Welcome to the Calleguas Creek Watershed

The Toxicity Work Plan

Various reaches within the Watershed appear on the California 2002 Clean Water Act Section 303(d) list of water quality limited segments as impaired due to water column and sediment toxicity, organophosphate (OP) pesticides in water, and chlorpyrifos in fish tissue. The goal of the Toxicity Work Plan is to identify the tasks required to address the beneficial use impairments caused by unidentified pollutants causing toxicity (toxicants) and the presence of OP pesticides, including chlorpyrifos.

To address the toxicity impairments, two steps are being taken. First, a monitoring program has been initiated to identify the pollutants causing toxicity in the watershed. Secondly, the toxicity will be addressed through existing or to be developed TMDLs (i.e. nutrients or historic pesticides and PCBs) or through the development of a TMDL specific to toxicity.

Responsible Agencies

The complete accounting of the responsible agencies and parties to carryout the Toxicity Work Plan has not yet been formalized, however the Agriculture Subcommittee is taking responsibility for providing policy guidance to the technical consultant. An MOU similar to the Salts Work Plan MOU will eventually be developed to formalize the funding of the Toxicity Work Plan.

Toxicity Monitoring and Pollutant Identification

Data gathered through various studies have indicated that ammonia, metabolically active organophosphate pesticides (e.g., diazinon and chlorpyrifos), non-polar organic chemicals (e.g., historic pesticides and PCBs), and volatile compounds may be causing part or all of the observed ambient water and sediment toxicity. However, additional data is necessary to determine if these pollutants are the only sources of toxicity. Accordingly, a necessary part of developing TMDLs to eliminate toxicity is to identify all of the pollutants responsible for toxicity through the development and implementation of a monitoring plan. The monitoring plan has been developed to identify the timing, extent, and magnitude of toxicity, the pollutants causing toxicity, the sources of toxicants, as well as the extent, magnitude, and sources of OP pesticides in ambient water and fish tissue.

TMDL Development

After determining the pollutant or pollutants responsible for toxicity, TMDLs will be developed for these toxicants and OP pesticides, if necessary. However, if ammonia is identified to be responsible for some or all of the toxicity, the recently developed Nutrient TMDL will likely be sufficient to address issues with toxicity. If historic pesticides and/or PCBs are identified to be responsible for some or all of the toxicity, elements of the historic pesticides and PCB TMDL will address toxicity impairments. If OP pesticides or other pollutants are responsible for some or all of the toxicity, a separate Toxicity TMDL that addresses those pollutants will be developed. Early stages of TMDL development will include the review of water quality objectives for potential toxicants to ensure they are sufficiently protective of beneficial uses.

Early Actions Items to Address Toxicity Related WQ impairments

The use of historic pesticides has been banned and certain uses of the OP pesticides, diazinon and chlorpyrifos, are being phased out. However, stocks of historic pesticides may still exist and although the uses of diazinon and chlorpyrifos are being curtailed, they are still available. As the public may not be aware of the adverse effects associated with the continued use of these pesticides, an educational program focusing on the requirements of the ban of these pesticides as well as the adverse effects associated with their continued use may be developed. In addition, a program to collect and properly dispose of the remaining historic and OP pesticides will be considered in conjunction with the education program.

Timing

The timing of the completion of the various tasks outlined in this work plan is contained in the work plan time schedule summary. The Toxicity TMDL Work Plan is to be completed by November 2005 to meet the Consent Decree deadline of March 22, 2006.

The Toxicity Work Plan

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