The Army Corps of Engineers began building 15 miles of border fence along the Barry M. Goldwater Training Range in Yuma, Ariz., yesterday, the Army’s civilian installations boss announced Thursday.

The fence, which will cost $50 million, will replace existing easily penetrable mesh fencing on the southern border with Mexico, where crossings have forced some shutdowns of pilot and ground crew training.

“When incursions occur and illegal border crossers get into that area, the ranges must close,” Jordan Gillis, the assistant Army secretary for energy and installations, told reporters. “That delays the training exercises. It diverts our time and our resources and ultimately impacts readiness.”

Gillis could not provide the number of incursions that have shut down the range over the past year.

The project will be paid for by military construction dollars that were not specified for another project and uncommitted planning and design dollars. The 15-mile stretch was not part of the 450-mile southwest border fence built during the first Trump administration, though that project was also paid for with reprogrammed military construction dollars originally destined for facilities on military bases.

Construction began Wednesday at the western edge of the project, Brig. Gen. John Lloyd, USACE’s South Pacific Division commander, told reporters, and is slated to cover 40 panels of fencing a day. 

In January, he added, another crew will start at the eastern edge, doubling the number of 8-feet-by-32-feet sections erected per day. The fence should be complete in April, he said, while construction of an access road for Customs and Border Protection will continue through August.

A video announcement of the project posted Thursday by the Pentagon shows construction workers tagging the first section of fencing. One wrote “For Charlie,” a nod to recently assassinated anti-immigrant political pundit Charlie Kirk.

Lloyd said his command is “looking into” the defacing of government property, but said he couldn’t attribute the tags—some of which were names—to anything other than commemorating the first section of the fence.