FLORIDA GEOLOGICAL SURVEY


gravel aquifer. During periods of low flow and high tides, salt water
extends up the river past the plant. At these times, heavy pumping can
cause salt water to enter the aquifer. This happened in Chemstrand well
035-714-4 where the chloride rose to 1,100 ppm before they abandoned
the well. Due to the loss of this well, pumping was decreased in several
other wells to prevent a recurrence of salt-water encroachment. The water
from the other wells, even though low in mineral content, is predominant
in sodium and chloride ions. In central Escambia County the water from
St. Regis Paper Company wells is low in mineral content and has no
predominant chemical constituent.
 Water from the sand-and-gravel aquifer in central Santa Rosa County
has a low mineral content and shows no predominant ions. This section
appears to be the major recharge area for the county. This is indicated
by both the low mineral content of the water and the favorable topo-
graphy.
 The water in the northwestern section of Santa Rosa County is mainly
of the carbonate type. The limestone of the Floridan aquifer is closest
to the surface in this area. The water in the 445-foot well (051-652-1)
at the Florida State Forest Nursery near Munson shows the effect of
solution of the fossil shells in the lower part of the sand-and-gravel
aquifer. The water had a total hardness of 116 ppm. This type water, al-
though considered moderately hard and undesirable for some domestic
and industrial use, is excellent for agriculture.
 A flowing 535-foot well (058-715-1) at Century is high in carbonate.
This is probably due to contact with a limestone bed just above the
aquifer. The constituents in water from this well are carbonate (89
ppm), sodium (62 ppm), and silica (12 ppm). The water contained
practically no calcium, magnesium, or chloride. The presence of sodium
bicarbonate is probably an example of natural softening. The water dis-
solves the calcium carbonate from the limestone; then by ionic ex-
change the calcium is replaced by sodium from clay lenses, which are
numerous in the sand-and-gravel aquifer. The pH of this water is 8.4. An
earlier analysis of a 305-foot well (058-715-2) in this area shows a water
of a similar type.
 In the area just west of and parallel to the Escambia River, from
 McDavid to Molino, the sand-and-gravel aquifer is apparently divided
 into two or more separate aquifers. Wells in the upper aquifer are non-
 artesian and range in depth from about 30 feet in the north to 80 feet
 in the south. The lower aquifer produces flowing wells which range in
 depth from 125 feet in the north to 282 feet in the south. These flowing
 wells result from the pressure of water confined beneath a continuous