With the exception of old black-and-white photography, nothing is truly black and white. Just about everything is more complex, nuanced and more layered than it first appears. This is certainly true when it comes to drilling for oil and natural gas. Initially, fracking was seen as an improvement to the industry’s drilling process, because it made each well much more efficient, and this has allowed natural gas to supplant dirtier coal in fueling power plants. But soon people began to express concerns about whether the liquids used in the fracking process were affecting water quality. Now studies are showing that the fracking liquid is too dense to migrate the significant distance (usually several thousand feet) between shale deposits and aquifers. Newer drilling practices are also recycling up to 90 percent of the extractable fracking liquids for additional fracking procedures, significantly limiting the amount of fracking liquid that is available to contaminate surface water or nearby land.
In the same way, the use of strong, uniformly-shaped grains of sand as “proppants” in the fracking process was initially hailed as an industry breakthrough, but not long after, concerns began to raise about the possibility of airborne dust particles being released during frac sand mining and processing. Like the fossil fuel drilling industry in which it plays an integral part, the frac sand industry understands this skepticism, and recognizes the need for safety and environmental stewardship, and is embracing the important steps necessary to maximize safety, and minimize the environmental impact of mining, processing, and transporting frac sand.
Mining Frac Sand
When it comes to mining frac sand, the biggest issue for both mine workers and nearby residents is “fugitive dust,” which is raised during the process of mining the sand. Mining companies are required to have processes in place for controlling fugitive dust in states like Wisconsin, where 75 percent of the frac sand is currently being mined. This means more than controlling dust during the blasting process; it also covers dust that might blow off of conveyer belts, trucks or piles of sand.
Minnesota’s Department of Health recently established a guideline for particulate exposure of no higher than 3 micrograms per cubic meter of particulates that measure 4 or less micrometers in diameter. This diameter, called the PM4 for short, is the size that worries health experts, measuring less than one-tenth the diameter of a human hair.
Frac sand companies like EOG Resources are funding their own studies to ensure safety for their workers and those who live nearby. EOG Resources is monitoring PM4 type emissions at four Wisconsin facilities, and has found the air to contain “much lower concentrations” than Minnesota’s established guideline, according to Wisconsin’s Department of Natural Resources (WDNR). In Minnesota, frac sand mining companies are committed to the environmental review process and willing to spend the millions of dollars necessary to adhere to state regulations, according to Dennis Egan of the Minnesota Industrial Sand Council.
Other environmental issues raised in the mining process are no different than they would be for any other type of mining. For example, the digging and loading machines used to mine the sand naturally emit what the WDNR rates as “insignificant” levels of air pollution. The removal, storage and reclamation of topsoil are both regulated and monitored, with soil stockpiles being seeded and mulched to minimize fugitive dust.
Processing Frac Sand
Once the frac sand has been removed from the ground, it must be further processed to prepare it for use in the fracking process. The first step in processing is usually the crushing of larger blocks of mined rock in order to break loose the individual grains of sand. The fugitive sand regulations mentioned above cover this process as well (in Wisconsin, the particular codes are s. NR 415.075(6) and s. NR 440.688, Wis. Adm. Code), and companies must take measures to ensure that processing adheres to these regulations.
Once the sand is separated into individual grains, it must be washed to remove smaller particulates and clay deposits. This is usually done by adding water to the sand to form a slurry, which is both easier to transport and captures any fugitive dust within the water. The water used in this process is conserved and recycled through the use of settling ponds, thus minimizing the amount of water needed and keeping the fugitive dust under control.
After washing, the sand is screened to sort it by size, then stored in a stockpile to dry. Mechanical dryers are often used to complete the process, but since the washing process has removed most, if not all, of the smaller particulates, there is minimal fugitive dust raised as the sand is transferred via loaders or conveyer belts from stockpiles to dryers, then to train cars for transport to the drilling site.
Transporting Frac Sand
Both because of their own need to save on transportation costs and from a desire to minimize pollution, companies in the frac sand industry have researched the logistics of transporting sand from the mine to the wellhead, and determined that “unit trains” of 100 cars or more are the best method for transporting sand the significant distances required. Frac sand companies are collaborating with railroads to lay new track and create distribution hubs in order to minimize the number of miles that frac sand must be transported by truck. For example, Unimin Corporation, the largest frac sand company in the US market, has signed a long-term agreement with Canadian Pacific Railroad to transport its sand, and opened a rail distribution terminal in Lubbock, Texas, close to the Permian Basin drilling area.
From mining to processing, and even as far as transport, companies in the frac sand industry are taking major steps in their commitment to minimizing the impact of frac sand, both in safety and in preservation of the environment. In an industry where there is more than meets the eye, this commitment to a myriad of approaches is required to maximize safety and environmental stewardship.