The wall is expensive.
The Government Accountability Office found that single-layer pedestrian fencing could cost approximately $6.5 million per mile. In addition, millions would have to be spent on roads and maintenance.
The easiest parts of the border fence have been built, according to Marc Rosenblum, formerly of the Migration Policy Institute and the current DHS Deputy Secretary of the Office of Immigration Statistics. The estimated cost of the remaining border wall segments are between $15 and $25 billion, with each mile of fencing costing $16 million.
According to the Fiscal Year (FY) 2017 DHS budget, $274 million was spent on border fence maintenance. Based on that expense, one can extrapolate that if fencing is built on the final two-thirds of the Southern border, the maintenance costs will triple to more than $750 million annually.
In FY 2006, appropriations for building and maintaining border infrastructure were $298 million, and then jumped to $1.5 billion in FY 2007 to pay for the fencing mandated in the Secure Fence Act. FY 2016 appropriations were $447 million.
The federal border agencies have not asked for a wall.
Outgoing Commissioner of U.S. Customs and Border Protection (CBP) Gil Kerlikowske said in January 2017, “I think that anyone who’s been familiar with the southwest border and the terrain ... kind of recognizes that building a wall along the entire southwest border is probably not going to work,” adding that he does not “think it is feasible” or the “smartest way to use taxpayer money on infrastructure.”
The head of the National Border Patrol Council, a union representing 16,000 Border Patrol agents which endorsed President Trump during his campaign, said, “We do not need a wall along the entire 2,000 miles of border.” He went on to say, “If I were to quantify an actual number, I would say that we need about 30 percent. Thirty percent of our border has to have an actual fence [or] wall.” The existing 650 miles make up more than 30 percent of the 2,000 mile border.
According to an internal U.S. government study obtained by Reuters in April 2016, CBP believes that more technology is needed along the border to create a “virtual wall.” The agency requested better radios and more aerial drones, but only 23 more miles of fences.