[Ord. No. 2023-01, 5/1/2023]
As used in this chapter, the following terms shall have the meanings indicated:
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.
ANTI-SEEP COLLARSAn impermeable diaphragm usually of sheet metal or concrete constructed at intervals within the zone of saturation along the conduit of a principal spillway to increase the seepage length along the conduit and thereby prevent piping or seepage along the conduit.
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.
BEST MANAGEMENT PRACTICE (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 behaviorrelated 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.
BMP MANUALPennsylvania Department of Environmental Protection's Stormwater Best Management Practices Manual, No. 363-0300-002 (December 2006), as amended.
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.
Any structure or practice that is designed and/or constructed to transmit or otherwise transfer stormwater runoff from one location to another. Typical conveyance facilities include, but are not limited to: swales and other open channel facilities, storm sewers, and pipe culverts.
DEPThe Pennsylvania Department of Environmental Protection.
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. Also see "Return Period."
DETENTION VOLUMEThe volume of runoff that is captured and released into the waters of the commonwealth at a controlled rate.
DISTURBED AREAAn unstabilized land area where an earth disturbance activity is occurring or has occurred.
DUMPINGThe unregulated disposal of waste, including, but not limited to, construction refuse, paint, petrochemicals, domestic solid waste.
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; and the moving, depositing, stockpiling, or storing of soil, rock, or earth materials.
EROSIONThe natural process by which the surface of the land is worn away by water, wind, or chemical action.
EROSION AND SEDIMENT CONTROL FACILITY (ESC FACILITY)Any structure or practice that is designed and/or constructed to capture, reduce, prevent, or otherwise mitigate the effects of stormwater runoff and sedimentation. Typical erosion and sediment control facilities include, but are not limited to: erosion control matting, silt fence, silt sock, inlet protection, temporary seeding, and sediment ponds.
EXISTING CONDITIONThe dominant land cover during the five-year period immediately preceding a proposed regulated activity.
FEMAFederal Emergency Management Agency.
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. 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 the watercourse and those portions of the adjoining floodplains that are reasonably required to carry and discharge the 100-year 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 floodway, it is assumed, absent evidence to the contrary, that the floodway extends from the stream to 50 feet from the top of the bank of the stream.
FOREST MANAGEMENT/TIMBER OPERATIONSPlanning and activities necessary for the management of forestland. These include conducting a timber inventory, preparation of forest management plans, silvicultural treatment, cutting budgets, logging road design and construction, timber harvesting, site preparation, and reforestation.
GREEN INFRASTRUCTURESystems and practices that use or mimic natural processes to infiltrate, evapotranspirate, or reuse stormwater on the site where it is generated.
GUTTERSA depression that runs parallel to a road and is designed to collect rainwater that flows along the street diverting it into a stormwater conveyance facility.
HEC-RASA software that allows the user to perform one-dimensional steady flow, one and two-dimensional unsteady flow calculations, sediment transport/mobile bed computations, and water temperature/water quality modeling.
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 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 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, and any new streets or sidewalks. Decks, parking areas, and driveway areas are not counted as impervious areas if they do not prevent infiltration.
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 DEVELOPMENT (DEVELOPMENT)Inclusive of any or all of the following meanings: (i) the improvement of one lot or two or more contiguous lots, tracts, or parcels of land for any purpose involving: (a) a group of two or more buildings, or (b) the division or allocation of land or space between or among two or more existing or prospective occupants by means of, or for the purpose of, streets, common areas, leaseholds, condominiums, building groups, or other features; (ii) any subdivision of land; (iii) development in accordance with Section 503(1.1) of the Pa. Municipalities Planning Code.
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.
LOW-FLOW CHANNELA channel designed to move water rapidly during small storm events to nearby watercourses.
MANNING'S EQUATIONAn equation used to calculate open channel flow. It is an empirical equation that applies to uniform flow in open channels and is a function of the channel velocity, flow area and channel slope.
MUNICIPALITYLondonderry Township, Dauphin County, Pennsylvania.
NATIVE PLANTA plant occurring naturally in the south-central Pennsylvania region, ecosystem, or habitat without human introduction.
NONPOINT SOURCE POLLUTIONPollutants carried into waterways such as rivers, streams, lakes, wetlands, and groundwater from rain and snowmelt.
NRCSUSDA Natural Resources Conservation Service (previously SCS).
OPERATION AND MAINTENANCE (O&M)Activities to ensure that stormwater practices will continue to function properly and yield expected water quality and environmental benefits, protect public safety, meet legal standards, and protect communities' financial investment.
PEAK DISCHARGEThe maximum rate of stormwater runoff from a specific storm event.
PROJECT SITEThe specific area of land where any regulated activities in the Municipality 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.
REGULATED ACTIVITIESAny earth disturbance activities or any activities that involve the alteration or development of land in a manner that may affect stormwater runoff.
RETENTION VOLUME/REMOVED RUNOFFThe volume of runoff that is captured and not released directly into the surface waters of this commonwealth during or after a storm event.
RETURN PERIODThe average interval, in years, within which a storm event of a given magnitude can be expected to occur one time. For example, the twenty-five-year return period rainfall would be expected to occur on average once every 25 years; or stated in another way, the probability of a twenty-five-year storm occurring in any one year is 0.04 (i.e., a 4% chance).
RIPARIAN BUFFERA permanent area of trees and shrubs located adjacent to streams, lakes, ponds and wetlands.
RUNOFFAny part of precipitation that flows over the land.
SEDIMENTSoils or other materials transported by surface water as a product of erosion.
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.
Drainage runoff from the surface of the land resulting from precipitation or snow or ice melt.
STORMWATER MANAGEMENT FACILITY (SWM FACILITY)Any structure, natural or man-made, that, due to its condition, design, or construction, conveys, stores, or otherwise affects stormwater runoff. Typical stormwater management facilities include, but are not limited to: detention and retention basins, rain gardens, and infiltration facilities.
STORMWATER MANAGEMENT PERMITThe permit issued by the Township in response to an application prepared by an applicant or its representative that provides necessary details, including, but not limited to disturbance area, impervious areas, and other items. "Stormwater management permit" will be designated as "SWM permit" throughout this chapter, and shall be divided into two categories:
1. MINOR SWM PERMITRegulated activities that result in: the alteration or development of 1,000-4,999 square feet of land in a manner that affects stormwater runoff; earth disturbances of 5,000 to 43,559 square feet; and/or the cumulative increase of 1,000-4,999 square feet of impervious area. "Cumulative" shall include incremental and phased development. (for example: adding a 1,000-square-foot patio onto a home will require a minor SWM permit).
MAJOR SWM PERMITRegulated activities that result in: the alteration or development of greater than or equal to 5,000 square feet of land in a manner that may affect stormwater runoff; earth disturbances of greater than or equal to 43,560 square feet; and/or the cumulative increase of greater than or equal to 5,000 square feet of impervious area. Regulated activities taking place on sites: (A) with greater than or equal to 5,000 square feet of existing impervious area; (B) that are not controlling the runoff from the existing impervious area in a manner consistent with this chapter; and (C) whose activities do not qualify for the exemptions listed in §
28-302,
shall also fall under the category of major SWM permit. "Cumulative" shall include incremental and phased development (for example: a new home with greater than or equal to 5,000-square-foot of impervious will require a major SWM permit).
STORMWATER MANAGEMENT PROBLEM AREAArea where increased runoff due to flow path modifications or decreased perviousness has resulted in one or more of the following: degradation of receiving waters via increased nutrient loading, sediment loading, or destabilization of channels through increased flow velocities; increases in volume and rate of water trespass on downstream properties resulting in surface erosion or subsurface infiltration into structures; or public infrastructure degradation through increased rate and volume.
STORMWATER MANAGEMENT REPORTThe report prepared by the applicant or their representative documenting the necessary design computations and data in order to demonstrate that the maximum practicable measures have been taken to meet the requirements of this chapter. "Stormwater management report" will be designated as "SWM report" throughout this chapter.
STORMWATER MANAGEMENT SITE PLANThe plan prepared by the developer or his representative indicating how stormwater runoff will be managed at the development site in accordance with this chapter. "Stormwater management site plan" will be designated as "SWM site plan" throughout this chapter.
SUBDIVISIONAs defined in the Pennsylvania Municipalities Planning Code, Act of July 31, 1968, P.L. 805, No. 247.
SWALELandscaped depression that collects and conveys stormwater.
TRASH RACKA sturdy cage-like stormwater filtration structure that keeps large debris and trash out of stormwater systems and waterways.
USDAUnited States Department of Agriculture.
WATERS OF THIS 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 this commonwealth.
WATERSHEDRegion or area drained by a river, watercourse, or other surface water of this commonwealth.
WETLANDAreas 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.