Though the bridge mentioned over Hwy. 49 looks like a railroad bridge, mainly because of its trestle type approaches, it never had rails and was used as part of a truck haul road to other quarries that supplied limestone to the San Andreas cement plant. The plant was also supplied with raw product from a large quarry they had off Camp 9 road that sits above Melones Lake. The limestone was finely ground, mixed with water, and then pumped down to the San Andreas plant. They had to clean out the pipeline periodically and would send a large ball called the "mouse" through. I don't recall how many hours it took to reach the plant. The Quarry is a good place for collecting calcite crystals. There is a neat limestone cave called Wool Hollow Cave on the edge of the Quarry. I also discovered a new cave there that I was first to enter. It started out as a 4" wide crack with air coming out that I mined out to gain entry. If you follow Camp Nine Road down to the river you can cross the bridge, go up the other side you will find yourself in Pickering Land after several miles and can come out at Schottgen ("shotgun") Pass.