The US Environmental Protection Agency ordered Molycorp Minerals, LLC, to pay a $27,300 penalty for improper management of hazardous waste at its San Bernardino County mine and mineral processing facility. The violations were discovered as part of unannounced EPA inspections in October 2012.

EPA testing at the facility determined that leaked or spilled lead-iron filter cake had impacted on-site stormwater, with the potential to contaminate soil along the edge of the holding area. A majority of the impacted stormwater was treated prior to legal disposal into on-site surface impoundments.

In addition, EPA investigators found several containers holding hazardous lead filter cake were improperly closed or labeled. Subsequent to the inspection, Molycorp discontinued the operation which generated the lead-iron filter cake.

Lead-iron filter cake is the largest hazardous waste stream generated by Molycorp. Process waste containing toxic concentrations of lead are treated and solidified utilizing a filter press. That lead filter cake is transferred and stored in hazardous waste containers.

Molycorp operates a rare earth lanthanide mine, mill and separation facility near Mountain Pass, Calif. It is believed to be the only rare earth mine in the United States. Production of lanthanide (rare earths) metals at Molycorp began in 1952. The facility suspended operations in 2002 and re-opened in 2012.

When alloyed with other metals, the rare-earths can provide enhanced magnetic, strength and high temperature and other properties. For example, high-strength magnets made from neodymium-iron-boron have been used in a variety of products, including electric motors and hybrid cars components.