Oil Recovery From Under River Ice

Abstract

On March 7, 1978, a successful field test of the recovery of oil from under river ice was conducted on the North Saskatchewan River in Alberta, Canada. The ice was 28 inches (70 cm) thick, the water depth ranged from 1.5 to 7.9 ft (0.5 to 2.4 m) and the average water current was 1.3 ft/second (40 cm/sec). Dyed vegetable oil and crude oil were released under the ice upstream of a recovery slot which was 4 ft (1.2 m) wide, 400 ft (122 m) long, and placed at an angle of 30 degrees to the current. Almost all the vegetable and crude oil that was released under the river ice was intercepted by the slot and diverted to the slower current at the downstream end of the slot where it was readily recovered with a specially-constructed weir skimmer. From experiments in small 4 ft by 4 ft (1.2 m by 1.2 m) slots cut in the ice, it was determined that a slot would hold about a 5 inch (12 cm) layer of oil on the water surface for an ice thickness of 28 inches (70 cm) and an average current of 1.6 ft/sec (50 cm/s). A trenching machine (Ditch Witch) proved effective for cutting the ice. Ice blocks about 3 ft by 4 ft (1 m by 1.3 m) were formed and pushed along the slot to the river bank. There, each ice block was lifted with a mobile crane by means of a cable and T-bar inserted through a 6 inch (15 cm) diameter hole drilled in the centre of the block. The load bearing capacity of the ice was critical in determining the type and size of equipment that could operate safely on the ice. The project was conducted by the Prairie Region Oil Spill Containment and Recovery Advisory Committee and was financed by the Canadian Petroleum Association, Environment Canada, and the Petroleum Association for the Conservation of the Canadian Environment.

Countermeasures for Ice Covered Waters

“…This can be accomplished by: direct pumping through holes augured into the oil pool, potentially the least effective method [2]; the deployment of skimmers in trenches cut through the ice [17,18]; or possibly the deployment of rope mop skimmers under the ice [19]. This latter technique requires that free oil be available to the rope mop, and is most applicable to spills in late winter when new ice is slow to form or does not form at all.…”