Injection well

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As defined by the EPA, an injection well is a device that places fluid deep underground into porous rock formations, such as sandstone or limestone, or into or below the shallow soil layer. These fluids may be water, wastewater, brine (salt water), or water mixed with chemicals.[1] As of 2012, there are more than 680,000 underground waste and injection wells nationwide, and U.S. industries have injected more than 30 trillion gallons of toxic liquid deep into injection wells over the past several decades, according to ProPublica.[2]

Injection wells have a range of uses that include CO2 storage, waste disposal, enhancing oil production, mining, and preventing salt water intrusion. Widespread use of injection wells began in the 1930s to dispose of brine generated during oil production. In the 1950s, chemical companies began injecting industrial wastes into deep wells. By the 1990s, injection wells were used to dispose of fracking wastewater. They are also planned for carbon capture and storage.[1]


Structurally, a disposal well is the same as an oil or gas well: tubes of concrete and steel extend from a few hundred feet to two miles into the earth. At the bottom, the well opens into a natural rock formation, with no container. Waste seeps out, "filling tiny spaces left between the grains in the rock like the gaps between stacked marbles," according to ProPublica.[3]

Structural failures

A ProPublica review of well records, case histories, and government summaries of more than 220,000 well inspections from October 2007 to October 2010 found that structural failures inside injection wells are routine. From late 2007 to late 2010, one well integrity violation was issued for every six deep injection wells examined — more than 17,000 violations nationally. More than 7,000 wells showed signs that their walls were leaking. Records also showed wells are frequently operated in violation of safety regulations and under conditions that greatly increase the risk of fluid leakage and the threat of water contamination. ProPublica's analysis showed that, when an injection well fails, it is most often because of holes or cracks in the well structure itself.[3]

Injection and waste migration

Once wastewater is underground, there are few ways to track how far it goes, how quickly, or where it winds up, raising concerns that it may migrate upward back to the surface. The hard data that does exist comes from well inspections conducted by federal and state regulators, who can issue citations to operators for injecting illegally, for not maintaining wells, or for operating wells at unsafe pressures, yet the EPA has acknowledged that it has done very little with the data it collects.[3]

A 1987 General Accountability Office review tallied ten cases in which waste had migrated from Class 1 hazardous waste wells into underground aquifers. Two of those aquifers were considered potential drinking water sources. In 1989, the GAO reported 23 more cases in seven states where oil and gas injection wells had failed and polluted aquifers. After the findings, the federal government drafted more rules aimed at strengthening the injection program. The government outlawed certain types of wells above or near drinking water aquifers, mandating that most industrial waste be injected deeper. In response, the energy industry lobbied and won a critical change in the federal government's legal definition of waste: Since 1988, all material resulting from the oil and gas drilling process is considered non-hazardous, regardless of its content or toxicity, making it subject to less strict standards than hazardous waste (Class I wells).[3]


In 1974, Congress passed the Safe Drinking Water Act (SDWA). Part of SDWA required EPA to report back to Congress on waste disposal practices, and develop minimum federal requirements for injection practices that protect public health by preventing injection wells from contaminating underground sources of drinking water.[1]

Under the program, the EPA groups underground injection wells into five classes, with each class subject to distinct requirements and standards. Class I wells are for waste designated as hazardous.[4]

All injection must be authorized under either general rules or specific permits under the underground injection control (UIC) program. Injection well owners and operators may not site, construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity that endangers an underground source of drinking water (USDW). The purpose of the UIC requirements is to:[1]

  • Ensure that injected fluids stay within the well and the intended injection zone, or
  • Mandate that fluids that are directly or indirectly injected into a USDW do not cause a public water system to violate drinking water standards or otherwise adversely affect public health.

Since 1988, all material resulting from the oil and gas drilling process is considered non-hazardous, regardless of its content or toxicity, making it subject to less strict standards than hazardous waste (Class I wells).[3]

As of 2012 there are more than 150,000 Class 2 wells in 33 states.

Fracking process

Congress provided for exclusions to the EPA's UIC authority (SDWA § 1421(d)) to regulate hydraulic fracturing, with the most recent language added via the Energy Policy Act of 2005:[5]

"The term 'underground injection' –
(A) means the subsurface emplacement of fluids by well injection; and
(B) excludes –
(i) the underground injection of natural gas for purposes of storage; and
(ii) the underground injection of fluids or propping agents (other than diesel fuels) pursuant to hydraulic fracturing operations related to oil, gas, or geothermal production activities."

While the SDWA specifically excludes hydraulic fracturing from UIC regulation under SDWA § 1421 (d)(1), the use of diesel fuel during hydraulic fracturing is regulated by the UIC program; any service company that performs hydraulic fracturing using diesel fuel must receive prior authorization. State oil and gas agencies may have additional regulations for hydraulic fracturing.[5]

Fracking wastewater

Because of a regulatory determination by the EPA not to classify shale gas wastewater as “hazardous”, it is not required to be injected into Class I wells for hazardous waste, and is therefore often injected into Class II wells, which are subject to less stringent requirements than Class I hazardous waste wells. Either states or the federal EPA can take primacy in overseeing the program, but state programs must meet minimum federal UIC requirements to gain primacy.[4]

As of May 2012, the EPA lists over 150,000 Class II wells in its inventory. According to the U.S. Geological Survey, about 40,000 of those are disposal wells. The rest are wells where water is used to dislodge oil and gas and "enhance recovery" of the minerals.[6]

According to E&E, oil and gas producers are exempt from a federal environmental law designed to prevent industrial waste injection wells from triggering earthquakes, although in 2012 the EPA began drafting suggestions for state regulators to minimize earthquakes caused by waste injection.[7]


In 2013, the Journal of Geophysical Research paper, "Induced seismicity associated with fluid injection into a deep well in Youngstown, Ohio," concluded that "the recent earthquakes in Youngstown, Ohio were induced by the fluid injection at a deep injection" and that the data "may indicate that the earthquakes were directly caused by the pressure buildup and stopped when pressure dropped."[8]

In April 2014 an Ohio state investigation of five small tremors the previous month in the Youngstown area concluded a "probable" link between the tremors and fracking in the region, marking the first time tremors in the region were tied directly to the fracking process itself, rather than the injection of wastewater.[9]

In January 2015 an article published online in the Bulletin of the Seismological Society of America noted that "77 minor earthquakes last March around Poland, Ohio, just across the Pennsylvania-Ohio state line" were caused by fracking.[10]


A 2012 ProPublica investigation into the threat to water supplies from underground injection of waste found the EPA has granted energy and mining companies exemptions to release toxic material in more than 1,500 places in aquifers across the country. The EPA may issue exemptions if aquifers are too remote, too dirty, or too deep to supply affordable drinking water. Applicants must persuade the government that the water is not being used as drinking water and that it never will be. However, EPA documents showed the agency has issued permits for portions of reservoirs that are in use, assuming contaminants will stay within the finite area exempted. EPA officials say the agency has quietly assembled an unofficial internal task force to re-evaluate its aquifer exemption policies.[11]



  1. 1.0 1.1 1.2 1.3 "Basic Information about Injection Wells," EPA, accessed May 2012.
  2. Abrahm Lustgarten, "Injection Wells: The Poison Beneath Us," ProPublica, June 21, 2012.
  3. 3.0 3.1 3.2 3.3 3.4 Abrahm Lustgarten, "Injection Wells: The Poison Beneath Us," ProPublica, June 21, 2012.
  4. 4.0 4.1 Rebecca Hammer, Jeanne VanBriesen, and Larry Levine, "In Fracking's Wake: New Rules are Needed to Protect Our Health and Environment from Contaminated Wastewater," Natural Resources Defense Council, May 2012 report.
  5. 5.0 5.1 "Regulation of Hydraulic Fracturing Under the Safe Drinking Water Act," EPA, accessed May 2012.
  6. Mike Soraghan, "WASTE DISPOSAL: Well construction boom comes despite drive for reuse," E&E, May 24, 2012.
  7. Mike Soraghan, "WASTE DISPOSAL: Well construction boom comes despite drive for reuse," E&E, May 24, 2012.
  8. Won-Young Kim, "Induced seismicity associated with fluid injection into a deep well in Youngstown, Ohio," Journal of Geophysical Research, Volume 118, Issue 7, pages 3506–3518, July 2013.
  9. "Ohio geologists link local earthquakes directly to fracking," al jazeera, April 12, 2014.
  10. "Fracking caused earthquakes in existing faults in Ohio, study says" Don Hopey, Pittsburgh Post-Gazette, January 5, 2015.
  11. Abrahm Lustgarten, "Poisoning the Well: How the Feds Let Industry Pollute the Nation’s Underground Water Supply," ProPublica, Dec. 11, 2012.

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