A worsening series of breaches in a 800-million-gallon holding pool at the Piney Point industrial site prompted Manatee County to evacuate residents within about a mile of the plant tonight.

• The Manatee County Sheriff’s Office and the Florida Highway Patrol closed off roads in the evacuation zone around U.S. 41 in Palmetto, per the Bradenton Herald, and the Red Cross has been called in to assist.

The latest: Acting Manatee County administrator Scott Hopes addressed reporters at a press conference around 9:20pm.

• Hopes said the water being discharged into Tampa Bay — at the rate of 22,000 gallons per minute, or 32 million gallons per day — is acidic and smells of ammonia, but said the pool supported wildlife like snook and ducks.
• "I wouldn't drink it," Hopes said when asked if it was contaminated.
• The property has long been considered "one of the biggest environmental threats in Florida history."

The backdrop: The old phosphate plant site, in operation from the 1960s until 2001, holds stacks of phosphogypsum, a byproduct of fertilizer production, and large pools of polluted water. As Selene reported Wednesday:

• A leak was discovered in the 77-acre process water pond last week.
• The Florida Department of Environmental Protection said draining it was the only way to prevent "a containment failure and catastrophic release."

The big picture: Site manager Jeff Barath's voice shook and he appeared to fight back tears as he spoke to the county commissioners about the situation.

• "There will likely be impacts in Tampa Bay," he told the commission.

What they're saying: USF geoscience professor Matthew Pasek initially told Axios that releasing small amounts of phosphate-contaminated water in the bay might not be so bad, but warned we’re now looking at irreversible damage.

• "Algae blooms followed by fish kills are the most likely thing," Pasek said. "It’s going to impact the food chain further down the line too. It’s unlikely to cause human damage, but there’s going to be a pretty stinky bay for a while."
• A state environmental spokeswoman wrote of the water: "It is slightly acidic, but not at a level that is expected to be concern, nor is it expected to be toxic," per the Tampa Bay Times.
• The DEP said in a statement that it's "dedicated to full enforcement of any damages to our state's resources and holding [property owner HRK Holdings] accountable for this event."