Impacts of the mixture rule on tank closures at Lowry Air Force Base, Colorado

Military base closures in the US will involve extensive expenditures of public funds on environmental characterization and restoration prior to transfer by deed of the surplus lands to public or private interests. Restoration and compliance issues related to base closures include the closure of underground storage tanks (USTS) in accordance with state or federal regulatory requirements. In the process of closing USTs used for storage of petroleum products or wastes at Lowry Air Force Base, Colorado, the Colorado Department of Health determined that certain USTs required closure under Resource Conservation and Recovery Act (RCRA) hazardous waste regulations, rather than under the UST closure regulations, based on the presence of nonpetroleum constituents (such as chlorinated solvents) in the tank contents at the time of closure. The purpose of this paper is to demonstrate the increased level of expenditure, the extended schedule for closure of the tanks, and the greater logistical difficulties associated with closing USTs used for storage of petroleum products or wastes that have been determined to require RCRA closure as hazardous waste tanks by regulatory authorities, and to encourage contingency planning for such unforeseen obstacles to timely base closure.