Soil pedogenic processes produce an aggregation of soil particles which results in the development of soil structure. In turn, the development of soil structure increases the porosity and interconnection of soil pores. This process has a positive affect on the rate of fluid movement. When soils are moved, manipulated or compacted, the soil structure is damaged or destroyed or particles rearranged, which for many soil textures and flow regimes, reduces the soil's ability to transmit fluids.
Codes which govern the design of individual sewage treatment systems were developed under the assumption that systems were to be placed in natural soils. Therefore, if a proposed system is to be designed for an area of disturbed soils, the methods described in the code may not directly apply. This may result in premature hydraulic failure of the system. The application of Minnesota's ISTS code in disturbed soils has resulted in failures at a frequency of concern to the state regulatory agency. Revisions to Minnesota's code classifies systems placed in or on disturbed soils as being experimental. The classification is meant to identify these systems as having an unknown degree of reliability and to provide a data gathering process at the state level to monitor the performance of various designs to overcome disturbance.
This paper describes the problems associated with disturbed soils, the methods of proper field identification, how to quantify the extent of disturbance and briefly discusses some mitigative measures in an attempt to overcome these limitations.