Plastics Manufacturing Facility

In 2014, Stratus Environmental, Inc. (Stratus) was retained by a confidential client to continue ongoing remedial actions at a former industrial facility. From 1958 to 2003, a PVC manufacturing plant operated at the Site that produced pelletized PVC for audio recording media. Raw materials stored on the site included vinyl chloride monomer (VCM), vinyl acetate, and trichloroethylene (TCE), as well as various stabilizers, defoamers, and suspension agents. During the time interval of PVC manufacturing, wastewater management practices transitioned from discharge to an unlined pond, to discharge of untreated wastewater to a publicly-owned treatment works (POTW), and finally, to on-site wastewater pretreatment and discharge to the POTW. PVC manufacturing operations ceased at the Site in 2003, and the facility was removed in 2004.

Prior to Stratus’ involvement, multiple remedial investigations were conducted at the Site. Soil vapor, soil, and groundwater sampling and laboratory analyses indicated that the primary chemical constituents of concern (COCs) are volatile organic compounds (VOCs), specifically 1,2-dichloroethane (1,2-DCA), cis-1,2-dichloroethylene (cis-1,2-DCE), tetrachloroethylene (PCE), toluene, TCE, and vinyl chloride.

A Site Conceptual Exposure Model (CEM) and Human Health Risk Assessment (HHRA) have been prepared for the site and site-specific risk-based concentrations for soil vapor and groundwater have been developed using Cal/EPA versions of the USEPA approved Johnson and Ettinger (J&E) vapor intrusion models, as well as indoor employee exposure parameters and toxicity values. Based on the Site’s CEM and HHRA, remedial action objectives and a Remedial Action Plan have been developed for both vadose soils and groundwater. The preferred remedial action alternative for the Site is SVE for treatment of vadose or unsaturated soils, and enhanced in-situ bioremediation (EISB) for treatment of dissolved-phase VOCs in groundwater. This conceptual design assumes emulsified vegetable oil (EVO) would be used as a carbon substrate source for EISB.

Short- and long-term SVE pilot tests have been performed at the Site to facilitate full-scale remedial design. To date, approximately 2,300 gallons of DNAPL (24,000 pounds) have been recovered via cryogenic recovery techniques. Stratus is currently finalizing the long-term SVE pilot test results and will subsequently develop a full-scale SVE system design for implementation.

The SVE system will be gradually expanded in stages over several years. During this time, pilot testing and design of EISB will be completed. Full-scale implementation of EISB is tentatively scheduled to begin approximately two years after the start of SVE operations. The duration of EISB to address VOC-impacted groundwater is expected to be five years.