This is one of the backyard scuba stories I love so much.  Nurit and I took Missy the Brave for a walk last weekend in the Chapman Woods area about a mile south of here.  We started walking in the nice, eclectic, upscale residential neighborhood and came to a fenced area that looked like the back of a poorly maintained park or a weird institution of some type.  So we walked around it to see what it was.  in short order we came across a large boulder with this plaque on it.

The inscription:

The area is now run by a water district and peeking through the fence one can still see the remnant of the dam built almost 200 years ago by Joseph Chapman.

Very cool find.