Solidification/Stabilization of Soft River Sediments Using Deep Soil Mixing

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CAIT project no.: 154 RU9178

Fiscal Year: 2004/2005

Status: Final

Rutgers-CAIT Author(s): Maria Boile, Husam Najm, Ali Maher

External Author(s): Scott Douglas



The objective of the demonstration project was to investigate the feasibility of using in-situ solidification/stabilization technology to treat highly contaminated sediments similar to those found in NY/NJ Harbor and surrounding waterbodies.

The study evaluated a technique that amends sediment, in situ, with a pozzolanic mixture, such as Portland cement. Mixing of sediments with pozzolanic materials has been used successfully throughout the NY/NJ Harbor to stabilize low-to-moderately-contaminated sediment dredged from navigation channels. Rutgers University was retained by the NJDOT to assess the utility and viability of using Cement Deep Soil Mixing technology (CDSM) for the in-situ solidification/stabilization of contaminated river sediment and to evaluate: 1) the efficacy of the technology to stabilize sediments and associated contaminants; 2) the optimum percentage of pozzolanic additive; 3) the potential for dispersion of sediments during treatment; and 4) the impact that highly organic enrichment might have on the pozzolanic treatment.

The pilot study demonstrated that significant improvement in the shear strength of the mixed sediments was measured following stabilization. Also a reduction of 40% in moisture content was measured within the solidified sediments. As a result, the treated sediments could be handled, transported and disposed of in a more environmentally sound manner. This is of great importance for toxic sediments. Turbidity was measured during the mixing operation and was found to be only within 120 feet of the mixing location.