HAWAIKIHDDOCEANOUTFALLOIL/GAS|SEWER|STORMWATER|POWER|WATER|TELCO

LOCATION CoogeeNSW

CLIENT HawaikiSubmarineCable

PIPE Steelconduit,103mmID

GEOLOGY Hawkesburysandstone&sand

LENGTH 1,300metres

TECHNIQUE HDD

PROJECTOVERVIEWAftercompletinganumberofsuccessfuloceanoutfallprojects,UEAwasawardeda1,300metredesignandconstructHDDoceanoutfall andbeachmanhole constructioncontractbyHawaiki SubmarineCable.TheprojectatlargeinvolvesanewsubmarinecablelinkingAustraliaandNewZealandtoHawaiiandmainlandUnited States, which will help eliminate the distance between all Pacific communities and boost socio-economic development through the provision of broadband access.With a design capacity of 42 Tbps,Hawaikiisnowcurrentlythehighestcross-sectionalcapacitylinkbetweenAustralia,NewZealandandtheUnited States. As a carrier-neutral cable system, Hawaiki will usher in a new era of internationalconnectivity,andwillbenefitbothbusinessesandconsumersacrossthePacificregion.LOCATIONTheHawaikicable landingsite iswithinSydney’sSouthernCableProtectionZone(CPZ)atCoogeeBeach.ThissitewasselectedasitisthefurthestdistancefromexistingsubmarinecablesanditisalsotheclosestlandingpointtotheCableLandingStation(CLS)inAlexandria.

Fivepossiblelaunchsiteoptionswereoriginallytendered.ThefinalchosenlocationattherearofTrenerryReservewasselectedbasedon its lower impactonresidentialandcommercialproperties,moreefficientaccesstothelandbasedroute,bettervehicularaccessthanothersitesandtheabilitytoinstallastraighterHDDboretoloweranticipatedcablehaultensions.BOREDESIGNAsapartoftheHDDdesigncomponent,UEAwasresponsibleforboththelandbasedsurveyoftherouteandthereviewofthenearshoresurveydata,toensurethattheboredesignwouldmeetallenvironmentalapprovalsandfitwithintheconstraintsplacedbytheclientandapprovingorganisations.

UEA’sin-houseteamundertookgeotechnicalinvestigation,servicelocationworksandpotholingofexistingassets. Thisworkhelped to confirma suitable entry anglewithin the entry site, and also to avoid a live1600mmhanddugsewertunnel.Theboredesignallowedforsufficientclearancetotheclifffaceandnear

shoremarineenvironments,eliminatingtheriskofdrillingfluidlosstotheformation.Thedesignalsometthe requirements of being located at least 100metres away from all rock reefs and exitingwithin sandground conditions. The installed conduitwas designed to be over 60metres deep as it crossed the cliffedge and maintain 30 metres of cover below the seabed before punching out of the sea floor atapproximately32metreswaterdepth,1,300metresoffshore.APPROVALSUEAwasresponsible forgainingallnecessarypermitsandapprovals includingthemanagementof trafficand community relations. A detailed Construction Environmental Management Plan and CommunityLiaison Planwere implementedwhich included council notifications, resident letterbox drops, individuallocalbusinessconsultationsandtheestablishmentofacommunity informationstall toanswerquestionsandprovidedetailsabouttheproject.Trafficmanagementwasespeciallydifficultonthisprojectduetothenarrow and congested Eastern suburbs streets, as well as the requirement tomobilise 13 semi-trailers,multipleoversizeloadsupto3.6metreswideandthe300tonnecapacitydrillrigtotheseasidesuburb.TECHNICALDETAILSTheHDDentrycompoundwassetuptoreduceasmuchnoiseimpactaspossibletoresidents,includingtheinstallationofa4.2metrehighnoiseabatementwallandstrategicplacementofequipmentonsite.Onceestablished,drillingworkscommencedwithinrock,whicheliminatedtheneedforcasingoftheborehole.Pilotbore trackingutilised thenewDigiTrak FalconF5 system, allowing faster setupandprogressionaswell as the ability to test the new equipment within virgin sandstone ground conditions in an area ofminimalbackgroundinterference.

Pilot boring was completed via walkover tracking to Ch200 prior to tripping out to change over to theParaTrack2wire line steering system.ThenewDCI F5Falconperformedbetter thanexpected, achieving29.1metredepthbelowsurface -deeper thanUEAhaseverpreviouscompletedwalkover tracking.Pilotboringcontinuedwithanumberofsurveyshotstakenbeforethesteeringtoolpassedthecliffedge,outoftherangeofthebeaconandonitswaytowardstheexitpoint1,100metresfurtherouttosea.

Drillingworksprogressedwellwithanaverageof130metresdrilledper11hourdaytimeshiftinthe80mPasandstone,sixdaysperweek.Groundconditionswereconsistentforthedurationofthebore,andthepilotborewascompletedinasinglepasswithouttheneedtotripoutdrillrods.AHawaikiteammembersaidoftheprojectthat“completingthe1,300metreborewithoutasinglewirelinefaultortripwasagreatresultandatestamenttothecrewonsitefollowingalldueprocessesandthequalityoftheirwork”.

Inorder tomeet thestrictenvironmentalcontrolsandapprovals requiredtoworkwithin thenear-shoremarineenvironment,thedrillingfluidprogramwaschangedtobiodegradablexanthanandfreshwaterforthepunchoutintotheseafloorsothatnobentoniteclaymaterialenteredtheocean.COMPLETIONAtthecompletionoftheunderbore,UEA’sdivingcrewconfirmedthespecificlocationofthepunchoutontheseafloorandalsoconfirmedthatall requiredseparationtorockreefswasmaintained.Thepilotborewas established by survey to have reached the seafloor at the correct locationwith the drill head only500mmnorthoftheproposedexitlocation.Drillrodsandtoolingwerethenwithdrawnfromtheboreholeto allow for the steel drill conduit installation and custom completion piece, in anticipation for cableinstallation. The roping and proving of the installed conduit was successfully undertaken without issue,leaving a 16mm draw wire in place ready for the cable hauling works. All equipment was demobilisedfollowingthesuccessfulinstallationoftheunderboreconduit,thecastin-situbeachmanholeconstructionwascompletedandtheparksurfacewasrestored.