The Movement of Bacteria and Viruses Through Porous Media

This report is the result of a request by the State Board of Examiners of Water Well and Pump Installation Contractors. The Board is in the process of formulating a more reasonable set of guidelines which control the location of wells designed to produce water for human consumption and/or food processing with respect to potential or existing sources of ground‐water pollution. The pollution of ground‐water supplies is artfully treacherous. It appears belatedly and often is not recognized until a relatively large area has been contaminated and perhaps one or more individual water supplies have been rendered unfit for human consumption. It is known that soils and aquifer materials have capacity to remove or “filter” some types of contaminants, and something is also known of the limitations in this regard. It is with these thoughts upon which this report is based. The report is designed to briefly describe the results of several pertinent ground‐water pollution investigations and present current and potential standards for governing “safe distances” between domestic‐food processing wells and sources of potential or existing pollution. The recommendations are meant to emphasize the fact that no one set of distances are adequate and reasonable for ALL conditions. Whenever possible the “safe‐distance” between a subject well and a source of potential or existing pollution should be based on local conditions. It is important that we develop knowledge that will permit continued use of the soil mantle as a waste‐water treatment system and at the same time permit continued use of ground water for human consumption and/or food processing. Functional legal, administrative and engineering mechanisms must be developed to maintain this combined usage. The Colorado Board of Examiners of Water Well Drilling and Pump Installation Contractors was established in early 1968. By October the Board adapted a set of rules and regulations which provide minimum standards for location, construction, modification or repair of pumping equipment. The Board's current concern is with the sanitary quality of those waters which are to be used for domestic purposes; in particular. human consumption. Realizing that proper sanitary protection of domestic wells involves the prevention of the intake of contaminants, the Board of Examiners introduced a set of standards which provides for the location of wells and well casings with respect to sources of contamination. The standards were chosen arbitrarily and do not consider the differences between chemical and biological contaminants. It is the purpose of this report to briefly point out some of the past and current developments regarding the nature of ground‐water pollution and, in particular, data related to studies of the length of travel of bacteria and virus‐laden water when injected on both soil surfaces and in water wells. Two distinctly different aspects of pollution travel are considered. They are: (1) the movement of bacteria and viruses downward with percolating water; and (2) the lateral movement of identical pollutants once they have reached the zone of saturation.