Typical of water and sewer line crossings, this historic 1939 photograph revealed structural details that can still be found in any contemporary Minnesotan municipality. A leak in this water main, which occurred close to a sewer pipe joint, made contamination of the water supply possible. This is especially true when a vacuum occurs in the water pipe. The descriptive information accompanying the photograph referred to a governmental publication dealing with this topic. The specific citation was, “Minnesota Department of Health, Division of Sanitation, Manual of Water Supply Sanitation, 1941, Section 12, p. 22”. This was one of a series of instructional images that were used by the Minnesota Board of Health, in order to train its state public health workers. The purpose of the images, and the associated training, was focused on the orderly disposal of waste, including sewage, in order to prevent contamination of potable water supplies.