Protecting Public Health and the Environment.

Protecting Ground Water Quality

It is DEQ's job to protect the quality of ground water in Idaho. It is illegal in Idaho to cause or allow the release of a contaminant (anything that does not occur naturally or naturally occurs only in very small quantities) into the environment in a manner that it:

  • Causes a ground water quality standard to be exceeded
  • Injures a beneficial use of ground water
  • Is not in accordance with a permit, consent order, or applicable best management practice, best available method, or best practical method

One potential source of contamination of ground water is land application of treated wastewater (spent or used water from a home, community, farm, or industry). To ensure ground water is protected, DEQ requires anyone wishing to land-apply treated wastewater to obtain a wastewater reuse permit. Septic systems can also contaminate ground water. Applicants for all large soil absorption septic systems and central septic systems located in nitrate priority areas or in areas of sensitive resource aquifers must complete a nutrient-pathogen evaluation of the proposed wastewater system as part of their application for a permit. This evaluation helps predict whether effluent from the treatment system will be diluted enough to prevent ground water contamination.

What You Can Do to Protect Ground Water

Remediating contaminated ground water is time consuming and expensive. Fortunately, preventing ground water contamination does not have to be.

Properly dispose of hazardous materials.

Hazardous materials (e.g. paint, bleach, used motor oil, and cleaning products) should not be poured down the drain, put in the trash, flushed down the toilet, or dumped on the ground.

Most community wastewater treatment plants are not designed to treat hazardous substances. Thus, they can eventually be discharged into bodies of surface water and cause contamination. Landfills are generally not equipped to handle hazardous materials either. Disposing of products that contain harmful substances in your septic system can adversely affect your system's ability to treat human wastes. Once in the ground, these harmful substances can eventually contaminate the ground water. Dumping hazardous materials on the ground, where they can leach down into ground water or be carried by runoff from rainstorms into nearby surface waters, is harmful, too.

The best alternative is to limit your use of products with hazardous materials as much as possible. Even better yet, use nonhazardous products instead. Some communities host hazardous waste disposal events or have hazardous waste disposal facilities. Take advantage of these options if available.

Carefully use pesticides and fertilizers.

Many pesticides and fertilizers contain hazardous chemicals that can travel through the soil and contaminate ground water. If you must use them, do so in moderation.

Maintain your septic system.

Your septic system discharges into a drainage field where the effluent undergoes some decomposition in the soil as it works its way down to the ground water. Have your system inspected and pumped out frequently to avoid allowing solid material to leave the tank and enter the drainage field.

Also be cautious about what you put in your system. Some substances, like coffee grounds, cigarette butts, and sanitary items, do not break down easily in septic systems, and chemicals like paints, solvents, oil and pesticides will go from your septic system into the ground water.

Staff Contacts

Ground Water Bureau Chief
Ed Hagan
DEQ State Office
Water Quality Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0356

DEQ Resources

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