Evaluation of Soil Class Proxies for Hydrologic Performance of In Situ Bioinfiltration Systems

The hydrologic performance of in situ bioinfiltration systems (bioretention systems with no fill media or underdrain) is quantified and soil classes are evaluated as proxies for design requirements. A one-dimensional (1D) Richard's equation model of a bioinfiltration system is used in combination with a dataset of soil hydraulic properties to conduct a Monte Carlo analysis of the effect of soil hydraulic properties; the results are summarized both by soil textural class and by hydrologic soil group (HSG), showing that textural class is generally a poor proxy for estimating the infiltration performance of in situ bioinfiltration cells (R-2 = 0.40). Because infiltration measurements are required to estimate the HSG, they are a better proxy for bioinfiltration performance (R-2 = 0.89). It is found that soil proxies do provide certain reliable guidelines: HSG-D soils always require engineered fill media with an underdrain; whereas underdrains are not necessary for sand, loamy sand, HSG-A, and HSG-B native soils. Minimum bounds on the design capture volume are generated for these soils which may be substantially larger than the surface storage volume. (C) 2016 American Society of Civil Engineers.