The FMC site contains hazardous waste surface impoundments (called "ponds") that were capped and closed under RCRA. The ponds were used to manage wastewater containing elemental phosphorus. The plant was closed in 2001, and FMC has since dismantled and removed the manufacturing facilities.
Since 2006, phosphine gas has been detected in and around a number of the RCRA-managed ponds. In December 2006, EPA issued a CERCLA Unilateral Administrative Order requiring FMC to implement a time-critical removal action to extract and treat gas from under the Pond 16S cap that had accumulated to high concentrations. As a result, Pond 16S gas concentrations were successfully lowered and a one-year period to demonstrate that gases can be maintained at safe levels began in November, 2009.
In April 2010, FMC notified EPA that they were commencing gas extraction at Pond 15S to address high phosphine concentrations under the cap that were being released to ambient air. EPA requested additional information, and FMC provided data that showed concentrations at or exceeding 20 ppm measured in ambient air in the vicinity of Pond 15S. Also, concentrations of phosphine gas have been measured at or excess of 1 ppm in air outside of the cap at Ponds 8E and 17.
On June 14, 2010, EPA issued another CERCLA Unilateral Administrative Order to FMC, requiring FMC to address phosphine gas releases at Ponds 15S, 8E and 17. The Order also requires FMC to extract and treat phosphine gas at other RCRA ponds where EPA determines that it's necessary to protect human health and the environment. Under the Order, FMC must design and operate gas extraction and treatment systems at these ponds and conduct additional monitoring.
