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Roads & Highways || Driving conditions || Safety strategies || Drainages || Ash cleanup & removal ||
Visibility on roads is typically poor during and after an ash fall, and total darkness may result during a heavy ash fall. During such conditions vehicle headlights and brake lights are often ineffective and barely visible to other drivers, and driving may become difficult or impossible. After an ash fall, fast-moving vehicles will stir up ash along roads and create billowing ash clouds a few tens of meters tall.
For example, following an eruption of Mount St. Helens in Washington on 25 May 1980 that deposited 1-4 cm of fine ash within about 120 km of the volcano, hundreds of vehicle accidents were likely caused by such stirred-up ash. This description appeared in the newspaper Seattle-Post Intelligencer on 28 May:
"Brake lights could be faintly seen through the dust which rose 30 feet (9 m) above the freeway. Often, though, lights couldn't be seen, and all that could be heard was the tinkle of broken glass and the crunch of crumpled metal as cars from the rear headed into the ash clouds, and rammed vehicles already hidden in the clouds" (Blong, 1984, p. 291-292).
Ash deposits will absorb a considerable amount of water before being eroded and washed away. When ash on roads become wet, the mud-like mixture can cause vehicles to lose traction and drivers to lose control of steering. During such conditions, the braking ability of vehicles may be significantly reduced.
Dry ash also cause roads to be slippery.
Road markings covered
Ash deposits thicker than about 1 mm will obscure or completely cover markings on roads that identify lanes, road shoulders, direction of travel, and instructions to drivers (for example, stop or slow). When such road markings are not visible, drivers may become confused and disoriented.
Before ash is removed from roads, several actions can help reduce vehicle accidents and lower the amount of ash that is constantly being stirred up by moving vehicles. The following actions were taken in communities and for major highways in eastern Washington following an ash fall that deposited between 1 and 5 cm of ash from the 18 May 1980 eruption of Mount St. Helens:
- Close interstate highways to limit the likelihood of motorists becoming stranded before reaching their destination.
- Close roads in urban areas to facilitate clean up and prevent stirring up the ash.
- Limit the number of vehicles allowed on highways; for example, to one vehicle every five minutes.
- Impose short-term speed restrictions of 15-30 kilometers per hour or less (10-20 miles per hour).
- Advise motorists to travel only when really necessary.
- Organize slow-moving convoys spaced at 1.6 km (1 mile) intervals.
- In hardest-hit areas, suspend public transportation until streets and roads are cleared.
Drainages and waste-water systems
Ash was removed first from drainage ditches, Philippines
Ash fall may also result in the clogging of roadside ditches and culverts. During rainfall, poor or nonexistent drainage along a highway or road can cause erosion of the shoulder and road surface. During ash clean-up operations, prevent ash from accumulating in such drainages or entering underground waste-water or storm-drain systems.
Ash cleanup & removal from roads
Most communities and organizations tackle the ash cleanup of roads and highways using their available road-cleaning equipment and, sometimes, from the help of those not affected by ash fall. If ash is pushed to the side of the road instead of removed, wind and vehicle movement will cause it to stir or billow, creating clouds of ash for weeks or months.
Ash typically is removed from urban areas even for accumulations of only a few millimeters. A number of factors will influence the removal method employed, the ease with which ash can be removed, and the cost of any clean-up operation. These include ash thickness, grain-size, availability of equipment, and the degree of cooperation and assistance from residents.
|Removing ash from paved roads and urban streets
Modified from, FEMA, 1984
|Removing ash from paved or oiled roads that have
no curbs or sewers
Modified from, FEMA, 1984
|Removing ash from gravel roads
Modified from, FEMA, 1984
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Vehicles || damage || special maintenance ||
Damage to vehicles
Because volcanic ash consists of tiny pieces rock and volcanic glass, ash can infiltrate nearly every opening and abrade or scratch most surfaces, especially between moving parts of vehicles. Ash particles easily clog air-filtration systems, which can lead to overheating and engine failure. Small concentrations of ash particles inside an engine can cause extra engine wear. Even transmissions experience extra wear after ingesting minute ash particles.
Seals on hydraulic components may wear out faster than usual, and brakes and brake assemblies are especially vulnerable to abrasion and clogging from ash. Trucks used to transport ash to disposal sites and other vehicles subjected to heavy ash exposure may require constant brake attention.
Ash caught between windshields and wiper blades will scratch and permanently mark the windshield glass, and windows are susceptible to scratching each time they are raised, lowered, and cleaned. Corrosion of paintwork and exterior fittings may also result where ash is in contact with the exterior.
Strategies for reducing the effects of ash on machinery involve frequent oil changes, cleaning or replacing air filters often, using air pressure (< 30 lbs/in2) to blow ash from electrical equipment and other essential engine components (for example, alternator, starter, wiper motor, and radiator), and frequently cleaning vehicles with water to wash away the ash. During such cleanup, care should be taken to ensure the ash does not enter a waste-water or drain-water system.
The list below provides some protective measures for vehicles driven in ashy conditions based on the experience of the 18 May 1980 eruption of Mount St. Helens. Vehicle owners and operators are encouraged to obtain maintenance manuals and manufacturers' recommendations that may be available for operating vehicles in ashy or dusty conditions. For example, in June 1980 General Motors Corporation issued a public service announcement to drivers in ash fallout areas from the Mount St. Helens eruption.
|Suggested measures for reducing effects of ash to
Oil change and air filters
Modified from, FEMA, 1984
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Railways || damage || temporary shutdown ||
Rail transportation is less vulnerable to volcanic ash than roads and highways, with disruptions mainly caused by poor visibility and breathing problems for train crews. Moving trains will also stir up fallen ash, which can affect residents living near railway tracks and urban areas through which railway lines run.
Fine ash can enter engines and cause increased wear on all moving parts. Light rain on fallen ash may also lead to short-circuiting of signal equipment.
Disuptions caused by poor visibility and breathing problems for train crews, and potential damage to engines and other equipment, can result in the temporary shutdown of rail services or the delay in normal schedules. For example, ten trains in western Montana (USA) were shut down for nearly a day because of 1-2 mm of ash fall resulting from the eruption of Mount St. Helens volcano, 625 km to the west (Blong, 1984). The rail services were back to normal operations within 3 days, however.
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Airports || effects || mitigation strategies & cleanup ||
Worldwide, approximately 500 airports lie within 100 km of volcanoes that have erupted since 1900 AD. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes (Guffanti and others, 2008). Since 1980, five airports per year on average have been affected by volcanic activity. Ash falling on airports will affect runways, taxiways and aprons, buildings, ground services, electrical utilities, communication facilities, and airplanes parked on the ground. Also, electronically-activated badges used to gain entry to restricted areas may not permit access during power disruptions or if the badges become severely abraded by ash. Before these facilities and airplanes can return to normal service following an ash fall, the ash must be removed and cleaned from all surfaces, facilities, and airplanes.
See recent report, Volcanic hazards to airports, 2008.
Problems at airports include:
(a) difficult landing conditions due to reduced runway friction coefficient, especially when the ash is wet,
(b) loss of local visibility when ash on the ground is disturbed by engine exhausts during take off and landing,
(c) deposition of ash on hangars and parked aircraft, with structural loading considerably worsened if weight is added by precipitation absorbed by ash, and
(d) contaminated ground-support systems.
Mitigation and cleanup
A workshop, Impacts of Volcanic Ash on Airport Facilities, was convened 26-28 April 1993 in order to enhance aviation safety through the exchange of information about proper removal and containment of volcanic ash at airport facilities (Casadevall, 1993). Several common recommendations emerged during discussions in the four working groups. These recommendations have a direct practical bearing on ash and airport operations. Many of these were also included in the working group recommendations and considerations listed below.
Impacts of Volcanic Ash on Airport Facilities, Summary Recommendations:
- Make plans for dealing with ash fall and cleanup operations ahead of time, and make sure the plan is practiced, staff are trained, and the equipment works. The ash plan should be coordinated with airport response plans and regional emergency plans.
- Systems that provide water for cleanup, especially under pressure, are extremely useful and important in most situations.
- Move ash only once; ash is not snow, it won't melt and disappearpick ash disposal sites carefully (plan ahead).
- The right equipment is needed for cleanup, ranging from trucks to graders to brooms, plastic covers, and tape.
- Airplanes should be moved away from the airport before ash starts to fall.
- Do not start cleanup operations until the ash fall is over (except when buildings are threatened by overloading of roofs).
- In light ashy conditions, aircraft can land and take off, but flight crews should exercise proper care and procedures such as tow-in and tow-out from ramp areas.
- Ash can be slippery when wet; aircraft and ground vehicles need to exercise caution.
- Personal protection gear and logistical support is needed for people working on roofs, aircraft wings, and during ashy conditions. For example, filter masks, respirators, eye protection, hats or helmets, food and water, auxiliary lighting, and portable toilets to minimize walking traffic into airport buildings.
- Innovation is needed to identify solutions to problems that emerge.
During the workshop, four working groups met to address four topics key to airport facilities and identified several action items (see below).
|A 3.5-hour-long eruption of Mount Spurr on
18 August 1992 formed an eruption cloud that moved over the Anchorage
area and deposited 1-3 mm (1/16-1/4 in) of ash between 8:10 p.m. and 11:00
p.m. The ash fall led to the closure of Anchorage International Airport
(AIA), Elmendorf Air Force Base, and Merrill Field. Total cost of removing
the ash from the airports, including the cost of protecting and cleaning
aircraft caught on the ground is estimated between about $650,000 and
At AIA, crews found the best technique for removing ash from runways and taxiways involved four steps: (1) completely saturate the ash with water in order to "float it with large quantities of water" (photos, lower left and center); (2) sweep the water-saturated ash into windrows or berms using graders and runway sweepers (photo, lower right); (3) loading the ash onto trucks and then hauling the ash to a disposal site at the airport; and (4) with water trucks, flushing the areas that the graders and runway brooms had swept over. One runway was re-swept and flushed with water more than six times before it was considered safe for use by aircraft. For more about the effects on the Anchorage-area airports and cleanup operations, see testimonials in Casadevall, 1993.
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Aircraft || effects || safety measures || ash cleanup ||
From 1973 through 2000, about 100 encounters of aircraft with airborne volcanic ash have been documented (Guffanti and Miller, 2002). That number can be considered a minimum value, because not all encounter incidents are publicly reported. Aircraft have been damaged by eruptions ranging from small, recurring episodes (e.g., Etna, Italy, 2000) to very large, infrequent events (e.g., Pinatubo, Philippines, 1991). Severity of the encounters has ranged from minor (acrid odor in the cabin and electrostatic discharge on the windshield) to very grave (engine failure requiring in-flight restart of engines). Engine failures have occurred 150 to 600 miles from the volcanic sources. Fortunately, engine failure leading to crash has not occurred.
Life-threatening and costly damages can occur to aircraft that fly through an eruption cloud. Based on reported damages from ash encounters, the hazard posed to aircraft may extend 2,000 km (3,200 miles) from an erupting volcano. The actual effects of ash on aircraft depend on several factors, including the concentration of volcanic ash and gas aerosols in the cloud, the length of time the aircraft actually spends in the cloud, and the actions taken by the pilots while in the eruption cloud.
Numerous instances of jet aircraft flying into volcanic ash clouds have demonstrated the serious damage that can be sustained. Ash particles are angular fragments having the hardness of a pocket-knife blade and, upon impact with aircraft traveling at speeds of several hundred knots, cause abrasion damage to forward-facing surfaces, including windscreens, fuselage surfaces, and compressor fan blades. Moreover, the melting temperature of the glassy silicate rock material that comprises an ash cloud is lower than the operating temperatures of modern jet engines; consequently, ingested ash particles can melt and then accumulate as re-solidified deposits in the engine. The overall result of an aircraft's flying into an ash cloud can be degraded engine performance (including flame out), loss of visibility, and failure of critical navigational and operational instruments.
Experimental tests (Dunn and Wade, 1994) determined the following mechanisms that can affect aircraft performance due to exposure to a volcanic ash cloud:
(a) Deposition of material on hot-section components.
(b) Erosion of compressor blades and rotor-path components.
(c) Blockage of fuel nozzles and cooling passages.
(d) Contamination of the oil system and bleed-air supply.
(e) Opacity of windscreen and landing lights.
(f) Contamination of electronics.
(g) Erosion of antenna surfaces.
(h) Plugging of the pitot-static system which indicates the airspeed of the aircraft.
An ash cloud eventually dissipates in the atmosphere, and ash concentrations drop. However, the threshold concentration at which ash poses no harm to aircraft is not known, and indeed, may never fully be characterized for all situations involving aircraft. It is usually assumed that ash identifiable on satellite images continues to present a hazard to aircraft. Accordingly, the consensus of the aviation community is that if an ash cloud can be discerned, it should be avoided.(Guffanti and Miller, 2002).
Flight crews and dispatchers
Complete avoidance of volcanic ash by aircraft and the quick exit of an eruption cloud if ash is encountered are the only courses of action for flight crews and dispatchers that guarantees flight safety. Updated information about ways to ensure safe operations and minimize damage to an aircraft during a volcanic-ash encounter is available from Aero, Advances in Volcanic Ash Avoidance and Recovery, (No. 9, 1999) a quarterly magazine published by Boeing Commercial Airplane Group.
International Cooperation and Communication
Keeping aircraft away from eruption clouds involves international cooperation and communication between volcanologists, meteorologists, airline dispatchers and pilots, and government aviation and meteorologic organizations. Since the early 1990s new procedures and systems have been devised to disseminate quickly and widely information about (1) volcano status, especially new activity that includes eruption columns and downwind clouds of ash; (2) forecasts of eruption cloud movement; and (3) pilot reports regarding possible and actual eruption clouds. Because the ash hazard to aircraft is greatest within the first few hours following an eruption, the speed of notification between all links in the chain of communication is critical.
Procedures handbook. Operational procedures for disseminating such information is identified in a report by the International Airways Volcano Watch (IAVW) under the auspices of the International Civil Aviation Organization (ICAO), Handbook on the international airways volcano watch (IAVW)operational procedures and contact list (second edition, 2004), available in pdf.
Volcanic Ash Advisory Centers. As a key part of the IAVW, in 1995 nine regional Volcanic Ash Advisory Centers (VAAC) were established around the world under ICAO auspices to advise Meteorological Watch Offices on the issuance of volcanic ash warnings to aircraft. The VAACs have been specifically tasked with the detection, tracking, and forecasting of the movement of eruption clouds within their respective areas of responsibility. See VAACs and messages.
Pilot Reports. Verbal and written pilot reports are critical for identifying the airspace where volcanic ash or sulfur aerosols are located at a specific time and also where ash is not located. Verbal pilot reports provided to the air control center are critical for informing other pilots and dispatchers of ash-contaminated airspace. Written pilot reports prepared after the flight has ended are also important to help scientists improve their forecasts of eruption cloud movement.
Each of the major airframe and engine manufacturers has developed operational and maintenance related procedures for dealing with volcanic ash. These may be found in the appropriate Flight Crew Operating Manuals (FCOM) and Aircraft Maintenance Manuals (AMM). Interested parties are urged to consult the appropriate manuals for their respective operational needs. A number of manufacturers' suggested procedures are derived from the Aerospace Industries Association Volcanic Ash Committee (Casadevall, 1993).
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Casadevall, T.J., ed., 1994, Volcanic ash and aviation safety: Proceedings of the first international symposium on volcanic ash and aviation safety, Seattle, Washington, July, 1991: U.S. Geological Survey Bulletin 2047, 450 p.
Casadevall, T.J., and Krohn, M.D., 1995, Effects of the 1992 Crater Peak eruptions on airports and aviation operations in the United States and Canada, in Keith, T.E.C., ed., The 1992 eruptions of Crater Peak vent, Mount Spurr volcano, Alaska: U.S. Geological Survey Bulletin 2139, p. 205-220.
Dunn, M. G., and Wade, D. P., 1994, Influence of Volcanic Ash Clouds on Gas Turbine Engines, in Casadevall, T. J. (ed.). "Volcanic Ash and Aviation Safety - Proceedings of the First International Symposium on Volcanic Ash and Aviation Safety" U.S. Geological Survey Bulletin 2047, p. 107-118.
Gibson, N.W., 1999, Trip report to Quito, Ecuador, November 9-12, 1999: unpublished report, 3 p.
Guffanti, M., Casadevall, T.J., and Budding, K., 2010, Encounters of aircraft with volcanic ash clouds; A compilation of known incidents, 1953-2009: U.S. Geological Survey Data Series 545, ver. 1.0, 12 p., plus 4 appendixes including the compilation database, available only at http://pubs.usgs.gov/ds/545
Guffanti, M., Mayberry, G.C., Casadevall, T.J., and Wunderman, R., 2008, Volcanic Hazards to airports, 2008, Natural Hazards, Special Issue on Aviation Hazards from Volcanoes edited by Fred Prata and Andrew Tupper, DOI:10.1007/s11069-008-9254-2.
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