Tunnel mystery solved

A few weeks ago I wrote about some mysterious tunnels that were being dug into the cliffs along the Mississippi. I have been watching the crew creating these with some fascination. The machinery, the ventilation systems, the precautions for rock collapse are all neat stuff. Doesn't this seem like an ideal construction site to explore after hours when the crew is gone? How cool to see the ancient limestone, hear the water dripping, and get a little claustrophobic? And of course, what an idea that your author would never, ever endorse.

Of course that doesn't mean a few pictures wouldn't help illustrate. Here is the entrance to one of the two tunnels showing the vent pipes that run down the sides of the tunnel. Each one is terminated with a round fan I suppose to bring in fresh air for the workers and remove exhaust from the machinery.

 Farther in the ground was really mushy and the air smelled of rusty water.The tire tracks are from a bobcat-size machine which gives a good sense for the tunnel dimension. This isn't a claustrophobic space although it gets dark pretty fast.

I learned later that part of the smell was coming from the sewer pipes the crew was repairing. The pipes were over 100 feet into the cliff and the only safe way to access was to bore a hole through the cliff wall. How do I know this? Meet Todd.

I was able to catch Todd while he was unloading his truck and he took a minute to explain the project. Apparently there are ways to access the tunnel from on top of the cliff but given the volume of sewage in the pipes it was not considered safe to send a technician. As Todd explained, if something happened and he got swept down the pipe with the sewage...uh, yeah, you can imagine.

I suppose it would have been even more true to the bike commuter spirit to have actually ridden in the tunnels. I did learn that bike gear, like clip shoes, is not well adapted to the tunnel rat environment. I got to work and the shoes needed some serious TLC. Not sure how the chain would've fared - maybe some day, I'll find out!

30 Days of Biking - Mystery tunnels

Biking along the Mississippi - especially before the leaves come out - you can see mysterious inlets, ravines, and the dark entrances to caves near the waterline. Some of these are real caves and others are man made. In either case it isn't everyday that something new shows up on the cave map.

So, I was quite surprised to see that some new caves were being dug into the bluffs right along my bike route. Equipment started showing up a few weeks ago and they cleared two areas. Here, there was a need to excavate more above grade so they built a gravel driveway up to the site.

I assume the corrugated metal tubes are to stabilize the entrance. The limestone in the cliff is very convenient for free landscaping mater...I mean very loose.

At the second site (below) you can see the shattered rock around the entrance. Once past this initial stage, they started tunneling into the cliff. I will get some better photos since the work is pretty cool to watch. The tunnel itself has a rectangular profile and so far it looks like they are going to leave the walls natural stone.

I have tried to ask one of the construction workers what the project was about but they aren't too responsive over all of the drilling noise. My assumption is that since these two tunnels are just below the East Bank of the University of Minnesota campus that they are meant to service the buildings on top of the cliff. In fact, just upstream there is an underground archive that does just that. This stuff is quite cool! And, all on the bike route to work...