REPORT OF INVESTIGATIONS NO. 38 31
7 x 10-3
leakage of 1.3 x 10-a gpd per ft3 by the ratio or by 5.4.
1.3 x 10-1
For example, for a coefficient of leakage of 7 x 10-3 gpd per ft3 and a pumping rate of 17.4 million gallons per month drawn from the west, east, and south lines of wells, the increase in chlorides would be computed to be: 350 x 5.4 or about 1,800 ppm.
A question of interest is at what rate could the well field be pumped without causing any salt-water leakage from the waterway. This rate can be estimated easily if it is remembered that the drawdown is proportional to the rate of pumping. If equal amounts of water were taken from each of the pumps in the west, east, and south lines of wells, such as was assumed in computing the drawdowns shown in figure 9, the well field could be pumped at the rate of about 6 million gallons per month without causing any salt-water leakage. If equal amounts of water are drawn from each of the pumps on the east and south lines of wells, as was assumed in computing the drawdowns shown in figure 10, the well field could be pumped at the rate of about 7 million gallons of water per month without any salt-water leakage.
Although these estimates of the rate of salt-water leakage are the best that can be made with the available data, the estimates are intended to be used only as a guide or in indication of the effect that constructing the intracoastal waterway along route C-1 would have on the Venice well field. The results are conditional and should be treated as such.
The estimates do not include any increase in chlorides that might be caused by: (1) The downward leakage of water from Hatchett Creek. (The drawdowns shown in figures 9 and 10 are great enough to cause water in Hatchett Creek, which at times has a high chloride content, to leak downward); (2) pumping from private wells; or (3) any disturbance of or cutting into the upper confining beds.
SUMMARY
1. Ground water at the Venice well field occurs in a water-table aquifer and at least three artesian aquifers: the first artesian aquifer, the second artesian aquifer, and the Floridan aquifer. The water-table aquifer extends from the surface of the ground to about 30 feet below the surface. The first artesian aquifer lies from about 50 to 65 feet below the surface, and the second artesian aquifer lies from about 80 to 130 feet below the surface. The top of the Floridan aquifer is about 280 feet below the surface.