The Mesquite Mine is located in eastern Imperial County along the southern slope of the Chocolate Mountains in southeastern California. The mine site is bounded on the north by the United States Navy Chocolate Mountains Aerial Gunnery Range and on the south and east by State Highway 78 ... The mine has been in operation since late 1985, and consists of three open pits, overburden/interburden storage areas (OISAs), seven heap leach pads and other facilities. The three mine pits are: the Big Chief, Vista and Rainbow, with mining currently occurring under existing permits. Past and present operations are described in the Mesquite Mine Consolidated Plan of Operations (POO). Current reserves will be depleted in the year 2000, but additional reserves have been identified outside the current project boundary ... The mine has proposed an amendment to the POO to allow expansion of the following existing facilities: extension of the Big Chief Pit; extension of the Rainbow Pit; construction/modification of infrastructure on public land; expansion of heap leach facilities on private land; and, expansion of OISAs ... The proposed expansions would allow the mine to continue operating through the year 2006 ... The proposed expansion is the subject of an Environmental Impact Statement (EIS) and concurrent Environmental Impact Report (EIR). The joint EIS/EIR document is being prepared in cooperation by the US Bureau of Land Management (USBLM) and Imperial County.