The State of California Approves Toxicity Provisions and the Test of Significant Toxicity (TST)

December 3, 2020

By: Adrienne Cibor

On December 1, 2020, the State Water Resources Control (State Board) approved the California Statewide Toxicity Provisions. The toxicity provisions include a statewide standardization for how toxicity testing is measured and reported for National Pollutant Discharge Elimination System (NPDES) compliance purposes. Toxicity testing is one of the three main tools used by the USEPA to achieve the objective of “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” stated in the Clean Water Act. To learn more about the background leading up to the approval, check out our previous blog post here.

New Guidance

As the Provisions are incorporated into new and existing NPDES permits, it is important for dischargers to understand how they can affect not only the toxicity test analyses, but also the frequency of testing, species sensitivity screening, and actions needed when limits are exceeded.

Another key change to note is how toxicity results will be handled under the new provisions. Toxicity test data will be analyzed with one single statistical test, the Test of Significant Toxicity (TST), for the purpose of determining permit compliance.

The incorporation of the TST is meant to simplify and standardize the answer to a toxicity test – whether or not a discharge from a water treatment plant going into the receiving environment is toxic to the organisms living in the environment.

Future Impacts

Currently these California provisions are only applicable for discharges to inland surface waters, enclosed bays, and estuaries. However, it is expected that similar provisions will be expanded to ocean discharges, groundwater, and stormwater runoff in the future.

Please note, The TST also has implications outside of California, as it is a USEPA method for determining test outcomes and has already been incorporated in permits outside of California.

For More Information

To learn more about what toxicity testing is, check out Enthalpy’s previous blog post on Toxicity Testing 101.

Need help determining the impact of these provisions and the TST on your business? Want to consult with our experts to plan for future compliance in your testing needs? Feel free to start a conversation with myself and our fellow experts at Enthalpy Analytical.

Adrienne Cibor
Senior Project Manager / Environmental Scientist
Adrienne Cibor is the Senior Project Manager in Enthalpy’s San Diego Environmental Toxicology lab. She leads a team of project managers and has over 18 years of experience in aquatic and sediment toxicology, regulatory affairs, risk assessment, and toxicity investigations. Adrienne is an enthusiastic community and environmental services professional with a Bachelor of Science focused in Marine Biology from San Diego State University.

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