Conrock was a sand and gravel business that operated the largest "man-made" hole in 1970s at Sun Valley, CA, northeast part of the San Fernando Valley. The "Con" in Conrock stood for "Consolidated" Rock Products, as they were a consolidation of many smaller sand/gravel/concrete companies in the greater LA area.
Here is a view of Conrock's, General Electric, 44 ton switch engine. As you can see it has protective sheet metal cover over each end of the hood, this cover kept sand from falling into the engine compartment.
Seen behind the 44 ton switch engine in the background are Southern Pacific ballast hoppers. The railroad used crushed rock from the pit for ballasting their tracks throughout Southern California. Signor Collection
Here is a ballast train waits on the Sun Valley Siding, with an EMD 1500, diesel locomotive. This train was to back down the mainline to supply ballast for the Valley Line's repairs caused by the 1971, Sylmar Earthquake that happened a few day before this photo was taken.