MULBERRY, Fla. (WTSP) -- About five months after a massive sinkhole opened at Mosaic’s New Wales plant in Mulberry, the company has begun filling it. The process is called grouting. They’re essentially filling the sinkhole with a mixture of gravel and concrete.

In an email, the Florida Department of Environmental Protection said, “The initial grouting phase will stabilize the base of the sinkhole, which is critical for moving forward with closure of the sinkhole opening.”

When the sinkhole opened last August, millions of gallons of radioactive water from the fertilizer plant leaked into Florida’s aquifer.

People who live near the plant became worried their drinking water might be contaminated. Mosaic offered free well water testing and bottled water to anyone who requested it.

As of right now, the DEP says no wells were contaminated because of the sinkhole.

Still, residents are worried. Joyce Hunter said her well hasn't been tested since September and she wouldn't expect contaminants to show up until months or years later.

"I don't drink the water. I don't cook with the water. I use bottled water altogether," she said. "I do shower in the water and I probably will start to glow one day."

The company began looking into ways to fill the sinkhole shortly after it opened. They found the widest spot is about 152 feet, and the gypsum that was at the top was about 220 feet below ground. Gypsum is a byproduct of making fertilizer.

Mosaic said they hope to have the sinkhole filled as early as May.