Florida Geological Survey


for the chloride plot is 0-92. The TDS value is 0.54. but jumps to 0.74 when the obvious outlying values are removed. For the TKN regression. values from February 1987 to Aprij 1988 were used, to determine the significance of the increase in concentration. The R-squaied value for that period is 0.71- These high R-squared values tend to support Ihe interpretation that possibly fractures and the general discontinuous nature of the confining interval have allowed injected iluids to migrate vertically through the confining layer.

 South Beaches

 The South Beaches injection well has a total depth of 2.916 feet BLS in the Oldsrrar Formation. There are two separate monitor wells at the sile. The upper Floridan aquifer system well monitors the zone from 300 to 350 test BLS in the Ocala Limestone, and the lower Floridan aquifer system well monitors from 1,550 to 1,700 feet BLS in the Avon Park Formation (Appendix A2). The confining zone. as defined by Dames and Moore (1985), extends from 1,665 to 2,081 feet BLS in the Avon Park and Oldsmar Formations. The injection zone extends from 2r081 to total depth, but the interval with the most fractures and cavities is from 2,081 to 2,760 feet BLS (Dames and Moore, 1985).

 The lower monitor zone, in the lower Avon Park Formation, has interbedded dolostone. mudslone, and wackestone, with porosilies ranging from 10 percent to 15 percent, moder. ate to good induration, and apparently low per. meability.

 The confining zone, in the lower Avon Park and upper Oldsmar, has interbedded mudstone, wackestone, packstone, and dolostone layers. Porosities range from five percent in a lew interbedded cherty layers, to 20 percent in the wackestones and packstones. Both induration and permeability have wide ranges, from low to high in altemating layers. Sickensides related to


fracturing ancVor laulting were observed in cores within and above the confining zone.

 The background water-quality report (Dames and Moore, 1985) on the lower monitor zone shows that before injection the average TDS value was 23,975 mg/L, and the average chloride value was 14.410 mg/IL. In this area TDS values exceed 10.000 mg/L at approximalely 1,250 leet BLS. No TKN measurements were taken, but nitrogen, measured as nitrate, was
0.03 mg/L.

 Dramatic changes in these values have been observed since injection began in May 1987, TDS tell from over 21,000 mg/L to less than 10,000 mg/1 (Figure 40). Chloride values lelL irom over 16.000 mg/L to less than 5,000 mgfL, starting in July 1987 (Figure 41). These changes are attributed to injection waters rising through the confining units. Values of TKN show a pattern similar lo that of ihe Merritt Island well lower momLior zone- There was a rise from approximately 0.5 mg/L to a peak at about 3.0 mg/L, arid then a decline (Figure 42). This is again attributed to the increasing efficiency of (he treatment plant at the South Beaches site. It is not known why the values increased rapidly in mid-1991. No trends were observed in the upper monitor zoneRegression results show an R-squared value of 0,78 tor the observed chloride trend, with the value increasing to 0.87 when outliers are removed from the calculations. The R-squared value lor the TDS plot is 0.9, Regression of TKN values was done for the period from July 1987 to March 1988, to determine if the increasing concentration trend was significant, The Asquared value for that period is 0,88, These values lend to support the conclusion that the Iractures, cavilies, and the discontinuous nature ol the confining zone have allowed migration of injected fluids into the monitor zone.