In-Ground Soil Absorption Areas
- The soil absorption area receives the liquid effluent from the septic tanks and distributes it over a specific area.
- Equal distribution of the effluent is very important to the proper functioning of the system.
- In a gravity system, this is achieved by a distribution box
- In a pump system, this is achieved by pumping the effluent through laterals. These laterals should be accessible through lateral risers.
- The effluent then filters through the soil under the pipes and is treated chemically and bacterially by the components of the soil.
- The size of the soil absorption area is based on the size of the house and the percolation rate of the soil.
- State law requires that there be at least four feet of usable soil for the effluent to percolate through before it reaches the water table.
- The type of system installed will depend on the slope of the property, the depth of usable soil, and the percolation rate.
Types of Conventional Soil Absorption Areas
- An inground seepage bed
- For seepage beds, the entire absorption area is excavated and lined with crushed stone.
- The pipes (laterals) are then placed over the stone and the entire bed area serves as an absorption area for the effluent.
- Leaching chambers may be used in place of gravel.
- A set of trenches
- A standard trench absorption area consists of two or more excavated trenches in which perforated pipes or laterals distribute effluent into a layer of crushed stone under the pipes.
- The effluent is then absorbed into the soil where it is renovated.
- Elevated sand mound
- The elevated sand mound system is used in areas with reduced permeability, shallow soils, and poor drainage characteristics.
- Soils in these areas require the addition of sand above the ground to provide for adequate renovation of the sewage prior to reaching the water table.
- The absorption area is constructed similarly to a standard seepage bed or trench, except that the system is required to use pressure distribution and a layer of sand must be placed between the crushed stone and the natural soil cover.
- A soil berm is placed around the mound to protect it and to provide a suitable base for the establishment of a vegetative cover.
Types of Non-Conventional Soil Absorption Areas
- At-Grade bed
- An at-grade bed is similar to an elevated sand mound, but without the sand.
- Drip Irrigation System
- Drip irrigation systems distribute the treated effluent into the soil using drip tubing that is installed just below the ground surface.