Mosaic Co. on Wednesday proposed a fix for two adjacent leaks reported in October at its phosphogypsum stack in Bartow.
The fertilizer giant also stated it now believes two leaks are coming from below a plastic lining at the bottom of a 200-foot industrial wastewater stack in Polk County. It’s likely coming from the old stack, which Mosaic built vertical extensions on top of starting in 2001, according to their consulting engineers’ Jan. 21 report to state and federal regulators.
According to that memorandum, the fix will involve continuing what they are doing now, which is pumping the leaking as it comes out below the gypstack, into the lined interior of the gypstack. The fix will also include excavation of areas around the leaks and installation of piping and geotextile fabric. This material holds in materials but allows drainage.
Fixing the leak will start as soon as possible, said Mosaic spokesperson Jackie Barron. It will take about six to eight weeks.
Mosaic emphasized that its investigations show the gypstack is stable. Charlotte County officials and other opponents to Mosaic’s operations have asked whether the leak indicates the potential for another sink hole opening up underneath the 164 million gallons of industrial waste water in the stack. That is what has happened once in 1994 and a second time in 2016 to neighboring gypstacks.
“The gypstack itself remains structurally sound,” the company said in a written statement.
It’s not the current process water that’s leaking, Mosaic said. It’s what Mosaic calls remnant water, or water left over from operations before regulators required Mosaic to add a plastic liner to the stack. In general, phosphate manufacturing produces an acidic brew that Mosaic both draws from and adds to. The stack has a 55-acre crusty pool at the top.
“As part of our long term care obligations for the old stack we are required to collect that water as it slowly seeps out,” Barron told the Sun. “The closed stack perimeter collection drain collects the remnant water and returns it to the plant for use in operations.”
Mosaic first notified state regulators of a fast-flowing leak of its industrial waste water on Oct. 23. Calling it seepage 1 and 2, the company reported the leaks started out at 100 gallons a minute into a grassy area by the gypstack. Later, the flow dropped to 25 gallons a minute.
For three months, Mosaic has been trying to locate the cause of the leak. To keep the ongoing leak from polluting groundwater or wetlands, Mosaic has been pumping the pooling fluids into the adjacent gypstack.
“To date there have been no offsite impacts, nor are any expected,” Mosaic’s statement reads.
Charlotte County officials and citizens have been closely following this situation. The county’s drinking water supply is the Peace River, which begins some 60 river miles to the north, near Mosaic’s Bartow operations.
Asked about Mosaic’s plan, DEP responded with a written statement.
“Once we have evaluated the adequacy of Mosaic’s proposed corrective measures, the Department will determine if additional information is needed or additional actions are necessary to properly address the concentrated seepage area...The Department will continue to hold Mosaic accountable for meeting all permit, rule and reporting requirements. We are reviewing all information in order to ensure that Mosaic is fully complying with its regulatory requirements, and to determine any violations or necessary penalties or enforcement actions.”
Mosaic itemized steps it has taken so far to diagnose the problem:
• installing an earthen coffer dam
• pumping into the gypstack to prevent offsite migration
• a dye study that did not find the source
• installing piezometers or fluid pressure gauges
• water acidity measures, to identify what kind of water was leaking
• downstream water sampling to assess spread of the leak
• evaluation of a cutoff wall to prevent subsurface water migration
• evaluation of a closed stack drainage system
Earlier, DEP stated that Mosaic’s assessment and management of this situation could affect the discharge permit it needs to continue operations.