_Fears of massive oil spill and ecological disaster grow as Tasman Spirit tanker, which ran aground on July 27, cracks in rough seas_
By *Kaleem Omar*, Pakistan’s premiere investigative journalist.
What was being feared for days finally happened on Thursday when the single-hull tanker Tasmin Spirit, which ran aground near the mouth of Karachi harbour in heavy monsoon storms three weeks ago, broke in two. Oil had already been spilling from the tanker for several days. On Wednesday a big crack developed in the hull, spilling thousands of tons of crude oil into the sea. Karachi Port Trust officials feared the crack could trigger an explosion and the crew was evacuated. Efforts to retrieve more oil from the tanker were also abandoned.
The Tasman Spirit is a Greek vessel chartered by the state-owned Pakistan National Shipping Corporation (PNSC) to carry crude oil to Pakistan. Three attempts were made to tow the tanker away before the hull cracked on Wednesday and oil began spilling into the sea. A growing slick of oil washed ashore along Clifton beach and other Karachi beaches, bringing toxic fumes and hundreds of dead fish, sea birds and turtles. More than 1,000 policemen, equipped with masks, were deployed to close the seafront. Around 10 miles of beach was closed, and many residents of Seaview were moved to safer locations.
It was not immediately clear how much oil was still on board the Tasmin Spirit. According to one report, the tanker was carrying 73,854 tons of US crude for the state-owned Pakistan Refinery Limited (PRL). The report said that by Thursday, 60,627 tons of oil had been salvaged, leaving 13,227 tons on board. The report added that KPT officials had declined to say how much oil had been spilled.
But another report said that the tanker was carrying 67,500 tons of Iranian crude. The report quoted port officials as saying that salvage experts had managed to retrieve some of the oil, but that more than 40,000 tons remained on board. The report said that if the rest seeped into the sea, it would become one of the world’s worst oil spills and could lead to an ecological disaster.
When the Exxon Valdez ran aground off Alaska in 1989, it spilled 38,800 tons of crude oil into Prince William Sound and it took many years for the area to recover. Exxon has so far spent $ 2 billion on clean-up operations, which are still continuing even some 14 years after the disaster.
To add to the confusion, a third report said the Tasman Spirit was carrying 67,000 tons of crude oil, of which about 20,000 tons had been salvaged, leaving 47,000 tons still on board. The report added that 12,000 tons of crude had already spilled into the sea before the tanker broke in two on Thursday. If this version is to be believed, about 35,000 tons of oil was still on board when the tanker broke up.
Perhaps the most authoritative account to date came from the London-based International Tanker Owners Pollution Federation (ITOPF). In a report dated Wednesday, August 13, ITOPF said the vessel was carrying 67,000 tons of Iranian crude oil for PRL when it ran aground on July 27. The report said a number of tanks were breached and oil began leaking from the vessel intermittently and at a modest rate.
The report said ITOPF was notified of the spill by the vessel’s P&I insurer and the Karachi Port Trust on the morning it occurred. First reports did not indicate a serious pollution incident and ITOPF was initially required to remain on standby and “monitor the situation from London.” As the situation deteriorated, ITOPF’s presence in Karachi was requested by the P&I Club on behalf of the tanker owner and Dr Karen Purnell, an ITOPF official, arrived on site on August 10 – two weeks after the incident occurred. The question is: why wasn’t the ITOPF’s presence requested earlier?
By August 10, according to the ITOPF report, a total of 13,000 tons of oil had been removed from the damaged tanks by lightering operations, but oil continued to spill periodically as attempts to plug leaks failed and other operational difficulties arose.
According to the ITOPF report, the prevailing swell and safety concerns hampered subsequent lightering and salvage efforts and the tanker began to break up on Wednesday, August 13, at which time the lightering operation was suspended. As a result of further ruptures in the forward tanks, the rate of oil leakage increased.
Referring to the resources at risk due to the oil spill, the ITOPF report noted: “There are popular beaches in the vicinity of Karachi. To the south of the grounding site, salt ponds and well-developed mangrove forests are present. The Karachi coastline and near-shore waters are also a rich source of fishing. Within the port of Karachi there are shipyard facilities and sea water intakes potentially sensitive to oil contamination.”
The report said ITOPF has carried out repeated surveys of the port area, the nearby Oyster Islands (popularly known as Oyster Rocks), and sandy beaches in and around Karachi. Mangrove areas have also been examined. The report said a continuous film of rainbow sheen was observed inside the harbour. Bands of oil were also observed on the hulls of a number of container vessels and other merchant ships in the vicinity and the harbour wall was stained in places.
In what to some may seem like an unduly optimistic assessment, the report added: “Overall, the impact of spilled oil has been moderate, partly reflecting the fact that the crude oil in question is light with a pronounced tendency to evaporate and disperse naturally.” Even if this assessment turns out to be correct, it still leaves open the possibility of a much greater impact on the coast’s ecology and environment from continuing oil spills.
The ITOPF report notes that booms and tugs were deployed by the Karachi Port Trust during the initial stages of the incident, but owing to the heavy sea swell and damage caused to some of the response vessels, these measures were of limited effect.
The report said: “As the seriousness of the incident escalated and on the advice of ITOPF, the P&I Club and the tanker owner mobilsed response equipment and personnel from Oil Spill Response Limited (OSRL) in Southampton, UK to supplement the resources available to the Karachi Port Trust. A range of equipment and specialist oil spill response personnel have been dispatched from OSRL and from East Asia Response Limited in Singapore so as to improve the capability for dealing with oil affecting coastal waters and shorelines.”
ITOPF said that “the main strategy agreed with Pakistani authorities for meeting the threat of a sudden major release from the casualty is the aerial application of dispersant.” At a press conference on Friday, KPT officials said that dispersant had been sprayed aerially around the site of the incident, using a Pakistani aircraft. They said the aircraft due from Singapore for dispersant spraying operations was still awaited.
Dispersants are a group of chemicals designed to be sprayed onto oil slicks, to accelerate the process of natural dispersion. Spraying dispersants may be the only means of removing oil from the sea surface, particularly when mechanical recovery is not possible. Their use is intended to minimize the damage caused by floating oil, for example to birds or sensitive shorelines.
However, in common with all oil spill response options, the use of dispersants has its limitations and should be carefully controlled, depending upon national regulations governing the use of these chemicals. Does Pakistan have such regulations of its own, or does it follow the regulations laid down by other countries or international bodies?
Natural dispersion of an oil slick occurs when waves and other turbulence at the sea surface cause all or part of the sea slick to break up into droplets and enter into the water column. The addition of dispersants is intended to accelerate this process.
Dispersants have two main components: a surfactant and a solvent. Surfactants are molecules which have an affinity for two distinct liquids which do not mix, acting as an interface between them. A part of the surfactant molecule used in dispersants has an attraction to oil (i.e., it is oleophilic), while another part has an affiliation for water (i.e., it is hydrophilic). Common washing-up liquid is another example of a product that contains surfactants.
When a dispersant is sprayed onto an oil slick, the interfacial tension between the oil and water is reduced, promoting the formation of finely dispersed oil droplets. These droplets will be of varying size and although the larger ones may rise back to the surface some will remain in suspension. If dispersion is successful, a characteristic plume will spread slowly down from the water surface a few minutes after treatment.
However, the effective distribution of surfactant throughout the oil is crucial to the success of the process. To achieve the required distribution, most dispersants contain a suitable solvent which allows the dispersant to penetrate into the slick and acts as a carrier for the surfactant.
Dispersants have very little effect on very viscous, floating oils, as they tend to run off the oil into the water before the solvent can penetrate. As a general rule, dispersants are capable of dispersing most liquid oils and emulsions with viscosities of less than 2,000 centistokes, equivalent to a medium fuel oil at 10-20 degrees Centigrade. They are unsuitable for dealing with emulsions (mousses) or oils which have a pour point near to or above that of the ambient temperature. Even those oils which can be dispersed initially become resistant after a period of time as the viscosity increases as a result of evaporation and emulsification.
For a particular oil, the time available before dispersant stops being effective depends upon such factors as sea state and temperature but is unlikely to be longer than a day or two. Dispersants can, however, be more effective with viscous oils on shorelines because the contact time may be prolonged, allowing better penetration of the dispersant into the oil.
It remains to be seen just how effective dispersant spraying will be in accelerating the natural dispersion of the oil spilling from Tasman Spirit. Minimising damage to the ecology of Karachi’s coastline could depend on how well the chemical dispersants work in this particular case.