5 Colo. Code Regs. § 1002-42.21
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.
STATEMENT OF BASIS AND PURPOSE
The Commission has adopted, in compliance with section 24-4-103(4) C.R.S. the following statement of basis and purpose.
As a result of this hearing, the Commission applied the classification of limited quality and use to the ground waters contained within the D, J, and O Sandstones of the Lower Cretaceous Dakota Group within a specified area of northeastern Colorado in which extensive oil and natural gas exploration and development have occurred. The specified area includes the western half of Logan County, the far northeastern corner of Morgan County, and the narrow strip along the northwestern border of Washington County.
Within the specified area the ground water in the D, J, and O Sandstones is brought to the ground surface or "produced" as a by product or "waste" of the oil and gas extraction process. The vast majority of this produced water is placed back into the formations from which it comes by injection into wells.
The practice of underground injection is essential to many industries, including the petroleum industry; however, the realization that subsurface injection could contaminate ground water led to the creation of the federal Underground Injection Control (UIC) program under the provisions of the Safe Drinking Water Act (SDWA) of 1974. The purpose of this program is to ensure that injection wells are operated in such a manner that underground sources of useable water are protected.
The EPA has delegated primary regulatory authority to the Colorado Oil and Gas Conservation Commission (COGCC) for what are known as "Class II" injection wells. Class II UIC wells in Colorado are authorized to inject under the COGCC's UIC Program by permit and with requirements specified in the following COGCC rules:
RULE 324B. EXEMPT AQUIFERS
RULE 325. UNDERGROUND DISPOSAL OF WATER
400 SERIES RULE. UNIT OPERATION, ENHANCED RECOVERY PROJECTS, AND STORAGE OF LIQUID HYDROCARBONS
Within the specified area, Class II injection wells are used only for the disposal of certain exploration and production (E&P) related fluids and for enhanced oil recovery. Produced water is the fluid most typically injected for both disposal and enhanced oil recovery.
Division of Water Resources data indicate that there are no public water systems, or domestic, agricultural, or industrial water wells completed in the D, J, or O Sandstones. Hydrogeologic data including produced water quality and depths of these formations, and COGCC data indicate that the ground water in these formation is of limited use and quality. The Commission, therefore, concluded that the application of the "Limited Use and Quality" classification to the ground water within the D, J, and O Sandstones in the specified area is appropriate. This classification and the application of site-specific standards for organic chemicals assures consistency between implementation of UIC Program requirements and WQCC Standards and Classification.
The adoption of this Limited Use and Quality classification by the Commission does not preclude the need for obtaining an aquifer exemption under the UIC program, if future applicants wish to inject fluids into portions of the specified area for which an aquifer exemption has not previously been granted. 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. The ground water in the D, J, or O Sandstones of the Lower Cretaceous Dakota Group is co-produced with oil and gas and is considered a waste. It is not currently used nor can it be reasonably expected to be used in the future for domestic or agricultural purposes. It is not in communication with any surface water bodies within the specified area so that 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 water follows:
Within the specified area there are approximately 4,278 water wells permitted with the Office of the State Engineer. None of these water wells are completed in the D, J, or O Sandstones.
The D, J, and O Sandstones contain or have contained naturally occurring accumulations of crude oil, condensate, and natural gas, in addition to ground water in many portions of this specified area. These oil and gas resources have been developed and produced since at least the early 1950's and 1960's in most of the oil fields and even earlier in some of the oil fields.
Within the specified area approximately 3,000 oil and gas wells or tests have been drilled to or completed in the D, J, or O Sandstones.
Within the specified area the Colorado Oil and Gas Conservation Commission (COGCC) has granted 34 aquifer exemptions for underground injection control (UIC) projects under Rule 322(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). Seven other injection projects also have been permitted within the specified area; however, these did not require aquifer exemptions, because the total dissolved solids (TDS) concentrations of the injection zone exceeded 10,000 milligrams per liter (mg/l). Of the total 41 permitted injection projects within the specified area, 26 are still in operation.
Within the specified area the D, J, or O Sandstones lie between 4,300 and 6,000 feet below the ground surface.
Within the specified area TDS concentrations range from 4,698 mg/l to 16,197 mg/l with an average of 9,516 mg/l for the D Sandstone, from 2,612 mg/l to 13,558 mg/l with an average of 6,413 mg/l for the J Sandstone, and from 4,235 mg/l to 14,550 mg/l with an average of 6,841 mg/l for the O Sandstones.
Consistent with the classification, the ground water quality standards in Tables 1 through 4 of the Basic Standards for Ground Water, Regulation No. 41 and the statewide standards for certain specified organic chemicals associated with oil and gas production activities will not apply within the specified area. 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.
The confined and unconfined ground waters underlying the specified area for the City of Sterling wellfield have been classified Domestic Use-Quality and Agricultural Use-Quality. Technically this would include ground waters in the D, J, and O Sandstones. The specified area for the City of Sterling wellfield is within the area specified for the Colorado oil and gas fields of Logan, northern Washington, and northeastern Morgan Counties; therefore, to classify the ground waters in the D, J, and O Sandstones Limited Use and Quality, the specified area for the City of Sterling Wellfield has been revised to exclude the ground waters within the D, J, and O Sandstones.
The risk of adverse impact to the City of Sterling Wellfield from this reclassification of the D, J, and O Sandstones is considered by the Commission to be very low, because all of the water supply wells are completed in the alluvial deposits of the Platte River, or shallow bedrock including the Tertiary White River, Arikaree, or Ogallala, or the upper sandy member of the Cretaceous Pierre Shale; none are completed in the D, J, or O Sandstones. In addition, the D, J, and O Sandstone lie at a depth of approximately 4,500 to 5,000 feet below the base of the aquifers tapped by the water supply wells; therefore, it is highly unlikely that there is any significant hydrologic interaction between the shallow ground waters sources for the wellfield and the ground waters in the D, J, or O Sandstones.
PARTIES TO THE RULEMAKING HEARING July, 1997
5 CCR 1002-42.21