Home  •   Field Guide  •   Forums  •    Unread Posts  •   Maps  •   Find a Hike!
| Page | Discussion | View source | History | Print Friendly and PDF

Twin Tunnels Catchment Structure

From Oregon Hikers Field Guide

The west end of the Mosier Tunnel Catchment Structure (Steve Hart)


In 1995, when the decision was made to reopen the Mosier Twin Tunnels for tourist use, there was immediately a question of safety. The area was always prone to rockfalls, but times have changed since the highway was built in the 1920s. If the state was going to bring the public into a rockfall zone in the 1990s, they had to be able to guarantee their safety to a level unknown in 1921.

The tunnels could be shored up with a new lining, but about 700 feet of trail just west of the tunnels was still going to be dangerous. In places, in the 40 odd years since the highway had been closed, over 15 feet of rock rubble had fallen from the cliffs to the road. The first thought was to build a shed that would force the rocks farther over the side. Unfortunately, there's a railroad immediately under the trail and the Union Pacific wasn't big on the idea of catching rocks.

The solution was to build the catchment structure shown here. The catchment structure is designed to catch rocks, rather than letting them hit the trail or bounce over the side. Above the roof slabs is a level of foam and pea gravel. The structure was designed to handle a rock that weighed 5,000 pounds falling 200 feet. The structure was tinted dark on purpose to help blend in to the rock visually.


Oregon Hikers Field Guide is built as a collaborative effort by its user community. While we make every effort to fact-check, information found here should be considered anecdotal. You should cross-check against other references before planning a hike. Trail routing and conditions are subject to change. Please contact us if you notice errors on this page.

Hiking is a potentially risky activity, and the entire risk for users of this field guide is assumed by the user, and in no event shall Trailkeepers of Oregon be liable for any injury or damages suffered as a result of relying on content in this field guide. All content posted on the field guide becomes the property of Trailkeepers of Oregon, and may not be used without permission.