Chemical spills

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Context

The high level of media attention attracted by oil spills completely overshadows the existence of marine chemical pollution in citizens’ minds. Although most of the time this type of pollution is invisible, it nevertheless represents a significant pollution risk which is becoming increasingly present each day. Today, an estimated 37 million chemicals are used by man and 2,000 are regularly transported by sea. This transport method is currently on the rise: in 20 years, shipping of chemicals has been multiplied by 3.5. Predictions forecast that sea transport will reach 215 million tonnes of chemicals each year by 2015.

Number of accidents

Generally speaking, even although shipping is on the rise, the number of accidents involving hazardous and noxious substances (HNS) is falling. A statistical study conducted by REMPEC (Regional Marine Pollution Emergency Response Centre for the Mediterranean Sea) on 106 accidents in the Mediterranean shows that between 1994 and 2007 the number of cases dropped from 18 to 2 per year. This can be partly explained by the average ship age which has considerably diminished over the past years. In the above-mentioned study, 60% of boats involved in accidents were over 16 years old, while the world average in 2007 was 11.8 years old.

Evolution of the number of accidents between 1998 and 2007
in the Mediterranean involving hazardous and noxious substances
(Source: REMPEC)

Accident characteristics and products involved

According to statistics published by EMSA (European Maritime Safety Agency) on one hundred accidents in European waters between 1987 and 2006, the most frequent causes are fire and explosion (24%), followed by capsizing which is often due to difficult weather conditions (22%).

In 50% of cases, accidents do not result in a spill of the cargo. Furthermore, the problem of ship propulsion fuel is added to that of the chemicals. In this case, two distinct response efforts are carried out, as the response strategies will be closely linked to the behaviour of the products involved.

An investigation carried out in 2010 by Cedre on 218 well documented events having occurred worldwide since the early 20th century showed that the substances spilt in the greatest quantities are: iron ore (590,500 t), coal (107,200 t), phosphates (56,894 t), sulphuric acid (50,549 t), caustic soda (43,910 t), naphtha, (40,941 t), fertilisers (26,695 t) and methanol (25,000 t).

In terms of containers, listing lost containers would be a long and painstaking task. Moreover, nobody has worldwide data on this subject.

Potentially fatal accidents

Accidents involving chemicals can be fatal due to high risks of explosion and fire inherent to the transport of this type of cargo. Among the accidents which will remain in people’s memories due to their tragic outcome, we can make mention of the following:

In 1917, the cargo ship Mont Blanc, loaded with explosives, which exploded in the port of Halifax (Canada). 3,000 people were killed or reported missing, and 8,000 were injured.

In 1947, the cargo ship Grandcamp, which violently exploded in the port of Texas City (US) with its cargo of ammonium nitrate. The disaster caused the death of 600 people and injured over 3,000.

In 1974, the gas carrier Yuyo Maru N°10, which collided with the Pacific Alice in Tokyo Bay (Japan). The crash cracked its hull and its cargo of naphtha ignited. The subsequent fire and explosions were dreadful; 5 members of the Yuyo Maru N°10 crew were killed, and onboard the Pacific Alice the situation was catastrophic: all the seamen but one were killed.

Foodstuffs

The grounding of the bulk carrier Fenes off the south of Corsica in 1996 caused the spill of its cargo of wheat. The collision of the Allegra in the Channel resulted in the gradual release of almost 900 tonnes of palm nut oil in 1997.

Impressive yet temporary pollution

In the open sea, the effect of dilution plays a major role, minimising the impact of chemicals on the marine environment. Accidents occurring in relatively confined areas, such as harbours, bays or estuaries, result in greater pollution if they are not rapidly controlled. Most of the time, contamination resulting from such accidents is temporary. For example:

In 1995, the chemical tanker N°1 Chung Mu collided with the cargo ship cargo N°1 Chon Stone in the entrance channel to the port of Zhanjiang (China), releasing 200 tonnes of styrene monomer from its tanks. In addition to the hazards presented by this product for humans (neurotoxic vapours), its capacity to alter the organoleptic properties of fish and shellfish flesh was a concern. The pollution proved to be temporary, as 3 weeks after the spill, fishery products no longer presented a characteristic taste.

In 2005, the barge MGM 3030 containing 2,892 tonnes of sulphuric acid grounded in Chocolate Bay, an area of marshland in Texas. Leaks of the cargo resulted in a strong decrease in pH (as low as pH 2) around the barge but the environmental impact was short-lived.

Shellfish market in China
(Source: Cedre)

Increasingly well controlled yet costly accidents

Response to chemical spills long remained rudimentary, or even inexistent. Indeed, in many cases, it is materially impossible to take action (explosion, rapid dissolution in the open sea…). However, environmental aspects are now the focus of our society’s concerns and response actions are strongly encouraged by politicians and public opinion. Spill response is evolving in the right direction, but can prove extremely costly according to strategies adopted and equipment required.

Among the accidents having led to major mobilisation of response systems, we note the following:

In 1984, the chemical tanker Brigitta Montanari, which sank in waters 82 m deep in the Adriatic Sea with 1,300 tonnes of vinyl chloride monomer onboard. The wreck was brought up to a depth of 55 m to be towed underwater to a small sheltered bay where it was grounded. The cargo was then pumped to the surface and transferred onto another vessel.

In 2000, the chemical tanker Ievoli Sun, which, after a towing attempt, sank in the Channel in waters 70 m deep with a cargo of 3,998 tonnes of styrene, 1,027 tonnes of methyl ethyl ketone and 996 tonnes of isopropyl alcohol. Work on the wreck required the deployment of underwater wire-guided robots. The entire cargo of styrene, considered as a marine pollutant, was pumped out. The methyl ethyl ketone and isopropyl alcohol, which did not constitute a real hazard for the environment, underwent controlled release through holes drilled in the ship’s hull.

In 2007, the container ship MSC Napoli loaded with 42,000 tonnes of goods suffered structural failure at the entrance to the Channel. 103 containers fell into the water and 57 arrived on the shoreline. A system was set up to stop scavenging. Meanwhile, the ship was towed towards a sheltered bay on the English coast. The bunker fuel was pumped out and the containers still onboard were removed then treated on land. Once empty, the wreck of the MSC Napoli was cut up to be dismantled.

Recovery of containers from the holds of the MSC Napoli
(Courtesy of MCA)