Since 2017, we have represented the San Diego Unified Port District (District) on sediment investigations near the Tenth Avenue Marine Terminal (TAMT) in San Diego Bay. This work was previously performed by Windward Environmental LLC, which is now part of Barr.
The California Regional Water Quality Control Board has issued two Investigative Orders (IOs) to the District and City of San Diego (City) related to the TAMT. The first IO (R9-2017-0081) required the District and the City to establish the nature and extent of sediment contamination, its potential sources, and contaminant transport and pathways. The second IO (No. R9-2022-040) required the District and the City to determine if sediments within and adjacent to the TAMT meet narrative sediment quality objectives (SQOs) that protect beneficial uses, including those associated with aquatic life, benthic communities, human health, wildlife, and resident fish.
The District and City of San Diego collaborated to address both IOs. On behalf of the District, we supported the development of focused sampling plans and collected sediment trap, surface sediment, sediment core, biota, and water samples to answer study questions presented in the IOs. We then contributed to the in-water sediment evaluation for the Sediment Chemistry Assessment Report, completed in 2020, to address the first IO. Our sediment trap sampling and analysis were critical to understanding sediment sources and transport pathways at the TAMT. Also in 2020, we completed a supplementary study to evaluate sediment trap chemistry throughout San Diego Bay, providing deeper insight into sediment sources and transport.
To address the second IO, we led a collaborative team in developing the Sediment Quality Objectives Assessment Report, which was completed in March 2025. As part of this effort, we conducted a sediment quality evaluation, an ecological risk assessment, and a human health risk assessment. We were the primary author of a memorandum summarizing the development of toxicity reference values for the ecological risk assessment. To support the human health risk assessment, we developed a calibrated food web model (FWM) for San Diego Bay and applied it to the TAMT, which helped our team assess potential human health risks and understand how sediment contamination might impact the local food chain.
Our recommendations in the Sediment Quality Objectives Assessment Report were to refine the focus areas for evaluating the benthic communities and human health SQOs, delineate contamination hotspots that could impact human health, and further characterize resuspended sediment to assess recontamination potential before any potential future actions at the TAMT.
