Specifications include, but are not limited to: The Alaska Railroad Corporation (ARRC) is planning to rehabilitate the Portage Tunnel which is located between ARRC milepost (MP) F5.8 and MP F6.8, near Portage, Alaska. Some of the issues within the tunnel can be attributed to water infiltration. During the summer months, water infiltration increases the quantity and velocity of water within the track prism causing drainage problems and track degradation within the tunnel. During the winter months the infiltration, coupled with freezing temperatures and/or freeze-thaw cycles, causes ice to build-up within the tunnel which increases the likelihood of derailing track equipment and trains, as well as incidents associated with both ice and rock fall. The existing heating system is unreliable and beyond its useful life. Both portals have manually operated doors which do not operate reliably due to age and condition. The portal structures themselves, and the majority of the existing multi-plate’s foundations, are constructed from concrete masonry unit (CMU’s). The CMU’s have deteriorated to a point where the structures are no longer serviceable, and have reached the end of their useful life. Furthermore, the railroad portals are subject to avalanche loadings at either end of the tunnel, and the north portal has some damage associated with avalanche activity. The tunnel itself does not meet current clearance design criteria, resulting in limiting some train operations. This project is intended to rehabilitate the tunnel and its applicable components as to renew this asset’s state of good repair, and result in the tunnel meeting current design criteria to assure serviceability for the next several decades, consistent with ARRC Standards.
