Design Chosen For New Waiaka Bridge Below Waimea

It’s got an off-camber “S” curve, and also involves a busy intersection.

What less could one want in a bridge?

How about a National Bridge Inventory Standard rating of 26 out of a possible 100, where 100 signifies a bridge meeting current engineering design standards?

All of the above describe the Waiaka Bridge below Waimea, where Kawaihae Road meets Kohala Mountain Road.

The state Department of Transportation is proposing to replace the 80-year-old structure with a new bridge complete with a traffic signal. It will also have reconfigured approaches for smooth transitions to the two roads involved.

According to a final environmental assessment issued this month, the Waiaka Bridge is “structurally deficient” and in such poor shape that it qualifies for federal funds for its replacement.

The current problems with the bridge are many, according to the EA, and include obstructed views due to its alignment and a wooden walkway attached to the bridge. It also has a center supporting pillar which collects debris that can obstruct Keaniuomano Stream, sending water spilling onto the bridge during heavy storms.

The design for the new Waiaka Bridge and its approaches are shown in dark grey, with the Kohala Mountain Road coming down from the top. Blue signifies the temporary bridge and roadway, while the colored areas at the bottom show private land to be acquired (click to enlarge). EA image.

Replacing the bridge will require construction of a temporary bypass bridge and roadway.

There were five alternative designs considered for the new bridge; the one chosen will relocate the bridge to the south and require acquisition of about 10,000 square feet of private property. The realignment of the Kawaihae Road will also remove the “S” curve.

According to the EA, the cost of the project will be about $12 million. Construction is expected to begin in 2015 and take about a year to complete.