because of stringent soil requirements.
INFILTRATION STRUCTURESA structure designed to direct runoff into the underground water (e.g., French drains, seepage pits, seepage trenches, or infiltration galleries).
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.
KARSTA type of topography or landscape characterized by surface depressions, sinkholes, rock pinnacles/uneven bedrock surface, underground drainage and caves. Karst is formed on carbonate rocks, such as limestone or dolomite.
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;
Development in accordance with Section 503(1.1) of the PA Municipalities Planning Code.
LIMITING ZONEA soil horizon or condition in the soil profile or underlying a stratum 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 sufficient 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 designated parcel, tract, or area of land established by a plat or otherwise as permitted by law and to be used, developed, or built upon as a unit.
MAIN STEM (MAIN CHANNEL)Any stream segment or other runoff conveyance used as a reach in the Wissahickon Creek Watershed hydrologic model.
MANNING EQUATION (MANNING FORMULA)A method for calculation of velocity of flow (e.g., feet per second) and flow or discharge 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 (PE) licensed as such in the Commonwealth of Pennsylvania, duly appointed as the engineer for a municipality, planning agency, or joint planning commission.
MUNICIPALITYCheltenham Township, Montgomery 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 are 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 DEP in Pennsylvania.
NRCSNatural Resource Conservation Service of the U.S. Department of Agriculture [previously the Soil Conservation Service (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.
PIPEA culvert, closed conduit, or similar structure (including appurtenances) that conveys stormwater.
POST-CONSTRUCTIONPeriod after construction during which disturbed areas are stabilized, stormwater controls are in place and functioning, and all proposed improvements 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 control requirements (WQ
v) of §
291-406. For example, any inlets draining to an infiltrating system should be sumped and trapped to prevent the system from becoming clogged with excess sediment.
The specific area of land where any regulated activities in the municipality are planned, conducted, or maintained.
QUALIFIED PERSONAny person licensed by the Pennsylvania Department of State or otherwise qualified by law to perform the work required by this chapter.
REACHAny stream segment or other runoff conveyance used in the Wissahickon Creek Watershed hydrologic model.
RECHARGEThe replenishment of groundwater through the infiltration of rainfall, other surface waters, or land application of water or treated wastewater.
RECHARGE VOLUME (Rev)The volume of stormwater, in cubic feet, required to be infiltrated on site, where practicable and appropriate.
RECONSTRUCTIONDemolition and subsequent rebuilding of impervious surface.
RECORD DRAWINGSConstruction drawings revised to represent the as-built conditions.
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 disturbance activities or any activities that involve the alteration or development of land in a manner that may affect stormwater runoff.
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.
REPAVINGReplacement of an impervious surface that does not involve reconstruction of an existing paved (impervious) surface (e.g., addition of a new layer of asphalt over an existing paved surface).
REPLACEMENT PAVINGReconstruction of and full replacement of an existing paved (impervious) surface (e.g., demolition and removal of surface layer, foundation, and base course; and subsequent reconstruction of the entire sequence).
RETENTION VOLUME/REMOVED RUNOFFThe volume of runoff that is captured and not released directly into the surface waters of the commonwealth during or after a storm event.
RETURN PERIODThe average interval, in years, within which a storm event of a given or greater 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, or conversely would have a four-percent chance of occurrence or exceedance in any given year.
RIPARIAN BUFFERAn area of land adjacent to a body of water and managed to maintain the integrity of stream channels and shorelines to 1) reduce the impact of upland sources of pollution by trapping, filtering, and converting sediments, nutrients, and other chemicals, and 2) supply food, cover and thermal protection to fish and other wildlife.
RIPARIAN FOREST BUFFERA type of riparian buffer that consists of permanent vegetation that is predominantly native trees, shrubs, and forbs along surface waters that is maintained in a natural state or sustainably managed to protect and enhance water quality, stabilize stream channels and banks, and separate land use activities from surface waters.
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.
SEDIMENTSoils or other materials transported by surface water as a product of erosion.
SEDIMENT BASINA barrier, dam, or retention or detention basin located and designed in such a way as to retain rock, gravel, sand, silt, clay 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.
STANDARD GRADING PERMITThe permit required to be issued by the municipality before any grading activities are allowed to commence on a site within the municipality. Such permits typically require information including, but not limited to, a contour map of the site showing existing and proposed contours, a plot plan showing streams and drainage courses on or within 50 feet of the site, drainage structures, neighboring streets and alleys, trees, and floodplain zones on or within 50 feet of the site, soil classifications.
STATE WATER QUALITY REQUIREMENTSThe regulatory requirements to protect, maintain, reclaim, and restore water quality under Title 25 of the Pennsylvania Code 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.
STORM FREQUENCYThe number of times that a given storm "event" occurs or is exceeded on average in a stated period of years (see "return period").
STORM SEWERA system of pipes and/or open channels that convey intercepted runoff and stormwater from other sources but exclude domestic sewage and industrial wastes.
STORMWATERDrainage runoff from the surface of the land resulting from precipitation or snow or ice melt.
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 FACILITY (SMF)Any structure, natural or man-made, that, due to its condition, design, or construction, conveys, stores, or otherwise affects stormwater runoff quality, rate, or quantity. Typical stormwater management facilities include, but are not limited to, detention and infiltration basins, open channels, storm sewers, pipes, and infiltration structures.
STORMWATER MANAGEMENT PLANThe watershed plan, known as the "Wissahickon Creek Watershed Act 167 Stormwater Management Plan," for managing those land use activities that will influence stormwater runoff quality and quantity, and that would impact the Wissahickon Creek Watershed adopted by Montgomery and Philadelphia Counties as required by the Act of October 4, 1978, P.L. 864 (Act 167).
STORMWATER MANAGEMENT SITE PLAN (SWM SITE PLAN)The plan prepared by the applicant or the applicant's representative indicating how stormwater runoff will be managed a project site to meet the requirements of this chapter. Small project SWM site plans may be prepared for certain projects.
STREAM BUFFERThe land area adjacent to each side of a stream essential to maintaining water quality (see "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, 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. As defined in the Pennsylvania Municipalities Planning Code, Act of July 31, 1968, P.L. 805, No. 247.
SURFACE WATERSPerennial 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.
SWALEA low-lying stretch of land that gathers or carries surface water runoff.
TIME-OF-CONCENTRATION (Tc)The time required for surface runoff to travel from the most remote point of a watershed to the watershed outlet.
TOP-OF-BANKHighest point of elevation in a stream channel cross-section at which a rising water level just begins to flow outside 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.
WATER VOLUME CONTROL(See §
291-406.) The storage capacity, in acre-feet, required to capture and treat a portion of stormwater runoff from the developed or redeveloped areas of the site.
A channel or conveyance of surface water having a defined bed and banks, whether natural or artificial, with perennial or intermittent flow.
WATERS OF THE COMMONWEALTHRivers, streams, creeks, rivulets, impoundments, ditches, watercourses, storm sewers, lakes, dammed water, 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.
WATERSHEDRegion or area drained by a river, watercourse or other surface water of the commonwealth.
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.
WETLANDThose 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.
WOODSA natural groundcover with more than one viable tree of a DBH of six inches or greater per 1,500 square feet which existed for a minimum of three consecutive years.