The first phase of what is expected to be a lengthy and costly process to build additional segments of wall along the southwestern U.S. border ended as the deadline expired Tuesday afternoon for companies to pitch their ideas to the government.
The bidding process was to build 3-by-3-meter (10-by-10-foot) prototypes -- some made of concrete, some of any other type of material -- in San Diego, that the government will now evaluate for potential use along parts of the border, which stretches from southeast Texas to southwest California.
The government said it will spend two weeks selecting up to 20 competitors for a second round of competition for each type of wall. More than 400 companies showed interest in bidding, and several may win the chance to build the prototypes.
If the schedule outlined by U.S. Customs and Border Protection is not delayed, the second phase will begin in mid-April, with companies submitting cost analyses and more specific design plans.
Construction on the prototypes could begin in June, according to bid documents.
The specifications for the wall indicate new portions could be as low as 5 meters or as high as 9 meters (18 feet and 30 feet) -- "physically imposing in height," and resistant to people chipping away at it, CBP described in a notice to interested contractors.
The process began in mid-March, pushed by President Donald Trump, who campaigned regularly on the idea of building a wall along the border. Fencing, walls, surveillance towers and other barriers -- including natural, rugged terrain -- already exist.
The overall length of the wall segments to be added to the border remain unclear. But they must be resistant to climbing and take more than 30 minutes to bore through, according to bid documents -- enough time for border agents to locate the attempted breach.
They should also be "aesthetically pleasing in color" on the north, U.S.-facing side, the document specifies.
In a Congressional hearing Tuesday, two former CBP officials and a Texas professor testified before the Senate Homeland Security Committee about border fencing in the Southwest; they agreed with several senators that a wall is not the only solution to illegal migration across the border.
"There is not a one-size-fits-all for the border," said David Aguilar, former acting commissioner of the U.S. Customs and Border Protection.
He advocated for increased resources for CBP in the area, while Terence Garrett, a professor from the University of Texas Rio Grande Valley, advocated for improving conditions in the so-called northern "triangle countries" -- Honduras, El Salvador and Guatemala -- to curb the number of aspiring migrants traveling north.
The ongoing bid process focuses exclusively on the wall, but Ron Colburn, former deputy chief of the U.S. Border Patrol who also worked on the Arizona-Mexico border, told senators Tuesday that border security combines multiple techniques that change depending on what area is in question.
"Without tactical infrastructure, it's too weak. Without the right amount of manpower, it's too weak. And without the right mix of technology, it's too weak," Colburn said. "The links in the chain have to be equally strong. And it has to be the right mix."
"It's not going to be the same in San Diego as in Rio Grande Valley, South Texas," he added.
Paying for the wall
Trump promised to make Mexico pay for the wall, a proposal that country rebutted. Instead, the administration has requested that Congress approve $1.5 billion this year to start building a wall.
Estimates for the overall cost of adding miles of wall to the border are as high as $21.6 billion, according to a Reuters estimate, and that funding will require congressional approval.
Additionally, the government faces continued legal wrangling along the border to secure the land, often from private owners, to build additional barriers.