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DNA Manufacturer - Dispersion Modeling

Business Objective

A DNA manufacturing company, located in southern California, sought to move and expand its operations. Unlike its existing facility, the new corporate campus was to be located proximate to residences and other sensitive receptors. A key objective for the company was to preserve operational flexibility among different manufacturing technologies, and to provide for continued growth of the company's product line. ALG was selected to perform all impact and dispersion modeling, associated incremental health risk analyses, and to prepare the applications for an Authority to Construct.

Technical Approach

In close coordination with our client's environmental and technical staff, ALG first compiled an inventory of volatile organic compound (VOC) and toxic air contaminant (TAC) emissions from facility research, production, and laboratory operations. Engineering data indicated very low concentrations of target compounds and relatively high exhaust flows. Therefore, the VOC and TAC control strategy was developed to capture the more toxic of these emissions, which would be directed to a highly efficient control device. The uncontrolled fraction of these emissions, as well as smaller process streams would be released to the atmosphere via the building's general high volume ventilation exhaust vents on the rooftop. These uncontrolled emissions contributed to incremental health risks, and accurate data were critical to proper impact analyses. ALG used the California Air Resources Board's Hotspots Analysis and Reporting Program (HARP) risk assessment model to calculate the potential health risks of these toxic air contaminant emissions to residents and workers in the areas neighboring the facility. In this situation, on-site building downwash and terrain variations both on-site and off-site were important considerations, and these effects were provided the full treatment incorporated into the Industrial Source Complex model, which is a built-in component of HARP. In addition, ALG provided technical guidance on the need for alternative control technologies to assure compliance with the new EPA 1-hour nitrogen dioxide standard. We also leveraged our working experience with local district engineering staff to allow for review and approval of all technical data within a compressed schedule.


The HRA results demonstrated compliance with carcinogenic and noncarcinogenic health risk thresholds, allowing for issuance of Authority to Construct permits and streamlined review. The facility was able to transition into its new production facility with no extended downtime, and the permit terms allow for continued expansion of product lines.

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