An Ohio oil and gas services contractor pled guilty on Thursday to dumping thousands of gallons of fracking wastewater into the Mahoning River in eastern Ohio. Hardrock Excavating LLC employee Michael Guesman admitted to dumping the toxic waste, also known as “flowback” and “produced water,” down a stormwater drain on numerous occasions over a three-month period, according to Law360.

In March, federal prosecutors filed an indictment against Hardrock LLC, Guesman, and Hardrock company owner, Benedict Lupo, after it was discovered that Lupo ordered his employee to dispose of wastewater, from their Youngstown, Ohio facility, at night when no one else was on the premises.

The Ohio Department of Natural Resources received an anonymous tip in January stating that someone was dumping wastewater from the Hardrock facility into the storm drain that emptied into a tributary leading to the Mahoning River.

The Youngstown facility stores 58 tanks that hold about 20,000 gallons each. On Lupo’s orders, Guesman began dumping wastewater at the beginning of November and continued for at least three months. Ohio Environmental Protection Agency (EPA) officials examined the dumping site after receiving the tip, and found the tributary leading into the Mahoning River “contained puddles of oil throughout its entire length.”

According to officials, a sample of the wastewater contained benzene, a known carcinogen for people and animals, the volatile solvent, toluene, and other pollutants.

Fracking wastewater contains toxic and hazardous materials used during the fracking process, but can also contain contaminants picked up from deep underground. Naturally-occurring radioactive substances such as radium are commonly found in drilling wastewater.

In 2011, the New York Times reviewed over 30,000 pages of documents from state and federal agencies, including EPA documents that revealed that fracking wastewater contains radioactive and toxic materials, often at levels much higher than those that federal regulators have deemed safe for wastewater treatment plants to handle.

Unfortunately, illegal dumping of toxic fracking waste is not uncommon. But wastewater poses a threat to drinking water and food supplies not only when dumped illegally, but when disposed of through the common practice of pumping the wastewater deep underground.

Over the last few decades, the US fracking industry has pumped over 30 trillion gallons of toxic wastewater deep into the earth in order to dispose of the hazardous byproduct of their drilling processes.

In 2010, there were over 680,000 underground waste and injection wells nationwide, according to a ProPublica report. Case histories and government summaries of wells show that structural failures inside injection wells are “routine.” Records show that wells leak, releasing their toxic contents into the ground, and are frequently operated in violation of safety regulations and under risky conditions.

Alisha is a writer and researcher with Ring of Fire. Follow her on Twitter @childoftheearth.