New Wales Water Loss Incident
In 2016, a sinkhole formed beneath a cell of the active phosphogypsum stack at Mosaic’s New Wales facility. Understandably, that incident caused significant community concern. Mosaic subsequently committed to heightened transparency for notable events having the potential to affect the community and that commitment remains today.
Interest in the Water Loss Incident has resurfaced during the permitting process to extend the New Wales gypstack south in a new area to accommodate continued phosphate production at the facility. Specifics on the permit and extension are available here.
Below is an overview of the event, along with highlights of changes implemented and the ongoing monitoring and maintenance we conduct on the gypstack system at New Wales.
In August 2016, monitoring showed a decline in process water stored atop the west cell of the New Wales south gypstack. After validating that information, the decline was reported to the Florida Department of Environmental Protection (FDEP) and U.S. Environmental Protection Agency (EPA), as well as Polk County. The water loss resulted from a sinkhole that formed beneath the gypstacks, which damaged the stack’s base liner.
In response, Mosaic transferred water from the affected area to other storage areas and began operating or upgraded the recovery well system to recover the process water for management. Mosaic offered free, third-party testing of neighbor drinking water wells upon request and provided bottled water until results were confirmed. We provided daily updates on those results and the incident on our website.
Extensive monitoring confirmed the effectiveness of the recovery effort; there were no offsite impacts from the incident. In October 2016, we signed a consent order with the Florida Department of Environmental Protection (FDEP) relating to repairing the sink hole.
Using LiDAR (Light Detection and Ranging) technology and other assessment tools, the sinkhole was evaluated, and a remedial plan was developed, which called for stabilizing and then filling the sinkhole with grout, essentially sealing the cavity. Instrumentation like piezometers, helped measure water levels and directed the grouting work. By May 2018, the repairs were substantially completed recognizing that maintenance of those repairs likely would be required in the future.
Over time, any gypstack will experience some settling and consolidation, which will require periodic maintenance. As this occurs at New Wales, the Mosaic team, paired with third-party experts, continue to monitor the gypstack, groundwater and the repaired area, and submit updates to the FDEP and Polk County.
Some examples of such maintenance include:
- Regrading stack features, including the crown on top of the former sinkhole;
- Replacing and upgrading instrumentation, including geophones, piezometers and collapse monitors; and
- Recovery well pump replacements and repairs.
Since 2016, Mosaic made significant additional investments in our gypstack management and monitoring at New Wales, including adding a network of state-of-the-art geophones installed around the perimeter of the stack, which monitor micro-seismic energy that can alert us to potential changes under a gypstack.
Pictured: Geophones being installed at the New Wales gypstack
The multi-faceted monitoring systems we have in, below and around the gypstack are working as intended. They provide real-time information to guide our efforts. We evaluate this data against modelling baselines to identify potential issues.
For example, we recently observed slight increases in water quality data at the recovery well, prompting us to evaluate the cause of the increased sodium and sulfate constituents. As part of that evaluation, we are conducting more frequent monitoring and enhanced geotechnical and geophysical studies. While those efforts continue, we may supplement the grout already in place with some additional binder.
It is common for remediated areas to require additional maintenance. In 1994, Mosaic legacy company, IMC-Agrico repaired an erosion sinkhole using a similar grout plug method. In 2015, grout reinforcement was added as part of its long-term management.
The additional testing confirms that there continues to be no offsite impacts to groundwater and the monitoring systems we have in place to alert us to any changes in the stack, are doing what they should.
More South Stack Activities
Phase III New Wales Gypstack Extension Preparation
Today, there is an enhanced presence at the New Wales gypstack as pre-activities get underway in preparation for the proposed extension area. Once the permit is approved, we will ready the Phase III extension area by fortifying the foundation using drilling rigs to grout the area.
Moving forward, we will provide updates on our website to describe our ongoing stack maintenance and extension activities to give our stakeholders a better understanding of the nature of our care efforts and due diligence— demonstrating that the promise we made five years ago to act responsibly remains.