Design and Construction of Leaching Systems in Fill Based on Permeability

Abstract

On‐site sewage disposal systems (commonly septic tank/soil absorption systems) provide a viable and permanent management alternative for the treatment and disposal of wastewater in rural, unsewered communities. Population expansion in rural and semirural areas has presented challenges to develop economical, efficient on‐site sewage disposal systems in severly limited areas. Building sewage disposal systems in fill can be used to overcome site limitations such as high groundwater and shallow depth to ledge. An efficient design balances the requirements of hydraulic and renovation capacity, which depend strongly on the compacted, in‐situ permeability of the emplaced fill specified in the design phase. This paper reviews the procedures used to design subsurface sewage disposal systems in emplaced fill, to illustrate the importance of fill permeability and its relationship to system performance and economy. Procedures are suggested for identifying and verifying suitable material and for placing fill to meet design specifications. These procedures are illustrated by a case study of a site in Ashford, Connecticut.