Florida Geological Survey


Floridan aquifer system is located at approximately -1,000 feel NGVD in northwestern Brevard County and increases to -1,500 feet NGVD in southeastern Indian River County (Figure 22). The injection wells are not deep enough to fully penetrate the lower Floridan aquifer system. Miller's regional maps indicate that the thickness of the lower Floridan aquifer system increases in a southeast direction with estimated thicknesses in the study area ranging between 1,500 to 2,000 feet (Figure 23).

 Ground-water movement in the lower Floridan aquifer system and middre confining unit has not been adequately determined due to lack of reliable head data and to the transitory effects of ocean, Earth and atmospheric lides (Meyer. 1989). However, direction of waler movement can be inferred indirectly from temperature, chemical and isotopic data (Kohout, 1965). Kohoul (1965) proposed that ground water is moving upward from the lower Floridan aquifer system through the circuJation of cold seawater inland through the lower part of ihe Froridan aquifer system. Higher flow values result where the upper and lower Floridan aquifer systems are continuous or where zones oi secondary porosity such as fractures and dissolutional karstic features occur- Geophysical logs and borehole videos indicate that possibility for numerous Iracture zones in the lower Floridan aquifer system (Plate 3).

 The quantitative methods used to describe aquifer parameters are usually based on homogeneous, isotropic conditions in a granular medium thai assumes laminar Ilow- On a regional scale these methods may be satisfactory (Bush and Johnson, 1988): however, locally. the lower Floridan aquifer system is extremely heterogeneous, and fractured carbonates are strongly anisolropic with respect to orientation and number of fraclures (Freeze and Cherry, 1979). Turbulent flow is common in karstic environments such as the Boulder Zone (DomenJco and Schwartz. 1990). Therefore, local hydrologic analysis for transmissivity, hydraulic conduc-


tivity and confinement within a fractured medium should be viewed with skepticism.

 The carbonates ol the lower Floridan aquifer system are predominantly low-permeability. interbedded dolostones and limestones with zones of moderate to high permeability (Miller. 1986) (Plates 1, 2 and 3) (Appendix A). Hydraulic conductivity analyses by various consulting firms (Appendix A) indicate that vertical groundwaler movement in the lower Floridan aquifer system is generally low with values less than 10-4 crn/s in the vertical direction (Appendix A). Horizontal hydraulic conductivity (when analyzed) was higher with values no greater than 10-3 cmls (Appendix A). Transmissivity values for the lower Floridan aquifer system above the Boulder Zone were reported only in the Merritt Island, Port Malabar and Hercules injection wells, Transmissivity estimates were variable and ranged between 2.2 to 609 gpd/fl (Appendix Al, A6 and A8).

 Boulder Zone

 The Boulder Zone (Kohout, 1965) is a subzone of the lower Floridan aquifer system consisting of dolostones that display vertical and horizontal fractures and cavities. The Boulder Zone is a zone of high Ifarsmissivity which records a period when paleowater tables were at a level that resulted in karstilication of the upper part of the carbonate sequence (Vernon, 1970). Where the overlying dolostone is elfectively conlining. ihe Boulder Zone is used extansively lor receiving liquid wastes because of high transmissivillies (Appendix A). The Boulder Zone has no stratigraphic significance and can exist at any level or locale where paleocondilions allowed karstic processes 1o occur.

 The Boulder Zone in the study area is generally located in the Middle Eocene Oldsmar Formation al a deplh of approximately -2.,000 feet NGVD between the glauconite marker bed and the "C" market bed (Figure 24 and Plate 3). Thickness ot the Boulder Zone is locally variable