— The natural gas boom gripping parts of the U.S. has a nasty byproduct: Wastewater so salty, and so polluted with metals such as barium and strontium, that most states require drillers to get rid of the stuff by injecting it down shafts thousands of feet deep.

Not in Pennsylvania, one of the states at the center of the gas rush.

There, the liquid that gushes from gas wells is only partially treated for substances that could be environmentally harmful, then dumped into rivers and streams from which communities get their drinking water.

In the two years since the frenzy of activity began in the vast underground rock formation known as the Marcellus Shale, Pennsylvania has been the only state allowing waterways to serve as the primary disposal place for the huge amounts of wastewater produced by a drilling technique called hydraulic fracturing, or fracking.

State regulators, initially caught flat-footed, tightened the rules this year for any new water treatment plants but allowed any existing operations to continue discharging water into rivers.

At least 3.6 million barrels of the waste were sent to treatment plants that empty into rivers during the 12 months ending June 30, according to state records. That is enough to cover a square mile with more than 8 inches of brine.

Risk debated

Researchers are still trying to figure out whether Pennsylvania’s river discharges, at their current levels, are dangerous to humans or wildlife. Several studies are under way, some under the auspices of the Environmental Protection Agency.

State officials, energy companies and the operators of treatment plants insist that with the right safeguards in place, the practice poses little or no risk to the environment or to the hundreds of thousands of people who rely on those rivers for drinking water.

But an Associated Press review found that Pennsylvania’s efforts to minimize, control and track wastewater discharges from the Marcellus Shale have sometimes failed.

For example:

• Of the roughly 6 million barrels of well liquids produced in a 12-month period examined by The AP, the state couldn’t account for the disposal method for 1.28 million barrels, about a fifth of the total, because of a weakness in its reporting system and incomplete filings by some energy companies.

• Some public water utilities that sit downstream from big gas wastewater treatment plants have struggled to stay under the federal maximum for contaminants known as trihalomethanes, which can cause cancer if swallowed over a long period.

• Regulations that should have kept drilling wastewater out of the important Delaware River Basin, the water supply for 15 million people in four states, were circumvented for many months.

In 2009 and part of 2010, energy company Cabot Oil & Gas trucked more than 44,000 barrels of well wastewater to a treatment facility in Hatfield Township, a Philadelphia suburb. Those liquids ultimately were discharged into a creek that provides drinking water to 17 municipalities with more than 300,000 residents. Cabot acknowledged it should not have happened.

People in those communities had been told repeatedly that the watershed was free of gas waste.

“This is an outrage,” said Tracy Carluccio, deputy director of the Delaware Riverkeeper Network, an environmental group. “This is indicative of the lack of adequate oversight.”

Situation watched

The situation in Pennsylvania is being watched carefully by regulators in other states, some of which have begun allowing some river discharges. New York also sits over the Marcellus Shale, but Gov. David Paterson has slapped a moratorium on high-volume fracking while environmental regulations are drafted.

Industry representatives insist that the wastewater from fracking has not caused serious harm anywhere in Pennsylvania, in part because it is safely diluted in the state’s big rivers. But most of the largest drillers say they are taking action and abolishing river discharges anyway.

Cabot, which produced nearly 370,000 barrels of waste in the period examined by the AP, said that since the spring it has been reusing 100 percent of its well water in new drilling operations, rather than trucking it to treatment plants.

“Cabot wants to ensure that everything we are doing is environmentally sound,” said spokesman George Stark. “It makes environmental sense and economic sense to do it.”

All 10 of the biggest drillers in the state say they have either eliminated river discharges in the past few months or reduced them to a small fraction of what they were a year ago. Together, those companies accounted for 80 percent of the wastewater produced in the state.

The biggest driller, Atlas Resources, which produced nearly 2.3 million barrels of wastewater in the review period, said it is now recycling all water produced by wells in their first

30 days of operation, when the flowback is heaviest. Half of the rest is now sent to treatment plants, but “our ultimate goal is to have zero surface discharge of any of the water,” said Atlas Senior Vice President Jeff Kupfer.

How much wastewater is still being discharged into rivers is unclear. Records verifying industry claims of a major drop-off will not be available until midwinter.

A number of gas drillers have also begun recycling wastewater in other parts of the country to cut down on the costs of disposal and of obtaining the fluids needed for new fracturing jobs.

Still, with dozens more energy companies at work in the state’s surging gas industry, more than 2,400 wells drilled and work starting on 5,400 more, operators of the largest of the state’s 16 most commonly used treatment plants say they haven’t lost much business. Records verifying company claims of a major dropoff in river disposal will not be available until midwinter.

University of Pittsburgh scientist Conrad Volz, who has been studying the environmental effect of the wastewater discharges, said he had student researchers in the field this fall documenting a steady flow of brine-filled tankers arriving at plants on the Monongahela River south of Pittsburgh, and on the Blacklick Creek, 17 miles northwest of Johnstown.

“We’ve been taking pictures of the trucks,” he said. “We know it’s still happening.”

Researchers are still trying to figure out, he said, whether the wastewater discharges, at their current levels, could cause serious environmental harm.

The municipal authority that provides drinking water to Beaver Falls, 27 miles northwest of Pittsburgh, began flunking tests for trihalomethanes regularly last year, around the time that a facility 18 miles upstream, Advanced Waste Services, became Pennsylvania’s dominant gas wastewater treatment plant.

Trihalomethanes aren’t found in drilling wastewater, but there can be a link. The waste stream often contains bromide, a salt, which reacts with the chlorine disinfectants used by drinking water systems to kill microbes.

That interaction creates trihalomethanes.

The EPA says people who drink water with elevated levels of trihalomethanes for many years have an increased risk of getting cancer and could also develop liver, kidney or central nervous system problems.

Gas drilling waste isn’t the only substance that can cause elevated trihalomethane levels. Pennsylvania’s multitude of acid-leaching, abandoned coal mines and other industrial sources are also a major factor in the high salt levels that lead to the problem.

Beaver Falls plant manager Jim Riggio said he doesn’t know what is causing the problem, but a chemical analysis raised the possibility that it might be linked to the hundreds of thousands of barrels of partially treated gas well brine that now flow past his intakes every year.

“It all goes back to frackwater,” he said.

Other contaminants

Fracturing involves injection of millions of gallons of water mixed with chemicals and sand deep into the rock, shattering the shale and releasing the gas trapped inside. When the gas comes to the surface, some of the water comes back, too, along with underground brine that exists naturally.

It can be several times saltier than sea water and tainted with fracking chemicals, some of which can be carcinogenic if swallowed at high enough levels over time.

The water is also often laden with barium, which is found in underground ore deposits and also used by drillers as a bit lubricant. It can cause high blood pressure if someone ingests enough of it over a long period of time.

Particles in the water are also often tainted with radium, a naturally occurring radioactive substance, and strontium, a mineral abundant in rocks, earth, coal and oil.

The amount of produced water varies from well to well, but in Pennsylvania it has been running at around 1 to 2 gallons for every 10 gallons injected into the ground.

When companies recycle their wastewater, they lightly treat it for particles and some other substances, combine it with fresh water, and reuse it in a new fracturing job.

Operators of the treatment plants handling the bulk of the waste still being discharged into Pennsylvania rivers say they can remove most of the toxic pollutants without much trouble, including radium and barium.

“We have been able to do it carefully. We have been able to do it safely,” said Al Lander, President of Tunnelton Liquids, one of the state’s busiest treatment plants. The facility, near Saltsburg, Indiana County, treats both drilling water and acid draining out of an abandoned mine.

“In some respects, it’s better than what’s already in the river,” he said of the water his plant discharges into the Conemaugh.

“What we are putting into the river now is far cleaner and far more eco-friendly than what was running in naturally from acid mine drainage.”

The one thing that can’t be removed easily, except at great expense, he said, are the dissolved solids and chlorides that make the fluids so salty.

In 2008, workers at two plants that draw water from the Monongahela River, U.S. Steel in Clairton and Allegheny Energy, noticed that salt levels had spiked so high that equipment was corroding. State regulators suspected it was related to gas drilling waste being discharged through sewage treatment facilities.

Today, however, it remains unclear how much of a role the wastewater had in the salt spike.

Some research has suggested that abandoned coal mines, which release far greater pools of polluted water into the state’s rivers than gas drilling, were predominantly to blame for the problem.

Salt levels have spiked again on the Monongahela since 2008, even though relatively little drilling wastewater is now being discharged into that waterway.