POSSIBILITY OF SALTWATER LEAKAGE FROM
PROPOSED INTRACOASTAL WATERWAY
NEAR VENICE, FLORIDA WELL FIELD
By
William E. Clark
ABSTRACT
The proposed route C-1 of the intracoastal waterway passes a few hundred feet west of the Venice well field. One of the questions involved in constructing the waterway along this route is whether salt water will enter the well field from the waterway. In investigating the problem, the construction of the wells was determined, the geology was studied, water from wells was analyzed, and pumping tests were run.
There are three comparatively shallow aquifers at the well field: the water-table aquifer, the first artesian aquifer, and the second artesian aquifer. The water from the Venice well field is drawn from the first and second artesian aquifers. The water from the first artesian aquifer is of a better quality than the water from the second artesian aquifer. The water from the first artesian aquifer contains about 30 ppm (parts per million) of sulfate and about 50 ppm of chloride; whereas, the water from the second artesian aquifer contains more than 400 ppm sulfate and about 100 ppm chloride. The water from both aquifers is very hard. The poorer quality of water in the second artesian aquifer may be caused, in part, by the intrusion of highly mineralized water from a deeper aquifer, the Floridan aquifer.
The proposed waterway will cut into the water-table aquifer. If the well field is pumped too intensively, salt water will leak downward from the waterway into the producing aquifers. The downward leakage of the salt water, however, will be impeded by beds of relatively low permeability that lie below the waterway and above the first artesian aquifer. Estimates indicate that 6 or 7 million gallons per month may be pumped from the well field without causing salt-water leakage. Salt-water leakage may be kept within tolerable limits by reducing the pumpage from the field or by redistributing the pumping so that it is further from the waterway.
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