Emergency workers in Florida are trying to prevent the collapse of a large wastewater pond while evacuating the area to avoid a “catastrophic flood”, the state’s governor said.

Manatee County officials said the latest models show that a breach at the old phosphate plant reservoir has the potential to gush out 340 million gallons of water in a matter of minutes, risking a 20ft wall of water.

“What we are looking at now is trying to prevent and respond to, if need be, a real catastrophic flood situation,” Ron DeSantis said at a press conference after flying over the old Piney Point phosphate mine.

Authorities have closed off portions of US Highway 41 and ordered evacuations of 316 homes. Some families were placed in local hotels.

Wastewater Reservoir Leak
Ron DeSantis has given a news conference (Chris O’Meara/AP)

A jail one mile away from the pond is not being evacuated but officials are moving people and staff to the second floor and putting sandbags on the ground floor.

Manatee County administrator Scott Hopes said the models show the area could be covered with between 1ft to 5ft of water, and the second floor is 10ft above ground.

County officials say well water remains unaffected and there is no threat to Lake Manatee, the area’s primary source of drinking water.

The Florida Department of Environmental Protection says the water in the pond is primarily salt water mixed with wastewater and storm water.

It has elevated levels of phosphorous and nitrogen and is acidic, but not expected to be toxic, the agency said.

Wastewater Reservoir Leak
An emergency evacuation order was sent out to an area around Piney Point (Tiffany Tompkins/The Bradenton Herald via AP)

Crews have been discharging water since the pond began leaking in March.

On Friday, a significant leak that was detected escalated the response and prompted the first evacuations and a declaration of a state of emergency on Saturday.

A portion of the containment wall in the reservoir shifted, leading officials to think a collapse could occur at any time.

Mr Hopes said on Sunday that with new state resources, crews will be nearly doubling the amount of water being pumped out of the pond and taken to Port Manatee.

Currently about 22,000 gallons of water are being discharged per minute, and Mr Hopes said he expects the risk of collapse to decrease by Tuesday.

Early on Sunday, officials saw an increase of water leaking out, but Mr Hopes says it seems to have plateaued.

“Looking at the water that has been removed and the somewhat stability of the current breach, I think the team is much more comfortable today than we were yesterday,” he said. “We are not out of the critical area yet.”