On my last day in Tulsa for this trip, I walked the whole system, as far as it is walkable anyway.

I went in at the outfall, taking the tunnel on the right. There is one spot where it turns squarish, that apparently used to be a bridge over the creek before it was put underground. Just before the junction, there is a side tunnel that leads to a convenient exit/entrance.

The junction seems to be heavily reinforced. It must be under the highway and the railroad, because train and highway sounds are clearly audible.

The junction

At the junction, I first went into the leftmost, RCB tunnel. There is another exit not far up there, a steep incline up a square side tunnel that opens into a lightly forested area next to a residential neighborhood, in a railroad embankment. The infall is steep like Fiend said, probably a 45-degree angle, but when there is a dry part (as there was when I visited) it is only moderately difficult to get up and down without a rope.

Sadly, I did not encounter any bats on my trip.

There are slots between the two RCB pipes every so often, just large enough to squeeze through. I went back down the RCB I traveled to the infall, because the other one was too slick at the infall to get down without just sliding on my ass. I went into the other RCB through one of these slots, and walked down that back to the junction.

From the junction, I picked the upstream SEP with no water in it. These SEPs are interesting because they have a wall in the middle, presumably for reinforcement. After the wall ends, I noticed "ledge" formations on the floor. These indicated to me that there was rarely flow in this tunnel ... so I was pretty interested to find the end.

The end is a wall with some windows into the other tunnel on the right. The windows apparently serve as an overflow for the main tunnel! That explains why there is no/little flow in this other tunnel. I went through a window, and returned to the main junction via the tunnel with some water in it, and made my way out via the other tunnel to the outfall. By the way, the water in that tunnel is coming from some fairly large, but low and wide tunnels which I did not explore. Who knows, maybe those open up later?!