SAN DIEGO — Workers toiled in intense 95-degree heat here Tuesday, putting final touches on eight possible versions of President Donald Trump's long-promised border wall.

As an Oct. 26 deadline to finish the prototype border-wall designs drew near, The Arizona Republic toured the construction site a few dozen yards from the border that divides this city from neighboring Tijuana, Mexico.

U.S. Customs and Border Protection awarded eight contracts to six companies, including two from Arizona, to build the prototypes. Four are made of reinforced concrete, and another four incorporate additional construction materials. Construction began on Sept. 26, giving companies 30 days to finish.

By Tuesday afternoon, when CBP allowed The Republic access to the site, five of the wall designs had already been completed and were fenced off with caution tape.

But crews were still at work on others, installing vertical concrete panels on one design, using cranes and bulldozers to place them upright. Another two prototypes were in various stages of construction.

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The construction site is about 2 miles east of San Diego's Otay Mesa border crossing, in the foothills of the Otay Mountains.

At 30 feet, the designs dwarf the primary fence that currently marks the international boundary — it's made of rusted Vietnam War-era landing mats. They are nearly twice the height of the secondary metal-mesh fence, which ends near where the prototypes are being built.

Their height, officials said, is intended to make a statement to criminals and would-be unauthorized crossers: Stay away.

"The 30 feet is very impressive," said Mario Villareal, the division chief for the San Diego Sector Border Patrol. "What we're trying to accomplish is by putting tactical infrastructure on the border, by having all-weather roads, by putting Border Patrol agents on the immediate border is the deterrence."

Whether the border-wall prototypes keep people away, will be closely scrutinized in the coming weeks. After they are done, CBP will move to the "test and evaluation" of each of the eight structures.

What they look like ... so far

All of the finished prototypes, as well as the one that's nearly completed, employ concrete as the main construction material. But the designs of some vary greatly.

For example, one built by a Maryland company uses concrete at the base with the top two-thirds featuring blue metal panels. Another, built by an Alabama company, has a wide concrete base that gives way to a thinner frame halfway up the structure.

Notably, only one of the completed designs incorporates see-through features that would allow Border Patrol agents to monitor activity on the other side of the border.

Initially, Trump called for a solid reinforced concrete design, and several of the finished prototypes seemed to fit that description. Under advisement from CBP, the administration later included "see-through features" in its call for submissions.

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A second design by the Alabama company features metal bars for the first half of the prototype, narrowly spaced and resembling the bollard-style fencing commonly used at the border in Arizona's urban areas. But the top half has what appears to be solid concrete panels.

Border Patrol Agent Theron Francisco, who is stationed in the San Diego sector, said the ability to see across the border can be beneficial. It's an option they don't have now with landing-mat fencing in the area.

"It's good to be able to see through the south side. We can see them, they can see us," he said. "But in a way, it can be negative because we're always being watched. They always can see us. It goes both ways."

Arizona companies

Of the six companies CBP chose to build the prototypes, two are from Arizona. But as of Tuesday, only one of the companies had finished building its design.

Francisco said Tempe-based Fisher Sand & Gravel was among the first to complete construction of its prototype, building it "in a matter of days."

The concrete design is made up of three long, concrete frames that gently slope upward from the U.S. side, but are completely vertical on the south side. The concrete is a light tan, nearly the same color as the dusty soil it stands on.

Next to it, workers with the other Arizona company, KWR Construction of Sierra Vista, were digging the foundation for their design, which incorporates materials other than concrete.

On Tuesday, it was unclear what materials would be used or what the final design would look like.

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The cost of eight contracts ranges from $320,000 to $480,000. CBP has already appropriated the funds to pay for them.

However, funding for additional construction is still up in the air.

Last week, Trump issued new priorities on immigration. His revamped requests make a legal solution for the young undocumented migrants living in the U.S. known as "dreamers" conditional on Congress appropriating funds to build additional barriers on the border.

Those new fences would not look like the 30-foot prototypes in San Diego. Instead, they would resemble existing bollard-style fencing commonly seen in other urban areas of the border.

Officials said the new designs will be tested before any are considered for the actual border.

CBP said it will look at how effective the designs are in preventing people from climbing over, opening a hole in them or tunneling beneath them.

Based on those tests, the final design could "take key features from each prototype and develop one that will work for us along the border," Villareal said. "That is something that not only CBP will be looking at, but our engineers, is what is the best utility along the Southwest border?"

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