Uncertainty about the safety of Milliken dam in Napa, California, has lead the city to authorise a 30% reduction of its storage capacity.
Holes will be bored into the dam’s concrete face to permanently lower the storage level of the reservoir, located in the hills above the Silverado hotel resort, to 4.8m below full. Authorities are confident that this will leave it better equipped to withstand a major earthquake.
The Napa city council has agreed to pay an engineering company US$74,000 to drill four to seven holes of 45cm and 61cm in the structure. The total cost of the operation is estimated at US$300,000 and is set to begin in late 2005.