Graham - Thanks for that link to the earlier AP thread with the DUSEL discussion. Very interesting read. Seeing that that was 6+ years ago and nothing further has developed, it would appear that this project is dead.

Having snooped around the Scenic area many many years ago, I can state that the airflow through pioneer tunnel is significant when a train moves through the tunnel. I believe that GN placed steel covers over all of the passages between the main tunnel and pioneer when the ventilation system was installed in 1956. These passages have a small door to allow pedestrian access to the passage. I don't know how much effort was made to make these covers air tight and how much it may have been compromised in the intervening years.

Also, there is a considerable water flow out of the mouth of pioneer tunnel.

Finally, to comment on J.B.Bain's comments on the MILW. He is right on! The loss of this line was indeed unfortunate. BN did actually purchase the MILW line over Snoqualamie pass west of Easton. They expected export coal traffic to grow rapidly and saw this as an easy way to increase capacity. Unfortunately they did not look far enough into the future and abandoned this line in the late 1980s, long after the rest of the MILW lines west was gone.