Abstract: Remedial Solutions for Impact to Perched and Ground Water within Quaternary Alluvial Deposits of the Niles Cone, Southwestern Alameda County, California

Richard H. Green

Historical industrial operations in southwestern Alameda County have impacted water quality to the extent that remedial solutions are necessary for restoration of existing contamination and Protection against future impact. These operations included utilization of almost every regulated industrial byproduct, including petroleum hydrocarbons, metals, volatile and semi-volatile organic compounds, polychlorinated biphenyls and organic pesticides.

Detectable concentrations of these byproducts occur in a variety of geologic settings, resulting in impact to surface, meteoric, perched and ground water systems. Consequently, numerous remedial designs have been implemented or are proposed, including hydraulic containment, pre-disposal treatment, capping to divert and reduce infiltration, and removal of impacted materials. As additional assurance, advective/dispersive transport modeling has been conducted to predict concentrations in ground water at the nearest down-gradient receptor.

A particularly creative remedial design is planned for perched water and ground water affected by impacted artificial fill deposits. These porous, permeable fill materials were placed in former clay mine excavations to depths as great as forty feet, and will not be removed under the intended remedial action because of the tremendous quantities of materials (approximately 400,000 cubic yards) which were deposited during industrial operations. To protect water quality, a combination capping/containment/monitoring design will be implemented, with capping as the key element of the overall design. Effectiveness of the cap design has been predicted using the Hydrogeologic Evaluation of Landfill Performance (HELP) model. Results indicate a 99 % infiltration reduction is achievable.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California