Georgiana Slough Erosion Control and Habitat Enhancement Project

The Georgiana Slough Erosion Control and Habitat Enhancement Project, managed by the Brannan-Andrus Levee Maintenance District in Isleton, California, focuses on constructing erosion control methods along the right bank levee of Georgiana Slough on Lower Andrus Island. The scope of work includes the placement of quarry stone riprap at the levee toe to create a foundation for a hat bench, addressing upper slope erosion and lower slope undercutting. The project involves four primary phases: mobilization, site preparation, levee slope and bench construction, and site demobilization. Technical specifications require the use of a barge-mounted long-reach excavator for overburden removal, the placement of dried and disced spoils on the landslide slope compacted to at least 90 percent per ASTM D1557-91, and the import of engineered fill to raise the levee crown to an elevation of +13.5 NAVD88, capped with class II aggregate base material for an all-weather roadway. The project is governed by an Initial Study and Mitigated Negative Declaration, with a June 2025 addendum addressing modifications to construction sequencing, material sourcing, and increased hauling trips. Environmental assessments confirm that these modifications do not create new significant effects. The construction schedule is set to begin on June 15, 2025, with mobilization occurring through June 18, site preparation through July 5, waterside slope grading and fill placement from July 6 to August 16, plant installation from September 7 to October 29, and final demobilization concluding by November 1, 2025. The project is categorized under NAICS code 237990.