Engineering study of tank fill options for landfill closure

To prepare single-shell tanks for closure, it will be necessary to piece some type of load- bearing fill material inside the tanks to support the domes. Provision of internal support permits the simplifying assumption that the combined weight of the dome, the existing operational soil cover, and the surface barrier will eventually transfer to and be carried by the fill. This engineering study provides descriptions and evaluations of four alternative concepts for fitting and stabilizing nominally empty SSTs with fill materials. For this study it is assumed that 99 percent (or more) of tank wastes will be retrieved before closure is undertaken. The alternatives are: Gravel: tanks would be fitted with crushed aggregate using a rotating stinger apparatus installed in the central riser; Grout: tanks would be fitted with a pumpable, ex-situ mixed grout formulation; Hybrid: tanks would be fitted first with coarse aggregate, then with grout, producing a pre-placed aggregate concrete material; or Concrete: tank. would be filled with a highly-flowable, ex-situ mixed concrete formulation