264 



depth to which a Secchi disc can be read in these waters is 

 usually less than 15 feet. With increasing distance from 

 shore the amount and size of detrital fragments in the water 

 naturally decreases. A consequent increase in transparency 

 occurs until at a distance of 10 to 12 miles from shore an 

 average transparency of 30 to 40 feet exists. 



As the sewage boil over the outlet of the Hyperion out- 

 fall is approached, a continuous decrease in transparency 

 occurs until in the boil itself, a Secchi disc can often be 

 seen no deeper than one foot. For a distance of about two 

 miles around the outfall, the transparency is normally less 

 than 10 feet. Such a condition would, of course, be relieved 

 if the outfall were removed ^ but the increase in transparency 

 would be no more than 5 feet except under the most unusual 

 conditions, due to the natural turbidity of the inshore water. 



Circulation of Santa Monica Bay 



The currents in Santa Monica Bay were measured by current 

 meters, drogues, and drift cards. Current velocities were 

 generally low. With current meterss, the maximum velocity 

 measured was 0.45 MPH, but most were less than 0.25 MPH. 



Drogues were used to measure subsurface currents at 

 depths of from 15 to 90 feet. Velocities were somewha"*" greater 

 than those observed with current meters or drift cards at 

 15 feet varying between 0.17 and 1.07 MPH. At greater depths 

 velocities were lower than near the surface; between 0.17 and 

 0.46 MPH at depths of 75 to 90 feet. There was no significant 

 difference in direction of flow between 15 feet and deeper 

 level „ 



