Groundwater Contamination Prevention Program

Perchlorate Cleanup Project in the Los Angeles Forebay


Project Background:

The Water Replenishment District (WRD) is currently investigating and will be cleaning up perchlorate in groundwater with the assistance of various regulatory agencies in association with our Los Angeles Forebay Groundwater Task Force. The perchlorate concentrations detected in groundwater are among the highest in the state and the impacted groundwater is currently located in a deep aquifer system within the Los Angeles Forebay. This is a particularly sensitive area of the basin as the groundwater (along with contaminants) can migrate through the coarse-grained sediments directly into the regional aquifer system representing a substantially imminent threat to the Central Basin and West Coast Basin (or CBWCB). In fact, perchlorate has already been detected at elevated levels and is currently having to be addressed in at least two municipal water supply wells located down-gradient of the City of Vernon. The source of the perchlorate is unknown and a responsible party (RP) has not been identified by the either the Department of Toxic Substances Control (DTSC) or Los Angeles Regional Water Quality Control Board (LARWQCB). 

WRD successfully applied for and received a grant for over $7 million from the State Water Resources Control Board (SWRCB) through the Proposition 1 Groundwater Grant Program (Proposition 1). The State grant funds will help pay for approximately 80% of the cleanup construction costs to address the perchlorate impacts along with other comingled volatile organic compounds (VOCs). In 2021, a groundwater extraction and treatment system will be installed to immediately reduce contaminant concentrations within the perchlorate "hot spot" to help prevent any further migration into the CBWCB. Additional data will be collected during the investigation phase to help support the various regulatory agencies in identifying the perchlorate source and yet to be determined RP. 


An estimated timeline for key project milestones is as follows:


WRD has already conducted an extensive amount of work to identify and address the contamination issues in the Los Angeles Forebay. In 2015, WRD constructed three deep-nested groundwater monitoring wells to delineate the occurrence of perchlorate in the City of Vernon. In 2016, WRD analyzed perchlorate remedial technologies and prepared cost estimates with the assistance of their on-call environmental consultant WorleyParsons. WRD submitted a grant proposal for the project on November 18, 2016.  A preliminary grant award was issued on March 30, 2017.  The grant agreement was signed by the State Water Board on November 21, 2018.


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Project Goals & Desired Outcomes
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The project goals, desired outcomes, and project lifetime are summarized as follows:

Performance Measure #1: Water That Is Prevented from Becoming Contaminated

The goal is to reduce the overall area of the perchlorate ‘hot spot’ through the installation of a groundwater extraction and treatment system capable of reducing the overall area by 90% and prevent the migration of perchlorate to municipal supply wells and concurrently treat other regional constituents like VOCs.  By reducing the area of perchlorate, less mass will be available for migration to municipal water supply wells in and around the City of Vernon.

Performance Measure #2: Mass Removal Target

The goal is to remove an estimated one thousand (1,000) pounds of perchlorate mass from groundwater in the vicinity of the ‘hot spot’ at monitoring well MW-03.  Samples will be collected from the groundwater treatment system to calculate mass removal for the Project.  The removal of perchlorate mass from the aquifer system will have a beneficial effect and prevent ‘hot spot’ concentrations from migrating to municipal water supply wells in an around the City of Vernon.

Performance Measure #3: Number of Contaminated or Threatened Municipal Wells That Will No Longer Be Contaminated or Threatened

The goal is to protect drinking water supplies and enhance local water supply reliability by remediating the perchlorate ‘hot spot’ in and around monitoring well MW-03.  Our desired outcome is the protection of 13 municipal water supply wells located in an around the City of Vernon (defined above in Section I.B).

Performance Measure #4: Percent Reduction in Concentration of the Contaminant

The goal is to significantly reduce perchlorate concentrations in the ‘hot spot’ which is defined by an area containing perchlorate concentrations exceeding 1,000 µg/L as defined in the grant submittal to the SWRCB with the highest perchlorate concentrations centering around groundwater monitoring well MW-03.  It is estimated the groundwater extraction and treatment system can reduce the perchlorate concentration in this well by 98%

Additional info is provided in the Project Assessment & Evaluation Plan available here