5 Colo. Code Regs. § 1002-42.23
The provisions of sections 25-8-202; 25-8-203; and 25-8-204 C.R.S. provide the specific statutory authority for adoption of these regulatory provisions. The Commission has also adopted, in compliance with section 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
As a result of this hearing, the Commission applied the classification of limited quality and use to the ground water contained with the Pennsylvanian-Permian aged Weber Formation and the Late Triassic-Early Jurassic aged Navajo Sandstone 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 144 square miles in northwest Rio Blanco County, Colorado.
Within the specified area the ground water in the Weber Formation is brought to the ground surface of "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 formation from which it comes by injection into wells. In addition, a small percentage of the Weber produced water is injected into the Navajo Sandstone.
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. In addition, makeup water for a secondary recovery waterflood project has also been obtained from the Dakota, Entrada, and Navajo formations and the White River. A tertiary recovery carbon dioxide (CO2) project has been initiated to help recover residual oil left behind by the waterflood.
Division of Water Resources data indicate that there are no public water systems, or domestic, or agricultural water wells completed in the Weber Formation or the Navajo Sandstone.
Division of Water Resources data indicate that there are 15 industrial water well permits. Thirteen of these are former oil wells or dry oil test holes that were recompleted in the Dakota, Entrada, and/or Navajo formations. Water from these wells was used as makeup water for the enhanced recovery injection projects. These wells all have been either plugged and abandoned or recompleted in the Weber Formation as oil wells.
Hydrogeologic data including produced water quality and depths of the Weber Formation and Navajo Sandstone and other 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 Weber Formation and Navajo Sandstone in the specified area is appropriate. The classification and the application of site-specific standards for organic chemicals assures consistency between implementation of the UIC Program requirements and WQCC Standards and Classifications.
The adoption of the 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 Weber Formation or the Navajo Sandstone within the 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 classifications of ground water begins with the identification of the use of the water. The ground water in the Pennsylvanian-Permian aged Weber Formation is co-produced with oil and gas and is considered a waste. The ground water in the Late Triassic-Early Jurassic aged Navajo Sandstone has been used as makeup water for the enhanced recovery projects. Within the specified area, ground water in both the Weber Formation and the Navajo Sandstone 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 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 32 water wells permitted with the Office of the State Engineer. None of these water wells are completed in the Weber Formation. Thirteen were industrial water wells completed in the Dakota, Entrada, and/or Navajo formations. These wells all have been either plugged and abandoned or recompleted in the Weber Formation as oil wells.
The Weber Formation contains or has contained naturally occurring accumulations of crude oil and natural gas, in addition to ground water in many portions of this specified area.
Although discovered in 1933, active development of the Weber Formation did not begin until 1944 when World War II petroleum demand justified the installation of facilities to produce the oil from this remote location. The Rangely Field is the largest oil field in Colorado and the sixteenth largest oil field in the United States, based upon cumulative production.
Within the specific area approximately 912 oil and gas wells or tests have been drilled to be completed in the Weber Formation.Within the specified area three injection projects have been permitted. These did not require aquifer exemptions, because the total dissolved solids (TDS) concentrations of the injection zones exceeded 10,000 milligrams per liter (mg/l). The Rangely Weber Sand Unit and the Northeast Rangely are enhanced recovery projects which use approximately 364 injection wells completed in the Weber Formation. The McLaughlin 44 is a disposal project which uses one injection well completed in the Navajo Sandstone.
Within the specified area the average depth to the Weber Formation is 6,500 feet below the ground surface (fbgs) and the average depth to the Navajo Sandstone is 5,100 fbgs.
Within the specified area the original TDS of the Weber Formation was greater than 115,000 mg/l; however, injection of makeup water with relatively lower TDS concentrations has caused an overall decrease in TDS so that today TDS concentrations ranging from 10,000 mg/l to 60,000 mg/l occur in some places. The TDS of the Navajo Sandstone is greater than 20,000 mg/l.
Consistent with this classification, the ground water quality standards in Tables 1 through 4 of the Basic Standards for Ground Water, 41.0 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 standard, 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 1002-42.23