The Log Jam
I originally spotted this tunnel on my way to Ben's house one afternoon several months earlier, but we never got around to checking it out.  Although I didn't originally intend to hit this system on this particular afternoon, it happened to be on my GPS, so I went ahead and had a look at it while we were in the neighborhood.  It turned out to be much, much larger than I had expected!
You can barely make her out in the distance, but that's Dani standing between the entrance of the fourth and fifth tunnels from the left.

Much further back, right next to the hospital, is the other end of the tunnel (the part I noticed originally).  We thought it would be easiest to start downstream.
The ceiling was really high in this section.  Oddly enough, it was a little higher just inside (i.e., upstream) than at the downstream end where we entered.
Up ahead is the opposite group of tunnels.  However, the ledge behind me is about 5' and covered with green slime... not the easiest place to climb.
This is looking back at the spot where we came out.  I'm getting a GPS reading right here; it's a little over half a mile from here to where we entered from.

Since we couldn't scale the ledge, we doubled back.
This tree became lodged in one of the tunnels.  Note that it had an almost intact root system.  This indicated to us that the upstream entrance was somewhere in the open rather than simply a narrow tunnel at the bottom of some drains.
At this point we returned to the car and drove back up to the opposite side of the street from where the section of the tunnel (i.e., with the slimy ledge) went under the road.
To the far left (out of frame) is the aforementioned short stretch of tunnel we just skipped.

The two tunnels that Dani is heading for are where we entered.
Although it started off as the pair of square tunnels shown above, within maybe 500 feet the architecture changed to the arched designed typical of the best Dallas systems (e.g., The Mouth, parts of Three-Way, The Drop-Off, and the second tunnel of the Rat Race).
This was a side tunnel that was completely sealed up with large stones and mortar.

While this was the largest example, many other smaller tunnels were similarly covered over throughout this place.
Continue to Part II