124 REPORT OF INVESTIGATIONS NO. 50
Analytical results in micrograms per liter
Aluminum 13 Germanium < .29 Beryllium < .57 Iron < .29 Bismuth < .29 Manganese < 1.4
Cadmium < 1.4 Molybdenum .54 Chromium < 1.4 Nickel .63
Cobalt < 1.4 Lead < 1.4
Copper < 1.4 Titanium < .57 Gallium < 5.7 Vanadium < .29 Zinc < 5.7
These concentrations are well within the recommended limits set by the U. S. Public Health Service. The symbol < indicates that the concentrations are less than the values shown which are the lower detection limits.
The temperature of the water in the Floridan aquifer in Orange County ranges from 71 0 to 770F (See fig. 59.). In general, the temperatures of the water increase with increased depth in the aquifer. This is probably due to the natural geothermal gradient of the earth.
SALT-WATER CONTAMINATION
The only known occurrence of salt-water contamination of ground water in Orange County is in the eastern part of the county (fig. 58). The high salt content of the water in this area is probably due to incomplete flushing of sea water that entered the aquifer when the ocean last covered this part of Florida, rather than to direct encroachment from the present-day ocean. In coastal areas where fresh water and sea water are in hydrostatic balance with each other, the Ghyben-Herzberg ratio can be used to calculate the approximate depth at which sea water will be found. The Ghyben-Herzberg ratio is based on the relative weight of fresh water and sea water (1:1.025) and indicates that 41 feet of fresh water are required to balance 40 feet of sea water. This means that for every foot of fresh water head above msl, there should be at least 40 feet of fresh water below msl. Applying this ratio in the Cocoa well field area in eastern Orange County (fig. 5) where the average piezometric head is about 40 feet above msl (fig. 47), there should be fresh water in the aquifer to a depth of at least 1,600 feet below msl; yet a pilot well drilled in the area