Gordon Slough Repairs are Done!
Repair work on Gordon Slough near the entrance to the Cache Creek Nature Preserve was finally finished on October 20, 2023.
The slough sustained erosion and slumping damage during the 2019 floods, a natural disaster declared by both the governor and the president. The project was originally scheduled to be done in 2020, but was delayed by the COVID shutdowns. In 2022, the shortage of contractors required the project be delayed to 2023.
Back in March, 2023, we sent out a request for bids.
The project was funded by the Federal Emergency Management Agency (FEMA) and Glissman Excavating, of Loomis, CA, was selected in a public bid process.
The construction project itself lasted approximately three weeks, and ended on time and on budget.
The damage was along the Salisbury Spillway channel and north levee. An estimated loss of 1,456 cubic yards of soil occurred over approximately 60 linear feet, 131 feet wide, and 5 feet high (approximately 7,500 square feet or 0.17 acres).
Glissman Excavating installed 735 cubic yards of compacted soil within the spillway channel and levee slope and installed 1,260 tons of 18-inch facing stones, 1,140 tons of half-ton rip-rap, 2,600 tons of quarter-ton riprap.
Equipment used included dump trucks, semis, two excavators, bulldozer, front-end loader, water truck, finish grader/tractor, and hydroseeding equipment.
Environmental Monitoring and Mitigation
The project requirements included biological services consisting of monitoring, mitigation measures, and reporting.
Federal and state wildlife agencies were consulted and a qualified biologist monitored the site daily. The Gordon Slough is considered habitat for four endangered or threatened species
- Giant garter snake,
- California red-legged frog,
- California tiger salamander,
- and Valley elderberry longhorn beetle (VELB).
None of the species were found before, during, or after the project completion, however.
The work included removing some overgrown invasive vegetation within the Salisbury Spillway channel to improve conveyance. The contractor also removed some non-native vegetation and trees in the project area. No elderberry shrubs were disturbed by this project.
They also planted willows as natural erosion control as mitigation against future flooding.
The Conservancy hopes to obtain additional funding to remove invasive blackberry and other invasive plants within the slough within the next five years.