LEWISBURG — Forty-five people, nearly double the usual turnout for a League of Women Voters’ speaker-luncheon, came out Tuesday to hear a Bucknell University geology student discuss the complex ramifications of drilling for natural gas through the mile-deep Marcellus Shale.

The audience listened intently to her rapid-fire presentation and offered a brisk barrage of questions at the end until they were cut off by time constraints.

Molly Pritz, who studies the wastewater by-product of hydrofracking, the method of extracting natural gas trapped under the shale, detailed its potential to deplete water supplies, contaminate water, pollute air and destroy established ecosystems.

The process of hydrofracking, forcing water and chemicals into the shale to crack open fissures that will release gas, uses enormous amounts of water, Pritz said. Water withdrawals necessary can reduce stream flow, deplete aquifers and impact the habitat of wetlands downstream.

Chemicals added to the water to facilitate the process can be spilled or leak into the fissures and go deep into the ground. Scientists don’t know how to track this seepage, she said.

Solids, sludge and natural salts, which are by-products of the process, will add to landfill mass. And some of it is radioactive due to naturally occurring radioactivity.

Liners used in holding ponds and dumps eventually need to be disposed of as well.

“We’re talking about a lot of salt, a lot of sludge and a lot of solids that have to be disposed of,” she said.

Aquifer contamination is a possibility, which would impact the quality of drinking water sources and the ecosystems that depend on the water.

A damaged site can be rehabilitated, but cannot be returned to its mature state, she said.

Then there are the roads. “Hundred and hundreds of trucks are used to bring the water to each well pad,” she said.

Pipelines need to be built, which affect the ecology and aesthetics of an area, she added.

Air quality is another concern. The internal combustion engines running all those trucks will add to the emissions and create greenhouse gases, which are implicated in global warming.

Well drilling itself adds dust to the air and streams.

East Buffalo Township Supervisor-elect Tom Zorn asked if the impacts have been studied in other locations where this type of drilling is well-established.