Rockridge Shopping Center quarry

Halfway up Broadway, where it crosses 51st Street/Pleasant Valley Avenue, there used to be the big Bilger quarry. The Oakland Paving Company mined a body of traprock (mapped as Franciscan quartz diorite, a near-basalt), crushed it, and shipped it out via a rail spur that crossed Broadway at 42nd Street and curved toward the former depot at 41st and Shafter streets (you can see the trace in Google Maps). This is what’s left. I’m standing at the very edge of the Catholic cemetery overlooking the Rockridge Shopping Center. Beyond it is a remnant of the original hill where California College of the Arts sits. It was a family estate before it became a school; perhaps they couldn’t stand the quarry operations and decided to give the place away. Still, the views from there are very nice, and the old quarry walls beautifully display the sandstone that adjoins the traprock as well as the faulted contact between them. Click the photo for a bigger version.

The old pit holds water from the Rockridge Branch of Glen Echo Creek after it traverses the Claremont Country Club golf course. A glory hole at the other end carries the overflow into a culvert that runs down the west side of Broadway, daylighted in two small places (by the new Kaiser parking structure and along Brook Street) before it joins Glen Echo Creek proper just north of 30th Street. The photo below shows where the creek joins the pit. I think the little waterfall on the left must be drainage from the country club grounds. It’s still pretty, and both are seasonal hidden treasures. The creek is barely visible from the other side—you have to stand by that little promontory at the front corner of the Longs store.

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