170 



Hancock Foundation. The disappearance rate established 

 included the effects of eddy diffusion, although its magni- 

 tude in relation to mortality, sedimentation, and other 

 factors could not be determined. 



Eventually, an intensive experimental and theoretical 

 investigation into eddy diffusion in shallow or coastal water 

 must be undertaken, because along with currents it is a 

 physical process of the utmost importance in determining the 

 rate of dispersal of any component of sewage, and the con- 

 centration of waste material in surrounding waters. As long 

 as this is neglected, forecasts as to the behavior of sewage 

 will remain largely on an empirical basis. 



In the investigations of the University of Southern 

 California the rate of disappearance of coliforms under 

 specified conditions was determined. The next problem was 

 to establish the direction and velocity of the ocean currents, 

 for if the bacteria were carried ashore or in any direction 

 at such a rate that their numbers could not be reduced to the 

 numbers required by law, then pollution by legal definition 

 would occur. Of course, currents are important in distri- 

 buting other components of the sewage as well. During the 

 past year the circulation of Santa Monica Bay has been measured 

 by three methods; (1) current meters, (2) drogues, and (3) drift 

 cards. In addition, a radioactive tracer study was conducted 

 on May 22, 1956, from which it was hoped that additional infor- 

 mation on the trajectory of a tagged body of water could be 

 determined , 



