Bannock County Groundwater


Action Level (AL)
The concentration of a contaminant, which if exceeded, triggers a treatment or other requirement that a water system must follow.
Acute Health Effect
An immediate (i.e. within hours or days) health effect that may result from exposure to certain drinking water contaminants (e.g., pathogens).
A natural underground geologic formation able to store and yield water.
Aquiclude or aquitard
An aquiclude is a layer of rock, sediment, or soil through which groundwater cannot flow. An aquitard is also a layer of rock, sediment, or soil, through which water cannot flow fast enough to be used as a water supply.
Artesian well
A well tapping a confined aquifer. Water in the well rises above the top of the aquifer under artesian pressure, but does not necessarily reach the land surface; a flowing artesian well is a well in which the water level is above the land surface.
Best management practices (BMP’s)
Structural, nonstructural, and managerial techniques recognized to be the most effective and practical means to reduce surface water and groundwater contamination while still allowing the productive use of resources.
Best Available Technology (BAT)
The water treatment(s) that the U.S. Environmental Protection Agency (EPA) certifies to be the most effective for removing a contaminant.
Chronic Health Effect
A health effect resulting from long-term exposure over many years to a drinking water contaminant at levels at or above its maximum contaminant level (MCL).
Coliform bacteria
A group of related bacteria whose presence in drinking water may indicate contamination by disease-causing microorganisms found in untreated human and animal waste.
Community Water System (CWS) (also called a Public Water System)
A water system which supplies drinking water to 25 or more of the same people year-round in their residences.
The act of meeting all local, state, and federal drinking water regulations.
Confined Aquifer
A confined aquifer (also known as artesian or pressure aquifers) exists where the groundwater is bounded between layers of impermeable substances like clay or dense rock. When tapped by a well, water in confined aquifers is forced up, sometimes above the soil surface. This is how a flowing artesian well is formed.
Any substance that when added to water or soil (including microorganisms, minerals, chemicals, radionuclides, etc.) makes it harmful to human and animal health, and unfit for consumption.
A microorganism commonly found in lakes and rivers which is highly resistant to disinfection. Cryptosporidium has caused several large outbreaks of gastrointestinal illness, with symptoms that include diarrhea, nausea, and/or stomach cramps. People with severely weakened immune systems are likely to have more severe and more persistent symptoms than healthy individuals.
A chemical (commonly chlorine, chloramine, or ozone) or physical process (e.g., ultraviolet light) that kills microorganisms such as bacteria, viruses, and protozoa.
Distribution System
A network of pipes leading from a treatment plant to customers’ plumbing systems.
Giardia lamblia
A microorganism frequently found in rivers and lakes, which, if not treated properly, may cause diarrhea, fatigue, and cramps after ingestion.
Ground Water (groundwater)
Water found in the spaces between soil particles and cracks in rocks underground (located in the saturation zone). Groundwater is a natural resource that is used for drinking, recreation, industry, and growing crops.
Health Advisory
An EPA document that provides guidance and information on contaminants that can affect human health and that may occur in drinking water, but which EPA does not currently regulate in drinking water.
Hydraulic Head
A combined measure of the elevation and the water pressure at a point in an aquifer which represents the total energy of the water; since ground water moves in the direction of lower hydraulic head (i.e. toward lower energy), and hydraulic head is a measure of water pressure, ground water can and often does flow ‘uphill’.
Inorganic Contaminants
Mineral-based compounds such as metals, nitrates, and asbestos. These contaminants are naturally-occurring in some water, but can also get into water through farming, chemical manufacturing, and other human activities. EPA has set legal limits on 15 inorganic contaminants.
Maximum Contaminant Level (MCL)
Designation given by the U.S. Environmental Protection Agency (EPA) to drinking water standards under the Safe Drinking Water Act. A MCL is the greatest amount of a contaminant allowed in drinking water without causing a risk to human health.
Maximum Contaminant Level Goal (MCLG)
The level of a contaminant at (and below) which there is no known or expected risk to health. MCLG’s allow for a margin of safety, however, this goal is not always economically or technologically feasible, and is not legally enforceable.
Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when consumed in drinking water. Also known as microbes.
Million fibers per liter (MFL)
Measure of the presence of asbestos fibers that are longer than 10 micrometers.
Millirems per year (mrem/yr)
Measure of radiation absorbed by the body.
Sampling and analysis of ground water that water systems must perform for the purpose of detecting and measuring contaminants.
Nephelometric Turbidity Unit (NTU)
The unit of measure for the clarity of water. Turbidity in excess of 5 NTU is just noticeable to the average person.
Non-Detects (ND)
The result of a laboratory analysis in which a contaminant is not detected within the laboratory method detection limits.
Non-Transient, Non-Community Water System
A water system which supplies water to 25 or more of the same people at least six months per year in places other than their residences. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.
Organic Contaminants
Carbon-based chemicals, such as solvents and pesticides, which can get into water through runoff from cropland or discharge from factories. EPA has set legal limits on 56 organic contaminants.
Parts per million (ppm), or milligrams per liter (mg/l)
Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid. One ppm is comparable to one drop of gasoline in a tankful of gas (full-size car) or one penny in $10,000.
Parts per billion (ppb), or micrograms per liter (µg/l)
Number of parts of a chemical found in one billion parts of a particular gas, liquid, or solid. One ppb is comparable to one kernel of corn in a filled, 45-foot silo, 16 feet in diameter or one penny in $10,000,000.
Parts per trillion (ppt), or nanograms per liter (nanograms/l)
Number of parts of a chemical found in one trillion parts of a particular gas, liquid, or solid. One ppt is comparable to one minute in 2,000,000 years or one penny in $10,000,000,000.
A disease-causing microorganism.
Perched aquifer
A type of unconfined aquifer that sits above another unconfined aquifer because water infiltrating from the surface is trapped or ‘perched’ on a shallow aquitard.
Capable of transmitting water (porous rock, sediment, or soil); the rate at which water moves through rocks or soil.
Picocuries per liter (pCi/L)
The amount of radioactivity in a liter (approximately one quart) of liquid substance, such as water.
Pore spaces
Openings between geologic materials found underground. Also referred to as void spaces or interstices. Pore spaces include spaces between grains, fractures, vesicles, and voids formed by dissolution.
The amount of water held per volume of aquifer material; this is expressed as a percentage e.g. 25% means that one cubic foot of aquifer holds 0.25 cubic feet of water. If all the porosity is filled with water, the rock is termed water-saturated.
Primacy State
A State that has the responsibility and authority to administer EPA’s drinking water regulations within its borders. The State must have rules at least as stringent as EPA’s.
Public Notification
An advisory that EPA requires a water system to distribute to affected consumers when the system has violated MCLs or other regulations. The notice advises consumers what precautions, if any, they should take to protect their health.
Public Water System (PWS)
Any water system that regularly provides water to at least 25 people for at least 60 days per year, or has at least 15 service connections.
Any man-made or natural element that emits radiation and that may cause cancer after many years of exposure, such as by drinking contaminated water.
Raw Water
Water in its natural state, prior to any treatment for drinking.
Sanitary Survey
An on-site review of the water sources, facilities, equipment, operation, and maintenance of a public water system for the purpose of evaluating the adequacy of the facilities for producing and distributing safe drinking water.
The condition wherein the pore spaces in a solid (such as rock) are completely filled with liquid (such as water).
Saturated zone
The portion below the earth’s surface that is saturated with water is called the zone of saturation. The upper surface of this zone, open to atmospheric pressure, is known as the water table.
Secondary Drinking Water Standards
Non-enforceable federal guidelines regarding cosmetic effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, odor, or color) of drinking water.
Sole Source Aquifer
An aquifer that supplies 50 percent or more of the drinking water of an area.
Source Water
Water in its natural state, prior to any treatment for drinking. The area delineated by a state for a Public Water Supply as the source of drinking water, whether the source is ground water or surface water or both.
Surface Water
Water above the surface of the land, including lakes, rivers, streams, ponds, floodwater, and runoff.
Trichloroethylene (TCE) and perchloroethylene (PCE)
Manmade chlorinated solvents used commercially as industrial degreasers, spot removers, and as dry cleaning fluids. TCE and PCE can get into drinking water aquifers when they are improperly disposed of and then leach into the ground. Chronic TCE or PCE exposure through inhalation of vapors or through ingestion of contaminated drinking water can cause damage to the liver, the kidneys and the central nervous system. It may also lead to increased risk of cancer. The MCLs for both TCE and PCE are 5.0ppb (5 grams per billion grams of water).
Total Maximum Daily Load (TMDL)
A legal determination of the total amount of a particular pollutant that can be discharged into a water body in one day. This sets the limit on total pollution a water body can receive from all possible sources. TMDLs are established by the Environmental Protection Agency as well as the Department of Environmental Quality. TMDLs are used to set the limits on how much of a particular pollutant each generating source (such as a factory) may discharge.
Transient, Non-Community Water System
A public water system which supplies water to 25 or more of the same people at least six months per year in places other than their residences. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.
Treatment Technique (TT)
A required process intended to reduce the level of a contaminant in drinking water.
The cloudy appearance of water caused by the presence of tiny particles of silt or organic matter. High levels of turbidity may interfere with proper water treatment and monitoring.
Unconfined aquifer
An aquifer in which the water table is at or near atmosphere pressure and is the upper boundary of the aquifer. Because the aquifer is not under pressure the water level in a well is the same as the water table outside the well.
Variances & Exemptions (V&E)
State or EPA permission not to meet a certain drinking water standard. The water system must prove that: (1) it cannot meet a MCL, even while using the best available treatment method, because of the characteristics of the raw water, and (2) the variance will not create an unreasonable risk to public health. The State or EPA must review, and allow public comment on, a variance every three years. States can also grant variances to water systems that serve small populations and which prove that they are unable to afford the required treatment, an alternative water source, or otherwise comply with the standard.
A failure to meet any local, state, or federal drinking water regulation.
Vulnerability Assessment
An evaluation of drinking water source quality and its vulnerability to contamination by pathogens and toxic chemicals.
Water Sample
Water that is analyzed for the presence of EPA-regulated drinking water contaminants. Depending on the regulation, EPA requires water systems and states to take samples from source water, from water leaving the treatment facility, or from the taps of selected consumers.
Water table
The top of an unconfined aquifer; indicates the level below which soil and rock are saturated with water. The upper surface of the saturation zone.
The land area from which surface runoff drains into a stream, channel, lake, reservoir, or other body of water; also called a drainage basin.
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 to inject, extract or monitor water.
Well field
An area in which productive wells are drilled.
Wellhead Protection Area (WHPA)
The area surrounding a drinking water well or well field which is protected to prevent contamination of the well(s).
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