Elk River Waste Water Treatment Plant Outfall Repair

The Elk River Waste Water Treatment Plant Outfall Repair project, identified by solicitation number ED-25-12, involves critical maintenance and structural repairs to the outfall pipe diffuser section located in Humboldt Bay. Managed by the City of Eureka, the project focuses on replacing 90 existing neoprene flap-style check valves with 3-inch elastomeric Tideflex check valves to prevent sand, sediment, and shell from entering the diffuser pipe. Additional scope includes the removal of accumulated sediment within the pipe, the replacement of one nut and restraining bolt on the diffuser, and the repair of a 6-inch-wide area of spalling using underwater concrete epoxy. The work will be performed at a depth of 10 to 25 feet below Mean Lower Low Water Level along the 360-foot diffuser section nearest the terminus. All construction activities are strictly regulated to minimize environmental impact and must be conducted by divers using hand tools only. The use of heavy construction equipment, pile driving, dredging, or mechanized excavation is explicitly prohibited. The project is scheduled for execution during the Summer-Fall 2026 window and must be timed to avoid periods of anadromous fish passage and heavy waterfowl use in the bay. This project has received a California Environmental Quality Act Notice of Exemption, as it is classified as routine maintenance that does not involve an expansion of use and is not expected to result in significant environmental impacts.