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Water: Oil & Gas Extraction

Unconventional Extraction in the Oil and Gas Industry

Photo of a shale gas well pad

EPA is developing a proposed rule to amend the Effluent Limitations Guidelines and Standards (ELGs) for the Oil and Gas Extraction Category, (40 CFR Part 435). The proposed rule is scheduled for publication in early 2015. The proposal would address discharges of wastewater pollutants from onshore unconventional oil and gas extraction facilities to publicly-owned treatment works (POTWs). EPA continues to collect and analyze information and will examine a variety of options for these discharges.

Extraction Process

Recent advances in hydraulic fracturing and horizontal drilling have made extraction of oil and gas from unconventional resources more technologically and economically feasible than before. Hydraulic fracturing is used to extract oil and natural gas from highly impermeable rock formations, such as shale rock, by injecting fracturing fluids at high pressures to create a network of fissures in the rock formations. This process provides the oil and/or natural gas a pathway to travel to the well for extraction. Geologic pressure within the low permeability formations force a portion of these fracturing fluids back to the surface (sometimes referred to as "flowback"), along with naturally occurring formation water. These wastewaters are collectively referred to as unconventional oil and gas extraction wastewaters, or produced water.

Coalbeds are another source of unconventional gas.  Discharges from coalbed methane extraction from onshore oil and gas facilities are not subject to effluent limitations guidelines or standards under Part 435 nor are they part of the EPA’s current effort to develop additional controls for pollutants in unconventional oil and gas extraction facility discharges.

Wastewater Generated by Extraction of Unconventional Oil and Gas Resources

Unconventional oil and gas extraction wastewater may be generated in large quantities and often contains high concentrations of total dissolved solids (salts). This wastewater may also contain various organic chemicals, inorganic chemicals, metals, and naturally occurring radioactive materials (referred to as “technologically enhanced naturally occurring radioactive material” or TENORM).

Current Federal Regulatory Framework

Direct discharges from unconventional oil and gas extraction are subject to NPDES permit regulations (40 CFR Parts 122 through 125). Indirect discharges to POTWs are subject to the General Pretreatment Regulations (40 CFR Part 403).

NPDES permits must include technology based effluent limitations. For direct dischargers of unconventional oil and gas extraction wastewater from onshore oil and gas facilities, with the exception of coalbed methane, Part 435 is the source for the technology-based limitations.  Permits for onshore oil and gas facilities must include the requirements in Part 435, including a ban on the discharge of pollutants, except for wastewater that is of good enough quality for use in agricultural and wildlife propagation for those onshore facilities located in the continental United States and west of the 98th meridian. Part 435 does not currently include categorical pretreatment standards for indirect discharges to POTWs for wells located onshore (i.e., PSES or PSNS).

Additional Resources

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Additional Information

To obtain more information on the rulemaking please contact Lisa Biddle, (biddle.lisa@epa.gov) at 202-566-0350.

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