WorldWorld TunnelTunnel CongressCongress (WTC)(WTC) 20092009
PlanningPlanning ofof DeepDeep SewageSewage TunnelsTunnels inin HongHong KongKong
By Raymond SEIT Drainage Services Department, HKSAR
1 CONTENTCONTENT
BackgroundBackground ofof HarbourHarbour AreaArea TreatmentTreatment SchemeScheme (HATS)(HATS)
RationalesRationales forfor choosingchoosing aa deepdeep tunneltunnel systemsystem
GGroundround investigationinvestigation usingusing thethe specializedspecialized techniquetechnique ofof horizontalhorizontal directionaldirectional coringcoring
WWhyhy wewe havehave selectedselected thethe drill-and-blastdrill-and-blast constructionconstruction methodmethod insteadinstead ofof TBMTBM
CContractontract strategystrategy forfor implementationimplementation ofof thethe constructionconstruction works.works.
2 VictoriaVictoria HarbourHarbour aa MajorMajor AssetAsset forfor thethe HongHong KongKong SARSAR
3 BeforeBefore thethe implementationimplementation ofof thethe HarbourHarbour AreaArea TreatmentTreatment SchemeScheme (HATS)(HATS) StageStage 1,1, sewagesewage dischargeddischarged intointo harbourharbour onlyonly afterafter screeningscreening andand degritting.degritting.
RapidRapid developmentdevelopment andand populationpopulation increaseincrease havehave ledled toto waterwater pollutionpollution problemsproblems
4 StageStage 11 tunnelstunnels (completed)(completed) 2424 kmkm StageStage 22 tunnelstunnels (being(being planned)planned) 2121 kmkm
Stonecutters Island Sewage Treatment Works
Kowloon Stonecutters Island
Hong Kong Island
5 HATS - Sewage Conveyance System
Catchment Flow Coarse Inlet Fine Screens Pumping Screens Station
Discharge Grit to tunnels Removal via shafts To Sewage Treatment Plant
6 HATS Stage 1 - Sewage tunnels system – vertical profile
Stonecutters To Kwa Wan Kwun Tong Island Sewage Treatment Tseung Kwai Tsing Yi work Kwan O Chai Chung Shau Kei Wan Wan
soil
Rock
Kwai ChungMostly Inverted siphons
7 HATS Stage 1 - Stonecutters Island Sewage Treatment Works PreventingPreventing 600600 tonnestonnes ofof sludgesludge fromfrom enteringentering intointo harbourharbour eacheach dayday
Capacity: 170 million cu.m of sewage per day
8 HarbourHarbour AreaArea TreatmentTreatment SchemeScheme StageStage 22 Total tunnel length about 21 km
N
StageStage 11 ++ 2:2: CapacityCapacity toto serveserve populationpopulation ofof overover 66 millionmillion 9 VerticalVertical ProfileProfile ofof HATSHATS StageStage 22 SewageSewage ConveyanceConveyance SystemSystem
10 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Planning considerations: Options and Evaluations Options considered: • Shallow sewers by open trench method • Shallow sewers by trenchless method: e.g pipe jacking, HDD • Mixed ground tunnelling (20-50m) • Deep hard rock tunnelling by TBM or D&B
11 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Factors considered in evaluation of options:
• Constructability • Cost • Environmental and social impact • Programme • Risks • Hydraulic performance • Maintenance
12 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Open Trench Method for sewers
13 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Evaluation - Open trench method: - practically ruled out - unacceptable by the public
- difficult and lengthy utility diversions
- environmental & traffic impacts difficult to mitigate
- strong objections from local bodies and legislature
14 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Evaluation – trenchless method (pipe jacking): • Very few possible locations for jacking pits • Inevitable road opening works -- similar problems as open trench • costs comparable with mix ground / deep hard rock tunnelling for this project’s situation • Programme risks due to likely strong public objections • Experience: trunk sewers by pipe jacking in urban areas: “more than 4 years”
15 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Evaluation – mixed ground tunnelling (20 –50m): • Cost similar to deep hard rock tunnelling • Ground settlement risks exist as for deep hard tunnel • Lack of above ground space for support, for e.g. slurry plant, TBM set up. • Impact on existing/future land development • Conflicts with existing piles from buildings and existing road and railway tunnels
16 WhyWhy useuse thethe DeepDeep TunnelTunnel System?System?
Deep hard rock tunnelling is selected mainly because: 1. Disturbance to public is minimized 2. Conflicts with existing foundations/utilities minimized 3. Acceptance by public 4. Cost and programme: comparable/ better than other options 5. Future land developments not constrained
17 DetailsDetails ofof StageStage 22 SewageSewage TunnelsTunnels byby DrillDrill andand BlastBlast
Total Length of tunnels: 20 km Length of tunnels between shafts: 3.2km to 4.6km Estimated excavated size of tunnel: horse-shoe shape width: 3.5m ~ 4.5m Height: 3.5m ~ 4.5m
Depth: ~ 75m to 165m below sea level 18 CrossCross SectionSection (Oval(Oval Conduits)Conduits) ofof SewageSewage TunnelTunnel
19 TunnelTunnel ConstructionConstruction mostlymostly byby HardHard RockRock TBMTBM inin StageStage 11 20 ProblemsProblems experiencedexperienced inin HATSHATS StageStage 11 • WaterWater InflowInflow
21 ProblemsProblems experiencedexperienced inin HATSHATS StageStage 11 • WaterWater InflowInflow
22 ProblemsProblems experiencedexperienced inin HATSHATS StageStage 11 (Cont.)(Cont.) • SettlementSettlement
480 mm
23 ProblemsProblems experiencedexperienced inin HATSHATS StageStage 11 (Cont.)(Cont.) • ForfeitureForfeiture ofof ContractContract
Original New Arrangement Contract Two construction forfeited Three completion contracts in end contracts 1996 Start: early 1995 Start: mid 1997 Completion: mid Completion: end 1997 2001
24 MeasuresMeasures takentaken inin StageStage 22 tunnels:tunnels:
• EarlyEarly designdesign inputinput fromfrom ExpertsExperts
• AA comprehensivecomprehensive sitesite investigationinvestigation programmeprogramme
• UseUse state-of-the-artstate-of-the-art sitesite investigationinvestigation technologytechnology :: directionaldirectional coringcoring
• CriticalCritical ReviewReview ofof TBMTBM vsvs Drill-&-BlastDrill-&-Blast
ContractContract measuresmeasures • 25 SiteSite InvestigationInvestigation
Rough costs in Euros (based on 1 Euro = 10 HK$)
Total length of directional about 5 km 4.7 Million coring
Number of vertical/inclined about 150 numbers 5.3 Million boreholes
Total length of about 18 km vertical/inclined boreholes
Total cost of ground 10 Million investigation works 26 HorizontalHorizontal DirectionalDirectional CoringCoring
• TheThe firstfirst useuse ofof thisthis technologytechnology inin obtainingobtaining geologicalgeological informationinformation atat suchsuch depthdepth inin HongHong KongKong
27 HorizontalHorizontal DirectionalDirectional CoringCoring TrajectoryTrajectory
Vertical Vertical andBorehole Inclined inclined boreholes Directional Coring TrajectoryBorehole
Directional Coring Trajectory
Sea
Fault Zone or Weak Soil Ground
Bedrock
28 AdvantagesAdvantages ofof usingusing DirectionalDirectional CoringCoring forfor SiteSite InvetigationInvetigation • ContinuousContinuous geologicalgeological informationinformation atat tunneltunnel levellevel cancan bebe obtainedobtained
• TestsTests cancan bebe carriedcarried outout atat tunneltunnel levellevel toto obtainobtain informationinformation forfor controlcontrol ofof groundwatergroundwater ingressingress andand groutinggrouting designdesign
29 HDC
30 SetSet UpUp forfor DirectionalDirectional CoringCoring
31 32 DIRECTIONALDIRECTIONAL BARRELBARREL
DRILL BIT HATS Stage 2A GI Works 33 RockRock CoresCores fromfrom DirectionalDirectional CoringCoring
34 GeologicalGeological InformationInformation
• FaultsFaults andand dykesdykes areare likelylikely toto bebe encounteredencountered atat tunneltunnel depthdepth
• DeepDeep weatheringweathering and/orand/or gougegouge materialsmaterials expectedexpected atat FaultsFaults andand dykesdykes
• FracturedFractured rockrock inin faultfault zoneszones andand areasareas otherother thanthan faultfault zoneszones
• LocalisedLocalised weatheringweathering inin faultfault zoneszones andand dykesdykes
• ExtensiveExtensive treatmenttreatment toto limitlimit waterwater inflowsinflows andand groundground supportssupports requiredrequired 35 CriticalCritical reviewreview onon constructionconstruction method:method: TBMTBM vsvs Drill-and-BlastDrill-and-Blast
36 WhyWhy Drill-and-BlastDrill-and-Blast isis selected:selected:
• VariableVariable GeologicalGeological conditionsconditions –– extensiveextensive groutinggrouting andand groundground supportsupport expected;expected; TBMTBM excavationexcavation ratesrates moremore susceptiblesusceptible toto adverseadverse groundground conditionsconditions
• RelativelyRelatively smallsmall tunneltunnel sizessizes forfor efficientefficient drillingdrilling andand groutinggrouting equipmentequipment forfor TBM.TBM. FullyFully automatedautomated drillingdrilling jumbojumbo availableavailable forfor sizesize range.range. 37 WhyWhichWhyWhich Drill-and-BlastDrill-and-Blast Drill-and-BlastDrill-and-Blast isis isisselected:selected: selectedselected
• ExtensiveExtensive groutinggrouting toto controlcontrol groundwatergroundwater inflowinflow
• LimitedLimited surfacesurface worksworks areaarea isis availableavailable forfor thethe useuse ofof TBMTBM
• FewFew provenproven experiencesexperiences inin TBMTBM tunnellingtunnelling atat suchsuch depthdepth (-160(-160 mPD)mPD)
38 MeasuresMeasures takentaken inin StageStage 22
• RiskRisk ManagementManagement ApproachApproach
– AA comprehensivecomprehensive riskrisk managementmanagement planplan hashas nownow beenbeen developeddeveloped
– RisksRisks areare allocatedallocated toto thethe mostmost appropriateappropriate partiesparties toto dealdeal withwith
39 MeasuresMeasures takentaken inin StageStage 22
• ContractContract StrategyStrategy toto reducereduce riskrisk
– ContractContract FormForm withwith Re-measurementRe-measurement ofof MajorMajor WorksWorks Items:Items: drilling of probe holes, pre-excavation grouting, shotcreting, rock bolts, steel ribs, etc.
– DivideDivide intointo twotwo drill-and-blastdrill-and-blast contractscontracts withwith manageablemanageable sizesize
– RestrictionRestriction thatthat aa contractorcontractor cannotcannot taketake bothboth drill-&-drill-&- blastblast contractscontracts
– RequirementRequirement forfor parentparent companycompany guaranteeguarantee andand aa performanceperformance bondbond 40 MeasuresMeasures takentaken inin StageStage 22 • MechanismMechanism forfor SelectingSelecting thethe ContractorsContractors – PrequalifyPrequalify contractorscontractors whowho areare capablecapable (both(both financiallyfinancially andand technically)technically)
– AA markingmarking schemescheme tailor-madetailor-made forfor thethe tenderingtendering exerciseexercise isis deviseddevised andand mademade knownknown toto allall prequalifiedprequalified tendererstenderers
– AwardAward basedbased onon bothboth technicaltechnical scorescore andand priceprice 41 PublicPublic ConsultationConsultation
• AA continuouscontinuous publicpublic involvementinvolvement approachapproach – ConsultConsult thethe publicpublic andand stakeholdersstakeholders atat variousvarious stagesstages ofof projectproject implementationimplementation
42 HATSHATS StageStage 22 TunnelsTunnels –– CostsCosts
CapitalCapital costcost ofof sewagesewage tunnels:tunnels: ~~ 600600 millionmillion EurosEuros
ProjectProject UpdateUpdate ApprovalApproval ofof EnvironmentalEnvironmental EndEnd 20082008 AssessmentAssessment StudyStudy
CommencementCommencement ofof contractscontracts 2nd2nd halfhalf ofof 20092009
CompletionCompletion ofof thethe wholewhole systemsystem 20142014
43 ThankThank you!you!