252 



Surface Currents 



The main focus of interest probably is in the upper 

 layer of water because it is within this layer that a large 

 part of the effluent and at least part of the sludge initially 

 will be found. They will remain there until they become so 

 diluted by settling of particulate matter and by vertical and 

 horizontal mixing that the waters are no longer recognizable 

 as containing material of sewage origin. It is also in this 

 layer that maximum current velocities generally will be found. 



During the period ot September 8, 1955 through February 

 16, 1956, the pattern of surface flow was variable, but the 

 bay appeared to be well flushed^ at least intermittently, by 

 relatively strong currents directed either to the north or to 

 the south. Of the five cruises during this interval, on only 

 one (September 29, 1955) was there a general drift to the east 

 and inshore from part of the area. On one (September 8, 1955) 

 the initial drift was to the north and outside the bay, and 

 on the other three the surface waters appeared to have been 

 removed almost completely from the bay (December 29, January 

 18, and February 16). 



Beginning on February 22, and extending through the 

 cruise of August 9=10 5, 1956, the predominant drift was toward 

 the shores of the bay, but frequently superimposed upon this 

 was a moderate southerly or northerly component. Many of these 

 later cruises, as well as the earlier one of September 29, 1955, 

 showed signs of a divergence in the current as the water 

 approached the shore. It is most clearly marked on the charts 

 showing drift card returns of September 29, Area III, and of 



