Reconnaissance of the Water Resources in the Vicinity of Proposed Deep-Well
Injection Sites in Southeast Dade County, Florida
By J.E. Earle and F.W. Meyer
INTRODUCTION
Deep-well injection
has been selected by Dade County Water and Sewer Authority as a means of
disposing treated waste water in southeast Dade County. Preliminary plans
call for construction of a county-owned sanitary sewage treatment plant
and several 3,000 foot deep injection wells at 1,000-foot intervals on Levee
31E. As a first stage, drilling of seven wells, capable of accepting, in
the aggregate, 30 mgd (million gallons per day) of treated liquid waste,
is planned. The locations of the proposed sites (fig.1)
were selected by consultants for the authority.
A reconnaissance
was made in the vicinity of the proposed well sites to determine the chloride
content of surface and ground water because this information is needed to
formulate plans for the safe disposal of salt water during drilling and
testing of the injection wells. The reconnaissance was part of a cooperative
program with the Dade County Water and Sewer Authority to investigate the
hydrologic effects of injecting treated waste into a deep saline aquifer.
The area of investigation
is near Cutler Ridge in southeast Dade County. It occupies about 5 ½
square miles bounded on the east by S.W. 77th Avenue extended, on the west
by S.W. 97th Avenue, on the south by Coconut Palm Drive, and on the north
by Old Cutler Road (fig.1.)
The area for the investigation was selected by the Authority and their consultants.
A considerable amount
of knowledge was available at the start of the investigation, part of which
has been documented, and part in survey files, unpublished. Most of the
area underlain by the Biscayne aquifer that contains salty water at various
depths. The approximate farthest inland extent of the slat front at the
base of the aquifer under the drought condition of May 1971 is shown in
figure 1 (Hull and Wimberly, 1972)
Samples of water
were collected from 8 wells and 44 surface-water sites (fig.1)
on February 22, May 18, and August 4, 1972 for determination of chloride
content. Chloride content was used as a measure of salinity. Chloride content
in natural waters of Dade County usually ranges between 12 mg/l (milligrams
per liter) in rainfall and 19,000 mg/l in sea water. On August 3, 1972,
profiles of the specific conductance of ground water were made in four wells.
The specific conductance values were converted to chloride content based
on a relation developed between chloride content and conductance for numerous
samplings of natural waters in southeast Florida. The results of samplings
in the area are presented in Table 1. Chloride in surface-water samples
ranged from 15 to 14, 600 mg/l, and in ground-water samples from 26 to 11,500
mg/l.
(The entire report
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