Bulletin No. 64


Haberfeld, DER, personal communication, 1991). This assumption is consistent with available TKN background values for other injection wells (see, for example, the Merritt Island background water quality section). When injection began, TKN values began to rise from around 4.0 mg/L to about 12.0 mg/L when injection stopped (Figure 45). The anomalous 34 mg/L value is probably due to sampling or analytical error. Values continued to rise for a short time after injection stopped (approximately 2 months), and then began to decline again. These patterns are best explained by rising injection waters and communication between the injection and monitor zones. One reason that the trends in the lower monitor zone are so prominent is that it is within 220 feet of the top of the injection zone.

 For the regression analyses, the chloride and TDS divided into two parts. Data collected during injection, from July 1988 to March 1989, comprise the first part, and data collected after injection stopped are in the second part. The Rsquared value for TDS values during injection is 0.69, and is 0.51 for the period after injection stopped. The values for chloride are 0.74 for both periods. These values seem slightly low because the patterns of declining and increasing concentrations are readily apparent on the graphs. This is probably due to the scatter of the data, most likely caused by fluctuating injection rates. Regression of TKN data was conducted for the time period from July 1988 to July 1989, to assess the significance of the increasing concentrations values. The R-squared value for this period is 0.93.

 The intermediate well water-quality data show trends which indicate rising injection water, though the patterns are somewhat erratic and attenuated. In particular, chloride values decreased from a high of approximately 16,000 mg/L to a low of approximately 10,000 mg/L during injection, and increased after injection stopped.


 The upper monitor well water-quality data show patterns that indicate increasing salinity. These patterns are most likely related to rising formation water, displaced upwards by injection water. TDS values increased from about 8,000 mg/L to over 17,000 mg/L and chloride concentrations increased from about 4,000 mg/L to a high of almost 14,000 mg/L just before injection stopped. Concentrations then dropped and fluctuated around 9,000 mg/L. TKN values increased from about 1 mg/L to over 12 mg/L.

 The changing ground-water chemistry observed in all three monitor zones indicates that the existence of a coherent confining zone in this area is highly questionable. Knapp (1989) concluded that there is "...inadequate information to determine if a confining sequence exists between 1,900 and 2,000 feet below land surface...," and the report confirms the freshening trends seen in the deep and intermediate monitor zones and the increasing salinity of the upper monitor zone during injection (Knapp, 1989). He also concluded, "The rate of change in the water quality indicates that there is a direct conduit from the injection zones into the monitor zones."

 Secondary Wells

 Harris Corporation

 There are two injection wells at the Harris Corp. site, one with a total depth of 2,800 feet BLS and the other completed at 2,333 feet BLS, both in the Oldsmar Formation. The confining zone, as defined by Geraghty & Miller, Inc. (1984), extends from 1,362 to 2,030 feet BLS, in the lower Avon Park and upper Oldsmar Formations. The major injection interval in both wells is from 2,030 to 2,245 feet BLS (Appendix A4). There is a dual zone monitor well at the site, with the upper zone monitoring the interval from 430 to 550 feet BLS in the lower Ocala Limestone and upper Avon Park Formation, and the lower monitor zone extending from 1,527 to 1,535 feet BLS in the lower Avon Park Formation.