Alternative 1 - Widen upstream: The existing sidewalk and concrete barrier on the upstream side of the bridge will be removed and replaced. A third reinforced concrete arch will be constructed similar to the existing arches. In addition, the scenic overlook area to the south of the bridge will require modification.
PDF file of Alternative 1 typical section
Alternative 2 - Widen downstream: Bridge removal would include the existing railing and barrier on the downstream side. A third concrete arch will be constructed on the downstream side as well. This alternative is the least expensive and requires the least modification of existing adjacent facilities.
PDF file of Alternative 2 typical section
Alternative 3 - Widen Both Sides: Add Two Arches. This Alternative would widen on both sides of the existing Rainbow Bridge, 7'-9" on the upstream side and 9'-3" on the downstream side. Two stages of construction will be used to maintain two lanes of traffic during construction. The existing sidewalk will be removed and replaced in the first stage and the downstream concrete barrier in the second stage. This Alternative would construct two additional reinforced concrete arches, one under each section of widened bridge, to bring the total number of arches to four.
PDF file of Alternative 3 typical section
Alternative 4 - Widen Both Sides: Strengthen Existing Arches. For this Alternative the deck would be widened in the same way as Alternative 3 in order to maintain two lanes of traffic during construction. This Alternative differs from Alternative 3 in that the two existing arches would be strengthened instead of adding any new arches.
PDF file of Alternative 4 typical section
Bridge Width: The existing clear traffic width is 25'. The minimum AASHTO standard is 40', consisting of two 12 ' lanes and 8' shoulders. A 5' sidewalk and two 18" railings increase the deck width to 48'. The railings put in place in all four alternatives would be historic replicas of the original railing.
Historic Railing: The existing railing was placed with the widening in 1969. A replica of the historic railing will be constructed for the selected Alternative.