Abstract
A hydrologic study of the shallow water-bearing interval and deep water-bearing interval beneath the CSUS campus was performed to estimate hydraulic conductivity (K) in an unconfined system and transmissivity (T), hydraulic conductivity (K), and storativity (S) for a confined system and a comparison of results was used to establish best methods for analysis of these aquifer systems. Data sets collected from monitoring wells EX-1, MW-1, MW-3, MW-1A, and MW-3A were used for this study. In 1991, the CA Department of Toxic Substances Control used a mud rotary drill method to drill 6 monitoring wells and an extraction well on the CSUS campus. These wells are used for classroom demonstration and research. Boring log data was used to establish various parameters for the aquifer testing methods in this study. In 2012, CSUS Geology students, in collaboration with Professor Tim Horner, performed 4 ft and 7 ft slug tests, 3-hour and 24-hour pumping tests, and manual step drawdown tests in these wells. Data from these tests were analyzed in this study using various methods that included Hvorslev slug-tests, Bouwer and Rice slug-tests, slug-tests in high K (under-damped) systems, Theis type curve method, Walton graphical solution, Hantush inflection-point, Cooper-Jacob time drawdown, Jacob distance drawdown, well efficiency, and step-tests. The Hvorslev and Bouwer & Rice solutions gave a range of 45 ft/day to 85 ft/day for the hydraulic conductivity of the shallow water-bearing interval. In the deep water-bearing interval, K values were estimated to be within a range of 120 ft/day to 160 ft/day, T values within a range of 3,000 ft2/day to 3,500 ft2/day, and S values within 0.0001 to 0.0004. Both the well efficiency tests and the step test performed indicated that the well EX-1 was functioning efficiently at 88% and the well was not overstressed at the pumping rate of 150 gpm. In analyzing the results of this study, it was concluded that the Hvorslev and Bouwer & Rice methods resulted in valid K value estimates for the shallow, unconfined aquifer, and the Theis type curve, along with the Jacob distance-drawdown method gave reliable T, K, and S estimates for the deep, confined aquifer in the CSUS aquifer system.