REPORT OF INVESTIGATIONS NO. 75


Where   0     =     porosity

          3   =     compressibility of water (2.23 x 10-8 ft2/lb at 600F)

          7   =     specific weight of water (64 lbs/ft3 for salt water)

          BE  =     Barometric efficiency (0.70) therefore

          Ss  =     0 (2.23 x 10"8) (64) . ft2 . lb
                       7.0 x 10-1         lb   ft3

                 =  0 (2.04 x 10-6) ft-1;


      Based on the relationships in equation 6, the hydraulic conductivity was calculated for porosities ranging from 10 to 90 percent by the following equation:

         K    =     hydraulic diffusivity x Ss,                        (10)

substituting

         K = (2.1 x 1011) (2.04 x 10-6) 0 . ft2 . 1 day ft

                 =  4.28 x 105 0   ft/day

      The results of the computations are shown in table 1. The values of K and Ss vary widely, depending upon the porosity. Generally, the connected porosity of very permeable limestone aquifers,,like the Biscayne aquifer, which is about 100 feet thick, ranges from 20 to 30 percent. The caliper-flowmeter log of the Peninsula well showed that the main water-bearing zone occurs between 2,930 and 2,945 feet. The porosity of the 15-foot zone is probably higher than that of the Biscayne aquifer.

      In the author's opinion a reasonable estimate of porosity for the 15-foot thick zone is 50 percent. The specific storage and hydraulic conductivity values corresponding to a 50 percent porosity (table 1) are 1.0 x 10-6 ft-1 and 2.1 x 1O   ft per day, respectively. If, on the other hand,- the thickness of the water-bearing zone is greater than 15 feet one would expect a lesser value for porosity.