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CONCORD — The crowd was itching for a fight Wednesday inside Concord City Hall, holding signs saying “Bring families together” and drawings of children behind bars. Then a cautious optimism swept through the standing-room only crowd, fed by an email from Contra Costa County Sheriff David Livingston that said there were no plans “at this time” to use the former Concord Naval Weapons Station to house as many as 47,000 immigrant detainees.

“I was recently advised by California Office of Emergency Services high-ranking officials that the U.S. Department of Homeland Security has said there will be no relocation camps established in Concord or anywhere in California. FYI at this time,” Livingston wrote to county supervisors, according to a city of Concord email.

The message brought relief — and yet another layer of uncertainty — to the fate of Concord’s long-shuttered naval base that turned up late last week in a draft memo, obtained by TIME.com, on a list of sites the military was studying to house immigrant detainees to cope with President Trump’s “zero-tolerance” policy to arrest anyone caught trying to enter the country illegally at the U.S.-Mexico border.

“It is important not to let our guard down, as one tweet can change things,” said U.S. Rep. Mark DeSaulnier, D-Concord, whose office was still working Wednesday to confirm the proposal was off the table.

The news came hours before outraged residents packed a special City Council meeting to discuss how to deal with the issue. The Navy continues to remain guarded about its plans, but local and state officials expressed relief about Livingston’s update. All concurred that a tent city would cause major problems at the base, which still has contamination issues and is destined for major residential and commercial development.

At the meeting, Concord official Guy Bjerke, who coordinates the city’s plan to redevelop the base, said Navy officials have continued to say their initial memo was simply an effort to prepare options in the event the Homeland Security Department asked them to house immigrants.

Standing room only crowd inside chamber for detention center discussion pic.twitter.com/o62EzJleAD — Matthias Gafni (@mgafni) June 27, 2018

Most speakers Wednesday voiced appreciation for the city’s quick condemnation of the proposal and expressed opposition to President Trump’s immigration policies.

“Thank you so much for your great news today. It gives us hope,” said Ady Olvera, a member of Concord Communities Alliance, speaking to the council during public comment. “I want to invite the community to continue to bring your concerns because while this impacts Concord, it still impacts the whole nation.”

Concord’s stance is part of the growing resistance to the Trump administration’s “zero-tolerance” policy, which has led to the detention of thousands of undocumented immigrants, the separation of many children from their parents and has left the government scrambling to find a way to house them all while they await hearings or deportation.

“The detention centers are anti-American and a blight on our honor and contrary to what we have struggled to create,” Mayor Edi Birsan told the crowd.

In Concord, the consensus among city leaders was that the former weapons station should not be an option. The city has been negotiating for the transfer of 2,300 acres of land to begin a massive development there and was months away from taking over portions of the property after 12 years of planning and finally choosing a master developer.

DeSaulnier said he he was pleased when he heard the news that the plans had been scrapped but that he was still waiting to hear back from Department of Defense officials to get written confirmation.

“As we advised the administration, the Concord Naval Weapons Station is an unsafe and inhabitable environment, and to propose housing almost 50,000 people there was both dangerous and immoral. We fought this proposal along with our local officials and dedicated community and will continue to fight against the inhumane and unjust policies proposed by this administration,” DeSaulnier said in a statement.

State Sen. Steve Glazer said he has “serious concerns” about the detention center idea and said there are better options. The Family Case Management Program, recently terminated by the Trump administration, was able to place immigrants in safe housing for a cost of $36 a day per family, Glazer said. The program had compliance rates of 99 percent for detainees to make court hearings and immigration appointments, he contended.

“Experience shows that far more humane alternatives to detention are available at a fraction of what it would cost to build and operate detention camps,” Glazer said in a statement. “I urge the Trump administration to reconsider its current policies and implement a humane and compassionate system for processing immigration cases and settling immigrants while their cases are being decided.”

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Concord Councilwoman Laura Hoffmeister said she was cautiously optimistic that the detention center proposal was off the table.

“We need to hope for the best and prepare for the worst and remain vigilant,” she said.