We were invited to join an interdisciplinary group at UW called the Small Scale Waste Management Program (SSWMP) that was studying on-site wastewater treatment, with a focus on septic tanks and the transport of contaminants through soil in septic tank effluents. We did both model studies of soil transport in laboratory columns Green and Cliver 1975) , and transport studies in the field (Alhajjar et al. 1988; Cliver 1984) . Field studies were done at homes where SSWMP had already installed groundwater sampling wells, so as to be able to study transport of contaminants from septic tank soil fields (Stramer 1984) . Inoculum was obtained by offering unlimited supplies of disposable diapers to mothers whose infants were receiving the oral polio vaccine, if the mothers would freeze and return any diapers with feces in them. Our laboratory thawed and assayed the feces. When at least 100 g of high-titer feces were accumulated, these were flushed down a toilet at a study-site home, and samples were taken from the septic tank and groundwater over time.