ABSTRACT

ABSTRACT: Collection of oriented core is an effective tool where detailed structural geologic analysis is necessary to identify and quantify contaminant migration pathways and structurally complex sedimentary bedrock sites. These subsurface features include fractures, faults, and variable bedding thickness, lithology, and continuity. This paper focuses on the application of the method to a specific environmental investigation, and summarizes the methodology and procedures, and advantages/disadvantages. The case history involves a hydrocarbon remedial investigation in Los Angeles, California (Meredith/Boli & Associates, 1994, 1997, 1997a). Thinly interbedded, fractured sedimentary rock of Miocene-age Puente Formation underlies the site. Structural and lithologic information obtained from oriented core provided an understanding of migration pathways within permeable sandstone laminae interbedded with impermeable fine-grained strata. These hydrocarbonbearing strata in turn were interconnected by two near-vertical fracture sets prominent within the contaminant plume. These fractures permitted the hydrocarbons to migrate via a laminae-fracturelaminae sequence across impermeable bedding thus providing the necessary transport mechanism for hydrocarbons movement.