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District to sample millions of cubic yards of dredge material; EPA/Army Corps tests planned
Summary
Sediment scientists told the board the 15% dredge design generates an estimated 5.5–6 million cubic yards of material and presented a sampling and analysis plan (55 locations, 38 spring samples, 16 geotechnical cores) with testing following Army Corps/EPA guidance; sampling is scheduled to begin in May 2025.
District consultants presented the technical approach and schedule to determine whether dredged material from the proposed wharf/deepening work is suitable for offshore disposal or beneficial reuse on beaches and nearshore areas.
Shelley Angara, a sediment scientist with Moffatt & Nichol, said the current 15% design produces an estimated 5.5–6.0 million cubic yards of dredged material. She described a sampling and analysis plan that identifies 55 sediment sampling locations across six dredge units, with 38 planned for late spring sampling and 16 geotechnical cores scheduled for summer fieldwork. The testing program is designed to follow Army Corps of Engineers and U.S. EPA guidance and will include toxicity tests, live‑organism bioassays and bioaccumulation studies to determine whether materials can be placed at the Humboldt Open Ocean Disposal site or used as beach nourishment.
Angara said much of the material is native and that the most likely portion to show contamination — if any — is a thin top layer (about the upper 5 feet) deposited during the industrial era; the vast majority of the dredge footprint is expected to be clean. The Army Corps and EPA will review the sampling and analysis plan, and Angara asked that stakeholders return final comments so the plan can be approved by the end of the month.
Board members asked about hydrodynamic effects and maintenance dredging. Angara said hydrodynamic modeling is part of the environmental evaluation and will address slope stability, anticipated maintenance dredging, and potential changes to bay hydrology.
Key technical details presented: 5.5–6.0 million cubic yards of design dredge; 55 sampling locations (38 planned in late spring, 16 geotechnical cores in summer); sampling and analysis plan to be submitted to regulators with targeted field sampling beginning May 2025; open‑ocean and beneficial use placement dependent on lab bioassays and bioaccumulation testing.
Quote: Angara told the board, "We're hoping to be starting our sampling program in May 2025."
What’s next: staff and consultants will finalize the sampling and analysis plan with regulatory and stakeholder review, submit required sampling permits and begin the field program pending approvals.
