Success Stories
Program monitoring and assessment helps improve water quality.
Pesticide Toxicity
Summary: Monitoring and assessment showed that two common pesticides, diazinon and chlorpyrifos, were causing toxicity in urban creeks. CCCWP partnered with municipal programs statewide to share that information with state pesticide and water quality regulators. The resulting toxicity problem went away. Currently, CCCWP monitors pyrethroids, which replaced diazinon and chlorpyrifos uses, and shares the information with a similar goal of helping state pesticide regulators implement policies to control pollutants of concern. The sequence of regulatory communications and scientific studies below shows how CCCWP identifies and helps correct water quality problems caused by legal pesticide uses.
Key documents:
- Letter to the Regional Water Quality Control Board Documenting Attainment of the Diazinon and Chlorpyrifos TMDl (PDF)
- "Attaining the TMDL" means that Diazinon and Chlorpyrifos no longer appear to cause toxicity in Conta Costa County's creeks.
- As the letter explains, the disappearance of historically observed toxic effects from those two pesticides is believed to result from restrictions on use that were implemented by pesticide regulatory agencies in response to stormwater monitoring study findings.
- Pyrethroids Stressor-Source Identification Report
- Part A presents evidence from monitoring potentially linking toxic effects observed in Contra Costa County's creeks to pyrethroid pesticides (PDF).
- The measured pyrethroids concentrations are high enough to cause the observed toxic effects, based on their known toxic potencies.
- When a substance that makes pyrthroid more toxic (a "synergist") was added sample toxicity increased.
- When a substance that makes pyrethroids less toxic (an "antagonist") was added sample toxicity decreased.
- Part B presents evidence from research on pesticide usage in Contra Costa County showing that allowed uses of pyrethroids (PDF) implicated in Part A have increased.
- Part A presents evidence from monitoring potentially linking toxic effects observed in Contra Costa County's creeks to pyrethroid pesticides (PDF).
- Letter to the Regional Water Quality Control Board Documenting Implementation of a Pyrethroid Control Program (PDF)
- Letter from the Regional Water Quality Control Board approving CCCWP's Pyrethroid Control Program (PDF)
Mysterious Fish Mortality
Summary: For many years, going back to 2005, fish mortality was observed from time to time in Marsh Creek, in Eastern Contra Costa County. The exact cause could not be pinpointed, until in 2018 CCCWP executed a monitoring program using technology to continuously record and report key water quality metrics, such as dissolved oxygen, temperature, and water clarity. The project identified low dissolved oxygen as a likely cause, and pilot tested a potential creek flow augmentation remedy in partnership with the City of Brentwood Wastewater treatment plant and the Contra Costa County Flood Control and Water Conservation District.
Key Documents: