Pocatello-FMC Corp. has submitted a design plan to the U.S. Environmental Protection Agency for a gas emissions treatment system to eliminate phosphine and other harmful gases from its waste pond site. FMC’s elemental phosphorus plant west of Pocatello was shut down in December 2001, but residual environmental concerns remain. FMC officials said the system will effectively lower the phosphine output to below the three parts per million limit required by EPA. The company has been working on a treatment system and is using a smaller trial system for the new design. In 2006, EPA officials detected worrisome amounts of phosphine gases in air samples taken from the area through temperature-monitoring ports. It ordered FMC to install a gas treatment system on Pond 16S, the most potentially dangerous pond onsite. A pipe runs from the pond well below the ground surface to one of the temperature-monitoring ports above ground. It mixes in oxygen to dilute phosphine gases sucked up the pipe. The gas is then transferred to a filtration system that cleans the phosphine gas into harmless carbon, ready for disposal. If EPA approves the new design, 55-gallon storage drums will be replaced by a 10×10-foot storage unit. If the process is expanded to a larger storage tank, FMC will mix nitrogen instead of oxygen with the phosphine to slow chemical reactions that may cause the phosphine to rise too quickly. Jim Sieverson, remedial project manager, is the only remaining FMC employee in Idaho, where hundreds were employed at the company’s peak.
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