The Florida Department of Environmental Protection and Mosaic struck back Friday against allegations by two retired government hydrologists that they should have noticed a potential sinkhole forming beneath Mosaic's Mulberry fertilizer plant a year before it caused contaminated water to leak into the aquifer.
State and company officials contend that hydrologists based their conclusions on incorrect data and said the Tampa Bay Times should not have published a story about their allegations.
"The allegations … are fundamentally wrong," Mosaic said in a statement.
At issue is the data from a monitoring well at the Mulberry plant, the largest fertilizer manufacturing plant in the world. A sinkhole opened up beneath a phosphogypsum stack at that plant in 1994, draining a pond of contaminated water into the aquifer. As a result, the DEP required Mosaic to install monitoring wells around the site to check for future problems.
In 2015, one of those wells detected a 40-foot jump in the water level of the aquifer.
The married hydrologists, Don Rice and Mary Hrenda, who retired from the U.S. Geological Survey and New Jersey Department of Environmental Protection, respectively, said that sudden jump was a sign that solid material from inside the gypsum stack had begun falling into the aquifer, signaling the start of the sinkhole that Mosaic detected in August 2016.
But Mosaic and DEP officials contend that because the well that detected that big jump in the aquifer was located at a different gypsum stack — one the company has been working to close down — that Rice and Hrenda's assertions are wrong.
"The water level increases . . . were observed in a location that is in no way related to the recent sinkhole," a Mosaic statement delivered via email said.
DEP officials made a similar point in their statement, which was emailed to reporters on Friday.
"The data they are referring to is from the north stack, which while continuously monitored and intact, has been closed and non-operational for nearly 12 years," the agency said.
The information from the report that Rice and Hrenda used "was carefully reviewed by DEP staff to ensure compliance with Florida's environmental regulations," the agency said.
Rice and Hrenda defended their conclusions, saying the location of the well does not matter. The aquifer isn't segmented, they said, but connected. They said something made the water level jump as if something big had been dropped down into it.
"If I saw a 40-foot rise in the water level, I'd go, 'Whoa, what's going on?' " Rice said.
Mosaic's statement said its workers were pouring grout into the closed stack. Those variations in the water level "were expected and intended" and were "subject to DEP's oversight," Mosaic's statement said. That prompted Rice to ask why they were putting grout in it. The Times asked Mosaic that question on Friday but did not receive a response.
As a result of the analysis of DEP data by Rice and Hrenda, environmental group Suncoast Waterkeeper sent a letter Friday to Gov. Rick Scott, Florida Attorney General Pam Bondi and the federal Environmental Protection Agency, accusing Mosaic and the DEP of negligence and demanding an investigation.
The statements from Mosaic and the DEP did not sway the Suncoast Waterkeeper from its demand for an investigation into whether the two could have done something to prevent the polluted water from being dumped into the aquifer.
"I don't believe, and I don't think the public believes, a thing Mosaic and FDEP say any longer," Waterkeeper's leader, Andy Mele, said.
The dispute over the well data follows a public uproar last fall after news broke that the sinkhole had occurred in August but neither the DEP nor Mosaic had informed the plant's neighbors or the public about it for three weeks.
The August sinkhole gulped down 215 million gallons of slightly acidic contaminated water, dropping it into the aquifer just as the 1994 sinkhole did.
Mosaic officials subsequently apologized for the secrecy. But DEP officials said they were merely following state law, which did not require telling anyone in the public until the pollution was detected beyond the boundaries of the plant's property. Gov. Rick Scott has called for changing that law.
Mosaic is seeking permission from Manatee County to expand its mining footprint there, and the August sinkhole has become a part of critics' arguments against approving the project. The County Commission is scheduled to vote Feb. 15.
Contact Craig Pittman at [email protected] Follow @craigtimes.