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Abandonment, Permanent of A Well <WRD, OAR 690>: Means to remove a well from service by completely filling it in such a manner that vertical movement of water within the wellbore and within the annular space surrounding the well casing is effectively and permanently prevented.

Abandonment, Temporary of A Well <WRD, OAR 690>: Means to remove a drilling machine from a well site prior to putting the well into service or returning it to service or subsequent to completing or altering a well, or to remove a well from service with the intent of using it in the future.

Advection (OHD): Contaminant transport by the movement of groundwater at pore water velocity along streamlines of groundwater flow.

Alluvium: Unconsolidated sediments of gravel, sand, silt and clay, that were deposited in stream channels and floodplains of rivers and streams.

Altering a Well <WRD, OAR 690>: Means the deepening, reaming, casing, re-casing, perforating, re-perforating, installation of line pipe, packers, seals, and any other material change in the design or construction of a well.

Annular Space <WRD, OAR 690>: The cylindrical space between the drillhole wall and the outer well casing.

Aquifer <OHD 33-61-020>: Means a water saturated and permeable geological formation, group of formations, or part of a formation that is capable of transmitting water in sufficient quantity to supply wells or springs.

Aquifer <WRD, OAR 690-200>: Means a geological formation, group of formations, or part of a formation that contains saturated and permeable material capable of transmitting water in sufficient quantity to supply wells or springs; the terms water bearing zone or water bearing stratum are synonymous with the term aquifer.

Aquifer <DEQ, 340>: Means an underground stratum holding water which is capable of yielding a significant amount of water to a well or spring.

Aquifer Parameter: Means a characteristic of an aquifer, such as thickness, porosity or hydraulic conductivity.

Aquifer Test: Means pumping a well in a manner that will provide information regarding the hydraulic characteristics of the aquifer.

Aquitard: A geologic unit with low hydraulic conductivity, capable of transmitting water at low rates, but not at rates sufficient for production wells.

Artesian Aquifer <WRD, OAR 690>: Means an aquifer in which groundwater is under sufficient head (pressure) to rise above the level at which it was first encountered whether or not the water flows at land surface. If the water level stands above land surface, the well is a flowing artesian well.

Artificial Groundwater Recharge <WRD, OAR 690>: The intentional addition of water to a groundwater reservoir by diversion from another source.

Average Groundwater Velocity: Means the average velocity at which groundwater moves through the aquifer as a function of hydraulic gradient, hydraulic conductivity and porosity.

Background Level: In groundwater monitoring, the sampling and analysis of the water for the determination of drinking water characteristics, water quality and the concentration of contamination indicator parameters. Generally performed on wells upgradient to areas of concern.

Background Water Quality <DEQ, OAR 340>: The quality of water immediately upgradient from a current of potential source of pollution that is unaffected by the source.

Basin <WRD, OAR 690>: Any one of the major drainage areas identified by the Water Resources Commission for program planning and management purposes. Basin boundaries are identified on WRD maps.

Bedrock: A general term for the consolidated (solid) rock that underlies soils or other unconsolidated surficial material.

Beneficial Purposes <DEQ, OAR 340>: Means a purpose where the resource values of the reclaimed waters, such as but not limited to its nutrients or moisture value, are utilized for enhanced productivity or water conservation by the user.

Beneficial Use <DEQ, OAR 340 and WRD, OAR 690>: The reasonably efficient use of water without waste for a purpose consistent with the laws, rules, and best interests of the people of the state.

Best Management Practice (BMPs): Operational or maintenance measures that are determined to be the most effective, practical means of preventing or reducing pollution inputs from nonpoint or point sources of contamination.

Biochemical or Biological Oxygen Demand (BOD): A measure of the amount of oxygen consumed in the biological processes that break down organic matter in water. The greater the BOD, the greater the degree of pollution.

Calculated Fixed Radius: Means a technique to delineate a wellhead protection area, based on the determination of the volume of the aquifer needed to supply groundwater to a well over a given length of time.

Carcinogen <DEQ, OAR 340>: A compound which the EPA has classified as Group A or Group B under the carcinogenic classification procedures described in 51 Fed. Reg. 33992.

Casing <WRD, OAR 690>: Means the outer tubing, pipe, or conduit, welded or screw coupled, and installed in the borehole during or after drilling to support the sides of the wall and prevent caving, to shut off water, gas, or contaminated fluids from entering the hole, and to prevent waste of groundwater. Casing does not include slotted or perforated pipe, well screens, or liner pipe.

Casing Seal <WRD, OAR 690>: Means the watertight seal established in the wellbore between the well casing and the drillhole wall to prevent the inflow and movement of surface water or shallow groundwater in the well annulus, or to prevent the outflow or movement of water under artesian or hydrostatic pressures.

Cement-Bentonite Grout (Slurry): A mixture of cement, bentonite, and water generally used as an annular sealant.

Chemical Analysis (Groundwater): The determination of the concentration of dissolved inorganic and organic constituents, the values of chemical state parameters (e.g., pH, Eh, and temperature), and the physical properties (e.g., turbidity). The minimum chemical properties that are usually determined are: T, pH, hardness, specific conductance, dissolved solids, chloride, bicarbonate, iron, fluoride, and nitrate.

Cleanup <DEQ, OAR 340>: Includes, but is not limited to, the containment, collection, removal, treatment or disposal of oil or hazardous material; site restoration; and any investigations, monitoring, surveys, testing, and other information gathering required or conducted by DEQ.

Coliform - Fecal Coliform: Microorganisms found in the intestinal tract of humans and animals. Their presence in water indicates fecal pollution and potentially dangerous bacterial contamination by disease-causing microorganisms.

Compliance Point <DEQ, OAR 340>: The point or points where groundwater quality parameters must be at or below the permit specific concentration limits or the concentration limit variance.

Community Well <WRD, OAR 690>: Means a well, whether publicly or privately owned, which serves or is intended to serve more than 15 connections for the purpose of supplying water for drinking, culinary, or household uses.

Community Water System <OHD, OAR 333>: Public supply which serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents. Community public supply wells may be owned by a municipality or community, a water district, a corporation, a private individual or by a local, state, or federal government agency.

Concentration Limit <DEQ, OAR 340>: The maximum acceptable concentration of a contaminant allowed in groundwater at a DEQ specified compliance point.

Conductivity (Chemical Analysis): The ability of water to transmit an electrical current. Conductivity is directly related to the abundance of ions in the water.

Cone of Depression: The depression of heads around a pumping well caused by the withdrawal of water.

Confined Animal Feeding or Holding Area <WRD, OAR 690>: The concentrated confined feeding or holding of animals or poultry, including but not limited to horse, cattle, sheep, swine feeding, dairy confinement areas, slaughterhouse, or shipping terminal holding pens where the animal waste is allowed to build up on the ground, and where the concentration of animals has destroyed the vegetative cover. Areas where animals and animal waste is confined in buildings are exempt.

Confining Formation <WRD, OAR 690>: Means the impermeable stratum immediately overlying an artesian (confined) well. A layer of rock having very low hydraulic conductivity that hampers the movement of water into and out of an aquifer.

Confirmed or Confirmation <DEQ, OAR 340>: Means that a second laboratory quantitatively detects the presence of the contaminant or substance of concern in groundwater by an established analytical technique.

Consolidated Formation <WRD, OAR 690>: Means materials that have become firm through natural rock forming processes. It includes material such as basalt, sandstone, hard claystone, conglomerate, and granite.

Contaminant <OHD, OAR 333>: Any physical, chemical, biological, or radiological substance or matter in water which may render the water nonpotable.

Contaminant (Groundwater) <DEQ, HB 3515 and WRD, OAR 690>: Any chemical, ion, radionuclide, synthetic organic compound, microorganism, waste, or other substance that does not occur naturally in groundwater or that occurs naturally but at a lower concentration. (The introduction into the natural groundwater environment of any chemical, organic material, live organism(s), wastes, radioactive, or other material that lessens the quality of the water, renders it unfit, and/or affects the intended use of the water.)

Contamination <WRD, OAR 690>: An impairment of water quality by chemicals, radionuclides, biologic organisms, or other extraneous matter whether or not it affects the potential or intended beneficial use of water.

Contaminant Plume: The two-dimensional (map view) or three-dimensional form of contaminated groundwater in an aquifer. The shape of the plume is controlled by groundwater flow and by the transportation processes involved.

Contingency Plan <DEQ, OAR 340>: A document setting out an organized, planned, and coordinated course of action to be followed in case of a fire, explosion, or release of hazardous waste or hazardous waste constituents which could threaten human health or the environment and is prepared pursuant to 40 CFR part 264.

Corrective Action <DEQ, OAR 340>: Remedial action taken to protect the present or future public health, safety, welfare, or the environment from a release of a regulated substance.

Critical Groundwater Area Boundary <WRD, OAR 690>: A line established in a critical groundwater area order on a map that surrounds an area in which one or more of the statutory criteria for critical area declaration are met and which is located either:

• Physically by coincidence with natural features such as groundwater reservoir boundaries, hydrologic barriers, or recharge or discharge boundaries, or
  
• Administratively by surrounding an affected area when that area does not coincide with an area bounded by natural features.
  

Datum Plane: An arbitrary elevation to which others are compared, e.g., sea level.

Decommission <DEQ, OAR 340>: To remove from operation an underground storage tank, including temporary or permanent removal from operation, abandonment in place, or removal from the ground.

Delineation: Means the determination of the extent, orientation, and boundaries of a wellhead protection area using factors such as geology, aquifer characteristics, well pumping rates, and time of travel

Detect, Detectable, Detection or Detected <DEQ, OAR 340>: To measure a contaminant by an established analytical technique in a laboratory using established quality assurance and quality control procedures such as 40 CFR 136.

Discharge: Means the volume rate of loss of groundwater from the aquifer through wells, springs, or to surface water.

Dispersion: Spreading out of a contaminant in groundwater by diffusion and mixing.

Disposal System <DEQ, ORS 468>: A system for disposing of wastes, either by surface or underground methods and includes municipal sewerage systems, domestic sewerage systems, treatment works, disposal wells, and other systems.

Downgradient Detection Monitoring Point <DEQ, OAR 340>: The point or points at which groundwater quality is monitored to immediately determine whether a pollutant has been discharged to groundwater. The detection monitoring point is not necessarily the same as the compliance point.

Domestic Well <WRD, OAR 690>: A well used to serve no more than three residences for the purpose of supplying water for drinking, culinary, or household uses, and which is not used as a public water supply. (A water well used exclusively to supply the household needs of the owner/lessee and family. Uses may include drinking, cooking, washing, sanitary purposes, lawn and garden watering, and caring for pets.)

Downgradient Well: A groundwater monitoring well which has been constructed at a point of lesser static head (downgradient) of an area of environmental concern for the purpose of detecting the migration of contaminants from this area.

Drawdown: Means the difference, measured vertically, between the static water level in the well and the water level during pumping.

Dump: A land site where solid waste is disposed of in a manner that harms the environment. Dumping is the indiscriminate disposal of solid waste.

Effective Porosity: Means the ratio of the volume of interconnected voids (openings) in a geological formation to the overall volume of the material.

Effluent: Sewage water, or other liquid, raw or partly treated flowing into a reservoir, basin, or treatment plant.

Element: Means one of seven components considered by the U.S. Environmental Protection Agency as the minimum required components in any state wellhead protection program:

• Specification of duties;
• Delineation of the wellhead protection area;
• Inventory of potential contaminant sources.
• Specification of management approaches;
• Development of contingency plans;
• Addressing new (future) wells and springs; and
• Ensuring public participation.
  

Emergency: Means a condition resulting from an unusual calamity such as a flood storm, earthquake, drought, civil disorder, volcanic eruption, an accidental spill of hazardous material, or other occurrence which disrupts water service at a public water system or endangers the quality of water produced by a public water system.

Environment <DEQ, OAR 340>: The air, water and land, and the interrelationship which exists among and between water, air, and land and all living organisms.

Equipotential Line: A line on a map or cross section along which total heads are the same.

Federal Standard <SDWA, DEQ, HB 3515>: A maximum contaminant level, a national primary drinking water regulation, or an interim drinking water regulation adopted by the EPA under the Safe Drinking Water Act.

Flow Line: The idealized path followed by particles of water.

Flow Net: The grid pattern formed by a network of flow lines and equipotential lines.

Formation: A mappable geologic unit or units with definite lithologic characteristics.

Future Groundwater Sources: Means wells and/or springs that may be required by the public water system in the future to meet the needs of the system.

Generator <DEQ, OAR 340>: The person who, by virtue of ownership, management or control, is responsible for causing or allowing to be caused the creation of hazardous waste.

Governmental Entity: Means any local, state, Indian tribe, or federal organization or agency which may own or manage lands or activities within a Wellhead Protection Area.

Gravel Pack (Filter Pack): The term applied to the inert, usually siliceous, material placed in and around the annular space between the borehole and a perforated casing or well screen to prevent the movement of finer material into the well.

Groundwater <WRD, ORS 537>: Any water, except capillary moisture, beneath the land surface or beneath the bed of any stream, lake, reservoir, or other body of surface water within the boundaries of this state, whatever may be the geological formation or structure in which such water stands, flows, percolates, or otherwise moves.

Groundwater <DEQ, OAR 340>: Water that occurs beneath the land surface in the zone(s) of saturation.

Groundwater Management Area <DEQ, HB 3515>: An area in which contaminants in the groundwater have exceeded the levels established under this act (Section 24) and the affected area is subject to a declaration (Section 36).

Groundwater Monitoring Program (Detection Monitoring): A monitoring well system capable of yielding groundwater samples for analysis. Upgradient well(s) are installed to obtain representative samples of the background (unaffected) groundwater. Downgradient wells are generally placed immediately adjacent to the area of concern to detect any constituents migrating into the groundwater environment.

Groundwater Velocity: The rate of movement of groundwater through an aquifer. Groundwater velocity may vary considerably within a given aquifer. The average groundwater velocity in the aquifer is defined as:

v = (hydraulic conductivity ´ gradient)/porosity

Half-Life (T 1/2): Time required to reduce the initial concentration of the component by one half. The component's concentration will be reduced to 50 percent after one half-life, 25 percent after two half-lifes, and 12.5 percent after three half-lifes, etc.

Hazardous Material <SFM, OAR 437 and DEQ, OAR 453>: Any substance known to present a physical or health hazard to people under normal conditions of use and/or during emergency use. Any chemical or material which is required to have a Material Safety Data Sheet under OAR 437 and ORS 453, or designated as such by the SFM.

Hazardous Substance <DEQ, OAR 340>: Any substance intended for use which may also be identified as hazardous.

Hazardous Waste <DEQ, ORS 340/466/469>: Means a substance defined by ORS Chapter 466.005 and or ORS 469.300. Storage or collection, the containment of hazardous wastes either on a temporary basis or for a period of years, in a manner that does not constitute disposal of the hazardous waste.

Hazardous Waste Disposal Site <WRD, OAR 690>: Refers to a geographical site in which or upon which hazardous waste is disposed.

Hazardous Waste Storage Site <WRD, OAR 690>: The geographical area site upon which hazardous waste is stored.

Hazardous Waste Generators <EPA>: Generators of greater than 1,000 kg/month of hazardous waste (large quantity generators); generators between 100 and 1,000 kg/month hazardous waste (small quantity generators); and generators of less than 100 kg/month of hazardous waste (conditionally exempt small quantity generators or very small quantity generators).

Head: The energy possessed by the water mass at a given point, related to the height above a datum plane that water will rise in a well drilled to that point. In a groundwater system, it is composed of elevation head and pressure head.

Health Hazard <WRD, OAR 690>: A condition where there are sufficient concentrations of biological, chemical, or physical contaminants in the water that are likely to cause human illness, disorders, or disability. This includes naturally occurring substances, pathogenic viruses, bacteria, parasites, toxic chemicals, and radioactive isotopes. Sufficient concentrations of a contaminant include but are not limited to contaminant levels set by the DEQ and ODH.

Health Threat <WRD, OAR 690>: A condition where there is an impending health hazard. The threat may be posed by, but not limited to: a conduit for contamination, or a well affecting migration of a contaminate plume, or the use of contaminated water. A well in which the well construction is not verified by a water well report or a geophysical techniques may be considered a conduit for contamination in certain circumstances. Those circumstances include, but are not limited to: an unused and neglected well, a well that is permanently out of service, or a well for which no surface seal was required. A well in which the casing seal, sanitary seal, or watertight cap has failed, or was in adequately installed may be considered a conduit for contamination.

Hydraulic Conductivity (K): A parameter related to the ability of the aquifer to transmit water. Formally defined as the rate at which a unit volume of water at the prevailing viscosity will flow through a unit cross section of the aquifer under a unit hydraulic gradient in a unit of time.

Hydraulic Connection <WRD, OAR 690>: Water that can move between a surface water source and an adjacent aquifer.

Hydraulic Gradient: Change in head per unit of distance measured in the direction of the steepest change.

Hydraulic Head: Means the energy possessed by the water mass at a given point, related to the height above the datum plane that water resides in a well drilled to that point. In a groundwater system, the hydraulic head is composed of elevation head and pressure head.

Hydrolysis: The reaction of an organic molecule with water or a component of water. Important in that hydrolysis may affect the molecule's solubility or susceptibility to biodegradation.

Hydrogeologic Boundary: Means physical features that bound and control direction of groundwater flow in a groundwater system. Boundaries may be in the form of a constant head, e.g., streams, or represent barriers to flow, e.g., groundwater divides and impermeable geologic barriers.

Hydrogeologic Mapping: Means characterizing hydrogeologic features (e.g. hydrogeologic units, hydrogeologic boundaries, etc.) within an area and determining their location, areal extent and relationship to one another.

Hydrogeologic Unit: Means a geologic formation, group of formations, or part of a formation that has consistent and definable hydraulic properties.

Interfering Wells: Means wells, that because of their proximity and pumping characteristics, and as a result of the aquifer's hydraulic properties, produce drawdown cones that overlap during simultaneous pumping. The result is a lowering of the pumping level in each well below what it would be if that well were pumping by itself.

Ion: A chemical species that carries a charge. Ions may consist of one or more elements and may be either positive (cations) or negative (anions).

Impermeable <WRD, OAR 690>: Means a material that limits the passage of water.

Inactive Well: A well is considered to be inactive if it is not presently operating but is maintained in such a manner that it can be placed back into operation with a minimum of effort.

Indicator Parameters: Specific biological, chemical and/or physical properties analyzed for the determination of groundwater quality (e.g., coliform bacteria, pH, total organic halogens, etc.).

Industrial Wastewater <DEQ, OAR 340>: means any liquid, gaseous, radioactive, or solid waste substance, or a combination thereof resulting from any process of industry, manufacturing, trade or business, or from the development or recovery of any natural resources.

Industrial Well: A well used to supply water for plants that manufacture, process, or fabricate a product. The water may or may not be used to cool machinery, to provide sanitary facilities for employees, to air condition the plant, and to water grounds at the plant.

Infiltration: The downward movement of water of surface origin into the soil or rock formations.

Injection Well: A well into which fluids are injected for the purpose of waste disposal or to recharge Aquifer pressure.

Irrigation Well: A well used for irrigating cultivated plants, for watering stock, farming, and similar agriculture activities.

Joint: A fracture in a rock along which no relative movement has taken place (e.g., columnar joints in basalts).

Landfill <DEQ, OAR 340>: A facility for the disposal of solid waste involving the placement of solid waste on or beneath the land surface.

Leachate <EPA>: Water that has percolated through solid waste or another medium and has extracted materials by dissolving them or carrying them in suspension. If leachate contaminates groundwater, it is difficult and expensive to clean up, and it may take decades for the contaminants to be flushed naturally.

Leachate <DEQ, OAR 340>: Liquid that has come into direct contact with solid waste and contains dissolved and/or suspended contaminants as a result of such contact.

Leakage <WRD, OAR 690>: Means leakage of surface and/or subsurface water around the well casing or within the well bore from one aquifer to another.

Local Emergency Planning Committee (LEPC)<OEM>: Part of the local emergency planning districts, focal point for SARA Title III community activities.

Local Government <DLCD, ORS 190>: A city, county, special district, or other public corporation, commission, authority or entity organized under state statute or city or county charter.

Material Safety Data Sheet <SFM, OAR 837>: Written or printed material concerning a hazardous chemical which is prepared pursuant to rules OAR 437 of the Oregon OSHA.

Maximum Contaminant Level (MCL) <SDWA/ODH OAR 333>: Refers to the maximum possible level of a contaminant in water at which no known or anticipated adverse effect on health of persons would occur and which allows an adequate margin of safety. Defined as the maximum allowable level of a contaminant in water, which will not cause a public health risk when the water is delivered to the users of a public water system, except in the case of turbidity where the maximum allowable level is measured at the point of entry to the distribution system. Contaminants occurring in the water resulting from circumstances controlled by the water user except those resulting from corrosion of piping and plumbing caused by water quality are excluded from this definition.

Maximum Measurable Level (MML)<DEQ, HB3515>: The maximum allowable concentration of a contaminant or substance of concern that is established by the EQC in accord with these rules. Adopted MMLs are to be used by DEQ to initiate the process of designating groundwater management areas within the state of Oregon were necessary to preserve groundwater quality.

Mineralized Water <WRD, OAR 690>: Means any naturally occurring groundwater containing an amount of dissolved chemicals limiting the beneficial uses to which the water may be applied.

Mitigation <WRD, OAR 690>: Avoiding or minimizing losses of resource values by implementing structural or operational measures within the project area.

Modified Spill Prevention Control and Countermeasure (SPCC) Plan <DEQ, OAR 340>: The plan to prevent the spill of oil from a non-transportation related facility that has been modified to include those hazardous substances and hazardous wastes handled at the facility.

Monitoring Well <WRD, OAR 690>: Any hole, however constructed, in naturally existing or artificially emplaced earth materials through which groundwater is accessed to make judgments, determinations, observations, or measurements of water quality.

Municipal or Quasi-Municipal Well <WRD, OAR 690>: A well owned by a municipality or nonprofit corporation that may be used as a community or public water supply.

Municipality <DEQ, OAR 340>: Any county, city, special service district, other governmental entity having authority to dispose of sewage, industrial waste, or other wastes, any indian tribe or authorized tribal organization, or any combination of two or more of the foregoing.

Natural Water Quality <DEQ, OAR 340>: Water quality that would exist as a result of conditions unaffected by human caused pollution.

New Groundwater Sources: Means additional or modified wells and/or springs owned by the Public Water System.

Non-Aqueous Phase Liquid (NAPL): A liquid that is immiscible with water. May be more or less dense than water.

Noncommunity Public Supply Well <EPA>: A public supply water well which serves either fewer than 15 service connections or fewer than 25 year-round residents or no year-round residents. Examples of the former case are small public water supplies for mobile home parks, subdivisions, etc., which fall below the 15 connections/25 persons criteria for community water supplies. The latter case includes water supplies which serve no year-round residents, such as lunges, motels, camps, office buildings, restaurants, rest stops, schools, etc.

Noncommunity Public Water Supply Well (NCWS) <OHD>: Those systems providing water to at least 10 people, 60 days per year. May be transient or nontransient.

Nonpoint Source <DEQ, OAR 340>: Diffuse or unconfined sources of pollution where contaminants can enter into or be conveyed by the movement of water into public water.

Nontransient Noncommunity Water System (NTNCWS)<OHD/EPA>: Means a public water system that is not a Community Water System and that regularly serves 25 or more of the same people for more than six months out of the year, e.g., schools, factories, and small residential systems.

Open Interval: Means in a cased well, the sum of the length(s) of the screened or perforated zone(s) and in an uncased (open-hole) well, the sum of the thickness(es) of the water-bearing zones or, if permeable, 10 percent of the length of the open hole.

Other Hole <WRD, OAR 690>: A hole other than a water well or monitoring well, however constructed, in naturally occurring or artificially emplaced earth materials through which groundwater can become contaminated.

Perched Groundwater <WRD, OAR 690>: Means groundwater held above the regional or main water table by a less permeable underlying earth or rock material.

Permeability <WRD, OAR 690>: The ability of material to transmit fluid, usually described in units of feet per day or gallons per day per square foot of cross-section area.

pH: A mathematical expression of the hydrogen-ion activity. A measure of the acidity (pH < 7.0) or alkalinity (pH > 7.0) of a material.

Pesticide <SFM, OAR 837, DEQ, OAR 340, and ODA, ORS 634>: Means any substance or mixture of substances (including fungicides, herbicides, insecticides, nematocides, and rodenticides), intended for preventing, destroying, repelling, or mitigating any pest and any substance or mixture of substances indented for use as a plant regulator, defoliant, or desiccant.

Plan: Means a specific local Wellhead Protection Plan.

Point Source <DEQ, OAR 340>: Any confined or discrete source of pollution where contaminants can enter into or be conveyed by the movement of water into the public waters.

Pollution (Water) <DEQ, ORS 340/468>: Alteration of the physical, chemical, or biologic properties of any waters of the state, including change in temperatures, taste, color, turbidity, silt or odor of the waters, or such discharge of any liquid, gaseous, solid, radioactive or other substance into waters of the state, which will or tends to, either by itself or in connection with any other substance, create a public nuisance or which will or tends to render such waters harmful, detrimental or injurious to public health, safety or welfare, or to domestic, commercial, industrial, agricultural, recreational or other legitimate beneficial uses or to livestock, wildlife, fish or other aquatic life, or the habitat thereof.

Porosity <WRD, OAR 690>: Means the ratio of the volume of voids (openings) in a geological formation being drilled to the overall volume of the material without regard to size, shape, interconnection, or arrangement of openings.

Porous Media Assumption: Means the assumption that groundwater moves in the aquifer as of the aquifer were granular in character; i.e., moves directly down-gradient, and the velocity of the groundwater can be described by Darcy's Law.

Potable Water <WRD, OAR 690>: Water which is sufficiently free from biological, chemical, physical, or radiological impurities so that users thereof will not be exposed to or threatened with exposure to disease or harmful physiological effects. (Water whose bacteriological, physical, and chemical properties make it suitable for human consumption.)

Potable Water Supply System <DEQ, OAR 340>: A water supply system used to provide water for human consumption.

Potential Contaminant Source: Means any activity which has the potential to release contaminants to the groundwater.

Potential Contaminant Source Inventory: Means the determination of the location within the wellhead protection area of activities known to use or produce materials that can contaminate groundwater.

Potentiometric Surface: Means a surface that denotes the variation of hydraulic head in the given aquifer across an area.

Potentiometric Surface (Piezometric Surface) <WRD, ORS 690>: The level to which water will rise in tightly cased wells.

Protect Public Health and the Environment <DEQ, OAR 340>: To keep humans and the environment from unreasonable adverse risk, effect or harm, excluding economic concerns.

Provisional Delineation: Means approximating the wellhead protection area for a well by using the wellhead protection area from another well in the same hydrogeologic setting or by using generalized values for the aquifer characteristics to generate an approximate wellhead protection area of the well. Used only for the purpose of evaluating potential siting of new or future groundwater sources. Not an acceptable way to formally delineate a wellhead protection area.

Public Health Hazard <WRD, OAR 690>: A condition whereby there are sufficient types and amounts of biological, chemical, or physical, including radiological agents relating to water which are likely to cause human illness, disorders, or disability. These include, but are not limited to pathogenic viruses, bacteria, parasites, toxic chemicals, and radioactive isotopes.

Public Health Hazard <OHD, OAR 333>: Defines as a condition, device or practice which is conductive to the introduction of waterborne disease organisms or harmful chemical, physical or radioactive substances into a public water system, and which presents an unreasonable risk to health.

Public Water System: Means a system for the provision to the public of piped water for human consumption, if such system has more than 3 service connections or supplies water to a public or commercial establishment which operates a total of at least 60 days per year, and which is used by 10 or more individuals per day or is a facility licensed by the Division. A public water system is either a "Community water system", a "Transient Non-Community water system", a "Non-Transient Non-Community water system" or a "State regulated water system".

Pump Test <WRD, OAR 690>: Means the procedure involving pumping water for a specified period of time to determine the yield characteristics of an aquifer.

Recharge: Means the process by which water is added to a zone of saturation, usually by downward infiltration from the surface.

Recharge Area: Means a land area in which water percolates to the zone of saturation through infiltration from the surface.

Reclaimed Water <DEQ, OAR 340>: Means treated effluent from a sewage treatment system which, as a result of treatment, is suitable for direct beneficial purpose or a controlled use that could not otherwise occur.

Recovery: Means the rise in water level in a well from the pumping level towards the original static water level after pumping has been discontinued.

Redox Potential (Eh): An indication of the environment's tendency to cause oxidizing-reducing reactions. These reactions are important in controlling solubilities of minerals and transport of contaminants. Eh is also an important control in biodegradation processes that reduce contaminant concentrations.

Registered Well: An inventoried well that has been assigned an identification number by state agencies and whose records are available.

Release <DEQ, OAR 340>: The discharge, deposit, injection, dumping, spilling, emitting, leaking, or placing of a regulated substance from an underground storage tank into the air or into or on land or the waters of the State, other than authorized by a permit issued under State or Federal law.

Remedial Action <DEQ, ORS 466>: Those actions consistent with a permanent remedial action taken instead of or in addition to, removal actions in the event of a release or threatened release of a hazardous substance into the environment, to prevent or minimize the release of a hazardous substance so that they does not migrate to cause substantial danger to present or future public health, safety, welfare, or the environment.

Reportable Quantity <DEQ, OAR 340>: An amount of oil or hazardous material which if spilled, released, or threatens to spill or release, in quantities equal to or greater than those specified in OAR 340 which would trigger CERCLA and SARA Title III emergency release reporting requirements.

Responsible Management Authority: Means the Public Water System whose water supply is being protected and any governmental entity with management, rule or ordinance making authority to implement wellhead protection management strategies within a Wellhead Protection Area. Responsible Management Authorities are responsible for implementation of the Wellhead Protection Plan; includes cities, counties, special districts, Indian tribes, state/federal government entities as well as Public Water Systems.

Retardation: The movement of a contaminant at a velocity less than that of the water in the aquifer as a result of chemical or biological reactions.

Rock: Any naturally formed, consolidated or unconsolidated material (but not soil) consisting of two or more minerals.

Sanitary Survey <EPA>: An on-site review of the water source, facilities, equipment, operation, and maintenance of a public water system for the purpose of evaluating the adequacy of such source, facilities, equipment, operation, and maintenance for production and distributing safe drinking water.

Saturated Zone: The subsurface zone in which all opening are full of water.

Screened Interval: A depth interval in a cased well that is slotted or perforated and serves as the intake portion for water from the aquifer.

Sewage <DEQ, OAR 340>: Means water-carried human wastes, including kitchen, bath, and laundry waste from residences, buildings, industrial and commercial establishments, or other places, together with such groundwater infiltration, surface waters, or industrial wastewater as may be present.

Sewage Treatment System <DEQ, OAR 340>: Any facility or equipment used to alter the quality of sewage by physical, chemical or biological means or a combination thereof such that the tendency of said wastewater to degradation in water quality or other environmental conditions is reduced.

Significant Adverse Impact <WRD, OAR 690>: Any impact resulting in degradation of an important resource, that is unacceptable because it cannot be mitigated or because of unacceptable conflicts in management of use of the impacted resource.

Signatory: Means any Responsible Management Authority in the Wellhead Protection Area who signs the Wellhead Protection Plan. Signing the Plan indicates the Responsible Management Authority will implement the actions outlined for their jurisdiction in the Plan.

Significant Hazard to Public Health <SDWA>: Any level of contaminant which causes or may cause the aquifer to exceed any maximum contaminant level set forth in any promulgated Nation Primary Drinking Water Standard at any point where the water may be used for drinking purposes or which may otherwise adversely affect the health of persons or which may require a public water system to install additional treatment to prevent such adverse effect.

Stakeholder(s): Means person(s) and/or governmental entity(ies) who could or will be affected by activities or requirements that may be required within a local wellhead protection area.

State Emergency Response Commission (SERC)<OEM>: Appointed by each state to ensure that SARA Title III emergency planning and implementation is developed.

Soil: The layer of material at the land surface that supports plant growth.

Solubility: The mass of a specific material, either solid, liquid or gas, that can be dissolved under specific conditions. Usually expressed as milligrams per liter.

Specific Capacity: The yield of a well per unit of drawdown.

Specific Retention: The ratio of the volume of water retained in a rock after gravity drainage to the volume of the rock.

Specific Yield: The ratio of the volume of water that will drain under the influence of gravity to the volume of saturated rock.

Spill or Release <DEQ, ORS 454/459/466/468/469>: The discharge, deposit, injection, dumping, spilling, emitting, releasing, leaking, or placing of any oil or hazardous material in the air or into, or on any land or waters of the state, except as authorized by a permit.

Sorption: The attaching of a component to the surface of a solid - either a mineral or organic particles.

Static Water Level <WRD, OAR 690>: The stabilized level or elevation of the water surface in a well which is not being pumped.

Storage Coefficient: The volume of water released (or gained) from storage in the aquifer per unit area of aquifer per unit change in hydraulic head.

Stratification: Large scale layered structure in rocks, e.g., sedimentary rocks or lava flows.

Substance of Concern <DEQ, OAR 340>: A contaminant confirmed to exist in groundwater in Oregon as a result of actual or suspected nonpoint source activities.

Sump <WRD, OAR 690>: A hole dug to a depth of 10 feet or less with a diameter greater then 10 feet in which water is encountered.

Team: Means the local Wellhead Protection Team, which includes representatives from the Responsible Management Authorities and various interests and stateholders potentially affected by the Wellhead Protection Plan.

Threat To Drinking Water <DEQ, ORS 454>: The existence in any area of any three of the following conditions:

• More than 50 percent of the affected area consists of rapidly draining soils;
  
• The groundwater underlying the affected area is used or can be used for drinking water;
  
• More than 50 percent of the sewage in the affected area is discharged into cesspools, septic tanks or seepage pits and the sewage contains biological, chemical, physical or radiological agents that can make water unfit for human consumption; and
  
• Analysis of samples of groundwater from wells producing water that may be used for human consumption in the affected area contains levels of one or more biological, chemical, physical or radiological contaminants which, if allowed to increase at historical rates, would produce a risk to human health as determined by the local health officer. Such contaminant levels must be in excess of 50 percent of the maximum allowable limits set in accordance with the federal Safe Drinking Water Act.
  

Time-of-Travel (TOT): Means the amount of time it takes groundwater to flow to a given well. The criterion that effectively determines the radius in the calculated fixed radius method and the up-gradient distance to be used for the analytical and numerical models during delineation of the wellhead protection area.

Transient Noncommunity Water System <OHD>: Noncommunity systems that serve a transient population, e.g., motels, restaurants, and campgrounds.

Transmissivity: The rate at which water of the prevailing kinetic viscosity is transmitted through a unit width of an aquifer under a unit hydraulic gradient. It equals the hydraulic conductivity multiplied by the aquifer thickness.

Treatment Works <DEQ, OAR 340>: Any facility for the purpose of treating, neutralizing or stabilizing sewage of industrial wastes of a liquid nature, including treatment or disposal plants, the necessary intercepting, outfall and outlet sewers, pumping stations integral to such plants or sewers, equipment and furnishings, thereof, and their appurtenances.

Turbidity: A cloudy condition in water due to suspended silt or organic matter.

Unconfined Aquifer (Water Table) <WRD, OAR 690): An aquifer in which the water table is the upper boundary. There is no confining layer between the aquifer and the surface and the pressure at the water table is atmospheric. Water level in an unconfined aquifer may move up and down in response to local recharge or discharge.

Unconsolidated Formation <WRD, OAR 690>: Means naturally occurring, loosely cemented, or poorly indurated materials including clay, sand, silt, and gravel.

Underground Storage Tank <DEQ, OAR 340>: Any one or a combination of tanks and underground pipes connected to the tank, used to contain an accumulation of a regulated substance, and the volume of which, including the volume of the underground pipes connected to the tank, is 10 percent or more beneath the surface of the ground (e.g., excludes farm and residential tanks, heating oil tanks, septic tanks).

Unsaturated Zone: The subsurface zone, usually starting at the land surface, that contains both water and air.

Upgradient Well: One or more wells which are placed hydraulically upgradient of an area of concern and are capable of yielding groundwater samples that are representative of the regional conditions andare not influenced by the monitored area.

Violation <WRD, OAR 690>: An infraction of any statute, rule, standard, order, license, compliance schedule, or any part thereof, and includes both acts and omissions.

Volatile: The tendency to transform from the liquid or solid state to the gaseous state.

Wastes <DEQ, ORS 468>: Sewage, industrial wastes, and all other liquid, gaseous, solid, radioactive, or other substances which will or may because pollution or tend to cause pollution of any waters of the state.

Wasteful Use <WRD, OAR 690>: Any artificial discharge or withdrawal of groundwater from an aquifer that is not put to a beneficial use, including leakage from one aquifer to another within the well bore.

Water (of the state) <DEQ, OAR 340/468 and WRD OAR 690>: Includes lakes, bays, ponds, impounding reservoirs, springs, wells, rivers, streams, creeks, estuaries, marshes, inlets, canals, the Pacific Ocean within the territorial limits of the State of Oregon and all other bodies of surface or underground waters, natural or artificial, inland, or coastal, fresh or salt, public or private (except those private waters which do not combine or effect a junction with natural surface or underground waters), which are wholly or partially within or bordering the state or within its jurisdiction.

Water-Bearing Zone: Means that part or parts of the aquifer encountered during drilling that yield(s) water to a well.

Water Table: The upper surface of an unconfined water body, the surface of which is at atmospheric pressure and fluctuates seasonally. The water table is defined by the levels at which water stands in wells that penetrate the water body.

Well <WRD, OAR 690 and OHD, OAR 333>: Any artificial opening or altered natural opening, however made, by which groundwater is sought or through which groundwater flows under natural

pressure, or is artificially withdrawn or injected. This definition shall not include a natural spring, or wells drilled for the purpose of exploration or production of oil and gas. Prospecting or exploring for geothermal resources as defined in ORS 522 or production of geothermal resources derived from a depth greater than 2,000 feet or greater than 250 degrees Fahrenheit as defined in ORS 522 is regulated by DOGAMI.

Wellhead Protection: Means implementing strategies within a wellhead protection area to minimize the potential impact of contaminant sources on the quality of groundwater used a drinking water source by a Public Water System.

Wellhead Protection Area: Means the surface and subsurface area surrounding a water well, spring or wellfield, supplying a public water system, through which contaminants are reasonably likely to

move toward and reach that water well, spring, or wellfield.

Wellhead Protection Plan: Refers to a Department certified plan which identifies the actions to be taken at the local level to protect a specific defined Wellhead Protection Area. The Plan is developed by the local Responsible Management Authority(ies) and/or team and includes a written description of each element, public participation efforts, and an implementation schedule.

Zone of Contribution (ZOC)<OHD>: Area surrounding a pumping well that includes all regions which supply groundwater to the well. In other words, groundwater within the ZOC boundaries will ultimately move to the well.

Zone of Influence (ZOI)<OHD>: The area surrounding a pumping well where the hydraulic head has been modified by the pumping.

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