What are Septic Mound Systems?
Mounds were developed to overcome three natural conditions: slow or fast permeable soils, shallow soil cover over porous bedrock, a high-water table. A site that has any one of these three conditions (or a combination of them) is not suited for a conventional septic system. Because acceptable soil conditions are not always found below the surface, the mound allows the conditions to be created above the surface.
The mound is a drain field that is raised above the natural soil surface. The mound is composed of a sand fill that has a gravel-filled bed and a network of small diameter pipes known as the distribution system. From the pump chamber, effluent is pumped through the pipes in controlled, low pressure doses so that uniform distribution is achieved throughout the bed. The effluent comes out of the pipes through small holes and trickles downward through the gravel bed and into the sand. Treatment occurs as the effluent moves through the sand and returns to the natural soil.
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​Advantages of Mound Systems:
  • The mound system enables use of land that would otherwise be unsuitable for in-ground or at grade onsite systems.
  • The natural soil used in a mound system is usually the top layer, which is typically the most permeable.
  • A mound system does not have a direct discharge to a ditch, stream, or other body of water.
  • If care is taken, construction damage can be minimized since little excavation is required in the mound area.
  • Mounds can be used in most climates.
Disadvantages of mound Systems:
  • Construction costs are typically much higher than those of conventional systems.
  • Since there is usually limited permeable topsoil available at mound system sites, extreme care must be taken not to damage this layer with construction equipment.
  • The location of the mound may affect drainage patterns and limit land use options.
  • The mound may have to be partially rebuilt if seepage or leakage occurs.
  • All mound systems require pumps or siphons.
  • Mounds may not be aesthetically pleasing in some cases.