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Flag City, California INNOVEX was retained by New West Petroleum to assist with bringing the site into compliance with a Cleanup and Abatement Order issued by the California Regional Water Quality Control Board. Due to the presence of methyl tertiary butyl ether (MTBE) reported in wells down gradient of the New West facility, the San Joaquin Environmental Health Department (SJEHD) directed New West to investigate potential impacts to soil and groundwater at the facility. Elevated concentrations of MTBE were detected in soil and groundwater, indicating that a release had occurred from the facility.  The MTBE plume created by this release contained one of the highest concentrations of MTBE in California history. To further complicate matters, the site’s aquifer was composed of numerous continuous and discontinuous layers of silt and sand allowing the MTBE to readily migrate throughout the soil and groundwater toward nearby municipal wells.

Based upon the site hydrogeology and potential impacts to nearby municipal wells, INNOVEX recommended an aggressive approach to control the plume. The remediation plan consisted of operating a Groundwater Extraction (GWE) remediation system to control the MTBE migrating off site and protect down gradient receptors. The GWE system extracted groundwater from the subsurface, routing it to a treatment system via subsurface piping, and discharging to the storm drain system via National Pollution Discharge Elimination System (NPDES) permit.  The remediation system piping network was installed by using horizontal borings to accomplish the subsurface trenching.  These horizontal borings limited the amount of surface disruption to the existing asphalt of nearby properties, and eased access negotiations with multiple stakeholders. This system served as the most effective technology to provide hydraulic control of the contaminant plume and allowed treated groundwater to be safely discharged to White Slough.