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Q: How does hydraulic fracturing for natural gas work?
A: Hydraulic fracturing begins with construction of a well that may be drilled vertically only or paired with horizontal or directional well sections. Drilling depths for vertical wells may be from hundreds to thousands of feet below the surface with lateral section may extend 1,000 to 6,000 feet from the well. To access natural gas trapped in geologic formations such as shale, fluids (commonly water mixed with chemicals) are pumped at high pressure into the formations, opening or enlarging fractures. Next, a proppant (a material such as sand that is used to prop open the fractures) is pumped into the fractures. After the pumping pressure is released, the internal pressure of the geologic formation causes the injected fluid, or flowback, to rise to the surface where it is stored and either disposed of or recycled.
Q: Aside from water, chemical additives and proppants, what else could be found in flowback fluids?
A: Because it is injected into the earth under pressure and to great depths, hydraulic fracturing flowback fluids may also contain high levels of total dissolved solids (most notably chlorides), metals and naturally occurring radioactive materials such as uranium, thorium, radium, and lead-210. The EPA is now in the process of updating chloride water quality criteria under CWA section 304(a)(1) for use by states in establishing acceptable discharge limits. A draft criteria document is anticipated in late 2014.
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Q: How is flowback fluid normally disposed of?
A: In some areas of the United States, hydraulic fracturing flowback is commonly disposed of via underground injection, which is regulated under the Safe Drinking Water Act’s (SDWA’s) Underground Injection Control (UIC) program. Wastewater treatment facilities, both public and private, may also accept flowback fluids (and are subject to General Pretreatment Regulations at 40 CFR Part 403) although the EPA states that “many are not properly equipped to treat this type of waste.”
Except in limited situations, the Clean Water Act’s (CWA’s) effluent guidelines program for oil and gas extraction prohibits the on-site discharge of wastewater from shale gas extraction into waters of the United States. The EPA is currently working to develop standards for wastewater discharges from natural gas extraction from underground shale formations as part of the CWA 304(m) planning process and a proposed rule is expected in 2014.
Q: Since drilling for natural gas typically takes place outdoors, are these sites subject to stormwater regulations under the National Pollution Discharge Elimination System (NPDES)?
A: According to the CWA, oil and gas exploration, production, processing, or treatment operations, or transmission facilities, including associated construction activities, are not required to obtain permit coverage for stormwater discharges unless there is a reportable quantity spill or the discharge causes or contributes to a water quality violation.
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Q: Are any wastes from hydraulic fracturing regulated under the Resource Conservation and Recovery Act (RCRA)?
A: Under 40 CFR 261.4(b)(5) wastes generated during the exploration, development, and production of crude oil, natural gas, and geothermal energy are exempt from categorization as hazardous waste, however, they are still considered solid wastes under RCRA, unless they meet the exemption requirements under 40 CFR 261.4(a)(12)(i) which states in part that:
“Oil-bearing hazardous secondary materials (i.e., sludges, byproducts, or spent materials) that are generated at a petroleum refinery (SIC code 2911) and are inserted into the petroleum refining process (SIC code 2911—including, but not limited to, distillation, catalytic cracking, fractionation, gasification (as defined in 40 CFR 260.10) or thermal cracking units (i.e., cokers) unless the material is placed on the land, or speculatively accumulated before being so recycled.”
40 CFR 261.4(a)(12)(ii) provides additional clarifications about this exemption and many states also have solid waste regulations that apply to hydraulic fracturing activities and process waste streams.
Q: What is the status of the EPA’s research study concerning hydraulic fracturing and drinking water?
A: At the request of Congress, the EPA, in cooperation with multiple stakeholders including industry, is conducting a study specifically addressing hydraulic fracturing for oil and gas and its potential impacts on drinking water sources. A progress report on the study was released in 2012 and a draft report is anticipated in 2014. More about the study is available at http://www2.epa.gov/hfstudy.