Attendees

The Corps reviewed aquatic disposal options that have been investigated for the Marina del Rey project.

Capping

Capping is used to sequester the contaminated dredged material, and can be level bottom capping (constructed mound) or contained aquatic disposal (pit, diked confinement). The Corps looked at three potential disposal locations within Santa Monica Bay where sand mining has occurred, but all three environments are too energetic for use. Within San Pedro Bay, the two useable sites are the North Energy Island Borrow Pit, which a capacity of @ 6 million cubic yards, and construction of a diked confinement site along the breakwater, whose capacity would be limited by the need to avoid being a navigation hazard for vessels. It would be desirable to aim for a 20-year lifespan for an aquatic disposal site.

The Waterways Experimental Station (Mississippi) is looking at the proposed pilot project for disposal of material in a portion of the North Energy Island Borrow Pit. The results of their modeling studies should be available soon. In addition to the criteria for construction of the cap layer, we would need a long-term monitoring and management plan, including contingency plans for dealing with potential problems.

Another disposal option that has not received much investigation would be the excavation of a new pit specifically for use as a regional disposal site. It also might be possible to create a disposal island above or near the surface of the water.

Assignment: COE will identify additional studies needed and estimate dollar amounts for different monitoring approaches used in the past. Due date: September 30th.