No abstract

A tracer test was used to evaluate whether cross contamination exists along a monitoring well completed through a shallow ground water system in fractured clay and screened in a sand and gravel aquifer. The fractured clay is separated from the sand and gravel deposit by a layer of highly plastic unfractured clay. A natural vertical downward hydraulic gradient of approximately 0.5 exists between the shallow system and the sand and gravel aquifer. Ground water contamination was detected in an adjacent monitoring well screened in the fractured clay and in the monitoring well screened in the sand and gravel deposit. No ground water contamination was apparent in an intermediate well screened in the unfractured clay layer. A tracer of sodium bromide was injected into a shallow boring near the monitoring wells. The tracer was detected in the monitoring well in the sand and gravel aquifer after three to seven days. The bromide concentration continued to increase in this well with time while the concentration in the shallow boring declined. This trend of tracer concentration indicates the tracer has in fact migrated downward and possibly traveled along the well column.

SUMMARYA finite element model is developed to simulate the behaviour of an aquifer used as storage space for a compressed air energy storage (CAES) system. The governing equations describing a two-phase flow of air and water are coupled non-linear partial differential equations and are solved by the Galerkin approach. The resulting computer model is applied to a gas percolation problem. Upon verification of the numerical results, the model is employed to simulate the air-water displacement in a storage reservoir during daily air cycling. The corresponding saturation variations and the effects of reservoir permeability on the system are presented. The results obtained are essential in establishing storage design and stability criteria for long-term operation of compressed air energy storage systems.

Ground water in a shallow glacial till aquifer and a deeper weathered shale aquifer at a site near Rock Creek, Ohio has been contaminated with trichloroethylene (TCE). Evaluation of remedial alternatives indicated that a system of subsurface drains would be most effective for decontaminating the shallow ground water. The performance of the proposed subsurface drainage system for the shallow aquifer was simulated using finite‐element flow and transport models. Model results indicate that the drains should reduce TCE concentration in the shallow aquifer to about 8 ppb in approximately 24 years. A single extraction well was the selected alternative to remediate trichloroethylene concentrations in the deeper weathered shale aquifer. The performance of the proposed well was analyzed by an analytical method. Results of the analysis indicated that the extraction well should reduce contamination in less time than required for the shallow glacial till aquifer. Validation of the predicted performance of the remedial system will be assessed following installation of the system and collection of field data.

No abstract