THE GROUND WATER FLOW SYSTEM IN THE 

 VICINITY OF MARCO ISLAND, FLORIDA 



Vincent P. Amy 



Geraghty & Miller, Inc. 

 West Palm Beach, Florida 



INTRODUCTION 



The Deltona Corporation's 

 planned development of a coastal 

 area near Marco Island includes the 

 creation of a series of intercon- 

 nected lakes ranging in depth from a 

 few feet to as much as thirty feet. 

 Construction of these lakes will 

 penetrate the water table aquifer in 

 an area that is a mix of coastal wet- 

 lands and uplands. Because the lakes 

 are to be created as part of a com- 

 munity development, one of the fact- 

 ors to be considered is the impact 

 on water quality. 



The previous section of this re- 

 port revealed that both fresh and 

 hypersaline water existed in Lake 

 Marco Shores. Because of the ge- 

 ometry of the lake and the density 

 difference between the two fluids, 

 no mixing has occurred; a distinct 

 boundary exists between the two. 

 Hypersaline ground water also was 

 found in shallow wells drilled in 

 the vicinity of the lake. Much has 

 been written regarding the effect of 

 runoff on the quality of lake water; 

 little has been written on the in- 

 fluence of ground water quality and 

 the contribution of the ground water 

 flow system. Accordingly, this study 

 was conducted by Geraghty and Miller 

 to investigate the influence of 

 ground water on the proposed lake 

 system. The principal goals were 

 to estimate groundwater input to the 



the property and to investigate 

 fresh-salty ground water relation- 

 ships in the vicinity of Lake Marco 

 Shores . 



METHODS 



The study was based on evalua- 

 tion of data collected from a variety 

 of sources--an existing network of 

 multi-zone monitor wells on the pro- 

 perty, new multi-zone wells, explora- 

 tory and observation wells installed 

 by the South Florida Water Management 

 District (SFWMD) , and information 

 from published reports. In addition 

 to an existing network of five multi- 

 zone monitor wells on the property, 

 multi-zone monitor wells were in- 

 stalled at five other locations on 

 the property to provide more complete 

 coverage. Two wells, 10 and 30 feet 

 deep (3.05 and 9.14 meters) were in- 

 stalled at each site. Each well was 

 sampled during drilling and geologic 

 logs were prepared. After completion 

 and development, water samples were 

 collected from each well and sent to 

 a certified laboratory where analyses 

 for selected constituents were 

 performed. The elevation of each 

 well was determined so that water 

 level measurements could be refer- 

 enced to NGVD (National Geodetic 

 Vertical Datum) and contour maps 

 and cross-sections depicting the 

 groundwater flow system could be 

 prepared . 



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