Oil slicks have appeared again along the coast of Vung Tau city in southern Viet Nam in what has become an unexplained annual phenomenon.

On March 2 slicks covered 10km of the city's Thuy Van Beach, scaring people out of the water.

In the past several years oil slicks have appeared along the city's coast in March and April when south-westerly winds blow, affecting tourism and aquaculture.

Nguyen Xuan Manh, director of the Vung Tau Environmental Services and Urban Works Company, said it has become a practice for his company before March to be prepared with plastic bags, shovels, rakes, and workers to co-operate with resorts to clean up the oil.

The province has had difficulty in the past in treating the collected oil, with some companies assigned to the task illegally burying instead of burning the oil as regulated.

After the Ha Loc Co., Ltd. opened a toxic waste treatment plant three years ago it has been treating the oil collected from slicks free of charge. The company treats around 50 tonnes every year.

The slicks have caused severe damage to aquaculture and tourism.

Pham Xuan Son, head of Joint Venture Vietsovpetro's Science Research and Design Institute, said the slicks washing into the Vung Tau coast were of crude oil but were not Vietsovpetro's.

Every year when the oil appears in Vung Tau, the company takes samples for testing to compare with its own oil.

"The slicks are not caused because of oil pipe leakages, drilling or seepage while filling oil tankers since all those processes have stringent safety regulations," Son said.

Le Van Cuong, head of the province's Sub-department of Environmental Protection, said the phenomenon might be caused by ships that illegally discharge waste oil into the sea to reduce the cost of treating it properly.

But it was beyond the province's capability to track down such vessels, he said.

Satellite monitoring and photography could help identify such ships and drilling rigs, but the cost would be very high, he added.

VNS