FILE - In this July 24, 2014, file photo, a bend in the Rio Grand is viewed from a Texas Department of Public Safety helicopter on patrol over in Mission, Texas. The U.S. government is preparing to begin construction of more border walls and fencing in South Texas' Rio Grande Valley, likely on federally-owned land set aside as wildlife refuge property. Heavy construction equipment is supposed to arrive starting Monday. A photo posted by the nonprofit National Butterfly Center shows an excavator parked on its property.
FILE - In this July 24, 2014, file photo, a bend in the Rio Grand is viewed from a Texas Department of Public Safety helicopter on patrol over in Mission, Texas. The U.S. government is preparing to begin construction of more border walls and fencing in South Texas' Rio Grande Valley, likely on federally-owned land set aside as wildlife refuge property. Heavy construction equipment is supposed to arrive starting Monday. A photo posted by the nonprofit National Butterfly Center shows an excavator parked on its property. Eric Gay, Pool, File AP Photo
FILE - In this July 24, 2014, file photo, a bend in the Rio Grand is viewed from a Texas Department of Public Safety helicopter on patrol over in Mission, Texas. The U.S. government is preparing to begin construction of more border walls and fencing in South Texas' Rio Grande Valley, likely on federally-owned land set aside as wildlife refuge property. Heavy construction equipment is supposed to arrive starting Monday. A photo posted by the nonprofit National Butterfly Center shows an excavator parked on its property. Eric Gay, Pool, File AP Photo