Why not bore out the Pioneer Tunnel and add a second track. The project is largly done now, enlarge what is there now and bore out the rest of the way. Modern boring machines are able to grind through solid rock so blasting probably wouldn't be needed and so project would be a minimal threat to existing tunnel. In operation, run train through one tunnel, while it's blowing out, run through other. However, I think it's going to be a long, long time before economy recovers enough to tax capacity of existing line. (BTW, I don't think Trains article considers how much further north Cascade tunnel is compared to California lines and what a difference that can make on snowfall and duration of snow pack.)