Not venting really, just rambling. Mostly I was kind of surprised because it’s been a couple weeks since we had any rain.
It appears to be a two-fold problem. Water is seeping in through the wall of the tunnel on the uphill side. The curved track is on a grade going through the tunnel. Somehow I ended up with a slight dip in the middle, which allowed water to accumulate. Filling in the dip with cement should help with the drainage.
I’m not sure about the seepage issue at this point. I think that a lot of it is due to water collecting in the hollow cement blocks that form the sides of the tunnel. These were filled with dirt and gravel during construction. The access panel rests on the top of the tunnel walls, and rainwater likely was pouring in through the gap. I plugged the top of the wall with cement today, hopefully that will prevent water getting into the wall in the future.
The repairs I’ve made are kind of patchwork, but I think they’ll be sufficient. If not, I’ll have to undo these repairs and do something much more extensive. The tunnel itself can’t be dismantled. On the plus side, if the more extensive work becomes necessary, I could always write about it for the last page of GR.
I think the lesson here was that I should have cemented the floor of the tunnel when it was first built.