Whenever Poland Spring announces its intention to bottle many more millions of gallons of Maine’s groundwater, environmentalists sound the alarm.

The corporation’s intention to build another plant — possibly in the Lincoln area — that could extract another 175 million gallons per year from an aquifer has, predictably, fanned fears that nearby wells or the entire aquifer will be sucked dry.

Here’s what we know — and don’t know — about the worries surrounding the expansion of Poland Spring, which is owned by the food and beverage giant Nestle.

Could Poland Spring deplete Maine’s groundwater?

No.

Each year, 25 trillion gallons of rain fall on the state. Ten to 20 percent of that enormous amount makes its way underground, replenishing Maine’s aquifers, according to Ryan Gordon, a hydrologist with the Maine Geological Survey.

In 2010, 36 billion gallons of water were extracted from Maine for human use. That included the 768 million gallons pumped out by bottled water companies, Gordon said.

Last year, Poland Spring bottled around 900 million gallons of water, less than 1 percent of the state’s groundwater, according to Thomas Brennan, Poland Spring’s senior natural resource manager.

Could Poland Spring bottling plants dry out nearby wells and deplete streams?

Experts disagree.

During droughts, bottling plants could dry up wells and wetlands or deplete the streamflows in the immediate area, according to Matthew Davis, chair of the Earth Sciences Department at the University of New Hampshire.

That fear was on the minds of Mainers near Poland Spring extraction sites during last summer’s drought. Laurie LaMountain, a Denmark resident who lives next to an extraction site said her well dried up last summer for the first time since it was installed in 2005. Several other Denmark residents had the same problem, she said.

However, Brennan insisted that the bottler’s pumping did not dry up private wells in Denmark.

Gordon, the state hydrologist, said during the drought he checked each of the company’s test wells that measure how the aquifer being tapped is being affected by the bottling operation. He found those test wells were at normal levels, meaning Poland Spring’s bottling operation was not causing the groundwater to dry up.

But Davis said that even with testing it is difficult to know what is or is not caused by water extraction. “A lot of times the water is coming out of fractured bedrock and it’s very difficult to predict or to prove that a pumping well has had a specific impact,” Davis said. “You don’t know the plumbing of the fractures. You don’t know the cause and effect.”

Does the state have any control over Poland Spring’s bottling activities?

Yes, but the control is very limited.

Poland Spring controls water under land it owns. But to get authorization to build a new bottling plant, the company must show state officials that the new operation will not harm surrounding water supplies.

The company needs approval from the Maine Drinking Water Program, Public Utilities Commission, the Maine Department of Environmental Protection and the Land Use Planning Commission when it’s in unorganized territories, Gordon said.

The Maine DEP typically checks testing wells at a proposed extraction site to see how the surrounding area would be affected, said Mark Margerum, an environmental specialist for the department.

After a permit is issued, DEP reviews test well data sent to it by Poland Spring, he said. During droughts, the Maine Geological Survey will check the company’s test wells itself.

Nisha Swinton, senior organizer for Food and Water Watch, said she wants stronger regulation of water extraction and says the state ought to have control over all of Maine’s groundwater.

“We should protect those groundwater resources for the communities here in Maine and not for the multinational corporation that comes in, takes it out for free and bottles it out,” Swinton said.