COLIFORM BACTERIA IN THE WATER 
Radioactive Tracer Study 
Description of Cruise 
On the day of the tracer experiment, unchlorinated effluent 
was discharged from the Hyperion plant for a total of eight 
hours, according to the following schedule: unchlorinated secon- 
dary, three hours; unchlorinated primary, two hours; unchlori- 
nated primary with tag, one hour; unchlorinated primary, one 
hour; unchlorinated secondary, one hour. Radioactive scandium- 
46 was fed into the primary unchlorinated effluent at the treat- 
ment plant at a constant rate for one hour starting at 0700, 
May 23, 1956. Sufficient scandium-46 was introduced to allow 
a measurement of dilution of the effluent to about one part 
in 10,000. 
Radioactivity was detected in the boil approximately one 
hour after its introduction into the outfall, and measurements 
were continued in the boil for a further hour until the radio- 
activity started to decrease. Two dye patch experiments were 
started, about one hour apart, while the radioactivity was at 
its peak. A series of patterns, spaced at appropriate intervals, 
was then traversed by the VELERO IV making radioactivity measure- 
ments while underway. These patterns served to delimit the 
extent and position of the radioactive field at various times. 
Surface samples were taken while the ship was underway at posi- 
tions where the radioactivity appeared maximum. At the end of 
each traverse pattern, the ship returned to the position of 
maximum radioactivity where measurements were taken of radio- 
