During the first Trump administration, ponds at the San Bernardino National Wildlife Refuge in Arizona dried up after crews pumped millions of gallons of water to mix cement.

Now, construction across the region has started again. The 30-foot wall is going up in places workers didn’t get to the first time around, and a second barrier is going up where a wall already exists.

CBP calls it a “smart wall,” which includes new technology like sensors, lighting and cameras. Congress gave the administration nearly $47 billion to finish the project.

The wells are on federal property, within a 60-foot strip of land that runs along the international boundary known as the Roosevelt Reservation. In April, Customs and Border Protection sent a letter to the state engineer’s office that said the federal government is “immune” from state law that requires a permit to pump groundwater.