Comparison of field measured soil absorption field loading rates and loading rates estimated from soil morphologic properties

Concerns from local health departments regarding premature septic system failure (less than 1 year from installation) has led to an investigation of septic system soil absorption field design parameters in northeast Indiana. The objective of this study was to compare the loading rate based on field measured saturated hydraulic conductivity (LR_m) across a toposequence to the estimated allowable loading rate (LR_e) based on soil morphological properties. Saturated hydraulic conductivity measurements were determined by a compact constant-head permeameter at five landscape positions, at four depths (surface horizon, upper argillic horizon, transition zone between the argillic horizon and till parent material, and till). Results showed that for all depths, the LR_m was smaller than LR_e. Results from this study suggest that the current method of using soil morphological properties to determine the loading rate may overestimate the ability of the soil to properly disperse septic system effluent.