Olivenhain reservoir is one I have tried to reach several times, but we
failed on one road (washed out) & deadended on a second (blocked by gate).
The main route is a 6 mile hike up 1500 vertical feet.
A friend has offered to get me a private tour of the dam. 
I'll take either when I get the chance.

[Photo by P Konstantin]

This is all we could see of the dam when we hit the locked gates.

Olivenhain to the left and Hodges to the right.