ABSTRACT
Injection wells (Class V disposal wells) are a major method for domestic
wastewater disposal in coastal environments around Florida, and particularly
the Florida keys, where there are nearly 700 in operation.
A recent report published in the June issue of Water Research by researchers
at the University of South Florida indicates that wastewater disposed by
these practices can rapidly contaminate groundwater and surface marine waters.
These investigators, led by Drs. John H. Paul and Joan B. Rose, used harmless
bacterial viruses as a tracer for the movement of wastewater from a recently
permitted class V disposal well in the Middle Keys.
This well meets current DEP requirements, which means that the well was drilled
to 90 feet and cased with PCV pipe to 60 feet. Within 8 hours of addition
of the tracer, it was detected in the groundwater, and within 36 hours it
was detected in Florida Bay.
By 53 hours, the tracer appeared in a canal on the other side of US1, on
its way to Hawk Channel and the Atlantic Ocean.
A second experiment performed last fall indicated that the tracer could move
from the waste disposal well to the same canal in less than 8 hours, if strong
North winds associated with a cold front occurred at the same time.
The meaning of these results is that wastewater from injection wells can
rapidly make its way to the subsurface. This could cause potentially serious
health problems for bathers in canals and coastal waters around the Florida
Keys.
