One certainty of Trump's wall: Big money

Today, as President Trump declares his intention to move forward with plans to build a barrier along the Mexican border, many of the details remain little more than a guessing game. Does Mr. Trump intend to build miles of concrete blocks, or fencing? Could parts of the wall be virtual, using technology like cameras and sensors to monitor the border, or be manned by drones? Will Mexico, as Mr. Trump has promised repeatedly, pay for it?

There is no doubt that if the United States moves ahead with plans for an ambitious border wall — one of the biggest infrastructure projects in decades, perhaps running in the tens of billions of dollars — it will be a boon for contractors.

An examination of failed efforts from the past highlights the potential gains for companies and potential pitfalls for taxpayers. Among the possible winners are construction firms, high-tech surveillance companies and cement manufacturers including, in what would be an ironic turn, one of Mexico’s largest materials companies.

“There’s no question that, when the government spends money on a big project like this, companies are going to make a lot of money,” said Joe Hornyak, a partner with the law firm Holland and Knight, who specializes in government contracting law. “There’s no question about that.”