Pipe Ramming Under Three Active Railroad Lines in Difficult Soil Conditions
Pipe ramming was chosen as the preferred method for installing a very shallow utility crossing beneath the three active BNSF Railway (BNSF) mainline railroads in Skykomish, Washington. The soil conditions in the area of the crossing are highly variable and consist primarily of gravel, cobbles, and boulders. Several trenchless options were considered before pipe ramming was selected as the most feasible. The crossing was constructed in the summer of 2008. A settlement and/or heaving monitoring program was required by BNSF. This program was designed by Jacobs Associates, and it was implemented and monitored by the contractor with the data submitted to the designer for review on a daily basis. This paper reviews the options considered for the utility crossing, the reasons for the feasibility determination, the design considerations and limitations, construction observations (including the results of the monitoring program), and the lessons learned on this project.