Y. Hashimoto Chief, Environmental Protection Agency, Marine Protection Section. Roughly 400 million cubic yards of sediment will be dredged from San Francisco Bay waterways over the next 50 years. The dredged material must be disposed of in a manner that is environmentally safe and acceptable to a wide variety of competing interests. Three ocean sites considered for disposal of dredged material lie on the Farallon slope, a part of the seafloor west of San Francisco. Some Answers Preliminary mapping shows that the three sites are characterized by areas of slow accumulation and erosion of sediment.
Sediment consists largely of silts and clays, with rock cropping out in places.
Analyses indicate that sediment is stable under normal conditions and marginally stable when subjected to extreme earthquakes. Our results can serve as a baseline for subsequent studies to monitor the fate of the dredged sediment and its effect on the natural environment. The acoustic data allowed us to map the geology and shape of the seafloor and to identify areas of sediment accumulation and erosion over the entire region. Analysis of sediment samples yielded information about the character of the sediment and its stability. This information combined with underwater photographs verified our interpretations of the acoustic data.