Help figuring out what happened to the east portal of Alpine Tunnel

[Kurt Maechner]

I'm doing a little work observing the gradual erosion of the east portal and I can't quite tell what's going on between three photos.  

The first photo is from the 1950s and one can clearly see the support redwood support structure, seemingly so far forward that it seems to be in sunlight.  However, in the 1986 photo by Al Pomeroy, there appears to be a large rock overhang and no redwood frame.  The last photo is one of mine from the 1990s.  Someone has unearthed the redwood frame again.  Yet, here the frame has a horizontal top, while the 1950s photo doesn't seem to have this.

Can anyone explain what appears to be a disparity?

[Al Pomeroy]

Kurt, I am no geologist, but I think there is a lot of rock moment. in this area. if I recall correctly the top of the mountain that was cut is all slide rock deposited by a glacier. this was why they had to timber the bore as they encountered no solid rock the entire length. so the theory that someone digs it out enough every few years to get inside and have a look. if I recall correctly there is a large rock slide not very far inside that prevents any further access.

I did have one image of the arch but because it was similar to another posted I did not add. I have done so now.

AL P.

[Kurt Maechner]

Do you think some of the arches have been crushed as rock has fallen?  It seems hard to believe this could happen when the portal is so full of slide rock.

[South Park]

  Never having gotten into the tunnel myself, I cannot say to what
degree rot has structurally compromised the integrity of the redwood.
It IS 1878-80 cut redwood ....  the good stuff, made of seriously rot
resistant old growth heartwood, ... BUT it is 140 years installed in
an unforgiving wet location too.

  Last year I replaced the beam structure in a residential deck that
showed signs of crushing at certain bearing points.  When I lifted
the structure off the supporting beams, I found that I could crush the
wood with my hands like reaching into a box of packing peanuts !
How the thing did not collapse under its own weight, nevermind the
vibrations of foot traffic, mystifies me still.

  With a million tons of rock and muck and wet bearing the full force
of gravity down upon that ancient structure, it is a real testamant to the
wood and engineering of the arches that it still stands at all.

  According to Poor, just a short section inside the tunnel was solid
rock, and no liner was required.

[Mike Trent]

Kurt, my understanding from years ago, was that there was so much concern that someone would be injured or even killed due to ever increasing numbers of railfans and other enthusiasts going inside the tunnel that it was intentionally blocked either by the Forest Service or some other agency.

Naturally, such an effort was pure folly, as it became even more desirable to get into it. After all, it's now only 108 years since a train passed through there. What could possibly go wrong?  

[Kurt Maechner]

This was true only of the west portal.  Ray Rossman who worked for USFS up there told me that they did seal up the west portal due to safety concerns.  Seal up, not in the sense that it was impossible to reopen, but enough to deter random folks from sliding down into a tempting hole.  The east portal, however, was already blocked naturally up by the 1940s, as evidenced by this Denver Library photo from 1949.

[Charles McMillan]

Kurt,

I believe that the first photo was taken at an angle . The photographer didn't shoot it square on, maybe do to the position he had to stand to get the shot.

I had been there years ago and you could still see the top of the arch. It was in the horizontal position.

Charles McMillan