Cienega Road Bridge Replacement Project

Cienega Road Bridge Replacement Project

The San Benito County Department of Public Works proposes to replace the Cienega Road Bridge at Pescadero Creek. The project objective is to improve the operation of the existing functionally obsolete and structurally deficient single-lane bridge. The existing bridge is constructed of steel channel girders and is 4.5 meters (m)/ 14.8 feet (ft) wide and 6.7 m (22 ft) long. The abutments consist of steel piles supporting a steel cap. The piles also hold back steel cattle guard panels, which are used to retain the approach fills. The proposed project consists of replacing the existing bridge with a cast-in-place reinforced concrete slab bridge. The new bridge will be 10.0 m (32.83 ft) wide and 25.3 m (83 ft) long, with two 3.66 m (12 ft) lanes and 0.9 m (3 ft) shoulders. Concrete bridge railings will be attached directly to the bridge deck. The proposed bridge will be a two-span structure with a pier near the middle of the creek. The bridge will be supported on cast-in-steel-shell (CISS) concrete piles with concrete pile extensions at the bents, and driven steel HP piles at the abutment supports. The 610 millimeter (mm)/24 inch (in) diameter CISS concrete piles will have 400 mm (16 in) diameter pile extensions above the CISS cutoff elevation, which will be approximately 1 m (3 ft) below the creek bottom. The abutments will consist of fixed end diaphragm type abutments supported on a single row of steel H piles. The proposed roadway alignment closely matches the existing alignment. The proposed bridge will be slightly more than twice as wide as the existing bridge. The proposed roadway centerline will be just downstream (east) of the existing bridge deck, so that the proposed southbound lane covers the existing bridge footprint. The north roadway approach will be approximately 113.5 m (372 ft) long while the south approach will be approximately 107.7 m (353 ft) long. The roadway approach fills along the proposed roadway alignment will remain within the proposed 18.3 m (60 ft) right-of-way limits except for in a few areas near the creek. The County intends to acquire permanent maintenance easements for these small areas. The permanent easements will extend approximately 1.5 m (5 ft) beyond the toe of fill lines, where they are outside the proposed right-of-way. The largest fill area beyond the proposed right-of-way limit occurs just northwest of the bridge.

Hollister

San Benito