Hydraulic considerations in designing an oil spill control system for a stormwater outfall

Oil spills have been identified to be a serious problem in the Humber Creek subwatershed in Toronto. To capture spilled oil at the storm water outfall, an oil spill control system was designed to perform under different flow conditions. The spill control system consists of an on-line triangular lateral diversion channel (1.7 m by 0.6 m) and an off-line tilted-plate oil–water separator (7 m by 5.4 m by 5.9 m). To investigate the hydraulic behaviour of the spill control system under different flow conditions, a physical model study was conducted at the National Water Research Institute's Hydraulics Laboratory in Burlington, Ontario. The model results confirmed the design conveyance capacity of the lateral diversion channel and indicated that floating objects and settleable solids could be trapped inside the oil–water separator under various flow conditions. A vortex was also observed inside the oil–water separator and was likely caused by the lateral diversion channel. During high flows, the flow through the oil–water separator was controlled by the flow backup from the storm water outfall. Key words: oil spills, lateral channel, oil–water separator, hydraulic models, storm conditions.