Impacts and Issues of Refining on Regional Groundwater, Los Angeles Coastal Plain, California

Stephen M. Testa
Testa Environmental Corporation, Mokelumne Hill, CA

The Los Angeles coastal plain was a prime location for the construction of numerous petroleum-handling facilities during the 1920s, notably, in the area along the Newport Inglewood Structural Zone. Numerous light non-aqueous phase liquid (LNAPL) hydrocarbon pools and associated dissolved hydrocarbon plumes occur beneath these facilities. Extensive pools occur in the Carson-Long Beach area, within the West Coast Basin. These pools occur as isolated perched zones of limited lateral extent, and relatively large pools encompassing tens to hundreds of acres in lateral extent. The cumulative estimated volume is on the order of millions of barrels. LNAPL recovery efforts were initiated in the late 1970s, and by the mid-1980s all major petroleum handling facilities implemented LNAPL recovery and groundwater quality and behavior monitoring programs. The Carson Regional Groundwater Group (CRGG), a consortium of facility owners in the Carson-Long Beach area, was established in 1990 to coordinate pool and plume delineation, LNAPL recoverability, and overall synchronized monitoring of fluid levels. Over the past decade, the lateral on- and off-site extent of LNAPL pools have been delineated, individual LNAPL pools further characterized via forensic fingerprinting, dissolved plumes further delineated, groundwater quality within the primary water-bearing zones assessed, and models developed to evaluate regional groundwater behavior. In addition, over a million barrels of LNAPL has cumulatively been recovered. A decade later, however, questions relating to larger regional issues remain uncertain. These issues include plume(s) containment, adversely impacted upper Gage aquifer, potential adverse impact on the intervening Lynwood (guardian) aquifer, hydraulic impacts associated with groundwater withdrawal from the lower and heavily utilized Silverado aquifer and barrier projects, hydraulic communication between aquifers, potential impact of those constituents of relatively higher solubility within underlying water-bearing zones, and source(s) identification.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005