Sediment entrainment during pipeline water crossing construction: predictive models and crossing method comparison

Sediment entrained during pipeline water crossing construction has the potential to adversely affect downstream aquatic biota and their habitats. Past construction monitoring studies were used to derive equations for the prediction of peak and mean sediment entrainment rates associated with different phases of open-cut (wet) construction. Correlation coefficients and suspended sediment concentrations measured downstream of simulated open-cut crossings indicate that entrainment equations more closely predict mean concentrations as compared to peak concentrations. The same data set was used to demonstrate that isolated (dam and pump or flumed) crossing methods were effective at reducing the amount of sediment released during pipeline installation underneath small to medium sized watercourses. The effectiveness of isolated crossing methods was in some cases limited by pump failure or insufficient capacity, dam failure, poor dam seals, and poor containment of pumped ditch water. Key words: pipeline constructi...