5 Colo. Code Regs. § 1002-41.4
Current through Register Vol. 47, No. 20, October 25, 2024
Section 5 CCR 1002-41.4 - CLASSIFICATION OF GROUNDWATERSA.Groundwater ClassificationsThe Commission hereby establishes the following classifications for groundwater:
1. Domestic Use - Quality2. Agricultural Use - Quality3. Surface Water Quality Protection4. Potentially Usable Quality5. Limited Use and QualityB.Criteria Used to Identify Classifications for GroundwaterThe groundwater classifications shall be implemented and applied to groundwaters within a specified area (as determined in accordance with section 41.4 based upon use, quality and other information demonstrating the following:
1. Groundwater within a specified area shall be classified "Domestic Use - Quality" when: a. Groundwater is used for domestic use within the specified area; or b. If groundwater is not currently used for domestic use within the specified area, the available information, including information regarding background levels, demonstrates that future domestic use of water within the specified area is reasonably probable; or c. The most recent State Engineer's well records or applicable water court decrees reveal that groundwater is permitted or decreed for domestic use within the specified area, unless other information demonstrates that domestic use is not being made of the groundwater and is not likely to be made; or d. The background levels are generally adequate to assure compliance with the Human Health Standards listed in Table 1 and TDS levels are less than 10,000 mg/l. The determination of whether or not background levels are generally adequate shall be made considering the number of parameters that meet or exceed table Values, the extent of any exceedances of table Values, the risk to the public health associated with any such exceedance, and the adequacy of the database available for such determinations.
2. Groundwater within a specified area shall be classified "Agricultural Use - Quality" when: a. Groundwater is used for agricultural use within the specified area; or b. If groundwater is not used for agricultural use within the specified area, the available information, including information regarding background levels, demonstrates that future agricultural use of water within the specified area is reasonably probable; or c. The most recent State Engineer's well records or applicable water court decrees reveal that groundwater is permitted or decreed for agricultural use within the specified area, unless other information demonstrates that agricultural use is not being made of the groundwater and is not likely to be made; or d. The background levels are generally adequate to assure compliance with the Agricultural Standards listed in Table 3 and TDS levels are less than 10,000 mg/l. The determination of whether or not background levels are generally adequate shall be made considering the number of parameters that meet or exceed table values, the extent of any exceedances of table values, the risk to crops and/or livestock associated with any such exceedance, and the adequacy of the database available for such determinations.
3. Groundwater within a specified area shall be classified "Surface Water Quality Protection" when: A proposed or existing activity does or will impact groundwaters such that water quality standards of classified surface water bodies within the specified area will be exceeded.
4. Groundwater within a specified area shall be classified "Potentially Usable Quality" when: a. TDS levels are less than 10,000 mg/l; and b. Groundwater is not used for domestic or agricultural uses within the specified area; and c. Background levels are generally not adequate to assure compliance with the Human Health and Agricultural Standards listed in Tables 1 and 3, or the information is insufficient to make such a determination; and d. Domestic or agricultural use of the groundwater can be reasonably expected in the future, considering background levels of water quality; geologic and hydrologic conditions; the degree to which any particular types of pollutants present are subject to treatment; the economic reasonableness of such treatment; the impact of treatment requirements on water quantity; whether or not pollution arises from natural sources; and other relevant factors.5. Groundwater within a specified area shall be classified "Limited Use and Quality" when: a. TDS levels are equal to or in excess of 10,000 mg/l; or b. The groundwater has been exempted under Rule 324(B) of the "Rules and Regulations, Rules of Practice and Procedure" (2 CCR 404-1) of the Oil and Gas Conservation Commission, pursuant to the Colorado Oil and Gas Conservation Act, Title 60, Article 34, C.R.S. (1982); or c. The criteria specified in sections 41.4(B)1, 2, 3, or 4 are not met.C.Specified Area1. When an activity exists or is proposed, the shape, depth, boundaries, and extent of a specified area shall be determined by considering:a. the presence, extent, and nature of existing uses of groundwater that may be affected by the activity, and the nature of reasonably expected future uses of groundwater that may be affected by the activity; and b. the nature and location of the activity and of its discharge; and c. existing groundwater quality that may be affected by the activity; and d. relevant geologic and hydrogeologic conditions, including but not limited to the presence of groundwater hydrologically connected to surface waters and recharge areas.2. In the absence of an existing or proposed activity, the shape, depth, boundaries, and extent of a specified area may be determined by considering: a. the presence, extent, and nature of existing uses of groundwater and the nature of reasonably expected future uses of groundwater; and b. existing groundwater quality; and c. relevant geologic and hydrogeologic conditions, including but not limited to the presence of groundwater hydrologically connected to surface waters and recharge areas.39 CR 11, June 10, 2016, effective 6/30/201639 CR 23, December 10, 2016, effective 12/30/201643 CR 11, June 10, 2020, effective 6/30/2020