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.


Since June 2019, South Coast AQMD has conducted air monitoring to evaluate levels of hexavalent chromium in the West Rancho Dominguez industrial area. Sampling equipment was installed at 13 different locations within a two-block area. Data collected from some of the industrial locations showed elevated levels of hexavalent chromium. 

Typical levels of hexavalent chromium in the South Coast Air Basin and the Compton area are 0.06 ng/m3 and 0.11 ng/m3, respectively, 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.

The nearest residents to the sampling area were in a mobile home park located upwind from the industrial area less than a quarter mile to the west (site #11) and an additional neighborhood located downwind just over a quarter mile to the southeast of the area (site #14). Measurements at both of these residential locations showed hexavalent chromium to be within the range of typical levels for residential/commercial areas.

The investigation results issued in December 2020 indicate that the hexavalent chromium levels in the residential areas are far lower than the levels found in the industrial area. Also, the levels in 2020 are lower than the levels from 2019, indicating that hexavalent chromium exposure risks to residents have declined.

Although the investigation has largely been completed, South Coast AQMD continues to periodically monitor and check for any issues that would warrant enforcement action.

Investigation and Enforcement Actions

South Coast AQMD’s investigation reviewed potential sources in the vicinity of the monitors. Those sources included: Coast Plating (Valence Surface Technologies), a chromic acid anodizing and metal finishing facility; Accu Chrome Plating and Grinding, a hard chromium electroplating facility; and two concrete batch plants operated by A&A Ready Mixed Concrete (concrete typically contains hexavalent chromium).

South Coast AQMD worked with the facilities to identify voluntary actions that could be implemented immediately—such as improvements to building enclosures and to housekeeping measures—some of which have been implemented and have helped to reduce hexavalent chromium emissions.  Additionally, recent amendments to Rule 1469 for chromic acid anodizing and chrome plating facilities required additional pollution controls on certain tanks that were previously unregulated that can significantly reduce hexavalent chromium emissions.

The Coast Plating facility is in the process of shutting down, planned installations of new equipment has been cancelled and some of the highest-emitting equipment has been removed from service and the associated permits inactivated. Recent ambient monitoring data in the vicinity of Coast Plating shows that ambient levels of hexavalent chromium have decreased since these actions were taken. The remaining production operations are expected to cease in the first quarter of 2021.

The Accu Chrome facility fully enclosed its grinding and polishing area to control emissions of chromium-containing dust from the grinding and polishing operation. Additionally, the facility is in the process of upgrading its emissions collection system for the chrome plating operation to ensure that 100 % of the plating emissions are captured and vented to the emissions control system. This upgrade is scheduled to be completed in the first quarter of 2021. Furthermore, the facility has temporarily taken one of its four chrome plating tanks out of service to reduce the load on that emission control system. The fourth tank will not be returned to service until the emission control system is enlarged to handle the additional load that would result from returning it to service.

A&A Ready Mixed Concrete has addressed fugitive dust issues by enhancing their housekeeping procedures at both sites, increasing the frequency of street sweeping and purchasing an upgraded sweeper.

South Coast AQMD continues to work with facilities in the area to identify and address additional potential sources of hexavalent chromium.

Notices of Violations Issued

See Compliance & Enforcement page

Next Steps

South Coast AQMD will continue to monitor the situation, conduct facility inspections and also take enforcement action and further collect and analyze air samples, 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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