WASTEWATER ONSLAUGHT: The McKeesport Sewage Treatment Plant, one of nine plants on the Monongahela River that has treated wastewater from Marcellus Shale drilling operations.
CREDIT: PROPUBLICA/JOAQUIN SAPIEN

Workers at a steel mill and a power plant were the first to notice something strange about the Monongahela River last summer. The water that U.S. Steel and Allegheny Energy used to power their plants contained so much salty sediment that it was corroding their machinery. Nearby residents saw something odd, too. Dishwashers were malfunctioning, and plates were coming out with spots that couldn’t easily be rinsed off.

Pennsylvania’s Department of Environmental Protection soon identified the likely cause and came up with a quick fix. The Monongahela, a drinking water source for 350,000 people, had apparently been contaminated by chemically tainted wastewater from the state’s growing natural gas industry. So the DEP reduced the amount of drilling wastewater that was being discharged into the river and unlocked dams upstream to dilute the contamination.

But questions raised by the incident on the Monongahela haven’t gone away.

In August, contamination levels in the river spiked again, and the DEP still doesn’t know exactly why. And this month the DEP began investigating whether drilling wastewater contributed to the death of 10,000 fish on a 33-mile stretch of Dunkard Creek, which winds through West Virginia and feeds into the Monongahela. A spate of other water contamination problems have also been linked to gas drilling in Pennsylvania, including methane leaks that have affected drinking water in at least seven counties.

2011: 19 million gallons, per day

Pennsylvania is at the forefront of the nation’s gas drilling boom, with at least 4,000 new oil and gas wells drilled here last year alone, more than in any other state except Texas. This rapid expansion has forced state regulators to confront a problem that has been overlooked as gas drilling accelerates nationwide: How will the industry dispose of the enormous amount of wastewater it produces?

Oil and gas wells disgorge about 9 million gallons of wastewater a day in Pennsylvania, according to industry estimates used by the DEP. By 2011 that figure is expected to rise to at least 19 million gallons, enough to fill almost 29 Olympic-sized swimming pools every day. That’s more than all the state’s waterways, combined, can safely absorb, DEP officials say.

"I don’t know that even our [water] program people had any idea about the volumes of water that would be used," said Dana Aunkst, who heads the DEP’s water program.

Much of the wastewater is the byproduct of a drilling process called hydraulic fracturing, or fracking, which pumps at least a million gallons of water per well deep into the earth to break layers of rock and release gas. When the water is sucked back out, it contains natural toxins dredged up during drilling, including cadmium and benzene, which both carry cancer risks. It can also contain small amounts of chemicals added to enhance drilling.

But DEP officials say one of the most worrisome contaminants in the wastewater is a gritty substance called Total Dissolved Solids, or TDS, a mixture of salt and other minerals that lie deep underground. Drilling wastewater contains so much TDS that it can be five times as salty as sea water.

Large quantities of TDS can clog machinery and affect the color, taste and odor of drinking water – precisely the problems reported along the Monongahela. While TDS isn’t considered particularly harmful to people, it can damage freshwater streams, which is what happened when TDS levels spiked in Dunkard Creek this month. West Virginia’s DEP is investigating whether TDS-laden wastewater from a coal mine near the creek could be to blame. It is also investigating reports that wastewater from natural gas wells may have been illegally dumped into the stream.