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While a large amount of research has been performed in recent years on characterizing wildfire ashes and determining the hydrological properties of slopes post-wildfire, fewer studies have concentrated on the overall engineering behavior of ash. This study addresses this need by examining the compaction, shear strength, and hydraulic behavior of wildfire ash and ash/soil layered specimens. Unique chemical and physical characteristics of wildfire ashes were shown to influence the ash engineering behavior. Ashes in the as-received condition have a silty sand grain size distribution with higher than expected surface areas (>1 m2/g). Chemically, ashes contained silica, aluminum, calcium (in the form of carbonates) and residual organic carbon from incomplete combustion. Maximum dry unit weights ranged from 13 – 16 kN/m3 at optimum moisture contents between 20 and 30%. Hydraulic conductivity of samples varied between 10^-4 and 10^-5 cm/s. A wet deposited layer of fine-grained ash on top of compacted sand reduced the hydraulic conductivity of sand by 1 – 3 orders of magnitude. Shear strength of ash/sand layered specimens demonstrated that ash was fairly stiff, with an average friction angle of 28 degrees. Void ratios of specimens were consistently higher than expected for a silty sand fabric (usually above 1.0). Ash particles were irregular in shape with fibrous textures and had electrostatic attractive tendencies. The authors suspect that the unique chemistries present in ash (notably carbonates and organic char) contributed to the loose fabric structure and engineering properties that were atypical of a silty sand grain size distribution