UNCONFINED GROUND WATER IN THE MIAMI AREA
The Ground-water Reservoir.--Very large aggregate supplies of potable ground water exist in the highly permeable aquifer (Tamiami formation, chiefly) in which the present wells are developed (see Plates 1, 2). Computations based on the known depth (top to bottom) and length (east to west) of the aquifer with an estimated 18% specific yield indicate over 15 million gallons of ground water stored in each foot of width (north to south) of the aquifer.
The permeability coefficient is very high with an average value of about 35,000. This means that through a section of the formation a mile wide and a foot deep 35,000 gallons of water a day would pass through under a water table slope of one foot to the mile. In terms of transmissibility, this coefficient of 35,000 must be multiplied by the depth, in feet, of the saturated part of the aquifer. Most water-bearing materials in which wells are developed elsewhere have a coefficient of permeability that ranges from 10 to 5,000. The most permeable material ever investigated in the U. S. Geological Survey hydraulic laboratory had a coefficient of about 90,000. Field permeability tests show that in some places in the Miami area the rocks are about that permeable.
The aquifer in Dade County ranges from about 10 feet deep in the extreme west to almost 300 feet deep in limited areas along the Atlantic shore. In the vicinity of the Miami well field the formations are over 100 feet thick but of this only about 75 feet is highly permeable because of oolite and fine aand in the-section (see Plate 2).
The highly permeable aquifer underlies the entire eastern margin 'of the Sta~te from the Florida Keys at least as far north as Delray, and