The steady-state flow of Newtonian and non-Newtonian dense aqueous slurries in horizontal pipes has been analyzed using a two-layer model, consisting of a top layer of flowing suspension and a bottom bed of stationary or moving particles. The coarse solids used have a wide range of particle density and particle size distributions. The fluids studied were designed to simulate U.S. Department of Energy Hanford site waste slurries. The most important changes from previous models include an independent settling analysis for different particle size fractions, effects of particle shape on settling velocity, and a new correlation for the turbulent particle dispersivity. The results indicate that the turbulent dispersivity of settling particles is sensitive to particle size and density. The model gives good estimation of the critical deposition velocity as the minimum of the pressure drop versus superficial slurry velocity relation. The existence of a stationary layer can be observed and predicted by the model under laminar and turbulent flow conditions.