Remediation of a 3-Mile Hexavalent Chromium Plume in Hinkley, California - 18532

Pacific Gas and Electric Company (PG and E) is conducting assessment and cleanup of hexavalent chromium (Cr[VI]) in groundwater related to industrial activities from the 1950's and 1960's at the PG and E Hinkley Compressor Station near Barstow, California (the Site). The plume core undergoing remediation is approximately 4.8 kilometers long and 1.6 kilometers wide (3 miles long and one mile wide). In December 2015, a Cleanup and Abatement Order was issued which established cleanup requirements for the Site, including required cleanup time frames for the plume core undergoing remediation to reach 50 micrograms per liter (μg/L) across 90% of the plume by 2025 and to reach 10 μg/L across 80% of the plume by 2032. To reach the milestones at the scale of the site, remedy design includes a series of remedial system expansions and remedy implementation relies on an adaptive management scheme for continual performance evaluation and optimization. This presentation will detail the remedial approach, implementation and performance to date. (authors)