Groundwater Contamination

01. Releases Degrading Groundwater Quality. No person may cause or allow the release, spilling, leaking, emission, discharge, escape, leaching, or disposal of a contaminant into the environment in a manner that: (7-1-26) a. Causes a groundwater quality standard to be exceeded; (7-1-26) b. Injures a beneficial use of groundwater; or (7-1-26) c. Is not in accordance with a permit; consent order; or applicable best management practice, best available method, or best practical method. (7-1-26) 02. Measures Taken in Response to Degradation. (3-24-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.11 Department of Environmental Quality Groundwater Quality Rule Section 400 Page 14 a. Except when a point of compliance is set pursuant to Section 401, when a numerical standard is not exceeded, but degradation of groundwater quality is detected and deemed significant by the Department, the Department will take one (1) or more of the following actions: (7-1-26) i. Require a modification of regulated activities to prevent continued degradation; (3-24-22) ii. Coordinate with the appropriate agencies and responsible persons to develop and implement prevention measures for activities not regulated by the Department; (3-24-22) iii. Allow limited degradation of groundwater quality for the constituents identified in Subsection 200.01.a. if it can be demonstrated that: (7-1-26) (1) Best management practices, best available methods, or best practical methods, as appropriate for the aquifer category, are being applied; and (7-1-26) (2) The degradation is justifiable based on necessary and widespread social and economic considerations; or (3-24-22) iv. Allow degradation of groundwater quality up to the standards in Subsection 200.01.b., if it can be demonstrated that: (7-1-26) (1) Best management practices are being applied; and (3-24-22) (2) The degradation will not impair a beneficial use. (7-1-26) b. The following criteria will be considered when determining the significance of degradation: (7-1-26) i. Site specific hydrogeologic conditions; (3-24-22) ii. Water quality, including seasonal variations; (3-24-22) iii. Existing and projected future beneficial uses; (3-24-22) iv. Related public health issues; and (3-24-22) v. Whether the degradation involves a primary or secondary constituent in Section 200. (3-24-22) 03. Contamination Exceeding a Groundwater Quality Standard. The discovery of any contamination exceeding a groundwater standard that poses a threat to existing or projected future beneficial uses of groundwater requires appropriate actions, as determined by the Department, to prevent further contamination. These actions may consist of investigation and evaluation, or enforcement actions if necessary to stop further contamination or clean up existing contamination. (7-1-26) 04. Agricultural Chemicals. Agricultural chemicals found in intermittently saturated soils within the crop root zone will not be considered groundwater contaminants as long as the chemicals remain within the crop root zone, and have been applied in a manner consistent with all appropriate regulatory provisions. (7-1-26) 05. Site-Specific Groundwater Quality Levels or Points of Compliance. The Department may allow site-specific groundwater quality levels, for any aquifer category, that vary from a standard(s) in Section 200 or Section 300, or may allow site-specific points of compliance, based on consideration of effects to human health and the environment, for: (7-1-26) a. Remediation conducted under the Department’s oversight; (3-24-22) b. Permits issued by the Department; (3-24-22) IDAHO ADMINISTRATIVE CODE IDAPA 58.01.11 Department of Environmental Quality Groundwater Quality Rule Section 401 Page 15 c. Situations where the site background level varies from the groundwater quality standard; (7-1-26) d. Dissolved concentrations of secondary constituents listed in Section 200 of this rule. The Department may allow the use of dissolved concentrations for secondary constituents if the requesting person demonstrates that doing so will not adversely affect human health and the environment; or (3-24-22) e. Other situations authorized by the Department in writing. (3-24-22)