Barriers Along the U.S. Borders: Key Authorities and Requirements [November 18, 2016] [open pdf - 949KB]
"Securing the borders is an issue of perennial concern to Congress. Federal law authorizes the Department of Homeland Security (DHS) to construct barriers along the U.S. borders to deter illegal crossings. DHS is also required to construct reinforced fencing along at least 700 miles of the land border with Mexico (a border that stretches 1,933 miles), though Congress has not provided a deadline for its completion. Nor has Congress provided specific guidelines about the characteristics of such fencing (e.g., the height or material composition of the fencing) or other barriers that DHS may deploy. At this time, fence construction has largely been halted, though DHS still needs to deploy fencing along nearly 50 additional miles of the southwest border to satisfy the 700-mile requirement. [...] This report discusses the statutory framework governing the deployment of fencing and other barriers along the U.S. international borders."
CRS Report for Congress, R43975
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html