FMC manufactured elemental phosphorus from the late 1940s until December 2001. Since 2001, FMC has decommissioned and dismantled the manufacturing plant and closed waste ponds. RCRA closed Pond 16S covers an area of approximately 10.2 acres and contains approximately 140 acre feet of phosphorus containing waste from the elemental phosphorus manufacturing process.
In June 2006, visible air emissions were observed coming from the temperature monitoring ports (TMPs) at Pond 16S. Air emissions were subsequently observed by Shoshone Bannock Tribal staff in September, 2006. These were thought to be emissions of phosphorus pentoxide, from the auto-ignition of phosphine gas. FMC reported that phosphine gas had collecting in TMP well casings, where it was auto-igniting. The auto-ignition concentration of phosphine is 20,000 parts per million (ppm). The concentration of phosphine gas that is immediately dangerous to life and health is 50 ppm. On November 20 and 21 2006, the EPA On-Scene Coordinator and START contractor conducted removal site assessment activities at Pond 16S and met with the property owner to discuss immediate actions to be taken to mitigate any ongoing release of phosphine gas.
November 20 and 21, 2006: EPA OSC Weigel and 4 START contractor personnel on site. Conducted air monitoring around Pond 16S with Area RAE. Monitored for HCN, PH3, H2S, CO, O2, LEL, and Volatile Organic Compounds (VOCs). START also collected air samples to be submitted for
laboratory analysis. START collected air samples at four downwind locations
and one air sample at a background location over a four-hour time period. START also collected air samples from under the cap of Pond 16S at Temperature Monitoring Point (TMP) #1. START collected two air samples (one for HCN analysis and one for H2S analysis) over a one-hour time period, one air sample (for PH3 analysis) over a 30-second time period, and one air sample (for H2S analysis) over a six-minute time period. The EPA OSC and a START engineer also conducting an inspection of the current gas extraction and treatment system and FMC and their contractor personnel. This information was used to provide technical comments on engineering controls currently being used to extract and treat the gas and ensure that pond gasses are not released to the environment. Technical comments and OSC direction included measures to seal TMP well heads that FMC was in the process of implementing.
December 20, 2006: OSC Andy Smith and 3 START contractor personnel returned to the site to collect additional air samples necessary to augment and confirm earlier results. A total of nine air samples were collected from previous and new locations
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