Liquid Gold Oil Corp.

Investigation and Cleanup Activities

This site was addressed in two stages: initial actions and a long-term remedial phase focusing on cleanup of the entire site.

Initial Actions

Initial Actions: In response to inspections and regulatory actions, some surface soil was removed in 1974, and liquid waste and soil from a drainage area and holding pond were removed in 1980. Twenty five storage tanks and more than 70 drums of hazardous waste were removed and disposed off-site from 1982-84. In 1985, 760 cubic yards of contaminated soil were excavated and a wooden building in the former asphalt facility removed, resulting in off-site disposal of an additional 65 cubic yards of wood and metal debris. The remaining site buildings were demolished and the debris disposed off-site in 1989.

Site Studies

Site Studies: Under State supervision, the potential responsible party prepared a Remedial Investigation (RI)/Feasibility Study (FS) Workplan for the site in 1988 and RI/FS activities were conducted during 1988-1992. These studies were summarized in a Remedial Action Plan (RAP), approved by the Department of Toxic Substances Control and EPA in 1993. The study results indicated elevated concentrations of lead, copper, and mercury in surface and subsurface soils. The elevated lead was found primarily in a 5-acre area in the central portion of the site. Polynuclear Aromatic Hydrocarbons (PAHs) were found in five surface soil sample located within the same 5-acre area. Oil and grease were found throughout site soils, though a source could not be identified.

Groundwater was also sampled and analyzed, and continues to be monitored. The groundwater contained elevated metals and petroleum hydrocarbons (diesel and gasoline). Ongoing monitoring indicates that contaminated groundwater is not migrating and that concentrations of contaminants are decreasing over time. Surface water samples from two drainage channels showed no surface water contamination.

An ecological risk assessment found evidence of possible ecological damage in two drainage channels leading from the site into San Francisco Bay. This was based on the observation that the species composition of sediment-dwelling organisms was typical of a community subject to petroleum contamination. In addition, mussel larvae exposed to marsh sediments exhibited a toxic response, though this response could not be linked to site chemicals.

Remedy Selected

Remedy Selection: Final clean-up actions (Final Remedy) are summarized in the Remedial Action Plan (RAP), approved the Department of Toxic Substances Control on March 15, 1993. EPA concurred with the RAP by signing a Record of Decision on June 21, 1993. The Final Remedy included excavating contaminated sediments from the drainage channels, placing these with contaminated soils from a used oil recycler, and constructing a vegetated soil cap to cover these soils and sediments. In addition, a deed restriction prohibiting residential development at the site was signed and recorded. These remedial activities were completed during 1995. Monitoring of the cap and the groundwater continues. The site was deleted from EPA's National Priority List in September, 1996.

Site Studies

Three Five-Year Reviews, which determine if the site is protective of human health and the environment, have been completed (2000, 2005, and 2010). The most recent review (2010) concluded that the remedy at the Liquid Gold Site protects human health and the environment, because all immediate threats at the site have been addressed through the removal of contaminated material, stabilization and capping of on-site contaminated soils, access restriction (fencing, warning signs), regular maintenance of engineered control structures, and institutional control (deed restriction that restricts land uses). However, in order for the remedy to be protective in the long-term, the potential responsible party must update the deed restriction to comply with current California regulations and finish realigning the fence to completely enclose the vegetated cap. The report also recommends several follow-up actions to improve the groundwater monitoring program.