McALLEN, Texas — A group of Texas Democratic congressmen want more details about preliminary plans to build a section of President Donald Trump’s proposed border wall through a federal wildlife refuge, saying such a move could do serious damage to the environment.

Federal officials have told landowners and local officials that they intend to build on about 3 miles (nearly 5 kilometers) of the river levee that runs through the Santa Ana National Wildlife Refuge.

The Trump administration has proposed 60 miles (96 kilometers) of wall construction in the Rio Grande Valley, the region of farmland and border cities at the southernmost point of Texas. The U.S. House has passed a budget proposal with $1.6 billion in funding to start construction in South Texas as well as 14 miles (22 kilometers) in San Diego.

Advocates are concerned that the Santa Ana refuge, a key sanctuary for birds and endangered wildcats, could be cut off at its northern edge by the construction of a wall, reducing visitor traffic and disrupting wildlife.

“A wall cutting through the refuge could do serious environmental and economic damage, and the American public deserves transparency for what could be billions of taxpayers’ dollars spent on a wall along the U.S.-Mexico border,” said the letter, sent Friday to Elaine Duke, the acting secretary of the Department of Homeland Security.

The letter asks the DHS to confirm it has targeted the refuge and to answer whether it will comply with environmental reviews and a host of laws regulating endangered species and water use.

The congressmen signing the letter are Joaquin Castro of San Antonio, Henry Cuellar of Laredo, Lloyd Doggett of Austin, Vicente Gonzalez of McAllen, Beto O’Rourke of El Paso, and Filemon Vela of Brownsville.

It’s unclear how quickly construction could begin if the Senate agrees to funding. The Trump administration could waive environmental reviews and other laws to expedite construction in Texas, as it already has for San Diego. And since the U.S. government controls the refuge, it would likely not have to file claims to take control of the land.

Scott Nicol, co-chair of the Sierra Club Borderlands campaign, told The Monitor of McAllen that he’s asked Customs and Border Protection officials to hold public meetings instead of inviting local officials to smaller gatherings.

“The landowners and the people who live right there next to the wall should be able to show up and give their input and find out what’s coming to their community,” Nicol said.