Hydrologic conditions in the Nassau River basin, northeastern Florida, 1982-89
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Water-Resources Investigations Report↗
Geology topics
P. S. Hampson
Publications and source records attributed to P. S. Hampson.
Measurement of reaeration coefficients for selected Florida streams
A total of 29 separate reaeration coefficient determinations were performed on 27 subreaches of 12 selected Florida streams between October 1981 and May 1985. Measurements performed prior to June 1984 were made using the peak and area methods with ethylene and propane as the tracer gases. Later measurements utilized the steady-state method with propane as the only tracer gas. The reaeration coefficients ranged from 1.07 to 45.9 days with a mean estimated probable error of +/16.7%. Ten predictive equations (compiled from the literature) were also evaluated using the measured coefficients. The most representative equation was one of the energy dissipation type with a standard error of 60.3%. Seven of the 10 predictive additional equations were modified using the measured coefficients and nonlinear regression techniques. The most accurate of the developed equations was also of the energy dissipation form and had a standard error of 54.9%. For 5 of the 13 subreaches in which both ethylene and propane were used, the ethylene data resulted in substantially larger reaeration coefficient values which were rejected. In these reaches, ethylene concentrations were probably significantly affected by one or more electrophilic addition reactions known to occur in aqueous media. (Author 's abstract)
Water-Resources Investigations Report↗
Effects of hydraulic borehole mining on ground water at a test site in northeast St Johns County, Florida
An experimental mining project was conducted in northeast St. Johns County, Florida, to determine the feasibility of extracting deeply buried phosphate ore by hydraulic borehole mining techniques. The phosphate zone is between 232 and 250 feet below land surface and consists of approximately equal proportions of fine-grained phosphate, sand, and clay. Six wells were constructed at the test site to monitor effects of the mining operation on the ground-water resources of the area. One well penetrated the Floridan aquifer beneath the phosphate zone, another was completed in the phosphate zone, and the other four were finished in water-bearing zones above the phosphate zone. The mining project consisted of three separate tests in which different mining methods were used. Changes in water levels, other than in the mined zone, were detected only in the overlying monitored zone during the first two tests as a result of roof failures in cavities formed by the mining operation. Water-quality changes were observed only in the mined zone and resulted from the injection of water from the deeper Floridan aquifer as part of the mining operation. (USGS)
Water-Resources Investigations Report↗