Document Type

Article

Publication Date

2021

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Abstract

The lack of iron-reducing capability in some red soils poses an issue for determining the suitability for on-site wastewater treatment systems (OSWWTS). The Arkansas Department of Health allows for placement of OSWWTS in certain red-clay soils that have the potential for iron reduction and do not show expansiveness upon wetting, but only in the Ozark Highlands (Major Land Resource Area [MLRA] 116A), which is referred to as the red-soil exception. The objectives of this study were (a) to confirm the nonexpansiveness and iron reducibility of select soils in the Ozark Highlands that meet the criteria for the red-soil exception, and (b) to compare the expansiveness and iron reducibility of the residual or colluvial red-clay soils of the Ozark Highlands with those in four other MLRA region groupings in Arkansas. Fresh and archived soils were used to create a 51-sample dataset from the 38- to 50-cm soil depth interval for analyses. The alluvial soils of the Red and Arkansas River valleys had a mean coefficient of linear extensibility (COLE) of 0.116 mm mm–1, whereas the residual or colluvial soils from the other MLRA regions evaluated had lower (P < .01) COLE values. Soils from the Red and Arkansas Rivers region changed red color (∆A) the least (∆A of −8.6 in the LAB color scheme; P < .01) compared with soils from the other regions. Results of this study indicate that the red-soil exception, as used by the Arkansas Department of Health for determining OSWWTS suitability, could be expanded to include soils from several additional MLRAs with additional, site-specific information.

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