The Marin Municipal Water District (Marin Water) in California is assessing a plan to remove about 50,000 cubic yards (38,000 cubic metres) of sediment and plant growth from Nicasio and Halleck Creeks to reduce flood risk around the community of Nicasio.
The work, planned across at least two construction seasons, would cover approximately 3,150 linear feet (2,410 metres) of Upper Nicasio Creek and 1,200 linear feet (920 metres) of Halleck Creek, which converge behind Nicasio School.
The proposal also calls for lowering the sediment delta in Nicasio Reservoir by about four feet (1.2 metres). It would create a bench around 100 feet (30 metres) wide along 2,000 feet (600 metres) of the creek's right bank.
Maintenance removal of up to 10,000 cubic yards (7,600 cubic metres) would follow every five to 10 years as needed.
Removal depths would range from about two feet (0.6 metres) near the reservoir to as much as six feet (1.8 metres) nearer town, with the channel widened in some areas.
Marin Water has folded the plan into the environmental impact report (EIR) for its Atmospheric river capture project, which is a 13.2-mile (21.2-kilometre) pipeline linking the North Marin Aqueduct to Nicasio Reservoir to hold excess winter water from the Russian River.
Comments on the scope of the EIR are due by noon on October 19. Excavation is unlikely before next year's rains. Current planning assumes construction could start in summer 2027 if permits are obtained early that year.
Nicasio Reservoir was built in 1961. The creek bed near Ranch Road now sits about seven feet (two metres) higher than in 1960, and sediment has built up six or seven feet deep in places since regular district maintenance ended in 1998.
