This is the conclusion of a three-part series inspired by the North Carolina General Assembly’s decision to make the disclosure of the chemicals used in fracking a crime here in the Tar Heel State, purportedly to protect the trade secrets of the drilling companies. In Part I, I reviewed why I do not believe that the identities of these chemicals qualify as trade secrets. In Part II, I gave my opinion on what I believe to be the actual motivations for the legislation. This week, I want to direct your attention to an important part of the fracking process that gets very little media attention: the fate of the water and chemicals that are extracted from the well after the underground rocks have been broken.

Before we proceed, let’s quickly review the fracking process. First, a drilling company locates what it believes to be an underground deposit of oil and/or gas contained within non-porous rock. (If the rock was porous, fracking would not be necessary.) A vertical hole is drilled straight down to the depth of the deposit and then multiple horizontal holes are drilled out from the bottom of the vertical hole. Next a mixture of water, sand, and chemicals is pumped into the horizontal holes where high temperatures and pressures combine to fracture the rocks. Approximately 40% of the water and chemicals are pumped back out of the well to the surface, while the sand and the remainder of the liquids stay underground forever. Once this is accomplished, extraction of oil or gas from the well can commence.

Hundreds of different chemicals are used in the fracking process, many of which are toxic and/or carcinogenic. (For a full list of the typical chemicals used in fracking and their functions, please open this link.) Much of the concern about fracking stems from the fear that these toxic substances could migrate underground from the zone where the fracking occurred into underground aquifers which are utilized for drinking water and/or agriculture. This risk is valid, and there have been a number of documented cases where this appears to have occurred, with a notable case in Pavillion, Wyoming. (1)

But what about the 40% of the fracking liquids which are pumped out of the well? Where do they go, and what sort of risks do they present?

When water is extracted from the well after the fracking process, it contains a portion of the chemicals it started with, plus others which are absorbed from the underground rock formations, particularly hydrocarbons and toxic heavy metals. Depending on the location of the well, some of the heavy metals may be radioactive. From here forward, I’ll refer to the mixture of liquids extracted from the well as fracking wastewater.

When fracking wastewater is extracted from the well, it is usually first collected in a temporary, open pond. Both of the adjectives describing the ponds should concern you. Since the ponds are intended to be temporary, there is an incentive to make them just sturdy enough to do the job, with little safety margin for the unexpected. In addition, open ponds often overflow in heavy rains. Spills of fracking wastewater from a pond have a far easier path to pollute our drinking water sources than the wastewater left underground.

Once the wastewater is contained in the pond, the drilling company needs to figure out what to do with it. Given that it is called wastewater, people often think we could send it to a municipal wastewater treatment plant. We can’t. Municipal wastewater treatment plants remove solids with filtration and then clean the dissolved organic material (poop) by letting bacteria eat it. Fracking wastewater includes many dissolved chemicals which bacteria cannot eat.

The fracking wastewater can be cleaned using an expensive, energy-intensive process, the details of which I will omit for the sake of brevity. Given that there are millions of gallons of wastewater produced from each well, the drilling companies are always on the look-out for less expensive solutions for its disposal. A common, less expensive approach is to inject the wastewater into either an old oil or gas well or into a new well drilled explicitly for wastewater disposal.

In Oklahoma, where fracking began in earnest in 2008, there are now thousands of fracked wells, and wastewater injection is a very common disposal technique. The combination of shattering the underground rock by fracking and pumping wastewater into disposal wells has had a dramatic effect on seismic activity. The graph below shows the absolutely stunning increase in the incidence of earthquakes registering 3.0 or higher on the Richter Scale since fracking began in Oklahoma, from a historical rate of one or two a year up to the current level of one or two a day! The geographic correspondence between the earthquakes and the drilling activities (they are in precisely the same places) is nearly exact, leaving very little doubt that fracking and the injection of the wastewater are the cause.

Oklahoma Earthquake Graph

The implications for North Carolina are clear. Given that fracking in NC appears to be inevitable, we need to do our best to ensure that the regulations give adequate attention to the wastewater handling. Among other things, the wastewater storage ponds must be well constructed and account for the possibility of heavy rains. The drilling companies should be required to treat the wastewater in a thorough and responsible manner rather than simply injecting it back into the ground. Otherwise our experience with fracking is likely to be particularly unpleasant.

Have a comment or question? Use the interface below or send me an email to Think that this column includes important points that others should consider? Send out a link on Facebook or Twitter. Also, please note that I am taking a rare vacation from writing. This will be the last Common Science until June 29th.

(1) Reports in the general media will usually cite higher rates of the incidence of drinking water contamination from fracking than you will see in my columns. I’d like to explain why. The vast majority of fracking-related water contamination events reported in the media are situations where the water has a higher than normal level of methane (the primary component of natural gas.) While I understand the rationale for including them, I do not.
First of all, since methane is everywhere, it is present at some level in all drinking water. Furthermore, it is biologically inert. So even if you are ingesting some in your drinking water, you body will not interact with it in any way. Therefore, it can’t hurt you.

Furthermore, since methane is not very soluble in water, your maximum exposure is limited. Due to this low solubility, I would like to note that I feel strongly that the famous scene in the movie Gasland where a man lights his kitchen faucet on fire was a fake. As far as I can tell, it is thermodynamically impossible.

I only count situations where a chemical added to the fracking process, many of which are quite harmful, ends up in drinking water. These situations have been less frequent than methane contamination, but they are far more troubling.