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17.36.331    WATER SUPPLY SYSTEMS: WATER QUALITY

(1) For non-public water supply systems, the following water quality requirements must be met:

(a) the applicant shall demonstrate that water quality is sufficient for the proposed subdivision. The reviewing authority may not approve a proposed water supply system if there is evidence that, after appropriate treatment, the concentration of any water quality constituent exceeds the human health standards in Department Circular DEQ-7, or the maximum contaminant levels established in ARM Title 17, chapter 38, subchapter 2. The necessary quality of water must be available at all times unless depleted by emergencies.

(b) the applicant shall obtain samples from wells in the proposed subdivision and shall provide analyses of the samples to the reviewing authority. If no wells exist in the proposed subdivision, the reviewing authority may accept samples from nearby water wells that are completed in the same aquifer as that proposed for the subdivision water supply. The samples may not be older than one year prior to the date of application. Water quality data must show the concentration of nitrates and nitrites and specific conductance. The reviewing authority may require testing of wells located near the proposed subdivision for additional constituents for which human health standards are listed in Department Circular DEQ-7, or in ARM Title 17, chapter 38, subchapter 2, if the reviewing authority believes that those constituents may be present in harmful concentrations. Analyses must be conducted by a laboratory certified by the Department of Public Health and Human Services for analyses of water samples for public water systems.

(i) the applicant shall provide the well log for every well from which a ground water sample is collected. If a well log is not available, the applicant shall provide information about the well depth and depth to static water level. The reviewing authority may require additional information to demonstrate that ground water quality is sufficient for the proposed subdivision;

(ii) the applicant shall accurately identify, on a topographic map or lot layout document, the location of every well from which a ground water sample is taken; and

(iii) the requirement to sample for nitrates and nitrites and specific conductance does not apply if the reviewing authority determines that information from nearby water wells, which are completed in the same aquifer as that proposed for the subdivision water supply, or a hydrogeological report confirms that the proposed water supply will be of acceptable quality.

(c) the minimum setback distances set out in Table 2 of ARM 17.36.323 must be maintained for all new and existing water sources. A drinking water supply well may not be constructed within 100 feet of a ground water mixing zone granted pursuant to ARM Title 17, chapter 30, subchapter 5.

(d) the reviewing authority may require greater than a 100-foot horizontal separation between a well and surface water if there is a potential that the well may be influenced by contaminants in the surface water. In determining the appropriate separation between a well and surface water, the reviewing authority may consider factors such as well location, well construction, aquifer material, hydraulic connection between the aquifer and watercourse, and other evidence of the potential for surface water contamination. The reviewing authority may also require that the proposed water source be tested for surface water influence in accordance with Department Circular PWS-5.

(e) wells must have unperforated casing to a minimum depth of 25 feet below ground surface unless the reviewing authority finds that, based upon geological information provided by the applicant, a lesser depth will ensure that the other requirements of this rule are satisfied. The reviewing authority may require unperforated casing to a depth greater than 25 feet if water of better chemical or microbiological quality can be obtained from a deeper zone.

(f) a surface water or ground water source under the direct influence of surface water, as described in Department Circular PWS-5, may not be used as a water source for a non-public system.

(2) Public water supply systems are subject to the requirements of Title 75, chapter 6, MCA, and rules promulgated thereunder.

History: 76-4-104, MCA; IMP, 76-4-104, MCA; NEW, 2002 MAR p. 1465, Eff. 5/17/02; AMD, 2006 MAR p. 528, Eff. 2/24/06; AMD, 2014 MAR p. 2098, Eff. 9/19/14.

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