DREDGED MATERIAL DUMPED NEAR ALCATRAZ ISLAND IN SAN FRANCISCO BAY 



Historically, much of the sediment dredged from the 

 San Francisco Bay to maintain shipping channels has 

 been disposed of in the bay itself, particularly in its 

 deeper parts, such as near Alcatraz Island. These 

 computer-generated oblique images of the bay floor 

 south of Alcatraz Island show the effects of dumping 

 millions of cubic yards of dredged material between 

 1 894 and the mid-1 980"s in the area outlined by the 

 red circles. The images were created by the U.S. Geo- 

 logical Survey using historical bathymetric data and 

 recent multibeam (acoustic) mapping. (Grid squares 

 are 100 yards on a side, and submarine vertical exag- 

 geration isxIO.) 



Alcatraz Island 



1894 



1997 



Alcatraz Island 



\ 



64 Issues of Environmental Management in the Gulf of the Farallones 



