Envelope reads "Hetch Hetchy Mitchell tunnel explosion 7/18/30." Photograph shows a group of approximately five wooden buildings standing in a valley which has a layer of water in it. In the foreground some sort of gas or water tank can be seen. This photograph was printed in the Oakland Tribune on July 18, 1930 (p2) with the caption "Bunk houses of mitchell Camp which tragedy entered without warning." For more information about the Mitchell Tunnel explosion see h99.1.482.