The Los Alfaques disaster was caused by the explosion of a road tanker near a holiday campsite on 11 July 1978 in Alcanar, Spain. The exploding tanker, which was carrying 23 tons of highly flammable liquefied propylene, killed 215 people and severely burned 200 more. Several individuals from the company that owned the vehicle were prosecuted for criminal negligence. The disaster resulted in new legislation in Spain, restricting the transit of vehicles carrying dangerous cargo through populated areas to night time only. Most of the victims were on holiday from West Germany and some other European countries, and who were staying at the Los Alfaques seaside campground. The site, which is located at km 159 on the N-340 national road, is 2 kilometres (1.2 mi) south of the town of Sant Carles de la Ràpita.
Background The campsite of Los Alfaques (Spanish for "the sandbanks") is triangular-shaped and wedged between the beach and the N-340 coastal national road. It is about 2 km (1.2 mi) south of the nearest township, Sant Carles de la Ràpita, although it belongs to the territory of the Alcanar municipality. When the accident occurred, it was 200 m (656 ft) in length and 10,000 m2 (107,600 sq ft) in area. From north to south, it tapered from about 100 m (330 ft) down to 30 m (98 ft) wide. Separating the campsite from the road was a brick wall with a concrete foundation. The campsite's legal capacity was 260 people. However, on the day of the disaster, some 800 people were staying on the original grounds and on two new undeclared extensions; luckily, not all occupants were at the premises at the time. The tanker involved in the explosion consisted of a Pegaso tractor unit and a Fruehauf tank trailer. It was owned by Cisternas Reunidas S.A. and on the day of the disaster was driven by 50-year-old Francisco Imbernón Villena. The trailer was manufactured in 1973. Its maximum capacity was 45 m3 (1,589 cu ft) with a maximum allowed mass of 19.35 metric tons (at 8 bar and 4 °C (39 °F)).
Events
Loading and departure At 10:15 am, the driver arrived at the state-owned ENPETROL refinery, located at La Pobla de Mafumet, 9 km (5.6 mi) north of Tarragona, to be loaded with liquefied propylene for another state-owned company, Paular (now Repsol) in Puertollano. At 12:05 pm the fully-laden tanker left the refinery carrying 23.47 metric tons (25.87 short tons) of propylene, which was more than 4 tons over the maximum design load for the tanker (i.e., 19.35 t (21.33 short tons)). Thus, the tank was nearly hydraulically full of liquid, with minimal ullage space. The tanker drivers were expected to take the smaller N-340 national road instead of the A-7. In the late 1970s, the N-340 was still a narrow and winding coastal road that passed directly through several densely populated urban areas.
Explosion By 2:35 pm the tanker was driving past the Los Alfaques campsite, after travelling 102 km (63 mi) from the ENPETROL refinery. The time is known because the driver's watch – which was found still attached to his burnt wrist – had stopped at 2:36 pm. The tightly packed campsite was crowded with nearly 1,000 visitors, many from West Germany, in caravans and tents. During the journey, solar radiation and ambient temperature heated the liquefied gas. Under normal circumstances, the presence of ullage gas vapours would have meant an increase in pressure well within the mechanical limits of the tank. However, the tank was hydraulically full, which meant that the liquid had no room left to thermally expand. This resulted in the tank walls being stressed over their design capacity. According to some reports from surviving witnesses, the tanker was already leaking liquefied gas while passing by the campsite. Some witnesses thought they heard a loud bang that preceded the leak. The bang might have been caused by a blown tire, which caused the tanker to swerve and crash into the wall separating the campsite from the roadside (possibly overturning in the process). Others argue that there was no mechanical failure or traffic accident before the loss of containment, with the overstressed pressure vessel failing at a weak point. Within seconds, highly flammable propylene started flashing out of the ruptured tank and formed a white cloud that drifted into the campsite and towards a discothèque to the northeast. According to some reports, numerous intrigued campers approached the cloud with curiosity as it continued to spread. Eventually it became so dense that many were unable to see the tanker. Within moments of the cloud reaching the discothèque, it ignited into a flash fire that quickly returned to the source of the leak, thus causing the weakened tanker to explode. This generated a massive boiling-liquid expanding-vapour explosion (BLEVE), whereby the entire content of the tank car vaporized and burnt almost instantly in a fireball with a diameter estimated at between 40 and 60 m (130 and 200 ft) and 180 m (590 ft), resulting in tremendous levels of thermal radiation as well as a significant blast wave. Other reports suggest that external fires did not contribute to the onset of the BLEVE, with the pressure vessel having BLEVEd as a consequence of the tank walls being weakened by the thermal expansion of the liquid propylene, and the resulting expanding-vapour cloud catching fire only moments after its release. The fire destroyed everything – cars, trailers and buildings – within a 90 m (300 ft) radius and charred everything within a 300 m (980 ft) radius, gutting over 90% of the main camping area. The 400 m2 (4,310 sq ft) discothèque to the northeast, which was later determined to be the likely source of the ignition, was also razed, killing all the staff members inside. Additionally, 34 vehicles and 21 tents were burnt out, a restaurant partially collapsed, and the tank trailer was broken into four main pieces (two sets of wheels and two sections of the pressure vessel). The blast effects of the BLEVE were comparatively minor. There was at least one secondary confined explosion inside the discothèque buildings. The tanker tractor was broken into four pieces. Two-thirds of the tank pressure vessel flew northwest, landed about 150 m (490 ft) away and then slid, coming to rest against the wall of a restaurant, 300 m (980 ft) from the starting point. The middle section was flung about 100 m (330 ft) into the campsite.
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