NV5 was retained by Placer County to prepare the construction documents for the replacement structure of the existing Lozanos Road Bridge at Auburn Ravine. The project was funded through the federal Highway Bridge Program (HBP), requiring the construction documents to be consistent with the Caltrans Bridge Design Manuals and Caltrans Highway Design Manual specifications. The documents also had to meet the permitting requirements under both NEPA and CEQA.
The original bridge was too short and too low to adequately span the channel of Auburn Ravine, causing a hydraulic constriction. It was also placed on a dangerous curve alignment with a 15 mph posted speed. To remedy this, the replacement bridge was set on a vertical and horizontal alignment, replacing the existing dangerous curve. The vertical alignment of the bridge accommodates the passing of the 100-year flood and the 50-year flood with two feet of freeboard below the proposed replacement bridge, as required by the HBP. A design speed of 35 mph specified by Placer County was used to develop the alignment. To limit the amount of right-of-way take needed and to avoid encroaching excessively into neighboring properties, a significant retaining wall was used to support the roadway approach fill.
The bridge structure itself consists of a 90-foot-long by 38-foot-wide, single-span, cast-in-place, post-tensioned concrete box girder bridge supported by concrete seat abutments. The seat abutments were founded on spread footings keyed into the rock subgrade. Due to the predominantly rural residential location of the bridge, an architectural treatment was applied to all exposed surfaces of the bridge exterior girders, bridge wing walls, and retaining walls. This architectural treatment consisted of using a concrete form liner, which gave the concrete the appearance of dry stacked rock, and staining the concrete to give it a more natural rock look. This was complemented by an open metal bridge barrier rail. In addition, in order to soften the bridge and retaining wall structures, NV5’s design incorporated native landscaping within the project limits. This landscaping also took care of some of the project mitigation requirements under CEQA and NEPA.