Proper Soil Textural Sequence for Septic Tank Systems

During the mid 1990's, the South Carolina Department of Health and Environmental Control (SCDHEC) and the University of South Carolina (USC) entered a joint project to address concerns about groundwater contamination from domestic septic tank systems along the South Carolina coast. Evidence of system failures through the years had been documented in these areas of typically shallow mean groundwater levels. The project employed monitoring wells located along the South Carolina coast and also undertook an extensive modeling effort. The modeling revealed a perceived weakness in the traditional listing order of soils used by many environmental departments in classifying soils for septic tank and absorption field systems (STSAS). This paper will present the case for reordering these soils to better match their failure potential as indicated by the models.