Business Objective

A petroleum client received notice from the local air district that, per the State of California’s Air Toxics “Hot Spots” Information and Assessment Act (AB 2588), they were required to submit an air toxics emission inventory report. Working directly with the client’s environmental staff and contractors, the emissions report was prepared and submitted to the agency. The toxic chemical emission levels were such that a health risk assessment (HRA) was required. ALG prepared the HRA using industry standard dispersion modeling and health risk modeling.

Technical Approach

For the toxics emission inventory, ALG worked with client staff to identify all relevant emission sources for the reporting year. A data needs list (primarily product throughputs and operating hours) was provided to the client and emissions were calculated using District-approved methodologies including emission factors and source tests.

Preparation of the HRA involved two primary tasks – dispersion modeling to estimate ambient concentrations of specific air toxics, and health risk modeling that translates exposure to these predicted concentrations to an incremental health risk. Dispersion modeling was performed using the latest version of the AERMOD dispersion model along with district-approved meteorological data and source parameters provided by the client. Dispersion modeling followed district recommended methodology. Cancer, chronic, and acute health risk, based on the reporting year emission rates, was determined following the California Office of Environmental Health Hazard Assessment (OEHHA) and local air district guidelines. ALG communicated regularly with district modeling staff to ensure the modeling approach would meet district approval, minimizing the need for future HRA revisions. A comprehensive HRA report was provided to the client and the District that met all OEHHA and district requirements.

The results of the HRA triggered a public notice requirement. ALG assisted with identifying residences and businesses to notify and helped create presentation material for the public meeting.

Results

The toxics emission inventory and HRA were completed and submitted prior to district deadlines and within budget. District comments on the original HRA report were minimal and easily addressed and no modeling revisions were required, minimizing costs for the client. ALG analyzed the HRA results and identified particulate matter from contractor diesel engines as a significant contributor to offsite cancer risk. ALG provided guidance to the client regarding ways to reduce diesel particulate matter emissions and potentially fall below the public notification level in future HRAs. This proposed control approach, while not required by regulation, was used as a key element in the facility’s public outreach.