Capping widespread creosote contamination in Eagle Harbor, WA: Problems, process, and prognosis
- Environmental Protection Agency, Seattle, WA (United States)
Eagle Harbor`s marine sediments are contaminated with creosote from a former wood-treatment facility and with mercury from a former shipyard. Under the Superfund remedial investigation process, areas requiring remediation were defined based on comparison to state of Washington sediment management standards for sediment chemistry and biological effects (bioassays for oyster larvae, amphipod). From a variety of cleanup alternatives, capping was selected for a heavily contaminated subtidal area as the most cost-effective way to provide clean benthic habitat, isolate the contamination, and prevent further contaminant migration. Sandy material for the cap was dredged the Snohomish River as part of a routine federal navigation project and, over a six-month period, was placed in Eagle Harbor using two methods. Within ferry navigation lanes, a split hull barge was opened slowly while under tow. In areas with softer bottom sediments, cap material was hosed off a flat-top barge. GPS and real-time mapping of tracklines allowed for even coverage. Monitoring during and after the construction included analysis of suspended sediments (sediment traps on cap periphery), measurements of cap thickness (bathymetry, subbottom profiling, sediment vertical profile photography, settlement plates), and diver observations of nearby eelgrass beds. Final measurements show that the 21.4 hectare cap ranges from 30 to 270 cm thick, but is at least 60 cm thick in more than 60% of the area. Although PAHs were measured in the sediment traps during capping, significant levels have not been found since. Videos indicate the rapid return of epibiota, and the eelgrass surveys indicated no capping impacts on shoot density. Periodic monitoring of the cap is planned, as well as capping of remaining contaminated subtidal areas.
- OSTI ID:
- 211989
- Report Number(s):
- CONF-9511137-; ISBN 1-880611-03-1; TRN: IM9617%%305
- Resource Relation:
- Conference: 2. Society of Environmental Toxicology and Chemistry (SETAC) world conference, Vancouver (Canada), 5-9 Nov 1995; Other Information: PBD: 1995; Related Information: Is Part Of Second SETAC world congress (16. annual meeting): Abstract book. Global environmental protection: Science, politics, and common sense; PB: 378 p.
- Country of Publication:
- United States
- Language:
- English
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