Seafloor Mounds Peer Review

The California State Lands Commission (the Commission) administers leases related to oil and gas operations located in and adjacent to the state’s waterways, beaches, and coastline. When four oil and gas platforms (“4H Platforms”) were decommissioned and removed from the Santa Barbara Channel in the mid-1990s, each left behind a mound of byproducts from drilling operations which over time became covered with sediment and shells. The Commission is in the process of determining whether Chevron, the lease holder, has met the lease obligations, which include a proposal to keep the 4H shell mounds in place in their current configuration, unless otherwise specified. To inform its decision, the Commission produced a draft report entitled “Review of Lease Obligations and Assessment of Impacts to Public Trust Resources and Values: State Oil and Gas Leases PRC 1824 and PRC 3150 Terminations and 4H Shell Mounds Disposition” summarizing impacts to public trust resources that could occur if the mounds are left in place. The Commission partnered with Ocean Science Trust (OST) to lead a peer review process that assessed the scientific merits of the report to ensure that ensuing decision are guided by sound science.

To meet the Commission’s needs, OST implemented a scientific review process that promoted objectivity, transparency, candor, efficiency and scientific rigor. OST assembled a multidisciplinary four-member review committee representing diverse expertise in oceanography, marine toxicology, ecology and seismic activity. The review committee was asked to conduct independent assessments of whether:

1. the scientific information presented within the report is sound and reasonable,
2. the relevant science included in the report is comprehensive and representative of existing knowledge in this field of research; and,
3. interpretations and conclusions drawn in the report are appropriate given the available scientific information.

This peer review took place in Fall 2022. Feedback indicated that the reviewers were overall satisfied with the scientific rigor of the draft report. However, reviewers across the board did recommend further assessment of the various ways in which leaving the shell mounds intact or removing them could threaten public trust resources. The reviewers’ feedback was primarily focused on recommendations for additional studies, such as an assessment of contaminant bioaccumulation in surrounding biota, rather than on recommendations for inclusion of additional readily-available scientific information. In response, the Commission conducted an additional study in 2023 assessing bioaccumulation to determine whether metals and other contaminants may be leaching from the mounds into surrounding waters. This follow-up study did not find evidence of increased contaminant levels in the tissues of mussels recovered from the shell mounds when compared to mussel tissues in reference sites. The Commission was able to update the report to incorporate reviewer feedback and reflect findings from these additional studies to ensure that the report reflects scientific objectivity and rigor. The final report is available on the Commission’s website as of March 2025. Please see the Peer Review Summary linked on this website for a complete summary of reviewer feedback.

• Dr. Tom Connolly, Physical Oceanographer, Moss Landing Marine Laboratories at San Jose State University
• Dr. Eunha Hoh, Professor of Environmental Health, School of Public Health at San Diego State University
• Dr. Samuel Y Johnson, Emeritus Research Geologist & Independent Consultant, United States Geological Survey
• Dr. Milton Love, Research Biologist, Marine Science Institute at University of California Santa Barbara