After finding the locked gate next to the grey block building, we knew we needed to find another way in. One of Jaime's relatives had been to the Spark Plug mine recently, so he knew the area was open and that there was a way to get on the main trail.
By the way, the grey block building is a hydroelectric plant, used to supply the ranch with power. White Mountain Ranch was used to raise beef to feed the workers at the Spark Plug Mine. The hydroelectric plant looks like it's still functional, although the supply water doesn't run above-ground these days.
We pressed on ahead on the now-unpaved road that followed the power lines, knowing that at some point, we'd need to find a road that turned left.
A half-mile past the hydroelectric plant (Jaime kept track of the distance) we found our left turn. It's a well-beaten path and crosses under the power lines and over the old rock-lined aqueduct. The aqueduct is a small channel not much more than a foot wide.