|Description:||This historic 1935 diagram, which had been digitally enhanced and colorized, depicted three renderings of properly constructed manhole covers of the “overlapping” type. Manhole covers were found to be quite important to maintaining safe and secure sanitation systems.|
This was one of a series of instructional drawings used by the Minnesota Board of Health to train its state public health workers. The purpose of this and other like images, and the training was focused on protecting potable water supplies from bacterial contamination, due to incorrect disposal of waste, such as sewage, which might foul ground water, rivers, lakes, and streams. The descriptive information accompanying this drawing referred to a governmental publication with instructions describing the correct placement and construction of a detached home privy. The specific citation was, “Minnesota State Board of Health, Division of Sanitation, Water Supplies and Sewerage Systems for Country Homes, 1933, p. 34”.