Coos Bay Rail Line Tunnel

There are nine tunnels on the rail line between Eugene and Coos Bay, Oregon, originally built between 1911 and 1916. These tunnels are lined with timber, shotcrete, or gunite over steel sets. Because of the weathered rock of the Coast Range mountains, the harsh climate near the Pacific Coast, and lack of maintenance, the timber-lined portions of the tunnels fell into disrepair, causing the line to shut down in 2007. In 2009, the Oregon International Port of Coos Bay (OIPCB) received $2.5 million in ARRA stimulus funds to repair the tunnels as a first step in reopening the line.

Jacobs Associates has been working with HDR in Portland to evaluate and prioritize the work needed along the entire line to get the railway functioning again. The principal objective is to repair specific sections of four railway tunnels. We prepared the project design calculations, drawings, and specifications, and facilitated the bid process for OIPCB. Construction started in September 2009, with Jacobs Associates providing the resident engineer for construction monitoring.

The tunnels are located in weathered sandstone and colluvium, and some had experienced localized collapses in recent years. To prevent further collapse during the repair process, we recommended two methods of timber set replacement: placement of steel jump sets for ground support prior to timber set removal; and presupport with steel channel spiling immediately ahead of timber set removal and replacement with steel sets. Both methods are proving successful.