Environmental groups have announced their intention to sue the Texas Department of Transportation over how it has managed construction of its MoPac Intersections highway expansion project in Southwest Austin.

The construction will better connect northern Hays County with MoPac, smooth traffic into Austin and ease congestion on neighborhood roads. But concerns over its environmental impact and how it could create suburban sprawl have long made the road project a point of controversy.

Now, two environmental groups have announced their intent to sue TxDOT because, they say, the agency has not protected endangered cave salamanders that live under the highway.

They offered as evidence photographs taken by the Austin-based Save Our Springs Alliance, one of the groups suing. The photos show uncovered holes, created by highway construction, that lead to cave systems underground.

“They said that if they encountered some of these underground caves or voids that they would immediately cover them up and that just hasn’t been done,” Collette Adkins, a senior attorney for the Center for Biological Diversity, said. “The problem with leaving these voids open to the air is that sediments and polluted runoff from the area can make its way right down to where these endangered salamanders live.”

Save Our Springs Alliance and the Center for Biological Diversity hope a lawsuit will force TxDOT to consult with the U.S. Fish and Wildlife Agency on steps to protect the animals.

The filing of a notice of intent to sue is the first step in the process of filing a lawsuit under the Endangered Species Act, Adkins said. She said the groups would not sue if TxDOT agreed to work with the federal agency.

This is would be the second lawsuit filed by the Center for Biological Diversity against TxDOT over the project. The initial suit claimed the agency had not formulated a stringent enough plan to protect the endangered salamanders ahead of construction.

Highway expansion in southwest Travis County has long been a politically contentious issue, pitting southwest Travis and northern Hays County homeowners and commuters against environmental groups.

Adkins said the groups aren't trying to block the project with this most recent legal action.

“We recognize that this construction project is going forward,” she said. “We just want to make sure that the salamanders are protected.”

Spokespeople for TxDOT and the U.S. Fish and Wildlife Service both declined to comment, saying they could not speak about pending litigation.

The project is due for completion in 2021.