The online RCAP Resources Library has a variety of resources that are useful to small, rural drinking water and wastewater systems.


Abandoned well: A well that has been permanently disconnected and filled. Most states have regulations or guidelines for abandoned wells to ensure that contamination cannot move from the surface in the aquifer.

Accounts payable: Money the system owes for the normal operation of business, including utility (electricity, telephone, etc.) bills, office supplies, reimbursement for travel expenses, and the like.

Accounts receivable: Money owed to the system, including outstanding water bills, connection fees, reconnection fees, and the like.

Accrual basis of accounting: A means of accounting under which the system records revenue when it is earned (not when it is actually paid) and records expenses when they are incurred (when the system is legally obligated to pay the debt, not when the system actually pays the expense).

Accrued interest: Interest that has been incurred on a debt but not yet paid to the lender by the system. For example, long-term loans or bonds that require annual or semi-annual payments have incurred interest during the months between payments.

Accrued liabilities: Money the system owes its employees or customers, including salaries, unpaid vacation or sick leave, payroll taxes withheld but not yet remitted to the taxing agency, and security deposits from customers.

Acid: A substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH-).

Acre-foot (acre-ft): The volume of water required to cover 1 acre of land (43,560 square feet) to a depth of 1 foot. Equal to 325,851 gallons or 1,233 cubic meters.

Activated sludge: Sludge particles produced in wastewater by the growth of organisms in aeration tanks. The term “activated” comes from the fact that the particles teem with bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living organisms that can feed on the incoming wastewater.

Activated sludge process: A biological wastewater treatment process that speeds up waste decomposition. Activated sludge is added to wastewater, and the mixture is aerated and agitated. After a certain amount of time, the activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank).

Acute toxicity: Any poisonous effect produced within a short time after exposure to the toxic compound, usually within 24 to 96 hours.

Acidic: The condition of water or soil that contains a sufficient amount of acid substances to lower the pH below 7.0.

Action level (AL): A concentration of a contaminant above which additional actions are required by the water system to ensure public health and safety. Other requirements may include additional testing, public notification or capital improvements. The action level is not the same as the maximum contaminant level (MCL).

Activated alumina: A treatment process for removing contaminants from water or wastewater, involving the absorption of contaminants onto the alumina.

Aeration: The process of adding air to water. Air can be added to water by either passing air through water or passing water through air.

Aerobic: A condition in which “free” (atmospheric) or dissolved oxygen is present in the water.

Aerobic treatment unit (ATU): refabricated units that provide wastewater treatment by injecting air into a tank and allowing aerobic bacteria to break down organic matter. They are usually used for onsite or decentralized wastewater treatment.

Agriculture Department: A cabinet-level department of the executive branch of the federal government. Within the U.S. Department of Agriculture is Rural Development (RD), one of its agencies. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD is the Rural Utilities Service (RUS), from which many small, rural water systems receive loans and grants. Also called the U.S. Department of Agriculture, the Department of Agriculture or USDA.

Algae: Microscopic plants that contain chlorophyll and live floating or suspended in water. They also may be attached to structures, rocks or other submerged surfaces. They are food for fish and small aquatic animals. Excess algal growths can impart tastes and odors to potable water. Algae produce oxygen during sunlight hours and use oxygen during the night hours. Their biological activities appreciably affect the pH and dissolved oxygen of the water.

Alkalinity: The capacity of water to neutralize acids. This capacity is caused by the water’s content of carbonate, bicarbonate, hydroxide and occasionally borate, silicate, and phosphate. Alkalinity is expressed in milligrams per liter of equivalent calcium carbonate. Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have a high alkalinity. Alkalinity is a measure of how much acid can be added to a liquid without causing a great change in pH.

Alluvium: A general term for clay, silt, sand, gravel or similar unconsolidated material deposited by a stream or other body of running water.

Alternative system: A wastewater treatment or collection system used instead of a conventional system.

Alum: A combination of an alkali metal, such as sodium, potassium, or ammonium, and a trivalent metal, such as aluminum, iron, or chromium. Potassium aluminum sulfate (or potash alum), the most common form, is used as a coagulant (see alsopolyaluminum chloride).

American Recovery and Reinvestment Act (ARRA): Federal legislation enacted in 2009 to distribute money to various sectors of the economy in order to help lift it from recession. Also known as the economic stimulus.

Anaerobic: A condition in which “free” (atmospheric) or dissolved oxygen is not present in water.

Anaerobic digestion: A sludge-stabilization process that takes place in an environmental without oxygen present.

Anaerobic lagoons: Wastewater treatment ponds that have no dissolved oxygen content.

Anoxic: A condition where free oxygen is not present but nitrate is present.

Apparent water loss: Non-physical water losses that occur due to customer meter inaccuracies, data-handling errors in customer billing systems, and unauthorized consumption.

Aquifer: A natural, underground layer of porous, water-bearing materials (sand, gravel) usually capable of yielding a large amount or supply of water.

Aquitard: An underground geological formation that is slightly permeable and yields inappreciable amounts of water when compared to an aquifer.

ARRA (American Recovery and Reinvestment Act): Federal legislation enacted in 2009 to distribute money to various sectors of the economy in order to help lift it from recession. Also known as the economic stimulus.

Artesian: Water held under pressure in porous rock or soil confined by impermeable geologic formations. An artesian well is free-flowing.

Artesian aquifer: An aquifer that contains water under pressure as a result of hydrostatic head. For artesian conditions to exist, an aquifer must be overlain by a confining material and receive a supply of water. The free water surface stands at a higher elevation than the top of the confining layer. Thus, if the aquifer is tapped by a well, the water in the well will raise above the level of the aquifer.

Artesian well: A well whose water is supplied by a artesian aquifer.

Artificial recharge: An process in which water is put back into ground water storage from surface-water supplies, such as irrigation, or induced infiltration from streams or wells.

Asset management: A planning process for efficiently preserving or replacing critical infrastructure.

Assets: The total economic resources of the system that are expected to provide benefits to the system in the future. Assets are listed in an order based on how easily they are converted to cash: cash, cash equivalents, current assets, long-term assets, and property, plant and equipment.

Atmosphere: The gaseous layer that surrounds the earth (air).

Attached growth process: A wastewater treatment process in which the microorganisms that provide the treatment are attached to an inert surface or medium such as rock or plastic. It is also referred to as fixed-film process.

Auditor opinion: The results page of an external audit, on which the auditor states whether or not mistakes were found in the system’s financial records. An “unqualified opinion” or a “clean opinion” are the best that a system can hope for. They mean no material mistakes were found.

Backflow: A reverse flow condition created by a difference in water pressures, which causes water to flow back into the distribution pipes of a potable water supply from any source or sources other than an intended source.

Bacteria (singular: bacterium): Microscopic living organisms usually consisting of a single cell. Bacteria can aid in pollution control by consuming or breaking down organic matter in sewage, or by similarly acting on oil spills or other water pollutants. Some bacteria in soil, water or air may also cause human, animal and plant health problems.

Balance sheet: Also known as the statement of financial position, this document shows a system’s net worth (how much the system is worth at a particular point in time). The balance sheet reflects how total assets = liabilities + equity.

Base: A substance that has a pH of more than 7, which is neutral. A base has less free hydrogen ions (H+) than hydroxyl ions (OH-).

Base flow: Stream flow coming from ground-water seepage into a stream.

Bedrock: A general term for any consolidated rock.

Belt-filter press: A sludge dewatering device that uses two fabric belts that squeeze water from the sludge.

Benchmarking program: The process of determining who is the very best, who sets the standard, and what that standard is. Benchmarking allows you to compare your system with others, to identify comparative strengths and weaknesses and learn how to improve.

Best management practices (BMPs): Structural, nonstructural and managerial techniques that are recognized to be the most effective and practical means to control nonpoint source pollutants yet are compatible with the productive use of the resource to which they are applied. BMPs are used in both urban and agricultural areas.

Biochemical oxygen demand (BOD): The amount of oxygen consumed by microorganisms (mainly bacteria) and by chemical reactions in the biodegradation of organic matter.

Biomass: Microbial growth

Biosolids: The nutrient-rich organic materials resulting from the treatment of sewage sludge.

Biosphere: All living organisms (plant and animal life).

Black water: Water containing liquid and solid human body waste generated through toilet use.

Blending: When a drinking water supply system can or does combine (for example, via connecting piping and associated valves) water from more than one well or surface water intake, or from a combination of wells and intakes. 

Blue baby syndrome: A blood-related condition in babies due to nitrate poisoning (poisoning limits blood’s ability to carry oxygen, thereby causing baby to look blue hued); known as methemoglobinemia.

Bored well: A well drilled with a large truck-mounted boring auger, usually 12 inches or more in diameter and seldom deeper than 100 feet.

Borrower: The legal entity that is the recipient of a loan, usually from USDA‘s Rural Utilities Service.

Business continuity plan: A plan for working out how to stay in business in the event of a disaster or emergency. These events include local incidents like building fires, regional incidents like earthquakes, or national incidents like pandemic illnesses.

CaCO3: Calcium carbonate

Calorie: The amount of heat required to raise the temperature of one gram of water by one degree centigrade.

Capillary fringe: A zone in the soil just above the water table that remains saturated or almost saturated.

Capital costs: Costs (usually long-term debt) of financing construction and equipment. Capital costs are usually fixed, one-time expenses which are independent of the amount of water produced.

Carcinogenic: Event, condition or effect that produces cancer.

Cash: The amount of money currently available in the system’s demand accounts.

Cash equivalents: Securities that have a maturity date of less than 90 days from the balance sheet date.

Cash-flow statement: This document shows how each financial transaction (financing activities, investing activities, and operating activities) conducted by the system affects its cash.

CCR (Central Contractor Registration): a federal government database that gathers, stores, validates, and shares information to support federal grants and contracts. (To register with CCR, go to

Central Contractor Registration (CCR): a federal government database that gathers, stores, validates, and shares information to support federal grants and contracts. (To register with CCR, go to

Centralized system/wastewater treatment: One in which wastewater is collected from the community and pumped to a central treatment facility.

Certification: Minimum professional standards for the operation and maintenance of public water and wastewater systems (usually applied to a system’s operators).

Chlorination: The application of chlorine to water, sewage, or industrial wastes, generally to disinfect, to oxidize, or to improve settling.

Clarifier: Removes solids from wastewater by gravity settling or by coagulation. Also referred to as a settling tank or sedimentation tank.

Class A biosolids: Biosolids that meet the criteria of the Part 503 rules allowing them to be used in parks, gardens, and golf courses.

Class B biosolids: Biosolids that do not meet all the criteria for Class A biosolids. They may be applied to agricultural land or disposed of in landfills.

Clean Water Act (CWA): The federal legislation that establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution Control Act, but it was significantly reorganized and expanded in 1972. “Clean Water Act” became the act’s common name with amendments in 1977. Under the CWA, EPA has implemented pollution-control programs, such as setting wastewater standards for industry and water-quality standards for all contaminants in surface waters. The CWA made it unlawful to discharge any pollutant from a point source into navigable waters unless a permit was obtained. EPA’s National Pollutant Discharge Elimination System (NPDES) permit program controls discharges.

Cluster system: A wastewater treatment system that uses septic tanks located at each house to remove solids and small-diameter sewers to convey the liquid effluent to a central area for additional treatment and/or dispersal, often through a community soil-absorption system.

Coagulation: The clumping together of very fine particles into larger particles caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles and cause destabilization of the particles. This clumping together makes it easier to separate the solids from the water by settling, skimming, draining, or filtering.

Coliform: A group of bacteria found in the intestines of warm-blooded animals (including humans) and also in plants, soil, air and water. Fecal coliforms are a specific class of bacteria that inhibit the intestines of warm-blooded animals only. The presence of coliform is an indication that the water is polluted and may contain pathogenic organisms.

Collection system: The pipes, tanks, valves, and pumps that work together to transport municipal waste from the point it is generated to the treatment system.

Colloidal: Particles in suspension in wastewater that are small enough to not readily settle out during primary treatment.

Combined filter effluent: Water that exits the filtering process and goes to a clearwell for disinfection. For water systems using conventional or direct filtration, the maximum turbidity allowed by the EPA is 1 nephelometric turbidity unit (NTU), and at least 95 percent of turbidity measurements taken each month shall be < 0.3 NTU.  For water systems using slow sand, diatomaceous earth, or alternative technologies approved by the state, the maximum turbidity allowed by the EPA is 5 NTU, and at least 95 percent of turbidity measurements taken each month shall be < 1 NTU.

Combined sewers: Sewers that carry both sanitary sewage and stormwater runoff.

Commercial water use: Water used for motels, hotels, restaurants, office buildings, other commercial facilities, and institutions. Water for commercial uses comes both from public-supplied sources, such as a county water department, and self-supplied sources, such as local wells.

Communitor: A machine that performs size reduction of debris in wastewater.

Community water system (CWS): A public water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents.

Compliance: Meeting the laws and regulations established by the U.S. Environmental Protection Agency (EPA), the state, the tribe, or other applicable governing entities.

Composting: The natural biological decomposition of organic material in the presence of air to form a stabilized, humus-like in consistency.

Condensation: The process in which water vapor is cooled to the liquid phase.

Conditioning: The addition of chemicals to sludge to aid in the dewatering process. Conditioning chemicals include alum, lime, ferric chloride, and synthetic organic polymers.

Confined aquifer: An aquifer in which groundwater is confined under a pressure which is significantly greater than atmospheric pressure.

Confining layer: Geological material through which significant quantities of water cannot move; located below unconfined aquifers, above and below confined aquifers. Also known as a confining bed.

Consent agenda: An agenda that contains items that need to be voted upon but do not need further discussion. Common items on a consent agenda are approval of meeting minutes and acceptance of reports that are attached to the minutes.

Consolidated rock: Bedrock.

Consumer confidence report (CCR): An annual report on the quality of water treatment, given to consumers by community water systems.

Consumptive use: The total amount of water taken up by vegetation for transpiration or building of plant tissue, plus the unavoidable evaporation of soil moisture, snow, and intercepted precipitation associated with vegetal growth.

Consumption: Water that is actually consumed, transpired, or incorporated into new products as it is used.

Contaminant level violation: A violation of EPA regulations that occurs when a contaminant which has the potential to cause illness is not removed to at least the level described in the regulations.

Contamination: The introduction into water of microorganisms, chemicals, toxic substances, wastes, or wastewater in a concentration that makes the water unfit for its next intended use.

Conventional filtration: A process for filtering water, including coagulation, flocculation, and sedimentation, prior to filtration. Also called complete treatment or conventional treatment.

Conventional septic system: A septic system with a standard septic tank and soil-absorption system in which the wastewater flow is moved by gravity.

Conveyance loss: Water that is lost in transit from a pipe, canal, or ditch by leakage or evaporation. Generally, the water is not available for further use; however, leakage from an irrigation ditch, for example, may percolate to a ground-water source and be available for further use.

Cost/benefit analysis: A quantitative evaluation of the costs that would be incurred versus the overall benefits to society of a proposed action, such as the establishment of an acceptable dose of a toxic chemical.

Cost sharing: A publicly financed program through which society, as the beneficiary of environment protection, shares part of the cost of pollution control with those who must actually install the controls.

Cross-connection: Any actual or potential connection between a drinking (potable) water system and an unapproved water supply or other source of contamination. For example, if a pump moves nonpotable water and is hooked into the groundwater system to supply water for the pump seal, a cross-connection or mixing between the two water systems can occur. This mixing may lead to contamination of the drinking water.

Cryptosporidium: A waterborne microorganism (protozoa) that causes gastrointestinal illness (cryptosporidiosis), including diarrhea and vomiting. These tiny pathogens are found in surface water sources like reservoirs, lakes, and rivers.

Cubic feet per second (cfs): A rate of the flow, in streams and rivers, for example. It is equal to a volume of water one foot high and one foot wide flowing a distance of one foot in one second. One “cfs” is equal to 7.48 gallons of water flowing each second. As an example, if your car’s gas tank is 2 feet by 1 foot by 1 foot (2 cubic feet), then gas flowing at a rate of 1 cubic foot/second would fill the tank in two seconds.

Current assets: Items that can be converted to cash within one year of the date of the balance sheet, including cash, cash equivalents, accounts receivable, inventory, short-term investments, and prepaid assets.

Current liabilities: Maturities on long-term debt, accounts payable, accrued liabilities and other short-term notes to be paid by the system.

Current maturities on long-term debt: The principal amount the system is required to pay on long-term loans over the next 12 months. This is not equivalent to the total loan payment amount, which is the principal plus interest.

Current ratio: See liquidity ratio.

Data Universal Numbering System (DUNS) number: a nine-digit number assigned to organizations and business entities as a means to identify and track them. A DUNS number is required by the federal government for all entities applying for and receiving federal grants. (To register for a DUNS number, call 1-866-705-5711, or visit

Decant: To draw off liquid without disturbing the sediment.

Decentralized system/wastewater treatment: A system in which wastewater is collected and treated onsite rather than gathered in a collection system and transported to a wastewater treatment plant.

Deep percolation: Water that moves downward through the soil profile below the root zone and cannot be used by plants.

Deficit equity: When the system has incurred more in net losses over its life than net income.

Degradation: To wear down, reduce to lower quality, by erosion or reduce the complexity of a chemical compound.

Denitrification: The reduction of nitrate to nitrogen gas, carried out in wastewater treatment tanks by bacteria under anoxic conditions. The bacteria use the nitrate for energy, and in the process, release nitrogen gas. The nitrogen gas, a major constituent of air, is released to the atmosphere. Nitrogen can cause algae blooms that deplete oxygen in the water that marine life needs to survive. Nitrogen is found in agricultural runoff and suburban and urban runoff as well as wastewater treatment plants.

Depreciation: The decrease in the value of fixed assets from normal wear and tear due to age and typical use. The easiest method used to calculate depreciation is the straight-line method, but other methods include the declining-balance method, the activity-depreciation method, the sum of years’ digits method, and others.

Debt-service coverage ratio: A measure of the system’s ability to pay its debt, this ratio (also called the coverage ratio) is calculated by dividing the sum of the net operating income plus depreciation by the total debt service. An adequate debt-service coverage ratio varies from system to system, depending upon lenders’ requirements or sometimes state statute. The Rural Utilities Service Water and Waste Disposal Loan Program prefers a minimum debt-service coverage ratio of 1.1 for financial viability.

Department of Agriculture: A cabinet-level department of the executive branch of the federal government. Within the U.S. Department of Agriculture is Rural Development (RD), one of its agencies. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD is the Rural Utilities Service (RUS), from which many small, rural water systems receive loans and grants. Also called the Agriculture Department, the U.S. Department of Agriculture, or USDA.

Depression storage: Water stored in surface depressions and therefore not contributing to surface runoff.

Desalinization: The removal of salts from saline water to provide freshwater. This method is becoming a more popular way of providing freshwater to populations.

Dew point: The temperature to which air must be cooled to cause condensation of the water vapor it contains. The higher the dew point, the higher the moisture content of the air.

Direct filtration: A process for filtering water that includes coagulation and flocculation prior to filtration. Direct filtration differs from conventional filtration in that the sedimentation process (allowing floc to settle out from the water prior to filtration) is not performed.

Discharge: The flow of surface water in a stream or canal or the outflow of ground water from a well, ditch, or spring.

Disinfectant: Any oxidant, including, but not limited to, chlorine, chlorine dioxide, chloramines, and ozone, that is added to water in any part of the treatment or distribution process and is intended to kill or inactivate pathogenic microorganisms.

Disinfectants and Disinfection Byproducts Rule (DDBPR): The federal regulation that sets limits on disinfection byproducts in public drinking water systems.

Disinfection: The killing of microorganisms, some of which may be disease-causing organisms.

Disinfection byproduct (DBP): A compound formed by the reaction of a disinfectant, such as chlorine with organic material in the water supply.

Disinfection profile: If a public water system has an annual average level of total trihalomethanes (TTHM) of 0.064 mg/L or an annual average level of haloacetic acids (HAA5) of 0.048 mg/L, the system must develop a disinfection profile. The profile is developed by compiling daily Giardia lamblia log inactivation values for 12 months, and for systems using chloramines or ozone for primary disinfection, compiling daily virus log inactivation values for 12 months. Log inactivation values are calculated using daily measurements of operational data collected during peak-hour flows.

Dissolved oxygen: The amount of free oxygen in solution in water or wastewater effluent. Adequate concentrations of dissolved oxygen are necessary for fish and other aquatic organisms to live and to prevent offensive odors.

Distribution system: The system of tanks, pipes, pumps, and valves that delivers treated water from the drinking water treatment system to the customer.

Domestic water use: Water used for household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens. About 85% of domestic water is delivered to homes by a public-supply facility, such as a county water department. About 15% of the nation’s population supply their own water, mainly from wells.

Drainfield: The part of a septic system in which the clarified liquid effluent is dispersed into soil for final treatment and disposal. Also referred to as a soil-absorption system or leachfield.

Drainage basin: Land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the Mississippi River, contain thousands of smaller drainage basins. Also called a watershed.

Drainage well: (1) a well pumped in order to lower the watertable; (2) vertical shaft to a permeable substratum into which surface and subsurface drainage is channeled (now illegal).

Drawdown: (1) lowering of the watertable, surface water, or piezometric surface resulting from the withdrawal of water from a well or drain; (2) the elevation of the static water level (at the well) at a given discharge.

Drilled well: A well usually 10 inches or less in diameter, drilled with a drilling rig and cased with steel or plastic pipe. Drilled wells can be of varying depth.

Drinking Water State Revolving Loan Funds (DWSRF or simply SRF): Federal money provided to qualifying states to address problems of deteriorating water systems. States may provide these funds in the form of low- or no-interest loans to eligible water systems for upgrading their facilities and ensuring compliance with drinking water standards. DWSRF loan programs vary from state to state.

Drip dispersal: A form of final dispersal of treated wastewater in which the effluent is applied to soil slowly and uniformly through a network of narrow, flexible tubes placed in the soil at shallow depths. It is also referred to as drip irrigation.

Dug well: A large-diameter well dug by hand, usually old and often cased by concrete or hand-laid bricks. Such wells typically reach less than 50 feet in depth and are easily and frequently contaminated.

DUNS (Data Universal Numbering System) number: a nine-digit number assigned to organizations and business entities as a means to identify and track them. A DUNS number is required by the federal government for all entities applying for and receiving federal grants. (To register for a DUNS number, call 1-866-705-5711, or visit

E. coli  (full name: Escherichia coli): a Gram-negative rod-shaped bacterium that is commonly found in the lower intestine of mammals, most of which are harmless, but some of which can cause gastrointestinal distress in humans.

Echovirus: An ECHO (Enteric Cytopathic Human Orphan) virus is a type of RNA virus that belongs to the genus Enterovirus of the Picornaviridae family. Echoviruses are found in the human gastrointestinal tract, and exposure to the virus causes other opportunistic infections and diseases.

Effluent: Water or some other liquid—raw, partially or completely treated—flowing from a reservoir, basin, treatment process or treatment plant.

Emergency operating procedures (EOP): A detailed set of written procedures documenting changes in standard operating procedures during emergencies, such as severe weather events.

Emergency management agency compact (EMAC): A voluntary agreement between neighboring water or wastewater treatment systems that are not located within a single state to detail assistance in emergencies.

Emergency-response plan (ERP): A written document that details the water or wastewater system’s plan of action for responding to emergencies, disasters, and other unforeseen events.  Updated ERPs should incorporate the results of the vulnerability assessment (VA) and must address terrorist or other intentional acts. The ERP may include detailed steps that the public water system will take to respond to potential or actual emergencies including, but not limited to, the following: loss of water supply from a source; loss of water supply due to a major component failure; damage to power supply equipment or loss of power; contamination of water in the distribution system from backflow or other causes; and the like. The ERP may also include a description of the procedures, structures and equipment used to respond to potential or actual emergencies. Requirements, guidelines and compliance checklists are available through the state primacy agency and/or state drinking water program.

Environmental Protection Agency: The federal agency responsible for researching and setting national standards for a variety of environmental programs. The EPA works to develop and enforce regulations that implement environmental laws enacted by congress. Its website is Also known as EPA, the U.S. Environmental Protection Agency, or the U.S. EPA.

EPA: The federal agency responsible for researching and setting national standards for a variety of environmental programs. The EPA works to develop and enforce regulations that implement environmental laws enacted by congress. Its website Also known as EPA, the Environmental Protection Agency, the U.S. Environmental Protection Agency, or the U.S. EPA.

Equity: The net value of the system over time. Equity increases each year the system earns a net income (has more revenue than expenses), and equity decreases each year the system incurs a net loss (has more expenses than revenue).

Erosion: The wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep. Geological erosion is naturally occurring erosion over long periods of time. Accelerated erosion is more rapid than normal erosion and results primarily from human activities. Erosion is further classified by the amount and pattern of soil removal and transport as gully, interrill, rill, sheet, and splash or raindrop erosion.

Estuary: A place where fresh and salt water mix, such as a bay, salt marsh, or where a river enters an ocean.

Eutrophication: The natural or artificial process of nutrient enrichment whereby a water body becomes filled with aquatic plants and low oxygen content. The low oxygen level is detrimental to fish.

Evaporation: The process in which liquid water is transferred into the atmosphere.

Evapotranspiration: The combined loss of water to the atmosphere from land and water surfaces by evaporation and from plants by transpiration.

Exemption: A state with primacy (primary regulatory authority) may relieve a public water system from a requirement respecting an MCL, treatment technique or both, by granting an exemption if certain conditions exist. These are: 1) the system cannot comply with an MCL or treatment technique due to compelling factors, which may include economic factors; 2) the system was in operation on the effective date of the MCL or treatment-technique requirement; and 3) the exemption will not result in an unreasonable public health risk.

Exothermic: A chemical reaction that releases energy in the form of heat.

Extended aeration: A variation of the activated sludge treatment process with a long detention time resulting in heavy competition for food by the microorganisms and little production of sludge.

Facultative lagoons: A wastewater treatment pond that contains some areas where dissolved oxygen is present and others where oxygen is absent.

Filtration: A process for removing particulate matter from water by passage through porous media.

Financially sustainable: A system that provides water or wastewater treatment services to customers at a rate that consistently generates enough money to meet all expenses, both in the short- and long-term.

Financing activities: Transactions resulting from activities to attract investors or creditors (for instance, loans to purchase assets or for major system repairs).

Finished water: Water that has passed through a water treatment plant—when all of the treatment processes are completed or “finished.” This water is ready to be delivered to consumers.

Fiscal year: A 12-month period that is the basis of the system’s operations. A fiscal year may be different from a calendar year, and if it is, common spans are July 1 to June 30 or October 1 to September 30 (which is the federal government’s fiscal year).

Fixed assets: The land, buildings, furniture and fixtures the system owns and uses in its day-to-day operations.

Fixed film system: A wastewater treatment process in which the microorganisms that provide the treatment are attached to an inert surface or medium, such as rock or plastic. It is also referred to as attached-growth process.

Floc: Clumps of bacteria and particulate impurities that have come together and formed a cluster. Found in flocculation tanks and settling or sedimentation basins.

Flocculation: The gathering together of fine particles in water by gentle mixing after the addition of coagulant chemicals to form larger particles.

Flood: An overflow of water onto lands that are used or usable by humans and not normally covered by water. Floods have two essential characteristics: the inundation of land is temporary; and the land is adjacent to and inundated by overflow from a river, stream, lake, or ocean.

Flood plain: A strip of relatively flat and normally dry land alongside a stream, river, or lake that is covered by water during a flood.

Flood stage: The elevation at which overflow of the natural banks of a stream or body of water begins in the reach or area in which the elevation is measured.

Flood, 100-year: Does not refer to a flood that occurs once every 100 years, but to a flood level with a 1 percent chance of being equaled or exceeded in any given year.

Flow diagram: A very simple diagram that shows where water or wastewater comes from, what treatment processes it goes through, and where it exits the treatment system.

Flowing well/spring: A well or spring that taps ground water under pressure so that water rises without pumping. If the water rises above the surface, it is known as a flowing well.

F:M: Food-to-microbe ratio.

Freshwater: Water that contains less than 1,000 milligrams per liter (mg/L) of dissolved solids; generally, more than 500 mg/L of dissolved solids is undesirable for drinking and many industrial uses.

FRPIN (federal reporting personal identification number): Required by the website to report ARRAprojects online. Once registered at, the FRPIN must be requested using a link on the left side. Once approved, a nine-digit number will be provided. That number will allow full access to the site for reporting.

Full-cost pricing: Calculating and setting rates that reflect the true cost of producing and selling water, including operating expenses, debt service, and reserve funds for equipment replacement and future improvements or expansion.

Fungi: Mushrooms, molds, mildews, rusts, and smuts that are small, non-chlorophyll-bearing plants lacking roots, stems and leaves. They occur in natural waters and grow best in the absence  of light. Their decomposition may cause objectionable tastes and odors in water.

Gage height: The height of the water surface above the gage datum (zero point). Gage height is often used interchangeably with the more general term stage, although gage height is more appropriate when used with a gage reading.

Gaging station: A site on a stream, lake, reservoir or other body of water where observations and hydrologic data are obtained. The U.S. Geological Survey measures stream discharge at gaging stations.

Geyser: A geothermal feature of the Earth where there is an opening in the surface that contains superheated water that periodically erupts in a shower of water and steam.

Giardia lamblia: A microorganism (protozoa), sometimes found in drinking water, that may cause diarrhea, cramps, and illness (giardiasis). Giardia is commonly found in surface water sources like reservoirs, lakes, and rivers.

Giardiasis: A disease that results from an infection by the protozoan parasite Giardia Intestinalis, caused by drinking water that is either not filtered or not chlorinated. The disorder is more prevalent in children than in adults and is characterized by abdominal discomfort, nausea, and alternating constipation and diarrhea.

Glacier: A huge mass of ice, formed on land by the compaction and recrystallization of snow, that moves very slowly downslope or outward due to its own weight.

Grey water: Domestic wastewater other than sewage, such as sink drainage or washing machine discharge.

Grinder: A machine that performs size reduction of debris in wastewater.

Grit chamber: A small detention basin designed to permit the settling of coarse, heavy inorganic solids, such as sand, while allowing the lighter organic solids to pass through the chamber.

Ground water: The supply of fresh water found beneath the Earth’s surface, usually in aquifers, that is often used for supplying wells and springs. Because groundwater is a major source of drinking water, there is growing concern over areas where leaching agricultural or industrial pollutants or substances from leaking underground storage tanks are contaminating ground water.

Ground water, confined: Ground water under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.

Ground-water recharge: Inflow of water to a ground water reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.

Ground Water Rule (GWR): The federal regulation for drinking water systems that use ground water as their source water.

Ground water, unconfined: Water in an aquifer that has a water table that is exposed to the atmosphere.

Ground water under the direct influence (GWUDI) of surface water: Any water beneath the surface of the ground with: 1) significant occurrence of insects or other macroscopic organisms, algae, or large-diameter pathogens such as Giardia lamblia; or 2) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Direct influence must be determined for individual sources in accordance with criteria established by the state. The state determination of direct influence may be based on site-specific measurements of water quality and/or documentation of well-construction characteristics and geology with field evaluation.

Half life: The time it takes certain materials, such as persistent pesticides, to become chemically altered.

Haloacetic acids (HAA5): A group of chemicals that are formed along with other disinfection byproducts when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic  and inorganic  matter in water. The EPA -regulated haloacetic acids are monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid.

Hardness: A characteristic of water caused by various salts, calcium, magnesium and iron (e.g., bicarbonates, sulfates, chlorides and nitrates)

Hazardous waste: Materials that, because of their quantity, concentration, or physical, chemical, or infectious characteristics, may cause mortality (death), injury, or serious illness.

Headwater(s): 1) the source and upper reaches of a stream; also the upper reaches of a reservoir. 2) The water upstream from a structure or point on a stream. 3) The small streams that come together to form a river. Also may be thought of as any and all parts of a river basin except the mainstream river and main tributaries.

Headworks: The first process in wastewater treatment, which removes large debris (cans, plastic bags, and other garbage) from the wastewater stream.

Helminths: Parasitic roundworms or flatworms.

Herbicide: Chemicals used to kill undesirable vegetation.

High-density polyethylene (HDPE): Synthetic pipe material often used in drinking water distribution systems.

Hydraulic analysis: An analysis of the factors that contribute to how well water moves through a treatment system (such as headloss, pipe age and condition, friction, and other factors).

Hydraulic capacity: The maximum amount of water that can pass through a water or wastewater treatment system.

Hydrograph: A graph that illustrates hydrologic measurements over a period of time, such as water level, discharge or velocity.

Hydrologic cycle: The circulation of water in and on the Earth and through Earth’s atmosphere through evaporation, condensation, precipitation, runoff, ground water storage and seepage, and re-evaporation into the atmosphere.

Hydrosphere: Water held in oceans, rivers, lakes, glaciers, ground water, plants, animals, soil, and air.

Impermeable layer: A layer of solid material, such as rock or clay, that does not allow water to pass through.

Incident command system (ICS): Common terminology that allows diverse incident-management and support organizations to work together across a wide variety of incident-management functions and hazard scenarios. Common terminology covers:

  • organizational functions and functional units with incident-management responsibilities are named and defined; terminology for the organizational elements is standard and consistent.
  • resource descriptions, including personnel, facilities, and major equipment and supply items that support incident management activities, are given common names and are classified according to their capabilities to help avoid confusion and to enhance interoperability.
  • incident facilities in the vicinity of the incident area that will be used during the course of the incident.

Incident-response communications (during exercises and actual incidents) should feature plain-language commands so they will be able to function in a multijurisdiction environment. Field manuals and training should be revised to reflect the plain-language standard.

Income statement: Also known as the statement of activities, this document shows the results of operations over a period of time (how much revenue the system has earned versus the amount of expenses the system has incurred).

Indentures: Written agreements between the issuer of a bond and the bondholders, usually specifying the interest rate, maturity date, convertibility and other terms.

Indicator organisms: Microorganisms whose presence in a water sample are used as an indication of the presence of fecal contamination and possibly the presence of pathogenic microorganisms.

Infiltration: The downward entry of water through the soil surface into the soil.

Infiltration rate: The quantity of water that enters the soil surface in a specified time interval. Often expressed in volume of water per unit of soil surface area per unit of time (in/hr, cm/hr).

Influent: Water or other liquid-raw or partially flowing into a reservoir, basin, treatment process or treatment plant.

Injection well: A well constructed for the purpose of injecting treated wastewater directly into the ground. Wastewater is generally forced (pumped) into the well for dispersal or storage into a designated aquifer. Injection wells are generally drilled into aquifers that do not deliver drinking water, unused aquifers, or below freshwater levels.

Inorganic: Material such as sand, salt, iron, calcium salts and other mineral materials. Inorganic substances are of mineral origin, whereas organic substances are usually of animal or plant origin.

Insecticide: Chemicals used to control undesirable insects.

Interceptors: Large sewer lines that collect the flows from smaller main and trunk sewers and carry them to the treatment plant.

Interim Enhanced Surface Water Treatment Rule (IESWTR): The federal regulation that improves control of microbial contaminants, particularly Cryptosporidium, in systems using surface water and serving 10,000 or more people (see also Surface Water Treatment Rule).

Inventory: The value of products related to the business that are or will become available for sale within the next year, such as new meters, pipe, equipment and replacement parts.

Investing activities: Transactions resulting from activities to obtain property, facilities and equipment necessary to run the system, or to invest idle cash (such as purchasing stocks or bonds, new buildings or new equipment).

Ion exchange: A technology for removing charged contaminants from water or wastewater.

Irrigation: The controlled application of water for agricultural purposes through human-made systems to supply water requirements not satisfied by rainfall.

Irrigation water use: Water application on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands, such as parks and golf courses.

Jar test: A laboratory procedure for evaluating coagulation and rapid mix, flocculation, and sedimentation processes in a series of parallel comparisons.

Jet: A stream of water under pressure coming from an orfice, nozzle, or tube.

Junction: A converging section of a conduit used to facilitate the flow from one or more conduits into a main conduit.

Karsts: Strata in limestone deposits that have dissolved away can create direct pathways from surface water to groundwater.

Kilogram: 1,000 grams.

Kilowatthour (KWH): A power demand of 1,000 watts for one hour. Electric utility rates are typically expressed in cents per kilowatt-hour.

Lagoon: Water impoundment in which organic wastes are stored or stabilized or both.

Latent heat: The heat (energy) absorbed or released as water changes between the gas (water vapor), the liquid (water droplets), and the solid (ice) states.

Lateral sewers: Small underground pipes that transport sewage from homes and businesses to the larger sewer lines leading to a wastewater treatment plant

LD50: The dosage of a toxic substance required to kill one half of the organisms under study in a given period of time.

Leachate: Liquids that have percolated through a soil and that carry substances in solution or suspension.

Leachfield: The part of a septic system where clarified liquid effluent is dispersed into soil for final treatment and disposal. Also referred to as a drainfield or soil-absorption system.

Leaching: The downward transport of dissolved or suspended minerals, fertilizers and other substances by water passing through a soil or other permeable material.

Lead and Copper Rule (LCR): The federal regulation setting limits for lead and copper in the distribution system.

Lentic waters: Ponds or lakes (standing water).

Lethal dose (LD): The amount of a toxic substance required to cause death of an organism under study in a given period of time.

Letter of conditions: a written document that describes the conditions which a borrower and/or grantee must meet for funds to be advanced and the loan and/or grant to be closed.

Levee: A natural or human-made earthen barrier along the edge of a stream, lake, or river. Land alongside rivers can be protected from flooding by levees.

Leverage ratio: A measure of the system’s reliance upon debt, this ratio is calculated by dividing equity by total assets. Systems with a leverage ratio of less than 0.30 are considered to be in financial distress.

Liabilities: What the system owes to others.

Life of assets: The length of time the asset is assumed to be used. Buildings have a normal life of 30 years. Land value does not depreciate.

Liquidity: The ability to convert an asset into cash.

Liquidity ratio: A measure of the system’s ability to pay off current liabilities, this ratio is calculated by dividing the system’s current assets by its current liabilities. Systems with a liquidity ratio of less than 1.5 are considered to be in financial distress.

Lithosphere: A general term for the outer layer of the earth.

Loading: The quantity of material added to a process at one time.

Loess: A wind-blown deposit of silty soil having little or no stratification.

Long-term assets: Items that cannot be converted to cash within one year of the date of the balance sheet, such as investments with maturity dates greater than one year.

Long-term debt: See the definition for long-term liabilities.

Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR): The federal regulation requiring certain public water systems to meet strengthened filtration requirements and to calculate levels of microbial inactivation to ensure that microbial protection is not jeopardized if systems make changes to comply with requirements of the Stage 1 Disinfectants and Disinfection Byproducts Rule (Stage 1-DBPR) (see also Interim Enhanced Surface Water Treatment Rule).

Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR): The federal regulation designed to reduce illness linked to disease-causing microorganisms in drinking water. The rule supplements existing regulations by targeting additional Cryptosporidium treatment requirements in higher risk systems. This rule also contains provisions to reduce risks from uncovered finished water reservoirs and to ensure that systems maintain microbial protection when they take steps to decrease the formation of disinfection byproducts that result from chemical water treatment.

Long-term liabilities: Loans expected to be paid back by the system over several years, such as capital-improvement loans. The principal amount to be repaid within one year is recorded in current liabilities as a current maturity; the remainder of the principal is listed as a long-term liability.

Macerator: A machine that performs size reduction of debris in wastewater.

Manure: The fecal and urinary defecation of livestock and poultry.

Maximum contaminant level (MCL): The maximum permissible level of a contaminant in water that is delivered to the free-flowing outlet of the ultimate user of a public water system, except in the case of turbidity, where the maximum permissible level is measured at the point of entry to the distribution system. Contaminants added to the water under circumstances controlled by the user are excluded from this definition, except those contaminants resulting from the corrosion of piping and plumbing caused by water quality.

Maximum contaminant level goal (MCLG): The maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non-enforceable health goals.

Membrane: A technology for removing contaminants from water or wastewater; types include microfilters, ultrafilters, reverse-osmosis and nanofilters.

Microgram per liter (μg/L): A measure of concentration of a dissolved substance. A concentration of one μg/L means that one microgram of a substance is dissolved in each liter of water. For practical purposes, this unit is equal to parts per billion (ppb), since one liter of water is equal in weight to one billion micrograms. Thus, a liter of water containing 10 micrograms of lead has 10 parts of lead per one billion parts of water, or 10 parts per billion (10 ppb).

Milligram (mg): One-thousandth of a gram.

Milligrams per liter (mg/L): A measure of concentration of a dissolved substance. A concentration of one mg/L means that one milligram of a substance is dissolved in each liter of water. For practical purposes, this unit is equal to parts per million (ppm), since one liter of water is equal in weight to one million milligrams. Thus, a liter of water containing 10 milligrams of calcium has 10 parts of calcium per one million parts of water, or 10 parts per million (10 ppm).

Million gallons per day (mgd): A rate of flow of water equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).

Maximum residual disinfection level (MRDL): The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

Maximum residual disinfection level goal (MRDLG): The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLG do not reflect the benefits of the use of disinfectants to control microbial contaminants.

Mining water use: Water use during the quarrying rocks and extracting minerals from the land.

Mixed liquor: Activated sludge mixed with wastewater in an activated sludge treatment process.

Mixed liquor suspended solids (MLSS): The suspended solids in the mixture of activated sludge and wastewater that undergoes aeration in an activated sludge treatment process.

Mound system: An effluent disposal system involving a mound of sand built on the original ground surface to which effluent is distributed.

mrem/year: millirems per year. A measure of radiation absorbed by the body.

Municipal water system: A water system that has at least five service connections or that regularly serves 25 individuals for 60 days; also called a public water system.

Municipal sewage: Wastes (mostly liquid) originating from a community. Municipal sewage may be composed of domestic wastewaters and/or industrial wastewaters.

National Pollutant Discharge Elimination System (NPDES) Permit: The regulatory agency document issued by either a federal or state agency that is designed to control all discharges of pollutants from point sources in U.S. waterways. NPDES permits regulate discharges into navigable waters from all point sources of pollution, including industries, municipal treatment plants, large agricultural feed lots, and return-irrigation flows.

ND: non-detectable

Nephelometric: A means of measuring turbidity in a sample by using an instrument called a nephelometer. A nephelometer passes light through a sample, and the amount of light deflected (usually at a 90-degree angle) is then measured in nepehlometric turbidity units (NTU).

Net operating income/loss: Calculated by subtracting operating expenses from revenue.

NH3-N: Measurement of ammonia in the form of nitrogen.

NO2-N: Measurement of nitrite in the form of nitrogen.

Nitrate (NO3): An important plant nutrient and type of inorganic fertilizer (most highly oxidized phase in the nitrogen cycle). In water, the major sources of nitrates are septic tanks, feed lots and fertilizers.

Nitrite (NO2): Product in the first step of the two-step process of conversion of ammonium (NH4) to nitrate (NO3).

Nitrification: The biochemical oxidation of ammonium to nitrate.

Nitrogen: Too much nitrogen and phosphorus in water—known as nutrient pollution—cause significant increases in algae, which harms water quality, food resources and habitats, and decreases the oxygen that fish and other aquatic life need to survive.

Non-community water system (NCWS): A public water system that is not a community water system. There are two types of NCWSs: transient and non-transient.

Nonpoint source: Water pollution that results from land runoff, atmospheric deposition, drainage, or seepage of contaminants. Major nonpoint sources include agricultural, silvicultural, and urban runoff.

Non-potable: Water that may contain objectionable pollution, contamination, minerals, or infective agents and that is considered unsafe and/or unpalatable for drinking.

Non-record material: Extra copies of documents, stockpiles of publications and processed documents, and library material used for reference or exhibition purposes.

Non-transient non-community water system (NTNCWS): A public water system that regularly serves at least 25 of the same nonresident persons per day for more than six months per year. Examples include schools, churches, and workplaces. The same individuals use the water from month to month, but do not live at this facility.

NTU (nephelometric turbidity units): Turbidity is measure with an instrument called a nephelometer, which measures the intensity of light scattered by suspended matter in the water. Measurements are given in nephelometric turbidity units.

Nutrient pollution: Too much nitrogen and phosphorus in water—known as nutrient pollution—cause significant increases in algae, which harms water quality, food resources and habitats, and decreases the oxygen that fish and other aquatic life need to survive.

Nutrients: Elements or compounds essential as raw materials for plant and animal growth and development.

Oocyst: The earliest stage of the life cycle of a parasitic protozoan (e.g., Cryptosporidium) in which it is enclosed in a hard-shelled capsule.

Operating activities: Transactions resulting from activities necessary for the system to perform its function (examples include salaries, office supplies, minor system repairs, purchases of water from other systems, and the like).

Operating expenses: Expenses incurred from the system’s normal operation, including salaries, fringe benefits, utility (electricity, telephone, etc.) bills, insurance, water purchased for resale, etc.

Operating ratio: A measure of the system’s profitability, this ratio is calculated by dividing the operating revenues by the operating expenses. An operating ratio of less than 1.0 is considered to be financially distressed.

Operations and maintenance (O&M) manual: A document detailing how the water or wastewater treatment system is operated and maintained. The level of detail is such that someone who has not performed these duties can use the manual to operate or repair equipment without additional instruction.

Organic: Substances that come from animal or plant sources. Organic substances always contain carbon.

Osmosis: The movement of water molecules through a thin membrane. The osmosis process occurs in our bodies and is also one method of desalinizing saline water.

Other income and expenses: Includes interest income, interest expenses, gains/losses on equipment sales, and unusual items that are not related to the regular operation of the system.

Outfall: The place where a sewer, drain, or stream discharges; the outlet or structure through which reclaimed water or treated effluent is finally discharged to a receiving water body.

Overland flow: Land treatment of wastewater involving the controlled application of wastewater onto grass-covered, gentle slopes with impermeable surface soils. As water flows over the grass-covered soil surface, contaminants are removed, and the water is collected at the bottom of the slope for reuse.

Oxidation: The loss of electrons from one substance, which causes the substance to become more positively charged.

Oxidation ditch: A variation of the activated sludge treatment process that takes place in an oval channel with aeration provided by various types of mechanical devices that move around the channel.

Oxygen demand: The need for molecular oxygen to meet the needs of biological and chemical processes in water. Even though very little oxygen will dissolve in water, it is extremely important in biological and chemical processes.

Ozonation: A disinfection process in which ozone is generated and added to wastewater effluent to kill pathogenic organisms.

Part 503 rules: Federal rules established in 1993 by the U.S. Environmental Protection Agency that address how wastewater biosolids can be applied to land, how they can be disposed, how they must be stabilized, and what the requirements are for incinerators that burn biosolids

Particle size: The diameter, in millimeters, of suspended sediment or bed material. Particle-size classifications are:

  1. Clay—0.00024-0.004 millimeters (mm)
  2. Silt—0.004-0.062 mm
  3. Sand—0.062-2.0 mm
  4. Gravel—2.0-64.0 mm

Parts per billion (ppb): The number of “parts” by weight of a substance per billion parts of water. Used to measure extremely small concentrations.

Parts per million (ppm): The number of “parts” by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations.

Pathogens: Microorganisms that can cause disease in other organisms or in humans, animals and plants. They may be bacteria, viruses, or parasites and are found in sewage in runoff from animal farms or rural areas populated with domestic and/or wild animals, and in water used for swimming. Fish and shellfish contaminated by pathogens, or the contaminated water itself, can cause serious illnesses.

Payable: The amount of money a system owes its vendors, energy providers, etc.

pCi/L (Picocuries per liter): A measure of radioactivity.

Peak flow: The maximum instantaneous discharge of a stream or river at a given location. It usually occurs at or near the time of maximum stage.

Peat filter: A type of alternative or advanced onsite wastewater treatment system. Peat filters involve the application of septic tank effluent to peat fibers housed in impermeable containers. As the effluent trickles through the peat, additional treatment is provided by microorganisms attached to the peat surface. The containers include an underdrain that collects the treated liquid, which is then dispersed, usually to a soil-absorption system.

Per capita use: The average amount of water used per person during a standard time period, generally per day.

Perched aquifer: An aquifer containing unconfined (unpressurized) ground water held above a lower body of ground water by an unsaturated zone; often a result of clay lenses in the soil strata.

Percolation: Water that moves through the soil at a depth below the root zone.

Permeability: The degree to which soils and rock are interconnected; depends upon size and shape of pores, size and shape of interconnections and their extent; a measure of the ease with which water penetrates or passes through soil.

Pesticide: A chemical substance used to kill or control pests such as weeds, insects, fungus, mites, algae, rodents, and other undesirable agents.

pH: An expression of the intensity of the basic or acid condition of a liquid. Mathematically, pH is the logarithm (base 10) of the reciprocal of the hydrogen ion concentration, [H+].

pH = log (1/[H+])

The pH may range from 0 to 14, where 0 is most acid, 14 most basic, and 7 neutral. Natural waters usually have a pH between 6.5 and 8.5.

Phosphorus: Too much nitrogen and phosphorus in water—known as nutrient pollution—cause significant increases in algae, which harms water quality, food resources and habitats, and decreases the oxygen that fish and other aquatic life need to survive.

PO4: Phosphate

Point of entry (POE): A treatment system for a house or a building at the point where the water line enters the house or building.

Point of use (POU): Treatment (of water) at the point-of-use, such as a kitchen sink.

Point source: A discrete conveyance, such as a pipe or a ditch, through which pollutants are discharged to U.S. waters (like rivers, lakes or oceans). The Clean Water Act authorizes the National Pollutant Discharge Elimination System (NPDES) permit program to regulate point sources.

Point-source pollution: Pollution of water from one place in a concentrated manner that is easy to identify.  An example is a leaking underground storage tank or discharge pipe from a sewage treatment plant.

Policy: A formal, written document outlining the ways a business intends to conduct its affairs and act in specific circumstances.

Pollutant: Generally, any substance introduced into the environment that adversely affects the usefulness of a resource.

Pollution plume: An area of a stream or aquifer containing degraded water resulting from migration of a pollutant.

Polyaluminum chloride: A polymer coagulant used to clump the dirt particles together for the coagulation and flocculation process (see also alum).

Polychlorinated biphenyls (PCBs): A group of synthetic, toxic industrial chemical compounds once used in making paint and electrical transformers, which are chemically inert and not biodegradable. PCBs were frequently found in industrial wastes and subsequently found their way into surface and ground waters. As a result of their persistence, they tend to accumulate in the environment. In terms of streams and rivers, PCBs are drawn to sediment, to which they attach and can remain virtually indefinitely. Although virtually banned in 1979 with the passage of the Toxic Substances Control Act, they continue to appear in the flesh of fish and other animals.

Poly vinyl chloride (PVC): A material used to make pipes for waterlines.

Porosity: The degree to which the total volume of soil, gravel, sediment or rock is permeated with pores or cavities through which fluids (including air) can move.

Potable: Water of sufficiently high quality that can be consumed or used without risk of immediate or long-term harm.

Potassium permanganate: A chemical compound used for oxidation, taste and odor control, and disinfection.

ppb (parts per billion): A measure of concentration of a dissolved substance, analogous to μg/L.

ppm (parts per million): A measure of concentration of a dissolved substance, analogous to mg/L.

Precipitation: Moisture falling from the atmosphere in the form of rain, snow, sleet or hail.

Prepaid assets: Expenses paid in advance, such as insurance policies for which the annual premiums are paid upfront.

Pressure sewer: A system of pipes in which the wastewater is transported under pressure supplied by pumps.

Preventative maintenance: Maintenance performed according to a schedule, done to avoid emergency repairs and keep equipment in running order.

Primacy: The responsibility for ensuring that a law is implemented and the authority to enforce a law and related regulations.

Primacy agency: A body, often a state agency, that has the first or main responsibility for administrating and enforcing regulations.

Primary clarifier: A tank used in the primary treatment process that provides a non-turbulent environment allowing heavier solids to settle out and floatable materials to come to the surface where they may be separated. Also referred to as a primary sedimentation tank.

Primary contaminants: Also known as the National Primary Drinking Water Standards. Currently there are 87 primary and 15 secondary contaminants.

Primary sludge: Sludge produced in the primary wastewater treatment process

Primary treatment: The step in the treatment of water or wastewater designed to remove large contaminants from the water by gravity or other means.

Primary wastewater treatment: The first stage of the wastewater-treatment process in which mechanical methods, such as filters and scrapers, are used to remove pollutants. Solid material in sewage also settles out in this process.

Principal aquifer: The aquifer in a given area that is the important economic source of water to wells for drinking, irrigation, etc.

Prior appropriation: A doctrine of water law that allocates the right to use water on a first-come, first-served basis.

Property, plant and equipment: See definition of fixed assets.

Protective programs: The EPA designation refers to planning for emergencies, whether they are natural, human-caused or epidemiologic in nature.

Protozoa: Single-cell organisms that move by using tails (flagella), hairs (cilia) or foot-like structures (pseudopods). Giardia lamblia is a flagellate protozoa.

Proxy voting: Designating another board member to vote in place of an absent member in the same manner the absent member would vote.

Public notification: A written notification of drinking water violations or other situations that may threaten human health, distributed by broadcast, mail or other means.

Public water systems (PWS): A system for the provision to the public of piped water for human consumption, if such system has at least 15 service connections or regularly serves an average of at least 25 individuals at least 60 days out of the year. Public water systems include: 1) any collection, treatment, storage, and distribution facilities under control of the operator of such system and used primarily in connection with such system, and 2) any collection or pretreatment storage facilities not under such control which are used primarily in connection with such system. A public water system is either a community water system or a non-community water system.

Qualification test: A set of tests and verifications performed to validate the conformance of water treatment equipment to a specific standard.

Quantification: The measurement of the quantity of a substance.

Quench: To cool a material suddenly or halt a process or reaction abruptly.

Rapid infiltration: A method of final treatment and dispersal of wastewater effluent by spreading the effluent over highly permeable soils, such as sand and loam.

Raw water: Untreated water (i.e., not safe for human consumption).

RD (Rural Development): A part (an agency) of the U.S. Department of Agriculture. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD is the Rural Utilities Service (RUS), from which many small, rural water systems receive loans and grants.

Real water loss: Actual water lost between treatment and delivery to customers, including water that leaks from distribution lines or valves and water that is stolen from hydrants or after the meter.

Receivable: The amount of money a customer owes the system.

Receiving waters: All distinct bodies of water that receive runoff or wastewater discharges, such as streams, rivers, ponds, lakes, and estuaries.

Recharge zones: The area of land that allows water to replenish an aquifer. This process occurs naturally when rainfall filters down through the soil or rock into an aquifer, usually in the higher-gradient section overlying the aquifer; artificial recharge is through injection wells or by spreading water over ground water reservoirs reservoir for any given area.

Record: All books, papers, maps, photographs, machine-readable materials, or other documentary materials, regardless of physical form or characteristics, made or received by the water or wastewater system in connection with the transaction of public business and preserved or appropriate for preservation by that system as evidence of the organization, functions, policies, decisions, procedures, operations, or other activities or because of the informational value of data in them.

Reduced-pressure backflow preventer: A device used to help prevent backflow into the distribution system.

Revenue: Income that has been earned by the system, including water sales, late charges, service charges, and the like.

Reverse osmosis: Treatment that uses a very fine molecular sieve that permits water to pass through but not contaminants. Useful for nitrate removal.

Riparian rights: A doctrine of state water law under which a land owner is entitled to use the water on or bordering his property, including the right to prevent diversion or misuse of upstream waters. Riparian land is land that borders on surface water.

Root zone: The depth of soil penetrated by crop roots.

Rotating biological contactor (RBC): An attached growth wastewater treatment process involving large, closely spaced plastic discs mounted on a revolving horizontal shaft. The discs alternately move through the wastewater and the air, developing a biological growth on the surface of the discs that removes organic material in the wastewater.

Rotavirus: The most common cause of severe diarrhea among infants and young children and one of several viruses that cause infections often called stomach flu (despite having no relation to influenza). It is a genus of double-stranded RNA virus in the family Reoviridae. By the age of five, nearly every child in the world has been infected with rotavirus at least once.

Runoff: The flow of water from the land to oceans or interior basins by overland flow and stream channels.

Rural Development (RD): A part (an agency) of the U.S. Department of Agriculture. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD are the Rural Utilities Programs, from which many small, rural water systems receive loans and grants.

Rural Utilities Service (RUS): A program area within Rural Development (RD), which, in turn, is a part (an agency) of the U.S. Department of Agriculture. Many small, rural water systems receive loans and grants from the Rural Utilities Service.

RUS (Rural Utilities Service): A program area within Rural Development (RD), which, in turn, is a part (an agency) of the U.S. Department of Agriculture. Many small, rural water systems receive loans and grants from the Rural Utilities Service.

Safe Drinking Water Act (SDWA): The federal legislation that defines a public water system, sets the standards for state regulation of public water systems, and authorizes funding for certain water systems. The legislation was enacted in 1974 and amended in 1986 and 1996 and requires many actions to protect drinking water and its sources: rivers, lakes, reservoirs, springs and groundwater wells. The SDWA does not regulate private wells that serve fewer than 25 individuals. The SDWA authorizes the U.S. Environmental Protection Agency (EPA) to set national, health-based standards for drinking water to protect against both naturally occurring and human-made contaminants that may be found in drinking water. EPA, states, and water systems then work together to make sure that these standards are met.

Salinity: The concentration of dissolved salts in water.

Salt-water intrusion:  The process by which an aquifer is over drafted, creating a flow imbalance within an area that results in salt water encroaching into the fresh-water supply.

Sand filter: A type of alternative or advanced onsite wastewater treatment unit. It involves the intermittent application of septic tank effluent to sand that is enclosed in a container, usually 2 or 3 feet in depth. The effluent receives further treatment as it trickles through the sand and is collected in an underdrain for further treatment or dispersal. Sand filters are classified as single-pass, in which the effluent is applied to the filter once, or recirculating, in which a portion of the liquid collected in the underdrain is recycled back to be applied to the filter again.

Sanitary sewer: A sewer that transports only wastewaters (from domestic residences and/or industries) to a wastewater treatment plant.

Sanitary Survey: A periodic inspection of a water system’s facilities, operations and recordkeeping.  The inspections identify conditions that may present a sanitary or public health risk.  The federal Safe Drinking Water Act (SDWA) calls for a routine sanitary survey of all public drinking water systems once every five years, except for community surface water systems, which are to be surveyed once every three years.

SCADA:  An acronym Supervisory Control And Data Acquisition, which refers to computer systems that monitor and control industrial, infrastructure, or facility-based processes.

Schmutzdecke: A biofilm or gelatinous layer that forms on top of a slow sand filter media and contains microorganisms that trap and breakdown algae, microorganisms, and other organic matter before the water reaches the filter medium.

Screen: A device used to remove large objects such as rags, plastics bottles, bricks, solids, and toy action figures from the waste stream entering the treatment plant and damaging valves or pumps.

Secondary aquifer: Any aquifer that is not the main source of water to wells in a given area; includes shallow and perched aquifers.

Secondary clarifier: A clarifier following a secondary treatment process, designed for removal of suspended matter by gravity.

Secondary maximum contaminant limit (SMCL): Established only as a guideline to assist public water systems in managaing their drinking water for aesthetic considerations, such as taste, color and odor.

Secondary sludge: Sludge produced during the secondary treatment process.

Secondary treatment: The portion of wastewater treatment that removes the biological waste component from the influent wastewater.

Septage: The residual solids in septic tanks or other onsite wastewater treatment systems that must be removed periodically for disposal

Septic system: An onsite system designed to treat and dispose of domestic sewage; a typical septic system consists of a tank that receives wastes from a residence or business and a system of tile lines or a pit for disposal of the liquid effluent that remains after decomposition of the solids by bacteria in the tank.

Septic tank: One of the primary components of a septic system in which heavier solids are allowed to settle out and lighter materials form a floating layer. An outlet is configured such that only relatively clarified liquid flows to the drainfield or soil-absorption system for final treatment and dispersal.

Septic tank effluent pump (STEP) sewer: A type of pressure sewer that uses a septic tank to eliminate most solids and a pump to push the liquid effluent through the sewers. Because there are very little solids in the sewage, very narrow pipes can be used.

Sequencing batch reactor (SBR): A variation of the activated sludge process in which all treatment processes occur in one tank that is filled with wastewater and drawn down to discharge after treatment is complete.

Settleable solids: Solids that are heavier than water and settle out of water by gravity

Sewer: An underground system of conduits (pipes and/or tunnels) that collect and transport wastewaters and/or runoff.  Gravity sewers carry free-flowing water and wastes; pressurized sewers carry pumped wastewaters under pressure.

Short-term investments: Investments with maturity dates greater than 90 days from the balance sheet date, but shorter than one year from the balance sheet date.

Sludge: The settleable solids separated from water during processing (also called biosolids).

Sludge drying bed: A constructed bed of sand used to dewater sludge. An underdrain is used to collect the separated water.

Softening: Water having a low concentration of calcium and magnesium ions. According to U.S. Geological Survey guidelines, soft water is water having a hardness of 60 milligrams per liter or less.

Soil-absorption system (SAS): The part of a septic system in which the clarified liquid effluent is dispersed into soil for final treatment and disposal. The SAS, also referred to as a drainfield or leachfield, is typically made up of a series of trenches or a bed lined with gravel or coarse sand. The effluent is dispersed through a network of perforated pipes or drain tiles.

Sole-source aquifer: An aquifer that supplies 50 percent or more of the drinking water of an area.

Solids retention time (SRT): The average amount of time that sludge remains in an activated sludge treatment process. It is a critical part of the treatment process that an operator watches because it determines how well the process works.

Sorb: To take up and hold either by absorption or adsorption.

Source water protection plan: A plan to prevent, reduce or eliminate known and potential sources of contamination within a drinking water source protection area.

Spring: A place where ground water naturally comes to the surface resulting from the watertable meeting the land surface.

Stabilization: Any process used to produce a final biosolids product that has little or no potential to further decompose and create undesirable odors and that is free of pathogens.

Standard operating procedures (SOPs): A set of written instructions that document a routine or repetitive activity followed by an organization. The development and use of SOPs are an integral part of a successful quality system as it provides individuals with the information to perform a job properly, and facilitates consistency in the quality and integrity of a product or end-result.

Statement of activities: See definition of income statement.

Statement of financial position: See definition of balance sheet.

Storm sewer: A sewer that collects and transports surface runoff to a discharge point (infiltration basin, receiving stream, or treatment plant).

Supplier of water: Any person who owns or operates a public water system.

Surface water: All water naturally open to the atmosphere (rivers, lakes. reservoirs, streams, impoundments, seas, estuaries, etc.) and all springs, wells, or other collectors which are directly influenced by surface water (groundwater under the direct influence of surface water, or GWUDI).

Surface Water Treatment Rule: The federal regulation designed to improve public health protection through controlling microbial contaminants, particularly viruses, Giardia, and Cryptosporidia (see also Interim Enhanced Surface Water Treatment Rule).

Suspended growth process: A wastewater treatment process in which the microorganisms providing the treatment are maintained in suspension in the wastewater

Suspended solids: Solids that either float on the surface or are suspended in water or other liquids, and which are largely removable by laboratory filtering.

Sustainable: A water or wastewater system’s ability to provide safe, high-quality drinking water to customers while meeting regulatory responsibilities.

Synthetic organic compounds (SOCs): Human-made organic compounds created through industrial synthesis. Some SOCs evaporate easily (are volatile) whereas others tend to remain dissolved in water with little or no evaporation.

Tertiary treatment: Any physical, chemical or biological wastewater treatment process that is used to improve the quality of secondary effluent.

Thickening: Any process to decrease the volume of sludge by removal of some of the liquid portion

Total assets: The sum of current assets, fixed assets, and long-term assets.

Total Coliform Rule (TCR): The federal regulation for measuring the presence of coliform bacteria in drinking water. (Coliform bacteria are used as an indicator of microbial contaminantion.) The rule also details the type and frequency of testing that water systems must undertake. The rule applies to all public water systems.

Total debt service: The total annual payment paid during the year by the system on borrowed funds, including principal, interest, and any reserve deposits if they were required.

Total dissolved solids: The total amount in milligrams of solid material dissolved in one liter of water (mg/l.).

Total organic carbons: Materials that come from natural decaying plant material such as leaves and other vegetation.

Total maximum daily load (TMDL): A calculation of the maximum amount of a pollutant that a body of water can receive and still safely meet water quality standards.

Total suspended solids (TSS): A measure of the suspended matter in a sample of water or wastewater. It is measured by passing the sample through a filter, evaporating the water, and weighing the dried residue that was retained on the surface of the filter.

Transient non-community water system (TNCWS): A public water system that serves at least 25 different people for 60 days or more each year. Examples include campgrounds, rest stops, parks, or restaurants. Different individuals use the water from one day to the next, and they do not live at this facility.

Transmissivity: The measure of the ability of an aquifer to transmit water.

Treated wastewater: Wastewater that has been subjected to one or more physical, chemical, and biological processes to reduce its concentration of pollution or health hazard.

Treatment technique: An enforceable procedure or level of technological performance which water systems must follow to ensure control of a contaminant (specifically for microorganisms, turbidity, copper, lead, acrylamide, and epichlorohydrin).

Trickling filter: An attached growth process that involves a tank, usually filled with a bed of rocks, stones, or synthetic media, to support bacterial growth used to treat wastewater.

Trihalomethanes (THMs): A group of four chemicals that are formed along with other disinfection byproducts  when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic  matter in water. The trihalomethanes  are chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Because of their carcinogenic potential and other possible health effects, these compounds are regulated by the U.S. Environmental Protection Agency.

TT (treatment technique): A required process intended to reduce the level of a contaminant in drinking water.

Turbidity: The cloudy appearance of water caused by the presence of suspended and colloidal matter. In the waterworks field, a turbidity measurement is used to indicate the clarity of water. Technically, turbidity is an optical property of the water based on the amount of light reflected by suspended particles. Turbidity cannot be directly equated to suspended solids because white particles reflect more light than dark-colored particles and many small particles will reflect more light than an equivalent large particle.

Ultraviolet (UV) disinfection: A disinfection process in which wastewater is exposed to UV light to kill or deactivate potential microbial pathogens

Unconfined aquifer: An aquifer containing water that is not under pressure; the water level in a well is the same as the water table outside the well.

Underground storage tank (UST): A tank system, including its piping, that has at least 10% of its volume underground.

USDA: A cabinet-level department of the executive branch of the federal government. Within the U.S. Department of Agriculture is Rural Development (RD), one of its agencies. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD is the Rural Utilities Service (RUS), from which many small, rural water systems receive loans and grants. Also called the Agriculture Department, the Department of Agriculture or U.S. Department of Agriculture.

U.S. Department of Agriculture: A cabinet-level department of the executive branch of the federal government. Within the U.S. Department of Agriculture is Rural Development (RD), one of its agencies. RD’s website says it “helps rural areas to develop and grow by offering Federal assistance that improves quality of life. RD targets communities in need and then empowers them with financial and technical resources.” Within RD is the Rural Utilities Service (RUS), from which many small, rural water systems receive loans and grants. Also called the Agriculture Department, the Department of Agriculture or USDA.

U.S. Environmental Protection Agency: The federal agency responsible for researching and setting national standards for a variety of environmental programs. The EPA works to develop and enforce regulations that implement environmental laws enacted by congress. Its website is Also known as the U.S. EPA, the EPA, or the Environmental Protection Agency.

U.S. EPA: The federal agency responsible for researching and setting national standards for a variety of environmental programs. The EPA works to develop and enforce regulations that implement environmental laws enacted by congress. Its website Also known as the U.S. Environmental Protection Agency, the EPA, or the Environmental Protection Agency.

User Fee: A fee which is collected only from those persons who use a particular service, as opposed to one collected from the public in general. User fees generally vary in proportion to the degree of use of the service.

Vacuum sewer: An alternative sewer system that uses a vacuum (created by a central vacuum station and maintained in the lines) to draw and transport wastewater through the system to a final treatment unit

Variance: A State with primacy may relieve a public water system from a requirement respecting an MCL by granting a variance if certain conditions exist.  These are: 1) the system cannot meet the MCL in spite of the application of best available treatment technology, treatment techniques or other means (taking costs into consideration), due to the characteristics of the raw water sources which are reasonably available to the system, and 2) the variance will not result in an unreasonable public health risk.  A system may also be granted a variance from a specified treatment technique if it can show that, due to the nature of the system’s raw water source, such treatment is not necessary to public health.

Vector: An insect or any living carrier (birds, rats) that transmits an infectious agent.

Virus: The smallest form of microorganisms capable of causing disease, especially those of fecal origin that is infectious to humans by waterborne transmission.

Volatile organic compound: A carbon-based substance that wastes away on exposure to the atmosphere.

Volatization: Loss of a substance through evaporation or sublimation. When manure is spread on a field, ammonia-nitrogen in the manure may volatize quickly and be lost as fertilizer unless it is incorporated into the soil.

Vulnerability Assessment: A process of determining which components of a system are vulnerable to damage or loss in an emergency, it consists of four steps: inventory critical system components, identify vulnerabilities, identify actions to address vulnerabilities, and prioritize actions.  To prioritize actions, system managers and operators must understand the relative risks to public health of the vulnerabilities identified.

WARN: Water and Wastewater Agency Response Networks, a voluntary network of utilities that help each other respond to and recover from emergencies.

Wastewater: The used water and solids from a community (including used water from industrial processes) that flow to a treatment plant.  Storm water, surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant.

Wastewater treatment plant: A facility that receives wastewaters (and sometimes runoff) from domestic and/or industrial sources, and by a combination of physical, chemical, and biological processes reduces (treats) the wastewaters to less harmful byproducts; also known by the acronyms STP (sewage treatment plant), and POTW (publicly-owned treatment works).

Wasting: Removal of excess microorganisms from a secondary treatment system.

Water audit: A plan for tracking water from its entry to the distribution system to its exit at the point of use, to determine where system losses are occurring.

Water budget: The depth of annual precipitation to cover an area. In the U.S., it is 30 inches.

Water loss: The sum of apparent water losses and real water losses, which result in the production of non-revenue water.

Water quality-based control standards: Standards imposed when technology-based standards are not expected to provide sufficient protection for local water quality, given local water conditions and uses. States classify all state waters according to specific uses, and then set an ambient water quality standard to protect that use. Once the standard is set, the total maximum daily load (TMDL) of a particular pollutant is set at a level that will not violate the standard. The TMDL is then translated into specific numerical limits in particular permits.  States identify the uses, set the water quality standards, and determine how to allocate the TMDL among different users.

Water supplier: A person who owns or operates a public water system.

Water supply system: The collection, treatment, storage, and. distribution of potable water from source to consumer.

Watershed: The land area that drains into a stream. An area of land that contributes runoff to one specific delivery point; large watersheds may be composed of several smaller “subsheds,” each of which contributes runoff to different locations that ultimately combine at a common delivery point.

Water table: The water level of an unconfined aquifer below which the pore spaces are generally saturated.

Water table aquifer: An aquifer whose upper boundary is the water table; also known as an unconfined aquifer.

Water table well: A well whose water is supplied by a water table or confined aquifer.

Well: A bored, drilled, or driven shaft, or a dug hole, whose depth is greater than the largest surface dimension and whose purpose is to reach underground water supplies or oil, or to store or bury fluids below ground.

Wellhead Protection Plan (WHPP): The national Wellhead Protection Program was established by the Safe Drinking Water Act in 1986.  It mandated that states develop WHPPs to protect groundwater supplies from contamination.  All states except Virginia have EPA-approved WHPPs.  Most states incorporate five primary elements into their plans: delineation of the wellhead protection area (WHPA), contaminant source inventory (CSI), management of the WHPA, public education and participation, and contingency planning.  State WHPPs vary and may also include other elements such as a plan for new wells and groundwater, or monitoring within/near the WHPA.

Withdrawal: Water withdrawal from the surface and ground water sources for various human uses.

Xerophyte: A plant structurally adapted to growth in an area of limited water supply.

X-ray fluorescence: A technique used for the identification and semiquantitative analysis of solids and liquids.


Yard meter: A water service seperate from the domestic service and used only for irrigation purposes.

Yellow water: Water that is colored as a result of the presence of iron. The iron can originate either from the source water or from corrosion reactions with iron piping. Sometimes refered to as red water.

Zero-discharge water: A condition in which a discharge limit is applied to manufacturing and commercial establishments such that only normal human sanitary wastewaters may be discharged into the municipal sewage system.

Zoning: A civil process that specifies which types of land use are allowablel in specific locations.