Comments and Lessons Learned: Advances in dredging technology highlighted ability to dredge sediment accurately. Importance and difficulty of characterizing contaminant sediment deposits accurately.3 Importance of backfilling. Difficulty of accessing data (see Chapter 4). Lack of planned post-dredging monitoring. Less stringent cleanup level (PAHs at 1,300 ppm).


Site: Lavaca Bay, TX

Stated Remedial Action Objectives (Related to Sediment Removal): Not a CERCLA remedy. Goals of this treatability study were as follows (Alcoa 2000): develop information to support the technical and economic evaluation of potential remedial actions; evaluate the effectiveness of dredging equipment on removal of mercury impacted sediment in the study area; evaluate potential impacts of dredging on mercury mobilization and residual sediment concentrations; and, understand the impact that dredging mercury contaminated sediment may have on mercury levels in Bay biota.

Stated Cleanup Levels: None given.

Comments: Pilot study.

Dates of Remediation: 1998.

Were Cleanup Levels Achieved? Not applicable—no cleanup levels indicated.

Were Remedial Action Objectives Achieved? Pilot-study goals apparently achieved; not expected to achieve long-term risk reduction.

Comments and Lessons Learned: (1) No significant change in average surficial sediment contaminant concentrations after dredging. (2) Advantages of pilot study for describing results of large-scale dredging at this site. (3) Evaluation of residuals after each dredging pass provided useful information on generation and concentrations.


Site: Black River, OH

Stated Remedial Action Objectives (Related to Sediment Removal): Not a CERCLA remedy. The goal of the sediment remediation project was to remove PAH-contaminated sediment to eliminate liver tumors in resident brown bullhead populations (Zarull et al. 1999).

2

Fish sampling was conducted in 1996 and 1997 and resulted in lifting of fish-consumption advisory in 1998 (CH2M Hill 2001), but there is no indication that shellfish sampling has been conducted.

3

“Detailed design investigations during the summer and fall of 1988 [post-ROD, pre-dredging] showed the volume of contaminated sediments to be approximately 150,000 cy, an increase of three times that estimated in the ROD. This dramatic volume increase resulted in a cost estimate for the selected remedy rising from approximately $55 million to about $150 million” (EPA 1990b).



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