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Preliminary Endangerment Assessment (PEA), Hercules, CA

In order to comply with the State requirement for new school construction projects, the West Contra Costa Unified School District requested assistance from the Department of Toxic Substances Control (DTSC) for providing a PEA for a potential school site. Accord Engineering was retained by DTSC to provide this PEA under a Brownfield grant from the U.S. EPA. The project site was owned by the City of Hercules at the time of investigation.

The property was previously used as a wastewater treatment facility with an ammunition powder manufacturer located in close proximity. A comprehensive soil gas, soil, and groundwater sampling event was conducted. A total of 16 soil gas samples, 62 soil samples and 10 groundwater samples, were collected during a 5-day fieldwork period. The soil gas samples were analyzed on real-time basis in the field. The gas sampling results were immediately used for guiding the soil and groundwater sampling strategy. Groundwater testing included explosives because of the previous usage of the site.

Many of the samples were collected within very tight work spaces with limited access. Accord Engineering was able to overcome these challenges by working closely with the on-site operators and City staff to complete the fieldwork safely, on schedule, and within budget. A screening-level environmental risk assessment was conducted based on the sampling results. A PEA report was subsequently prepared, which included summarized of the sampling results; a conceptual site model; risk assessment calculations; and recommended risk-based cleanup goals. The report was reviewed and approved by DTSC and the U.S. EPA with minimal comments.

More pictures from this very important project