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Ground Water Quality

The quality of Idaho’s ground water affects nearly everyone in the state. Although Idaho’s ground water quality is generally good, monitoring shows that water has been significantly degraded in specific areas. This localized degradation negatively impacts water quality and potentially threatens domestic water supplies, aquaculture, agriculture, mining, industrial, and other ground water beneficial uses. Three more commonly found constituents in Idaho’s ground water include nitrate, arsenic, and uranium.” 

  • Nitrate
  • Uranium
  • Arsenic

Nitrate is one of the most widespread ground water contaminants in Idaho. Nitrate is a compound containing nitrogen, an element which is avital component of foods and fertilizers. It’s also an essential nutrient for plant growth. Nitrate comes from a variety of sources such as plants and other organic matter that return nitrate to the soil as they decompose. Septic sewer systems, waste from animal feedlots, and nitrogen-based fertilizers also release nitrate to the environment.

Nitrate that is not used by plants can build up in and move through the soil. Precipitation, irrigation, and sandy soils allow nitrate to percolate downward into ground water.

Nitrate is just one of the potential ground water contaminants in Idaho, and the presence of nitrate may be an indicator of other potential water quality problems.

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High levels of nitrate in drinking water are associated with adverse health effects in humans and livestock and adversely affect fish and surface waters. 

People can be exposed to nitrate through food and water. In most populations, short-term exposure to even fairly large amounts of nitrate produces no immediate health effects. However, sensitive populations (e.g., babies, people in poor health, and the elderly) can be susceptible to problems from short-term nitrate exposure. Infants younger than six months are especially sensitive to nitrate poisoning, which may result in serious illness or death.

Livestock, such as cattle and sheep, also can be poisoned by high levels of nitrate (over 100 mg/L). Learn more on our Contaminants in Drinking Water web page.

As a private well owner, it is your responsibility to make sure that your water is safe to use by testing for contaminants, It is recommended that you test your water for nitrate at least once per year. A certified lab or your local health district may be able to test your well water for contaminants. Staff will tell you how to collect your water sample and the costs for the tests. Contact your local health district for information on testing your well water. 

The Idaho Ground Water Quality standard and the EPA drinking water standard for public water systems is 10 parts per million (or 10 milligrams per liter (mg/L)). The standard applies to public water systems, but private well owners should adhere to it as well.

Certified treatment devices such as reverse osmosis, distillation, and ion exchange systems can be used to remove nitrate from water. To determine the best method of removing nitrate from your well, call the NSF International Consumer Hotline at (800) 673- 8010.

DEQ developed a list of degraded ground water areas that ranks the nitrate-degraded areas (referred to as nitrate priority areas) based on the severity of the degradation. DEQ uses specific nitrate priority scoring criteria as the basis for the ranking, including population, existing water quality, water quality trends, and other factors. The data used to rank areas are updated regularly.

The Nitrate Priority Area Mapping Application is used in the most recent nitrate priority ranking was created by DEQ. The application includes nitrate results from sampling conducted by the Idaho Department of Water Resources; the U.S. Geological Survey; Idaho State Department of Agriculture; and DEQ. Capture zones delineated for source water assessments are an optional layer that may be turned on when zooming into an area on the map.

Uranium is a radioactive element (radionuclide) that occurs naturally in rock, soil, and water, usually in low concentrations. Radionuclides are unstable atoms with excess energy that emit radiation as radionuclides decay. The uranium decay sequence also includes other radionuclides of concern such as radium and radon.

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Long-term exposure to elevated levels of uranium in drinking water can result in kidney damage. Individual risk depends on many factors, including the concentration of uranium in the water, the duration and volume of consumption, and the age and health of the individual. 

The drinking water standard for public water systems is 30 parts per billion (ppb). The standard applies to public water systems, but private well owners should adhere to it as well. There is currently no Idaho ground water quality standard for uranium.

It is recommended that testing for uranium be done once every 3 to 5 years. 

NSF International-certified treatment devices such as reverse osmosis and ion exchange systems can be used to remove uranium from water. Boiling water will not remove uranium. To determine the best method of removing uranium from your water, call the NSF International Consumer Hotline at (800) 673-8010.

Arsenic is a naturally occurring element found in the earth's crust, rocks, soil, water, air, plants, and animals.

Approximately 90% of industrial arsenic in the United States is used as a wood preservative. Arsenic is also used in the manufacture of agricultural chemicals such as pesticides, paints, dyes, metals, drugs, soaps, and semiconductors.

Arsenic can be released into the environment through natural activities such as volcanic action, erosion of rocks, and forest fires, or through human activities such as pesticide application, improper disposal of arsenic-containing waste chemicals, agricultural applications, mining, and smelting.

Learn more about arsenic on our Contaminants in Drinking Water web page.

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Health effects vary depending on the person, level of exposure, and the amount of time exposed. Drinking water with high levels of arsenic over a long period may cause lung, bladder, skin, or liver cancer, in addition to non-cancer health effects:

  • Upset stomach
  • A feeling of ‘pins and needles’ in the hands and feet
  • Darkening of the skin and the appearance of corns or warts on the body

Concern over the potential effects of chronic arsenic exposure in drinking water prompted EPA to reduce the drinking water standard for arsenic from 50 parts per billion (ppb) to 10 ppb in 2006. The standard applies to public water systems, but private well owners should adhere to it as well. The Idaho Ground Water Quality Standard for arsenic is currently 50 ppb.

Arsenic testing should be done once every 3 to 5 years. Arsenic levels at 10 ppb or higher should be removed from your water as soon as possible. If your total arsenic test result is higher than 10 ppb, ask the lab to determine the level of arsenic. The amount and type of arsenic in your water will determine the type of treatment you should use. 

Arsenic levels at 10 ppb or 10 micrograms per liter of water (mg/L) or higher should be removed from your water as soon as possible. Boiling water will not remove arsenic. 

The amount and type of arsenic in your water will determine the type of treatment you should use. NSF International-certified treatment devices such as reverse osmosis, distillation, and carbon block filters can be used for removing arsenic. To decide the best method of removing arsenic from your water call the NSF International Consumer Hotline at (800) 673- 8010. Until you install a treatment device, EPA recommends using bottled water for drinking and cooking.

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