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Hunt - Operational experience worldwide 
was apparent that additional releases of the light crude oil were dispersing naturally with the 
strong wave action and there was no longer enough of a slick on the sea surface to warrant 
widespread spraying by that stage. Given the low persistence of Iranian Light crude oil and 
the high mixing energy in the damaged cargo tanks generated by the incessant heavy swell, 
it is considered likely that much of the spilled oil dispersed naturally. Hence dispersant appli 
cation simply accelerated this natural process, while further reducing the risk of floating slicks 
reaching the Indus River Delta mangroves. 
Shoreline contamination resulting from the TASMAN SPIRIT spill was relatively small scale 
considering the quantity of oil released. Oil came ashore along approximately 8-10 km of 
shoreline, much of it along Clifton Beach, a sandy recreational beach downwind of the casu 
alty and adjacent to the port. A shoreline clean-up operation was carried out along Clifton 
Beach and within the harbour, mainly using manual recovery techniques with local workers. 
Sections of the beach that had been heavily contaminated were tilled at low tide using agri 
cultural ploughs to accelerate the biodegradation of oil within the sediment. 
Overall the strategic decision to conduct large scale dispersant application in this case is 
considered to have been a successful one given the limited extent of spill-related environ 
mental and socio-economic impacts associated with such a large spill in a densely populated 
and environmentally sensitive area. Field surveys conducted after the incident showed little 
or no impact on mangroves, salt pans and other sensitive resources in the vicinity, and the 
geographical extent of shoreline oiling was limited to a ten-mile radius around the grounded 
tanker. In addition, there were very few reports of impacts of the oil on fisheries. 
Case Study: HEBEI SPIRIT (Republic of Korea 2007) 
A key consideration when planning the response to any oil spill is the ‘window of opportunity’ 
for a particular strategy, and this is particularly relevant for dispersant application. Once oil 
has been released at sea it begins to spread out, fragment and its properties change as a 
result of a variety of processes, collectively known as weathering. These processes act to 
reduce the amenability of the floating oil to dispersion since the loss of lighter components to 
evaporation results in an increased viscosity of the remaining oil, and the incorporation of 
droplets of seawater in the slicks with wave action can create a water-in-oil emulsion for 
some oil types, further increasing the viscosity. In addition, as the oil spreads out it becomes 
increasingly difficult to locate and target suitable slicks. Hence quick decision-making is fre 
quently necessary if an effective dispersant spraying operation is to be mounted. It is there 
fore advantageous to have considered the use of dispersants for a variety of different spill 
scenarios during the contingency planning stage, and a clear policy to have been formulated 
in advance, along with a detailed plan of action with logistical considerations taken into ac 
count. 
An incident that highlights the issues associated with the window of opportunity for disper 
sant application is the HEBEI SPIRIT spill in South Korea. On 7 th December 2007, the VLCC 
HEBEI SPIRIT (146,848 GT, built 1993), laden with 209,000 tonnes of four different Middle 
Eastern crude oils, was struck by a crane barge whilst at anchor off Taean on the west coast 
of South Korea. The barge broke free from its tow in poor weather, puncturing three port-side 
cargo tanks on the tanker. Despite mitigating efforts by the crew of HEBEI SPIRIT, approxi 
mately 10,900 tonnes of Iranian Heavy, Upper Zakum and Kuwait Export crude oils were 
released to the sea. 
The at-sea response was led by the Korea Coast Guard with support from the Korean Navy 
and Korea Ocean Environment Management (KOEM) with more than 100 vessels from these 
organisations involved, along with over 1,500 fishing boats. Dispersants were applied from 
vessels, from helicopters equipped with spray systems and small fixed-wing crop sprayers, 
although the extent of this operation is understood to have been relatively modest for a spill