West Rancho Dominguez Emissions Investigation

South Coast AQMD is conducting special air monitoring in the West Rancho Dominguez area to assess levels of the toxic compound hexavalent chromium.


In June 2019, South Coast AQMD staff began extensive air monitoring to evaluate levels of hexavalent chromium in West Rancho Dominguez, which is an industrial area within the AB 617 Wilmington, Carson, West Long Beach community. Ambient air monitors were installed at 10 different locations within a two-block area. Data collected from these sampling locations in West Rancho Dominguez showed elevated levels of hexavalent chromium. The highest level, collected from a single monitor reading, was 17.75 nanograms per cubic meter (ng/m3) on June 20th (Monitoring Data and Map).

Typical background levels for hexavalent chromium in the South Coast Air Basin are 0.06 ng/m3 and 0.11 ng/m3 in the Compton area, averaged over one year (MATES IV). These background levels represent what would be expected in residential or commercial areas, and levels in industrial areas with sources of hexavalent chromium are expected to be higher. 

As noted earlier, this is an industrial area and the nearest residents are in a mobile home park located upwind from the industrial area less than a quarter mile to the west. An 11th monitor was recently installed at the mobile home park, and preliminary data has shown very low levels of hexavalent chromium thus far. An additional neighborhood is located downwind just over a quarter mile to the southeast, where additional monitors have been placed.

Investigation and Enforcement Actions

In response to initial monitoring results, inspectors investigated all potential hexavalent chromium emission sources in the vicinity of the monitors. Those sources included: Coast (Valence) Plating, a chromic acid anodizing facility; Accu-Crome, a hard chromium electroplating facility; and two concrete batch plants operated by A&A Ready Mixed Concrete, which can potentially contain hexavalent chromium material. Bulk sampling and handheld XRF (X-Ray Fluorescence) analysis were conducted at these facilities and in the surrounding area, and the presence of hexavalent chromium was confirmed. South Coast AQMD staff met with both Accu-Crome and Coast Plating to identify voluntary actions that could be implemented immediately. In response, the facilities made improvements to building enclosures and to their housekeeping measures, both of which should reduce emissions.

A Notice of Violation was also issued to both A&A facilities for violations of Rule 403-Fugitive Dust, for allowing track-out from the two facilities in excess of 25 feet. Another facility in the monitoring area, Multi-Spec, was found to be spraying hexavalent chromium-containing paint in violation of Rule 1469.1-Spraying Operations Using Coatings Containing Chromium, for which staff issued a Notice of Violation. 

Overall, levels of hexavalent chromium in the area have shown a generally decreasing trend, although we still observe variations in the levels. Therefore, conclusive results would require further efforts, as described below.

Next Steps

As part of this ongoing investigation to identify and address sources of hexavalent chromium in West Rancho Dominguez, South Coast AQMD staff will continue air monitoring that will expand to nearby residential areas. In addition, follow-up monitoring surveys will be conducted in Fall of 2019. Finally, inspectors will continue to investigate potential sources in the area, conduct surveillance in the vicinity of the monitors, and take enforcement action, as appropriate.

Related Information


Please contact us at 1-800-CUT-SMOG or file a complaint online, if you have information that can assist us in the investigation of sources of hexavalent chromium in the area. If desired, the information can be provided anonymously.


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South Coast Air Quality Management District

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