U.S. Customs and Border Protection is reportedly preparing to begin the construction of a stretch of wall in Texas along the U.S border with Mexico. The Associated Press reported that the Border Patrol planned to start moving heavy construction equipment to the Rio Grande Valley on Monday.

Here's what we know

This border barrier will be built using funds already set aside by Congress nearly a year ago.

In March 2018, Congress approved an omnibus spending bill that contained $641 million designated for the building of a 33-mile stretch of border fencing. The bill specified that the barrier could not be made out of concrete.

Since the bill was passed, President Donald Trump has started saying that his border wall, or barrier, would be built out of steel slats instead of concrete.

In September, CBP released plans to build an 18-foot-high, 25-mile wall in Hidalgo County, Texas. The Associated Press reported that this section of the wall will cut through a state park, the National Butterfly Center, and a hundred-year-old Catholic chapel. The construction will begin on federal land.

Environmental activists have expressed concern that the stretch of wall could upset local ecosystems. The Lower Rio Grande Valley National Wildlife Refuge, which is expected to be the site of part of the wall, is made up of land that was purchased as a corridor for local endangered species.

But what about the rest of the wall?

Congress has so far refused to approve the $5.7 billion in funding for a border wall that Trump has demanded. If a funding deal is not reached by Feb. 15, the government will shut down again.

Trump has said that if Congress doesn't pass a bill that includes the full amount of wall funding he requested, he would consider use an emergency order to have the military build the wall without congressional approval.