yal 
surface of the sea around this outfall is usually covered with 
large continuous patches of brown grease and stringy material. 
These patches may be several thousand feet in length and many 
hundred feet wide. Grease areas covering several hundred square 
feet have been seen as far as six miles from the outfall site. 
It appears, therefore, that each type of effluent will have 
its own settling characteristics and that this parameter will 
largely control the rate of coliform disappearance, over the 
periods of time significant in a disposal situation. Consequently, 
it is no more valid to predict what will happen in the proposed 
outfall on the basis of the Orange County effluent than it is on 
the basis of the secondary treatment effluent now being discharged 
in the bay. What is now needed is a study of what happens when 
Hyperion primary is introduced and this study should employ not 
only the methods already in use by our group and the Hyperion 
group, but should also employ radioactive tracing of the sewage 
field, if possible. 
CONCLUSIONS 
1. The greatest effect of aon on the disappearance of 
coliforms occurs during the initial mixing of the effluent with 
sea water, and subsequent effects are minor. 
2e Factors other than dilution are effective in reducing 
coliform numbers. Evidence has been obtained to show that sedi- 
mentation has a major role in this connection and may actually 
by the only other factor of significance operating over short 
time periods. 
