The Portland & Western wanted to replace four existing timber trestles, road under crossings by completely removing the trestle and filling with crushed rock. The existing trestles provided some channelizing of drainage and were replaced with new culverts. One trestle was provided with a vehicular opening for various public agencies.
The project involved surveying, creating alignments and profiles at each of the four sites as well as culvert sizing, ditching, drainage, and trestle removal plans. It was determined that complete geotechnical evaluations involving field testing was driving the cost of the design above the construction cost and it was determined that we would design for the greatest expected settlements given the local area geology. There was concern the amount of settlement would drag the existing trestle piles down during initial settlement so monitoring of the trestle settlement was incorporated into the construction package. The construction was performed without a problem resulting in total settlements in the ¼ - ½” range.