FLORIDA GEOLOGICAL SURVEY


 The LFA lies beneath MFCU strata and
consists of the lower part of the Avon Park
Formation, the Oldsmar Formation and the
upper part of the Cedar Keys Formation (Miller,
1997). The Cedar Keys Formation forms the
lower boundary of the LFA and generally
consists of persistently dolomitized carbonates
with widespread bedded and intergranular
gypsum and anhydrite. Except for the
northeastern part of the study area, the LFA is
commonly highly saline and not used as a
potable or an economically treatable water
source. Research on use of the LFA as a
sustainable fresh water resource for the
northeastern part of the District is underway
(Southwest Florida Water Management District,
2006a).

 The LFA is the lowermost known and well-
defined aquifer, ranging in elevation from -400
ft (-122 m) MSL in the northeastern part of the
study area to more than -2500 ft (-762.0 m)
MSL in Sarasota and Charlotte counties; LFA
thicknesses exceed 2,400 ft (731.5 m) in the
southeast part of the study area (Miller, 1986).
Per findings of the CFHUD II (Copeland et al.,
in review) the low-transmissivity strata lying at
the base of the FAS (e.g., the "sub-Floridan
confining unit" referenced in Southeastern


Geological Society, 1986) is informally referred
to as "undifferentiated aquifer systems."

 Hydraulic properties of the FAS are
summarized in Figures 33-38 for the parameters
transmissivity, storativity, leakance, Kh, and
total porosity, respectively. A large degree of
vertical anisotropy exists in the FAS (e.g., Ryder
et al., 1980; Ryder, 1982) due to variations in
grain size and diagenetic factors affecting
permeability (e.g., Budd, 2002; Budd and
Vacher, 2004). Median horizontal and vertical
hydraulic conductivity values differ by three
orders of magnitude, which is notably less than
the difference between these same parameters in
the SAS and IAS/ICU. This is due in part to a
relative lack of sampling bias in the analyzed
FAS core samples. A greater degree of
anisotropy in the SAS and IAS/ICU relative to
the FAS is another possible contributing factor.
Anomalously high transmissivity values (Figure
33) likely reflect the influence of dual-porosity
(i.e. fracture/conduit flow). It is also noteworthy
that spatial analysis of dolines (e.g., sinkholes)
in the northern and central region indicates a
statistically significant correlation between FAS
hydraulic conductivity and doline-area ratios
(Armstrong et al., 2003).


 Summary for UFA T (ft^2/day)


 A nderson-Darling Normality Test
 A-Squared 18.49
 P-Value < 0.005
 Mean 88602
 StDev 187201
 Variance 35044192303
 Skewness 4.4198
 Kurtosis 21.3092
 N 90
 M inim um 1300
 0 200000 400000 600000 800000 1000000 1200000 1st Quartile 18650
 S Median 38369
 3rd Q uartile 69789
 -- Maximum 1203210
 95% Confidence Interval for Mean
 49393 127810
 95% Confidence Intervals 95% Confidence Interval for Median
 n- I 29279 48540
 Mean- I I 95% Confidence Interval for StDev
 Median- 163279 219401
 20000 40000 60000 80000 100000 120000 140000

Figure 33. Statistical summary of UFA transmissivity data from Southwest Florida Water
Management District (2006b). Asterisks in the box plot denote statistical outliers.