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Hunt - Operational experience worldwide 
The response operation at sea was managed from the Coastguard Centre in Milford Haven 
by the Marine Pollution Control Unit (MPCU) [now the Counter Pollution and Response 
Branch of the Maritime and Coastguard Agency (MCA)]. A Joint Response Centre (JRC) was 
established in Milford Haven by the MPCU and the various local authorities who were in 
volved in the shoreline clean-up. Within the JRC a Technical Team and an Environment 
Team carried out assessments of shoreline contamination, environmental concerns and pri 
orities, on the basis of which appropriate clean-up techniques were selected. ITOPF was 
included in the Technical Team along with MPCU (MCA), the local county council, Texaco 
and the UK Petroleum Industry Association. 
Due to severe weather, little could be done to recover oil at sea using booms and skimmers 
during the initial stages. Throughout the entire response operation some 7,260 tonnes of oily 
waste was recovered at sea, with an estimated 700 - 1,400 tonnes of ‘pure oil’ contained 
within it. However, the conditions and oil type were particularly suitable for the use of disper 
sants, and as a result the MPCU made the decision to undertake a large-scale offshore aeri 
al spraying operation using their own fleet of six aircraft as well as the C-130 Hercules Aerial 
Dispersant Delivery System (‘ADDS Pack’) operated by Oil Spill Response Limited (OSRL). 
The spraying aircraft were controlled by an Air Coordinator onboard a spotter aircraft who 
would guide them towards the heaviest concentrations of oil using both visual observations 
and remote sensing. 
The use of a spotter aircraft was a particularly effective approach to the coordination of the 
operation since it allowed the geographic limits for dispersant use to be confirmed and 
helped each spraying run to focus on freshly released oil which was in thicker slicks and was 
more amenable to dispersion. Weathered and emulsified slicks were sprayed as a secondary 
priority. Once patches of oil had become too weathered to effectively disperse or too frag 
mented to target by the aircraft spraying would cease. 
In addition to the spotter aircraft, there was also an in-situ monitoring team operating from a 
boat to assess the effectiveness of the spraying operations. This team would survey the 
sprayed area between runs and would stop the operations once sufficient dispersant had 
been applied. A submerged flow-through Ultraviolet Fluorescence (UVF) Spectrometer was 
used to monitor oil concentrations in the sea to indicate effective dispersion. Although the 
UVF Spectrometer could not determine exactly how much oil was dispersed, by measuring 
the oil concentration before and after dispersant application, it could indicate qualitatively 
whether or not dispersed oil in the water column has increased significantly, and therefore 
whether or not the application was successful. 
The application of dispersants during the SEA EMPRESS spill is widely considered to have 
been highly effective amongst the spill response community, particularly as a result of the 
measures applied by MPCU for the purposes of coordinating and monitoring the operations. 
During the eight day aerial spraying operation a total of 446 tonnes of seven different types 
of dispersant was applied to the released oil, and on the basis of the real-time measurements 
of oil concentrations in the water column and subsequent mass balance calculations, it was 
estimated that approximately 37,500 tonnes of crude oil dispersed into the water column, 
either through natural dispersion or as a result of the application of dispersants. This equates 
to roughly 52 % of the 72,000 tonnes spilled from SEA EMPRESS, and therefore there is 
little doubt that the application of dispersants resulted in a dramatic reduction in the amount 
of oil that eventually stranded along the sensitive shorelines of Pembrokeshire. It is estimat 
ed that between around 5,000 tonnes and 15,000 tonnes of oil and emulsion came ashore 
along around 200 km of coastline, much of it within the Pembrokeshire National Park, but the 
situation could have been far more severe had dispersants not been applied. Bearing in mind 
that slicks were fairly rapidly forming water-in-oil emulsions in rough sea conditions, the 
quantity of oily waste to be recovered from the shoreline could potentially have been greater