California Experience with Air Toxics Health Risk Assessments for Proposed New Power Plants

摘要

The deregulation of electrical generation in the State of California was authorized by the September 1996 passage of California State Assembly Bill 1890 and took full effect in March 1998. This restructuring of California's electric system stimulated numerous applications for new and repowered thermal power plants. A primary public concern about these new power plant projects is the potential human health impacts of their air emissions. This paper examines the public record of Applications for Certification (AFCs) submitted to the California Energy Commission (CEC) for proposed new projects under CEC jurisdiction since deregulation. The public health analyses of approved projects and pending projects with published CEC staff assessments are studied, and the general methodologies used to evaluate potential public health impacts are summarized. All of the studied power plant projects, with the exception of two, are natural-gas-fired turbine-based combined-cycle plants or simple-cycle "peaker" plants. One factor that could impact estimated human health risks is the configuration of the plant (fuel and thermodynamic cycle). Other potential factors include date of analysis (since emission factors, toxicity factors, and other risk assessment assumptions are periodically updated) and location of projects (since meteorological factors and proximity to complex terrain affects atmospheric dispersion). To assess the potential importance of individual factors in overall risk estimates, the various CEC projects are categorized by appropriate factors (type of plant, size of plant, date of analysis) and evaluated relative to calculated health risks. In addition, issues that have surfaced during the CEC staff analyses are discussed. These issues include estimated impacts from diesel-fired emergency equipment used during operation, and from specific compounds, such as measurement uncertainties and toxicity factors associated with acrolein. The relative magnitude of health risk posed by new natural-gas-fired power plants was found to be low across the range of plant capacities. This and other lessons learned from the California experience are discussed.