This aerial photo shows a massive sinkhole Friday, Sept. 16, 2016, in Mulberry, Fla., that opened up underneath a gypsum stack at a Mosaic phosphate fertilizer plant. (Jim Damaske/The Associated Press) A large sinkhole has opened by a phosphate fertilizer plant near Tampa, Florida, pouring hundreds of millions of litres of contaminated water into a nearby aquifer.

The water contains a "slightly" radioactive by-product from the production of phosphate, called phosphogypsum.

We might not know what the consequences are until it is too late. - Bradley Marshall, Earthjustice

The sinkhole was discovered by a worker on Aug. 27, but the company responsible for the phosphate, Mosaic, waited three weeks to notify authorities.

So-called "gypsum stacks" are common in Florida. These are piles of waste material generated in the processing of some fertilizers. It's believed the chemicals in these stacks undermine the earth below which can lead to sinkholes.

An aerial photo of the sinkhole near Tampa that opened up underneath a gypsum stack at a Mosaic phosphate fertilizer plant. (Jim Damaske/ The Associated Press) Mosaic says the situation is under control, and "there is absolutely nobody at risk." But Bradley Marshall, an attorney with the non-profit environmental law office Earthjustice, is not convinced.

As It Happens host Carol Off asked Marshall about the situation:

Carol Off: What exactly is the stuff that is pouring into the sinkhole?

Bradley Marshall: What you have, as part of the phosphate mining process, is you create this phosphogypsum waste byproduct. And in Florida, because of the way the processing is done, it's actually radioactive. It creates this radioactive waste water that sits on top of these mountains of waste. And so that water that poured into that sinkhole, is actually radioactive. Hundreds of millions of litres of reprocessed water from the fertilizer plant in central Florida are likely to have seeped into the Floridan aquifer after the massive sinkhole opened up. (Jim Damaske/ The Associated Press) What you have, as part of the phosphate mining process, is you create this phosphogypsum waste byproduct. And in Florida, because of the way the processing is done, it's actually radioactive. It creates this radioactive waste water that sits on top of these mountains of waste. And so that water that poured into that sinkhole, is actually radioactive.

CO: The company Mosaic says it's only slightly radioactive.

BM: Well, I'm not going to get into how they characterize slightly, but I would be concerned about any level of radioactivity going into the aquifer which is the primary drinking source for 90% of Floridians.

CO: And that's where it's going?

BM: Yes, it's going into the aquifer.

CO: Directly in, like, it's going into the drinking water?

BM: Yes. It's going right into the Floridian aquifer which is the drinking water source for most people in Florida.

CO: The report from your department of environmental protection says that along with reviewing daily reports, it's performing frequent site visits to make sure a timely and appropriate response continues, it's safeguarding public health and the environment, and it's monitoring the process water to make sure it's ok. Does that reassure you?

BM: I think every step that they can do at this point is good, but no. The damage, in some ways, is done. Yes, the company can try and recover what waste water it can from the aquifer, but no matter what they do, they're not going to recover it all. We might not know what the consequences are until it's too late.

For more on the leak, listen to our full interview with Bradley Marshall of Earthjustice.