Last year, nearly 1,000 trucks hauling 15,769 tons of Marcellus Shale waste were stopped at Pennsylvania landfill gates after tripping radioactivity alarms.
The trucks were pulled to the side, wanded with hand-held detectors and some of the material was sent to laboratories for further evaluation. In the end, 622 tons were shipped to three out-of-state landfills specifically designed to dispose of hazardous and radioactive materials.
But most of the flagged waste was eventually allowed past the gates. It was safe enough to be buried along with other waste as long as it stays below the annual limit, the Department of Environmental Protection and landfill operators deemed.
The increase in radiation alarms going off at landfills has mirrored the growth in Marcellus Shale activity, and the DEP has launched a yearlong study of radioactive Marcellus waste to determine any risks involved in its transportation or disposal.
The agency's bureau of waste management also has formed a working group and charged it with developing protocol for tracking rejected loads, for telling gas operators how to characterize the waste, for developing waste acceptance criteria for landfills, and for clarifying how well sites and waste treatment plants should handle residual waste.
So far, neither the DEP nor the landfill owners are alarmed.
To put it into perspective, the alarms flagged only 1 percent of all landfill-bound Marcellus waste last year, according to state figures. Shale gas operators reported sending just under 1 million tons of waste to Pennsylvania landfills in 2012. The majority of that was drill cuttings -- chunks of earth pulled out of the well during the drilling process -- but there was also flow-back water, frack sand and other fluids that were turned into sludge for disposal.
It's these sludges that experts say are most likely contributing to elevated radiation counts.
The radioactive material in Marcellus waste is naturally occurring. It's mostly radium, a product of uranium decay, and it has been underground for millions of years in the Marcellus formation. Dredging earth and gas out of the ground brings up the radioactive elements.
Since 2002, all Pennsylvania landfills have been outfitted with radiation detectors following concerns about medical waste ending up in the municipal waste stream. All trucks arriving at the facilities pass through a gate topped with a sensor that takes a reading inches away from the top of the truck.
According to the DEP, Marcellus sludge is three times more likely to trip alarms than solid shale waste. Last year, 224 loads of drill cuttings elicited alarms at landfills, while 773 loads of sludge did the same. So far this year, 211 loads of sludge and 124 loads of drill cuttings tripped alarms, the DEP said.
But the number of times an alarm is tripped doesn't tell the whole story.
Landfill sensors are particularly sensitive and able to detect even small levels of radioactivity, said Erika Deyarmin, a spokeswoman for Waste Management Corp., which operates 17 commercial landfills in Pennsylvania.
Usually, if a load is really radioactive, it never makes it to a landfill because the oil and gas company or wastewater treatment plant that first scans that waste at their site knows it will be rejected, she said. In such cases, the company must come up with another disposal option.
The increase in radioactivity at landfills may be a product of how Marcellus waste treatment has changed over the last few years.
In 2011, radioactivity concerns centered around water. Back then, oil and gas companies were still taking their waste to municipal wastewater treatment plants and to commercial plants that were discharging into the state's waters.
In the summer of 2011, the DEP collected and analyzed sediment from the PA Brine wastewater treatment plant in Indiana County and found levels of radium 226 in the discharge pipe that was 44 times the drinking water standard. Twenty meters downstream of the discharge point, levels were still 66 percent above the standard.
Similar results were found at several other facilities, as revealed in a settlement between the Environmental Protection Agency and the company earlier this year.
In April 2011, the PA Brine plant and all such plants in the state had been told not to accept Marcellus wastewater, but the radioactive elements found in PA Brine's soil were remnants of prior discharges.
Kelvin Gregory, an assistant professor at Carnegie Mellon University who works on Marcellus water issues, said the peak of radioactivity in wastewater comes after the initial gush of flow-back water comes to the surface after fracking. Radium concentrations are highest in produced water, a term that describes the brine that continues to flow out of the well for long periods of time after that well starts producing gas.
In a survey of flow-back and produced water at 46 Marcellus sites, Mr. Gregory found radioactivity increases for two months on average, then he saw plateaus.
Whether the level stays at that high concentration forever or tapers off at some point isn't yet clear, Mr. Gregory said. The wells haven't been producing long enough to tell.
Examples of highly radioactive waste from the Marcellus are rare so far.
"The cases where we get a very hot load are very few and far between," said John Poister, a spokesman for the DEP's southwestern district.
But every once in awhile, it happens.
In April, a truckload from Rice Energy arrived at Max Environmental's Yukon Landfill in Westmoreland County and set off the alarm. The waste was deemed too radioactive.
The company shopped it around to a few landfills, but no one would take it, Mr. Poister said. Eventually, the truck went back to the source while arrangements were made to transport the waste to a specialized disposal site in Idaho.
Why was Rice's load so much hotter than others?
"That's a question for the [DEP] study," Mr. Poister said.
"We've taken quite a bit of drill cuttings at our Yukon facility this year, and only one truck triggered the radiation alarm," said Carl Spadaro, environmental general manager of the Yukon landfill. "Other landfills have had alarms triggered quite a bit."
Yukon accepts about 90,000 tons of waste annually and just last month amended its permit to be able to accept waste that trips radiation alarms.
"We didn't do this to bring in a lot of [radioactive] waste," Mr. Spadaro said. "We did this to level the playing field."
Yukon competes with two other landfills within a 5-mile radius.
"The biggest concern is exposure of a landfill worker during unloading and somebody who's handling material," Mr. Spadaro said.
The exposure level allowed at Pennsylvania landfills is a quarter of the EPA's public radiation dose limit of 100 millirem per year.
"This is equivalent to about two chest X-rays," said Kevin Sunday, a former spokesman for the DEP.state - marcellusshale
Anya Litvak: firstname.lastname@example.org or 412-263-1455.