Arcata Wastewater Treatment Facility Improvements-Levee Augmentation

The City of Arcata is implementing improvements to its Wastewater Treatment Facility in Humboldt County, specifically focusing on levee augmentation to protect critical infrastructure. The project involves raising the existing levee system to a consistent height of 15 feet NAVD to provide one foot of freeboard above the base flood elevation of 14 feet. Construction will utilize unpainted corrugated steel metal sheet piles driven vertically into the soil, with reinforced concrete used in areas where utilities prevent sheet pile installation. Additionally, engineered fill with light-rock facing will be placed where no environmentally sensitive habitat area is present, and a storm gate system will be installed at the existing entrance to maintain traffic flow. The project is governed by FEMA standards for the VE zone and Flood Design Class 4 requirements, ensuring new essential facilities are protected to the base flood elevation of 10.0 feet NAVD 88 plus 2.0 feet. All work must conform to the current California Building Code. Environmental compliance is managed through a Notice of Determination and an addendum to the Initial Study/Mitigated Negative Declaration, which confirms no new significant environmental impacts and includes updated mitigation measures for the northwestern pond turtle. Compliance will be verified through visual inspections, photo documentation, construction inspector notes, and QSP reports. The project is managed by the City Engineer and the Community Development Director.