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1 <br />' An outbreak of waterborne transmission of disease was reported in Dade <br />County. The major incident occurred in 1974 in Richmond Heights, where an <br />outbreak of Shigellosis was linked to contamination of the community supply <br />' well by a nearby septic tank. The contaminated well, drilled to 25 feet and <br />cased to 20 feet, was located 150 feet from the septic tank. Dye studies <br />' showed that the leachate travel time from the septic tank to the well was <br />only 6 to 9 hours. The indicated pathogen, Shigella sonnei, has an average <br />survival time of 10 days in the free environment. Thus, there was <br />sufficient time for this organism to reach the well, pass through the <br />distribution system, and infect consumers. <br />An argument that is often heard for septic tanks is that their effluent is <br />' needed to recharge the aquifer. It has been shown that the recharge <br />' IRC.VB4 <br />6/4/87 <br />review the USGS report and related studies. The Task Force outlined <br />several cases in which waterborne transmission of disease has been linked <br />to seepage of septic tank effluent. The following examples illustrate the <br />' <br />magnitude of microbial transport in midwestern states, which have permeable <br />or creviced limestone rock much like that found in Dade County. <br />a. Polio virus and coliform bacteria have been isolated on <br />' <br />several occasions from well water in Monroe County, Michigan. <br />One of the wells tested penetrated a limestone formation <br />' <br />lying underneath a shallow layer of glacial drift. Pollution <br />was determined to have originated from a septic tank located <br />' <br />100 feet from the well. <br />b. An infectious <br />hepatitis epidemic in Posen, Michigan, was <br />caused by septic tank drainage through limestone into shallow <br />twells. <br />C. In Minnesota, an outbreak of gastroenteritis was traced to <br />' <br />contamination of a well drilled to 198 feet (cased to 8 feet) <br />into Platteville limestone. The source of pollution was a <br />' <br />septic tank located 110 feet from the well. <br />' An outbreak of waterborne transmission of disease was reported in Dade <br />County. The major incident occurred in 1974 in Richmond Heights, where an <br />outbreak of Shigellosis was linked to contamination of the community supply <br />' well by a nearby septic tank. The contaminated well, drilled to 25 feet and <br />cased to 20 feet, was located 150 feet from the septic tank. Dye studies <br />' showed that the leachate travel time from the septic tank to the well was <br />only 6 to 9 hours. The indicated pathogen, Shigella sonnei, has an average <br />survival time of 10 days in the free environment. Thus, there was <br />sufficient time for this organism to reach the well, pass through the <br />distribution system, and infect consumers. <br />An argument that is often heard for septic tanks is that their effluent is <br />' needed to recharge the aquifer. It has been shown that the recharge <br />' IRC.VB4 <br />6/4/87 <br />