Experts warn dam in Cameroon will collapse

Experts who have returned from examining a dam in Cameroon have warned that it could collapse in five years unless urgent action is taken.
In a report issued October 6 in Geneva, a team of U.N. experts who had just returned from visiting Lake Nyos in the country’s Northwest Province, said a breach of the dam there is “imminent,” and would likely happen by 2011. The team, led by Olaf Van Duin and Nisa Nurmohamed of the Netherlands, warned such a collapse could release up to 50 million cubic feet of water, affecting thousands of people in Cameroon and Nigeria.
The dam on Lake Nyos is a natural structure of volcanic rock. At its narrowest point it measures 40 metres high and 45 metres wide. Scientists have found that erosion has weakened the wall, and found holes and pockets in the upper layer, and water already passing through the lower section. There is also a risk of seismic activity in the region.
The Cameroon government denies there is any immediate threat, but the U.N. experts recommended it should begin a $15 million mitigation project to reduce the water level by 20 metres and then remove the dam wall.
Lake Nyos has been the scene of a catastrophic disaster in the relatively recent past. It lies on the flank of an inactive volcano on a pocket of magma, which leaks carbon dioxide into the waters. Consequently, the lake becomes saturated with the gas. In August 1986, the lake suddenly released a cloud of carbon dioxide, estimated at 1.6 million tonnes. The gas rushed down the valleys and suffocated up to 1,800 people in nearby villages and 3,500 livestock.
Scientists who studied the disaster decided that the catastrophe may have been caused by a landslide or by a volcanic eruption at the bed of the lake. Another possibility is that cool rainwater falling on one side of the lake triggered an imbalance, causing the reaction.
Subsequently engineers recommended that in order to avoid a future carbon dioxide eruption, five tubes be lowered into the lake to allow the gas to released to the surface, but so far only one has been built.
Source UN News, and Wikipedia (http://en.wikipedia.org)