Ground‐Water Mounding Due to On‐Site Sewage Disposal

Abstract

Localized ground‐water mounding beneath larger on‐site sewage disposal fields (leach fields) may be a major problem which previously had not been adequately addressed. Existing methods to predict mounding, mainly developed for ground‐water recharge spreading basins, are reviewed for applicability to sewage disposal fields. A most appropriate and accurate method is selected and considerably simplified to provide a convenient, straightforward prediction procedure for regulatory agencies and designers. The major simplification, to a single equation, is particularly accurate after longer wastewater application times, of say 10 to 20 years, when mounding is of most concern. Sensitivities of the procedure to the various simplifications, site factors, and design and management options are discussed and presented in graphical form where significant. Alternative means to reduce mounding are reviewed. Mounding problems and potential mitigation measures should be made more widely known, and long‐term field verification of the theory is needed.