South Bay Odor Attribution Study

Learn about the Air District’s efforts to minimize odors in Milpitas and the surrounding communities.

Odor issues have been ongoing for many years in Milpitas and the surrounding communities in the South Bay. Population density and proximity of residential housing and public spaces to the landfill, transfer station, sewage treatment plant, and compost and organic waste processing operations continue to affect air quality. While there have been improvements to air quality in the area, odors continue to be a concern.

Since 2015, Air District staff have been active participants in the South Bay Odor Stakeholders Group (SBOSG) meetings, which were initiated to steer development and implementation of an odor study required by the City of San Jose as part of the approval of a landfill expansion project at the Newby Island Resource Recovery Park. This forum provides an open and transparent space to discuss enforcement activities, permit and regulatory requirements, and odor mitigation and control measures alongside municipal leaders, private industry, state and local regulators, members of the community, and elected officials.

Odor Attribution Study

In 2019, the Air District committed to conducting an Odor Attribution Study to identify odorous compounds impacting the local community and characterize the odors generated by three closely located facilities with similar odor profiles (Newby Island Resource Recovery Park, San Jose-Santa Clara Regional Wastewater Facility, and Zero Waste Energy Development), as well as other potential odor sources in this area. The goal of the study was to determine the contribution and variability of odors from these facilities and any other sources in the vicinity, as well as support a strategy to reduce the odors impacting the local community.

The Air District recently completed the Odor Attribution Study, which consisted of an overall source attribution study and a targeted odor compound fingerprint study. The source attribution study characterized the diurnal and seasonal odors through focused field sampling and data collection, while the targeted odor compound fingerprint study was a preliminary screening to identify compounds for further investigation.

Findings and Next Steps

The findings from the study revealed that landfill gas is the primary driver for community complaints, though there are other sources that also contribute to odors in the community. Based on the findings, the Air District will work with the facilities and agency partners to mitigate the odors and will use our rulemaking, permitting, and enforcement authorities, where deemed appropriate, to employ additional operational measures aimed at emission and odor reductions. In particular, to reduce releases of landfill gas, the Air District plans to:

  • Strengthen enforcement, including enhanced inspections at the landfill facility, and
  • Assess odor minimization measures in applications for new or modified source permits.

The California Air Resources Board is currently updating their landfill methane rule, which may help with minimizing emissions.

Members of the public are encouraged to report ongoing air quality complaints to the Air District. Visit the Air Quality Complaint Program web page for more information.

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Last Updated: 2024/3/8