REPORT OF INVESTIGATIONS No. 40


 SAND-AND-GRAVEL AQUIFER
 The sand-and-gravel aquifer is composed of sand but has numerous
lenses and layers of clay and gravel. In the northeast corner of Santa
Rosa County, the aquifer extends from the first saturated beds (near
land surface) to a depth of about 350 feet. In the center of the area,
however, it extends to a depth of about 1,000 feet. This aquifer lies at
the surface throughout Escambia and Santa Rosa counties.
 The shallow saturated permeable beds in the sand-and-gravel aquifer
contain ground water under nonartesian conditions, and the deep perme-
able beds contain ground water under artesian pressure. The artesian
water is confined by lenses of clay and sandy clay. Most of the water in
the sand-and-gravel aquifer is under artesian pressure.
 The gradient of the water table in the shallow beds of the sand-and-
gravel aquifer generally indicates movement of ground water toward
the nearby streams. The seepage of this ground water supplies more than
half of the entire flow of the smaller streams in Escambia and Santa Rosa
counties. The water table is the highest under the broad, relatively level
lands that are at a higher elevation than surrounding lands. Examples of
places where the water table is high include the lands between Jay and
Milton, the lands between Pensacola and Cantonment, and the land
east of Milton.
 The artesian pressure head of water in the lower permeable beds of
 the sand-and-gravel aquifer does not conform to the topography of the
 land as much as the water table. The artesian pressure head of water
 from the lower beds indicates a general movement of water to the south.
 The head of water in the northern part of both counties is usually more
 than 100 feet above sea level and at some places is more than 150 feet
 above sea level. In the central part of the counties, the artesian pressure
 head is about 30 to 80 feet above sea level except near the larger rivers.
 Upward leakage of ground water probably occurs which lowers the
 pressure head of the ground water. The artesian pressure head of water
 under the lands adjacent to the bays is usually less than 20 feet above
 sea level and often less than 10 feet above sea level.

 FLORIDAN AQUIFER
 In Escambia and Santa Rosa counties, the Floridan aquifer is com-
 posed of two sections of limestone separated by a thick clay bed. In the
 northeast corner of Santa Rosa County, the upper surface of the Floridan
 aquifer is only about 350 feet below the land surface; whereas in the
 southwest corner of Escambia County the upper surface is more than