As gas-drilling operations proliferated in Pennsylvania's Marcellus Shale over the past couple of years, most of the hundreds of millions of gallons of briny wastewater they produced was eventually dumped into the state's rivers. Much of the rest is unaccounted for. That news, from a detailed look at the state's management of drilling wastewater by the Associated Press, should come as no surprise to readers of this site.

As we reported in October 2009, Pennsylvania was largely unprepared for the vast quantities of salty, chemically tainted wastewater produced by drilling operations in the Marcellus, the gas-bearing shale formation that stretches under that state and into West Virginia, New York and Ohio. While the state Department of Environmental Protection called for the fluids to be sent through municipal treatment plants, those facilities are largely unable to remove the salts and minerals, also known as Total Dissolved Solids (TDS), from the waste.

As our story noted, abnormally high salt levels in the Monongahela River in 2008 corroded machinery at a steel mill and a power plant that were drawing water from the river. The DEP suspected that drilling wastewater was the cause and ordered upstream treatment plants to reduce their output. But months later levels spiked again.

AP examined the DEP's first annual report of waste produced by drilling operations in Pennsylvania's Marcellus Shale area from July 2009 through June 2010. Among the AP findings:

  • More than 150 million gallons were discharged into rivers after passing through treatment plants in the 12-month period. Enough, as the AP put it, “to cover a square mile with more than 8 1/2 inches of brine.”
  • More than 50 million gallons, or about one-fifth of the total waste fluid, was unaccounted for because of “weakness” in the state's reporting system or incomplete filings from drilling companies.

The AP report says researchers still don't know whether high TDS levels are harmful to humans or wildlife. But the analysis found that some public water utilities had exceeded the federal limit for levels of cancer-causing trihalomethanes, which can form when chlorine in drinking-water treatment systems combines with bromide, which can be present in drilling waste.

As we reported back in 2009, the federal EPA recommends against discharging drilling wastewater into rivers, but it allowed Pennsylvania to continue the practice because more stringent regulations were in the works. The DEP announced new limits on TDS discharges in August, but they apply only to new and expanding facilities. The department has not yet responded to ProPublica's questions about the number or nature of any new treatment plant applications, so it's unclear to what extent these new standards are actually being practiced.

Another solution, which DEP secretary John Hanger and drilling companies say is already in the works, is to encourage companies to reduce waste by reusing wastewater in new wells. Hanger told the AP he thinks about 70 percent of fluids are now being reused.

But as we reported in December 2009, part of the reason drillers are able to achieve such high rates of reuse is that much of the fluid they pump into gas wells never comes back to the surface. When as much as 85 percent of the water and chemical mixture remains in the ground, drillers can dilute what little comes back with fresh water and reuse it. While that solves the issue of discharging briny water into rivers, it raises a separate set of questions about the implications of leaving fracking chemicals underground.

As the AP notes, industry claims of higher levels of waste-recycling can't be verified until the next DEP report is released, in mid-winter. Until then, Hanger called for “daily vigilance” of rivers and streams to ensure standards are being met.