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Injection systems allow the deposition of waste in rock formations where the waste cannot contaminate underground sources of drinking water. The suitability of this disposal method depends upon the availability of appropriate rock formations which have the ability to accept and confine wastes in the same manner that has allowed the entrapment of naturally occurring oil and gas deposits. There are five classes of injection systems in the Federal UIC program.
Class I wells inject hazardous, industrial and municipal wastes below the lowermost formation containing an underground source of drinking water with in one-quarter mile of the well. Site selection for Class I injection systems is dependent upon geological and hydro-geological conditions. Currently only certain parts of the U.S. are suitable (mid-continent, gulf coast and Great Lakes). Class I systems are continuously monitored and tested for mechanical integrity. An important part of the determination is the evaluation of geologic stability based on the history of earthquake activity. Class I injection is not suitable for use in Oregon and are not allowed in Oregon.
Class II injection systems are associated with oil and gas production fields. There are three types: 1) saltwater disposal; 2) enhanced oil recovery (EOR); and 3) hydrocarbon storage. As oil and gas are brought to the surface they are often mixed with salt water. Only approved geological formations can receive the produced waters that are re-injected. EOR injection systems are used to increase production and prolong the life of oil and gas fields through water flooding which results in the recovery of additional product. Hydrocarbon injection is used for underground storage of crude oil and liquid hydrocarbons. Class II systems are regularly required to be tested, monitored, and mechanical integrity testing is to occur every five years. These wells are to be located below underground sources of drinking water. Currently Oregon has only a few registered Class II systems associated with the Mist Gas field and the proposed Coos Bay gas field. Class II hydrocarbon injection systems are not allowed in Oregon.
Class III injection systems are related to mineral extraction and leachate. There are two basic types: 1) solution mining of salts and sulfur and 2) in situ (in place) leaching for minerals such as uranium, gold or copper. Class III systems are not allowed in Oregon.
Class IV injection systems are used for hazardous waste disposal as defined under the Resource Conservation and Recovery Act (RCRA), and radioactive wastewater disposal into or above formations containing an underground source of drinking water within one-quarter mile of the well. These wells have been identified by EPA as a threat to human health and have been banned from use in all states in amendments to the 1986 Safe Drinking Water Act. In 1999 EPA revised this rule allowing Class IV injection systems to be rule authorized if used for bio-remediation at cleanup sites under state or federal oversight. Some pump and treat systems in use in Oregon qualify as Class IV systems. They like all other types of injection systems must be registered with DEQ and may operate with written approval in coordination with on-going remediation work by with Cleanup.
There are 30 types of injection systems ("wells") recognized by EPA ranging from simple french drains to complex geothermal power generation reinjection systems. Not all Class V systems are used for injection, some are used for recharge, de-watering, remediation and recovery. Due to this they are called injection systems in Oregon. Currently in Oregon the majority of registered and approved injection systems are Class V (75%) and are predominantly used for stormwater disposal. About 50% of the cities and counties in Oregon have injection systems instead of stormwater sewers. Class V systems must meet the Safe Drinking Water Act Standards as well as the existing state Groundwater Act requirements. Pretreatment is required in most instances prior to discharge.
EPA defines Class V systems as: 1) any bored, drilled or driven shaft; or 2) a dug hole whose depth is greater than its largest surface dimension; or 3) an improved sinkhole; or 4) a subsurface fluid distribution system (an assemblage of perforated pipes or drain tiles used to distribute fluids below the surface of the ground). EPA Region 10 is interpreting the definition to be any system, structure, or activity that is created to discharge directly into the subsurface. In most instances a dug hole or even a trench using piping will qualify if the purpose or intent is for subsurface discharge either through infiltration or injection.
Class V systems commonly found in Oregon (by their EPA Classification) includes:
Class VI wells are used for injection of carbon dioxide into subsurface rock formations for long-term storage, or geologic sequestration. Geologic sequestration refers to technologies that may be used to reduce carbon dioxide emissions to the atmosphere to help mitigate climate change.
For questions about UIC applications please contact the UIC Program via Your DEQ Online Helpdesk.
Derek SandozUIC Program Coordinator503-229-5099
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