Ever since large-scale drilling for natural gas began in Pennsylvania's Marcellus Shale, environmentalists have been warning of the potential dangers, while the industry has touted its ability to do its work safely, cleanly and responsibly.
The signing a year ago of Act 13, the state's major overhaul of its shale gas regulations, does not appear to have quieted the debate.
"We're still looking at this as a severe environmental challenge," said Erika Staaf, a spokeswoman for PennEnvironment Research and Policy Center, a nonprofit with offices in Pittsburgh and Philadelphia.
For Patrick Creighton, spokesman for the Marcellus Shale Coalition, on the other hand, "Natural gas is a clear environmental winner."
As most Pennsylvanians now know, drilling in the Marcellus Shale involves "fracking," a method of freeing natural gas from porous rock formations by injecting wells with a potent mix of water, sand and industrial chemicals. It takes several million gallons of water to frack a single well.
Environmentalists say current safeguards aren't enough to keep frack chemicals and methane from contaminating drinking water and air.
"Families living in the shadow of gas drilling face explosions mere feet from their doorsteps, polluted tap water that is unsafe to drink, toxic fumes in the air they breathe, and more," Staaf's group, PennEnvironment, writes on its website.
Those concerns are vastly overblown, say industry and government representatives.
"No other state has added more staff, done a more comprehensive strengthening of its rules or more aggressively enforced its rules than Pennsylvania has," the state Department of Environmental Protection boasts in a statement posted on its website.
DEP's efforts to ramp up Marcellus Shale enforcement span two administrations, department spokesman Kevin Sunday said. It began under Democratic Gov. Ed Rendell and continued when Republican Gov. Tom Corbett took office in January 2011.
In 2010, DEP increased the number of well inspectors from 83 to 202, Sunday said. The following February, it finalized tougher regulations on well casing and cementing, he said.
The state's wastewater treatment plants offer a notable example of how regulations evolved. Under Secretary John Hanger, a Rendell appointee, DEP implemented regulations requiring plants accepting frackwater to treat it to a "drinking water" standard in order to receive a permit.
However, plants operating under older standards were grandfathered in until, following reports of high bromide levels in several rivers, Corbett's DEP secretary, Michael Krancer, in April 2011 called for a voluntary moratorium on drillers sending wastewater to the older plants, Sunday said.
"The industry got on board with that call practically overnight" and shifted to large-scale water recycling, he said.
Today, about 70 percent of frackwater is recycled, with some companies achieving 100 percent, he said. Drillers filter out contaminated sludge and ship it to landfills equipped to handle it, he said.
In implementing recycling, the industry was able to "turn on a dime," Creighton said: "That's impressive by any measure."
Act 13, signed by Corbett on Feb. 13, 2012, further strengthened environmental safeguards, Sunday said. It increased setbacks from waterways, tripled fines for environmental violations and widened the circumstances under which drillers are presumed liable for water contamination.
Environmentalists acknowledge some improvement, Staaf said, but consider Act 13 insufficient, and they object strongly to its ban on local municipalities enacting their own ordinances on the industry. That provision is now before the state Supreme Court for a ruling on its constitutionality.
Staaf's organization supports enacting regulations tighter than Act 13's and advocates a drilling moratorium during which that would happen. However, now that Act 13 has passed, there is little political appetite to reopen the issue, she acknowledged.
"So we're left with what we have," she said.
Pennsylvanians continue to be wary of fracking, polls indicate. A telephone poll conducted in the Pittsburgh area last fall found eight in 10 respondents consider drilling at least a slight danger to the environment and public health, and more than half consider it a moderate or significant threat.
Nevertheless, respondents supported drilling 45 percent to 25 percent, with 30 percent undecided, the poll found.
The Marcellus Shale Coalition has worked hard to create a positive public perception of the natural-gas industry, most recently taking out short ads before the movie "Promised Land" pointing audiences to its own "Learn About Shale" website.
"People have questions," Creighton said. "We have to answer them. That's our obligation as an industry."
A majority of Pennsylvanians support responsible drilling, he said.
DEP will be vigilant and will take whatever steps are needed to protect the public, Sunday said.
"We won't hesitate to make changes if needed," he said.