SR-280 Bridge Pavement and Concrete Slope Repair DO (EA 04-0V020)

Caltrans proposes repairing damaged pavement, concrete sidewalk, and concrete slope at the bridge approach and departure of Bridge #35-0008 on SR-280 in San Mateo County at post mile (PM) R1.61. The damaged was caused by erosion of the structural section supporting the infrastructure at the bridge. Google Maps indicate the damage has existed for several years which has progressively worsened due to repeated rainstorms. The issue was recently brought to Maintenance Services’ attention because of the severity of the deterioration. The Damage Assessment Team recommends urgent repairs. If left unaddressed, continued water intrusion will further displace roadway subbase material supporting the sidewalk and slope paving, leading to increased erosion, debris migration toward the highway below, and potential pavement failure. Additionally, erosion adjacent to and beneath the sidewalk poses a safety concern for pedestrian travel. Further sidewalk failure would force pedestrians off the sidewalk and onto the pavement, requiring a 6–8-inch step down, making the route inaccessible for individuals using wheelchairs or motorized scooters. The project will backfill the voids under the slope pavement at Abutments 1 and 5 with cement grout from the top and sides of the slope pavement. Imported borrow will be used to rebuild the subgrade under the sidewalk at Abutment 1. Expansion joints will be repaired and sealant applied. The failed curb, gutter, and pavement section will be replaced to keep stormwater from washing out the subsurface fill. The damaged roadway pavement will be ground and repaved. Erosion control measures will be implemented on the slope. Traffic control will be required during construction.