Democrats running for governor promise a greener Pa.

All said they'd seek to impose a severance tax on natural gas extracted from the Marcellus Shale.

All said they'd push to renew Growing Greener, a $625 million program approved by Pennsylvania voters in 2005 that has preserved open space, enhanced state parks, and cleaned up streams.

All said they'd enforce clean-air regulations, provide incentives for development of wind power and solar power, and work to remove storm water from municipal sewer systems.

The four Democrats running for governor in the May 18 primary sang in near-perfect harmony Thursday night while portraying themselves as friends of the environment and champions of the green economy.

The occasion was a debate at the Academy of Natural Sciences, sponsored in part by a coalition of 25 community groups. It was called the Urban Sustainability Forum.

The candidates, often tongue in cheek, stepped over one another to cast themselves to the audience of perhaps 300 people as the most eager to help the environment.

"I am the only candidate who walked to this forum tonight" - from Broad and Walnut Streets, a few blocks away - said Montgomery County Commissioner Joe Hoeffel, drawing a laugh.

"And I walked here from Pittsburgh," said Allegheny County Executive Dan Onorato, drawing a bigger laugh.

In answer to an inquiry about how he had to cut his energy consumption, State Sen. Anthony Hardy Williams brought up his wife, Shari, whom he described as "a fanatic" about the environment.

He said the couple had weatherized their house in West Philadelphia, had bought a hybrid car, had "changed all the lightbulbs," and had installed Energy Star-rated appliances.

"I don't even know half the stuff we've done."

The only major point of disagreement among the candidates had to do with the state's 31.2-cents-a-gallon gasoline tax.

Moderator Zack Stalberg, president of the Committee of Seventy political watchdog group, asked each man to say "yes" or "no" on whether he'd raise the tax to make up for the $450 million in anticipated revenue the state lost last week when the Federal Highway Administration refused to permit tolls on I-80.

"Don't know," said Williams.

"Yes," said Hoeffel.

"No," said Onorato.

"At this stage, no," said state Auditor General Jack Wagner.

The four agreed that the drilling for natural gas in the Marcellus Shale was providing an economic windfall for Pennsylvania - but one that poses an environmental hazard.

Each said revenue from a tax could beef up the state Department of Environmental Protection and help it enforce clean-water standards in drilling areas.

"I would re-fund all of DEP. It took a 28 percent hit in last year's budget," Onorato said. "I would also form an impact fund, which would raise funds from the severance tax to help municipalities with their impact."

Saying the state's vehicle fleet could be run on natural gas, Wagner said the massive gas find in the Marcellus Shale provided "an opportunity for us to get off of oil."

"I would like to see us maximize that opportunity," he said. "At the same time, I want to see that we protect our environment."

Hoeffel noted the environmental concerns of fracking, which uses water under high pressure to break up underground rock trapping the natural gas.

But he said fracking wasn't the only water-protection issue. He said rainwater runoff from drilling sites was also a problem.

"I want a moratorium on issuing any more permits until the industry is required to clean up the waste water they are generating," Hoeffel said. "Industry won't do it unless government makes them. As governor, I will."

Williams agreed that rainwater runoff from drilling was polluting streams. He said he also had concerns about fracking.

"There is a way to protect the environment without being oppressive to these companies," Williams said.