The Baldwin Park Operable Unit (BPOU) site includes an 8-square-mile area of groundwater contamination underlying portions of the cities of Azusa, Irwindale, Baldwin Park, West Covina, La Puente and Industry. Contaminants include perchlorate, nitrate, NDMA, 1,4-dioxane, and volatile organic compounds (VOCs).

Of the areas of contamination in the Basin, the BPOU is considered the most significant because of the geographic size and degree of contamination. For this reason, the U.S. Environmental Protection Agency (EPA) prioritized this area for investigation in the late 1980s.

By 1994, there was a general consensus on the technical approach, including a financial arrangement under which sales of the water produced by the treatment plant would be used to offset the costs of the project. However, just as designs were being prepared, the discovery of perchlorate prompted a complete reevaluation of cleanup plans.

In 1999, due to the critical need for immediate action, the San Gabriel Basin Water Quality Authority (WQA), Main San Gabriel Basin Watermaster, and Upper San Gabriel Valley Municipal Water District joined resources and began implementing the plan by constructing the first facility to treat both perchlorate and n-nitrosodimethylamine for drinking water at the La Puente Valley County Water District (LPVCWD) well site. Following the success of the LPVCWD project, WQA prescribed additional early actions that built on the LPVCWD project development model.

In 2002, eight of the 20 BPOU Potentially Responsible Parties entered into a comprehensive project agreement with WQA, the Watermaster and local purveyors to fund the prescribed 22,000-gallon-per-minute cleanup. The agreement formed the BPOU Project Committee, which meets monthly to manage the projects.

As of 2019, five groundwater extraction and treatment systems process more than 43 million gallons of water per day. More than 130 billion gallons of contaminated groundwater have been treated, and more than 80,000 pounds of contamination have been removed from the groundwater.

Additional information:

Appendix A in WQA’s Groundwater Quality Management and Remediation Plan (406 Plan)