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.

Recent Update

South Coast AQMD has completed its investigation of hexavalent chromium emissions in the West Rancho Dominguez industrial area. The investigation began in 2019 and discovered elevated levels of hexavalent chromium near three facilities in the area. Following enforcement actions – which were accompanied by additional enclosures, improvements to housekeeping, and other actions at the identified facilities – levels of hexavalent chromium have significantly declined.

South Coast AQMD therefore concluded its investigation and ended its special air monitoring efforts. However, the agency continues to periodically monitor and check for any issues that could warrant enforcement action.


In June 2019, South Coast AQMD identified elevated levels of hexavalent chromium in the West Rancho Dominguez industrial area and began special air monitoring efforts, as well as an investigation into potential sources of emissions.

Sampling equipment was installed at 13 different locations within a two-block area.

Typical levels of hexavalent chromium in the South Coast Air Basin and the Compton area are 0.04 ng/m3 and 0.06 ng/m3, respectively (South Coast AQMD MATES V study). 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 indicate that the hexavalent chromium levels in the residential areas are far lower than the levels found in the industrial area. Additionally, overall hexavalent chromium levels have significantly declined from 2019 through present, indicating that hexavalent chromium exposure risks to residents have decreased.

Investigation and Enforcement Actions

South Coast AQMD’s investigation evaluated potential emission 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. (Note: 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 immediately 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 to further reduce hexavalent chromium emissions.

Coast Plating shut down its operations in early 2021, and recent ambient monitoring data in the vicinity showed levels of hexavalent chromium have decreased.

Accu Chrome fully enclosed its grinding and polishing area to control emissions of chromium-containing dust those operations. Additionally, the facility completed upgrades to its emissions collection system for chrome plating operations to ensure that 100% of plating emissions are captured and vented to the emissions control system.  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 addressed fugitive dust issues by enhancing their housekeeping procedures at both sites, increasing the frequency of street sweeping and purchasing an upgraded sweeper.

Notices of Violations Issued

See Compliance & Enforcement page

Related Information


Members of the public may contact South Coast AQMD at 1-800-CUT-SMOG (1-800-288-7664) or file a complaint online, to report hexavalent chromium emissions or any other air quality issue. If desired, complaints may be submitted anonymously.

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