36 
other occasions, however, samples taken in the vicinity of the 
outfall showed initial dilutions as low as 1/33. It is probable 
that oceanographic conditions and sewage discharge rates vary 
sufficiently to produce marked fluctuations in the initial degree 
of mixing. The calculated counts followed the observed counts for 
the first two hours of the Whites Point experiment and then started 
to digress. The final difference was somewhat less than those at 
the other outfalls, amounting to only a magnitude (Fig. )). 
The three sets of data are thus qualitatively alike although 
quantitatively different. They show that the maximum effect of 
dilution on the coliform population occurs during the initial 
mixing of the effluent with sea water as it leaves the outfall, 
and any further reduction in MPN due to dilution is slow. 
Surface Distribution of Coliforms 
The surface sewage field around the Orange County outfall as 
determined by coliform detection is outlined in Figure 5. The 
picture is a composite based on zal the surface samples taken 
from the VELERO IV on the four trips to this area, plus a series 
of inshore samples collected by personnel of the County Sanitation 
District of Orange County on December 19 and 20, 1955. The shaded 
portion represents the area within which all positive samples of 
any magnitude are contained. The field drawn should not be con= 
sidered a static picture of the area of detectable sewage, but 
rather as a rough boundary beyond which coliforms should not 
usually be found. 
The same surface data, when plotted as the log of the coli- 
form count against distance from the outfall, independent of 
=~ 
