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J. C. Broska

Publications and source records attributed to J. C. Broska.

6 recordsLinked to original sources
USGS1999

Hydrogeology and analysis of aquifer characteristics in west-central Pinellas County, Florida

The U.S. Geological Survey, in cooperation with Pinellas County, Florida, conducted an investigation to describe the hydrogeology and analyze the aquifer characteristics in west-central Pinellas County. A production test well and four monitor wells were constructed in Pinellas County at Walsingham Park during 1996-97. Water-quality sampling, static and dynamic borehole geophysical surveys, and hydraulic tests were conducted at the wells to delineate the hydrogeology at Walsingham Park. A 9-day aquifer test was conducted to determine the hydraulic characteristics of the aquifer system and observe the changes in water quality due to pumping. A numerical model was constructed to simulate the aquifer test and calculate values for hydraulic conductivity and storage coefficient for permeable zones and confining units at Walsingham Park. Final calibrated values for hydraulic conductivity for the different permeable zones and confining units at the test site were 18 feet per day for Upper Zone A, 750 feet per day for Lower Zone A, 1 foot per day for Zone B, 1x10-4 feet per day for the intermediate confining unit, and 10 feet per day for the semiconfining unit separating Upper Zone A and Lower Zone A. Final calibrated values for storage coefficient were 3.1x10-4 for Upper Zone A, 8.6x10-5 for Lower Zone A, 2.6x10-5 for Zone B, 3.1x10-4 for the intermediate confining unit, and 4.3x10-5 for the semiconfining unit separating Upper Zone A and Lower Zone A. Estimates of transmissivity for Upper Zone A and Lower Zone A were about 2,500 and 37,500 feet squared per day, respectively.

Florida↗
USGS1996

Assessment of the hydrogeology and water quality in a near-shore well field, Sarasota, Florida

The city of Sarasota, Florida, operates a downtown well field that pumps mineralized water from ground water sources to supply a reverse osmosis plant. Because of the close proximity of the well field to Sarasota Bay and the high sulfate and chloride concentrations of ground-water supplies, a growing concern exists about the possibility of lateral movement of saltwater in a landward direction (intrusion) and vertical movement of relict sea water (upconing). In 1992, the U.S. Geological Survey began a 3-year study to evaluate the hydraulic characteristics and water quality of ground-water resources within the downtown well field and the surrounding 235-square-mile study area. Delineation of the hydrogeology of the study area was based on water- quality data, aquifer test data, and extensive borehole geophysical surveys (including gamma, caliper, temperature, electrical resistivity, and flow meter logs) from the six existing production wells and from a corehole drilled as part of the study, as well as from published and unpublished reports on file at the U.S. Geological Survey, the Southwest Florida Water Management District, and consultant's reports. Water-quality data were examined for spatial and temporal trends that might relate to the mechanism for observed water-quality changes. Water quality in the study area appears to be dependent upon several mechanisms, including upconing of higher salinity water from deeper zones within the aquifer system, interbore-hole flow between zones of varying water quality through improperly cased and corroded wells, migration of highly mineralized waters through structural deformities, and the presence of unflushed relict seawater. A numerical ground-water flow model was developed as an interpretative tool where field-derived hydrologic characteristics could be tested. The conceptual model consisted of seven layers to represent the multilayered aquifer systems underlying the study area. Particle tracking was utilized to delineate the travel path of water as it enters the model area under a set of given conditions. Within the model area, simulated flow in the intermediate aquifer system originates primarily from the northwestern boundary. Simulated flow in the Upper Floridan aquifer originates in lower model layers (deeper flow zones) and ultimately can be traced to the southeastern and northwestern boundaries. Volumetric budgets calculated from numerical simulation of a hypothetical well field indicate that the area of contribution to the well field changes seasonally. Although ground-water flow patterns change with wet and dry seasons, most water enters the well-field flow system through lower parts of the Upper Floridan aquifer from a southeastern direction. Moreover, particle tracking indicated that ground-water flow paths with strictly lateral pathlines in model layers correspond to the intermediate aquifer system, whereas particles traced through model layers corresponding to the Upper Floridan aquifer had components of vertical and lateral flow.

Water-Resources Investigations Report↗