The American Wall, to be built in 21 segments at strategic points along the Rio Grande, must be able to withstand a crash by a 10,000-pound (4,545-kg) vehicle traveling at 40 miles per hour (64 kph), but also be “aesthetically pleasing,” the agency said.

The wall is part of a federal plan to build 700 miles of walling along the U.S.-Mexico border.

South Texas Border Wall 2010

The U.S. Customs and Border Protection agency said the wall would mostly be built on river levees, but also would cross private land and encroach on state parks and the Lower Rio Grande Valley National Wildlife Refuge. The refuge is considered one of the most biologically diverse wildlife sanctuaries in the nation and environmentalists say the fence could harm endangered species such as ocelots and jaguarundi found there.