COMMENCEMENT BAY CASE STUDIES OF ENVIRONMENTAL DREDGING RESIDUALS

摘要

A critical issue in the initial evaluation, final design, and implementation of contaminated sediment dredging projects is assessment and management of residual contaminants that may remain after dredging is completed. Residuals can be composed of both "generated residuals" left by the dredging operation and "undisturbed residuals" remaining below the dredge prism or actual dredge cutline due to dredging inaccuracies, accuracy in defining the contaminated surface, or other factors. No removal technology can remove every particle of contaminated sediment, and field results to date suggest that post-dredging residual contamination levels often have not met desired cleanup action levels. Currently there is no commonly accepted method to predict the degree of generated residual sediment resulting from different dredges applied to different environmental settings.This paper summarizes several Commencement Bay area and national case histories that have characterized the amount of generated residuals, and discusses key design and construction considerations relevant to the assessment and management of residuals. Environmental dredging residual data are evaluated relative to operational factors and key site characteristics such as the presence of hardpan/bedrock, debris, and relatively low dry density sediment. Post-construction management strategies are also discussed.