Bulletin No. 64


GEOLOGIC FRAMEWORK OF THE LOWER FLORIDAN AQUIFER
 SYSTEM, BREVARD COUNTY, FLORIDA

 By
 Joel G. Duncan, P.G. #396, William L. Evans III and Koren L. Taylor


 INTRODUCTION

 Brevard County is located on the Atlantic coastline of eastern, central peninsular Florida (Figure 1). White (1970) places Brevard County in the Mid-Peninsular Zone which is "characterized by discontinuous highlands in the form of sub-parallel ridges separated by broad valleys." According to White (1970), the geomorphology of Brevard County consists of, on the east, the Atlantic Coastal Ridge and on the west, the Eastern Valley (Figure 2). Ten Mile Ridge is a discontinuous ridge trending northwest-southeast through the southeastern portion of the county (White, 1970).

 Coastal communities in Brevard County, like many others in Florida, have experienced a substantial population increase over the past several decades. Rapid growth and development accompanying the population influx resulted in increased demands on the environment. A common problem has been the disposal of liquid waste products, principally treated municipal sewage and in some cases, industrial waste byproducts. A favored solution utilizes injectiondisposal wells whereby liquid waste is pumped underground into highly permeable rocks of the lower Floridan aquifer system. In Brevard County, ground water within the lower Floridan is highly mineralized and unsuitable as a potable water source. Thus, disposal of injected waste water in this portion of the aquifer system was not considered a problem. Ideally, upward migration of liquid waste into potable portions of the aquifer system is prevented by a confining sequence of impermeable strata overlying the injection zone.

 Monitor well data from several injection sites in Brevard County suggest that the presence


and/or lateral continuity of suitable confining rock above the lower Floridan injection zone is questionable. These data indicate that a better understanding of the lower Floridan aquifer system is necessary in formulating protective criteria for future injection projects. The purpose of this study is to detail the geologic framework of the lower Floridan aquifer system in Brevard County. This will contribute to a better understanding of the local aquifer hydrogeology and thus support future injection well practices that maximize resource protection.
 This investigation summarizes the geology, hydrogeology, and ground-water chemistry of the lower Floridan aquifer system based on data from seven injection wells in Brevard County and one in Indian River County. Data employed in the study included well cuttings, cores, injection well tests, borehole videos, geophysical logs, and monitor well water chemistry information.
 The report focuses on the following aspects of the lower Floridan aquifer system:
 1. Structural Geology
 2. Lithostratigraphy
 3. Depositional environments
 4. Dolomitization
 5. Geophysical character
 6. Hydrogeology
 7. Ground-water chemistry analysis
 The greatest concentration of injection wells occurs in the Melbourne-Palm Bay area (Figure 3). Merritt Island, approximately 25 miles north of Melbourne, is the northern-most injection site of the study. The Hercules injection site, in Indian River County, is the southern-most injection well included in the study and was chosen as a control well outside the primary study area for comparison purposes.