SR-128 Pavement Settlement and Drainage Repair DO (EA 04-0V830)

The California Department of Transportation (Caltrans) proposes repairing pavement settlement and drainage failures at post mile (PM) 16.07 and 16.16 on State Route (SR-) 128 in Sonoma County, south of Maacama Creek Bridge near Calistoga. At PM 16.07 the drainage system will be repaired by replacing the westbound DI with a GT4 DI and the eastbound DI with a G2 DI. A short reach of 24-inch corrugated steel pipe (CSP) culvert with a TEE dissipator will be constructed to discharge runoff onto the existing rock slope protection (RSP) pad. The alignment of the drainage culverts will remain unchanged. Loose material, debris, and vegetation on the failed slope will be removed. A soldier pile wall with concrete lagging will be constructed to prevent further progression of the slipout. The proposed wall is estimated to be approximately 80 feet long and will retain a maximum height of 10 feet. The embankment will be reconstructed and permanent erosion control installed. The roadway and structure will be excavated and reconstructed. The roadway will be repaved and any striping/pavement delineation replaced. At PM 16.16 The existing undermined section below the concrete pad will be repaired using cement slurry to backfill the cavity. Loose debris within the washout area will be removed and the slope will be excavated an additional one foot below the failure plane boundaries. RSP fabric Class 8 will be placed over the excavated areas in conformance with Standard Specification Section 72-2.02C. Class VI 3/8-ton RSP (Type A Placement) will then be placed over the RSP fabric. Rock voids will be filled with excavated material per District Landscape Architect recommendations. A 3-point bearing for rocks must be achieved. The top of the RSP will be filled with shotcrete for a 4-inch shotcrete layer. Shotcrete must be added one inch at a time.