Microorganisms in the soil decompose many of the remaining contaminants. However, the soil cannot remove dissolved solvents, automotive and lubricating oils, drain cleaners, and other household chemicals that can easily percolate into groundwater. If the absorption field is properly located, designed and installed it will accept septic tank effluent for a very long time. Minimizing household water usage and waste output will extend the life of the absorption field and help keep it in good operating condition. The size and placement of the absorption field is determined by the type and depth of soils on the site, as well as the sewage load it is expected to handle.
Some soils are better than others for placement of an absorption field.
In sandy soils, for example, water may pass through too quickly to be treated efficiently, while heavy clay soils may not allow enough flow. Your county conservation district can help you estimate the type, depth, and location of the various soils on your property. A final determination of their suitability for septic systems will be made by your local sewage enforcement officer. The absorption field ceases to function when the soils surrounding it become saturated. This can happen when the system is overloaded or when the water table rises to the level of the absorption field.