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Refinery HRA - Expansion Project

Business Objective

ALG was contracted by a West Coast refinery to prepare new source review authority to construct applications and to prepare supporting technical analyses for a major refinery modification. The project faced detailed public review and agency scrutiny; and ALG was selected based on our understanding of refinery operations, and extensive prior experience in conducting health risk assessments for petrochemical facilities consistent with agency-approved protocols and guidelines.

Technical Approach

ALG staff conducted refined air dispersion modeling and prepared a health risk assessment (HRA) for the proposed refinery expansion project. Separate analyses were prepared in support of the project's Environmental Impact Report to satisfy the California Environmental Quality Act, and for the local air district's New Source Review permit applications. Unlike pre-construction review analyses, the EIR HRA included emissions from project stationary sources and the expected increases in diesel-fueled truck emissions within the facility. Under California risk guidelines, diesel particulates are considered carcinogenic and have relatively high unit risk values. ALG worked closely with air district staff to establish acceptable modeling procedures to define the appropriate source/receptor relationships. The U.S. EPA's AERMOD was used for the air dispersion modeling and the California Air Resources Board's Hotspots Analysis and Reporting Program (HARP) risk assessment model was used to calculate the potential health risks of project stationary source emissions of toxic air contaminants. Iterative analyses and refinements were conducted to assure compliance with various local agency incremental health risk guidelines.


The HRA results demonstrated compliance with carcinogenic and non-carcinogenic health risk thresholds, allowing certification of the EIR and issuance of Permits to Construct. This technical analysis was subject to intense scrutiny from members of the public adverse to the planned expansion, as well as federal and state agencies. ALG also provided testimony in response to public officials responsible for the review and approval of the project.

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