During a 2008 construction push, U.S. Customs and Border Patrol (CBP), without informing Mexico, built a 5-foot concrete barrier inside a storm-water tunnel that undocumented migrants used to move between Nogales, Sonora, and Nogales, Arizona, effectively creating an underground dam. Citing its authority under the “Real ID Act of 2005,” the Department of Homeland Security waived environmental review for the project under the National Environmental Policy Act (NEPA).
That July, monsoon rains flooded eight feet deep on the streets of Nogales, Sonora, buckling roads, destroying 578 homes, 45 cars, and causing $8 million in damages. Two people drowned. The flooding caused a total of $8 million in damage and state officials declared the damaged part of the city a disaster zone.
Adding insult to injury, it turned out that the barrier was built on the Mexican side of the border and was constructed without notifying the International Boundary and Water Commission, according to agency spokesperson said Sally Spener. The commission requests that any agency doing work on the border that could affect storm drainage send it plans.
A week after the flooding, federal officials gave permission for the cities of Nogales, Arizona and Nogales, Mexico to remove 1.5 feet from the concrete wall.
The flooding was later found to be linked to the storm drain that CBP had installed earlier that year, which had effectively created an underground dam.
All of this is to say that: 1) arbitrarily waiving environmental laws like NEPA is anathema to responsible planning; and, 2) government actions have historically had serious, often unanticipated consequences that deserve a fair accounting.
 Trump’s Border Wall Could Cause Deadly Flooding in Texas. Federal Officials Are Planning to Build It Anyway.” Texas Monthly. September 25, 2018. Available at:
 6 ways the border wall could disrupt the environment.” National Geographic. January 10, 2019. Available at: