5 Colo. Code Regs. § 1002-42.28
SPECIFIC STATUTORY AUTHORITY
The provisions of C.R.S. 25-8-202; 25-8-203; and 25-8-204 provide the specific statutory authority for adoption of these regulatory provisions. The Commission has adopted in compliance with C.R.S. 24-4-103(4) the following statement of basis and purpose.
STATEMENT OF BASIS AND PURPOSE
As a result of this hearing, the Commission applied the classification of limited use and quality to the ground water contained within the following specified area:
Rio Blanco County (Figure 50) The Jurassic age Morrison and Sundance Formations within a specified area of Rio Blanco County, Colorado in which extensive oil and natural gas exploration and development have occurred. The specified area includes approximately 23 square miles in Rio Blanco County, Colorado.
The adoption of this Limited Use and Quality classification by the Commission does not preclude the need for obtaining an aquifer exemption under the Underground Injection Control (UIC) program, if future applicants wish to inject fluids into portions of the subject formations within each specified area for which an aquifer exemption would be needed. That is, the adoption of this classification does not preclude the need for compliance with the specific requirements of the UIC program.
Site-specific classification of ground water begins with the identification of the use of the water within the four specified areas as follows:
Rio Blanco County (Figure 50) The ground water in the Jurassic age Morrison and Sundance Formations is co-produced with oil and gas and is considered a waste. Within the specified area, ground water in the Morrison Formation is not currently used nor can it reasonably be expected to be used in the future for domestic or agricultural purposes. The ground water is not in communication with any surface water bodies within the specified area so that the water quality standards of any classified surface water bodies are not affected by this ground water. More specific evidence of the limited use and quality of this ground water follows:
Within the specified area there are approximately 14 water wells permitted with the Office of the State Engineer. One is a shallow stock watering well, ten are shallow ground water monitoring wells installed along Wilson Creek for a contamination investigation, and three are inactive industrial water supply wells completed at depths within or exceeding the Morrison and Sundance Formations. The Division of Water Resources data indicates that there are no public water systems, or domestic, agricultural, commercial water wells completed in the Morrison and Sundance Formations within the specified area.
The Morrison and Sundance Formations contain contained naturally occurring accumulations of crude oil and natural gas, in addition to ground water this specified area. These oil and gas resources have been developed and produced since the 1930's.
Within the specified area approximately 40 oil and gas wells or tests have been drilled to or completed in the Morrison and Sundance Formations.
Within the specified area the Colorado Oil and Gas Conservation Commission (COGCC) has not granted any aquifer exemptions for UIC projects under Rule 324(B) of the Rules and Regulations, Rules of Practice and Procedure (2 CCR 404-1), pursuant to the Colorado Oil and Gas Conservation Act, Title 60, Article 34, C.R.S. (1982). Two enhanced oil production injection projects have been permitted within the specified area; however, these did not require aquifer exemptions, because the total dissolved solids (TDS) concentrations of the injection zones exceed 10,000 milligrams per liter (mg/l). These two injection projects contain a total of approximately five injection wells completed in the Morrison and Sundance Formations.
Morrison Formation
Within the specified area the Morrison Formation lies between 6,380 to 7,868 feet below the ground surface (fbgs).
Based on information available to the COGCC, within the specified area the TDS concentration of the Morrison Formation ranges from 2,342 mg/l to 11,770 mg/l with an average of 7,055 mg/l.
Hydrogeologic data including produced water quality and depths of the Morrison Formation and other COGCC data indicate that the ground water in this formation meets the criteria in Regulation 41 for classification as "Limited Use and Quality". The Commission, therefore, concluded that the application of the "Limited Use and Quality" classification to the ground water within the Morrison Formation in the specified area is appropriate. This classification and the application of site-specific standards for organic chemicals assure consistency between implementation of the UIC Program requirements and WQCC Standards and Classification
Sundance Formation
Within the specified area the Sundance Formation lies between 6,707 to 7,941 feet below the ground surface (fbgs).
Based on information available to the COGCC, within the specified area the TDS concentration of the Sundance Formation ranges from 13,277 mg/l to 22,000 mg/l with an average of 16,974 mg/l.
Hydrogeologic data including produced water quality and depths of the Morrison Formation and other COGCC data indicate that the ground water in this formation meets the criteria in Regulation 41 for classification as "Limited Use and Quality" . The Commission, therefore, concluded that the application of the "Limited Use and Quality" classification to the ground water within the Sundance Formation in the specified area is appropriate. This classification and the application of site-specific standards for organic chemicals assure consistency between implementation of the UIC Program requirements and WQCC Standards and Classification.
Consistent with the "Limited Use and Quality" classification, the ground water quality standards in Tables 1 through 4 of the Basic Standards for Ground Water, 41.0 will not apply within the specified area. Additionally, the ground water organic chemical standards included in Table A of Section 41.5.C.3 of the Basic Standards for Ground Water (5 CCR 1002-41) for benzene, toluene, ethylbenzene, xylenes, and benzo(a)pyrene will not apply to certain oil and gas producing formations within the specified areas. However, to provide some protection of the potential future use of water resources in the specified area, the Commission's action provides that the statewide standard for radionuclides, as well as the statewide organic chemical standards (other than those for benzene, toluene, ethylbenzene, xylenes, and benzo(a) pyrene) will continue to apply to this ground water.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-42.28