A £25,000 investigation is underway to assess the continuing impact and level of threat posed by an historic oil slick that blackened the beaches of Gorleston and Hopton more than 35 years ago.
Experts are combing a 4km stretch of beach, focusing on trenches that were exposed by severe erosion last year, in a bid to find out how much oil was buried under the beaches in 1978 and what to do with it today.
A spokesman for Great Yarmouth Borough Council, which has commissioned the survey, stressed that although the oil posed a low risk to human health, people were urged to avoid the area and keep their pets at a distance.
The thick deposits are the aftermath of the Eleni V shipping disaster - the worst marine oil slick to have hit the east coast.
The Greek oil tanker was sailing in thick fog when she was struck by the French bulk carrier Roseline six miles off Winterton spilling more than 5000 tonnes of oil along 35km of the east coast from Winterton to Aldeburgh
A £2m mop up operation was a race against time with wildlife and birds badly affected, the oil even reaching the seals huddled together on Scroby Sands.
Among other measures it saw boreholes drilled to sink oil well below popular tourist beaches thinking it was biodegradable and would disappear. However, now stretches of beach have been much depleted the substance has begun to resurface.
The spokesman added: 'Where washed up oil could not be accessed by machinery to be removed to landfill, oil was removed by hand and buried in trenches that had been dug at the back of beaches, which was an approved method of disposal at that time.
'There are no known maps indicating the exact location of the trenches. Last winter, easterly storms exposed five trenches on a relatively isolated part of the beach between Gorleston and Hopton, where the sand level has dropped in recent years due to erosion.
'Following discussions with the Environment Agency and other partners, the borough council has commissioned a specialist firm to drill test holes to determine the depth of the exposed trenches, as well as the depth and location of any other hitherto unexposed trenches.
'The firm's resultant report, expected to be finished in the spring, will include an accurate estimate of the location and volume of oil, plus an options appraisal of ways to deal with the oil and the potential costs.
'However, it is thought that no oil was buried on the most popular part of Gorleston beach, as there was good access for machinery. Furthermore the sand at this part of Gorleston has built up over the last few years, further burying any potential trenches.
'The tests cover a 4km stretch, centring around the trenches that were exposed last year.
'The £25,000 investigation is being part-funded with £7,000 from the Environment Agency, with the rest coming from the borough council.
'Ensuring that any oil is located, quantified and dealt with appropriately is important to reduce the risk of pollution as a result of oil washing backing into the sea, and to maintain a pleasant environment at these beautiful beaches, which bring millions of tourists to the borough every year.
Signs were erected last year and are in the process of being renewed, he added. Work started last week and is expected to be completed within the next couple of weeks.
At the time the heavy diesel was said to have a powerful smell that made people feel sick, attacked the throat and caused headaches. Although a boom was put across the harbour at Yarmouth it gave way and oil entered Breydon Water, the gateway to the Broads.
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