§ 383-10. Terms defined.

As used in this Part 1, the following terms shall have the meanings indicated:

ACCELERATED EROSION

The removal of the surface of the land through the combined action of human activities and natural processes, at a rate greater than would occur because of the natural processes alone.

BEST MANAGEMENT PRACTICE (BMP)

Activities, facilities, measures or procedures used to manage stormwater quantity and quality impacts from the regulated activities listed in § 383-5, to meet state water quality requirements, to promote groundwater recharge and to otherwise meet the purposes of this Part 1.

BEST MANAGEMENT PRACTICE OPERATIONS AND MAINTENANCE PLAN

Documentation, included as part of a drainage plan, detailing the proposed BMPs, how they will be operated and maintained and who will be responsible.

BIORETENTION

Densely vegetated, depressed features that store stormwater and filter it through vegetation, mulch, planting soil, etc. Ultimately stormwater is evapotranspirated, infiltrated, or discharged. Optimal bioretention areas mimic natural forest ecosystems in terms of species diversity, density, distribution, use of native plants, etc.

BUFFER

A. 

STREAMSIDE BUFFER

A zone of variable width located along a stream that is vegetated and is designed to filter pollutants from runoff.

B. 

SPECIAL GEOLOGIC FEATURE BUFFER

A required isolation distance from a special geologic feature to a proposed BMP needed to reduce the risk of sinkhole formation due to stormwater management activities.

CAPTURE/REUSE

Stormwater management techniques such as cisterns and rain barrels which direct runoff into storage devices, surface or subsurface, for later reuse, such as for irrigation of gardens and other planted areas. Because this stormwater is utilized and no pollutant discharge results, water quality performance is superior to other noninfiltration BMPs.

CARBONATE BEDROCK

Rock consisting chiefly of carbonate minerals, such as limestone and dolomite; specifically a sedimentary rock composed of more than 50% by weight of carbonate minerals that underlies soil or other unconsolidated, superficial material.

CISTERN

An underground reservoir or tank for storing rainwater.

CLOSED DEPRESSION

A distinctive bowl-shaped depression in the land surface. It is characterized by internal drainage, varying magnitude, and an unbroken ground surface.

CONSERVATION DISTRICT

The Lehigh or Northampton County Conservation District, as applicable.

CONSTRUCTED WETLANDS

Constructed wetlands are similar to wet ponds (see below) and consist of a basin which provides for necessary stormwater storage as well as a permanent pool or water level, planted with wetland vegetation. To be successful, constructed wetlands must have adequate natural hydrology (both runoff inputs as well as soils and water table which allow for maintenance of a permanent pool of water). In these cases, the permanent pool must be designed carefully, usually with shallow edge benches, so that water levels are appropriate to support carefully selected wetland vegetation.

CULVERT

A pipe, conduit or similar structure including appurtenant works which carries surface water.

DAM

An artificial barrier, together with its appurtenant works, constructed for the purpose of impounding or storing water or another fluid or semifluid or a refuse bank, fill or structure for highway, railroad or other purposes which does or may impound water or another fluid or semifluid.

DEP

The Pennsylvania Department of Environmental Protection.

DESIGN STORM

The depth and time distribution of precipitation from a storm event measured in probability of occurrence (e.g., one-hundred-year storm) and duration (e.g., twenty-four-hour) and used in computing stormwater management control systems.

DETENTION BASIN

A basin designed to retard stormwater runoff by temporarily storing the runoff and releasing it at the appropriate release rate.

DEVELOPER

A person, partnership, association, corporation or other entity, or any responsible person therein or agent thereof, that undertakes any regulated activity of this Part 1.

DEVELOPMENT SITE (SITE)

The specific tract of land for which a regulated activity is proposed.

DIFFUSED DRAINAGE

See "sheet flow."

DRAINAGE EASEMENT

A right granted by a landowner to a grantee, allowing the use of private land for stormwater management purposes.

DRAINAGE PLAN

The documentation of the proposed stormwater quantity and quality management controls to be used for a given development site, including a BMP Operations and Maintenance Plan, the contents of which are established in § 383-20.

EARTH DISTURBANCE ACTIVITY

A 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.

EROSION

The removal of soil particles by the action of water, wind, ice, or other geological agents.

EXISTING USES

Those uses actually attained in the water body on or after November 28, 1975, whether or not they are included in the water quality standards. (25 Pa. Code Chapter 93.1)

FILL

Man-made deposits of natural soils or rock products and waste materials.

FILTER STRIPS

See "vegetated buffers."

FREEBOARD

The incremental depth in a stormwater management structure, provided as a safety factor of design, above that required to convey the design runoff event.

GROUNDWATER RECHARGE

Replenishment of existing natural underground water supplies.

HARDSHIP WAIVER REQUEST

A written request for a waiver alleging that the provisions of this Part 1 inflict unnecessary hardship upon the applicant. A hardship waiver does not apply to and is not available from the water quality provisions of this Part 1 and should not be granted.

HOT SPOT LAND USES

A land use or activity that generates higher concentrations of hydrocarbons, trace metals or other toxic substances than typically found in stormwater runoff. These land uses are listed in § 383-14P.

HYDROLOGIC SOIL GROUP (HSG)

Soils are classified into four HSGs (A, B, C and D) to indicate the minimum infiltration rates, which are obtained for bare soil after prolonged wetting. The Natural Resources Conservation Service (NRCS) of the U.S. Department of Agriculture 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 permeable as the HSG varies from A to D.

IMPERVIOUS SURFACE (IMPERVIOUS COVER)

A surface which prevents the percolation of water into the ground.

INFILTRATION PRACTICE

A practice designed to direct runoff into the ground, e.g., French drain, seepage pit, seepage trench or bioretention area.

KARST

A type of topography or landscape characterized by depressions, sinkholes, limestone towers and steep-sided hills, underground drainage and caves. Karst is usually formed on carbonate rocks, such as limestones or dolomites and sometimes gypsum.

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 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.

B. 

A subdivision of land.

C. 

Development in accordance with Section 503(1.1) of the Pennsylvania Municipalities Planning Code.

LOADING RATE

The ratio of the land area draining to the system, as modified by the weighting factors in § 383-17B, compared to the base area of the infiltration system.

LOCAL RUNOFF CONVEYANCE FACILITIES

Any natural channel or man-made conveyance system which has the purpose of transporting runoff from the site to the mainstem.

LOW-IMPACT DEVELOPMENT

A development approach that promotes practices that will minimize postdevelopment runoff rates and volumes, thereby minimizing needs for artificial conveyance and storage facilities. Site design practices include preserving natural drainage features, minimizing impervious surface area, reducing the hydraulic connectivity of impervious surfaces and protecting natural depression storage.

MAINSTEM (MAIN CHANNEL)

Any stream segment or other conveyance used as a reach in the Trout/Bertsch Creeks 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.

MARYLAND STORMWATER DESIGN MANUAL

A stormwater design manual written by the Maryland Department of the Environment and the Center for Watershed Protection. As of January 2004, the manual can be obtained through the following web site: www.mde.state.md.us.

MINIMUM DISTURBANCE/MINIMUM MAINTENANCE PRACTICES (MD/MM)

Site design practices in which careful limits are placed on site clearance prior to development allowing for maximum retention of existing vegetation (woodlands and other), minimum disturbance and compaction of existing soil mantle and minimum site application of chemicals postdevelopment. Typically, MD/MM includes disturbance setback criteria from buildings as well as related site improvements such as walkways, driveways, roadways, and any other improvements. These criteria may vary by community context as well as by type of development being proposed. Additionally, MD/MM also shall include provisions (e.g., deed restrictions, conservation easements) to protect these areas from future disturbance and from application of fertilizers, pesticides, and herbicides.

MUNICIPALITY

Borough of Walnutport, Northampton County, (as applicable), Pennsylvania.

NO-HARM OPTION

The option of using a less restrictive runoff quantity control if it can be shown that adequate and safe runoff conveyance exists and that the less-restrictive control would not adversely affect health, safety and property.

NPDES

National Pollutant Discharge Elimination System.

NRCS

Natural Resources Conservation Service, U.S. Department of Agriculture. (Formerly the Soil Conservation Service.)

OIL/WATER SEPARATOR

A structural mechanism designed to remove free oil and grease (and possibly solids) from stormwater runoff.

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.

OWNER

One with an interest in and often dominion over a property.

PEAK DISCHARGE

The maximum rate of flow of stormwater runoff at a given location and time resulting from a specified storm event.

PENN STATE RUNOFF MODEL (PSRM)

The computer-based hydrologic modeling technique adapted to each watershed for the Act 167 Plans. The model was calibrated to reflect actual flow values by adjusting key model input parameters.

PERSON

An individual, partnership, public or private association or corporation, firm, trust, estate, municipality, governmental unit, public utility or any other legal entity whatsoever which is recognized by law as the subject of rights and duties.

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.

PRELIMINARY SITE INVESTIGATION

The determination of the depth to bedrock, the depth to the seasonal high water table and the soil permeability for a possible infiltration location on a site through the use of published data and on-site surveys. In carbonate bedrock areas, the location of special geologic features must also be determined along with the associated buffer distance to the possible infiltration area. See .

PUBLIC WATER SUPPLIER

A person who owns or operates a public water system.

PUBLIC WATER SYSTEM

A system which provides water to the public for human consumption which has at least 15 service connections or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. (See 25 Pa. Code Chapter 109.)

QUALIFIED GEOTECHNICAL PROFESSIONAL

A licensed professional geologist or a licensed professional engineer who has a background or expertise in geology or hydrogeology.

RATIONAL METHOD

A method of peak runoff calculation using a standardized runoff coefficient (rational 'c'), acreage of tract and rainfall intensity determined by return period and by the time necessary for the entire tract to contribute runoff. The rational method formula is stated as follows: Q = ciA, where "Q" is the calculated peak flow rate in cubic feet per second, "c" is the dimensionless runoff coefficient (see ), "i" is the rainfall intensity in inches per hour, and "A" is the area of the tract in acres.

REACH

Any of the natural or man-made runoff conveyance channels used for watershed runoff modeling purposes to connect the subareas and transport flows downstream.

RECHARGE VOLUME (REv)

The portion of the water quality volume (WQv) used to maintain groundwater recharge rates at development sites. (See § 383-14J.)

REGULATED ACTIVITIES

Actions or proposed actions which impact upon proper management of stormwater runoff and which are governed by this Part 1 as specified in § 383-5.

REGULATED EARTH DISTURBANCE ACTIVITIES

Earth disturbance activity other than agricultural plowing or tilling of one acre or more with a point source discharge to surface waters or to the municipality's storm sewer system or earth disturbance activity of five acres or more regardless of the planned runoff. This includes earth disturbance on any portion of, part or during any stage of a larger common plan of development.

RELEASE RATE

The percentage of the predevelopment peak rate of runoff for a development site to which the postdevelopment peak rate of runoff must be controlled to avoid peak flow increases throughout the watershed.

RETURN PERIOD

The average interval in years over which an event of a given magnitude can be expected to recur. For example, the twenty-five-year return period rainfall or runoff event would be expected to recur on the average once every 25 years.

ROAD MAINTENANCE

Earth 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.

RUNOFF

That part of precipitation which flows over the land.

SEDIMENT TRAPS/CATCH BASIN SUMPS

Chambers which provide storage below the outlet in a storm inlet to collect sediment, debris and associated pollutants, typically requiring periodic cleanout.

SEEPAGE PIT/SEEPAGE TRENCH

An area of excavated earth filled with loose stone or similar material and into which surface water is directed for infiltration into the ground.

SEPARATE STORM SEWER SYSTEM

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.

SHEET FLOW

Stormwater runoff flowing in a thin layer over the ground surface.

SOIL-COVER-COMPLEX METHOD

A method of runoff computation developed by NRCS which is based upon relating soil type and land use/cover to a runoff parameter called a "curve number."

SPECIAL GEOLOGIC FEATURES

Carbonate bedrock features, including but not limited to closed depressions, existing sinkholes, fracture traces, lineaments, joints, faults, caves, pinnacles and geologic contacts between carbonate and noncarbonate bedrock which may exist and must be identified on a site when stormwater management BMPs are being considered.

SPILL PREVENTION AND RESPONSE PROGRAM

A program that identifies procedures for preventing and, as needed, cleaning up potential spills and makes such procedures known and the necessary equipment available to appropriate personnel.

STATE WATER QUALITY REQUIREMENTS

As defined under state regulations, protection of designated and existing uses (see 25 Pa. Code Chapters 93 and 96), including:

A. 

Each stream segment in Pennsylvania has a designated use, such as cold water fishes or potable water supply, which is listed in Chapter 93. These uses must be protected and maintained, under state regulations.

B. 

Existing uses are those attained as of November 1975, regardless of whether they have been designated in Chapter 93. Regulated 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 involves 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 stream bank, streambed and structural integrity of the waterway, to prevent these impacts.

STORAGE INDICATION METHOD

A method of routing or moving an inflow hydrograph through a reservoir or detention structure. The method solves the mass conservation equation to determine an outflow hydrograph as it leaves the storage facility.

STORM DRAINAGE PROBLEM AREAS

Areas which lack adequate stormwater collection and/or conveyance facilities and which present a hazard to persons or property. These areas are either documented in of this Part 1 or identified by the municipality or municipal engineer.

STORM SEWER

A system of pipes or other conduits which carries intercepted surface runoff, street water and other wash waters, or drainage, but excludes domestic sewage and industrial wastes.

STORMWATER

The surface runoff generated by precipitation reaching the ground surface.

STORMWATER FILTERS

Any number of structural mechanisms such as multi-chamber catch basins, sand/peat filters, sand filters, and so forth which are installed to intercept stormwater flow and remove pollutants prior to discharge. Typically, these systems require periodic maintenance and cleanout.

STORMWATER MANAGEMENT PLAN

The plan for managing stormwater runoff adopted by Lehigh and/or Northampton County for the Trout/Bertsch Creeks Watershed as required by the Act of October 4, 1978, P.L. 864, (Act 167), as amended, and known as the "Stormwater Management Act."

STREAM

A watercourse.

SUBAREA

The smallest unit of watershed breakdown for hydrologic modeling purposes for which the runoff control criteria have been established in the stormwater management plan.

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 10 acres, not involving any new street or easement of access or any residential dwelling, shall be exempted.

SURFACE WATERS OF THE COMMONWEALTH

Any 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 water, or parts thereof, whether natural or artificial, within or on the boundaries of this commonwealth.

SWALE

A low-lying stretch of land which gathers or carries surface water runoff. See also "vegetated swale."

TECHNICAL BEST MANAGEMENT PRACTICE MANUAL AND INFILTRATION FEASIBILITY REPORT

The report written by Cahill Associates (November 2002) that addresses the feasibility of infiltration in carbonate bedrock areas in the Little Lehigh Creek Watershed. The report is available at the Lehigh Valley Planning Commission offices.

TRASH/DEBRIS COLLECTORS

Racks, screens or other similar devices installed in a storm drainage system to capture coarse pollutants (trash, leaves, etc.).

VEGETATED BUFFERS

Gently sloping areas that convey stormwater as sheet flow over a broad, densely vegetated earthen area, possibly coupled with the use of level spreading devices. Vegetated buffers should be situated on minimally disturbed soils, have low-flow velocities and extended residence times.

VEGETATED ROOFS

Vegetated systems installed on roofs that generally consist of a waterproof layer, a root-barrier, drainage layer (optional), growth media, and suitable vegetation. Vegetated roofs store and eventually evapotranspirate the collected rooftop rainfall; overflows may be provided for larger storms.

VEGETATED SWALES

A. 

Vegetated earthen channels designed to convey stormwater. These swales are not considered to be water quality BMPs.

B. 

Broad, shallow, densely vegetated, earthen channels designed to treat stormwater while slowly infiltrating, evapotranspirating, and conveying it. Swales should be gently sloping with low flow velocities to prevent erosion. Check dams may be added to enhance performance.

WATERCOURSE

Any channel of conveyance of surface water having defined bed and banks, whether natural or artificial, with perennial or intermittent flow.

WATER QUALITY INSERTS

Any number of commercially available devices that are inserted into storm inlets to capture sediment, oil, grease, metals, trash, debris, etc.

WATER QUALITY VOLUME (WQv)

The volume needed to capture and treat 90% of the average annual rainfall volume. (See § 383-14B.)

WATERSHED

The entire region or area drained by a river or other body of water, whether natural or artificial.

WET DETENTION PONDS

Basins that provide for necessary stormwater storage as well as a permanent pool of water. To be successful, wet ponds must have adequate natural hydrology (both runoff inputs as well as soils and water table which allow for maintenance of a permanent pool of water) and must be able to support a healthy aquatic community so as to avoid creation of mosquito and other health and nuisance problems.