Hydraulic fracturing (fracking) wastewater injection wells can cause increased risk of seismic activity.
As a Pivotal Resource, Fulcrum is constantly monitoring the construction landscape and researching to identify potential risks for our clients.
When it comes to the construction risk perspective related to seismic activity, most people think primarily about the West Coast of the United States. Oklahoma, Connecticut, or Texas may not come to mind; however, these should. It is typically not the places we expect and plan for this kind of impact that pose the greatest risk; it is the places where we do not expect seismic activity to occur that can cause the greatest damage. Likewise, when we contemplate how we obtain our energy, such as drilling for natural gas, what comes to mind are soil pollution issues, contaminated water supplies, or increased industrial activity driving land value down. The thought of manmade earthquakes is not something typically planned for. Still, the risk is increasing and, depending on where a new construction or existing structure is located, the risk may be great. In the case of hydraulic fracking, approximately half of all natural gas will be recovered through this process over the next 20 years. This process has not been unequivocally tied directly to earthquakes; however, it generates a lot of wastewater, and that waste is often stored in underground injection wells or voids in the Earth’s natural formations.
Image Copyright © 2012 Thomson Reuters
The real issue, as it relates to seismic activity, appears to be less a result of the actual fracking and more a result of what happens afterward. The wastewater treatment and storage process includes a large amount of storage in underground “storage” areas, also known as the Earth. Similar to the way rain water is naturally stored in the Earth in freshwater aquifers, the waste from fracking operations (basically salt water or brine and an aqueous mixture of proprietary chemicals) is stored in the gaps between geologic formations or layers in the ground. Part of the advantage to the fracturing process of using this mixture is that it maintains a level of lubricating quality in addition to the pressure it applies for its intended purpose; however, this lubricating quality also reportedly has an effect on the geologic formations it comes into contact with.
These geologic formations act like tectonic plates and are often under pressure. As it applies to known geographic areas of high risk such as California, Alaska and certain Mississippi Valley areas within Seismic Zone 3 or Zone 4 (IBC), the slippage allowed is what accounts for earthquakes. In other areas of the country, even though there are geologic formations under pressure, the conditions are usually not likely to result in earthquakes, because there is no real ability for the plates to shift violently. They are under so much force and there is so much pressure, that they just cannot reasonably move. That is, unless we introduce a lubricant – which is, apparently, exactly what the storage of this lubricating waste from the fracking process may serve to do. Areas where earthquakes did not previously factor into our design and building considerations are now observing the effects of a changing situation, where this seismic activity should therefore be accounted for in regions such as the Midwest, Northeast, or Southwest. The risk is also exacerbated in already susceptible areas like California.
Image Courtesy of the Department of the Interior/USGS
The Oklahoma Geological Survey states that the post-fracking earthquake rate is now 600 times higher than its natural seismicity. A vast majority of these earthquakes are the result of the wastewater product injection into the underground storage areas. Fracking itself can also induce earthquakes, but the technique has never caused earthquakes greater than magnitude 4. Though that magnitude can still be problematic, research and data show that wastewater injection is capable of producing much greater activity. For instance, an Oklahoma wastewater injection well reportedly triggered a 5.6 magnitude earthquake in 2011. Though fracking operations are not the only cause of manmade seismic activity (geothermal energy plant operations and mining blasts can also generate earthquakes), the data is sufficiently solid to allow the savvy developer and builder to plan ahead for the probability of loss from this operation. As a pivotal resource, Fulcrum remains ever vigilant in assisting to identify and mitigate risk no matter where or how it is imposed.
Image Courtesy of the Department of the Interior/USGS
According to the U.S. Geological Survey (USGS), parts of 42 states are at risk of earthquakes during the next 50 years (typical building lifetime). It is not the earthquakes that kill people, but the buildings and infrastructure that were not built to withstand them. The ability to identify this risk proactively can save time, money, and lives. We cannot always avoid risk, but we can mitigate the negative effects and increase the probability of success. Fulcrum is dedicated to helping our clients ensure that this process is properly managed. Fulcrum teams with professional structural engineers, geologists, and environmental scientists to seek solutions to our clients’ needs to both protect against and to mitigate risk.
Jack Runnels contributed to this article