Christopher Smith, Associated Press
U.S. Fish and Wildlife Service biologist Cary Myler counts tiny Bruneau hot springsnails in December.

RENO, Nev. — Federal wildlife officials have agreed to consider federal protections for more than two dozen species of tiny snails in Utah, Nevada and California that environmentalists say are threatened by a big water pipeline project for thirsty Las Vegas.

Backers of the 300-mile pipeline said Tuesday they are not concerned that a federal listing of the aquatic mollusks would jeopardize the $3.5 billion project.

But opponents said the move bolsters their legal arsenal in what they expect to be another court battle aimed at stopping the transfer of billions of gallons of water a year from aquifers beneath east-central Nevada and western Utah.

The U.S. Fish and Wildlife Service said it found enough scientific evidence to move ahead with a yearlong status review of 32 species of Great Basin and Mojave Desert springsnails. The agency had been reviewing petitions submitted by the Center for Biological Diversity and others.

"The Southern Nevada Water Authority's pipeline scheme threatens not just these snails but also hundreds of other species to say nothing of water supplies for rural residents and future generations," said Tierra Curry, a biologist at the center who was among those who first petitioned for protection in February 2009.

Jill Ralston, U.S. Fish and Wildlife Service deputy supervisor for the state of Nevada, emphasized that the finding, to be published Tuesday in the Federal Register, did not mean the agency decided federal protection of the snails was warranted.

Rather, it was the "first step in a process and triggers a review of all available biological information," she said in a statement confirming the agency will review 32 springsnail species out of 42 that conservationists want listed.

J.C. Davis, spokesman for the Southern Nevada Water Authority, said the authority already has mitigation measures in place that would address any possible listing of the snails.

"It's certainly not a show stopper," Davis said. "It just means there are additional requirements under the Endangered Species Act."

The springsnails are found only in freshwater springs in Clark, Lincoln, Nye and White Pine counties in Nevada; Beaver and Millard counties in Utah; and Inyo County, Calif.

Rob Mrowka, an ecologist for the Phoenix-based center, said the new move by the wildlife service was significant because it verified legitimate concerns about the status of the snails and a number of other fish and wildlife species dependent on natural springs.

"Before, they could just blow us off," he said. "But once you get the review and they make a 90-day finding in your favor like this, that gives added impetuous for protection."

The water authority had the necessary water rights in hand but lost them a year ago when the Nevada Supreme Court sent the matter back to the state water engineer for a round of hearings later this year.

Meanwhile, the Bureau of Land Management was accepting public comment through Oct. 11 on a draft environmental impact statement as it considers granting the necessary right-of-way for the pipeline to be built. The draft statement said the proposal has the potential to affect 305 springs, 112 miles of streams, 8,000 acres of wetlands and 191,506 acres of scrub land wildlife habitat.

"I don't know of anybody who thinks the BLM is going to deny it, given the politics the way they are," Mrowka told The Associated Press. "What we really are doing is teeing it up for litigation."

"Once we get into court, it is going to be the Endangered Species Act that is going to trump a lot of the other issues," he said.

Mrowka said the pumping could result in a drop in the land surface of more than 5 feet over 525 square miles, as well as the generation of 34,742 tons of windblown dust per year created by the death of vegetation.

Davis said those concerns are based on "fairly speculative" assumptions about "potential possible impacts after 200 years of pumping, and treating those as though they are foregone conclusions."

"What they characterize as a water grab is nothing of the sort," Davis said. "We didn't seek it out. It is a matter of us asking permission to use water that the state says is available."