As used in this chapter, the following terms shall have the meanings indicated:
ACCELERATED EROSION — The removal of the surf ace of the land through the combination of human activity and natural processes at a rate greater than would occur due to natural processes alone.
AGRICULTURAL ACTIVITIES — The work of producing crops and raising livestock, including tillage, plowing, discing, harrowing, pasturing and installation of conservation measures. Construction of new buildings or impervious areas in support of agricultural activities is not considered agricultural activities.
APPLICANT — A landowner, as herein defined, or agent of the landowner, who has filed an application for a stormwater management permit or other approval under this chapter.
BASE FLOW — Stream flow originating from groundwater seepage into a streambed and any releases from impoundment structures.
BEST MANAGEMENT PRACTICE (BMP) — Structural and nonstructural measures, including activities, facilities, designs, measures or procedures, used to manage stormwater runoff to meet water quality requirements and to reduce flooding, to promote groundwater recharge and to otherwise meet the purposes of this chapter and federal and state stormwater regulations. BMPs include but are not limited to infiltration, filter strips, low-impact design, bioretention, wet ponds, permeable paving, grassed swales, forested buffers, sand filters and detention basins.
BIORETENTION AREA — Stormwater management measure which involves the shallow, temporary ponding of stormwater runoff in areas with well-drained soils and native vegetation.
BUILDING — Any structure, either temporary or permanent, having enclosed walls and a roof, located on the land, designed or used for the shelter of any person, animal or property, and occupying more than 100 square feet of area.
CHANNEL EROSION — The widening, deepening and headward cutting of small channels and waterways due to erosion caused by water flows.
CISTERN — An underground reservoir or tank for storing rainwater. CONSERVATION DISTRICT — The Montgomery County Conservation District.
CULVERT — A pipe, conduit or similar structure, including appurtenant works, which carries surface water.
DAM — A refuse bank, fill, structure or artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or other fluid.
DEDICATION — The deliberate donation of property by its owner for public use.
DEP — The Pennsylvania Department of Environmental Protection or its predecessor or successor agencies.
DESIGN STORM — The magnitude of precipitation from a storm event measured in probability of occurrence (e.g., fifty-year storm) and duration (e.g., twenty-four-hour), and used in computing stormwater management control systems.
DETENTION BASIN — A stormwater management structure with a controlled release rate which is essentially dry while not receiving stormwater.
DEVELOPER — Any landowner, agent of such landowner or tenant who, with the permission of such landowner, makes or causes to be made a subdivision of land or a land development or who undertakes a regulated activity as defined herein.
DEVELOPMENT — Any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures, the placement of mobile homes, streets and other paving, utilities, filling, grading, excavation, mining, dredging or drilling operations and the subdivision of land. This term includes redevelopment.
DEVELOPMENT SITE — The specific tract of land for which a development is proposed, conducted or maintained.
DOWNSLOPE PROPERTY LINE — That portion of the property line of a lot, tract or parcel of land being developed which is located such that all overland or pipe (low of stormwater from the site would be directed towards it.
DRAINAGE EASEMENT — A right granted by a landowner to a grantee, including an association or the Township, allowing the use of private land for stormwater management purposes.
DRAINAGE FACILITY — Any ditch, pipe, culvert, storm sewer, stream, channel, swale, conduit or other structure or feature designed, intended or constructed for the purpose of diverting surface water from or carrying surface waters off streets, public rights-of-way, parks, recreational areas or any part of any subdivision or land development.
DRAINAGE PERMIT — A permit issued by the Township after a stormwater management plan has been approved. Said permit is issued prior to or with a final land development approval.
DRY WELL — Below-grade stormwater retention structure that is open at the base, allowing water to percolate to the underlying soil.
EARTH DISTURBANCE — Any activity, including, but not limited to, grading, construction, mining, timber harvesting, clearing and grubbing, and stockpiling or storage which alters, disturbs and exposes the surface of the land greater than 5,000 square feet. See also "land disturbance."
EROSION — The removal or wearing away of the surface of the land by the action of natural processes, including the action of water, wind and ice, and chemicals.
EROSION AND SEDIMENT POLLUTION CONTROL PLAN — A plan, which designates measures to be employed to minimize accelerated erosion and sedimentation.
EXISTING CONDITIONS — The initial condition of a project site prior to the proposed construction, earth disturbance, clearing, grubbing or filling. 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.
FEMA — Federal Emergency Management Agency.
FILL —
A. (Verb) Any action by which earth, sand, gravel, rock or any other acceptable material is deposited, placed, pushed, dumped, pulled, transported or moved to a new location.
B. (Noun) Earth, sand, gravel, earth or other material permitted and acceptable by law to be placed or deposited to form an embankment or raise the elevation of the land surface. The term includes material used to replace an area of aquatic life with dry land or to change the bottom elevation of a regulated water of the commonwealth.
FLOOD — A temporary condition of partial or complete inundation of normally dry land areas from excessive surface water or the overflow of streams, rivers and other waters of the commonwealth and waters of the United States. The action by which a flood occurs.
FLOODPLAIN — The area along a watercourse which is periodically flooded by water therefrom, as defined by the Township Code, Chapter 255, Zoning, Article XXII, Floodplain Conservation District.
FLOODWAY — The channel of a watercourse and those portions of the adjoining floodplains which 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 maps 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 from the watercourse to 50 feet from the top of the bank of the watercourse or as determined by § 255-161A(4), whichever distance from the top of bank is greater.
FREEBOARD — A vertical distance between the elevation of the design high water and the top of the berm or embankment of a stormwater management structure. The space is required as a safety margin in a pond or a basin to prevent overtopping.
GRADE —
A. (Noun) A slope of a street, pipe, culvert, channel or natural ground, specified as a percentage or ratio and shown on plans as specified herein.
B. (Verb) To finish or work the surface of the land, a roadbed, top of embankment or bottom of excavation.
C. GRADE, EXISTING — The vertical elevation of the ground surface prior to earthmoving, filling or other land disturbance.
D. GRADE, FINAL — The final vertical elevation of the ground after earthmoving, filling or other land disturbance.
GRASSED WATERWAY — A natural or constructed waterway, usually broad and shallow, used to convey surface water.
GROUNDWATER — The water beneath the surface of the ground, the source of water in springs and wells and base flow in streams.
GROUNDWATER RECHARGE — Replenishment of the water beneath the surface of the ground, the source of water in springs and wells. Infiltration of precipitation and its movement to the water table is one form of natural recharge.
GROUNDWATER RECHARGE DESIGN STORM — Benchmark rainfall event used as a basis for establishing compliance with the groundwater recharge requirement of this chapter: seventy-five-hundredths-inch, twenty-four-hour rainfall.
IMPERVIOUS SURFACE — Any material placed on or above the earth, or any material change in the natural surface of the earth, which substantially reduces or prevents the natural infiltration of water. Examples include but are not limited to structures, including eaves, roofs, and roof overhangs; roads; parking areas (whether hard surfaced or not); driveways; sidewalks; walkways; patios; sports courts; pools; and, the horizontal surface area of aboveground stormwater management structures, including retention and detention basins. Stormwater basins designed and constructed to allow for infiltration shall not be considered as impervious surface. Patios designed and constructed with pervious materials shall not be considered as impervious surface. [Amended 4-12-2016 by Ord. No. 16-1316]
IMPOUNDMENT — A retention or detention basin designed to manage stormwater runoff by retaining it or releasing it at a controlled rate.
INFILTRATION STRUCTURE — A structure designed to direct runoff into the ground, (e.g., seepage pits, infiltration trench).
LAND DEVELOPMENT — Any of the following activities:
A. The improvement of one lot or two or more contiguous lots, tracts or parcels of land for any purpose involving:
(1) A group of two or more residential or nonresidential buildings, whether proposed initially or cumulatively, or a single nonresidential building on a lot or lots, regardless of the number of occupants or tenure; or
(2) The division, subdivision or allocation of land or space, whether initially or cumulatively, between or among two or more existing or prospective parcels, owners, tenants or occupants by means of or for the purpose of lots, streets, common areas, leaseholds, condominiums, building groups or other features.
B. A subdivision of land.
C. Any activity regulated as development in accordance the Municipalities Planning Code and any amendments thereto.
LAND DISTURBANCE — Any activity involving grading, tilling, digging, filling of ground, clearing, grubbing, stripping of vegetation or any other activity that causes an alteration to the natural condition of the land. See also "earth disturbance."
LANDOWNER — The legal, beneficial or equitable owner or owners of land, including the holder of an option or contract to purchase (whether or not such option or contract is subject to any condition), a lessee, if he is authorized under the lease to exercise the rights of the landowner, or other person having a proprietary interest in land.
MANNING'S EQUATION — A method for calculation of flow velocity (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.
MUNICIPALITIES PLANNING CODE — Pennsylvania Municipalities Planning Code, Act of July 31, 1968, P.L. 805, No. 247, as reenacted and amended December 31, 1988, P.L. 1329, No. 170, as amended, 53 P.S. § 10101 et seq., and any further amendments thereto.
MUNICIPAL SEPARATE STORM SEWER SYSTEM (MS4) — A means of conveyance or system of conveyances (including roads with drainage systems, public streets, catch basins, curbs, gutters, ditches, channels or storm drains) owned or operated by the state, a municipality or other public body and designed or used for collecting or conveying storm water, and which is not a combined sewer and which is not part of a publicly owned treatment works.
NONPOINT SOURCE POLLUTION — Pollution that enters a waterway or body from diffuse origins in the watershed and does not result from a discernible, confined or discrete conveyance.
NPDES — National Pollutant Discharge Elimination System, the federal government's system for issuance of permits under the Clean Water Act, which is delegated to DEP, and to the Conservation District to a limited extent.
NRCS — Natural Resource Conservation Service, previously known as the Soil Conservation Service ("SCS").
OPEN CHANNEL — A drainage conveyance in which stormwater flows with an open surface. Open channels include, but shall not be limited to, natural and man-made drainageways, swales, streams, ditches, canals and pipes flowing partly full.
OUTFALL — Point where water discharges from a conduit, pipe, or other drainage conveyance. "Point source," as described in 40 CFR § 122.2, at the point where the MS4 discharges to surface waters of the commonwealth.
OUTLET — Point of water discharge from a watercourse, stream, river, lake or artificial drain.
PEAK DISCHARGE — The maximum rate of flow of stormwater runoff at a given point and time resulting from a specified storm event, expressed as volume per unit of time (cubic feet per second).
PERSON — An individual, partnership, public or private association or corporation, or a governmental unit, public utility or any other legal entity whatsoever which is recognized by law as the subject of rights and duties.
PIPE — A culvert, closed conduit or similar structure (including appurtenances) that conveys stormwater.
POINT SOURCE — Any discernible, confined 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.
PROJECT SITE — The specific area of land where any regulated activity in the Township is planned, conducted or maintained.
RAPARIAN CORRIDOR — A vegetated or natural area directly adjacent to (or surrounding) a water body, including watercourses, ponds, lakes and wetlands, that serves a variety of functions important to the health and welfare of humans and the environment. A riparian corridor is determined by boundaries set by a horizontal measurement extending from the top of bank or high water mark of a water body to one foot above the one-hundred-year base flood elevation, or, alternatively, a horizontal measurement extending 50 feet from the top of bank or high water mark of the water body, whichever distance is greater.
RATIONAL METHOD (FORMULA) — A precipitation-runoff relation used to estimate peak discharge.
REDEVELOPMENT — Earth disturbance activity on land which has previously been disturbed or developed.
REGULATED ACTIVITIES —
A. Actions or proposed actions which affect stormwater runoff and which are governed by this chapter.
B. Earth disturbance activity one acre or more in area with a point source discharge to surface waters or the Township's MS4, or five acres or more regardless of the planned runoff. This includes earth disturbance on any portion of, part of or during any stage of a larger common plan of development. This only includes road maintenance activities involving 25 acres or more of earth disturbance.
RETENTION BASIN — A stormwater management structure with a controlled release rate which maintains a constant water level while not receiving stormwater.
RETENTION VOLUME — The combined storage volume provided by BMPs on a site for the retention and eventual infiltration or evaporation of precipitation.
RETURN PERIOD — The average interval, in years, within which a storm event of a given magnitude can be expected to recur. A storm with a probability of occurrence of four percent in any year. See "storm frequency."
RISER — A vertical pipe extending from the bottom of a pond or basin that is used to control the discharge rate from the pond or basin for a specified design storm.
ROAD MAINTENANCE — Earth disturbance activities within the existing road cross-section and right-of-way, such as grading and repairing existing unpaved road surfaces, cutting road banks, cleaning or clearing drainage ditches and other similar activities.
ROOFTOP DETENTION — Temporary capture and gradual release of precipitation falling directly onto a roof surface by incorporating controlled flow roof drains into building designs.
RUNOFF — The surface water discharge of a given watershed after precipitation that does not enter the soil but runs off the surface of the land.
SEDIMENT — Solid material, both mineral and organic, that is in suspension, is being transported or has been moved from its site of origin or has been deposited by water.
SEDIMENT BASIN — A barrier, dam, retention or detention structure designed to capture sediment.
SEDIMENT POLLUTION — The placement, discharge or any other introduction of sediment into the waters of the commonwealth occurring from the failure to design, construct, implement or maintain control measures and control facilities in accordance with the requirements of this chapter.
SEDIMENTATION — The process by which mineral or organic matter is accumulated or deposited by wind, water or gravity. Once this matter is deposited (or remains suspended in water), it is usually referred to as "sediment."
SEEPAGE PIT OR SEEPAGE TRENCH — An area of excavated earth filled with loose stone or similar material and lined with filter fabric into which surface water is directed for infiltration into the ground. Also known as an "infiltration pit" or "infiltration trench."
SEMIPERVIOUS SURFACE — A surface, such as turf, stone, porous paving or other material, which allows some percolation or infiltration of water into the ground.
SHEET FLOW — Runoff which flows over the ground surface as a thin, even layer not concentrated in a channel.
SINGLE ENTITY — An association, public or private corporation. partnership, firm, trust, estate or any other legal entity empowered to own real estate exclusive of an individual lot owner.
SOIL COVER COMPLEX METHOD — A method of runoff volume computation developed by the Natural Resource Conservation Service. Soil type, land use/cover, rainfall amounts and moisture conditions are related to the predicted runoff volume for a single rainfall event.
SOIL GROUP, HYDROLOGIC — A classification of soils by the Natural Resource Conservation Service into four runoff potential groups. The groups are distinguished by letters A through D. The soils represent a range of drainage capabilities from A soils that are very permeable and produce little runoff to D soils, which are not very permeable and produce much more runoff.
SPILLWAY — A depression in or a stormwater system through the embankment of a stormwater management structure which is used to pass peak discharge greater than the maximum design storm controlled by the structure.
STATE WATER QUALITY REQUIREMENTS — As defined under state regulations, protection of "designated" and "existing uses" (see 25 Pa. Code chapters 93 and 96).
A. Each stream segment in Pennsylvania has a "designated use," such as "cold water fishery" or "potable water supply," which are listed in 25 Pa. Code chapter 93. These uses must be protected and maintained, under state regulations.
B. "Existing uses" are those attained as of November 1975, regardless whether they have been designated in 25 Pa. Code chapter 93. Earth disturbance activities must be designed to protect and maintain existing uses and maintain the level of water quality necessary to protect those uses in all streams and to protect and maintain water quality in special protection streams.
C. Water quality is a function of the chemical, biological and physical characteristics of surface water bodies. After regulated earth disturbance activities are complete, these characteristics can be impacted by addition of pollutants, such as sediment, and changes in habitat through increased flow volumes and/or rates as a result of changes in land surface area from those activities. Therefore, permanent discharges to surface waters must be managed to protect the streambank, streambed and structural integrity of the waterway to prevent these impacts.
STORM FREQUENCY — The number of times that a given storm event occurs or is equaled or exceeded on the average in a given year. See "return period."
STORM SEWER — A 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. Excludes domestic sewage and industrial waste systems.
STORMWATER — The total amount of precipitation reaching the ground surface.
STORMWATER DETENTION FACILITY — Stormwater detention facilities include all structural measures whose principle purpose is the attenuation of incoming runoff peak discharge rates, All stormwater detention facilities incorporate a method of restricting outflow and a storage volume for the temporary detention of incoming runoff. Stormwater detention facilities include both above-grade and below-grade devices. See also "detention basin."
STORMWATER MANAGEMENT FACILITY OR STRUCTURE — Any structure, natural or man-made, that, due to its condition, design or construction, conveys, stores or otherwise controls stormwater runoff. Typical stormwater management facilities include, but are not limited to, detention and retention basins, open channels, storm sewers, pipes and infiltration structures, Referred to as a "storm water management structure" when man-made.
STORMWATER MANAGEMENT PLAN — The depiction, to scale, of the stormwater management facilities, BMPs, design and techniques, if any, to be used for a given development site, including drainage areas, pipes, inlets, culverts, basins and appurtenances.
STREAM — A watercourse.
STREAM ENCLOSURE — A bridge, culvert, pipe or other structure which encloses a watercourse. A permit to construct such an enclosure is required for an enclosure greater than 100 feet in length.
SUBDIVISION — The division or redivision of a lot, tract or parcel of land by any means into two or more lots, tracts, parcels or other divisions of land, including changes in existing lot lines for the purpose, whether immediate or future, of lease, partition by the court for distribution to heirs or devisees, transfer of ownership or building or lot development; provided, however, that the subdivision by lease of land for agricultural purposes into parcels of more than ten acres, not involving any new street or easement of access or any residential dwelling, shall be exempt.
SWALE — A low-lying stretch of land which intercepts, collects or carries surface water runoff.
TIME OF CONCENTRATION (TC) — The time for surface runoff to travel from the hydraulically most distant point in the watershed to a point of interest within the watershed. This time is the combined total of overland flow time and flow time in pipes or channels, if any.
TOWNSHIP — The Township of Upper Dublin, Montgomery County, Pennsylvania.
TOWNSHIP CODE — The Code of the Township of Upper Dublin.
WATER QUALITY DESIGN STORM — Benchmark rainfall event used as a basis for establishing compliance with the water quality requirement of this chapter: one-year, twenty-four-hour rainfall.
WATERCOURSE — A channel or conveyance of surface water, such as a stream or creek, having defined bed and banks, whether natural or artificial, with perennial or intermittent flow.
WATERSHED — The area contained within a drainage divide above a specified point on a stream. In water-supply engineering it is termed a watershed, and in river-control engineering it is termed a drainage area, drainage basin or catchment area.
WATERS OF THE COMMONWEALTH — Any and all rivers, streams, creeks, rivulets, ditches, watercourses, storm sewers, lakes, dammed water, wetlands, ponds, springs, and all other bodies or channels of conveyance of surface and underground water, or parts thereof, whether natural or artificial, within or on the boundaries of the Commonwealth of Pennsylvania.
WETLAND — Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstance do support, a prevalence of vegetation typically adapted for life in saturated soil conditions, including swamps, marshes, bogs, ferns and similar areas, as defined by the U.S. Army Corps of Engineers.