Mosaic Fertilizer executives and their contractors are scrambling to find new places to store millions of gallons of highly acidic water being drained from a slumping 140-acre lake atop a towering waste pile in St. James Parish.

Company executives are trying to drain the lake to remove pressure from the weight of all that water on a 1,500- to 2,000-foot-long wall of gypsum that has been slowly shifting to the north, potentially endangering streams below. 

Tapped for use Thursday afternoon following a brief halt in pumping, an emergency reservoir that normally holds less contaminated rainfall runoff — not the acidic process water inside the threatened lake — has been designated the next holding pen for the lake water, company officials and state regulators said.

The first pond to receive the process water is already full.

Known as the "west cell," that pond is located on a lower level of the shifting waste pile and began taking the process water Jan. 14. The pond, which Mosaic finished building in May as part of an earlier planned expansion, is now holding 180 million gallons, Mosaic officials said. 

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Russell Schweiss, a spokesman for Mosaic, said Friday that the 110-acre emergency reservoir put into use Thursday will buy the company time while it tries to finish construction of a second new containment pond on the waste pile. Known as the "east cell," that pond is expected to be finished and ready for use sometime in March, permit records show. 

"And once the east cell's ready for water, we'll have storage for everything," Schweiss said.

The juggling act among ponds and lakes scattered through Mosaic's 3,300-acre site at its Uncle Sam complex near Convent underscores the amount of hazardous water that must be contained while the company also tries to prevent a catastrophic release of that water that could threaten the Blind River and the freshwater back swamps to the east.

Heavy rain during the past three years and, in particular, the past 6-7 months, has stressed the system of ponds at the Mosaic facility on the east bank of the Mississippi River, state regulatory documents show. The company told state regulators in late November that the rainfall totals since 2015 were two feet greater than what its required "extreme" weather modeling had projected. 

While Mosaic officials can't say how much water they must remove from the 140-acre lake atop the waste pile to stop the gypsum wall's slow slide, they don't think they'll have to remove all 720 million gallons of water remaining inside.

The emergency reservoir pulled into action can hold another 200 million gallons of water. Earlier this week, construction also began on a dirt berm designed to brake the leading edge of the creeping wall of gypsum, Schweiss added.

Marylee Orr, executive director of the Louisiana Environmental Action Network, said gypsum piles in St. James and also in Ascension Parish have been a concern of hers and other environmental groups for decades. She noted two gypsum stacks owned by other companies along La. 30 in Geismar raise constant worries about runoff and leachate potentially escaping to reach the Spanish Lake swamp basin.

"Those gypsum stacks are kind of a reminder of us in another era where there wasn't, we felt, quite as much regulation ... way back," Orr said, "where people weren't quite as much of a watchdog and really understood exactly what was happening, but they do now."

Mosaic also owns now closed and capped legacy gypsum piles at its Faustina plant in western St. James and its Taft facility in St. Charles Parish that are under long-term monitoring. 

Like those closed gypsum piles, the active 960-acre pile at the Uncle Sam plant is made up of an unwanted and largely unusable byproduct of the company's production of phosphoric acid. Cooling ponds that normally hold the process water, recycle it back to Mosaic's plant and keep it out of the surrounding environment have been built into the gypsum pile, like the slipping lake.

The emergency reservoir was once one of those cooling ponds but more recently has been used for rainfall runoff. In that role, the reservoir normally empties untreated runoff into the Mississippi River, but Schweiss and state regulators said the outlet for the reservoir will remain shut while it has the acidic process water inside it.

"No process water will be discharged," said Greg Langley, spokesman for the state Department of Environmental Quality. 

Once the emergency settles down, the water will be pumped back into other ponds that normally handle process water, Schweiss said.

The reservoir also lacks the heavy plastic liner that has been installed in Mosaic's new ponds under the requirements of a 2015 consent decree that settled long-standing violations over the company's handling of process water at its facilities in Louisiana and Florida. As part of the agreement, Mosaic agreed to a $2 billion settlement. 

Instead, the reservoir has a clay liner that DEQ and company officials said would prevent process water from seeping into the groundwater below. Schweiss said monitoring wells have shown the clay liner's previous ability to contain the acidic water, while DEQ officials said that, even if there were seepage, the area doesn't have potable aquifers underneath it. 

In any case, the EPA consent decree allows Mosaic to use the reservoir for just this kind of emergency, Schweiss and Langley added.

Langley noted that the whole emergency effort is about managing the water at Mosaic.

"We're feeling our way as we go and, you know, we're trying to figure out the best way to handle this, to get the weight off that slope, to stop the movement of the slope and to remove the emergency condition," he said. 

Follow David J. Mitchell on Twitter, @NewsieDave.