EXPERIMENTAL EVALUATION OF SEDIMENTATION BASIN PERFORMANCE FOR ALTERNATIVE DEWATERING SYSTEMS

Abstract

The effectiveness of four sediment removal/water control treatments, each designed to dewater the 155-m3sedimentation basin in 24 h, was evaluated using 100-m3 inflow hydrographs (35-mm, 2-yr runoff events) from a 0.4-hadenuded construction site containing 454 kg of sediment. The treatments were a perforated riser alone that discharged26.1 kg of sediment and had an overall sediment retention efficiency of 94.3%; two internal barriers designed to trisectthe basins volume with a perforated riser, significantly reduced the sediment loss below that of the perforated riser aloneto 20.4 kg; a skimmer alone discharged the least total sediment at only 14.3 kg; and trisecting the basin with barriers,with the skimmer, did not improve the capture efficiency of the basin over that of the skimmer alone. All treatmentsremoved 100% of soil particles and aggregates larger than 75 m. The basin sediment was completely mixed during theentire inflow/dewatering event and the effluent particle size distribution was the same as that observed for the influentsediment smaller than 75 m. Particle sizes retained between 0.1 and 75 m ranged from 77 to 100% with the poorestretention in the 6 to 12 m range.