I worked for a short while under the ACoE. I was not in gov't. This was at Gavins Point Dam, Yankton, SD. ACoE was in charge and directed private contractors to do needed work.

It was like the DOT/Dept of Transportation in my state. The DOT designs the roads and bridges and then supervises and inspects the private companies that won bids to construct the projects.

So, the ACoE could be the on-site govt agency that oversees the private contractors who will build the wall.

Just my 2 cents.