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Application of California Sediment Quality Objectives at Small Sites: Challenges and Potential Modifications
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Background/Objectives.

The State of California adopted a Water Quality Control Plan for Bays in Estuaries in California (Plan)in 2018 that included Sediment Quality Provisions. These provisions describe narrative sediment quality objectives (SQOs) and methods for the assessment of SQOs for benthic communities, human fish consumers, and wildlife seafood consumers in enclosed marine bays and estuaries. Some Regional Boards in California are requiring all three SQO assessments (i.e., to assess benthic community, human health, and wildlife protection, separately) at sediment sites of all sizes despite the recommendations of the Plan, which specifies a minimum site area of 1 km2 because "uptake from foraging activities outside of the site is not specifically considered". While comprehensive in nature, the SQO assessment methods were developed for assessment of larger exposure areas and when applied to small sites (<1 km2), the risks and areas requiring potential actions are over-estimated and uncertain, particularly for sites with PCBs.

Approach/Activities.

This review evaluates small site benthic SQO data (i.e., chemistry, toxicity, and benthic community LOEs) from previously completed assessments and uses sediment and relevant tissue chemistry data available in the State Water Board's database (CEDEN) to conduct separate human health SQO and wildlife SQO assessments at small sites. The benthic SQO assessments were conducted at these sites in accordance with the State Plan's pre-established lines of evidence and categories of impairment ranging from unimpacted to impacted. We performed human health SQO assessments using the State's Decision Support Tool to evaluate human "chemical exposure" (i.e., risks from consumption of fish collected in or adjacent to the small sites) along with an evaluation of the degree of sediment linkage; PCBs were the focus of this evaluation. For wildlife, the guidance is not specific; thus tissue PCB data from potential prey of relevant avian receptors were screened using protective tissue screening levels established by Fish and Wildlife Service (Southern California office). Challenges associated with the three SQO assessments at small sites are considered along with modifications to the methods and overall SQO approach that could improve these assessments at small sites.

Results/Lessons Learned.

The Plan's assessment methods allow for the collection of valuable data but show limitations particularly at small sites with detectable sediment PCBs. On a station-by-station basis, the benthic SQO assessment is reasonable to implement at small sites to understand baseline conditions; however, unless toxicity is significant, there isn't a clear path forward for the benthic SQO, especially for sites where natural physical conditions affect the localized benthic community. Alternative approaches will be suggested in which bioavailability of constituents is evaluated and/or toxicity data supersedes other LOEs. Results of the human health SQO and wildlife SQO assessments at the small sites, show a high degree of uncertainty due to the disconnect between the site size and fish foraging/home ranges. We will illustrate reasonable modifications to these SQO assessments including evaluating human and wildlife chemical exposure and sediment concentrations within larger exposure areas. We also will discuss a workflow process for a more integrated SQO assessment program, that incorporates potential off-ramps and allows more flexibility for stakeholders/PLPs that are required to implement SQO methods at small sites.

Publication Summary

  • Geosyntec Authors: Wendy R. Hovel, Brian Hitchens
  • All Authors: Wendy R. Hovel (Geosyntec, San Diego, CA, USA), Brian Hitchens (Geosyntec, San Diego, CA, USA)
  • Title: 2023 Battelle Sediments Conference
  • Event or Publication: Event
  • Practice Areas: Sediment assessment and remediation, Contaminated site assessment and clean up
  • Citation: Battelle's International Conference on the Remediation and Management of Contaminated Sediments at the JW Marriott in Austin, Texas, on January 9 through 12, 2023
  • Date: January 9 through 12, 2023
  • Location: JW Marriott in Austin, Texas
  • Publication Type: Platform Presentation