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 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 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 have shown has shown hexavalent chromium to be within the range of 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 include: Coast Plating (Valence Surface Technologies), a chromic acid anodizing and metal finishing facility; Accu-Crome 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 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 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.

Coast Plating has conducted some operational changes that are expected to considerably reduce hexavalent chromium emissions from the facility. One of the facility’s equipment, the sodium dichromate seal tank, was previously operating without any pollution controls. South Coast AQMD approved a permit for this tank to install controls under the new requirements for Rule 1469, but that equipment has been voluntarily removed from use and the permit for the tank has been inactivated. Additionally, the company has removed one spray booth, which was used for applying coatings containing hexavalent chromium, from operations.  The company has also cancelled plans to install two new spray booths at its facility.

Recent ambient monitoring data in the vicinity of Coast Plating has shown ambient levels of hexavalent chromium have decreased since these actions were taken.  

Accu-Crome has taken efforts to fully enclose the grinding and polishing area of the facility and is evaluating options to modify its air pollution control system to reduce hexavalent chromium emissions from its facility.  

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, 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



© 2020 South Coast Air Quality Management District