They Built the Wall. Now Some in Texas Fear It May Fall Down.

“We’ve lived here all our lives so we know what a flood does,” said Mr. Cavazos, 77, a retired U.S. customs agent. “You don’t build on the riverbank.”

Engineers who studied the fence’s construction on behalf of the Justice Department reached a similar conclusion. Among the issues outlined in the 400-page report from the engineering firm Arcadis were that, in the event of a major flood, the fence “would effectively slide, overturn and become buoyant.”

The firm concluded: “The fence is likely not fit for use under all reasonably anticipated service loads,” meaning environmental conditions, such as snow, wind, rain, earthquakes and floods.

But the government did not take its case to trial, choosing instead to reach the settlement with Fisher. Among the stipulations agreed to by the Justice Department and Fisher were that copies of the engineering report be destroyed. Its conclusions were instead reported by ProPublica and the Texas Tribune. A copy was obtained by The New York Times.

A spokeswoman for the Justice Department declined to respond to questions about the settlement.

“Ultimately we think what would be the best for everyone involved is just to take it down, even for Fisher,” said Javier Pena, a lawyer for the National Butterfly Center, referring to Tommy Fisher, the owner of the company. “He did not intend for this fence to stay up forever, because if he did, he would have built it better.”

Mark J. Courtois, a lawyer representing Fisher and its subsidiary in the project, said the company stands behind the design and construction of the fence, disagreed with the “assumptions and modeling” of the government’s report, and “agreed to perform routine maintenance for the project as is required for all structures.”

The fence sits just outside a relatively urbanized portion of the border in the Rio Grande Valley, which has been among the top locations for illegal crossings. Around the time of its construction, more people crossed in the Rio Grande Valley sector than anywhere else in Texas, though more recently larger numbers have been recorded farther northwest, in and around Eagle Pass and El Paso.