Storm Damage Repair of Buckeye Canyon Road {Sites 5 and 6) within the Los Vaqueros (LV) Watershed - FEMA 4683

Storm Damage Repair of Buckeye Canyon Road {Sites 5 and 6) within the Los Vaqueros (LV) Watershed - FEMA 4683

CCWD proposes to perform storm damage repairs of Buckeye Canyon Road, a gravel access road, at two sites (damage Sites 5 and 6) which were damaged by the storm events of January 2023. At these two sites, heavy storm flows resulted in significant erosion of the embankment downslope of the road. Portions of the gravel road adjacent to the downslope embankment also eroded. Buckeye Canyon Road is an important access road utilized by both CCWD staff and easement holders and remains at risk of further degradation or collapse during future storm events. The proposed improvements at the two damage sites are described below. Damage Site 5 – This damage site is located towards the southern end of Buckeye Canyon Road. Storm flows resulted in erosion of the road’s downslope embankment. CCWD plans to excavate loose soils and stabilize the embankment by placing rip rap. A geotextile fabric will first be placed underneath the riprap. The total extent of rip rap along the roadway edge would be approximately 134 feet long by 30 feet wide, or 4,020 square feet. Portions of the rip rap furthest downslope will be backfilled with a layer of soil (approximately 2,860 square feet of riprap wil be exposed). The estimated depth of disturbance will be 3 feet when excavating to bench in the riprap. Damage Site 6 – This damage site is located towards the northern end of Buckeye Canyon Road. Storm flows eroded both the steep roadway embankment and portions of the roadway edge. CCWD plans to stabilize both the roadway and embankment by constructing a soldier pile retaining wall along the northbound (NB) direction of the road. The wall will be placed approximately 5 feet away from the edge of the road and will run approximately 75 feet in length alongside the road. The maximum estimated depth of disturbance will be 32 feet when drilling for the wall’s soldier piles. After holes are pre-drilled into the soil, steel I-beam piles will be inserted and concrete casings will be poured. Next, pre-cast concrete lagging will be placed between the I-beams. The concrete lagging will be placed about 3 feet below grade with 10 feet exposed height, for a total lagging height of 13 feet. The area between the wall and edge of road will be backfilled with engineered fill and a Midwest guardrail system will be constructed. A concrete gutter will also be placed inbetween the guardrail posts and retaining wall. The gutter will direct flows to a drop inlet that will empty into a new 8-inch storm drain running approximately 32 feet down the embankment. This drop inlet system will direct future storm flows away from the embankment behind the retaining wall to avoid erosion.

Contra Costa

Unincorporated

Contra Costa