The Department of Toxic Substances Control (DTSC), pursuant to authority granted under Chapter 6.8, Division 20, section 25300 et seq is considering approving an Explanation of Significant Differences (ESD) which proposes secondary remedy technologies to the 1997 Remedial Action Plan (RAP) for the GBF/Pittsburg Landfill (Site). The Site is a capped and closed 84-acre landfill located northeast of the intersection of Somersville Road and James Donlon Boulevard in the City of Antioch (see Figure 1). Due to historical operations, groundwater beneath the landfill is contaminated with primarily volatile organic compounds. DTSC is supervising the long-term monitoring and restoration of the groundwater in the area.
The proposed Explanation of Significant Differences (ESD) proposes the following secondary remedy technologies: (1) installation of a hydraulic barrier wall, (2) a redesigned on-site GWETS, (3) an on-site soil vapor extraction and treatment system (SVETS), (4) in-situ groundwater remediation at two off-site locations, and (5) risk-based mitigation, where unacceptable indoor air risk from off-site soil vapor would be addressed on a case-by-case basis. The secondary remedy technologies would not fundamentally alter the overall cleanup approach. The remedial action objectives (RAOs) are and will continue to be containment of contamination, reduction of contamination, and attainment of standards which protect the beneficial uses of the waters.
Activities associated with the ESD would occur over an approximately 23-week period.