67 
out that the variations in sewage content of the Whites Point 
grid were very small and the variable counts cannot be ascribed 
to passing in and out of the sewage field. The same is apparently 
true in the Hyperion area. At the same time the grids were being 
run, the Hyperion personnel were measuring "viability" according 
to the described procedure. Their two hour traverse had three 
points within the area of the first grid, and their ).7 hour 
traverse had four points within the grid area. The counts for 
these seven determinations are shown in Table 9, along with other 
pertinent data. It can be seen that the variations in count can- 
not be ascribed to variations in sewage content. It also can be 
seen that traverse A and B taken by themselves indicate a marked 
reduction in count over the period involved, but that the results 
from the grid over essentially the same period do not indicate 
this decrease. If one takes the zero time count on the same day 
and the two traverse averages, a marked decrease is observed that 
approximates the results of our dye patch experiments, i.e., O hours - 
over 70,000/ml, 2.0 hours - 22,000/ml, and ).7 hours - 3,000/ml. 
Thus, data can be chosen from their runs that gives a picture almost 
identical to ours. 
The conclusion from this discussion is that both methods are 
measuring the same thing; that is, the disappearance of coliforms 
in the individual patches of the sewage field that happened to be 
sampled. Neither is presenting a picture of what happens in a 
representative sample. Either will determine what should happen 
on the average, and both should give essentially similar results 
if equal numbers of samples are examined by both methods. These 
conclusions are reinforced by the data obtained when LASD personnel 
