The interesting thing about this tunnel is that it was originally built for the narrow gauge Ilwaco Railway and Navigation Co. railroad. After that worthy little railroad was abandoned and scrapped, the tunnel was enlarged and lined with concrete for the highway.
Darrin,
The 15.4' vertical clearance provided is from the Washington State DOT bridge log and is identified as the max vertical clearance. I just looked at the WSDOT bridge log again and they have updated there log and now provide a minimum clearance of 15'-2". I updated the measurement on this site to match the minimum.
HOWEVER, you should contact the WSDOT Commercial Vehicle division and have any questions answered by them since they should have diagrams made to the tunnel. Here is a link to there website.
Michael, I have basically the same question as Dave but for a large class A motorhome. Our rig is 13' tall so the center clearance of 15.4' you've provided is sufficient, but I'm worried about the vertical clearance at the shoulders. Can you provide that measurement as well? This will let me know if I need to drive down the center or not. Thanks! Darrin
I have been asked if the Fort Columbia Tunnel can accomodate a travel trailer (height wise) with a A/C unit on top. My initial response was sure, but then I started to 2nd guess myself. Can you help me by providing the height of the tunnel?