Support for TMDL Development Service
Section 303(d) of the federal Clean Water Act requires states to identify those water bodies not attaining water quality standards (i.e., waters whose beneficial uses have been impaired), to identify the pollutant causing the impairment, and to develop remediation plans (known as “total maximum daily loads”, or TMDLs) for each pollutant in each water body that will reduce and eventually eliminate the impairment and restore the beneficial use(s). A TMDL is multi-stage process that ultimately leads to a determination of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutant`s sources.
As experts on the fate and effects of contaminants in aquatic systems, Pacific EcoRisk can provide a wide variety of support services for the TMDL process, ranging from a critical evaluation of technical aspects of existing or proposed TMDLs to review of existing scientific information and/or performance of scientific studies to assist in the preparation of appropriate and technically-supported TMDLs.
Services that we provide in the support of TMDL development include:
- Preparation of information (e.g., literature) reviews,
- Collection and analyses of water, sediment, and/or biota samples,
- Performance of toxicity and/or bioaccumulation testing.
- Evaluation of biological communities
Performance of a Critical Review of a Proposed TMDL for PCBs
Pacific EcoRisk served as the lead organization and acted as chair of an expert work panel performing a critical review of a Draft TMDL for PCBs in San Francisco Bay for the maritime industry. This review effort identified several technical issues with key elements of the Draft TMDL that ultimately led to significant revisions of the TMDL.
Development of a Conceptual Model and Impairment Assessment for Diazinon in San Francisco Bay
As part of an effort by a multi-stakeholder group charged with assisting state regulatory agencies in the preparation of a TMDL for diazinon, Pacific EcoRisk performed a review of available scientific information and authored a conceptual model and impairment assessment of diazinon in San Francisco Bay; based upon the current and projected absence of any diazinon-related toxicity in the Bay’s ambient waters, this report concluded that there was no impairment of the Bay’s beneficial uses. Based upon these findings, the state regulatory agencies are currently considering ‘de-listing diazinon’ (i.e., removing diazinon in San Francisco from the 303(d) list).
Development of a Conceptual Model and Impairment Assessment for Selenium in San Francisco Bay
As part of an effort by a multi-stakeholder group charged with assisting state regulatory agencies in the preparation of a TMDL for selenium, Pacific EcoRisk performed a review of available scientific information and authored a conceptual model and impairment assessment of selenium in San Francisco Bay. As a result of this effort, Pacific EcoRisk is currently co-leading an effort to develop a Water Quality Attainment Strategy for selenium to facilitate compliance with the Bay’s beneficial uses.