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 conducting 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. Sampling equipment was installed at 14 different locations within a two-block area. Data collected from these locations showed elevated levels of hexavalent chromium.  

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. 

The nearest residents are 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 these residential locations, through mid-September, has shown hexavalent chromium to be within typical levels for residential/commercial areas.

Investigation and Enforcement Actions

South Coast AQMD is investigating 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, which can potentially contain hexavalent chromium. 

South Coast AQMD has also been working 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 already implemented and should help to reduce fugitive emissions.

Recent amendments to Rule 1469 for chromic acid anodizing and plating facilities require additional pollution controls on certain tanks that were previously unregulated. Coast Plating has two such tanks and is working with the South Coast AQMD to install pollution controls.  Coast Plating has submitted eight applications for changes to the facility that will significantly reduce emissions of hexavalent chromium and additional applications for further changes are expected.  Applications for modifications to reduce hexavalent chromium emissions are also expected from Accu-Chrome Plating and Grinding.

Notices of Violations Issued

See Compliance & Enforcement page

Next Steps

South Coast AQMD will continue to monitor the situation, collect and analyze air samples, conduct facility inspections, 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.


Newsletter Sign Up
Periodic newsletter updates via Email on a variety of air quality-related topics

South Coast Air Quality Management District

21865 Copley Dr, Diamond Bar, CA 91765



© 2019 South Coast Air Quality Management District