Abstract

An innovative risk-based approach was used to evaluate and mitigate environmental conditions in an industrialized area of San Francisco, California, prior to development of a new baseball stadium (‘the Stadium’) for the San Francisco Giants (SBC Park, formerly Pac Bell Park). The redevelopment area historically contained a manufactured gas plant, along with other industrial facilities. The risk-based investigation focused on providing data required to evaluate the end use of the property as a sta-dium. To accomplish this investigation approach, a conceptual site model (CSM) was developed to identify the data needs required to evaluate potential exposure pathways. A focused investigation was implemented and the data were used to perform a risk assessment. Results indicated that residual coal tar, and chemicals associated with other previous site uses, could remain in place without posing an unacceptable risk to human health and the environment, given the intended site use. This risk-based approach resulted in the completion of the project in an expedited time frame, and minimized the remediation effort/costs by focusing on actions necessary to mitigate exposure pathways. The CSM also integrated specific components of the redevelopment plan as mitigation measures, such the use of the Stadium foundation as a ‘cap’ to limit contact with affected soil (e.g. coal tar waste). Post-closure guidelines were developed to address the health and safety of construction workers in the event that coal tar wastes were encountered during site construction. As a result, the Stadium was completed with minimal disruption to construction activities. Frequent communication between project stakeholders (i.e. property owner, regulators, and consultants) was key to the success of this risk-based approach.

Key words: chemicals of potential environmental concern, conceptual site model, manufactured gas plant, risk-based approach, site management plan