Improving Fine Dredge Material for Use as Fill Material

This study investigates methods of improving fine dredge material for use as fill material. Dredging is common in port cities, creating the need to store or use large volume of soil. While the dredge material's coarse fraction is typically used in transportation applications, the fine dredge material has limited utility and often requires storage. Fine dredge storage in Duluth, Minnesota is limited, increasing the need for reuse. The city is targeting former industrial areas for redevelopment, generating significant requirements for fill. The authors investigated methods of improving Duluth fine dredge material, classified as SM by the unified soil classification system, through combination with several locally available, inexpensive materials, including fly ash, lime kiln dust, taconite mine tailings, and recycled tire. Fly ash and lime kiln dust were not effective in raising hydraulic conductivity to minimum requirements. Additionally, already elevated pH levels in former industrial areas led to environmental concerns with fly ash use. Combinations of approximate two thirds coarse borrow, in this case taconite mine tailings or recycled tire, and one third fine dredge material provided a method of reusing materials to create engineered fill material.