Oil contamination of Nigeria's Ogoniland region could require one of the world's largest and longest decontamination programmes, according to a new report from the UN Environment Programme which says 50 years of oil operations have caused even worse pollution than previously feared.
Its 14-month scientific assessment of the Niger delta looked at 200 locations, surveyed 122km of pipeline, reviewed 500 medical records and engaged 23,000 people at local meetings.
It found severe contamination of soil and groundwater and 10 communities where drinking water is contaminated with hydrocarbons, seriously threatening public health.
UNEP executive director Achim Steiner said the report provides a scientific basis for a long-overdue remediation of Ogoniland.
"The oil industry has been a key sector of the Nigerian economy for over 50 years, but many Nigerians have paid a high price, as this assessment underlines," he said.
Soil and groundwater was tested at 69 sites ranging from 1,300m² at Ajeokpori-Akpajo to 79ha at Barabeedom-K.dere. 4,000 samples were analysed including 142 groundwater monitoring points and 780 soil boreholes.
The UNEP scientists found an 80mm layer of refined oil in an aquifer used for drinking wells and believed to have come from a spill six years ago. It recommended emergency action in Nisisioken Ogale as a prelude to long-term remediation which could last for 25-30 years.
The report says individually contaminated sites in Ogoniland could, with a concerted approach, be remediated within five years.
But it also found disastrous contamination of mangrove swamps which will take up to 30 years to cure. In just one area, Bodo West, an increase in artisanal refining since 2007 has seen 307,380m² - 10% of the total - lost.
The only remediation noted in the region was enhanced natural attenuation but this was judged not to have been effective.
It has only been used on the land surface area and was based on the assumption that, given factors like temperature and an underlying level of clay, hydrocarbons would not penetrate deeply. But in 49 cases they were found deeper than 5m.
Total petroleum hydrocarbons in groundwater were found in excess of 1g/l at five locations - the Nigerian standard is 600μg/l. Burning oil spills have left crusts of ash and tar, making remediation difficult and surface water all has layers of floating oil of various thicknesses.
UNEP recommends a five-year programme to tackle individual areas of contamination, together with a 30-year programme to tackle mangrove areas and swamplands. But it will be necessary to end all ongoing sources of contamination as a first step.
It says there should be three new institutions in Ogoniland - an environmental restoration authority, an environmental restoration fund, an integrated contaminated soil management centre and a centre of excellence in environmental restoration.
The report also recommends reform of government environmental regulation, monitoring and enforcement and improved practices by the oil industry.
