In the dark I thought I heard somebody call

So here's a summation:

• Entered graffiti-covered entrance. A few feet in, I turn on my flashlight and discover that there is a giant gaping hole in the floor a few feet ahead, which explains why there was no water coming out of this drain.
• I skirt around the edges of the hole. It's only a few feet deep, but it's got a fair amount of water rushing through it, and I would rather not get wet because it's below freezing out. So there's a decently broad ledge around it
• One of the things you don't notice from photographs of draining expiditions: your depth perception is totally messed up. There's not a lot of light and what with the lack of landmarks it's hard to tell just how far ahead you can see. So I see what looks like two pillars in the distance-- one flush with the right side of the tunnel, the other crooked and maybe leaning against the right pillar? But no, that's not it-- it's steps! The right 'pillar' was the steps themselves, the left pillar was the water rushing down the slope. So.
• After the steps I get out my non-sucky flashlight (i.e., not the pocked maglite) and continue on. The tunnel gets a little narrower and changes texture. Also, there is a offshoot tunnel. It's narrower and about as tall as I am in the very middle, and since I want to avoid walking in the water I have to stoop to do walk up the tunnel.
• This tunnel turns! and turns. it's significantly more crooked than the main tunnel. It eventually dead-ends in what looks like a rain chamber-- water keeps falling in big drops down to the chamber floor, at which point it runs out down the tunnel I was travelling up. I don't check it out in a lot of detail; I'm trying to avoid getting wet.
• So back down to the main tunnel! It is at this point I notice the bright orange distance markers on the walls. Evidently, the tunnel I just went down starts 660 ft. from the entrance.
• And so I keep walking down the main tunnel. At around 1575~ ft there's another offshoot tunnel-- this one is much wider, slightly taller, and it starts halfway up the main tunnel's wall, at about shoulder or neck height. As far as I can tell, it looks like the water there flows down a steep step. I decide not to try and scramble up there, because water is sheeting down onto the floor and (say it with me this time) I don't want to get wet. After this offshoot, the water in the main tunnel becomes deep enough to cover the entire floor. I decide to turn back, because I'm alone and using two flashlights with who-knows how old batteries, and I don't want to get wet.

So I guess I'll try again in the spring once all the snow has melted and it's warmer and dry! But this was totally awesome! But more interesting than the first expedition.