DDW to Lower Perchlorate Detection Limit for Purposes of Reporting

On March 9, 2020 the State Water Resources Control Board (SWRCB) Division of Drinking Water (DDW) issued a Notice of Proposed Rulemaking and Initial Statement of Reasons (ISR) to lower the perchlorate detection limit for purposes of reporting (DLR) from 4 µg/L to 2 µg/L.

This afternoon (July 20, 2020) DDW released the enclosed documents that modify the March 9th proposal (revised_regtext_15day_perchlorate_070820 draft_israddendum_perchlorate_dlr_070820 notice_perchlorate_15day).  In the enclosed documents, DDW is proposing a two phase approach to the lower the perchlorate DLR.  The first phase will be to lower the DLR to 2 µg/L.  The second phase is to lower the DLR to 1 µg/L, effective January 1, 2024.   This revised proposal is open for a 15-day public comment period (comments are due by August 7, 2020).


The perchlorate Maximum Contaminant Level (MCL) is 6 µg/L and as stated above the current DLR is 4 µg/L.  In 2015 the Office of Environmental Health Hazard Assessment (OEHHA) lowered the perchlorate Public Health Goal (PHG) from 6 µg/L to 1 µg/L.  In 2017, DDW presented a two-step process for possibly lowering the perchlorate MCL from 6 µg/L to a level closer to the PHG of 1 µg/L.  The first step involves lowering the DLR.  The intent of lowering the DLR would be to generate statewide occurrence data for perchlorate below the current DLR of 4 µg/L.  Using occurrence data collected with a lower DLR, in the second step, DDW may propose lowering the MCL from 6 µg/L to a level as close to the 1 µg/L PHG as technologically and economically feasible.

[Note: on a separate topic, the enclosed information includes the proposal to readopt the definitions of “Potential Contaminating Activity” and “Source Water Assessment” back into Title 22 regulations.]

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About Dan Askenaizer

Dr. Askenaizer leads WQTS’ work on regulatory compliance support for many of our water agencies clients. Dr. Askenaizer tracks water quality and treatment regulations at the Federal and State levels and provides regulatory updates to our clients. Dr. Askenaizer has strong expertise in the development of Regulatory Monitoring and Compliance Plans (RMCPs), which he has completed for a number of water agencies. He has also been working on a number of projects dealing with the development of distribution system monitoring plans and review of nitrification control strategies. Prior to joining WQTS, Dr. Askenaizer was the Water Quality Manager for the Glendale Water and Power. Under his leadership, the Water Quality Group conducted a demonstration-scale study of chlorite for nitrification control and a pilot-scale study of biological treatment for removal of nitrate. Dan has 30 years of experience working on projects dealing with regulatory, water quality and public health issues. Dan has given numerous presentations at workshops and round-tables across the country for water utilities. Dan was instrumental in developing and implementing a Mentoring Program for water staff and was involved in a Sustainable Development team.