Alternative 1 - Replace Bridge: This alternative involves removing the existing bridge and constructing a new single span prestressed concrete box girder bridge at the same location with slight revision to the horizontal and vertical alignment of bridge and bridge approach roadway. The existing sewer line can be carried across the creek inside of the new bridge. This alternative allows for an improved alignment with only minor modification to the approach roadway. A cast-in-place concrete bridge is best suited for this location with a curved alignment. For this span length, the contemporary prestressed cast-in-place concrete box girder bridge is the most economical structure type to design, construct and maintain. The substructure will likely consist of seat type concrete abutments founded on driven or drilled piles.
PDF file of Alternative 1 typical section
Alternative 2 - Replace Bridge on Changed Alignment: This alternative involves removing the existing bridge and constructing a new single span prestressed concrete box girder bridge at the same location with major changes to roadway horizontal and vertical alignment east of the bridge to connect to American River Canyon Drive at a 90º angle. The preferred structure type for this alternative is the same as Alternative 1, a prestressed cast in place box girder bridge supported on seat type abutments with piles. Advantages to this alternative include improved horizontal alignment of Orangevale Avenue and greater separation between intersections on American River Canyon Drive for Orangevale Avenue and Greenback Lane. However, due to a steep grade on American River Canyon Drive, vertical alignment of Orangevale Avenue is steeper and vertical sight distance along Orangevale Avenue at the intersection with American River Canyon Drive reduced. In addition, right-of-way needs, construction costs and environmental impacts are all greater than those for Alternative 1.
PDF file of Alternative 2 typical section
Alternative 3 - Widen Existing Bridge: This alternative involves widening the existing bridge and approach roadway. Since a widened structure will need to be more than double the existing bridge width, it cannot be completely supported on the existing concrete arch substructure. The widened structure will require the addition of a single arch on one side of, and similar to, the existing arches. The existing arches, spandrel columns, and floor beams will need to be rehabilitated to correct the current spalled condition. Both sides of the bridge will be widened and a new barrier placed on both sides. Most of the widening will occur on the same side as the added arch and a slight widening will occur on the opposite side that is supported on the existing substructure. Existing foundations will likely need to be retrofitted with pile underpinnings to arrest any ground settlement that is occurring. The primary advantage of this alternative is that you retain the existing arch appearance that is intrinsically more aesthetic than the single span concrete box girder alternatives. Because the bridge is straight, more roadway realignment is required than with Alternative 1 to safely transition traffic from the existing roadway alignment to the bridge where the centerline is shifted. This alternative will be significantly more expensive than a bridge replacement and does not allow for a curved bridge alignment that is preferred at this location.
PDF file of Alternative 3 typical section