Volcanic ash impacts on critical infrastructure Thomas M. Wilson a,⇑ , Carol Stewart b , Victoria Sword-Daniels c , Graham S. Leonard b , David M. Johnston b , Jim W. Cole a , Johnny Wardman a , Grant Wilson a , Scott T. Barnard a a Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand b Joint Centre for Disaster Research, Massey University and GNS Science, P.O. Box 756, Wellington, New Zealand c Department of Civil, Environmental and Geomatic Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom article info Article history: Available online xxxx Keywords: Volcanic risk Electricity supplies Water supplies Wastewater Transport Telecommunications abstract Volcanic eruptions can produce a wide range of hazards. Although phenomena such as pyroclastic flows and surges, sector collapses, lahars and ballistic blocks are the most destructive and dangerous, volcanic ash is by far the most widely distributed eruption product. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation and primary production can lead to significant societal impacts. Even relatively small eruptions can cause widespread disruption, damage and economic loss. Volcanic eruptions are, in general, infrequent and somewhat exotic occurrences, and consequently in many parts of the world, the management of critical infrastructure during volcanic crises can be improved with greater knowledge of the likely impacts. This article presents an overview of volcanic ash impacts on critical infrastructure, other than aviation and fuel supply, illustrated by findings from impact assessment reconnaissance trips carried out to a wide range of locations worldwide by our inter- national research group and local collaborators. ‘Critical infrastructure’ includes those assets, frequently taken for granted, which are essential for the functioning of a society and economy. Electricity networks are very vulnerable to disruption from volcanic ash falls. This is particularly the case when fine ash is erupted because it has a greater tendency to adhere to line and substation insula- tors, where it can cause flashover (unintended electrical discharge) which can in turn cause widespread and disruptive outages. Weather conditions are a major determinant of flashover risk. Dry ash is not con- ductive, and heavy rain will wash ash from insulators, but light rain/mist will mobilise readily-soluble salts on the surface of the ash grains and lower the ash layer’s resistivity. Wet ash is also heavier than dry ash, increasing the risk of line breakage or tower/pole collapse. Particular issues for water supply managers include: monitoring turbidity levels in raw water intakes, and if necessary increasing chlorina- tion to compensate for higher turbidity; managing water demand; and communicating monitoring results with the public to allay fears of contamination. Ash can cause major damage to wastewater dis- posal systems. Ash deposited onto impervious surfaces such as roads and car parks is very easily washed into storm drains, where it can form intractable masses and lead to long-term flooding problems. It can also enter wastewater treatment plants (WWTPs), both through sewer lines and by direct fallout. Damage to modern WWTPs can run into millions of dollars. Ash falls reduce visibility creating hazards for ground transportation. Dry ash is also readily remobilised by vehicle traffic and wind, and dry and wet ash depos- its will reduce traction on paved surfaces, including airport runways. Ash cleanup from road and airports is commonly necessary, but the large volumes make it logistically challenging. Vehicles are vulnerable to ash; it will clog filters and brake systems and abrade moving parts within engines. Lastly, modern tele- communications networks appear to be relatively resilient to volcanic ash fall. Signal attenuation and interference during ash falls has not been reported in eruptions over the past 20 years, with the exception of interference from ash plume-generated lightning. However, some telecommunications equipment is vulnerable to airborne ash, in particular heating, ventilation and air-conditioning (HVAC) systems which may become blocked from ash ingestion leading to overheating. 1474-7065/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.pce.2011.06.006 ⇑ Corresponding author. Tel.: +64 3 364 2987x45511; fax: +64 3 364 2967. E-mail addresses: thomas.wilson@canterbury.ac.nz (T.M. Wilson), stewart.carol@xtra.co.nz (C. Stewart), victoria.sword-daniels.09@ucl.ac.uk (V. Sword-Daniels), g.leonard@gns.cri.nz (G.S. Leonard), david.johnston@gns.cri.nz (D.M. Johnston), jim.cole@canterbury.ac.nz (J.W. Cole), john.wardman@pg.canterbury.ac.nz (J. Wardman), grant.wilson@pg.canterbury.ac.nz (G. Wilson), scott.barnard@canterbury.ac.nz (S.T. Barnard). Physics and Chemistry of the Earth xxx (2011) xxx–xxx Contents lists available at ScienceDirect Physics and Chemistry of the Earth journal homepage: www.elsevier.com/locate/pce Please cite this article in press as: Wilson, T.M., et al. Volcanic ash impacts on critical infrastructure. J. Phys. Chem. Earth (2011), doi:10.1016/ j.pce.2011.06.006