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Hazardous Waste Cleanup: FMC RCRA Ponds, Pocatello, Idaho

The FMC RCRA Ponds are located in southeast Idaho, approximately 3 miles northwest of Pocatello, and are situated within the Eastern Michaud Flats Superfund Site. The ponds were subject to a RCRA enforcement action that resulted in a consent decree in 1998 requiring that the ponds be capped and closed under EPA-approved RCRA closure plans. Upon completion of closure the ponds became subject to RCRA post-closure requirements.

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Site History and Cleanup Status

The former FMC Corporation Elemental Phosphorous Plant (FMC) operated a facility from the early 1940’s until December of 2001. In 1999 the US District Court of Idaho entered a Consent Decree embodying the settlement agreement between the EPA and the FMC Corporation to address hazardous waste violations under the Resource Conservation and Recovery Act (RCRA) at the FMC Corporation facility of Pocatello, Idaho.

The Consent Decree required FMC to close surface impoundments containing ignitable and reactive hazardous waste, to construct a treatment system to remove the hazardous characteristics of its waste, and to comply with specified interim requirements for handling such waste prior to treatment. In addition, the Consent Decree required the completion of Supplemental Environmental Projects offered by FMC to reduce air emissions from its operations and to conduct an environmental health assessment on the Fort Hall Reservation. FMC ceased operations in 2001 before the required treatment system for plant waste became operational. The treatment system was dismantled.

The RCRA ponds were closed in 2004 and 2005 under the RCRA Consent Decree, in accordance with EPA-approved RCRA closure plans. While most of the facility has been demolished, the eight RCRA ponds are closed RCRA regulated units with waste remaining in place, which requires ongoing monitoring under a RCRA post-closure plan. The RCRA Ponds were capped by one of two types of cover systems following the removal of water in accordance with the EPA approved closure plans, the RCRA engineered cap or the RCRA double cap, depending on the type of pond construction. The rest of the FMC facility is part of the EMF Superfund site undergoing remediation under CERCLA.

In 2006, excess phosphine gas was detected emanating from RCRA Pond 16s. The EPA CERCLA Removal Program issued a Time Critical Removal Action Unilateral Administrative Order (UAO) under CERCLA Section 106(a) which required FMC to design, construct and operate a gas extraction and treatment system for extraction and treatment of phosphine gas. Upon completion of that work and termination of the 2006 UAO, phosphine gas concentrations at hazardous levels were detected at other RCRA Ponds. A second UAO was issued in 2010. The UAO requirements include: (1) design, construct and operate a phosphine gas extraction and treatment system as necessary at the Ponds to protect human health and the environment, and (2) develop and implement a plan approved by EPA to monitor the air for releases at the RCRA Ponds and at the facility boundary. The 2010 UAO remains in effect.

Since the excess phosphine gas issues came about after the completion of the original post-closure plans, the approved post-closure plans do not provide adequate protection. While the removal actions continue to provide for protection under the 2010 UAO, EPA is reviewing and developing amendments to the existing post-closure plans to make sure that the new FMC post-closure plan contains all applicable ongoing RCRA requirements to ensure the long term protection of human health and the environment, including ongoing gas management at all of the RCRA Ponds for as long as that is needed.

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Site Description

The RCRA Ponds are named Ponds 8E, 8S, 9E, Phase IV, 15S, 16S, 17 and 18A. They range in size from 3.2 to 12.9 acres and contain from 27 to 140 acre-feet of phosphorus-bearing waste material from FMC’s former manufacturing processes and equipment. The RCRA Ponds are located in the western portion of the FMC facility in Pocatello, Idaho. These ponds are RCRA units and subject to RCRA regulation, despite being situated within the Eastern Michaud Flats Superfund Site. While the FMC RCRA Ponds have many similarities, there are also some differences in how they were constructed, operated, and closed that warrant some differences in their associated post-closure monitoring for both the traditional cap maintenance and for the monitoring requirements under development for the management of phosphine gas that is generated at varying rates at the different ponds.

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Contaminants at this Facility

Phosphine gas is the primary contaminant of concern (COC) at the FMC RCRA Ponds. Other contaminants that have been monitored for and assessed through limited investigation but were not determined to be COCs include hydrogen cyanide, hydrogen sulfide, and hydrogen fluoride.

When the waste was moved to the Ponds it was discharged as a slurry, a mixture of elemental phosphorous and water, to prevent ignition from the reaction with air. Phosphine is a product of the reaction between elemental phosphorous and water, or by the reaction of water with calcium phosphide. In a number of the closed Ponds the slurry was mixed with lime which also effects the Phosphine generation rate. When the pH of the slurry stream is lowered the waste could also generate hydrogen cyanide.

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Land Reuse Information at this Facility

There can be no reuse of the RCRA pond area because there is waste left in place in the ponds.

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Regulatory Authority

The RCRA Ponds were closed under EPA-approved RCRA closure plans in accordance with the 1998 consent decree. Since 2006, it has been necessary to extract and treat phosphine gas being generated at levels posing unacceptable risk to human health and the environment by the waste left in place in the RCRA Ponds. Currently the management of phosphine at the RCRA Ponds is governed by a 2010 CERCLA Unilateral Administrative Order for a Time Critical Removal Action (UAO) (Docket No. CERCLA 10-2010-0170). The UAO will remain in place until adequate gas management requirements are in effect under an amended RCRA post-closure plan for all remaining RCRA regulated units including the eight RCRA Ponds.


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