Looks like a long time ago. Take Kiavo Drive north to its junction with Santee Lane. The park entrance and parking lot are immediately to the west on Santee Lane. Longer hikes are possible to the peaks 3040 and 3127 at the north boundary of the Preserve, but I don't know the mileage for those.
All mileages below are cumulative from the trailhead and all altitudes are from the topo map .
The trail begins with a steep descent to Hell Creek, with a nice wooden bench halfway down the descent located in shade. The trail sometimes goes along the bottom of the aqueduct, and sometimes on top of the wall. In one of the side canyon crossings before the first trail junction, a pipe must have been present to span the crossing with the aqueduct. There are remnant supports for the pipe on each end of the side canyon. In other side canyons farther along the trail, the canyons themselves have been dammed by the outer wall, allowing the water from those side canyons to enter the diversion.