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• ~ • • The materials used in the construction of a slurry wall system include bentonite, slurry, and soil- bentonite backfill. The bentonite is a natural, untreated, non~hemical, powdered bentonite conforming to American Petroleum Institute Specification 13A. This is the bentonite used in oil well drilling mud. The slurry is a mixture of bentonite and clean water. The slurry is typically mixed by static or mechanical mixers and stored in a slurry pond where it is continuously remixed to insure hydration and prevent settlement and segregation. The soil-bentonite backfill consists of a mixture of soil, dry bentonite, and slurry. The soil is typically generated from the trench excavation. Supplemental fine-grained soils are sometimes added to the backfill mix. The backfill materials are mixed adjacent to the trench with a bulldozer until it achieves a consistency similar to wet concrete with a slump of four to six inches. The dozer pushes the backfill into the back end of the trench. The trench is usually covered with a compacted soil cap to protect the slurry wall and stabilize the surface. Desigp-Build Construction The design-build approach has been the favored method of contracting for slurry wall construction on several recent projects in the Front Range area. Atypical design-build contras includes: Pre{Jesign meeting to discuss options and layout features Geotechnical drilling and geologic charaserization Engineering analysis and design Development of construsion plans and specifications construsion including all of the equipment, labor, and materials necessary to construs the slurry wall Quality control testing and engineering oversight Consultation with reviewing agencies As-built drawings with a surveyed description of the final alignment Conclusions Slurry wall construction is a proven method for lining reservoirs. It is particularly well suited in converting gravel mining operations to reservoirs. In addition to forming a reservoir liner, the slurry wall can also provide the economic benefit of reduced dewatering during mining operations. Slurry wall construction contrass are frequently formatted as a design-build project. An experienced design-build team can provide an owner with a complete package from investigation to finished produs which meets or exceeds the requirements for an absolute storage right.