SECTION 785:45-7-4. Criteria for groundwater quality protection

(a)   Groundwaters of the state support many different beneficial uses. The criteria below do not require improvement over naturally occurring background concentrations. When naturally occurring background concentrations exceed the criterion for a given parameter, the naturally occurring background concentration may be utilized as a criterion, if suitable. If a given parameter has more than one criterion associated with it, the most stringent criteria shall apply to ensure beneficial use protection.

(b)   The following criteria apply to all groundwaters for the protection of beneficial uses except those groundwaters specifically referenced in 785:45-7-4(c).

(1)   The groundwaters of the state shall be maintained to prevent alteration of their chemical properties by harmful substances not naturally found in groundwater.

(2)   Protective measures adequate to preserve and protect background quality of the groundwater and existing and designated groundwater basin classifications shall be maintained at all times.

(3)   Protective measures shall also be sufficient to minimize the impact of pollutants on groundwater quality.

(4)   The concentration of any synthetic substance or any substance not naturally occurring in that location shall not exceed the PQL in an unpolluted groundwater sample using laboratory technology. If the concentration found in the test sample exceeds the PQL, or if other substances in the groundwater are found in concentrations greater than those found in background conditions, that groundwater shall be deemed to be polluted and corrective action may be required.

(c)   For artificial aquifer recharge and or aquifer storage and recovery activities, the criteria below and presented in Tables 1 and 2 of Appendix I shall apply to ensure the protection of beneficial uses, as specified. Artificial recharge and or aquifer storage and recovery activities shall not cause or contribute to a condition of pollution or nuisance or result in nonattainment of any applicable groundwater quality standard.

(1)   Chemical Constituents. Groundwaters shall not contain chemical constituents in concentrations that adversely affect any beneficial use. At a minimum, groundwaters with the designated beneficial uses of public water supply and domestic untreated water supply shall not contain concentrations of chemical constituents in excess of the maximum contaminant levels specified in the following provisions:

(A)   Organic Contaminants in 40 CFR 141.61(a)

(B)   Synthetic Organic Contaminants in 40 CFR 141.61(c)

(C)   Inorganic Contaminants in 40 CFR 141.62(b)

(D)   Disinfection Byproducts in 40 CFR 141.64

(E)   Disinfectants in 40 CFR 141.65(a)

(2)   Toxicity. Groundwaters shall be maintained free of toxic substances in concentrations that produce detrimental physiological responses in human, plant, animal, or aquatic life associated with any beneficial use(s). This criterion applies regardless of whether the toxicity is caused by a single substance or the interactive effect of multiple substances or the mobilization and or transformation of a substance due to changes in physiochemical properties within the aquifer. At a minimum, groundwaters with the designated beneficial uses of public water supply and domestic untreated water supply shall not exceed limits specified in Table 1 of Appendix I of this chapter.

(3)   Secondary Contaminants. At a minimum, groundwaters with the designated beneficial uses of public water supply and domestic untreated water supply shall not exceed the criteria limits presented in Table 2 of Appendix I of this chapter and consistent with 40 CFR 143.3.

(4)   Microorganisms. Groundwaters with the designated beneficial uses of public water supply and domestic untreated water supply microorganisms shall not exceed the limits specified in 40 CFR 141.63 and 40 CFR 141.70-73.

(5)   Taste and Odor. Groundwaters shall be free from taste and odor producing substances, in concentrations that cause nuisance or adversely affect any beneficial use.

(6)   Radioactivity. At a minimum, groundwaters with the designated beneficial uses of public water supply and domestic untreated water supply shall not contain concentrations of radionuclides in excess of limits specified in 40 CFR 141.66.

(7)   Geochemical and Physical Composition. The geochemical and physical composition of groundwaters shall not be altered such that mobilization of any introduced or in-situ contaminants, natural or non-natural, occurs and impairs any beneficial use.

(8)   Minerals. Increased mineralization, in comparison to existing water quality, from elements such as, but not limited to, calcium, magnesium, sodium and their associated anions shall not impair any beneficial use.

(d)   Measures to prevent noncompliance with this Section caused by any person, or activity, shall be the responsibility of each state environmental agency within their jurisdictional areas of environmental responsibility. Such measures shall be prescribed in the Water Quality Standards Implementation Plan of each such agency. When regulating activities that have the potential to contaminate groundwater from the surface, the vulnerability level of an affected hydrogeologic basin (for example, more stringent measures such as siting limitations, lagoon liners, or additional monitoring wells may be required to protect groundwater in hydrogeologic basins with High or Very High vulnerability levels) shall be considered. When regulating groundwater quality activities that have the potential to cause or contribute to impairment of a surface water beneficial use., provisions to prevent the impairment of any surface water beneficial use shall be included.

[Source: Added at 34 Ok Reg 2170, eff 9-11-17]