Fright at the end of the tunnel

The stream has built up this plug of rock and debris at the upstream end of the tunnel. At the base of the debris pile is a pool about four feet deep and 10 feet wide. On this particular hike, we were able to ckimb up the logs while leaning against the wall to get over the pool. Without the logs, we would have gotten wet since the foundations of the concrete walls have been undercut and there was no way to cross the pool. On another hike, we had to retreat and go up and over the railroad fill.