This post discusses the impact disposal wells have on seismic activity in the communities in which the wells are used. An injection well “places fluid deep underground into porous rock formations, such as sandstone or limestone, or into or below the shallow soil layer.” Disposal wells are often used to dispose of the fluids used in hydraulic fracturing and the wastewater produced in drilling operations by injecting those fluids into rock formations thousands of feet underground. Disposal wells are cased and cemented, and are often considered to be the final resting place for used drilling fluid. Disposal wells are considered to be the safest and most cost-efficient way to get rid of the fluids from fracking.
Earthquakes surrounding the use of disposal wells have become a developing environmental concern. Increasingly over the past few years, scientists and surveyors have reported increased seismic activity in the vicinity of injection wells. These earthquakes have been occurring in areas that have not been historically seismically active, including in states such as, Arkansas, Colorado, Ohio, and Texas. The drilling of injection wells may cause destabilization in older fault lines, which could be the cause of earthquakes. The earthquakes can occur when injecting wastewater into disposal wells causes “shock waves or fluids [to] release strain on a preexisting fault.” “Thus, ‘high-pressure fluid can squeeze into and push apart a planar fault, freeing adjacent rock formations to slide past one another.’” These faults are capable of sustaining high stresses without slipping “because natural ‘tectonic’ stress and the weight of the overlying rock pushes the opposing sides of the fault together, increasing the frictional resistance to fault slip;” however, when wastewater is injected into deep wells, it can counteract the frictional forces on faults and cause an earthquake.
Proving the theory that wastewater injection causes earthquakes is difficult because there is a small data set with only a few discrete events. There are more than 144,000 operational disposal wells in the United States, but less than ten have been linked to earthquakes. As of March 2014, Oklahoma experienced the second most earthquakes in the country, only behind California, and these earthquakes are unlikely to be the result of natural variations in earthquake rates. The city of Youngstown, Ohio in late 2011, experienced a series of earthquakes believed to be connected to the operation of a particular injection well. Following these earthquakes, the Ohio Department of Natural Resources (DNR) issued a statement noting that the injection well probably was the cause of the earthquakes felt in Youngstown. In this report, the Ohio DNR stated that many geologists believe the following circumstances must exist in order for an injection well to induce seismic activity:
A fault must already exist within the crystalline basement rock; that fault must already be in a nearfailure state of stress; an injection well must be drilled deep enough and near enough to the fault and have a path of communication to the fault; and the injection well must inject a sufficient quantity of fluids at a high enough pressure and for an adequate period of time to cause failure, or movement, along that fault (or system of faults).
Since 2010, there have been a few studies in Texas linking disposal wells and earthquakes in the Barnett Shale. One study, conducted by researchers at Southern Methodist University and the University of Texas at Austin, determined that the operation of a saltwater injection disposal well in the area was a “plausible cause” of the Dallas/Fort Worth earthquakes that occurred in 2008 and 2009.. However, Carl Frohlich, the researcher from the University of Texas still stated that he believes it is almost impossible to say with certainty that an earthquake is manmade. Because the vast majority of injection wells are not associated with earthquakes, it leads to the question “why one and not the other?” In April 2015, Southern Methodist University published another study, ultimately saying that wastewater injection likely promotes seismic activity, though some uncertainties remain because of the thousands of injection wells not associated with earthquakes. This study focused on earthquakes occurring in Azle, Texas in 2013 and 2014, and found that “high volumes of wastewater injection combined with saltwater (brine) extraction from natural gas wells is the most likely cause” of these earthquakes. Based on these studies, the scientific community has “reached a consensus” that some of the nationwide increase “in seismic activity is related to underground injection and disposal of wastewater” from the oil and gas production process.
Because of the developing concern over earthquakes, state authorities have taken steps to address the risk of seismic activity associated with injection wells. For example, after a series of earthquakes in Arkansas that were suspected to be connected to oil and gas activity, the Arkansas Oil & Gas Commission issued an order prohibiting the operation of disposal wells in a particular area. In response to earthquakes in Ohio, the state has enacted one of the more demanding regulatory schemes, requiring any new horizontal drilling “within three miles of a fault or seismic activity above a 2.0 magnitude” to be placed with a sensitive seismic monitor. Furthermore, if any seismic activity above a 1.0 magnitude is detected, then activity is paused for investigation, and if that investigation reveals a probable connection between “oil and gas operations and seismic activity,” then operations are suspended indefinitely.
There are calls for similarly focused regulations in Texas that increased with urgency in 2014 after a series of earthquakes in north Texas. The Railroad Commission of Texas (RRC), who oversees oil and gas drilling in the state, is in charge of permitting and inspecting disposal and injection wells. In October of 2014, the RRC adopted amendments to portions of its rules governing disposal wells to incorporate requirements dealing with seismic events. These amendments state that some oil and gas operators may be required to submit more frequent reports than the standard monthly and annual reports. Under the new amendments, permit applications for injection wells would require inclusion of information regarding the locations of historical seismic events within the designated radius. In high-risk areas, the RRC may now require additional information such as “logs, geologic cross-sections, and/or structure maps” to accompany the permit application. If the RRC suspects an injection well is causing seismic activity, then the amendments allow it to “modify, suspend, or terminate” a permit. With these amendments, the RRC can slow or halt injections into a well if it becomes problematic. Overall, despite the fact that some uncertainty remains about the link between injection wells and earthquakes, states are moving towards more strict regulations in this field.
 Basic Information about Injection Wells (May 4, 2012), http://water.epa.gov/type/groundwater/uic/basicinformation.cfm.
 How Oil and Gas Disposal Wells Can Cause Earthquakes, https://stateimpact.npr.org/texas/tag/earthquake/.
 Spencer Salmon, Booms and Busts: Preserving Mother Nature While Staring into the Abyss of Bankruptcy, 16 Tex. Tech. Admin L.J. 465, 477 (2015).
 Monika Ehrman, The Next Great Compromise: A Comprehensive Response to Opposition Against Shale Gas Development Using Hydraulic Fracturing in the United States, 46 Tex. Tech L. Rev. 423, 460-61 (2014).
 Salmon, supra note 5, at 478.
 Ehrman, supra note 7, at 462.
 Id. at 462.
 David J. Hayes, Is the Recent Increase in Felt Earthquakes in the Central US Natrual or Manmade? (April 11, 2012), https://www.doi.gov/blog/Is-the-Recent-Increase-in-Felt-Earthquakes-in-the-Central-US-Natural-or-Manmade
 Ehrman, supra note 7, at 461.
 See Keith Hall, Recent Developments in Hydraulic Fracturing Regulation and Litigation, 29 J. Land Use & Envtl. L. 29, 51–52 (2013).
 See Victor Flatt & Heather Payne, Curtailment First: Why Climate Change and the Energy Industry Suggest a New Allocation Paradigm is Needed for Water Utilized in Hydraulic Fracturing, 48 U. Rich. L. Rev. 829, 835 (2014).
 Richard D. Andrews, Statement on Oklahoma Seismicity (April 21, 2015), http://wichita.ogs.ou.edu/documents/OGS_Statement-Earthquakes-4-21-15.pdf
 Hall, supra note 13, at 51.
 Id. at 52.
 Terrence Henry, How Fracking Disposal Wells are Causing Earthquakes in Dallas-Fort Worth (Aug. 6, 2012), https://stateimpact.npr.org/texas/2012/08/06/how-fracking-disposal-wells-are-causing-earthquakes-in-dallas-fort-worth/.
 SMU-UT Study Shows ‘Plausible’ Connection Between DFW Quakes and Saltwater Injection Well (March 10, 2010), http://www.smu.edu/News/2010/dfw-earthquake-study-10march2010.
 Ehrman, supra note 7, at 462.
 Jim Fuquay, Researchers Say Finding Cause of Azle Quakes Will Take Time, Star-Telegram (Feb. 7, 2014), http://www.star-telegram.com/2014/02/07/5550415/smu-researchers-say-azle-quakes.html, archived at http://perma.cc/73WR-W69R.
SMU-led Seismology Team Reveals Azle Findings: Combination of Gas Field Fluid Injection and Removal is Most Likely Cause of 2013–14 Earthquakes (April 21, 2015), https://www.smu.edu/News/2015/earthquakes-azle-report-21april2015.
 Carlos Romo & Colin Cox, Natural Resources, 45 Tex. Envtl. L.J. 401, 403 (2015).
 See Hall, supra note 13, at 51.
 Ohio Announces Tougher Permit Conditions for Drilling Activities Near Faluts and Areas of Seismic Activity (April 11, 2014), http://ohiodnr.gov/news/post/ohio-announces-tougher-permit-conditions-for-drilling-activities-near-faults-and-areas-of-seismic-activity.
 Romo & Cox, supra note 25.
 Henry, supra note 19.
 Memorandum from the Railroad Commission of Texas Office of General Counsel (Oct. 21, 2014), available at http://www.rrc.state.tx.us/media/24613/adopt-amend-3-9and3-46-seismic-activity-102814-sig.pdf.
 16 Tex. Admin. Code. §3.46(i)(2) (2014) (Tex. R.R. Comm’n, Fluid Injection into Productive Reservoirs).
 16 Tex. Admin. Code § 3.9(B) (2014) (Tex. R.R. Comm’n, Disposal Wells).
 16 Tex. Admin Code §3.9(C).
 16 Tex. Admin Code $3.46(d)(1)(F).
 Jim Malewitz, Responding to Quakes, Texas Passes Disposal Well Rules (Oct. 28, 2014), https://stateimpact.npr.org/texas/2014/10/28/responding-to-quakes-texas-passes-disposal-well-rules/.