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Toxics TMDL for Greater Los Angeles and Long Beach Harbor Waters – Establishing Targets and Implementing Actions in a Complex Setting

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A Draft Total Maximum Daily Load (TMDL) for Toxic Pollutants in the Dominguez Channel and Greater Los Angeles (LA) and Long Beach (LB) Harbor Waters (Los Angeles, CA), expected to be completed in Fall 2010, will address impairments due to metals and organic compounds in water, sediments (toxicity and benthic community effects), and tissues (bioaccumulative effects). The current approach by the U.S. Environmental Protection Agency (USEPA) is to use standardized sediment quality benchmarks (Effects Range Low [ERL]) and water quality standards (California Toxics Rule [CTR]) as the TMDL targets. However, defaulting to the ERL and CTR values as targets leads to overly conservative values that are not consistent with other lines of evidence and furthermore are impractical. For instance, the majority of the harbor sediments are above the ERL values for the listed constituents, and yet the majority of the harbor is home to a healthy benthic community. Therefore, management of sediments based on exceedance of conservative values such as the ERL could result in the destruction of an established healthy benthic community on a harbor-wide scale.

For complex sites such as the LA and LB Harbor Waters, a one-size-fits-all approach is not appropriate: true weight-of-evidence decision making is required. In setting compliance targets and determining implementation and compliance plans, the TMDL should consider the complex nature and operational needs of the Harbor, natural and anthropogenic recovery that is occurring, other state efforts to address contaminated sediment issues, existing water resource and sediment management plans, as well as habitat restoration plans for the area beyond just contaminant source reduction and control. All of these issues must be considered and integrated into a final implementation plan to ensure that cleanup activities are effective, coordinated, and support all the beneficial uses.

Implementation and compliance planning for large, complex, and highly managed water bodies such as these Harbor Waters should include multiple lines of evidence, natural and assisted attenuation, and risk-based management approaches. The State of California has established and adopted direct-effects Sediment Quality Objectives (SQOs) that are based on a multiple line of evidence (MLOE) approach that evaluates chemistry, toxicity, and benthic community to determine a protective condition (e.g., “unimpacted” or “likely unimpacted”). Because this is a MLOE approach, conclusions do not rest on a single numeric target for sediment chemistry. In addition, because this is a highly managed system, the implementation of the TMDL should incorporate the assisted recovery occurring in the Harbor through on-going and planned dredging activities as one driving force in long-term attainment of the water quality standards. The Portsof Los Angeles (POLA) and Long Beach (POLB) (Ports) have developed a Water Resources Action Plan (WRAP) and a Sediment Management Plan (SMP) that are logical foundations for implementation and compliance plans. The WRAP and SMPs outline methods and approaches to managing water resources, contaminated site clean-ups and prioritizing dredging programs. The WRAP identifies actions the ports can implement to improve water quality through source reduction and control. The SMP uses a risk-based approach to assess chemically mediated impacts from sediments to prioritize sediment cleanup actions.
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Keywords: Sediment Management Plans; TMDL Numeric Targets

Document Type: Research Article

Publication date: 01 January 2011

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