The P-16 Permit

P-16 is a pond at the Mountain Pass Mine that has been constructed for tailings impoundment. "Tailings" is a mining term used to refer to the crushed and ground ore that is left over after the valuable rare earth constituents have been removed. The production and disposal of tailings is subject to a permitting process that is administered by the County of San Bernardino and the Lahontan Regional Water Quality Control Board (LRWQCB).

The P-16 facility commenced operations during the 1960's, and the LRWQCB permit for the facility has been amended a number of times. The most recent permit (also known as Adopted Board Order R6V-2004-0042) was issued to Molycorp in October 2004 and describes the closure process and the long-term monitoring required for this facility. The application process to obtain the permit involved the preparation and submittal of a series of reports to the LRWQCB that constituted a Report of Waste Discharge (RWD).

The P-16 permit issued by the LRWQCB contains very detailed compliance requirements. The permit includes various mitigation measures that are designed to minimize the environmental impact of the facility. Extensive monitoring programs are also described in the permit that are designed to verify the effectiveness of the closure process as well as to allow for the prompt detection of any additional environmental impacts. The permit requires comprehensive reporting on a quarterly basis to the LRWQCB. The P-16 impoundment was successfully closed during a 15 month project that lasted from January 2005 through March 2006.