Percolation Tests, Soil Texture, and Saturated Hydraulic Conductivity in Lacustrine Soils in North Dakota

Authors:
  • JCJ. F. Conta
    J. F. Conta
  • JRJ. L. Richardson
    J. L. Richardson
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Abstract
Percolation tests were unreliable estimators of in situ saturated hydraulic conductivity (Ksat) if the data were to be used to predict soil permeability for on‐site septic disposal systems in soils with > 0.35 kg/kg clay (r = −0.38 [nonsignificant], p = 0.01). The wide variations in percolation rates (10.5–135.9 min/cm) measured on similar pedons with silty clay or clay textures were attributed to the pedal nature and vertic properties that exist in high clay content soils of the area. Percolation rates yielded good estimates of Ksat in soils with < 0.35 kg/kg clay (r = −0.79**, p = 0.01) (** indicates significance at the 1% level). The soil clay content and Ksat rate correlated with sufficient precision over a wide range of soil textures for clay content to be used in predicting permeability and to permit using permeability to interpret the soil suitability for septic absorption fields. This research showed that clay content could reliably form the basis of a sanitary code.A comparison of in situ Ksat rates and estimated permeability ranges used by the Soil Conservation Service revealed that many fine‐textured soils have permeabilities greater than the Soil Conservation Service ranges indicate. The ranges of permeability should be expanded for these fine‐textured soils to include more rapid permeabilities.