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8/8/2019 Joint Health and Safety Committee Report on B.C. Place Stadium roof
1/82
InvestigationReport: BCPlaceRoofDeflationIncidentof
January5,2007
CompletedbytheInvestigationSubcommittee
SubmittedbytheBCPlaceJointHealthandSafetyCommittee
December21,2007
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ThisreportsprincipalauthorsaretheInvestigationSubcommitteeconsistingof:
JimHughes,CSP
JackieIng
JamesSwank
Thisreportwasreviewed,finalizedandsubmittedbytheBCPlaceJointHealth&Safety
Committee.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20071
TableofContents
ExecutiveSummary............................................................................................................. 3
IntroductionandOverview................................................................................................. 6
SequenceofEvents............................................................................................................. 8
CommentaryonSequenceofEvents................................................................................ 16
EventAnalysisandDiscussion .......................................................................................... 17
Weather ........................................................................................................................ 17
RoofLoading ................................................................................................................. 19
RoofFabric .................................................................................................................... 28
PressureExcursion ........................................................................................................ 28
Equipment..................................................................................................................... 34
CrisisIdentificationandManagement.......................................................................... 36
Policies,ProceduresandTraining ................................................................................. 38
CultureIssues ................................................................................................................ 41
CausalAnalysisMethodologies ........................................................................................ 42
RootCause .................................................................................................................... 51
DirectCause#1 ............................................................................................................. 52
DirectCause#2 ............................................................................................................. 52
Conclusion ......................................................................................................................... 54
Recommendations ............................................................................................................ 54
Appendices........................................................................................................................ 57
AppendixA RoofSupportPressureControlSystemsDescription .......................... 58
AppendixBBCPlaceRoofLoadingCalculations .................................................... 61
AppendixCRoofSupportSnowMeltSystem ........................................................ 67
AppendixD InvertedPanelLoadingCalculations.................................................... 69
AppendixE WeatherData ....................................................................................... 72
AppendixFEmergencySnowMeltProcedures,Nov15,2006 .............................. 76
AppendixGGeigerEngineersReportData,Sept14,2007,#207813 ................... 79
AppendixHListingofPhotographsandVideoClips,inCDformat ........................ 80
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20072
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20073
Executive Summary
Aftersustainingdamagetoawesttriangleroofpanel,thebuildingareaunderthedome
ofB.C.Placewassafelyevacuated,andthentheroofofBCPlacewassafelydeflatedina
controlledmanneratabout12:49pmonJanuary5,2007. Therewasnoinjuryasresult
ofthedeflation.
AttherequestofBCPlaceManagement,acomprehensiveinvestigationwasconducted
bymembersoftheJointHealth&SafetyCommitteeguidedbyanexperienced,external,
OHSConsultant. Theinvestigationsubcommitteehadthecompletecooperationof
buildingmanagement,union,staffandcontractors. Thisinvestigationteamalsoworked
closelywithKrisP.Hamilton,P.ENG,ofGeigerEngineering,thefirmthatdesignedthe
stadiumroof.
Theinvestigationisbasedonfactualdataandinformationandeventsleadinguptothe
deflation. Thepurposeofthisinvestigationwastofindfactsanduncoverrootcauses
thatweredirectlyresponsiblefortheevent,nottoassignblames,orfingerpoint.
Recommendationsinthisreportaimtopreventsimilarincidentsfromhappeninginthe
future.
Bypiecingalltheinformationtogether,thisreportpresentsapictureofwhattookplace
andthesequenceofeventsleadinguptothedeflation. Reconstructionofthedays
eventswerebasedonanumberofinformationsourcesincludingeyewitnessaccounts
boththroughinterviewsandwrittenreports,weatherreports,internalrecordsand
charts,newsmedia,inspectorsandprivateindividualsvideofootageandphotographs,
and
engineers
testing,
findings
and
preliminary
reports.
Thisreportgoesdeeperthansimplyrecordingthestepsoftheevent. WhiletheGeiger
Engineersreportcoverstheengineeringtechnicalaspectsoftheincident,the
InvestigationSubcommitteeexaminedabroadrangeofcausalfactorsthatwere
identifiedduringtheanalysisphaseofinvestigation. Inadditiontodealingwithmany
complextechnicalaspectsoftheevent,thesubcommitteealsolookedcloselyintothe
operationalside. BoththeEngineersreportandthisinvestigationreporttaken
together,addressthecompletescopeoftheroofdeflationincident.
EventDescription
Simplystated,heatandthenumberoffanscirculatingairattheroofwerenot
increased,whensnowwasimminent,norweretheyincreasedwhensnowwas
observed. Asthesnowaccumulated,unchecked,theroofbecameheavilyloadedtothe
pointitstartedtoloseitsshape.Thechangeintheroofwasnotnoticeduntilthemain
speakerclusterwasobservedtobeverylow,andthecenteroftheroofappearedvery
flatontheinside.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20074
Atthispointbuildingpersonnelreactedbyincreasingbuildingpressureandactivating
thesnowmeltroofheatingsystem. Theroofshapedidnotappeartoberecoveringas
expectedbecausetherequestedcomputersystemspressuresettingwasconflictingwith
thebuildingspneumaticcontrolsystems.Thiscausedthereliefventstobleedoffthe
intendedpressureincrease. Atthispointthepressuresetpointonthepneumatic
controlsystemwasincreased. Whenthesystemsfinallyreactedtothecommands,the
combinationofsetpointincreaseandotherfactorscausedabriefpressureexcursion,
substantiallyabovetherequestedpressuresetpoint,whichquicklybutbrieflyrestored
therooftoahigherthannormalprofile. Thebuildingspneumaticreliefsystemwasvery
slowtoreact,butafterafewminutesitbroughtthepressurebackdowntotheset
pointpressure. Bynowitwastoolateastheunstablemassorpond,consistingof
water,snowandicetomovetowardsthewesttrianglepanel. Itwasthemovementof
water,snowandicefrompaneltopanelthatcausedtheinvertedpanelstopopup,
creatingveryloudsoundsrecountedbywitnesses. Asthemassreachedtheendofits
travelatthewesttrianglepanel,theresultingavalanchecausedthewesttrianglepanel
tobulgeinwardabout7.5to8feet. Atthesametime,thismasshittheringbeamarea
belowthewestpanelwithatremendousforcewellbeyondtheroofpanelmaterials
designloading. Atearonthewesttrianglepaneloccurred.
Asthedamagedpanelcontinuedtotear,itwasnolongerpracticaltomaintain
adequateinternalpressureasfurtherdamagewasimminent. Thedecisionwasmadeto
safelyevacuatethebuilding,andtostartturningoffpressuresupportsystemswhich
easedtheroofdownintoitsconstructionpositioninasafemanner. Theroofslowly
defaultedtoitsconstructionpositionapproximately6metersabovetheStadiumfloor
andseats.
Oncetheroofwasstableinitsconstructionposition,asafetyandstructuralassessment
wasconducted. Aseachareawasdeemedsafe,workersweredirectedtobegin
assessmentandwatercontrol. Anumberofprofessionalswereonsitetoassessthe
damagebothupontheringbeamandinsidetheStadium.
CausalAnalysisandDiscussion
Basedonthefactualinformationanddata,keyfactorsarehighlightedandexaminedto
determinehowtheyhadcontributedtotheincident. Thesefactorsareweather,roof
loading,rooffabric,equipment,policiesandprocedures,Stadiumculture,andcrisis
management. Differentcausalanalysismethodologieswereusedinfleshingoutthe
detailsandultimatelypinpointingtherootcause.
Itisimportanttonotethatevidencecollectedduringthisinvestigationclearlydispels
anynotionthatpersonnelotherthanthecontrolroomoperatorwereflippingdifferent
switchesatthesametimeinattemptingtorecovertheroofincrisis. Allcommands
wereinitiatedbythecontrolroomoperatorthroughthebuildingautomationcomputer
andnotbypersonnelturningonfanswithswitchesfromtherearHoneywellpanel.All
therequestedpressuresettingswerewellwithintheknownsafeoperatingrangeofthe
building.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20075
RootCause
Thecausalanalysisofthiseventpointsdirectlytothelackofeffectivepolicies,
proceduresandtrainingastherootcauseofthisincident.
Furthermore,ageneralblindnessandlackofunderstandingandtrainingrelatedto
theroofsupportsystems,operatingwithinanenvironmentwherepoliciesand
procedureswerefullofholes,hadallowedsnowaccumulationtogounnoticed. Pooror
verylittleroofincrisisidentification,assessmentandtrainingalongwithconflicting
controlroomsystemsallcameintoplaytocausethedamagetothewesttrianglepanel.
Recommendations
Thecorrectiveactionsclearlysupportedbythisinvestigationcanbebrokenintothe
following5categories:
1.Create,inform,implementandpostaNoSnowAccumulationpolicyforthe
roof. ThispolicywouldbecomethegoalfortheStadiuminkeepingtheroofup.
Itdefinesthefacilityphilosophyandmakesitcleartoallpartiesthateveryeffort
willbemadetopreventsnowfromaccumulatingontheroof.
2.Withoutfurtherdelay,completeanexternalauditofStadiumOperationsto
focusonpolicies,proceduresandtrainingthenimmediatelyimplementthe
correctiveactions. ThisincludesriskidentificationandmanagementinStadium
maintenanceandoperations.
3.Immediatelyhaveaqualifiedperson,assistedbyaqualifiedtestinglaboratory
conductaphysicalassessmentoftheroofmaterialandseamsadjacenttothe
ringbeamstartingwitheachofthetrianglepanels.Makethenecessary
corrections.
4.Haveaqualifiedperson,knowledgeableintheseroofsystems,assess,modify
andupdateroofsupportcontrolsystemsincludingamethodforthecontrol
roomtoseetheroofandknowwhenitisincrisis.
5.Completeacomprehensiveindependentexternal,auditoftheOccupational
Health&Safetyprogramofthisfacilityandimplementrecommendations.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20076
IntroductionandOverview
ThereportsummarizestheJointHealth&SafetyCommitteesincidentinvestigationof
theBCPlaceroofdeflationincidenttookplaceonJanuary5,2007.
FollowingthecontrolleddeflationonJan5,2007,attherequestofBCPlace
Management,aninternalinvestigationwasconductedbymembersoftheJointHealth
&SafetyCommitteewiththeassistanceofanexternalOHSConsultant. The
investigationisbasedonfactualdataandinformationandeventsleadinguptothe
deflation. Membersontheinvestigationsubcommitteeandthejointhealth&safety
committeelefttheirmanagementorunionhatsoutsidetheinvestigationdoortoensure
theinvestigationwasdonethroughanobjective,impartiallens. Thepurposeofthis
investigationwastofindfactsanduncoverrootcausesthatweredirectlyresponsible
fortheevent,nottoassignblames,orfingerpoint. Therecommendationsputforthat
the
end
of
the
document
aim
to
prevent
similar
events
from
happening
in
the
future.
Bypiecingalltheinformationtogether,thisreportpresentsaclearpictureofwhattook
placeandthesequenceofeventsleadinguptothedeflation. Reconstructionofthe
dayseventswerebasedonanumberofinformationsourcesincludingeyewitness
accountsboththroughinterviewsandwrittenreports,weatherreports,internalrecords
andcharts,controlroomlogs,newsmedia,inspectorsandprivateindividualsvideo
footageandphotographs,andengineerstesting,findingsandpreliminaryreports.
Thisreportgoesdeeperthansimplyrecordingthestepsoftheevent. WhiletheGeiger
Engineersreportcoverstheengineeringtechnicalaspectsoftheincident,the
InvestigationSubcommitteeexaminedabroadrangeofcausalfactorsthatwere
identifiedduringtheanalysisphaseofinvestigation. Inadditiontodealingwithmuch
Stadiumspecifictechnicalinformation,thesubcommitteealsolookedcloselyintothe
operationalside. BoththeEngineersreportandthisinvestigationreporttaken
togetheraddressthecompletescopeoftheroofdeflationincident.
Thisinvestigationreportconsistsofvarioussections,startingoffwithadetailedaccount
ofthedaysevent,followedbycommentariesandindepthdiscussionsonkeyelements
andfactorstodeterminetheirsignificanceintheroofdeflationincident. Casualanalysis
employingdifferentmethodologieswasusedtoidentifyrootcausesandassociated
contributingcauses.
AsthisreportcontainsmanytechnicaltermsspecifictotheBCPlacesroofsupport
system,whichmightbeunfamiliartosomereaders,pleaserefertoAppendixA Roof
SupportPressureControlSystemsDescription. Forthepurposeofkeepingthemain
reportsuccinct,technicaldataandsupportinginformationaremadeavailableinthe
appendices.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,20077
Thisinternalinvestigationhadthecompletecooperationofbuildingmanagement,
union,staff,contractors,professionalsandprivatecitizens. Thisinvestigationteamalso
workedcloselywithKrisP.Hamilton,P.ENG,ofGeigerEngineering,thefirmthat
designedthestadiumroof. Wewishtoexpressourappreciationtoallthesepartiesin
theirassistanceintheinvestigatingprocess.
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SequenceofEvents
TheControlroomoperatesina12hrrotation,0700to1900asdayshift,1900tonext
day0700asnightshift. ThissequenceofeventsinitiatesfromthenightshiftofJan4
(1900ofJan4/07to0700ofJan5/07). Atypicalcontrolroomshiftisatwostaff
memberteam:aControlRoomOperatorwhoisresponsibleforthemonitoringof
systemsandcontrolsofthebuildingandanEastAirlockSecuritywhoisresponsiblefor
internalandexternalsecurityandpatrolofthebuilding.
Thedatacollectedduringtheinvestigationsupportsthefollowingscenario:
Jan4
Theshiftwasdescribedtohavestartedlikeanyother,normal,uneventfulnightshift.
23:13 alowtemperatureoutsidealarmcameinindicatingandprintingoutnearfreezing
outsidetemp,watchforsnow.
Jan5
04:10, Smokealarmonfirepanel,Zone3,sentEastAirlock(EAL)Securitytocheckitout.
Showerincoachslockerroomwasleftonandsteamsetoffalarm. Turnedoffshower.
04:20, ControlRoom(CR)Operatortriedtoresetalarm,butthewholepanellituplikea
Christmastree. Allindicatorlightscameon.
04:25, CROperatorcalledsupervisorbutcouldnotgethimathome,socalledthe2nd
supervisorathome,andleftmessageonmachineastherewasnoanswer.
04:27, Becausetheyhadnoideawhythefirepanelwasalllitupthesecuritypersondecidedto
goonactivefirewatch.
04:29, 1stsnowconditionalarmcamein. 1hourdelaystartedtocountdown(systemdefault
setting).TheCROperatoractivatedthe15hourdelayontherearHoneywellpanel.(See
AppendixCRoofSupportSnowMeltSystem)
04:30, TheroofsensorsentamoisturealarmandprintedPrecipitationdetectedatroof
sensors. (thesystemisconfirmingthatbothlowtemperatureandmoistureexist,
showingarealpossibilityofsnow).
04:31, CROperatorwentoutsideofeastairlocktoobserveweather.Itwassnowinglightlybut
hecouldnotseeanyaccumulationontheroof.
04:40, CROperatorcalledEnvironmentCanadaweatherofficeforreport. Theweatherreport
wasgivenasfollows:GREATERVANCOUVER.TODAY.PERIODSOFSNOWCHANGINGTOPERIODSOFRAINTHISMORNING.
RAINFALLAMOUNT20TO30MM.BECOMINGWINDY.HIGH8.TONIGHT.PERIODSOFRAINENDING
OVERNIGHTTHENCLOUDYWITH30PERCENTCHANCEOFSHOWERS.AMOUNT10MM.WINDY.LOWPLUS
5.
05:00, Bythistime,neitherofthesupervisorshadcalledback,sotheCROperatordecidedto
calltheDirectorofOperationsregardingthefirealarm,andsnowconditionalarm.The
DirectoraskedtheOperatortoresetthefirepanelandwastoldCRhadtriedthat,but
thewholefirepanellituplikeaChristmastree. Directorsaidhewouldbetherearound
6:15to06:30.
05:05, Engineeringsupervisor(2nd
call)calledbackinresponsetothemessagetheyleft.CR
Operatortoldhimhehadalreadyspokentothedirectorandhewasonhiswayin.
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Supervisordiscussedfirepanelproblemandhadtoldthemnottoworryaboutitand
thetechnicianwouldfixitwhenhegetsinat08:00.
05:42, UnbeknownsttotheCROperator,theEnvironmentCanadaweatherofficehadnow
issuedanewreportat0542:GREATERVANCOUVER. TODAY. PERIODSOFSNOWCHANGINGTOPERIODSOFRAINTHISMORNING.
SNOWFALLAMOUNT2CM. RAINFALLAMOUNTS20TO30MM. BECOMINGWINDY. HIGH8. TONIGHT.
PERIODSOFRAINENDINGOVERNIGHTTHENCLOUDYWITH30PERCENTCHANCEOFSHOWERS.AMOUNT
10MM.WINDY.LOWPLUS5.
05:53 1stsnowconditionalarmcancelleditself,indicatingsnowconditionshavecleared.
05:59, 2nd
snowconditionalarmcameinfromthesensors,1hourdelaystartedtocountdown
bydefaultofthesystemandthe15hourdelaybuttonwasmanuallyactivated.
06:09, 2ndsnowconditionalarmcancelleditself,indicatingsnowconditionshavecleared.
06:14, 3rdsnowconditionalarmcamein,1hourdelaystartedtocountdownbydefaultofthe
systemandthe15hourdelaybuttonwasmanuallyactivated.
06:20, TheDirectorarrived,reviewedsituationwiththeCROperator,thenwentintothe
Operationsofficeandprintedoutthelatestweatherreport.
06:27, 3rdsnowconditionalarmcancelleditself,indicatingsnowconditionshavecleared.
Itshouldbenotedatthispointthatallstaffandsupervisorsthatwereinterviewedhadspecificallynotedsnowaccumulationofupto2inchesofslushywetsnowonthegroundoutside
ofthestadiumastheywerestartingtoarriveatwork. Somereportedrain,somesleetandsome
snowbutallnotedtheaccumulationontheground.
06:45, ThedirectorspoketothenextshiftCROperator(07:0019:00)ashehadshowedup
earlyforhisshift. GavehimacopyoftheEnvironmentCanadaweatherreportissuedat
05:42whichhehadprintedoutwhenhegotin.HealsoreiteratedwiththeCROperator
towatchtheweatherandapplyheatathisdiscretion.
06:45, Atthistime,theEnvironmentCanadaweatherofficeissuedanupdatedadvisory
indicatingthefollowingbutitwasunknowntostaff.GREATERVANCOUVER,SNOWFALLWARNINGINEFFECT.
TODAYPERIODSOFSNOWCHANGINGTOPERIODSOFRAINTHISMORNING. SNOWFALLAMOUNT2CM
EXCEPT10CMOVERHIGHERTERRAIN.RAINFALLAMOUNT20TO30MM.WINDY.HIGH8,
TONIGHT.PERIODSOFRAINENDINGOVERNIGHTTHENCLOUDYWITH30PERCENTCHANCEOFSHOWERS
AMOUNT10MM.WINDY.LOW,PLUS5.
06:57, Controlroomshiftchange,newoperatorsignedon.
Itshouldbenotedatthispointthatmostoftheinterviewedstaff,commentedthatthe
temperatureinsidethebuildingthatmorningwascoolerthanusual.Duringthemorningof
January5,2007,theinsidebuildingtemperaturewassetat10degreecelcius. Thisisthe
minimumtemperaturesettingallowed. Therewere2adjustablespeedfans(ASDs),#10inFan
Room#5inFanRoom#8.Thecomputersetpointwassetat250Pa. Becauseitwasa
turfupday,toincreaseventilationforthedieselpoweredforklift,twoconstantspeedfans
(CSFs)#4inFanRoom2,fan#14inFanRoom7wereturnedon.These2constantspeedfans
areinrecirculationmodebecausethebuildingpressureismaintainedbythecomputerdriven
AdjustableSpeedDrives. Thecomputerpressuresetpointwasat250Pa,thepressureandrelief
controllers,onthemanualHoneywellcontrolpanelweresetat250Paforthepressure
controllersandat300Paforthereliefcontroller. Thisappearstofollowthebuildingsprocedure
manual. Soupuntil12.33,therewere2ASDsand2CSFsinoperation.
08:10, Shortlyaftershiftbriefing,oneworkerfromtheTurfupcrewcommentedtotheCR
Operatorandasupervisor:WhyamInotwearingmytshirtinsidethismorning?The
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responsewaseconomicsdictatewedonotneedtheheat. (Theworkerherereferredto
whensnowmeltison,theStadiumwouldbeheatedandwarmenoughtowearonlyat
shirt).
08:16, CROperatorturnedonconstantspeedfan4inroom2.Thisisastandardprocedurefor
turfupoperation.
08:17, 4thsnowconditionalarmcamein.1hourdelaystartedtocountdown.
08:18, CROperatorturnedonconstantspeedfan14inroom7.Thisisalsopartofthestandardprocedureforturfupoperation.
08:34, the15hourdelayforsnowmeltwasmanuallyactivated.
09:00, AworkerhadbeenworkingonLevel2andnoticedoutsidesnowaccumulation. Worker
thenwentintoControlRoomandaskedwhysnowmeltwasnton.
10:05, 4thsnowconditionalarmcleareditself,indicatingsnowconditionshavecleared.
10:15, Aturfupworkernoticedthespeakerclusterwashangingataveryoddandcrooked
angle.
10:30, DutyManager(DM)whendoingroundsonlevel2,notedabout2inchesofwetsnowon
theplazadeckwithwhatappearedtobeverywetlookingfootprintsinit. Whenrounds
werefinishedtheDMwentintothecontrolroomandreportedherobservationtothe
CROperator.TheCROperatorlookedinthecameraattheroofandsawnosnow,so
toldtheDMthatthesnowhadslidoffoftheroofandnottoworry.Whatwasnot
realizedwasthattheroofareavisibletothecamerawasabovethesectionofthe
stadiumaffectedbyFanRoom#2. Assuchtheresidualheatcombinedwiththeair
circulationfromthefaninFanRoom#2hadmeltedthesnowinthatarea. Thecamera
didnotseetherestoftheroofwhichwasstillcoveredwithsnowandpossiblyfrozen
snow.
10:55, Thepressuredialchartchanged. ThisisadailyactivityintheControlRoom,pressure
dialchartsarechangedevery24hoursat1100. OnJanuary5,timeindicatedonthe
chartseemstobeslightlyoutofsyncwhencomparedtothecomputerdataprintout
logs. Thechartappearstobeabout3or4minutesbehindtheactualtimeline.
11:00, UnbeknownsttotheControlRoom,EnvironmentCanadaweatherofficeissuedagaina
snowfalladvisory: GREATERVANCOUVERSNOWFALLWARNINGINEFFECT
TODAY.PERIODSOFRAINATTIMESMIXEDWITHSNOWNEARNOON. SNOWFALLAMOUNT2CMEXCEPT
10CMOVERHIGHERTERRAIN.RAINFALLAMOUNT20TO30MMWINDSOUTH40TO60KM/HBECOMING
SOUTHWEST30GUSTINGTO60EARLYTHISAFTERNOON,HIGH6
11:01, 5thsnowconditionalarmcamein. 1hourdelaystartedtocountdown,andthe15hour
delaybuttonwasmanuallyactivated.
11:20, EastAirlockSecurityandtheDirectorofOperationswentoutsidetotheTerryFoxplaza
todealwithavagrant. EALSecurityreportedtherewaswetsnowfallingandnoticeda
littlesnowstickingtorooflookingupfromTerryFoxarea.
11:30, TwoworkersfromtheturfupcrewwentoutsideattheDisabledEntrancebytheturf
storageareaandnoticedheavy,bigflakesofwetsnowwasfalling.
Lunchbreak,from12noonto12:30sonoonewasworkingonthefieldduringthistime.
12:06, 5thsnowconditionalarmcleareditself,indicatingsnowconditionshavecleared.
12:10, CROperatorlefttheControlRoomtograbapop,hewalkedouttotheeastfield
entranceandlookedupattheroof. Herememberstherooflookednormaltohim.
12:20, Contractworkercamebackearlyfromlunchandnoticedthelowspeakercluster,(about
15or20feetoffoffieldlevel). Hewatchedforafewminutesnoticedtheroofwasvery
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flat(flatterthanhehadeverseenit)thenwastoldtostaybackfromthefieldandto
remainintheconcourse.
12:31, Astaffmembernoticedwhenreturningfromlunch,walkingonthefieldthroughthe
EastAirlock,themainspeakerclusterwasverylow,about10feetabovethefield. He
thenlookedupattheroofandnoticedsomethingveryodd.Herealizedtheentiretop
areaoftheroofwasflat.Hedefineditwasflatfromtheinsideanchorpointofthe
suspensioncablesofthesatellitespeakerswhicharelocatedaroundtheperimeteroftheroof.HethenwenttotheDutyManagerandreportedthis.Itwasalsoobservedthat
3or4ofthediamondsectionsaroundtheareaofthespeakerclusterwereinverted.
12:32, DutyManagernoticedworkersstaringattherooffromtheEastAirLock,whenshe
returnedfromlunch. Sheobservedthespeakerclusterwasactuallysittingonthefield
atthispointandshethoughtitwasoddbecauseitwouldblocktheforkliftaccessfor
theturfupoperation. Thenshenoticedtheroofwasflatlikeapancake.Shetold
workerstostayclearofthefieldandthenwenttotheControlRoomtoreportthe
situation.
Atthispointseveralstaffhadnowcomebackfromlunchandnoticedthegrowingcrowdof
peoplewatchingtheroofasitseemedveryeerie. Aroundthebuildingatvariouslocations
staffshadnoticedtheroofflatandlowandwerenowstartingtowatchwhatwashappening.
Thoseinterviewedwitnesseswhowereonsitethatday,allreportedseeingtheroofbeingflat
andunusuallylow,aswellas:flatlikeapancake,wrinkledlikeaprune,couldnotseethe
sideoftheringbeam,onesidepusheduplookinglikeintestines,speakerclustertiltedata
45degreeangleandwaterwasdrippingthroughthevents,theroofwasdimpling,etc..
12:33, Twoworkersreturnedfromlunch,andreportedthesituationtosupervisors
immediately. BothengineeringsupervisorsandastaffmemberranintotheControl
Room. TheyimmediatelyalertedtheCROperatorthattheroofwascomingdown.
12:33, Itisnowapparentthattheroofisincrisis. OnesupervisorinstructedtheCROperatorto
increasethepressureto300Paandpreparethebuildingforsnowmelt. Theother
supervisorwenttothebackwiththeotherworkertochecktheMagnehelicPressure
Gauge.
SeveraladditionalstaffandsupervisorsarenowintheControlRoom. Ithasbeendetermined
thatatleast5people(supervisors,workerandCROperator)wereintheControlRoom. TheCR
Operatornotonlyhavingtodealwiththeroofincrisis,buthenowhasagroupofpeople
offeringwellintentionedassistanceandprovidinginstructions.
ITMUSTBENOTED,theonlypersonissuingcomputercommands,andadjustingtheHoneywellpressureandreliefcontrollers,intheControlRoomuptothepointofthepanelfailure,wasthe
CROperator.
Thecomputerpressuresetpointwasincreasedfrom250Pato300Pa. Thissetsthe
pressureparameterfortheadjustablespeed(ASD)fans. Atthistime,therewereonly2
ASDfansrunning. TheASDfanswerenowworkingtoincreasepressuretowards300Pa.
The2constantspeedfanswhosedampersarecontrolledbytheHoneywell
pressure/reliefcontrollerswereinrecirculationmode,astheyhaveachievedthe
controllersetpointof250Pa.ThepressurecontrollerontheHoneywellpaneliskeeping
theoutsideairdampersclosed,asithasthe250Paitissetfor.Itisimportantto
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understandthattheconstantspeedfandampers(CSFs)taketheirpressuresettings
fromtheHoneywellpressurecontrolleronly,andcomputersetpointchangesdonot
affectCSFs.
**note,Basedonwitnessaccountsandanalysis,thepressureandreliefcontrollersonthe
HoneywellPanelatthebackofthecontrolroomdidnotappeartohavebeenchangedtoreflect
theincreaseincomputersetpointfrom250to300Pa.Theprocedurewhenchangingthe
computerASDsetpointto300PaistoimmediatelygotherearHoneywellpaneland
changethepressurecontrollersetpointto300Paandtochangethereliefcontrollerset
pointto350Pa. WhenASDfansarerunningthereliefcontrollersetpointmustalways
be50Pahigherthanthecomputer/pressure controllersetpoint.
12:34, Fan#7(ASD)inroom4wasturnedonbycomputercommandbytheCROperator. This
fanwastakingitssettingfromthecomputersetpointof300Pa. Forabriefperiodof
30secondsto1minute,therewillbeairlosscausingasmalldropinpressure,(atypical
occurrenceafterafanisturnedon),butshortlyafterthat,all3ASDfansshouldbe
rampingupto300Pa.
EvidenceindicatesthatbecausetheASDfanstaketheirpressuresettingfromthecomputerset
point,whichisbasedonanaveragefromareadingtakenineachofthe8fanrooms,they
usuallyshootalittlehigher(8to10Pa)thantheMagnehelicpressuregaugethatcontrolsthe
relief.Asettingof300Paonthecomputerisreallyabout310Pa.ontheMagnehelic.Thisisnot
achievablebecausetheHoneywellpressurecontrollerwasnotresetto300andtherelief
controllerto350. Theywerestillontheoldsettingsof250and300. ThismeanttheASDfans
werenotgoingtobeabletohitthedesiredpressureof300Pabecausethereliefdamperswill
openanddrainoffthepressurebeforetheASDscouldreachthesetpointof300Pa.Therelief
systembeingpneumaticallycontrolledissoslowtoreact,needsabout2minutestoopenand1.5
minutestoclose,thatthemaximumpressuretheASDfanscouldhopetoachieveisabout270to
280Pa.
12:36, CROperatorcalledthesteamplanttoaskforsteamtogotosnowmeltmode.Hegot
theOKasthesteamplanthadbeenpreparedforhiscall. Hethenoverrode
temperatureandmoisturesettingsontheEnergratedcomputerinpreparationfor
immediatesnowmelt.
12:36, 15hrdelaytimerforsnowmeltwasactivatedonthebackHoneywellpanel.Atthispointtherewasgrowingconcern,becausewith3ASDfansrunningat100%toincrease
thepressurebuttherewasverylittlemovementintheroof,andthepressurehasbarelymoved
up. Noonerealizedreliefsettingsonthepressureandreliefcontrollerswereconflictingwiththe
computersetpointfortheASDfans. Thereliefcontrollerwasopeningthereliefdampersto
reducepressurebeforethecomputersetpointcouldbeachieved.
12:37, Aworkerhadgoneouttothefieldandobserved3invertedpanelsabovethespeaker
clusterandreportedthisinformationtoControlRoom. Engineeringsupervisoratthis
pointdecidedtoruntotheTechShopandgetatechniciansassistance. Heknewthe
technicianwashavinghislunchthere. Heranintotheshopandtoldthetechnicianthat
theRoofwasfallingandhemustgointothecomputerandraisethepressureto400
Pa.
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Thetechnicianfollowedhissupervisorsinstructionsandproceededtologontothe
computersystemfromhisshopandmakethechanges. Ittookabout4minutestoenter
thedata.
Itshouldbenotedthecomputersetpointchangedbythetechnicianwouldnothave
beeneffectiveforthesamereasonabove. BecauseHoneywellreliefcontrollerwasstill
at300Pa,thereliefsystemwouldreacttoreducepressure;andthereforeprevented
theASDfansfromachievethis400Pasetpoint.
12:37to12:38, meanwhileintheControlRoom,CSFs#12,then#5wereturnedonatthe
computer.
12:39, ASD#2wasturnedonatthecomputer.Forabriefperiodof30secondsto1minute,
therewillbeairlosscausingasmalldropinpressureasthisASDfancomesonline.
12:40, theCROperatoratthispointactivatedsnowmelttoapplyheatdirectlytotheroof.
Activationofsnowmeltatthispointimmediatelyoverrodethecommandsfromthe
technician,asittakespriorityoverandsetsthecomputersetpointimmediatelyto300
Pa. Theremotesetpointrequesttoputpressureupto400wouldhaveatbestbeenin
effectverybriefly. Atthispointthecomputersystemwasunderseverestressandsome
datawasnotevenacknowledged.Muchofthedatabeingprintedfromthecomputerin
thecontrolroomwasoutofsequence.
Justpriortotheprevious3fansrampinguptospeed,theHoneywellpressurecontroller
andthereliefcontrollerwereresetto350Parespectively.Thishappenedjustasthe
pressurelosswasineffectfromASD#2startingup.
Nowallthingsarechanging.AssoonasthesettingswereontheHoneywellpanel. Therelief
systemswouldbegintoclosedowntopreventairloss,the4ASDfanswouldhavequickly
achievedtheprevioussetpointof300Pa. LikelybythetimetheASDfansachievedthesetpoint
of300Pa.,thereliefdamperswerecompletelyclosedandthe4constantspeedfanswerenow
gettingfulloutsideairastheywerepumpingpressuretoasetpointof350. Withallfourcsf
fansworkingtowards350Pa,itwaslikelythissetpointwasachievedveryquickly.
Thisistheturningpointfromanoverloadedrooftoanavalanche.Thestagewasset.WithbothHoneywellpressureandreliefcontrollerssetat350Pa,thishadsetuptheperfectsituation
forthepneumaticreliefcontrolsystemtocauseapressureovershootabovethesetpoint.
12:41to12:42
Pressurerapidlyincreasedto520Paorapprox68%onpressurechart.Ananalysisofthe
Honeywelldialchartshowsittookabout2minutesforthepressuretokickupto520
Pa. Bythetimethereliefcontrollercouldreactandopendamperstoreducepressure,
thebuildingpressurehasnowreached520Pa.
Thereliefcontrollerisonapneumaticsystem;thereforeitwouldhavetaken2minutesforallofthedamperstoopen. Thisdelayedthesystemsabilitytodrainoffexcess
pressure. Oncethepressurehadpeakedat520Pa,thereliefcontrollerwouldnowhave
allreliefdampersfullyopentoreducepressure,andthepressurecontrollerwouldnow
fullyblockedoutsideairandonrecirculationfortheconstantspeedfans. TheASDfans
wouldbeatidlespeed. Thepressurethenbegantodroprapidlybackdowntotheset
point. Thepressureundershotbelowthesetpointreachingalowpointof33%or247
Pa. Asthepressuredroppedbelowthesetpoint,computercontrolledASDfansreacted
quicklyandbegantoraisepressure.
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SeeanalysisonPressureExcursion
12:43, AnavalanchewasheardbywitnessesontheTerryFoxplazasideoftheroof. (Section7
10)Witnessesreportedalow,rumblinghummingsound.
12:44to12:46 Staffnowstartedhearingthesoundofsnowmovingontheroof. Theyreporteditasa
lowroar,Thump,thump,thump,roofwasshakinglikeablanket,agiantwas
runningontheroof,jetplanestakingoffandothersequatedittothesoundofan
elephantrunningthroughthelivingroomtowardsthewestendandanotherdescribed
therewasawhooshingsound. Oneverydetailedaccountsaidthatheobservedalarge
bulbouspillowormass,likeafistbeingpusheddownontherooffromabove,moving
throughthediamondpanelsonebyonethenitmovedontothetopofthewesttriangle
andinvertedit,thenitmoveddowntowardstheringbeamatatremendousspeed.This
bulgewaslargeenoughthatitcompletelyblockedtheviewoftheclockwhenitgotto
thebottomofthetrianglepanel,(atleast7or8feetdeep).Hesaidwhateverthebulge
washadalotofweightinit. Inrapidsuccessiontherewasaloudcracklikesound,sort
oflikethesnappingofabullwhip,thentheSeikoclockexplodedandatearappearedin
thebottomcenterofthewestpaneljustabovetheringbeam.Thetearseemedtostop,
momentarily,atabout12feetinlengththenwaterandicecamepouringin.Thetear
thentookoffacrossthebottomthenuptheleftside. Asthewaterandicecontinuedto
pourin,peoplecontinuedtoobservethetearopenedtotheleftthenrightandthen
peeledopenlikeacanofsardines,youcouldhearaveryloudcrackingorflapping
soundasthepanelwaswhippedbytheairrushingoutofthebuilding.
12:46, Thepressurewasonitswaybackuptothesetpointof300Pawhenthewesttriangle
panelfailed. Atthispointthepressurewasabout37%or277Pa.Itappearsthataspan
ofabout12minuteselapsedfromtheinitiatingcorrectiveactiontothepanelfailure.
12:48, Atthispoint,thesystemisunabletomaintainadequateinternalpressuretosupport
theroof,andfurtherdamagewasimminent. Thedecisionforacontrolleddeflationwas
made.TheevacuationannouncementwasmadebytheDutyManagerandthenthe
controlroomoperatorplayedtheevacuationrecordingoverthePAsystem.
12:49, Fans#4,5,12&14weresequentiallyturnedofftoallowacontrolledandgentle
deflationoftheroof.
12:50, Whenthepressurewentbelow180Pa,thecomputerautomaticallyturnedonan
additional10fans.ThetechnicianhadtologontotheEnergratedComputerSystemto
maketherequiredsoftwarechangestoallowallfanstobeturnedoff. Thiswas
completedat12:51.
Atthispointtheroofwasdown. Barricadeswereplacedatallfieldentrancesandstaffweretoldtoremainintheconcourseareaundertheconcreteroof.
Onesupervisoralongwithtwoworkers,werethefirstonesupontheringbeamtoassessthe
damage.Whentheyarrivedonthetopthroughthewesthatch,theynoticedsnow/ice/slush,
withaccumulationuptotheeliminatorframes.Therailingswereallstillinplaceandthedrains
wereallfrozenandpluggedwithiceandslush.Theyhadtouseshovelstoclearthedrains.When
theygottheshovelsoutoftheroofboxes,theyobserved2inchesofveryheavy,frozensnowon
topoftheseboxes.Thelidsweresoheavytheycouldbarelyliftthem.
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Otherauthorizedpersonnelwentuptotheringbeamshortlyafterthedeflationwhichconsisted
ofBCPlace&PavCoemployees,architect,structuralengineers,Cityinspectors,rescue
professionals. Theircommentsincluded:lotsandlotsofsnow, asurprisingamountofsnow,
veryslippery,snowstillstuckonsomepanels,moresnowonthewestthantheeast,
cablesappearedcrooked,watersnowandiceontheseatsrightunderthehole,etc.. Some
ofthesepeoplewereabletotakephotographsofthedamageandtheroofconditionwhichgreatlyassistedtheinvestigationprocess.
Meanwhile,backinsidetheStadium,oncetheroofwasstableinitsconstructionposition,the
assessmentprocessthenkickedinandcallsweremadetobringinassessmentstaff,engineers,
riggersandsafetyprofessionalsetc.tocomeupwithanactionplan
Theabovesequenceofeventssummarizesthedatacollectedbytheinvestigationsub
committee. Itisthefoundationoftheinvestigationandhasformedthebasisforthe
causalanalysisoftheeventtodetermineoutcomesandrecommendations.
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CommentaryonSequenceofEvents
AsthesnowmeltalarmscameinonthemorningofJanuary5th
,thesnowandsleet
begantoaccumulateonthefabricsurfaceoftheroof. TheStadiumtemperatureset
point
remained
at
the
lowest
possible
setting
of
10
degrees
C
and
the
internal
pressure
setpointremainedat250Pa.
ManyStaffcommentedonhowcolditwasinthestadium. Whensnowwasobserved
fallingandaccumulatingonthePlazadecks,somestaffwereconcernedenoughabout
thelackofheat,thattheywenttothecontrolroomtoinquirewhytheheatwasnot
increasedorthesnowmeltsystemturnedon. The4th
and5th
snowmeltalarmscamein
at8:17and11:01thatmorningandbothtimestheoperatorpushedthe15hourdelay
timertopostponetheactivationofthesnowmeltsystem.
Atapproximately10:30adutymanagerwenttothecontrolroomandvoicedconcernto
theoperatorbecausetherewas2inchesofwetslushysnowontheplazadecks. The
controlroomoperatorlookedattheringbeammountedcameratocheckthecondition
oftheroof. Heinformedthedutymanagerthatthesnowhadslidofftheroofandnot
toworry.(SeeEquipmentsectionphotosoftheviewsforthiscamera)
Itshouldbenotedthatat08:18,constantspeedfan#4inFanroom2wasturnedon. As
theoutsideairtemperaturewascloseto0degrees,uponstartupandforaperiodof
time,thisfanroomwouldhavebeendeliveringasignificantamountofheatedairuntil
thereturnairtemperaturecameuptothesetpointof10degreesC. Theotherfactoris
thatfan#4isaconstantspeedfanandthereforewouldhavebeendeliveringaconstant
100,000CFM(cubicfootperminute)ofairflowasopposedtotheASDfanswhichwouldonlybeoutputtingmuchlowervolumesofair.
Thelevel5dischargedamperforfanroom#2islocatedatsection10ofthestadium.
Thisistheexactstadiumsectionthattheringbeammountedcameraislocated. A
significantamountofheatedairwouldhavebeendischargedfromthisdamperwhile
thetemperaturecontrolsystemopenedthesteamvalvetoraisethereturnair
temperaturetotheminimumvalueof10degrees. Thisheatedairwouldhaverisento
heattherooffabricintheimmediatevicinityofthecamera. Thereforewhenthe
operatorsawthismeltingeffectonthesmallareaoftheroofvisiblefromthecamera,
hewasonlygettingthesmallpicture. Inrealityonlythissmallsectionoftheroofwas
sheddingsnowduetotheheatingeffectcausedbyfan#4.(Thiseffectwouldhavebeen
mirroredinFanroom#7astherewasalsooneconstantspeedfanningrunninginthis
fanroomaswell.)
Contrarytowhatthecontrolroomoperatorwasobservingthroughthelimitedview
affordedbytheringbeamcamera,themajorityoftheroofsurfacewasactually
accumulatingsignificantamountsofheavywetsnow.
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EventAnalysisandDiscussion
Weather
Withminimalheatandaircirculation,theroofoutsidesurfacetemperaturewas
hovering
around
the
freezing
point.
The
weather
on
the
morning
of
January
5
th
was
comingfromanortheasterlydirection.Thenearestofficialweathermonitoringstation
wastheGVRDKitsilanoHighSchoolstation. Therecordedtemperatureshovered
around1degreeCfrom4AMtoNoon,therecordedprecipitationduringthistime
periodwas17.6mmandthewindswererelativelylightwithamaximumwindspeedof
14KPHfrom4AMto3PMonthatday.
TheStadiumwindspeedsensorslocatedatboththeEastandWestRingbeamlevelof
theroofdidnotgenerateanyhighwindwarnings(greaterthan30KPH),andnohigh
windwarningwasrecordedonEnergratedcomputerprintout. Wecansafelyconclude
thewindswerelessthan30KPH. Windsdidpickupmuchlaterintheeveningof
January5th
withwindspeedsincreasingto25KPHbetween10:00PMandmidnight.
Thereisnoevidencesupportthetheorythathighwindswereafactorinthecollapseof
theroof.
Photo#1 CamerapointsNorthWest
Steamplumeindicating
winddirectionfromthe
northeast
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Acompletesetofweatherdata,sourcedfromGVRD,EnvironmentCanadacanbefound
inAppendixE WeatherData.
Snowsquallsconsistingofheavywetsnow,sleetandrainmixedwithsnowfellonthe
stadiumthatmorningandafternoon. TimelapsevideosuppliedbyTomasSvabat
23degrees.netgivesagoodpictureoftheweatherincludingtimingandmagnitudeof
snowsquallsandwinddirection. (SeeAppendixHListingofPhotographsandVideo
Clips,inCDformat)
Inaddition,evidenceindicatesthatthetemperaturedroppedbelowfreezingfora
periodoftime,attheringbeamandroofduringthemorningofJanuary5th
. Witnesses
reportedfrozensnowandiceonthelidsofequipmentboxeslocatedontheringbeam
shortlyaftertheroofwasdeflated. Photographicandvideoevidenceshowssnowand
icefrozentothefabricoftheroof.
Photo#2taken45minutesafterdeflationfromringbeam
Inadditionthereisevidencetosupportthattherewasaliquidcomponentconsistingof
waterandslushontheroofaswell. Witnesseswhowereontheroofimmediately
followingthedeflationobservedandwalkedthroughslushontheringbeamdescribing
astheconsistencyofa711slushy. Underneaththisslushwasacoatingoficethatalso
frozeandblockedtheringbeamdrainsandalsomadeitveryslippery. ACityofficial
Photo#2
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indicatedhowslipperythewalkwaywasashemadehiswayfromtheEastringbeam
hatchtothewestsideoftheroof.
RoofLoading
ThestagewassetforcumulativeloadingoftheroofstructureonthemorningofJanuary
5th.
Beforewelookatloading,itisimportantthatthereaderunderstandthatthestadium
roofsupportsystemisbasedonaconstantpressureenvironment. Thisisdifferentfrom
theexampleofaninflatableexerciseball. Theexerciseballisaconstantvolume
environment.
Inthecaseoftheexerciseball,ifyousitontheball,yourweightpressingdownonthe
ballwillcausetheinternalpressureoftheballtoincrease. Thisisbecausethevolume
oftheballremainsconstant.Yourincreasedweightissupportedbytheincreasein
pressureandconsequentlytheballbecomesmorerigidwhenyousitonit.
However,intheconstantpressureenvironmentofthestadium,astheloadingonthe
roofinincreased,thecontrolsystemwillacttomaintainaconstantpressure. Asthe
loadincreasedandpresseddown,thecontrolsystemwouldbleedoffthepressure
increasecausedbyweighttomaintaintheconstantpressure. Asthereisnoincreasein
internalpressureduetoloadingoftheroof,thepressureremainsconstantasdoesthe
safetyloadmargin. Oncethesafetyloadmarginisexceededduetotheadditional
weightofsnow,theroofwillnolongerbeabletosupportitselfandwillbegintodeform
anddropinelevation.
Atanoperatingpressureof250Pascals,theroofloadsafetymarginwascalculatedto
beapproximately324tons. Thisisbasedonanevenlydistributedloadovertheentire
roofarea. (SeeAppendixBBCPlaceRoofLoadingCalculationsfordetailed
calculationsandanalysis)
Asprecipitationintheformofhighdensitysnow,sleetandrainbegantoaccumulateon
thefabricsurfacesoftheroof,theweightofthismaterialbegantoapproachthesafety
marginload.
Basedonphotographicevidence,thesnowloadontherooffabricwasuniformly
distributedovertheentireroofarea. Asdiscussedintheprevioussectiononweather
conditions,thereweretwoseparateformsofprecipitationontheroofthemorningof
thecollapse. Thefirstbeingauniformcoatingofwetsnowthateventuallyfrozetothe
rooffabric. Thesecondformconsistedofamoremobilemixtureofrainandslushthat
fellontopofthefrozenlayerofsnow. Thethreephotographsbelowillustratethe
uniformsnowcoverageontheroof.
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1stof3photostakenfromapartmentoppositestadium
Thissequenceofphotosillustratesthemovementofsnowoffthepanelsastheroof
camedown.
Photo#2ofsequenceshowsastheroofdropped,snowbeginstomigrateoffsomeroof
panelsslidingintothecenterofthebowl.
Uniformsnowloading
onthemajorityofroof
anels
Snowhasnowslidoffthis
rectangularpanel
Snowhasslidoffthe
lowerpartofthis
rectanglepanel
Theremainderoftheroofis
stillevenlycoveredwithsnow
Snowbeginsto
slideoffsome
ofroofpanels
inthisarea
WaterMarkonringbeamcaused
bythespilloveroftheavalanche
contentsofwater,iceandsnow
Photo#3
Photo#4
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Thirdphotoinsequenceillustratesfurthermigrationofsnowoffroofpanels.
PhototakenfromRingbeam45minutesafterdeflation
Piecesof
ice\frozen
snowbroken
awayfrom
fabric
Majorityof
easttriangle
isnowclear
Centerdiamond
panelsstillcovered
insnow
Northtrianglenow
mostlyclearofsnow
Photo#5
Photo#6 Secondarydamageto
rectangularroofpanelPilesofsnow/icethat
haveslidoff
rectangularroofpanels
downintothebowl,
theroofcableline
actedasabarrier
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Astheroofloadbegantoapproachthebalancepoint,theentiretopsectionoftheroof
begantoflatten. Astheroofapproachescriticalloading,itbecomesverysoft
structurallyandsmallincreasesinloadingpastthispointfurtherexacerbatethe
deformation. Themainspeakerclusterwhichissuspendeddirectlyunderneaththe
westernsectionoftheroofwastheextraweightpullingdownthealreadyoverloaded
roof. Thiscausedatleast3diamondpanelsinthisareatobecomeinverted.
Theinvertedareabecameacollectionpointwherewaterandslushbegantodraininto
thisareacreatingapond. Shortlybeforethewestpanelwasdamaged,witnesses
observed invertedpanelsinadditiontoseeingtheroofcablesinthisareabent
downwardandwaterpouringoutofonetheroofdomevents.
Thephotographonnextpageillustrateshowthemainspeakerclusterissuspendedand
anchoredtotheroofcables.
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InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,200723
Mainspeakerclustercablesupportanddiamondpanelsinthepond/inversionarea.
Themainspeakerclusterhangsinsidethestadiumsupportedby4cablesthatattachto
themainroofcablesjusteastofthewesttrianglepanel.
Mainspeaker
clustersupport
framecable
attachmentpoints
Roofdamper
reliefvents.
Witnesses
observed
waterpouring
outofthese
vents
indicativeof
panel
inversion.
TopofWest
trianglepanel.
Thisisthepanel
thatfailed.
MainSpeaker
clusterat15
meterposition
These4panels
withinthered
boundarywerein
distressandatleast
3ofthesepanels
wereinverted.
Avalancheor
pondtraveled
inthedirection
ofarrow
towardsthe
westtriangle
roofpanel.
Photo#7
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Theoriginaloperatingproceduresforthebuildingmakereferencetoloweringthemain
speakerclustertoavoidpanelorroofinversioninasignificantevent. Byloweringthe
mainspeakerclustertotheground,theweightwillberemovedfromtheroof,reducing
theloadinginthisareaoftheroof. Thisincreasestheabilitytowithstandmoreloading
withcausingdeformation.
Thisspecificareaunderthemainspeakerclusterhasanincreasedloadcausedbythe
weightofthespeakercluster. Hence,itwilltakelessofasnowloadthanotherroof
sectionstocauseeitherdepressionorpanelinversion. Asloadingcontinuesandmore
waterandslushfallsin,thepondorinversiongrowsinsize.
OnthedayofJanuary5th
,themainspeakerclusterwassetatits15meterdefault
position. Astheroofbecameoverloaded,witnessesobservedthemainspeakercluster
atvariousheightslowerthanthedefaultsetting. Thefollowingphotographillustrates
themainspeakerclusteratthedefault15metersetting,alongwithlowerpositions
observedbywitnesses.
ThisphotowastakenfromtheEastfieldentranceshowingthemainspeakerclusterat
15meterposition.
Speakercluster15
metersor49feet
aboveturf. Thiswas
thepositionsetting
oftheclusteron
January5,2007.
Photo#8
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Itisclearfromthephotographicevidencethatby12:24theloadingontheroofhad
exceededthesafetyloadmarginandtheroofbeganitsdecent. Atonepointatabout
12:24pmaphotographshowsthewestpanelinvertedatthetop. At12:25orsothe
roofwasabout50feetlowerthanitsnormalprofile.
This
photo
represents
the
normal
profile
of
B.C.
Place
at
250
Pa.
Thisphotowastakenabout20minorsobeforetheavalanche.
Pondorpanel
inversionin
thisarea
TopofVancity
officebuilding
West
Triangle
PanelTop
5
floors
ofVancity
Buildingnow
visible
Photo#9
Photo#10
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Noticethedifferenceintheelevationaswellashowflattheroofisonthetopsections.
Theroofprofileinthe2ndphotoisabout50feetlowerthanitshouldbe. Thewitness
thattookthispicturedidsobecausehethoughtitwasstrangethathecouldseethe
upperportionoftheVancitytowerlocatedatQuebecandTerminal. Normallyhecould
onlyseetheflagpolefromhisapartmentwindowandthispromptedhimtobegin
takingphotos.
Oncetheweighthadaccumulatedontheroofandthepondwasallowedtoaccumulate,
itwasinevitablethatoncethepressurewasrapidlyincreased,theunstablepond
consistingofwater,iceandsnowwasgoingtomovesomewhere.
Therewasarapidincreaseinpressurecausedbyapressureovershootinthebuilding
controlsystem(RefertofulldetailsonPressureExcursion). Thissuddenincreasein
pressurecausedtherooftoregainitsnormalprofile. Atthesametime,thiscauseda
suddenandinstantmovementofaminimumof8,000to11,000lbsofwater,iceand
snowtomovesuddenlyandquicklydowntheWesttrianglepanel.(SeeAppendixD
InvertedPanelLoadingCalculations)
Thislargemassinvertedthewesttrianglepanelasittraveledwestward,causingthe
paneltodepress6to8feetlowerthannormal. Asthemassmoveddownthewest
panelitfinallyhittheinsideringbeamandSeikoClockwithsuchtremendousforce,it
tooktheroofpanelwellpastitsdesignbreakingstrength.
Theresultwasafailureintheweakestspotwhichwasafieldweldwheretheskirting
hadbeenweldedtothefabric. Thisfindingwasdeterminedbytheengineer;see
AppendixGGeigerEngineersReportData,Sept14,2007,#207813. Hadtheweld
notbeenthere,thepanelfailurewouldhavefailedinthenextweakestspot,etc. The
forcelikelywaslargeenoughtofailevenanewpanel.Thekeytothispanelfailurewas
theavalancheofsnow,waterandicewhichshouldhavenotbeenallowedto
accumulateonthesurfaceoftheroof. Itshouldalsobenotedthatarectangularroof
panelwasalsodamagedonthesoutheastsideoftheroof. Photograph#6above
clearlyshowsarippedpanel. Thismayhavebeencausedbysnowandiceslidinginward
downintothebowlastheroofdeflated.
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Fiberglassfibers(rooffabricmaterial)werefoundimbeddedinthemetalhousingon
whatwasremainingoftheSeikoClockadpanel.
SeikoClockhousing Seikoclockframe
Inadditionsomeoftheinchmountingboltssecuringtheclocktotheconcretewereshearedoff. Thisgivesthereadersomeideaofthemagnitudeofthecollisionforces
thatweregeneratedwhentheavalancheormovingpondstruckboththeSeikoclock
andtheconcreteringbeam.
glassfibers
imbeddedin
damaged
metalclock
panel
Strandof
glassfiberon
Seikoclock
housing
6feethighconcrete
ringbeam
Noticehowmetalstructureis
deformedandpushedinasa
resultoftheavalanchecollision
forces. Thisiswherethe
committeeobservedinchanchor
boltsthatwereshearedoff.
Thispanelis
undamaged. Notice
howthefaceofthe
structureisflush
withtheringbeam
RemainsofSeiko
clockinternal
electronics/wiring
Rooffabricattachestoring
beamhere. Thearcgivesan
ideaofhowfardownbelow
theringbeamtheavalanche
causedthepaneltomove.
Photo#11
Photo#13
Photo #12
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RoofFabric
Theengineerhadconductedextensivetestingofthefabric. PleaserefertoGeiger
Engineersdraftreportonthefindings(AppendixGGeigerEngineersReportData,
Sept14,2007,#207813).
It
is
determined
fabric
weakness
did
not
play
a
significant
role
in
the
initial
failure
of
the
panel. Themovingweightofslush,snowandicethatwasexperiencedonJanuary5/07
wouldhavebeenenoughtodamageamuchnewerrooffabric. Duringthe
investigation,theengineersharedinformationonasimilarroofdeflationincident
happenedin1982attheMetrodomeStadiuminMinneapolis. IntheMetrodome
incident,thethenoneyearoldairsupportedroofbecameloadedwithsnowandice
withsomepanelsinverted. Operatingstaffincreasedinternalpressuretoomuchand
tooquickwhichledtoanavalancheofsnowandicethatcausedroofpanelruptureand
consequentlyatotalroofdeflation. TheMetrodomeexampleillustratesthatevena
practicallynewroofcansustainpanelfailureduetomovingroofloadsofsnowandice.
BCPlaces23yearoldroofmayhavedeterioratedandevenweakenedatsomespots,
butthatwouldnothaveresultedinapanelfailureonitsown. Itwastheheavyloading
ofrain,snowandicethatcompromisedtheintegrityoftheroofstructure.
PressureExcursion
ThissectioncontainstechnicalinformationwhichisuniquetoBCPlacesroofsupport
systems. Tofullyunderstandthebehaviorsandimpactsofinternalpressureincreases,
pleaserefertoAppendixA RoofSupportPressureControlSystemsDescription.
ThecausalanalysisoftheroofdeflationatBCPlaceStadiumonJanuary05,2007points
toarapidincreaseinbuildingpressure,abovesetpointof350Pa,asasecondary,
precipitating,contributingevent.Althoughthiswasnotthedirectcauseofthedeflation
itdoesappeartohaveplayedamajorroleinthegenerationofthepanelfailure. The
computerlogsandinterviewsofcontrolroomstaffandsupervisorsalongwithvarious
witnessaccountssupportthefollowingscenario:
OnJanuary5,2007justpriortotheroofcollapse,theroofsupportsystemwasusing
bothASDandCSFcontrolsystemsforpressurecontrol. ThereweretwoASDfans
runningandtwoconstantspeedfansrunning. Thepressuresetpointwas250Paon
boththecomputerandthepneumaticpressurecontroller. Asperprocedure,therelief
controllerwassetto300Pa. Inanalyzingthecircularpressurechartrecorder,wecan
seethatthepressurewasverystablepriortostaffrealizingthattheroofwasincrisis.
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PressureRecorderChartfromJanuary5,2007
EnergratedComputerConsolelocatedinthefrontareaofthecontrolroom
FullScale100%=750Pa
Inset:
Seebelowfor
detail
ThisistheEnergrated
computerusedtomakeset
pointchangesforASDfans
aswellasmonitoringand
controllingawidevarietyof
building/roofsupport
systemparameters.
Photo#14
Photo#13
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HoneywellControlPanellocatedintherearareaofthecontrolroom
Whenitwasdiscoveredthattheroofwasincrisis,thecontrolroomoperatorwasinstructedtoincreasepressuresetpointto300Paandtoprepareforsnowmelt
operation. Theoperatorincreasedthesetpointonthecomputerto300Pa. Duringthe
crisisenvironmentinthecontrolroomasstafftriedtoevaluatewhatwashappening,
thenextstepoftheprocedure,namelytoincreasetheHoneywellpressurecontroller
setpointto300PatomatchthecomputersetpointandthentoraisetheHoneywell
reliefto350Patoisolateitfromthesystem,didnothappen. Thissetpointchange
requiresthattheoperatorleavetheEnergratedcomputerconsoleandgotothe
Honeywellpanelthatislocatedattherearofthecontrolroom. Inthecrisis
environmentitisunderstandablehowthisstepcouldhavebeenmissed.
WiththeomissionofchangingthesettingsontherearHoneywellpneumatic
controllers,thetwoseparatecontrolsystemsbegantointeractinaconflictingmanner.
AstheASDfansrampedupto100%speedtotryandraisethestadiumpressureto300
Pa,thepneumaticreliefcontrollerbegantoworkagainstthisactionoftheASDfansby
openingupreliefdampers. Theconstantspeedfandamperscontrolledbythepressure
controllerwerenowinrecirculationmodebecausethecontrollersetpointof250Pa
hadbeenachieved. Hencetheconstantspeedfanswerenotworkingtoincrease
stadiumpressure,insteadidlingat250Pa.
Pressure
Chart
Recorder
Honeywell
Pressure
ControllerHoneywellRelief
damper
controller
SnowMelt
delaytimers
15hoursnow
meltdelay
button
Photo#15
Magnehelic
PressureGauge
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Insetofpressurechart: Pressureovershootanalysis
Asmorefanswereturnedoninpreparationforsnowmeltoperations,thepressureonly
increasedtoapproximately270to280Pabasedontheanalysisofthepressurechart
recorder. Asthebuildingpressurewasnotrespondingtothenewsetpointchangeof300Pa,andtheroofwasstillfalling,asupervisorrandowntotheTechShopwherethe
seniorcontroltechnicianwashavinghislunch. Heinstructedthetechniciantogointo
hiscomputerandincreasetheASDsetpointto400Pa. Ittookthetechnicianafew
minutestomakethesesoftwarechangestothesystem. Basedonanalysisitwas
determinedthattwofactorswereatworktocancelthissetpointchangetotheASDs.
Thefirstbeingthereliefdamperswhichwouldhavebeenopeninguptoreducethe
pressureonceitroseabove300Paandthesecondiswhenthesnowmeltsystemwas
turnedon. Itwasdeterminedthatwhentheroofsupportsystemwentintosnowmelt
mode,thesnowmeltsetpointof300Patookpriorityandcancelledthe400Pasetpoint
changemadebytheTechnician.
Meanwhilebackinthecontrolroom, directionsweregiventothecontrolroom
operatortoraisethesetpointto350Pa,themaximumpressuresettingallowedonthe
Honeywellpressureandreliefcontrollers.
TheoperatorthenchangedtheHoneywellpressureandreliefcontrollersto350Pa.
Withcomputerpressurecontroller,sinceitwasalreadyinsnowmeltmode,pressure
Pressureat270280Pajust
priortocontrollersetpoint
changeto350Pa
Pressurepriorto
crisis=262Pa
Setpoint =250Pa
PeakPressure=520Pa
LowpointofundershootwhenASD
fansbegantorespond=247Pa
Fansare
turnedoffto
deflateroof
West
TriangleFails
Numbersrepresent
percentageof750Pa.
Fullscale
70=.7x750=525Pa
Photo#16
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setpointwaslockedat300PafortheASDfans. Theconditionswerenowsetupfora
largepressuresetpointovershoot.
Oncetheoperatormadethesechangesanumberofpressurerelatedeventsoccurred.
TheHoneywellpressurecontrollerbegantorespondtotheincreaseinsetpoint. Asthe
stepchangeinsetpointwas100Pa(250to350Pa)thepressurecontrolleroutput
veryquicklyincreasedfromzerooutput(fullrecirculation)to100%pneumaticoutput.
This100%signalcausedthefanroomdamperstoswitchfromfullrecirculationtonow
callingfor100%outsideair.
Simultaneously,thereliefcontrollerwhichalsohaditssetpointchangedto350Pa
begantooutputitspneumaticsignaltocloseallofthereliefdampers. Theneteffectof
theseactionscreatedarapidincreaseinpressure. ThefourASDfanswererunningat
closeto100%,thefourconstantspeedfanswerenowdrawinginoutsideairat
maximumrates. Wenowhaveeightfansdrivingthepressuretowardstheirrespective
setpoints. Asthepressureroseto300Pa,theASDfanswouldhavesloweddown,as
theirsetpointvaluewasnowachieved. Thefourconstantspeedfanscontinueddriving
thepressureupwardtowardstheirsetpointof350Pa.
Thisiswherethecharacteristicsofapneumaticsystemworkedtoamplifythepressure
overshoot. Asthepressureroseabove350Pa,thepressurecontrolleroutputwould
nowstarttodecrease. Butsinceitisapneumaticsignal,ittakestimeforthesignalto
propagatethroughthepneumaticsystemoverthelargedistancesfromthecontrol
roomtothefanrooms. Insomecasesthisdistanceis800feet. Consequentlyittook
timeforthesignaltoreachthedampersandtobegintoreducetheamountofoutside
airbeingbroughtin(thisincreasedpressure)andswitchtorecirculationmode. During
thistimelagthepressureinthestadiumcontinuedtorisewellabove350Pa.
Inparalleloperation,thepneumaticreliefcontrollerisnowsensingthepressurerising
aboveitssetpointof350Pa. Asthepressurerisesabovethesetpointthepneumatic
controlleroutputsendsasignalouttostartopeningthebanksofreliefdampers.
TypicallyduetothelocationofthereliefdampersonLevel4andattheringbeamlevel
5ofthestadium(distancesofcloseto1000feet)thetimedelayforfullyopeningthe
reliefdampersistwominutes. Whilethisdelayisineffectthepressureisstillrising.
Bythetimethereliefdampersbecameeffectiveandhaltedtheupwardpressure
overshoot,thepressurehadrisento68%onthepressurechartwhichrepresentsapeak
pressureof520Pa. Forsuchalarge100Paincreaseinpressuresetpoint,combined
withtherapidturnonofadditionalfans,thisisnotanunreasonableovershootabove
thesetpoint.
Theonlyproblemwasthesignificantroofoverloadingandsubsequentpanelinversions
thatcreatedalargeunstablemassonthewestendoftheroof. Oncethepressurewas
increased,theroofbegantoregainitsnormalprofile. Asthepressurecontinued
towardsitspeakof520Pa,eventuallytheinternalpressurewasenoughtoovercome
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thedeformationoftheroof. Asthishappened,themassofsnow,waterandicebegan
tomovedownwardaccordingtotheprincipalsofgravity. Themasswasslidingfrom
paneltopanelpickingupweightandvelocityasitmoved. Theresultwastheavalanche
ofsnow,waterandicethatresultedinacatastrophiccollisionwiththeringbeam. The
rooffabricatthispointwassustainingatremendousweight,andfinallybrokenatits
weakestspotresultinginthefailureofthewesttrianglepanelandtheexplosionofthe
Seikoclock.
Oncethetearoccurred,itwastoolate. Activitiesrecappedbelowweresimplysystem
defaultreactionstothepressurelossduetoaholeintheroof,buthadnoeffectsin
rescuingthedamagedroof. Thereliefsystemhasnowfullyopenedallofthedampers,
thepressurecontrollersignalispositioningtheconstantspeedfandampersforfull
recirculationandthepressureisdecreasing. Bythetimethepressuredropsbelow300
PatheASDfancontrollernowrespondsandtheASDfansbegintospeeduptocounter
thepressuredrop.Thepressurefellbelowthesetpointreachingalowpointof33%or
247Pa. Asthepressuredroppedbelowthesetpoint,computercontrolledASDfans
reactedquicklyandbegantoraisepressure.Thepressurewasonitswaybackuptothe
setpointof300Pawhenthewesttrianglepaneltotallyfailed. Atthispointthe
pressurewasabout37%or277Pa.
Thistechnicalanalysisofthedatasupportstheconclusionthatthenotedaccidental
rapidpressurizationofthebuildingwaslikelytheresultofanovershootinthe
pneumaticdamperpressure/reliefcontrolsystem. Throughoutthehistoryofthis
building,therehavebeenseveralsimilarpressureexcursionsupwardsof100Paabove
setpointundervariouscircumstances.
Itisimportanttonote,duringthehandlingoftheroofincrisis,noStadiumpersonnel
wereflippingdifferentswitchestocausetherapidpressureincrease.
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Equipment
Thecausalanalysisrevealedanumberofdeficienciesthatwererelatedtoequipment.
1.Theabilityofthecontrolroomtoeffectivelyanalyzeandseetheactualroof
conditionswaslessthanadequate. Theexistingcamera(picturebelow)located
outsideontheringbeamofthestadiumwasonlyabletoseeasmallportionofthe
rooffabriclessthan10feetupfromtheringbeam. Consequentlythecontrolroom
operatorwasunabletoobservethecumulativesnowloadingoftheroof.
RingbeamCameraatsection10(TerryFoxPlaza)
Photo#17rightpanview Photo#19 leftpanview Photo#29 centerview
Theabovearephotosoftheactualscreeninthecontrolroomthatoperatorsuseto
viewthecamera.
2.Thecausalanalysisalsohighlightedtheinabilityoftheexistingcontrolsystemto
senseadropinroofelevation. Henceastheroofbegandroppingfrom12:00to
12:30,thecontrolroomoperatorwastotallyunaware.
3.Thecausalanalysisidentifieddirectcause#2asthefailuretoincreasepressureand
effectivelyapplyheat. Twoofthekeyaspectsrelatedtocause#2wereboththe
absenceofapushedautomatedweatheradvisoryservicetonotifyoperatorsof
significantweathereventsthatcouldimpactstadiumoperationsaswellasthetotal
Ringbeam
mounted
camera
Photo#16
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lackofaccesstorealtimeweatherinformation. Bothoftheseserviceshadbeenin
placeinthepast,butwerediscontinued.
4.Thecausalanalysisconductedbythecommitteeidentifiedarapidincreasein
pressureasasecondary,precipitating,contributingeventanditwasafactorinthe
generationofthewesttrianglepanelfailure. Theanalysisoftherapidpressure
increaseidentifiedbothhumanelementsrelatingtocontrolsystemsettingsaswell
ascontrolsysteminteractionsandconflictsastherootcauseoftherapidpressure
increase.
5.Themechanismtolowerthemainspeakerclusterwasnotlocatedinthecontrol
room. Inanemergencysituation,thisdelaystheresponsetimefortheoperatorto
lowerandunweightthespeakertothegroundinanextremeloadingsituation.
6.Whileitisknownthatthesnowmeltingsystemcanhandlevirtuallyanyamountof
snowandkeeptheroofclearwhenoperatedproperly,thecommitteeidentifiedthe
potentialriskofsystemfailuresthatcouldrenderthissnowmeltingsystem
ineffective. Intheearlyeighties,roofhotwaterdispersionsystemwasinstalledto
beusedincontingencysituationsforsnowremovalfromtheroof. Inadditiontothe
hotwatersystem,therewasavarietyofspecializedequipmentstoredinequipment
boxesontheroofthatwasreadyforuseinemergencysituations. Someofthis
equipmentincludedpumpsfordrainingpanelinversionsorponds,emergency
generators,snowblowersandshovelsforringbeamclearing,roofrepairequipment
andmaterialforeffectingtemporaryrepairstotherooffabric.
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CrisisIdentificationandManagement
Fromthemomentthatstaffwereinformedthattheroofwasindistress,therewasa
lackofcoordinationandassessmentoftheproblem. Supervisorsandstaffrantothe
controlroom. Onesupervisorstayedatthefrontofthecontrolroomandimmediately
instructedthecontrolroomoperatortoraisethepressuresetpointto300Paandget
readyforsnowmeltsystemactivation. Theothersupervisorandaworkerwenttothe
backofthecontrolroomtolookattheMagnehelicpressuregauge,believingthatthe
problemwiththeroofmayberelatedtopressure. Oneoftheworkersleftthecontrol
roomtogooutseewhatwasgoingonwiththeroof. Hereturnedtoreportthatthere
werenumerousinvertedroofpanelsnearthespeakercluster. Atthispoint,whenit
wasidentifiedtheroofwasincrisis,multiplepartieswereinvolvedindoingtheirbestto
dealwiththesituationindependentlywithoutengaginginacoordinatedprocess.
Afterseeingthatthestadiumpressuredidnotseemtoberisingtothenewsetpointof
300Pa,asupervisorrandowntothetechshoptoinstructaseniortechnicianto
increasethesystempressureto400Paviahisshopcomputer. Unknowntothe
supervisorandthetechnician,thesettingsforthepressureandreliefcontrollerswere
adjustedforthenewcomputersetpointof300Pa. Consequentlythepressuresetpoint
initiatedbythetechnicianwasnullifiedbythereliefdampercontrolleraction.
Asstaffweredoingtheirbesttodealwithacrisissituation,thereseemedtobealackof
coordinationintheirefforts. Thisclearlyrelatestothefactthatstaffhadnothadany
formalizedtrainingrelatingtocrisismanagement. Therewasnocrisisassessment
proceduretofollow,andconsequentlytheeffectivenessoftheirwellintentioned
actionsanddecisionswasreduced.
Thepoliciesandproceduresdocumentrelatingtoroofinversionwasnotavailableinthe
controlroom. Thisdocumentwasnotalivingdocumentasithadnotbeenupdated
andstaffhadnotbeentrainedinitsapplication.
Whencontrolroomoperatorsreceivedinformationthatsomeroofpanelswere
inverted,ifalivingpoliciesandproceduresmanualwereinplace,theycouldhave
quicklylookeduptheproceduretodealwiththisproblemandidentifiedthatstabilizing
thepressureandkeepingitat300Pawasthebestcourseofaction.
TheactivitiesfortheControlroomoperatorsareroutineforthemajorityofthetime. It
isonlyperiodicallythattheoperatorsexperiencesignificanttechnicaleventsthat
requirefastdecisionmakingandactionontheirparttodealwiththeproblemorcrisis.
Acomparativejobanalogycanbemadetocommercialairlinepilots. Forthemostpart,
thejobofapilotisveryroutineandstructuredinnature. However,whenproblems
arise,pilotsareextremelywelltrainedindealingwithcontingencysituations. Pilotsrely
onspecificproceduresandpolicieswhendealingwithawidevarietyofinflight
emergencies. Theyreceivemandatoryregulartrainingsessionsthatsimulateavast
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arrayofpossibleinflightemergenciesandpracticetheproceduresandactionsto
successfullydealwiththeseemergencies. Acomponentoftheirtrainingfocuseson
crisismanagementandcockpitresourcemanagementwhichtrainsthemtoworkasan
effectiveteamwithinthecockpitenvironment. Consequentlywhenrealemergencies
doarise,pilotsareverysuccessfulatdealingwiththeseemergenciesandmitigating
potentiallossoflifeordamagetoaircraft.
Overtheyearsthestadiumcontrolroomoperatorshaveexperiencedavarietyof
seriousincidentsthathavecompromisedintegrityoftheroof. Theseincidentsincluded
numerouspowerfailures,overloadingoftheroofduetosnowaccumulationandfailure
ofkeycontrolequipment.
Ifthecontrolroomoperatorsandmanagementstaffaretobesuccessfulatdealingwith
thesepotentialcrisissituationsinthefuture,theremustbeongoingtrainingand
refreshersessionsthatgivethemtheskillsnecessarytoworkasateamanddealwith
thecrisiseffectively.
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Policies,ProceduresandTraining
TheInvestigationSubcommitteelookedatdocumentsrelatedtocontrolroompolicies
andproceduresandtraining. Therewerepoliciesandprocedurescoveringthevarious
aspectsofoperationsrelatingtothedaysevent. Withpoliciesandproceduresalready
inplace,itisnecessarytoexaminewhypoliciesandprocedureswerenotfollowed.
Letsfirstlookatthepoliciesandproceduresmanual,theBCPlaceControlRoom
OperationsManualwasdevelopedbackin1987. Overtheyears,whileControlRoom
hadgonethroughupgrades,therehadbeenverylittleupdatesmadetothewritten
manual. Manyofthecontentsinthemanualwerenolongerreflectingthesystemsand
operationsintheControlRoomatthetimeoftheincident. Theneedtoupdatethe
manualhadbeenrecognizedduringanemergencyevacuationexerciseinNovember
2005,sincethenthemainpolicyandproceduremanualforthecontrolroomhadbeen
removedforupdating. Thereweretwokeypprocedurescontainedinthemanualthat
wouldhavebeenmostrelevanttotheroofcrisissituationonthedayoftheincident:
PartialRoofPanelInversion,andTotalRoofPanelInversion. Unfortunatelyboth
procedureswerenotavailableinthecontrolroomastheyhadnotyetbeenrevised.
ThefollowingaretheRoofpanelinversionprocedures:
VIII21 PartialRoofPanelInversion
ControlRoomStaffwillslowlyturnonmorefans. Thenumberoffanstobeturnedonis
dependentonthesizeoftheinversionandisuptothejudgmentofthecontrolroomoperator.
(1) WatchStadiumairpressureverycarefully. DONOToverpressure(i.e.keeppressureunder300Pa.)
(2) Trytostabilizethepressurearound250Pa.(3) ReporttotheDutySupervisorimmediately
VIII22 TotalRoofPanelInversion
(1) ControlRoomStaffwillslowlyturnonallsixteen(16)fans.(2) Watchstadiumairpressureverycarefully. DONOToverpressure (i.e.keep
pressureunder300Pa.)
(3) Trytostabilizethepressurearound250Pa.(4) ControlRoomStaffwillinformalldepartmentstohavealldoorsclosed,especially
bothairlockdoors.
(5) ReporttotheDutySupervisorImmediately
Andforupdatingpurposes,somepartsoftheP&PwereremovedfromtheControl
Roomcopyofthemanual. Oneparticularsectionwhichwasrelevanttotheroof
situation,Howtodealwiththepanelinversion,wasmissinginthemanual.
Itshouldbenotedthatduringtheinvestigation,thecommitteediscoveredthatthese
procedureshadbeendevelopedbasedonthefindingsofadeflationincidentin1982at
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theMetrodomeStadiuminMinneapolis. TheMetrodomeisanairsupportedstadium
verysimilartoB.C.Place. SeeRoofFabricsectionfordetailsoftheMetrodomeincident.
Basedonthelessonslearnedfromthisincident,B.C.PlaceManagementimplemented
theaboveprocedureswhenthestadiumfirstopenedin1983toavoidasimilarmishap.
Overtheyearstheknowledgethatresultedintheadoptionofthesepanelinversion
procedureshadbeenlostbyStadiumPersonnel. Asaresultwhenthestadiumstaff
werefacedwithanoverloadedroofandpanelinversions,theydidnothavethese
procedurestofollow. Iftheseprocedureswerelivingdocuments,thestaffmayhave
avoidedthenaturalinstincttoraiseinternalpressuretocombattheroofloadingand
panelinversion,buttakenthestepsoutlinedintheprocedures.
Itisnotthecommitteesintenttosecondguessthedecisionsmadeinsuchacrisis
situation. However,wewanttoillustratetheimportanceofproperlivingpoliciesand
proceduresandhowtheymayhaveassistedindealingwitharoofincrisis.
AsnowmeltprocedurehadjustbeenintroducedrecentlyonNovember15,2007.
See
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AppendixFEmergencySnowMeltProcedures,Nov15,2006. Theprocedurewason
theinsidecoveroftheP&Pmanualwithastickynoteonitsayingpleaseread. When
askedwhethertheywereawareofthenewprocedure,allControlRoomOperators
interviewedrespondedyes,buttheyalsoindicatedtheywerenotexplainednor
trainedonthenewprocedure.Furthermore,someofthecontrolroomoperatorshad
notevenreceivedtrainingontheoldsnowmeltprocedures. Inaddition,therewasno
seasonalrefresherforallcontrolroompersonnel.
WhileitwasimpliedthattheSnowMeltProcedureswastocombataccumulationson
theroof,butthepurposewasneverclearlystatedforallcontrolroomstafftoknowand
follow. Itappearsanoverarchingoperationalmissionwasamiss: keeptheroofup.
Onmanyoccasions,inspiteofthewrittenpolicythatclearlyindicatesthatifitis
snowing,thebuildingtemperatureistoberaisedtoitsmaximumtemperatureof23
degreesC,theoperatorsfelteitherthat,theydidnothavetheautonomytoexecutethis
policy;orthat,theyhadseenworseweatherconditionsbefore,needtofollowthe
policywasirrelevant.
Thecommitteefoundaculturewherebothstaffandmanagementdidnotfollowthe
writtenprocedures. Theunwrittenproceduresprevailedwhenitcametothe
applicationofheatduringsnowconditions.
Hencethatiswhylackofeffectivelyimplementedpolicies,proceduresandtrainingis
therootcauseoftheroofdeflation.
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CultureIssues
Organizationalcultureplayedamajorroleintheroofdeflationincident. Organizational
cultureisthepersonalityoftheorganization. Theculturecanbeassumptions,beliefs,
practicesandnormsoforganizationmembersandtheirbehaviors.Culturecanbe
difficulttoexpressdistinctly,buteveryoneknowsitsexistence.
AcloselookatthecultureofBCPlacesmaintenanceandoperationsrequiresan
impartialbutcriticalintrospection. Thereseemedtobeanunwrittenoperational
guidelinecostminimization;applyingheatwhenitisabsolutelynecessary;turningon
heatrequiresmanagementapproval. Overtime,controlroomoperatorsdefaultedto
managementdirectionswhenitcametotheapplicationofheat.
Theculturewasnottofollowprocedure,buttoseekpermissiontoapplyheat. Ithas
beenalongpracticethatlittleheatorevennoheatwouldbeapplied,aswehave
weatheredmanyborderlinesnow/sleetconditions. Thispracticeengenderedan
unhealthycultureofcomplacency:leavingdecisionmakingtoothers,henceany
responsibilitiesandconsequencesassociatedwiththedecisionbelongedtosomeone
else. Thiscultureofcomplacencycorrelateswithalowlevelofemployeeengagement
andempowerment. Engagementisthedegreetowhichworkersidentifywith,are
motivatedby,andarewillingtoexpendextraeffortfortheiremployer. Empowerment
iswhenworkersbelievetheyhaveautonomousdecisionmakingforthebestinterest
andbenefitoftheirorganization.
ThefollowingisanexamplethatillustratesthecultureexistedinBCPlace:
Atasnowrelatedeventinlate2006wheretheoperator,believingthathedidnothave
the
authority
to
turn
on
the
heat,
worked
with
staff
and
the
Event
to
get
permission
to
turnontheheat. Thisillustratestheunwrittenpolicyorculturerelatingtotheuseof
heat. Hadtheoperatornotturnedonsomeheatduringthisheavywetsnowfall,itis
likelythattheroofwouldhavebeenincrisisonthatdate. Inspiteofthewrittenpolicy
thatclearlyindicatesthatifitissnowing,thebuildingtemperatureistoberaisedtoits
maximumtemperatureof23degreesC,theoperatorsfeelthattheydonothavethe
autonomytoexecutethispolicy.
InthisdeflationincidentofJanuary507,complacencycontinuedtobeafactoras
personnelinvolvedintheoversightandoperationoftheroofsupportsystemshadlost
theirknowledgeofbasicyetcriticalinformationrelatedtotheroof. Thisincludesissues
suchasloadingandsafetymargins,knowledgegainedbyincidentsatotherair
supportedfacilitiesandkeybehaviorsofairsupportedroofsinavarietyofweather
conditions. Asaresultofthelossknowledge,alongwithverylimitedvisionoftheroof
condition,operatorsmayhavereliedoninstincts.
Itisnotuntilwerecognizethatacultureofcomplacencyexists,thatwecanthenstart
tacklingitthroughacollectivekeeptheroof upmission,effectivepolicies,
proceduresandtraining.
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CausalAnalysisMethodologies
CausalAnalysisistheprocessofidentifyingdirectandindirectcausesoftheroof
deflation. TheCausalanalysisflowedoutofthecausedriversthatwereidentifiedinthe
process
that
built
the
fishbone
diagram.
FishBoneDiagram
TheFishboneorIshikawadiagram,formedthefoundationofcauseandeffectanalysis
conductedbythecommittee. Thediagramshowsthecauseofanevent. Theendresult
oreventwasthedeflationofthestadium. TheanswerstothequestionWhydidthe
roofofB.C.Placedeflatebecamethecausesthatdrovethefinalresultofadeflated
roof. Inallphasesoftheinvestigation,thefishbonediagrambecamethereference
pointortouchstoneforthecommittee.
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CausalEventPathDiagram
Thefollowingisacausaleventpathdiagramthatgivesaroadmapofthepaththatled
toPanelfailureandultimatelydeflationofthestadiumroof.
West PanelFailure
Avalanche
No Roof in
Crisis actionplan!
NoRoof in Crisis
training! NoAssessment
Training
Roof
Overloaded
WithSnow, Ice
&Water
Pressure Increase
To520 Pa.
No awareness or
assessment of roofconditions!
Failure to follow
Pre-snow, Snow meltpolicy
Lack of new proceduretraining re pre-snow
procedure.
Lack ofEffective policy,procedure and
training
CultureUnwritten NO-HEAT Policy
Failure toincrease
pressure andeffecively apply
heat.
No
PhysicalRoofMonitoring
NoPhysical
RoofMonitoring
No
ApplicationOf snow-melt
Start Here
To follow the
Causal Event Path
Lack of
SnowAbatement
CausalAnalysisChart
ThefollowingCausalcharttakesthedirectandindirectcausesandidentifiesour
analysisforeachandthentherecommendedcorrectiveaction.
Definitions:
CausalFactor: Aconditionoraneventthatresultsinaneffect.
DirectCause:Thecausethatdirectlyresultedintheoccurrence.
ContributingCause: Acausethatcontributedtoanoccurrencebutbyitselfwouldnot
havecausedtheOccurrence.
RootCause: Thecausethat,ifcorrected,wouldpreventrecurrenceofthisandsimilar
occurrences.(Doesnotusuallyapplytothisoccurrenceonly,butisgenericinnatureas
itappliestoabroadgroupofpossibleoccurrences).Quiteoftensystemic.
8/8/2019 Joint Health and Safety Committee Report on B.C. Place Stadium roof
46/82
InvestigationReport:BCPlaceRoofDeflationIncidentofJanuary5,200744
DirectCause#1 Causeanalysis RecommendedCorrectiveAction
WestTriangle
PanelFailure.
Avalanche(caused
severetrauma)
(Unprovenbutlikely)
Possiblepreexisting
wear/damage(most
exposedandlikelythe
moststressedpanelon
entireroof)
Havetherooftechnician
conductassessmentofthe
areaimmediatelyadjacent
totheringbeam,theentire
perimeterandunderthe
skirt.Ensurerepairsare
conductedtocorrectany
damagefound.
Haveanapprovedagency
conducttestsonthe
remainingtrianglepanelsin
thebuildingthenmakeany
necessaryrepairsor
replacement.
Trainacrewinemergency
repairandmaintainarepair
planandrepairkitinthe
buildingattheroof.
Conductadetailed
assessmentoftheroofthen
developareplacement
program.
DirectCause#1 Causeanalysis RecommendedCorrectiveAction
Avalanche
Overloadedroof,severe
snow,ice&water
accumulation
Toomuchpressuretoo
fastandthesubsequent
automatedquick
pressuredropbackto
normalsettings.
FailureofEnergrated
controlsystemto
preventconflictwith
pneumaticcontrolled
reliefsystem.
Failuretoconduct
assessmentofroofin
crisis.
Lackofsnow
abatement.
Noroofincrisisaction
plan
Noroofincrisistraining
Updatepressurecontrol
systems
to
prevent
CSV
vs.
ASDoverruns.
Trainstaffandsupervisors
inroofincrisisassessment
andsafereco
Recommended