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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  involved ­
  in  the  shoreline  clean-up.  Within  the  JRC  a  Technical  Team  and  an  Environment
Team  carried  out  assessments  of  shoreline  contamination,  environmental  concerns  and  priorities, ­
  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  dispersants, ­
  and  as  a  result  the  MPCU  made  the  decision  to  undertake  a  large-scale  offshore  aerial ­
  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  fragmented ­
  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  estimated ­
  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