The observation well network was 

 completed in late February 1980 dur- 

 ing the dry season. Since then, 

 Applied Environmental Services (AES) 

 personnel have been measuring water 

 levels periodically. These measure- 

 ments have been used in preparing 

 water table contour maps. 



In addition to site-specific 

 data, similar information from areas 

 surrounding the property also has 

 been used. Data on water levels, 

 quality, and geology from a network 

 of exploratory and observation wells 

 installed by the SFWMD were used 

 to depict regional conditions. The 

 locations of all wells are given on 

 Figure 1. Information also was 

 obtained from a variety of published 

 reports dealing with the hydrogeology 

 of the general area. 



Clay and silt layers are not present. 

 The thickness of the sand ranges from 

 five to six feet north of the planned 

 development to as much as 25 feet 

 (7.62 meters) near the west end of 

 Lake Marco Shores. In general, the 

 sand is thicker along the southern 

 part of the area near the lake and 

 thinner to the north. 



The Fort Thompson-Caloosahatchee 

 Marl Formations (undifferentiated) 

 underlie the sand throughout the 

 study area. Typically, these forma- 

 tions consist of ±20 feet (6.1 

 meters) of a hard, sandy, shelly 

 limestone. Marl is present in 

 places. Near the bottom of this 

 zone, cavities are frequently en- 

 countered. Most of the observation 

 wells installed as part of the 

 Geraghty & Miller field program pene- 

 trated cavities in the upper 20 feet 

 (6.1 meters) or so of the limestone. 



RESULTS 



SUBSURFACE CONDITIONS 



The zone of interest in the 

 study area consists of the upper 30 

 to 60 feet (9.14 to 18.3 meters) of 

 sedimentary rocks formed by uncon- 

 solidated sand and limestone. A 

 typical cross-section is illustrated 

 in Figure 2. The section is drawn 

 approximately parallel with the di- 

 rection of groundwater flow. The 

 entire area is overlain by a veneer 

 of fine- to medium-grained clean, 

 quartzitic sand (Pamlico Sand) with 

 varying amounts of organic material. 

 The upper one foot or so consists of 

 silty, peaty material throughout much 

 of the area. The predominant color 

 of the shallower sand beds is tan to 

 brown, owing to the presence of and 

 staining by organic matter. 



Deeper portions of the sand 

 range in color from tan to gray. 



The Tamiami Formation underlies 

 the Fort Thompson-Caloosahatchee 

 Formations. The upper portion of the 

 Tamiami Formation consists of the 

 Ochopee Limestone member which is 

 about 130 feet (39.6 meters) thick. 

 This unit consists of abundant shell 

 fragments and cavities, particularly 

 above depths of about 80 feet (24.4 

 meters) . 



HYDROLOGIC CHARACTERISTICS 



The Pamlico Sand and the under- 

 lying limestone formations form a 

 single hydrologic unit, especially 

 in the upper 80 feet (24.4 meters) 

 or so. No clay or silt confining 

 beds are present in the Pamlico 

 Sand, and there appear to be no con- 

 fining units in the limestone. Thus, 

 the sand will transmit water to the 

 limestone and vice versa, so that 

 both the sand and limestone respond 

 hydrologically as a single unit form- 

 ing a water table aquifer in the area, 



253 



