Fine Print

They drive on a dirt road alongside the dried-out river name. The road is in pretty poor condition and they get shaken thoroughly.
Mary appears to be having a blast: Faster! Faster!
I don't think Annie would appreciate that.
Aww.
Annie says thanks from the rear seats.

After a bit less than ten minutes of driving, Mary points to a structure extending into the river bed and says: That's it.
Jack pulls over and parks the truck, and they get out. They walk through the tall grass towards the structure. A bridge further upstream catches Jack's attention.
Is that a road or a railway?
Mary says: Railway – why?
What's the condition like?
Not sure, it's been a while... We used to play there as kids, we even got a railcar to move once.
Sounds like serviceable enough to me. Do you know where it goes?
There's a train station a bit that way, with a bunch of other ruins in the area.
And the other direction?
I don't know. We followed it pretty far, the only thing we found is a switch.
Okay. Would be incredibly useful if that ended up somewhere in Ivydale.

They reach the structure. It's the entrance to a tunnel with a few walls that pertrude into the river and two weers? translate: Stauwehre / Wehre, one for controlling the inflow? tanslate: Zufluss, one for a bypass. The floor of the tunnel sits significantly beneath the river bed and, while the river bed is completely dry, there is still some water inside.