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By Jeff Danner Jeff has worked in both the chemical and biotech industries and is the veteran of thousands of science debates at cocktail parties and holiday dinners across the nation. In his Common Science blog, Jeff aims to make technological and scientific concepts accessible to all.

A Tale of Two Spills

By Jeff Danner Posted February 16, 2014 at 9:14 pm

On February 2, 2014, a storm water drain at a retired coal-fired power plant near the North Carolina-Virginia border ruptured, which allowed more than 80,000 tons of coal ash to spill into the Dan River. The Dan River is the drinking water source for many communities and is a primary feeder to Kerr Lake Reservoir. This event comes closely on the heels of another coal-industry-related accident, the spill of 4-methylcyclohexane methanol (MCHM) into the Elk River in West Virginia. (Follow this link to my recent column on the events in West Virginia.) These two spills share an important connection: toxic heavy metals.

So what is coal ash? The easiest way to understand it is to consider a fireplace. The sticks and logs you use in a fireplace are flammable, but some parts don’t burn and are left as ash in the bottom. Burning coal in a power plant works the same way; most of it burns but some is left behind as ash. Coal contains small amounts of a number of heavy metals including arsenic, cadmium, selenium, uranium, lead, and mercury. These metals do not burn and are thus left behind in the coal ash.

Among toxins which are harmful to human health, heavy metals are some of the most pernicious. Once they enter the body, be it from breathing in contaminated dusts, ingesting liquids in which heavy metals are suspended or dissolved, or eating fish or shellfish which have eaten heavy metals, these metal atoms tend to accumulate in your body where they can cause a host of problems, including cancer, neurologic disease, and respiratory ailments.

The MCHM which spilled into the Elk River last month in West Virginia is used for the processing of coal. Specifically, it is employed in a step called froth flotation, which helps to remove heavy metals from the coal before is it burned to reduce the toxicity of the resulting ash. Were it not for froth flotation, the Dan River spill would have been even worse.

A comparison of the potential health impacts of these two spills provides important lessons. Let me explain why, if you had the choice, you would want to live along the Elk River rather than the Dan. MCHM has two characteristics that help to limit the long-term damage it can cause: it is a liquid and it is an organic chemical. Since it is a liquid, it can flow and be diluted. As it travels downstream, it will mix with ever-increasing amounts of water until its concentration becomes too low to be harmful. Furthermore, since it is an organic molecule (meaning it is primarily made of carbon, hydrogen, and oxygen), it can be eaten by bacteria in the river which will decompose the MCHM. As a result of these phenomena, the Elk River will be just as clean as it was before the MCHM spill in a matter of weeks.

The prospects are far worse for the Dan River, since it was polluted by coal ash, which is a solid and is inorganic. The coal ash will settle to the river bed and become incorporated into the muck. Then, every time the stream is disturbed by heavy rains or other activity, heavy metal-containing solids will be resuspended to create new hazards. Coal ash derives it toxicity from the metal atoms, which are inorganic. Bacteria can’t digest them, and unless someone drops a nuclear bomb on the Dan River, they won’t break down. Fish in the Dan that feed along the bottom, such as catfish, will accumulate heavy metals in their body fat, making them unacceptable for human consumption. These problems for the Dan River will persist for decades.

Before we close out this discussion, let’s consider why a retired coal plant had tens of thousands of tons of coal ash on site. If you operate a chemical plant, you can’t get a license to operate if you don’t have a method to dispose of the waste. Although the rules should be the same for power plants, they are not. I will leave it to the reader to consider what types of political and financial influences were involved in the formulation of these less restrictive regulations.

Every year in the United States we produce approximately 140 million tons of coal ash. Most of this ash accumulates on site and waits for the Gods of Entropy to conjure up a storm, an earthquake, a human error, or a rusty pipe to allow it to break out of its storage location. Since coal plants are nearly always located along waterways, this situation almost guarantees that more and more of our water ways will be contaminated in the coming years. What makes this circumstance particularly tragic is that it is completely unnecessary. There are no technical or scientific challenges which need to be surmounted to find a way to safely dispose of coal ash. The ash can be safely encased in concrete and returned to the ground, or even incorporated into construction materials. But if the power companies won’t take these potentially costly steps on their own, government intervention is required to protect our waterways.

Have a comment or question? Use the interface below or send me an email to commonscience@chapelboro.com.

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