Technical Integrity / Collaboration / Exceptional Results

Sediment Cap Stability Analysis

Integral staff conducted an analysis of sediment stability in the vicinity of the Washington Navy Yard (WNY) on the Anacostia River to provide a better understanding of the integrity of capping material and transport of contaminants of potential concern at the site. Previous studies provided a rationale for the field study design, specifically the selection of locations for sediment erosion rate measurements via SEDflume and current measurements via acoustic Doppler current profiler deployments. These data were combined with additional modeling analysis.

The WNY, as with many sediment sites, is located in an area of relatively low hydrodynamic energy, where sediments and contaminants tend to accumulate over time. This study focused on the collection and analysis of data to assess the remedial options of capping and monitored natural recovery employed at the site. A combination of historical data, site-specific measurements, and numerical modeling techniques was used to characterize the physical stability of these options.

Using SEDflume core analysis, we determined sediment erosion rates, critical shear stresses, and bulk properties of the sediments in the vicinity of WNY. The typical currents near the remediation areas were also determined to quantify the dominant conditions at the site governing sediment transport. Using typical and extreme hydrodynamic conditions in the WNY region, a numerical analysis of sediment transport on the native and capped material was performed. The analysis showed which caps were most successful at resisting erosion relative to the native sediment. The analysis provides a basis for the selection of appropriate capping material to ensure sediment stability.

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