REPORT OF INVESTIGATIONS NO. 38 17
The coefficient of leakage at well 9S is much less than the coefficient at well 31. The coefficients, however, are not comparable. The coefficient at well 9S is determined by the leakage through the confining beds above the first artesian aquifer and by leakage through the confining beds below the second artesian aquifer. The coefficient at well 31 is determined by the leakage through the confining beds just above and below the first artesian aquifer.
CHEMICAL QUALITY OF WATER
Ground water contains various substances dissolved from the air, the soil, and the material of which the aquifer is composed. The concentration of the various substances increases with, among other things, the length of time water is in contact with these materials. Water samples were collected from most of the wells in the Venice well field in July 1962. On most of the samples, alkalinity, sulfate, chlorides, hardness, pH, and specific conductance were determined (table 3).
Samples were taken from six wells that tapped only the first artesian aquifer and from four wells that tapped only the second artesian aquifer. The six samples from the first artesian aquifer had an average sulfate concentration of 29 ppm, an average chloride concentration of 49 ppm, a carbonate hardness of 307 ppm, and a noncarbonate hardness of 31 ppm. The four samples from the second artesian aquifer had an average sulfate concentration of 420 ppm, an average chloride concentration of 102 ppm, a carbonate hardness of 688 ppm, and a noncarbonate hardness of 500 ppm.
The analyses show that the water in the first and second artesian aquifers is typical of that in many limestone aquifers in Florida. The water in the Floridan aquifer at Venice is highly mineralized, rendering it undesirable for a public supply. The water in the second artesian aquifer at the Venice well field, though less mineralized than that in the Floridan aquifer, is more mineralized than that in the first artesian aquifer.
The analyses, however, probably do not show the character of the water that was originally in the first and second artesian aquifers. For example, the highest concentration of sulfate, 1,140 ppm, was in the sample taken from well 706-226-4, which taps the Floridan aquifer. The sample having the next highest concentration of sulfate, 1,060 ppm, was a composite sample taken from wells 9N and 9S that tap both the first and second artesian aquifers. The high concentration of sulfate in this sample is