The Mississippi Phosphates Corporation (MPC) Superfund Site in Pascagoula, Mississippi, is an approximately 1,500-acre former diammonium phosphate fertilizer manufacturing facility. Since 2016, KEMRON Environmental Services, Inc., and its joint venture partners have supported the U.S. Environmental Protection Agency (EPA) Region 4 with wastewater treatment, site operations, infrastructure maintenance, large-scale earthwork, waste consolidation, and closure of the East Gypsum Stack.

Water Treatment and Management: KEMRON operates and maintains the site’s industrial wastewater treatment and water management systems. This work includes treating acidic leachate and stormwater, maintaining pumps and conveyance systems, managing water levels within the containment system, and repairing dikes, levees, roads, and drainage features.

KEMRON’s primary task was to manage and treat the site’s highly acidic leachate and runoff, totaling 1.5 million gallons per day. The existing water containment system held approximately 500 million gallons of contaminated water, and rainfall added an additional 9 million gallons of wastewater per inch. KEMRON introduced an innovative in situ treatment process, using spent lime slurry to buffer low pH water. This method increased the treatment capacity from 1.5 million gallons per day (MGD) to over 4.0 MGD, improving efficiency by 20%. The process also resulted in annual cost savings of over $2.5 million due to reduced chemical usage, including lime and hydrochloric acid.

Infrastructure Improvements: Significant infrastructure improvements were essential for the site’s rehabilitation. KEMRON repaired and reinforced over five miles of levees and berms and dredged more than three miles of ditches to manage sediment accumulation, using the dredged material to strengthen the levees. Switching from diesel to electric water pumps, along with constructing new high-voltage lines, further enhanced system reliability and reduced operational costs.

Capping the East Gypsum Stack: KEMRON and its joint venture partners completed three phases of remedial construction to prepare and close the East Gypsum Stack. The work included stabilizing spent lime and gypsum, excavating and consolidating waste, grading stack slopes and benches, constructing drainage and erosion-control features, and installing structured geomembrane and engineered synthetic turf cover systems.

The third phase, valued at more than $55 million, was completed in 2026. The project included draining and dredging a pond on the north slope of the stack; stabilizing spent lime; preparing the stack subgrade; grading slopes, benches, channels, and access roads; and installing the final cover system.

Tasks performed during this Phase Include:

• Dewatered Ponds 1-5 with approximately 170 million gallon capacity.
• Excavated and consolidated 3.5 million cubic yards of spent gypsum, phosphogypsum, and other waste residuals to grade in preparation for capping.
• Installed 22,000,000 square feet over 300 acres of the engineered ClosureTurf® system—comprising a structured geomembrane, geocomposite drainage layer, and synthetic turf cover designed to eliminate infiltration and minimize long-term maintenance
• 40,000 linear feet over 7.5 miles of a triple run pipe system installed to draw leachate water from the stack. This wraps around the entire site below grade of stack reducing water volume and routing into two holding cells where leachate water can be stored, pumped, and treated.
• Integrated the cover with existing slopes, dikes, drainage systems, and water management infrastructure.
• Maintained erosion, stormwater, and water-management controls throughout construction.

In March 2026, EPA awarded KEMRON/Arrowhead Joint Venture, LLC, a $15 million contract to perform Phases 2 and 3 of the MPC remedial action.

Phase 2 includes construction of a continuous soil-cement-bentonite barrier wall to hydraulically isolate groundwater beneath Pond 6 from the East Gypsum Stack complex. The work includes a 200-linear-foot performance test section, approximately 2,520 additional linear feet of barrier wall, connection to the existing perimeter containment system, construction of a working platform and access roads, management of trench spoils, installation of piezometers, and field and laboratory quality-control testing.

Phase 3 will address four northern lime ponds through dewatering, stabilization, grading, and installation of an engineered cover system. Work includes constructing sumps and drainage trenches, stabilizing lime sludge and soft subgrade materials, improving access roads and drainage, installing a 50-mil geomembrane liner and engineered synthetic turf with sand infill, and completing anchor trenches, drainage pipes, pipe boots, riprap aprons, and site restoration.

Together, Phases 2 and 3 will improve groundwater containment, reduce infiltration and contaminated-water generation, and advance the site toward long-term closure and leachate management.