GPI’s team interfaced with the design team on this landmark City of Pasco project to fulfill the project geotechnical requirements. A new railroad overpass bridge will replace the aging and narrow tunnel below this major rail thoroughfare. LRFD design for deep and intermediate foundations was evaluated and pavement section design analyses validated City standards for the traffic loading. Through revised loading and proactive design approach, we were able to rely on conventional foundations with rigid, geogrid-reinforced soil improvements.

In addition, we worked closely with J-U-B’s design team on methods to design a backfill approach for the existing tunnel underpass using recycled materials from construction. For project economy, portions of the backfill will utilize site demolition materials with cement stabilization up to the tunnel’s top 10 feet. To maintain settlement criteria on the adjacent abutments that supported 4 primary BNSF tracks, geofoam was selected for the final tunnel backfill. The project has been funded by WSDOT to initiate construction in 2020.