As used in this chapter, the following terms shall have the meanings indicated:
ACCELERATED EROSIONThe removal of the surface of the land through the combined action of man's activity and the natural processes of a rate greater than would occur because of the natural process alone.
AGRICULTURAL ACTIVITYActivities 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 as the result of changing the land cover including the water, vegetation and bare soil.
APPLICANTA person who has filed an application for approval to engage in any regulated activity defined in §
206-5.
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 qualified professional at the completion of the project.
BANKFULLThe channel at the top-of-bank, or point from where water begins to overflow onto a floodplain.
BASE FLOWPortion 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.
BEST MANAGEMENT PRACTICES (BMP)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, 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, low-impact design, bioretention, wet ponds, permeable paving, grassed swales, riparian or forested buffers, sand filters, detention basins, and manufactured devices. Structural stormwater BMPs are permanent appurtenances to the project site.
BIORETENTIONA stormwater retention area that utilizes woody and herbaceous plants and soils to remove pollutants before infiltration occurs.
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 watercourses, swales, streams, ditches, canals, and pipes that convey continuously or periodically flowing water.
CISTERNAn underground reservoir or tank for storing rainwater.
CONSERVATION DISTRICTThe Montgomery County Conservation District (MCCD). A 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.
CULVERTA structure, with its appurtenant works, which carries water under or through an embankment or fill.
CURVE NUMBERValue used in the Soil Cover Complex Method. It is a measure of the percentage of precipitation which is expected to run off from the watershed and is a function of the soil, vegetative cover, and tillage method.
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 which impounds or may impound water or another fluid or semifluid.
DEPARTMENT (DEP)The Pennsylvania Department of Environmental Protection (PADEP).
DESIGN PROFESSIONAL (QUALIFIED)A Pennsylvania-registered professional engineer, registered landscape architect or registered professional land surveyor trained to develop stormwater management plans.
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. 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 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.
DEVELOPERAny landowner, agent of such landowner or tenant with the permission of such landowner who makes or causes to be made a subdivision of land or a land development or who seeks to undertake any regulated earth disturbance activity.
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, drilling, and site alteration such as embankments, dredging, grubbing, grading, paving, parking or storage facilities, excavation, filling, stockpiling, or clearing. As used in this chapter, "development" encompasses both new development and redevelopment.
DEVELOPMENT SITEThe specific tract or parcel of land where any regulated activity set forth in §
206-5 is planned, conducted or maintained.
Drainage discharge that is not confined to a single point location or channel, including sheet flow or shallow concentrated flow.
DISCHARGEA. (verb) To release water from a project, site, aquifer, drainage basin or other point of interest (verb);
(noun) The rate and volume of flow of water such as in a stream, generally expressed in cubic feet per second. See also "peak discharge."
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 as specified in Appendix C, Disconnected Impervious Area.
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.
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.
DRAINAGE PERMITA permit issued by the Township after the SWM site plan has been approved.
EARTH DISTURBANCE ACTIVITYA construction or other human activity that disturbs the surface of 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.
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, including water/stream channels, is worn away by water, wind, or chemical action.
EROSION AND SEDIMENT CONTROL PLANA site-specific plan identifying BMPs to minimize accelerated erosion and sedimentation. For agricultural plowing or tilling activities, the erosion and sediment control plan is that portion of a conservation plan identifying BMPs to minimize accelerated erosion and sedimentation.
EXCEPTIONAL VALUE WATERSSurface waters of high quality which satisfy Pennsylvania Code Title 25 Environmental Protection, Chapter 93, Water Quality Standards, § 93.4b(b) (relating to antidegradation).
EXISTING CONDITIONSThe dominant land cover during the five-year period immediately preceding a proposed regulated activity.
EXISTING RECHARGE AREAUndisturbed surface area or depression where stormwater collects and a portion of which infiltrates and replenishes the groundwater.
EXISTING RESOURCES AND SITE ANALYSIS MAPA base map which identifies fundamental environmental site information including floodplains, wetlands, topography, vegetative site features, natural areas, prime agricultural land and areas supportive of endangered species.
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 as delineated by applicable Department of Housing and Urban Development, Federal Insurance Administration Flood Hazard Boundary Map as being a special flood hazard area. That area defined in the Township Zoning Ordinance as the Floodplain Conservation District; the floodplain definition contained therein is made part of this chapter by reference. Also includes areas that comprise Group 13 soils, as listed in Appendix A of the Pennsylvania DEP Technical Manual for Sewage Enforcement Officers (as amended or replaced from time to time by DEP).
FLOODWAYThe channel of a 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 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 100-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.
FOREST MANAGEMENT/TIMBER OPERATIONSPlanning and associated 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, 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.
GRADEA. (noun) A slope, usually of a road, channel or natural ground specified in percent and shown on plans as specified herein.
(verb) To finish the surface of a roadbed, the top of an embankment, or the bottom of excavation.
GREEN INFRASTRUCTURESystems and practices that use or mimic natural processes to infiltrate, evapotranspire, or reuse stormwater on the site where it is generated.
GROUNDWATERWater beneath the earth's surface that supplies wells and springs, and is often between saturated soil and rock.
GROUNDWATER RECHARGEThe replenishment of existing natural underground water supplies from rain 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 Neshaminy Creek Watershed during the Act 167 Plan development and was the basis for the standards and criteria of this chapter.
HIGH QUALITY 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).
HOTSPOTAn area where land use or activity generates highly contaminated runoff, with concentrations of pollutants in excess of those typically found in stormwater. Typical pollutant loadings in stormwater may be found in Chapter
8, Section 6, of the Pennsylvania Stormwater Best Management Practices Manual, Pennsylvania Department of Environmental Protection (PADEP) No. 363-0300-002 (2006). More information concerning hotspots may be found in §
206-6.
A 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 GROUP (HSG)Infiltration rates of soils vary widely and are affected by subsurface permeability as well as surface intake rates. A classification of soils by the Natural Resources Conservation Service, formerly the Soil Conservation Service, 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. The NRCS defines the four groups and provides a list of most of the soils in the United States and their group classification. The soils in the area of the development site may be identified from a soil survey report that can be obtained from local NRCS offices or conservation district offices. Soils become less pervious as the HSG varies from A to D (NRCS).
IMPERVIOUS MATERIALAny materials that do not permit the natural absorption and permeation by soils of rain or other surface water, to include but not be limited to all concrete, asphalt, and similar paving products, earthen materials (brick, stone), chemical treatment of soils or artificial ground covers as may be used in the construction of roads, walks, driveways, parking areas, patios and recreation facilities.
IMPERVIOUS SURFACEA surface that prevents the infiltration of water into the ground. Impervious surfaces include, but are not limited to, streets, sidewalks, pavement roofs, or driveway areas. Any surface areas designed to be gravel or crushed stone shall be regarded as impervious surfaces.
IMPOUNDMENTA retention or detention basin designed to retain stormwater runoff and release it at a controlled rate.
INFILL DEVELOPMENTDevelopment that occurs on smaller parcels that remain undeveloped but are within or 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 STRUCTUREA structure designed to direct runoff into the underground water (e.g., french drains, seepage pits, or seepage trenches).
INITIAL ABSTRACTION (IA)The value used to calculate the volume or peak rate of runoff in the Soil Cover Complex Method. It represents the depth of rain retained on vegetation plus the depth of rain stored on the soil surface plus the depth of rain infiltrated prior to the start of runoff.
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.
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 Pennsylvania 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.
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 the applicable watershed hydrologic model.
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.
MCCDThe Montgomery County Conservation District.
MUNICIPALITYMontgomery Township, Montgomery County, Pennsylvania.
NESHAMINY CREEK WATERSHED ACT 167 STORMWATER MANAGEMENT PLANThe watershed plan for managing those land use activities that will influence stormwater runoff quality and quantity and that would impact the Neshaminy Creek Watershed adopted by Bucks and Montgomery Counties as required by the Act of October 4, 1978, P.L. 864 (Act 167).
NONPOINT SOURCE POLLUTIONPollution that enters a water body 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.
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 Soil Conservation Service).
OUTFALL"Point source" as described in 40 CFR 122.2 at the point where the Township's storm sewer system discharges to surface waters of the commonwealth.
OUTLETPoints of water disposal to a stream, river, lake, tidewater or artificial drain.
PADEPThe Pennsylvania Department of Environmental Protection.
PARENT TRACTThe parcel of land from which a land development or subdivision originates, determined from the date of Township adoption of this chapter.
PEAK DISCHARGEThe maximum rate of stormwater runoff from a specific storm event.
PERENNIAL STREAMA stream which contains water at all times except during extreme drought.
PERVIOUS SURFACEA surface that allows the infiltration of water into the ground.
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 Pa. Code § 92.1.
POSTCONSTRUCTIONPeriod 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 volume requirements of §
206-17. 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 Township are planned, conducted or maintained.
QUALIFIED PROFESSIONALAny person licensed by the Pennsylvania Department of State or otherwise qualified by law to perform the work required by this chapter.
RECHARGEThe replenishment of groundwater through the infiltration of rainfall, other surface waters, or land application of water or treated wastewater.
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-built drawings 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. Record drawings are not the same as record plans submitted for recording with the county in accordance with the Pennsylvania Municipalities Planning Code (Act 247).
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. Utility trenches in streets are not considered redevelopment unless more than 50% of the street width including shoulders is removed and repaved.
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 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 structure in which stormwater is stored and not released during the storm event. Retention basins are designed for infiltration purposes, and do not have an outlet. The retention basin must infiltrate stored water in four days or less.
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 PERIOD (or AVERAGE RECURRENCE INTERVAL)The average interval, in years, within which a storm event of a given or greater magnitude can be expected to recur. The reciprocal of the return period is the annual exceedance probability of the storm event, that is, the probabilty that the storm event is equaled or exceeded in any one-year period. 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 1/25 or 4% chance of occurrence or exceedance in any given year.
RIPARIAN BUFFERA permanent area of trees and shrubs located adjacent to streams, lakes, ponds and wetlands.
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 DRAINA drainage conduit or pipe that collects water runoff from a roof and leads it away from the structure.
RUNOFFAny part of precipitation, as well as any other flow contributions, that flows over the land surface.
SALDOSubdivision and Land Development Ordinance.
SEDIMENTSoils or other materials transported by water, air or gravity as a product of erosion.
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, air or gravity. Once this matter is deposited (or remains suspended), it is usually referred to as "sediment."
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. More information on seepage pits may be found in the PA BMP Manual, December 2006, Chapter 6, Section 4.
SEPARATE STORM SEWER SYSTEMA 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 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 the NRCS that is based on relating soil type and land use/cover to a runoff parameter called Curve Number (CN).
SPECIAL PROTECTION SUBWATERSHEDSWatersheds that have been designated in Pa. Code Title 25, Environmental Protection, Chapter 93, Water Quality Standards, as exceptional value (EV) or high quality (HQ) waters.
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 Title 25 of the Pennsylvania Code and the Clean Streams Law.
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 system of pipes and/or open channels that convey intercepted runoff and stormwater from other sources, but excludes domestic sewage and industrial wastes.
STORMWATERThe surface runoff generated by precipitation reaching the ground surface.
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. 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 or plans for managing those land use activities that will influence stormwater runoff quality and quantity and that would impact the watershed adopted Montgomery County as required by the Act of October 4,1978, P.L. 864 (Act 167).
STORMWATER 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.
STREAMA flow of water in a natural channel or bed, as a brook, rivulet, or a small river.
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.
STREAM BANK EROSIONThe widening, deepening, or headward cutting of channels and waterways, caused by stormwater runoff or bankfull flows.
SUBAREA (SUBWATERSHED)The smallest drainage unit of a watershed for which stormwater management criteria have been established in the stormwater management plan.
SUBDIVISIONAs defined in the Pennsylvania Municipalities Planning Code, Act of July 31, 1968, P.L. 805, No. 247.
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.
SWALEA low-lying stretch of land that gathers or carries surface water runoff.
SWM SITE PLANThe documentation of the stormwater management system to be used for a given development site, the contents of which are established in §
206-25.
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.
TOWNSHIPMontgomery Township, Montgomery County, Pennsylvania.
TOWNSHIP ENGINEERA professional engineer licensed as such in the Commonwealth of Pennsylvania, duly appointed as the engineer for Montgomery Township.
USDAUnited States Department of Agriculture.
VEGETATED SWALEA natural or man-made waterway, usually broad and shallow, covered with erosion-resistant grasses, used to convey surface water.
VERNAL POOLSeasonal 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, 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.
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. Wetlands generally include swamps, marshes, bogs, fens, and similar areas.
WISSAHICKON CREEK ACT 167 PLANThe watershed 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 Philadelphia and Montgomery Counties as required by the Act of October 4,1978, P.L. 864 (Act 167).