Suitability for Septic Tank Filter Fields and Taxonomic Composition of Three Soil Mapping Units in Arkansas1
- M. D. Ransom2,
- W. W. Phillips3 and
- E. M. Rutledge4
Although soil surveys of Washington and Benton counties, Arkansas, show large areas of soils with severe limitations for septic tank filter fields, houses with septic tank systems are rapidly being built on these soils. The soil survey criteria for soil evaluation differ from those of the state regulatory agency. Also, mapping unit inclusions of other soils can account for different evaluations. The objectives of this study were to evaluate three mapping units (i) for suitability for septic tank filter fields according to the differing criteria used by the Soil Conservation Service (SCS), the Arkansas Department of Health (ADH), and the U.S. Public Health Service (USPHS); and (ii) for their taxonomic composition. The mapping units were Peridge silt loam, 1 to 3% slopes (fine-silty, mixed, mesic Typic Paleudalfs); Nixa cherty silt loam, 3 to 8% slopes (loamy-skeletal, siliceous, mesic Glossic Fragiudults); and Clarksville cherty silt loam, 12 to 50% slopes (loamy-skeletal, siliceous, mesic Typic Paleudults). Approximately 14 sites in each mapping unit were selected at random for evaluation. The small number of sample sites caused a wide confidence interval about the results. Sampling of the Clarksville mapping unit was biased due to equipment limitations.
The Peridge unit contained a 50:50 distribution of similar and dissimilar kinds of soils. Of the Peridge unit pedons, 50% were rated moderate and 50% severe by SCS criteria, 79% passed ADH criteria, and 86% passed USPHS criteria. All Nixa unit pedons were Nixa and similar kinds of soils, all were rated severe by SCS criteria, and all failed ADH and USPHS criteria. The Clarksville unit contained 85% Clarksville and similar kinds of soil. All pedons in the unit were rated severe by SCS criteria, and 62% failed ADH and USPHS criteria.
We suggest that mapping units be evaluated by their range in soil properties and by their suitability for use and management in two independent steps.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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