Client: USACE Seattle
Location: Cascade Locks, Oregon
Scope of Work:
- Remedial investigation
Brice completed a Supplement Remedial Investigation as part of the cleanup work being conducted in accordance with CERCLA at Bradford Island. Bradford Island forms a portion of the southern end of the Bonneville Dam which is owned and operated by U.S. Army Corps of Engineers. Releases from historic dam operations have resulted in contamination in upland soils and in Columbia River sediments adjacent to the site.
Specifically, our scope of work involved conducting additional sampling in the River Operable Unit (OU) to better delineate the nature and extent of contamination and to assist in technology screening and remedial alternatives development. Brice collected 93 surface sediment samples using surface grab samplers, as well as diver‐assisted sampling methods in portions of the site with poor bedded sediment cover. We also sampled for PCBs potentially remaining in cracks and crevices in the substrate along the north shore of Bradford Island. For the diver-led sediment sampling, we used a diver mounted Ultra Short Baseline tracking system with submeter accuracy.
Brice also implemented sediment trap studies and deployed current meters to develop an understanding of sediment transport and erosional patterns to determine the viability of monitored natural recovery (MNR) as a passive technology and to support remedial design. Brice developed, constructed, deployed, and retrieved 11 sediment traps, and deployed and retrieved 8 current meters.
The project required an understanding of contaminant behavior and remediation in complex substrates and/or fractured bedrock in riverine systems. Site characteristics presented unique challenges for in-water remediation and technology development. The River OU has complex substrate and bathymetry, with fractured-bedrock substrate, boulders and cobble, and depositional areas. There are steep drop-offs and rock benches. Sediment erosional and depositional zones are not fully delineated, in part because, depending on dam operations, currents flow both downstream and upstream throughout the River OU.
