In 2020 the California State Water Resources Control Board (SWRCB) adopted a State Policy for Water Quality Control: Toxicity Provisions (Provisions). Subsequently, the SWRCB sought approval of the Provisions from the US Environmental Protection Agency (EPA). On May 1, 2023, EPA Region IX officially approved the Provisions for use as a regulatory tool under the Clean Water Act (CWA).

How will these changes affect you?

This approval has the potential to affect all dischargers to inland surface waters, enclosed bays, and estuaries who hold a National Pollutant Discharge Elimination System (NPDES) permit containing toxicity testing requirements. Here are a few things to consider, as Regional Water Boards will likely begin incorporating the Provisions during your next permit renewal:

  • Many dischargers who previously had performance-based limits may now receive effluent limitations for toxicity.
  • Statistical analysis of toxicity data regulated under the Provisions will incorporate the Test of Significant Toxicity (TST), which is based on a single effluent concentration exposure. This is a departure from multiple concentration testing and the use of toxicity units (TUs) to determine compliance. Assessing test data variability is a key element of this statistical method.
  • Median monthly effluent limitations can require that up to 3 toxicity tests be conducted within a calendar month; planning and communication with your laboratory are critical to meet these deadlines.
  • You’ll want to have a high-quality and current Toxicity Reduction Evaluation (TRE) plan in place to address the pathway for resolving a potential exceedance of toxicity limits.
  • If the chronic Ceriodaphnia dubia is your most sensitive species, or if it becomes your most sensitive species, there are additional requirements specific to the regulation of this assay in the Provisions.

What can you do to prepare?

  • Talk to your laboratory about their performance history with your most sensitive species and how to identify if increased test replication is needed.
  • Confirm your planned testing schedule meets these new requirements.
  • Review and update your TRE plan.
  • Work with your lab or other qualified expert to review your new draft permit and provide comments to your Regional Board.

Got questions?  You’ve got experts in your corner.

Our team of expert toxicologists has been monitoring, training, and participating in the development of the Provisions for more than a decade. We also have significant applied experience conducting testing, analyzing data, and reviewing permit requirements under the framework of the Provisions. During this transition period, we can help you shorten your learning curve and minimize your risk.  For more information please reach out.

Katie Payne

Business Development Manager & Toxicology Testing Expert

Katie Payne is an environmental scientist who has a passion for applying toxicology, biology, and ecology to understand, navigate, and solve complex environmental issues.  She has more than 15 years of experience in aquatic toxicity and bioassay at Enthalpy Analytical in San Diego, California.  During her career in environmental laboratory services, she’s held positions in bench testing, project management, quality assurance, operations, and business development.  She is well versed in conducting routine and specialized freshwater, marine, and sediment toxicity tests in an accredited laboratory setting and utilizing a variety of organisms.  She shares her expertise with several collaborative working groups, including The NELAC Institute Whole Effluent Toxicity Testing Expert Committee, the Society of Environmental Toxicology and Chemistry, the California Society of Environmental Analysts, and the Professional Environmental Management Association.  Katie has a bachelor’s degree in biology and economics from the University of San Diego and a master’s degree in public health from the University of California, Los Angeles.