Doug provided all of today's photos, including the culvert (with gate) shown above, and the old flume seen below. Doug writes, "The features are of milled redwood and dated to the gun club period of operation... The salts in the ground aided in preserving many of wooden blinds and flume system which supplied fresh water..."
The image above shows a Byron Jackson centrifugal pump (post-1909). The image below shows a wooden culvert. Note the oil well and bluffs in the background.
Doug also writes that, coincidentally, "In the early 1930s our family, which supplied the Alpha Beta grocery store chain with beef, leased some of this area to graze cattle."
The photo above shows the pump, wooden culvert, and Doug's shadow. (Dontcha hate it when that happens?) Another closeup of the pump and its platform are shown below.