Wayne Cornelius, a researcher on Mexican migration weighed in on the Wall idea in early 2017:
Construction of the wall will inevitably be plagued by a swarm of daunting engineering, environmental and legal obstacles. And even if Trump succeeds somehow in pouring concrete from sea to shining sea, such a physical barrier would not prevent undocumented migrants from entering the United States, as decades of fieldwork-based research have demonstrated.
A formidable obstacle course of pedestrian and vehicle barriers covering about 700 miles of the border has already been built during the last 24 years. Ten surveys conducted by me and my field research team in Mexico and California from 2005 to 2015 found that these existing fortifications prevent fewer than one in 10 would-be unauthorized migrants from gaining entry into the U.S.
Inevitably, people-smugglers would take clients over, around or under Trump’s new wall, or guide them through legal ports-of-entry using false documents or concealed in vehicles, charging higher fees for their trouble.
Independent estimates from MIT researchers and others of initial construction costs run from US$25 billion to $40 billion – a far cry from the $12 billion to $15 billion claimed by Senate majority leader Mitch McConnell – plus $500 million to $750 million per year to keep the barrier repaired.
Most of these estimates, however, also exclude the costs of land acquisition (nearly all of the affected land is in private or state hands), technological upgrades like seismic sensors to detect tunneling, temporary housing for a construction crew of 1,000 workers (if the project is to be completed in Trump’s first term) and litigation to resolve suits brought by landowners, environmental groups, Indian tribes and others affected by the project.