Utah classifies ground water according to Total Dissolved Solids (TDS) concentration and contaminant concentration as follows:
Class I Ground Water
CLASS I ground water is subdivided into three subclasses: Class IA, Class IB, and Class IC.
Class IA
Class IA ground water is referred to as Pristine Ground Water and is classified as such by exhibiting both of the following characteristics:
- Total dissolved solids of less than 500 mg/l and;
- No contaminant concentrations that exceed the ground water quality standard.
For facilities located above Class IA ground water, that discharge or will probably discharge to the ground water, and that are under the regulatory authority of the Ground Water Quality Protection Program, ground water quality protection levels will be established as follows:
- Total dissolved solids may not exceed the greater of 1.25 times the background or background plus two standard deviations.
- When a contaminant is not present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 0.1 times the ground water quality standard,or the limit of detection.
- When a contaminant is present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 1.25 times the background concentration, 0.25 times the ground water quality standard, or background plus two standard deviations; however, in no case will the concentration of a pollutant be allowed to exceed the ground water quality standard.
Class IB
Class IB ground water is referred to as Irreplaceable Ground Water and is a source of water for an existing community public drinking water system for which no reliable supply of comparable quality and quantity is available because of economic or institutional constraints.
For facilities located above Class IB ground water, that discharge or will probably discharge to the ground water, and that are under the regulatory authority of the Ground Water Quality Protection Program, ground water quality protection levels will be established as follows:
- Total dissolved solids may not exceed the lesser of 1.1 times the background value or 2000 mg/l.
- When a contaminant is not present in a detectable amount as a background concentration,the concentration of the pollutant may not exceed the greater of 0.1 times the ground water quality standard, or the limit of detection.
- When a contaminant is present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 1.1 times the background concentration or 0.1 times the ground water quality standard; however, in no case will the concentration of a pollutant be allowed to exceed the ground water quality standard.
Class IC
Class IC ground water is referred to as Ecologically Important Ground Water and is a source of ground water discharge important to the continued existence of an existing wildlife habitat.
Class IC ground water will be protected as a source of water for potentially affected wildlife habitat. Limits on increases of total dissolved solids and organic and inorganic chemical compounds will be determined in order to meet applicable surface water standards.
Class II Ground Water
Class II ground water is also referred to as Drinking Water Quality Ground Water and is classified as such by exhibiting both of the following characteristics:
- Total dissolved solids greater than 500 mg/l and less than 3000 mg/l and;
- No contaminant concentrations that exceed ground water quality standards.
- For facilities located above Class II ground water, that discharge or will probably discharge to the ground water, and that are under the regulatory authority of the Ground Water Quality Protection Program, ground water quality protection levels will be established as follows:
- Total dissolved solids may not exceed the greater of 1.25 times the background value or background plus two standard deviations.
- When a contaminant is not present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 0.25 times the ground water quality standard, or the limit of detection.
- When a contaminant is present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 1.25 times the background concentration, 0.25 times the ground water quality standard, or background plus two standard deviations; however, in no case will the concentration of a pollutant be allowed to exceed the ground water quality standard.
Class III Ground Water
Class III ground water is also referred to as Limited Use Ground Water and is classified as such by exhibiting one or both of the following characteristics:
- Total Dissolved Solids (TDS) greater than 3000 mg/l and less than 10,000 mg/l, or;
- One or more contaminants that exceed the ground water quality standards.
- For facilities located above CLASS III ground water, that discharge or will probably discharge to the ground water, and that are under the regulatory authority of the Ground Water Quality Protection Program, ground water quality protection levels will be established as follows:
- Total dissolved solids may not exceed the greater of 1.25 times the background value or background plus two standard deviations.
- When a contaminant is not present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 0.5 times the ground water quality standard, or the limit of detection.
- When a contaminant is present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 1.5 times the background concentration, 0.5 times the ground water quality standard, or background plus two standard deviations; however, in no case will the concentration of a pollutant be allowed to exceed the ground water quality standard.
Class IV Ground Water
Class IV ground water is also referred to as Saline Ground Water and is classified as such by containing greater than 10,000 mg/l of Total Dissolved Solids (TDS).
Protection levels for Class IV ground water will be established by the Executive Secretary to protect human health and the environment.