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{{Short description|Device that places fluid deep underground}}
[[File:Deep injection well.jpg|thumb|right|Deep injection well for disposal of hazardous, industrial and municipal wastewater; a "Class I" well under USEPA regulations.<ref name="EPA Basicinfo"/>]]
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. The fluid may be [[water]], [[wastewater]], [[brine]] (salt water), or water mixed with industrial chemical waste.<ref name="EPA Basicinfo">{{cite web |url=https://www.epa.gov/uic/general-information-about-injection-wells |title=General Information About Injection Wells |publisher=U.S. Environmental Protection Agency (EPA) |location= Washington, DC |date=2020-04-20}}</ref>

==Definition ==
The [[U.S. Environmental Protection Agency]] (EPA) defines an injection well as "a bored, drilled, or driven shaft, or a dug hole that is deeper than it is wide, or an improved sinkhole, or a subsurface fluid distribution system". Well construction depends on the injection fluid injected and depth of the injection zone. Deep wells that are designed to inject [[hazardous wastes]] or carbon dioxide deep below the Earth's surface have multiple layers of protective casing and cement, whereas shallow wells injecting non-hazardous fluids into or above drinking water sources are more simply constructed.<ref name="EPA Basicinfo"/>

==Applications==
{{expand section|date=April 2015}}
Injection wells are used for many purposes.

=== Waste disposal ===
Treated wastewater can be injected into the ground between impermeable layers of rocks to avoid polluting surface waters. Injection wells are usually constructed of solid walled pipe to a deep elevation in order to prevent injectate from mixing with the surrounding environment.<ref name="EPA Basicinfo"/> Injection wells utilize the earth as a filter to treat the wastewater before it reaches the aquifer. This method of wastewater disposal also serves to spread the injectate over a wide area, further decreasing environmental impacts.{{Citation needed|date=January 2021}}

In the United States, there are about 800 deep injection waste disposal wells used by industries such as chemical manufacturers, petroleum refineries, food producers and municipal wastewater plants.<ref>{{cite web |title=Class I Industrial and Municipal Waste Disposal Wells |url=https://www.epa.gov/uic/class-i-industrial-and-municipal-waste-disposal-wells |date=2016-09-06 |website=Underground Injection Control |publisher=EPA}}</ref> Most produced water generated by oil and gas extraction wells in the US is also disposed in deep injection wells.<ref>{{cite report |title=Summary of Input on Oil and Gas Extraction Wastewater Management Practices Under the Clean Water Act |url=https://www.epa.gov/eg/summary-input-oil-and-gas-extraction-wastewater-management-practices-under-clean-water-act-final |archive-url=https://web.archive.org/web/20201016204448/https://www.epa.gov/eg/summary-input-oil-and-gas-extraction-wastewater-management-practices-under-clean-water-act-final |url-status=dead |archive-date=October 16, 2020 |date=May 2020 |publisher=EPA |id=EPA 821-S-19-001 |page=2}}</ref>

Critics of wastewater injection wells cite concerns about potential groundwater contamination. It is argued that the impacts of some injected wastes in groundwater is not fully understood, and that the science and regulatory agencies have not kept up with the rapid expansion of disposal practices in US, where there are over 680,000 wells as of 2012.<ref name="ProPublica-Poison-Beneath">{{cite news |last=Lustgarten |first=Abrahm |title=Injection Wells: The Poison Beneath Us |url=https://www.propublica.org/article/injection-wells-the-poison-beneath-us |date=2012-06-21 |work=ProPublica |location=New York}}</ref>

Alternatives to injection wells include direct discharge of treated wastewater to receiving waters, conditioning of oil drilling and fracking [[produced water]] for reuse, utilization of treated water for irrigation or livestock watering, or processing of water at [[industrial wastewater treatment]] plants.<ref name=Erickson>{{Cite magazine |last=Erickson |first=Britt E. |title=Wastewater from fracking: Growing disposal challenge or untapped resource? |url=https://cen.acs.org/environment/water/Wastewater-fracking-Growing-disposal-challenge/97/i45 |date=2019-11-17 |magazine=Chemical & Engineering News |volume=97 |issue=45}}</ref> Direct discharge does not disperse the water over a wide area; the environmental impact is focused on a particular segment of a river and its downstream reaches or on a coastal water body. Extensive irrigation is not typical in areas where the produced water tends to be salty,<ref name=Erickson /> and this practice is often prohibitively expensive and requires ongoing maintenance and large electricity usage.<ref>{{cite journal |author1=Martin, DL |author2=Dorn, TW |author3=Melvin, SR |author4=Corr, AJ |author5=Kranz, WL |title=Evaluation Energy Use for Pumping Irrigation Water |url=https://www.ksre.k-state.edu/irrigate/oow/p11/Kranz11a.pdf |journal=Proceedings of the 23rd Annual Central Plains Irrigation Conference |location=Burlington, CO |date=February 2011}}</ref>

Since the early 1990s, [[Maui County]], Hawaii has been engaged in a struggle over the 3 to 5 million gallons per day of wastewater that it injects below the [[Lahaina]] Wastewater Reclamation Facility, over the claim that the water was emerging in seeps that were causing [[algae bloom]]s and other environmental damage. After some twenty years, it was sued by environmental groups after multiple studies showed that more than half the injectate was appearing in nearby coastal waters. The judge in the suit rejected the County's arguments, potentially subjecting it to millions of dollars in federal fines. A 2001 consent decree required the county to obtain a water quality certification from the [[Hawaii Department of Health]], which it failed to do until 2010, after the suit was filed.<ref>{{cite web|url=http://www.civilbeat.com/2014/07/federal-judge-rejects-maui-county-arguments-on-lahaina-plant-violations/#comments |title=Federal Judge Rejects Maui County Arguments on Lahaina Plant Violations |date=9 July 2014 |publisher=Civil Beat |access-date=2014-07-22}}</ref> The case proceeded through the [[United States Court of Appeals for the Ninth Circuit]] and subsequently to the [[Supreme Court of the United States]]. In 2020 the Court ruled in ''[[County of Maui v. Hawaii Wildlife Fund]]'' that injection wells may be the "functional equivalent of a direct discharge" under the Clean Water Act, and instructed the EPA to work with the courts to establish regulations when these types of wells should require permits.<ref>{{cite web |url=https://www.bloomberg.com/news/articles/2020-04-23/supreme-court-issues-mixed-ruling-on-reach-of-clean-water-act |title=Supreme Court Gives Environmentalists Partial Win on Water Law |first=Greg |last=Stohr |date=April 23, 2020 |work=Bloomberg News}}</ref>

===Oil and gas production===
{{see|Enhanced oil recovery|Hydraulic fracturing}}
Another use of injection wells is in [[natural gas]] and [[petroleum]] [[Extraction of petroleum|production]]. Steam, [[carbon dioxide]], water, and other substances can be [[water injection (oil production)|injected into an oil-producing unit]] in order to maintain [[petroleum reservoir|reservoir]] pressure, heat the oil or lower its viscosity, allowing it to flow to a producing well nearby.<ref name="EPA Class II">EPA. [https://www.epa.gov/uic/class-ii-oil-and-gas-related-injection-wells "Class II Oil and Gas Related Injection Wells."] Updated 2015-10-08.</ref>

===Waste site remediation===
Yet another use for injection wells is in [[environmental remediation]], for cleanup of either [[soil contamination|soil]] or [[groundwater contamination]]. Injection wells can insert clean water into an [[aquifer]], thereby changing the direction and speed of groundwater flow, perhaps towards [[extraction well]]s downgradient, which could then more speedily and efficiently remove the contaminated groundwater. Injection wells can also be used in cleanup of soil contamination, for example by use of an ozonation system. Complex [[hydrocarbons]] and other contaminants trapped in soil and otherwise inaccessible can be broken down by [[ozone]], a highly reactive gas, often with greater cost-effectiveness than could be had by digging out the affected area. Such systems are particularly useful in built-up urban environments where digging may be impractical due to overlying buildings.<ref>EPA. New York, NY (2003-04-17). [https://web.archive.org/web/20110609041407/http://yosemite.epa.gov/opa/admpress.nsf/6427a6b7538955c585257359003f0230/7bfcdcd6fef70da285257163005c159c!OpenDocument "EPA Announces Cleanup Plan for Contaminated Soil and Ground Water at Central Islip Superfund Site."] Example of use of ozonation wells for remediation ''in situ.''</ref>

===Aquifer recharge===
Recently the option of [[Groundwater recharge|refilling natural aquifers]] with injection or percolation has become more important, particularly in the driest region of the world, the [[MENA]] region (Middle East and North Africa).<ref>H2O magazine (2010-10-16). [http://www.h2ome.net/en/2010/10/strategic-reserve/ "Strategic reserve"] by Anoop K Menon</ref>

[[Surface runoff]] can also be recharged into [[dry well]]s, or simply barren wells that have been modified to functions as cisterns.<ref>H2O magazine (2011-05-03). [https://prototype-creation.de/recharging_dry_wells.pdf/ "Recharging dry wells."] {{Webarchive|url=https://web.archive.org/web/20200708123930/http://www.prototype-creation.de/recharging_dry_wells.pdf |date=2020-07-08 }} by Nicol-André Berdellé</ref> These hybrid [[stormwater]] management systems, called [[recharge well]]s, have the advantage of aquifer recharge and instantaneous supply of potable water at the same time. They can utilize existing infrastructure and require very little effort for the modification and operation. The activation can be as simple as inserting a polymer cover (foil) into the well shaft. Vertical pipes for conduction of the overflow to the bottom can enhance performance. The area around the well acts as funnel. If this area is maintained well the water will require little purification before it enters the cistern.<ref>Prototype-Creation (2011-04-20). [http://www.prototype-creation.de/recharge_wells.pdf "Recharge wells and ASR."] by Nicol-André Berdellé</ref>

===Geothermal energy===
Injection wells are used to tap [[geothermal energy]] in hot, porous rock formations below the surface by injecting fluids into the ground, which is heated in the ground, then extracted from adjacent wells as fluid, steam, or a combination of both. The heated steam and fluid can then be utilized [[geothermal power|to generate electricity]] or directly for [[geothermal heating]].<ref name="EERE pamphlet">{{cite web |title=Geothermal Technologies Program: Tapping the Earth's energy to meet our heat and power needs |url=https://www.nrel.gov/docs/fy04osti/36025.pdf |publisher=U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy |access-date=2 June 2018 |date=April 2004}}</ref><ref name="Fitch and Matlick 2008">{{cite journal |last1=Fitch |first1=David |last2=Matlick |first2=Skip |title=Gold, silver and Other Metals in scale— Puna Geothermal Venture, Hawaii |journal=GRC Transactions |date=2008 |volume=32 |pages=385–388 |url=http://pubs.geothermal-library.org/lib/grc/1028353.pdf |access-date=2 June 2018 |archive-date=1 November 2016 |archive-url=https://web.archive.org/web/20161101002822/http://pubs.geothermal-library.org/lib/grc/1028353.pdf |url-status=dead }}</ref><ref name="Direct uses">{{cite web |last1=Gill |first1=Andrea T. |title=Prospective Direct Use Enterprises in Kapoho, Hawaii |url=https://energy.hawaii.gov/wp-content/uploads/2011/10/Prospective-Direct-Use-Enterprises-in-Kapoho-Hawaii.pdf |publisher=Hawaii Dept. of Business, Economic Development and Tourism, Strategic Industries Division |access-date=2 June 2018 |date=2004}}</ref>

==Regulatory requirements==
In the United States, injection well activity is regulated by EPA and state governments under the [[Safe Drinking Water Act]] (SDWA).<ref name="EPA Basicinfo"/> The “State primary enforcement responsibility” section of the SDWA provides for States to submit their proposed UIC program to the EPA to request State assumption of primary enforcement responsibility. <ref>{{USC|42|300h-1}}(b)</ref> Thirty-four states have been granted UIC primacy enforcement authority for Class I, II, III, IV and V wells.<ref name="EPA-UIC-primacy">{{cite web |url=https://www.epa.gov/uic/primary-enforcement-authority-underground-injection-control-program |archive-url=https://web.archive.org/web/20151013162417/http://www2.epa.gov/uic/primary-enforcement-authority-underground-injection-control-program |url-status=dead |archive-date=October 13, 2015 |title=Primary Enforcement Authority for the Underground Injection Control Program |author= |date=2019-04-15 |publisher=EPA}}</ref> For states without an approved UIC program, the EPA administrator prescribes a program to apply.<ref>{{USC|42|300h-1}}(c)</ref> EPA has issued Underground Injection Control (UIC) regulations in order to protect drinking water sources.<ref name="EPA Regs">EPA. [https://www.epa.gov/uic/underground-injection-control-regulations "Underground Injection Control Regulations."] Updated 2015-10-05.</ref><ref>EPA. (July 2001). [https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=2000E99H.PDF "Technical Program Overview: Underground Injection Control Regulations."] Document no. EPA 816-R-02-025.</ref>

EPA regulations define six classes of injection wells. Class I wells are used for the injection of municipal and industrial wastes beneath underground sources of drinking water. Class II wells are used for the injection of fluids associated with oil and gas production, including waste from hydraulic fracturing. Class III wells are used for the injection of fluids used in mineral [[solution mining]] beneath underground sources of drinking water. Class IV wells, like Class I wells, were used for the injection of hazardous wastes but inject waste into or above underground sources of drinking water instead of below. EPA banned the use of Class IV wells in 1984.<ref>{{cite web |url=https://www.epa.gov/uic/class-iv-shallow-hazardous-and-radioactive-injection-wells |title=Class IV Shallow Hazardous and Radioactive Injection Wells |author= |date=2016-09-06 |website=Underground Injection Control |publisher=EPA}}</ref> Class V wells are those used for all non-hazardous injections that are not covered by Classes I through IV. Examples of Class V wells include stormwater drainage wells and [[Septic drain field|septic system leach fields]]. Finally, Class VI wells are used for the injection of carbon dioxide for [[Carbon sequestration|sequestration]], or long term storage.<ref name="EPA Basicinfo"/> Since the introduction of Class VI in 2010, only two Class VI wells have been constructed as of 2022, both at the same Illinois facility; four other approved projects did not proceed to construction. <ref>{{cite web|url=https://www.mayerbrown.com/en/insights/publications/2022/06/carbon-capture-utilization-and-storage-class-vi-wells-and-us-state-primacy|title="CARBON CAPTURE, UTILIZATION, AND STORAGE: CLASS VI WELLS AND US STATE PRIMACY"|author=
Philip K. Lau and Nadav C. Klugman|date=2022-06-22}}</ref>

==Injection-induced earthquakes==
[[File:Cumulative induced seismicity.png|thumbnail|Cumulative number of earthquakes in the central U.S. The red cluster at the center of the map shows an area near Oklahoma which experienced the largest increase in activity since 2009.]]
{{see also|Induced seismicity#Waste_disposal_wells|label 1=Induced seismicity § Waste disposal wells}}
A July 2013 study by US Geological Survey scientist William Ellsworth links earthquakes to wastewater injection sites. In the four years from 2010-2013 the number of earthquakes of magnitude 3.0 or greater in the central and eastern United States increased dramatically. After decades of a steady earthquake rate (average of 21 events/year), activity increased starting in 2001 and peaked at 188 earthquakes in 2011, including [[2011 Oklahoma earthquake|a record-breaking 5.7-magnitude earthquake]] near [[Prague, Oklahoma]] which was the strongest earthquake ever recorded in Oklahoma. USGS scientists have found that at some locations the increase in seismicity coincides with the injection of wastewater in deep disposal wells. Injection-induced earthquakes are thought to be caused by pressure changes due to excess fluid injected deep below the surface and are being dubbed “man-made” earthquakes.<ref name="Man-Made Earthquakes Update">USGS. [http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/ "Man-Made Earthquakes Update"] {{Webarchive|url=https://web.archive.org/web/20140329224145/http://www.usgs.gov/blogs/features/usgs_top_story/man-made-earthquakes/ |date=2014-03-29 }} Updated January 17, 2014.</ref> On September 3, 2016, [[2016 Oklahoma earthquake|a 5.8-magnitude earthquake]] occurred near [[Pawnee, Oklahoma]], followed by nine aftershocks between magnitudes 2.6 and 3.6 within three and one-half hours. The earthquake broke the previous record set five years earlier. Tremors were felt as far away as [[Memphis, Tennessee]], and [[Gilbert, Arizona]]. [[Mary Fallin]], the Oklahoma governor, declared a local emergency and shutdown orders for local disposal wells were ordered by the Oklahoma Corporation Commission.<ref>[http://hosted.ap.org/dynamic/stories/U/US_MIDWEST_EARTHQUAKE Record tying Oklahoma earthquake felt as far away as Arizona], ''[[Associated Press]]'', Ken Miller, September 3, 2016. Retrieved 4 September 2016.</ref><ref>[http://www.enidnews.com/news/updated-with-fallin-comments-aftershocks-large-and-long-earthquake-felt/article_184f9e1e-71d2-11e6-8dc9-87f17af9538d.html USGS calls for shut down of wells, governor declares emergency in wake of 5.6 quake in Oklahoma], ''[[Enid News & Eagle]]'', Sally Asher & Violet Hassler, September 3, 2016. Retrieved 4 September 2016.</ref> Results of ongoing multi-year research on induced earthquakes by the [[United States Geological Survey]] (USGS) published in 2015 suggested that most of the significant earthquakes in Oklahoma, such as the 1952 magnitude 5.5 El Reno earthquake may have been induced by deep injection of waste water by the oil industry.<ref name="usgs_2015">{{cite web |url=http://www.usgs.gov/newsroom/article.asp?ID=4362#.Vj-sOpTIxku |title=A Century of Induced Earthquakes in Oklahoma? |last1=Hough |first1=Susan E. |last2=Page |first2=Morgan |date=October 20, 2015 |publisher=U.S. Geological Survey |access-date=November 8, 2015 |quote=Several lines of evidence further suggest that most of the significant earthquakes in Oklahoma during the 20th century may also have been induced by oil production activities. Deep injection of waste water, now recognized to potentially induce earthquakes, in fact began in the state in the 1930s.}}</ref>

==Notes==
{{Reflist}}

==References==
{{refbegin}}
* US Army Environmental Center. Aberdeen Proving Ground, MD (2002). [http://www.frtr.gov/matrix2/section4/4-54.html "Deep Well Injection."] ''Remediation Technologies Screening Matrix and Reference Guide.'' 4th ed. Report no. SFIM-AEC-ET-CR-97053.
{{refend}}

==External links==
{{Commons category|Injection wells}}
*[https://www.epa.gov/uic EPA - Underground Injection Control Program]

{{Wastewater}}

{{DEFAULTSORT:Injection Well}}
[[Category:Drinking water]]
[[Category:Hydrology]]
[[Category:Natural gas technology]]
[[Category:Petroleum technology]]
[[Category:Water pollution]]
[[Category:Oil wells]]
[[Category:Water wells]]

Injection well - Revision history

OpenDEM 1: 1 revision imported from :wikipedia:en:Injection_well

wikipedia:en>GreenC bot: Rescued 3 archive links; Move 5 urls. Wayback Medic 2.5 per WP:URLREQ#epa.gov