The Raven Rock Mountain Complex (RRMC), also called "Site R", is an underground hardened command and control facility operated by the US Army in Adams County, Pennsylvania. The facility is located adjacent to the state and county border with Frederick County, Maryland. The installation encompasses 640,000 square feet on 716 acres. The facility poses unique risks to fire/life safety, given the presence of confined spaces, large industrial power plants with fuel storage, high voltage electrical and communications equipment, and unventilated areas.