Pete Giordano said:

I'm not sure which tunnel you are talking about. There is an old bridge on your way upstream, cross the bridge and continue up until the road falls apart. There is an old aquaduct inlet there. The waterfall is just upstream around a bit of a corner from there. You can also bushwack down from the road above it. The waterfall is a sweet 30' into a small pool, it then turns to the right 90deg. and falls/slides down another 50' or so. The canyon is quite steep around here but it is possible to hike around the falls.

I know where you are talking about I think.  We saw the intake, but continued up the hill, which is where the tunnel is.  On the top side of the tunnel, you can see the upper part of the falls and see where the waterfall turns the corner.  Pretty cool….I want to hike down to the bottom of these falls to get a better look at them.

We ended up continuing up the road and then scrambling up an old slide to an old spur road.