20 
The comparable data for the vicinity of the Orange County outfall 
are also plotted on Figure 6 for purposes of conparisieay the 
average disappearance rate for this area being 90% in 13 hours. 
In an effort to determine whether or not the dye patch 
experiments gave data that were representative of the entire 
effluent field, experiments were run at Whites Point and at 
Hyperion (during discharge of secondary treatment effluent) 
in which a large number of samples were collected over a closely 
Spaced grid (1,000 feet on a side) located within the sewage 
field. The results of these experiments were discussed in the 
May 1 report. The same type of experiment was done on three 
Separate occasions during the discharge of primary effluent from 
the Hyperion outfall. Two grids of 25 samples each, spaced 
approximately 4 hours travel of the field apart, were run on 
each trip. 
The individual counts in the grids showed the same type of 
distribution as was shown for the two previous Hyperion grids 
(May 1 report), with most of the values for any grid clustered 
around the geometric mean. The geometric mean of the MPN's of 
the individual grids are plotted on Figure 6. It can be seen 
that, with one exception which was low, the means fall remarkably 
close to the curve representing the average disappearance rate 
determined from the dye patch experiments. These data are further 
confirmation that the dye patch technique gives a representative 
picture of the behavior of the effluent field. 
The question as to whether the fluorescein used in the dye 
patch experiments exerts a toxic effect on the coliforms present 
waS previously considered. Experiments were reported (May 1 
