Donald Trump may have confused people recently about whether he supports mass deportation. But there’s one thing he’s been consistent about: building a wall along the southern border. And having Mexico pay for it.

In an interview aired Aug. 23, Fox News host Sean Hannity asked the Republican presidential nominee how long it would take to build the wall, from start to finish.

"Almost immediately," Trump answered. "Now if you would believe it, you know, they were going to build the wall a while ago, not so long ago, like in '06. And they couldn't get environmental impact statements. Can you believe it? Okay. Now we got lucky because it was such a little wall, it was such a nothing wall, no, they couldn't get their environmental -- probably a snake was in the way or a toad or…"

We were curious about wall plans from a decade ago and whether environmental impact statements hindered its construction, as Trump’s statements suggest.

Trump’s campaign did not respond to our requests for more information. But immigration experts referred us to the Secure Fence Act of 2006, signed into law by President George W. Bush.

Secure Fence Act

The act called for the construction 700 miles of additional fencing along the U.S.-Mexico border. It also authorized the use of more vehicle barriers, checkpoints and lighting to deter illegal immigration, and the use of advanced technology such as satellites and unmanned aerial vehicles.

Bush said the new law would make borders more secure and hailed it as "an important step toward immigration reform."

The act also required the Department of Homeland Security to install at least two layers of reinforced fencing along some stretches of the border. That was amended, however, through the Consolidated Appropriations Act of 2008, which got rid of the double-layer requirement.

Environmental impact statements

So there was a 2006 law that sought to increase fencing around the border. But it didn’t face hurdles from environmental impact statements.

That’s because the REAL ID Act of 2005, passed by Congress, gave the Secretary of Homeland Security the authority to "waive all legal requirements" that may get in the way of construction of barriers and roads along the border.

In 2008, then Secretary of Homeland Security Michael Chertoff, used his authority to waive environmental reviews.

"Congress and the American public have been adamant that they want and expect border security," said Chertoff in an April 2008 New York Times report. "We’re serious about delivering it, and these waivers will enable important security projects to keep moving forward."

The secretary also waived requirements under the National Environmental Policy Act and Endangered Species Act, according to Melinda Taylor, who directs an energy and environmental law center at the University of Texas and who co-wrote a paper on the environmental impacts of the border wall between Texas and Mexico.

The waivers were not without controversy.

"The environment was certainly a major issue that opponents of the wall brought up," said Cassie Williams, spokesperson for Federation for American Immigration Reform, which favors reduced immigration. But DHS did not need an environmental impact statement because of the Congress-approved waiver, Williams said.

In July 2008, DHS released an Environmental Stewardship Plan, analyzing potential environmental impacts of the fence and plans to mitigate them.

While there were environmental concerns related to fence construction, "it’s simply false that environmental requirements or issues impeded wall construction," said Denise Gilman, a clinical professor and director of the immigration clinic at the University of Texas School of Law.

Gilman believes it’s appropriate to call the fencing a wall because it’s clear that it was supposed to keep people out. Segments built are generally 18-feet high, she said.

Rebecca Hamlin, assistant professor of legal studies at University of Massachusetts, Amherst, said environmental concerns were raised at the border, but believes money is what has halted additional construction, not environmental impact statements.

A 2009 U.S. Government Accountability Office report noted that for fiscal years 2006 through 2009, the Secure Border Initiative program -- designed to secure borders and curb illegal immigration -- received about $3.6 billion. About $2.4 billion of that amount was allocated to complete about 670 miles of vehicle and pedestrian fencing along the roughly 2,000-mile border.

That same report found that pedestrian fencing accounted for 140 of the miles Customs and Border Protection had completed by Oct. 31, 2008, averaging $3.9 million a mile. Vehicle fencing costs averaged $1 million a mile.

"The per-mile costs to build the fencing varied considerably because of the type of fencing, topography, materials used, land acquisition costs, and labor costs, among other things," the 2009 report said.

Our ruling

Trump said, "They were going to build the wall a while ago, not so long ago, like in '06. And they couldn't get environmental impact statements."

The Secure Fence Act of 2006 called for the construction of an additional 700 miles of fencing along the U.S.-Mexico border. While there were environmental concerns related to the construction, the Secretary of Homeland Security waived required environmental reviews in order to proceed with construction.

Trump’s statement suggests a wall or barrier was not built due to inability to get environmental impact statements.

Trump’s statement contains an element of truth but ignores critical facts that would give a different impression. We rate it Mostly False.