HARRISBURG — A Republican state lawmaker who fears injection wells used to dispose natural-gas drilling waste may trigger earthquakes and imperil Pennsylvania’s water supply wants to halt the practice until additional studies are conducted.

The move by freshman Rep. Cris Dush, of Indiana County, comes on the heels of a U.S. Geological Survey report linking injection wells to earthquakes in five states, including Ohio — where much of Pennsylvania’s fracking waste is mechanically thrust thousands of feet underground. Critics worry that the waste might leak from the well shafts on the way down. And there is increasing evidence that the pressure from pumping waste into the rock is contributing to a spike in earthquake activity across the country.

Dush’s idea also comes as Pennsylvania’s use of injection wells slowly picks up speed as natural-gas drilling companies seek ways to eliminate the millions of gallons of wastewater remaining after wells are fracked.

Pennsylvania drillers in 2014 got rid of 147 million gallons of briny, polluted water by injecting it into disposal wells — mostly in Ohio disposal wells. State Department of Environmental Protection records show that wastewater from fracked wells in 25 Pennsylvania counties went to 45 injection disposal wells in 2014. Only three of those wells were in Pennsylvania — in Warren, Clearfield and Somerset counties.

Those living in Youngstown, Ohio, in December 2011 got a jolt when the ground began to tremble from a magnitude-4 earthquake linked to an injection well that was disposing natural-gas drilling waste.

Between 1973–2008, an average of 21 earthquakes of magnitude-3 and larger hit the central and eastern United States per year, the USGS found.

This rate jumped to an average of 99 earthquakes magnitude-3 or higher per year in 2009–2013.

And it’s getting worse.

In 2014, there were 659 earthquakes measured as magnitude-3 or higher in the central and eastern United States.

Earthquakes in the magnitude-3 to 4 range are large enough to be felt by people, but small enough to cause significant damage.

But Dush, the Indiana lawmaker, notes that earthquake concerns are just one of the reasons that Pennsylvanians need to take a second look at injection wells. There are environmental concerns, chiefly with the potential threat to drinking water supplies, he said.

In Pennsylvania, the federal government takes the lead on oversight of injection wells. But DEP must sign off on the well permit.

There are four new injection well plans approved by the federal Environmental Protection Agency, but still awaiting the blessing of state regulators. That includes an injection well proposed by PGE in Indiana County that was initially approved by state and federal regulators. But last month the state DEP yanked the permit after complaints from neighbors.

The controversy in Indiana County helped convince Dush that Pennsylvania needs to hit the pause button on the expansion of injection wells.

“I’ve been listening to people on both sides and in four months, I don’t think I’ve gotten enough information,” he said. “I don’t think the public is informed enough either.”

Dush said he’s not opposed to the growth of the natural-gas industry. But there might be better ways to dispose of the waste. The drilling industry already estimates that as much as 90 percent of the wastewater is reused. Dush said that type of water recycling is probably a better option than pumping the waste into injection wells.

Opposition to the Indiana County injection well has been led by the East Run Hellbenders Society, a group founded by 71-year-old Judy Wanchisn.

The group’s name is an homage to the secretive amphibian that lives in the Little Mahoning Watershed, the area in which PGE hopes to operate its disposal well.

Wanchisn said she learned off the proposed well when a former township supervisor gave her a public notice about the plan.

“It kind of fell in my lap and I couldn’t let it go,” she said.

Wanchisn said she became alarmed when she read Propublica reporting about other problems with injection wells. The investigative website examined government records and found that 1 of 6 injection wells checked between 2007 and 2010 had been cited for well integrity violations.

Concerns about what’s underground were only aggravated by concerns about problems above ground, she said. The Indiana County site is accessible only by traveling winding country roads, leading to worries that trucks will crash and spill their loads into environmentally-significant waterways, she said.

“It’s just not a good place for an injection well,” she said.

Wanchisn pointed to the state Clean Streams Law in making her successful appeal to get DEP to pull the permit.

The state environmental agency had never examined injection well permits through the prism of the Clean Stream Law before, said DEP spokeswoman Amanda Witman.

When Wanchisn’s group made their case, “in an abundance of caution DEP rescinded the permit,” Witman said.

A spokeswoman for PGE said the company would not comment because of pending litigation in the dispute. The company sued after the East Run Hellbenders Society convinced the Grant Township supervisors to pass a local ordinance banning injection wells. Arguments in that case were supposed to take place later this month, but the judge postponed that hearing after DEP pulled the permit for the well.