IMPACTS ON CRITICAL INFRASTRUCTURE FOLLOWING THE MAY 2008 CHAITéN ERUPTION IN PATAGONIA

On 2 May 2008 a rhyolitic eruption from Chaitén volcano in southern Chile led to extensive ashfalls over >200,000 km² of Chile and Argentina. Lahars were also generated in drainages surrounding the volcano. Our team visited the affected region between 23 January and 12 February 2009 and assessed impacts to critical infrastructure.

Several high and low voltage electrical distribution networks suffered flashover damage to insulators and damage to lines from treefall, resulting in outages to some communities and prompting cleaning and insulator replacement programmes. The Futaleufú hydroelectric power dam (Argentina) received heavy ashfalls but these did not cause immediate damage. However, ash-induced flashovers on transformer insulators in the step-up yard disrupted electricity supply to the Argentinian national grid. Municipal water supplies in the towns of Chaitén and Futaleufú (Chile) and Esquel (Argentina) were disrupted by the eruption.

In Futaleufú, the original snowmelt-fed source was disconnected on a precautionary basis, and a groundwater-fed system developed. In Esquel, a timely and well-designed monitoring programme helped allay public fears about a metallic taste in the water supply, which remained continuous. Authorities did however experience other problems with the water supply as a consequence of the ashfall; suspended ash increased turbidity levels in the intake water and to prevent terminal disinfection from being compromised it was necessary to increase the chlorination dosage. In addition, residential cleanup operations came close to exhausting the town supply.

Ground transportation networks suffered disruption with ash reducing visibility both during the primary ashfall and as a result of remobilisation. Some bridges have been damaged or destroyed by lahars. Most electromagnetic transmission systems proved resilient to ashfall, at least in the short term. The only reported problems occurred when ash penetrated telecommunication devices causing failure to electronic componentary, also overloading of local exchanges due to excessive call traffic.