According to a Friday report by TIME magazine, the U.S. Navy may be planning to detain tens of thousands of immigrants (accused of illegally entering the country) in Concord, despite the fact that the Environmental Protection Agency [EPA] still lists the Concord Naval Weapons Station as a Superfund site, a designation reserved for some of the most toxic places in the country.

TIME cited a Navy draft memo that singled out potential detention locales in three states, including the Concord base, which could hold up to 47,000 people in what the publication describes as a proposed “tent city.”

The proposal calls for immigration camps that are “temporary and austere.”

The magazine cautions that “the military has not yet been ordered to construct these new detention facilities,” but cites the existence of the memo as an indication that the organs of the federal government are preparing to create new detention facilities on a large scale.

Dating to World War II, the Concord base—located in the largest city in Contra Costa County—went out of service in 2007, although gradual shutdown began years prior.

The federal government determined that decades of munitions storage had resulted in toxic conditions at the Weapons Station, and the EPA has designated it a Superfund site. According to the EPA website, longstanding cleanup efforts are not yet complete:

In November 2005, WPNSTA Concord was recommended for partial closure and realignment under the Base Realignment and Closure (BRAC) process. The final BRAC determination that was made resulted in about half of the facility (the Tidal Area) being transferred to the Department of the Army in 2008. The remaining area (the Inland Area) was closed, transferred and redeveloped. Initial actions such as wetland restoration and excavation of contaminated soils are helping to protect nearby populations and the environment. [...] To protect human health and the environment, site investigations and long-term cleanup are ongoing.

Potentially hazardous elements in the soil include lead, mercury, arsenic, and “unexploded ordinance.”

The EPA does report that “there are currently no unacceptable human exposure pathways” at the base and that the locale “may have redevelopment occurring on portions of the site and may be eligible for additional redevelopment.”

However, the Concord site’s report card also cautions about “expected groundwater contamination” and that “actions are still needed to address contamination.”

The city has frequently expressed a desire to redevelop the Weapons Station, and mega developer Lennar has planned a large mixed-use project there for years. Concord even offered the base as a potential site for Amazon’s new corporate headquarters in 2017.

But the station remains a Navy asset. In early 2017, a Navy profile on the base indicated it was still working “to make the property environmentally suitable for transfer.”

On the EPA’s 100-point Hazard Ranking System, the Concord base’s score is 50. Generally, a 28.5 or higher indicates toxicity sufficient to demand cleanup, and 50 is a greater than average score. For context, Treasure Island’s former Navy base is a 48.77.

The EPA, the Navy, and the city of Concord have not yet responded to Curbed SF’s queries about whether the base is appropriate for short-term occupation. The TIME report does not make clear which parts of the base detainees may occupy.

In response to reports, the city of Concord released the following statement on Friday:

The City of Concord is very concerned to learn of news reports that the Navy may be planning a detention center at the Concord Naval Weapons Station. The Navy has not communicated information to the City about any such plans, although we have reached out to them upon hearing these reports. While the City of Concord is currently negotiating to acquire and eventually develop the Naval Weapons Station, we do not have jurisdiction or control over that federally-owned property. Last September, the City of Concord passed a resolution affirming Concord’s commitment to being a welcoming, inclusive, tolerant and supportive community for all. We do not feel that a detention center within city limits represents those values.

Congressman Mike DeSaulnier, who represents the Concord area, called the proposal “absolute madness” on Friday, adding “I oppose it wholeheartedly” and “we will fight this in every way we can.”