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1 <br />1 <br />water supply contains as little as one plaque -forming unit of virus per 50 <br />gallons of drinking water in a community which utilizes 50 mgd (0.2 percent <br />' of which is ingested as drinking water) at a 30 percent infection rate, 600 <br />individuals would daily contract a variety of clinical and subclinical <br />infections. Thus, the presence of even one detectable virus unit in a <br />' water supply poses a potential disease hazard. <br />' 3.4.2 REGULATIONS <br />' There are no regulations directly governing the treatment efficiency of a <br />septic tank, since that value is very difficult to obtain. Instead, the <br />' design and installation are controlled by Chapter 1OD-6 of the Florida <br />Administrative Code. <br />It is assumed that if proper design and installation procedures are <br />followed, efficient septic tank operation will be achieved. The use of <br />' septic tanks does require periodic maintenance that includes pumping out <br />the accumulated scum and sludge. It has been estimated that approximately <br />' 70 gallons per capita per year of this septage builds up in properly <br />functioning systems. <br />' 3.4.3 CASE STUDIES <br />' A recent USGS study in areas serviced by septic tanks in Dade County, <br />Florida, showed that the effluent is having a significant impact on <br />' groundwater quality in certain cases. From 1971 to 1974, five established <br />neighborhoods in Dade County with septic tank densities of less than four <br />' per acre were monitored. The study found that where the tanks were less <br />than 5 feet above the water table, groundwater up to 95 feet away <br />' horizontally and 20 feet deep was often unfit to drink. <br />The Septic Tank Task Force of the Department of Environmental Resources <br />' Management in Dade County, first organized in 1971, reconvened in 1975 to <br />' IRC.VB4 <br />6/4/87 <br />