Effluent Guidelines

Unconventional Extraction in the Oil and Gas Industry

EPA is proposing pretreatment standards for the Oil and Gas Extraction Category (40 CFR Part 435). The regulations would address discharges of wastewater pollutants from onshore unconventional oil and gas (UOG) extraction facilities to publicly-owned treatment works (POTWs).

The public comment period closed on July 17, 2015.

  • Federal Register Notice (PDF) (24 pp, 376 K, About PDF) (April 7, 2015)
  • Support documents, including:
    • Technical Development Document
      Describes industry processes, pollutants generated, available control & treatment technologies, the technical basis and costs of the proposed rule
    • Fact Sheet
Documents related to this rulemaking can be found on EPA’s docket at regulations.gov. The Docket Number is EPA-HQ-OW-2014-0598.
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Public Hearing

EPA conducted a public hearing on the proposed rule on May 29, 2015. A transcript of the hearing has been added to the rulemaking record.


UOG extraction wastewater can be generated in large quantities and contain constituents that are potentially harmful to human health and the environment. Wastewater from UOG wells often contains high concentrations of salt content, also called total dissolved solids or TDS. The wastewater can also contain various organic chemicals, inorganic chemicals, metals, and naturally-occurring radioactive materials (also referred to as technologically enhanced naturally occurring radioactive material or TENORM). This potentially harmful wastewater creates a need for appropriate wastewater management infrastructure and practices.

Historically, operators primarily managed their wastewater via underground injection in disposal wells (where available). Where UOG wells were drilled in areas with limited underground injection wells, and/or there was a lack of wastewater management alternatives, it became more common for operators to look to public and private wastewater treatment facilities to manage their wastewater.
Because they are not typical of POTW influent wastewater, some UOG extraction wastewater constituents:
  • can be discharged, untreated, from the POTW to the receiving stream
  • can disrupt the operation of the POTW (for example, by inhibiting biological treatment)
  • can accumulate in biosolids (also called sewage sludge), limiting their use
  • can facilitate the formation of harmful disinfection by-products

Based on the information reviewed as part of this proposed rulemaking, this proposed prohibition of discharges to POTWs reflects current industry practice. Because onshore unconventional oil and gas extraction facilities have discharged to POTWs in the past, and because the potential remains that some facilities can consider discharging to POTWs in the future, EPA proposes this rule.

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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 at onshore oil and gas facilities are not subject to existing effluent limitations guidelines or standards under Part 435, nor the current proposed rule.

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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).

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Additional Resources

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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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