Version1Page1of30July2012CaseStudy#001Title:PlanningandPreparedness–TheRiskAssessmentProcessIntroductionRiskassessmentformsanintegralaspectofmanyincidentmanagementphasesincludingplanning,preparednessandresponse.Planningandpreparednesswilltypicallyinvolveproactivestrategichazardandriskanalysis,whilstriskassessmentduringresponseismorelikelytobeadynamicprocessrequiringongoingreviewasconditionschange.Initssimplestformriskcanbedefinedastheseverityofaneventcombinedwiththelikelihoodofthateventoccurringunderadefinedsetofcircumstances.Thisprocessistypicallydevelopedfurthertoincludelikelynumbersthatmaybeaffected(includingsensitivepopulationgroupssuchastheyoung,elderlyandinfirm),doseresponsetotheagentsunderassessmentandexposureassessment,asdefinedwithintheWHOtoolkitforpublichealthriskassessment.ThefollowingUKeventillustrateshowsuchassessmentwasusedtoplanandmanageapotentiallyhazardousoperation.SummaryofEventThe“HappyLady,”agascarrieranchoredoffSpurnHeadintheHumberestuary,England,UKrequestedpermissiontovent40tonnesofethylenegasinordertofacilitaterepairs.Theshipcouldnotmovefurtheroffshoreduetohulldamageandfearsthatthehullcouldsplitinrougherwater.Ethyleneisacommonrawmaterialinthesyntheticorganicchemicalindustry.Itisshippedascompressedgas;underpressureandbelow10oCitexistsasliquefiedgas.Thegashasacharacteristicsweetodour.Itiscolourless,lighterthanair,extremelyflammableandcanformexplosivegas/airmixtures.Explosivelimitsarerelativelylow:2.7%-36.0%byvolumeinair.Itisofaloworderoftoxicityandvapoursarenotirritatingtotheeyesorupperrespiratorytract.Highconcentrationsmayleadtoanaestheticeffects.Ethylenecanactasasimpleasphyxiant,causingsuffocationbyloweringtheoxygencontentoftheairinconfinedareas.Itisnotclassifiedasahumancarcinogen.NoUKWorkplaceExposureLimitexists.Asaguidetooccupationalrisks,USstandardsareavalueof200ppm(over8hours).Nearbypopulationcentres,othershippingintheestuaryandmediainterestsuggestedpossiblerisksfromtheactivity.Ariskassessmentwasneededtoaddressthefactthatventingwouldtakeplaceoveranextendedperiod,inwhichconditionswouldbevariable.Plumemodellingwasusedtoidentifypotentialforgroundingofthegasandidentifytheradiusoftheexclusionzonetobeimposedaroundthevessel.Theresultsofthemodellingconfirmedthattherewasunlikelytobeanyrisktothepublicatthelevelspredictedbutthattherewasapotentialrisktothecrew.Repeatedmodellingandinterpretationthroughouttheprocessenabledassessmentofrisksuntilventingwascompleteandthevesselcouldenterportforrepairs.Version1Page2of30July2012NarrativeEarlyontheafternoonofMonday7thApril2008,theUKMaritimeandCoastguardAgency(MCA)contactedtheHealthProtectionAgency(HPA)regardingthe“HappyLady,”agascarrieranchoredoffSpurnHeadintheHumberestuary.Theshipownerhadrequestedpermissiontovent40tonnesofethyleneinordertocarryoutrepairs;thustheMCAsoughtadvicefromtheHPAoverthepotentialpublichealthrisk.Thedesignofthisshipprecludedanyattemptatship-to-shiptransfer.Assuchventingwouldbeundertakenovera3dayperiodbyintroducinghotairintothetankstoboiloffvapour,followedbybackfillingwithinertgas.Theshipcouldnotmovefurtheroffshoreduetoafractureofthehull.Inviewoftheflammableandpotentiallyharmfulnatureofethylene,undertakingtheactivityclosetoshoreposedapotentialrisktopublichealth,inrespectofpossibleexposureofresidentsandusersoftheestuary.Assuchitwasnecessarytoundertakeriskassessmentaspartoftheplanningproce...
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