As debate in the nation’s capital has focused on health care, Russia and secret tapes, President Donald Trump’s signature proposal — building a “big, beautiful wall” on America’s southern border — has faded from the spotlight.

But preparations are quietly moving forward to start the first wall-related construction on California soil in the next few months, in an effort to translate campaign rally applause lines into cold, hard concrete.

Construction is scheduled to begin on four to eight wall prototypes by “late summer,” acting Border Patrol Chief Carla Provost said at a recent congressional hearing. They’ll each be 30 feet long and 18 to 30 feet high, and designed to withstand climbing, tunneling and attempts to break through.

The slices of wall will go up in a dusty patch of federal land on the edge of the San Diego sprawl, several hundred feet north of the border. The site, at the foothills of the Otay mountains and about two miles east of the warehouses of San Diego’s Otay Mesa neighborhood, is surrounded by scrubby grassland. Across the border are busy, poor Tijuana neighborhoods.

More than 600 companies expressed interest in the project earlier this year, and several hundred submitted bids, ranging from a utopian hyperloop track tracing the border to a wall covered in solar panels.

Each prototype will be built by a different company or team of companies, with the best design winning its builder a contract to build the first section of the actual wall — an arrangement that could have been ripped from Trump’s reality TV days.

U.S. officials have been tight-lipped about the details of the construction effort, saying only that they’re in the final stages of selecting the contractors who will build the prototypes.

But locals say it’s clear that preparations are already being made on the ground. Jill Holslin, a photographer and San Diego State lecturer who has gone hiking in the area for years, said she’s noticed increased construction activity in the past few weeks, with workers leveling land and marking off what appears to be a staging area with orange construction tape.

Congress has not agreed to Trump’s requests to budget $2.6 billion to start building a new wall across the entire border — and there’s definitely no sign that Mexico will pay for it, as Trump repeatedly promised his supporters during the campaign. But $20 million for the prototypes was included in this year’s budget.

Most companies that are in the final rounds of selection aren’t talking about their proposals. But Dennis O’Leary said his Arizona business DarkPulse Technologies is one of the finalists. The company’s sensors would be embedded within a concrete wall, O’Leary said, and would allow officials to immediately detect intrusions or tunneling with precision “in the millimeters, not the meters,” he said. The sensor technology has also been used to detect leaks in pipelines, he said.

“It’s just fiber and a laser,” he said. “It doesn’t care what your skin color is or who you voted for.”

DarkPulse is teaming up with two other construction firms, which O’Leary declined to name but said were Fortune 100 companies.

There could be consequences for any company involved in the project. The California Senate passed a bill this month banning California from entering contracts with any company involved in building the wall. Berkeley and Oakland have passed similar laws, and San Francisco and Los Angeles are debating whether to follow suit.

Nontheless, dozens of small businesses in California have listed their interest in subcontracting on the project.

Susie Bozzini, general manager of Safety Engineering International near Santa Barbara, said she hoped to supply the winning contractor with her technology to prevent construction vehicles from rolling over when driving in rocky, off-road conditions.

Politics doesn’t factor into the equation, she said: “I don’t think we really need a wall, but I’m a businessperson and I have sales goals to meet.”

“As for the political part, I don’t understand it,” said Robert Acosta, the CEO of AD Improvements, a Southern California demolition and excavation company that’s looking to become a subcontractor on the project. “As an American, we’ve got to protect the homeland. And I’ve got employees, and they’ve got to feed their families.”

The construction site is sure to become a target for protests, and O’Leary said if his company is selected to build a prototype, he’d hire substantial private security.

Meanwhile, the contracting process has also attracted some hoping to make a political statement. Ted Levinson, a social enterprise investor who lives in San Francisco, said he registered himself as a federal contractor and submitted a series of anti-wall cartoons to the request for proposals. “My submission was not selected,” he said dryly.

Getting the prototypes built would be a powerful morale boost at a time when Trump’s legislative agenda, from repealing Obamacare to reforming the tax code, has racked up few successes, said Dan Schnur, a former Republican strategist.

“The first time that pictures of him in front of a wall prototype go up on the internet, his supporters are going to go absolutely crazy with delight,” Schnur said. “Then even if the wall ultimately never gets built, it’s the fault of all the career politicians in Washington.”

But even as the prototypes move forward, the project is already running into legal trouble. The Center for Biological Diversity, a conservation group in Oakland, says the mini-walls would irreversibly damage habitats of endangered species, and they’ve filed a formal notice to sue the federal government under the National Environmental Protection Act and the Endangered Species Act.

The construction would especially impact the Quino checkerspot butterfly, a dainty insect with distinctive burnt orange-and-white checkered wings, said Jean Su, a lawyer with the center. The Quino was added to the federal endangered species list in 1997, as its natural environment in Southern California was eaten up by development. Wall construction would destroy even more of the butterfly’s habitat and disrupt its natural mating routes, which meander back and forth between Mexico and the United States.

There’s no evidence that the feds have done any kind of environmental review on the project. A U.S. Customs and Border Protection spokesman declined to say whether a review had taken place, but said the agency “works diligently to integrate responsible environmental practices — including incorporating sustainable practices — into all aspects of our decision-making and operations.”

The federal government is “being incredibly secretive about something that could have a huge impact on both humans and wildlife,” Su said. “If they’re failing to do an environmental review on the prototypes and they’re about to start construction in a few weeks, it’s a very bad omen for what that means for the larger border wall.”

Once the prototypes are complete, the first construction on the actual wall would also be in San Diego, replacing what is now a double-layered fence. Beefing up the wall in the San Diego area is important, Provost, the CBP head, told members of Congress, because the local segment of the border has been “breached over 800 times.”

“That is our priority area,” Provost said. “The current fence that is in that area is insufficient.”