Pennsylvania officials gave approval Friday for a mining company to excavate 50 feet deeper in a Bucks County quarry that residents have blamed for causing sinkholes and lowering the water table near Primrose Creek.

The revised permit, granted by the Department of Environmental Protection to New Hope Crushed Stone Co., contains safeguards that were not previously in effect.

These include a provision that, in the event of "mud seams" or another anomalies, mining must be halted pending a state inquiry to make sure there is no adverse impact to the basin's "hydrogeologic balance."

In a news release, the agency said that the terrain surrounding the quarry was "naturally vulnerable" to sinkholes, but that the company would be required to repair any sinkholes "within and adjacent to the quarry's hydrologic zone of influence." That zone includes residential areas and property belonging to Solebury School, a private school serving grades seven through 12.

In a statement, company officials said the state's decision, which followed a 2-1/2 year review, was based on science.

"We are confident that this permit will not cause adverse environmental impacts and we are pleased with the outcome of this long process," the company statement said.

Kevin Morrissey, president of the Primrose Creek Watershed Association, felt otherwise. He said that quarry operations have interrupted creek flow and caused water levels to drop in some residential wells.

"It's a major concern for us," Morrissey said.

Solebury School head Tom Wilschutz also voiced concern, saying the permit posed a safety issue.

"We are troubled that the department apparently would ignore the scientific evidence that conclusively demonstrates that the massive dewatering that is part of the quarry's operations is the cause of collapse sinkholes on the Solebury School campus," Wilschutz said in an e-mail. "An expansion of mining by New Hope Crushed Stone will only worsen an already unacceptable situation."

The quarry has been in operation since the 1930s. The mining company is required to seek state approval every time it seeks to go 50 feet deeper into the ground. The new permit extension allows it to mine up to 170 feet below sea level.

Solebury Township has 30 days to appeal the permit. The board of supervisors will likely decide whether to do so during its Aug. 16 meeting, said Peter Augenblick, chairman of the board.

He said he had not yet seen the revised permit and thus declined to comment on it.

Contact staff writer Tom Avril at 215-854-2430 or tavril@phillynews.com.