Sadly, I thought all my gutters were plumbed together and went to a single, large well.

It seems each leader feeds it's own underground plumbing and dry well. The two dry wells I dug up so far are pitiful. One's a plastic thing full of pebbles with barely enough capacity for a good long ****. The other is a large pipe thrown into the ground vertically that's about 8' long, with no percolation holes that I could see while danging a super-bright LED flashlight down there on a string. And, it smelled like rotting racoon flesh. Bleah. Though the vertical pipe one confused me, because I pumped 600 gallons per hour for 3.5 hours before the length of hose I shoved down there wasn't long enough. So, I'm not sure if there's a tank there or not, or maybe it's just so far down I haven't hit it with the shovel yet.

And you're right, with all the dirt, rocks, bricks, gravel I've uncovered thus far, there's no shortage of backfill material. I'll just have to sort the debris so the larger pieces go in and the stupid annoying pebbles (and dirt) stays out.

Fun!