san juan creek outfall junction structure …...apr 23, 2014 · the san juan creek outfall system...

SAN JUAN CREEK OUTFALL JUNCTION STRUCTURE REHABILITATION

Technical Memorandum

Junction Structure Rehabilitation

B&V PROJECT NO. 181812

PREPARED FOR

South Orange County Wastewater Authority April, 2014

®

®

©Black & Veatch Holding Company 2012. A

ll rights reserved.

South Orange County Wastewater Authority | SAN JUAN CREEK OUTFALL JUNCTION STRUCTURE REHABILITATION

BLACK & VEATCH i

JunctionStructureRehabilitation B&VProject:181812 April23,2014

Preparedby: M.Jayakumar,P.E. MarkLowe,S.E. ReviewedBy: JonathanHay,P.E. Submittedby: SteveFoellmi,P.E.,ProjectManager VictorTsai,P.E.,EngineeringManager

TableofRevisions

Revision Author Date Approved Date Description

0 M.Jayakumar/MarkLowe

04/16/2014 JonHay 04/23/2014 FinalSubmittal


BLACK & VEATCH | TABLE OF CONTENTS I

Table of Contents ExecutiveSummary........................................................................................................................................ES‐11.0 ProjectOverview.................................................................................................................................1‐1

1.1 PurposeofthisMemorandum........................................................................................................1‐11.2 FacilityDescription.............................................................................................................................1‐11.3 ProjectRequirements.........................................................................................................................1‐4

2.0 ReviewofOceanOutfallEvaluation..............................................................................................2‐13.0 ReviewofDudekConstructionReviewReport........................................................................3‐14.0 ReviewofHydraulicCapacityEvaluation...................................................................................4‐15.0 DevelopmentofAlternatives..........................................................................................................5‐1

5.1 JunctionStructureExternalRehabilitationAlternatrives...................................................5‐25.2 JunctionStructureInternalRehabilitationAlternatrives...................................................5‐55.3 JunctionStructureConstructionAccessAlternatives.........................................................5‐105.4 OutfallPipePermanentAccessAlternatives..........................................................................5‐10

6.0 ScreeningofAlternatives.................................................................................................................6‐16.1 ExternalReinforcementAlternatives..........................................................................................6‐16.2 InternalReinforcementAlternatives...........................................................................................6‐16.3 ConstructionAccessAlternatives..................................................................................................6‐36.4 PermanentAccessAlternatives.....................................................................................................6‐3

7.0 ConstructabilityReview....................................................................................................................7‐17.1 JunctionStructureRehabilitation.................................................................................................7‐1

7.1.1 ConstructionAccessandStagingArea.....................................................................7‐17.1.2 ConstructionSequenceforAlternatives1B‐2and1B‐5...................................7‐27.1.3 ConstructionSequenceforAlternative1C.............................................................7‐3

8.0 ConstructionCostEstimatesandSchedule................................................................................8‐18.1 ConstrcutionCostEstimatesforAlternatives1B‐2and1B‐5...........................................8‐18.2 ConstructionCostEstimatesforAlternative1C......................................................................8‐18.3 ConstructionCostEstimatesforPermanentAccessHatch................................................8‐28.4 ConstructionScheduleforAlternatives1B‐2and1B‐5.......................................................8‐28.5 ConstructionScheduleforAlternatives1C...............................................................................8‐38.6 ConstructionScheduleforPermanentAccessHatch............................................................8‐4

9.0 Recommendations..............................................................................................................................9‐19.1 JunctionStructureRehabilitationRecommendation............................................................9‐1


BLACK & VEATCH | TABLE OF CONTENTS II

LIST OF TABLES TableES‐1:SummaryofAlternatives.......................................................................................................................ES‐2TableES‐2:JunctionStructureRehabilitationEvaluation...............................................................................ES‐4Table4‐1:HydraulicGradeLineatJunctionStructure........................................................................................4‐1Table5‐1:SummaryofAlternatives............................................................................................................................5‐1Table5‐2JunctionStructureExternalRehabilitationAlternativesComparison......................................5‐3Table5‐3JunctionStructureInternalRehabilitationAlternatives................................................................5‐6Table5‐4JunctionStructureRehabilitationConstructionAccessAlternatives......................................5‐11Table5‐5OutfallPipePermanentAccessAlternatives.....................................................................................5‐11Table6‐1:PreliminaryRankingSummaryfortheRehabilitationAlternatives........................................6‐3Table6‐2:PreliminaryRankingSummaryforPermanentAccessAlternatives.......................................6‐5Table8‐1:EstimatedConstructionCostforAlternatives1B‐2and1B‐5....................................................8‐1Table8‐2:EstimatedConstructionCostforAlternative1C...............................................................................8‐2Table9‐1:JunctionStructureRehabilitationEvaluation....................................................................................9‐1

LIST OF FIGURES Figure1‐1:SOCWAFacilityMap(extractedfromSOCWA10YearPlan)....................................................1‐2Figure1‐2:LandSectionofOutfallPipe(nearJunctionStructure)................................................................1‐3Figure1‐3:LandSectionofOutfallPipe(nearSurgeStructure).....................................................................1‐4Figure4‐1:FlowvsHGLatJunctionStructure........................................................................................................4‐2Figure4‐2:FlowvsHGL,RiserElevation..................................................................................................................4‐2Figure5‐1:JunctionStructureExternalRehabilitationAlternatives.............................................................5‐4Figure5‐2:JunctionStructureInternalRehabilitationAlternatives‐1........................................................5‐8Figure5‐3:JunctionStructureInternalRehabilitationAlternatives‐2........................................................5‐9Figure5‐4:OutfallPipePermanentAccessAlternatives..................................................................................5‐12Figure5‐5:RecordDrawingofExistingSurgeTowerStructureModifications......................................5‐13Figure5‐6:TypicalPipeCoupling...............................................................................................................................5‐14Figure5‐7:TypicalInternalPipeSeal.......................................................................................................................5‐14Figure5‐8:InflatableExternalPipePlug.................................................................................................................5‐14Figure7‐1:ConstructionAccessandStagingArea................................................................................................7‐2Figure8‐1:PreliminaryConstructionScheduleforAlternatives1B‐2and1B‐5.....................................8‐3Figure8‐2:PreliminaryConstructionScheduleforAlternative1C................................................................8‐3


BLACK & VEATCH | ACRONYMS AND ABBREVIATIONS LIST i

Acronyms and Abbreviations List ACI American Concrete Institute

ACOE Army Corps of Engineers

CBC California Building Code

CCC California Coastal Commission

CFRP carbon fiber reinforced polymer

CIPP cured in place pipe

CRR Construction Review Report

CSC City of San Clemente

EIR Environmental Impact Report

EPA Environmental Protection Agency

FRP Fiber reinforced plastic

JBL J.B.Latham Treatment Plant

HDPE High density poly ethylene

HGL hydraulic grade line

MNWD Moulton Niguel Water District

mgd million gallons a day

MSL mean sea level

OOE Ocean Outfall Evaluation

OOSE Ocean Outfall Structural Evaluation

Project San Juan Creek Outfall Junction Structure Rehabilitation Project

RCP reinforced concrete pipe

ROV remote operated vehicle

RWQCB Regional Water Quality Control Board

SMWD Santa Margarita Water District

SOCWA South Orange County Wastewater Authority

SS Stainless steel

WRP Water Reclamation Plant

WWTP Wastewater Treatment Plant


BLACK & VEATCH | EXECUTIVE SUMMARY ES‐1

Executive Summary SouthOrangeCountyWastewaterAuthority(SOCWA)engagedBlack&VeatchtodevelopandevaluatealternativesforrehabilitatingtheSanJuanCreekOutfallSystemJunctionStructureandtoprovideapermanentaccesstotheoutfallsystem.ThisExecutiveSummaryhighlightstheinformationpresentedinthisTechnicalMemorandum.

ProjectOverview(Section1)

TheSanJuanCreekOutfallsystemdischargestreatedeffluentfromfourSOCWAreclamationplantstotheocean.Thelandandmarinesectionsoftheoutfallsystemwereconstructedin1979andconsistof57‐inchreinforcedconcretepipe(RCP)extending10,550feetintotheocean.Theoutfallsystemincludesa10footdiameterJunctionStructureseparatingthelandandmarinesections.In2006,SOCWAengagedCarolloEngineerstoevaluatethehydrauliccapacityandpressureratingoftheoutfallsystem.Thisevaluationestablishedamaximumhydrauliccapacityof85milliongallonsaday(mgd)formostpartsoftheoutfallsystemwiththeexceptionoftheJunctionStructure,whichwasfoundtohavestructuralweaknessatthebottomportionofconcretewalls.Carollorecommendedreinforcementofthebottom12feetofthestructuretoathicknessof12‐inches.CarolloEngineersdevelopedadesignforexternallyreinforcingthestructure’slowerwalls.SOCWAengagedDudektoreviewthedesign.DudekraisedconcernsaboutconstructabilityofthealternativedevelopedbyCarolloEngineers.SOCWAengagedBlack&VeatchtoreviewthepreviousreportsanddevelopfeasiblealternativesfortherehabilitationoftheJunctionStructure.Theassignmentalsoincludesdevelopmentofadesignforpermanentaccesstotheoutfallsystem.

ReviewofOceanOutfallEvaluation(Section2)

Black&VeatchreviewedtheJunctionStructurepartofthe“OceanOutfallStructuralEvaluation”(OOSE)FinalReportpreparedbyCarolloEngineers,datedMarch2007,forcompliancewithgeneralengineeringpracticesandmethodologiesusedforstructuralassessment.ThemaximumwaterpressureloadswithintheJunctionStructureweredeterminedforboththecracked‐concreteandsteel‐yieldconditions.Black&Veatchrecommendthattheinternalpressuresbelimitedtobelowtheconditionwheretheconcretebeginstocracktoensurethelongevityofservicelifeforthestructure.BasedontheOOSE,thiswouldcorrespondtoaHGLof11.00.Also,therecommendationtoreinforcethebottom12feetoftheJunctionStructuretohandlethemaximumheadpossiblefortheoutfallstructureisconsistentwithgeneralengineeringpractices.

ReviewofDudekConstructionReviewReport(Section3)

Black&VeatchreviewedandagreeswithrecommendationsoftheConstructionReviewReport(CRR)preparedbyDudek,datedMarch2008,forgeneralconformancewithstandardstructuralengineeringandconstructionpractices.TheCRRreviewedthealternativedevelopedbyCarolloEngineersandbroughtoutthedifficultiesinimplementingtheproposedalternativeandsuggestedthedevelopmentofinternalrehabilitationalternativesfortheJunctionStructure.DudekalsosuggestedamajorupwardrevisiontotheconstructioncostestimateofCarolloEngineers.

ReviewofHydraulicCapacityEvaluation(Section4)



Black&VeatchusedtheHydraulicCapacityEvaluationconductedbySOCWAinJune2006toestablishthehydraulicgradelineattheJunctionStructure.ThiswouldbeusedforestimatingtheheightoftherisertobeusedattheJunctionStructureduringconstruction.Correspondingtoaflowof20mgd,thehydraulicgradeline(HGL)attheJunctionStructurewouldbe9.00aboveMSLandtherisershouldhaveaheightof11.00feetaboveMSL.

DevelopmentofAlternatives(Section5)

AlternativesweredevelopedforJunctionStructurerehabilitation,constructionaccess,andpermanentaccess.TableES‐1summarizesthealternativesconsidered.DetailedfiguresarepresentedinSection5asreferencedinthetable.

Table ES‐1: Summary of Alternatives

ALTERNATIVE DESCRIPTION

A. External Junction Structure Rehabilitation Alternatives

1A‐1 – Concrete Reinforcement External concrete reinforcement of existing Junction Structure. Dowelling of rebars to the existing structure would be required (alternative developed by Carollo) (Reference Figure 5‐1).

1A‐2 – CFRP Reinforcement External carbon fiber reinforced polymer (CFRP) reinforcement of existing Junction Structure (Reference Figure 5‐1).

1A‐3 – Wire Wrapped Concrete Reinforcement

External wire wrapped reinforcement of existing Junction Structure (Reference Figure 5‐1).

B. Internal Junction Structure Rehabilitation Alternatives

1B‐1 – Internal Stainless Steel Reinforcement

Install internal stainless steel (SS) pipe liner on both sides and around the Junction Structure at the bottom using underwater construction. Space between liner and outfall pipe will be grouted. Access from the top of Junction Structure. No bypass pumping is required (Reference Figure 5‐2).

1B‐2 – Internal Stainless Steel Pipe Liner with Internal Seals

Install internal SS pipe liner through the Junction Structure using underwater construction. Space between liner and outfall pipe will be grouted. Junction structure could be filled with light weight cellular concrete. Access from the top of Junction Structure. No bypass pumping is required (Reference Figure 5‐2).

1B‐3 – Internal Stainless Steel Pipe Liner Pipe with Internal Seals

Install internal SS pipe liner through the Junction Structure using underwater construction. Space between liner and outfall pipe will be grouted. Junction Structure could be filled with concrete. Access from the metering port upstream of the Junction Structure. No Bypass pumping is required (Reference Figure 5‐2).

1B‐4 – Internal Reinforcement with Bypass Pumping

Install internal SS pipe liner through the Junction Structure in the dry using bypass pumping. Access could be either from the top of Junction Structure or from the metering port (Reference Figure 5‐2).

1B‐5 – Internal Stainless Steel Pipe Liner with External Seals

Install internal SS pipe liner through the Junction Structure with external pipe seals on both sides, inflate the seals, dewater the Junction Structure, and do the reinforcement in the dry. Access through Junction Structure. No bypass pumping (Reference Figure 5‐3).

1B‐6 – Cured in Place Pipe Install High density poly ethylene (HDPE) or fiber reinforced plastic (FRP) pipe using cured in place pipe (CIPP) technology.

1C – Internal Structural Reinforcement

Internal structural reinforcement after installing a temporary through sleeve through the Junction Structure with seals on either side, dewatering the Junction Structure, and then providing internal reinforcing (Reference Figure




5‐3).

1D –Demolish and Replace Existing Structure

Replace existing structure with a new structure at Doheny State Park.

C. Construction Access Alternatives

2A – Access at Junction Structure

Provide access at the Junction Structure. Provide a temporary riser over the Junction Structure to avoid spills of effluent and also to keep seawater away.

2B – Access at Metering Structure

Provide access at the Metering Structure by installing a riser.

2C – Access at Surge Structure Provide access at the JB Latham Plant or old Surge Tower.

2D – New Access at Doheny State Park

Provide new access structure at Doheny State Park.

D. Permanent Access Alternatives


Provide watertight access hatch at existing Junction Structure (Reference Figure 5‐4).


Provide access at the Metering Structure by installing a riser (Reference Figure 5‐4).

3C – Access at Surge Structure Provide access at the JB Latham Plant or old Surge Tower (Reference Figure 5‐4).


Provide new access structure at Doheny State Park.

Details,advantages,disadvantages,andpermitrequirementsareevaluatedindetailandincludedinSection5.

ScreeningofAlternatives(Section6)

AsdescribedinSection6,apreliminaryscreeningofthealternativeswasconductedbasedontechnicalfeasibility,temporaryconstructionimpacts,constructability,constructionaccess,constructionschedule,plantshutdown(needforstorageofeffluent),beachuseimpacts,andpermitting.Allfactorswereweightedequally,andahigherscoreisconsideredfavorable.Constructioncostwasnotconsideredfortheinitialscreening.Externalreinforcementalternatives1A‐1,1A‐2,and1A‐3hadthesamelimitationsastheCarollodesign,andhencethesealternativeswerenotrecommendedforfurtherconsideration.Internalrehabilitationalternatives1B‐1,1B‐3,1B‐4,1B‐6,and1Dhadfatalissuesandwerenotrecommendedforfurtherconsideration.1B‐2,1B‐5,and1Cwererecommendedforfurtherconsideration.

Forconstructionaccess,onlytheaccessattheJunctionStructurewasfoundfeasible.Forpermanentaccess,aftercarefulconsideration,theaccessattheoldSurgeTowerStructurewasfoundtobethemostappropriatealternative.Sincetheexisting36‐inchaccesshatchattheSurgeTowercouldbeusedforaccess,noadditionalworkisrequired.

ConstructabilityReview(Section7)

Thethreeinternalrehabilitationalternatives(1B‐2,1B‐5,and1C)werefurtherevaluatedforconstructionaccessandstagingarea,andconstructionsequence.Allthreealternativesarefeasible



withvaryingdegreesofdifficulty.Alternatives1B‐2and1B‐5arelessdifficulttoconstructcomparedtoalternative1C.Alternative1Cwouldresultinlimitedworkingareaduetotheinternalbypass.Allthreealternativeswouldrequireshuttingdowntheflowforunderwaterwork.

CostEstimatesandConstructionSchedule(Section8)

Preliminaryopinionsofconstructioncostandconstructionschedulesweredevelopedforthethreerehabilitationalternatives.Thecostestimatesarebasedoncurrentrates,andescalationforoneyearisbuiltintotheestimate.Thecostestimatesareonlyforconstruction.AnEIRwouldberequiredpriortostartingtheconstructionwork.ThecostforEIR,detaileddesign,andconstructionphaseservicesarenotincludedinthecostestimate.

ForAlternatives1B‐2and1B‐5,theestimatedconstructioncostis$305,900.

ForAlternative1C,theestimatedconstructioncostis$260,400.

Alternatives1B‐2and1B‐5wouldrequireapproximately10weeksandAlternative1Cwouldrequireapproximately13weeks.ForthepermanentaccesstotheOutfallSystem,theexisting36‐inchhatchattheSurgetowerStructurecouldbeusedwithoutanyadditionalworkandhencewouldnotrequireanyanyadditionalwork.

Recommendations(Section9)

AfinalevaluationoftheJunctionStructureRehabilitationwasconducted.ResultsareshowninTableES‐2.

Table ES‐2: Junction Structure Rehabilitation Evaluation

EVALUATION CRITERIA INTERNAL REINFORCEMENT ALTERNATIVES

1B‐2 1B‐5 1C

Technical Feasibility 4 5 4

Temporary Construction Impacts 4 4 4

Constructability 4 4 1

Construction Access 3 3 3

Construction Schedule 4 4 3

Plant Shutdown 3 3 3

Beach Use Impacts 3 3 3

Permitting 3 3 3

Construction Cost 3 3 4

Total Score 31 32 28

Black & Veatch Ranking 2 1 3

Ranking: A score of 1to5 has been assigned for each evaluation criteria; a higher score represents a better alternative based on the listed evaluation criteria

BasedontheBlack&Veatchevaluation,Alternative1B‐5isrecommended.Acombinationofalternatives1B‐2and1B‐5consistingofinternalpipesealsandexternalpipeseals,atthediscretionoftheContractorwouldprovidebettersafetyduringconstruction.TheconstructionaccesswouldbeattheJunctionStructureforallthealternativesconsidered.Forthepermanentaccesstothe



OutfallSystem,theexisting36‐inchhatchattheSurgeTowerStructurecouldbeusedwithoutanyfurthermodification.


BLACK & VEATCH | PROJECT OVERVIEW 1‐1

1.0 Project Overview ThissectionprovidesabriefdescriptionofthebackgroundoftheSanJuanCreekJunctionStructureRehabilitationProject(Project)andscopeofreviewprovidedbyBlack&Veatch.

1.1 PURPOSE OF THIS MEMORANDUM

Thisshortmemorandumisdevelopedwiththefollowingpurposes:

ProvideresultsofBlack&Veatchreviewofpastreports

DevelopalternativesfortheJunctionStructureRehabilitation

Developalternativesforaccessforconstruction

DevelopalternativesforpermanentaccesstoOutfallSystem

Pre‐screenthealternativesandshortlistamaximumofthreealternativesforeachcategoryforfurtherevaluation

1.2 FACILITY DESCRIPTION

TheSanJuanCreekOutfallsystemdischargestreatedeffluentfromfourSouthOrangeCountyWastewaterAuthority(SOCWA)reclamationplantslistedbelow.

CityofSanClementeWaterReclamationPlant(CSCWRP)

J.B.LathamTreatmentPlant(JBL)

MoultonNiguelWaterDistrictPlant3A(MNWDPlant3AWWTP)

SantaMargaritaWaterDistrictChiquitaWaterReclamationPlant(SMWDChiquitaWRP)

Thelandandmarinesectionsoftheoutfallsystemwereconstructedin1979.Theoutfallpipeconsistsof57‐inchreinforcedconcretepipe(RCP)andextendsapproximately10,550feetintothePacificOcean.ThemajorstructuresalongtheoutfallpipeincludeaJunctionStructurelocatedatthebeach,ameteringstructurelocatedwithintheDohenyStateParkapproximately485feetupstreamoftheJunctionStructure,andasurgetowerstructurelocatedapproximately1,285feetupstreamoftheJunctionStructure.Thediffusersectionsattheoceanendoftheoutfalldischargesatadepthbetween94.5to97.5feetbelowmeansealevel.

Figure1‐1showsanoverallviewoftheabovelistedfacilities.



Figure 1‐1: SOCWA Facility Map (extracted from SOCWA 10 Year Plan)

TheJunctionStructureisa10footdiameterreinforcedconcretestructurethatformstheinterfacebetweenthelandandmarinesectionsoftheoutfallsystem.Theoriginalconstructionincludedatopcoverwithafourfootsquare,boltedsteelaccesshatch.ThetopcoveroftheJunctionStructurewasmodifiedintheearly1990stoincreasethemaximuminternalhydrostaticpressurebyaddingapermanentconcreteslaboverthetop.



Figures1‐2and1‐3showthelandsectionoftheoutfallpipealignmentwithprominentstructuresmarkedup.

Figure 1‐2: Land Section of Outfall Pipe (near Junction Structure)



Figure 1‐3: Land Section of Outfall Pipe (near Surge Structure)

In2006,SOCWAengagedCarolloEngineerstoevaluatethehydrauliccapacityandpressureratingoftheoutfallsystem.Thisevaluationestablishedamaximumhydrauliccapacityof85milliongallonsaday(mgd)formostpartsoftheoutfallsystemwiththeexceptionbeingtheJunctionStructure.TheJunctionStructurewasfoundtohavestructuralweaknessatthebottomportionofconcretewallsandwouldrequirereinforcementtoincreaseitscapacitytosupport85mgdload.CarolloEngineersdevelopedandproposedadesignforexternallyreinforcingthestructure’slowerwallstoaheightof12feetabovethebottom.SOCWAengagedDudektoreviewtheCarolloevaluationtoprovidefeasibleconstructionmeansandmethodsthatwouldbeassociatedwiththiswork.Black&VeatchreviewedtheCarolloevaluationandtheDudekreview.

1.3 PROJECT REQUIREMENTS

Thescopeofreviewandcurrentprojectobjectivesincludedinthisreportarelistedbelow:

Reviewavailableinformationincludingoutfalldrawings,previousrehabilitationdesignsandreports,operatingrecords,andotherpertinentinformation.

Conductageotechnicalreviewoftheoriginaloutfallboringsandotherrelevantdata.

PresentaminimumofthreeexternalreinforcementalternativesfortheJunctionStructure,oneofwhichistobethealternativedevelopedandproposedbyCarolloEngineers.

Presentaminimumofthreeinternalreinforcementalternatives.



Evaluatethealternativesintermsofconstructability,regulatoryissues,constructionschedule,constructability,andcostforconstruction.

Presentaminimumofthreepermanentaccessconceptstotheoutfallpipeforfutureaccessforinspectionandrepair.Evaluatethepermanentaccessconceptsdeveloped.

Acomprehensivegeotechnicalreviewisnotincludedinthescopeofthisreport.


BLACK & VEATCH | REVIEW OF OCEAN OUTFALL EVALUATION 2‐1

2.0 Review of Ocean Outfall Evaluation Black&Veatchreviewedthe“OceanOutfallStructuralEvaluation”(OOSE)FinalReportpreparedbyCarolloEngineers,datedMarch2007forcompliancewithgeneralengineeringpracticesandmethodologiesusedforstructuralassessment.TheOOSEprovidesresultsandconclusionsfromanalysesperformedonboththeexistingSurgeTowerandJunctionStructure.ThepurposeoftheOOSEwastoestablishthemaximumhydraulicgradeline(HGL)orinternalpressureloadthatcanbeappliedwithinthesystemwithoutexceedingthestructuralcapacityoftheweakestelementoftheoutfallsystem.Toaccomplishthisobjective,theOOSEgeneratedafiniteelementmodelofeachstructureandappliedinternalpressureloadstothemodels.Theresultingstresseswithinthestructurewerereviewedtoidentifythefirstfailuremodeofthestructurewhichwouldlimittheoverallcapacityofthestructure.

Finiteelementanalysiswasusedtohelpdeterminehowappliedloadsaredistributedwithinthestructureanditsusefulnessincreaseswiththecomplexityofthestructure.TheJunctionStructure,ingeneral,isasimplecirculartank,butcomplexitiesareintroducedbythelargepipeopeningsandtheuncertaintyofconnectionstiffnessatthefoundation.TheOOSEhasaddressedthesecomplexitiesofthestructureasfollows:

Provideafinermeshpatternaroundopeningswithinthefiniteelementmodeltoprovideamorerefineddistributionofstressesintheseareas.

Provideanalysesforbothfixed‐baseandpinned‐basemodelstoenvelopetherangeoffixitythatmayexistatthebaseofwalls.

TheappliedloadsusedintheanalyseswereincompliancewithAmericanConcreteInstitute(ACI)350‐01,whichincludesadurabilityfactorthateffectivelylimitsthetensilestressintherebartomitigateconcretecrackformation.Reductionofconcretecracksrelatesdirectlytoextendingservicelifeanddoesnotprovideinformationregardingshort‐termultimatestructuralcapacityassociatedwithanimminentstructuralfailurecondition.Astheinternalpressureloadsincrease,thestressesinthewallsreachapointwheretheconcretecracks.Aftercracksintheconcretehaveappeared,theconcretemaintainsitsintegrityandcontinuestoprovidesupportbyonlyutilizingthereinforcingsteeltensilestrength,whichprovidessupportuptothesteelyieldpoint.ThedesignprovisionsofACI350‐01limitthestructuralstresseswellbelowthesteelyieldpointtoensurethestructuremaintainsitsexpectedservicelifeof50years.

ThemaximumwaterpressureloadswithintheJunctionStructureweredeterminedforboththecracked‐concreteandsteel‐yieldconditions.Werecommendtheinternalpressuresbelimitedtobelowthecracked‐concreteconditions(+11.00aboveMeanSeaLevel(MSL))toensurethelongevityofservicelifeforthestructure.

Hydrodynamicloadsproducedbyseismicactivitywereassumedtobeinsignificantandnon‐controllingduetothesmalldiameterdimensionofthetankandonlyhydrostaticloadswereusedintheanalyses.TheassumptionseemsreasonablegiventhatCaliforniaBuildingCode(CBC)2013requiresthesloshingloadsbeincludedinstructuraldesignfortanksthathavediameterslargerthan20feet.


BLACK & VEATCH | REVIEW OF OCEAN OUTFALL EVALUATION 2‐2

Ingeneral,theengineeringmethodsandanalysesusedandpresentedwithintheOOSEareconsistentwithconventionalandacceptedstructuraldesignpractices.

TheexternalstructuralreinforcementalternativedevelopedbyCarolloEngineersisevaluatedasoneoftherehabilitationalternativesinasubsequentsection.


BLACK & VEATCH | REVIEW OF DUDEK CONSTRUCTION REVIEW REPORT 3‐1

3.0 Review of Dudek Construction Review Report Black&Veatchreviewedthe“ConstructionReviewReport”(CRR)preparedbyDudek,datedMarch2008,forgeneralconformancewithstandardstructuralengineeringandconstructionpractices.TheopinionsandproposedconstructionmethodspresentedintheCRRareinregardstoworkattheexistingJunctionStructureasdescribedintheCarolloOOSEreport.ThepurposeoftheCRRwastoprovidefeasibleconstructabilityinformationandpracticableworkstrategiesandapproachesregardingtheimplementationandexecutionoftheproposedreinforcementworkpresentedintheOOSE.

ThefollowingmainconcernswerepresentedintheCRRandhaveBlack&Veatchconcurrence:

TheCRRidentifiestheprimaryconstructionchallengeforthisworkasdevelopinganeffectiveandsafeshoringanddewateringsystemthatwouldfacilitatetherequiredexcavationaroundtheJunctionStructure.TheCCRrecommendsconsiderationofanalternativeapproach,whererepairworkwouldbeperformedwithinthestructure,avoidingtheneedforexcavationandshoringofthesurroundingsoil.

Thecurrentconditionoftheconcreteisrecommendedtobeverifiedbynon‐destructivetestingtoensuretheconcretehasadequatestrengthandsoundnesstoensurethatthedrilledholesforthedowelsdonotexcessivelydamagetheexistingconcrete.

Proposedaccesstotheconstructionsiteistoonarrowforequipmenttopass.Itisrecommendedtolocateconstructionaccessthroughcampsites#37and#38locatedwithintheDohenyStatePark.

TheJunctionStructuremayrelyontheexistingsoiloverburdendeadweighttoprovideresistancetohydrostaticupliftforces.Excavationandremovalofsurroundingsoilscouldincreasethebuoyancyanddisruptthestabilityofthestructure.

Noiselevelfromtemporarypowergeneratorsanticipatedduringconstructionwouldbeaseriousnuisanceandwouldrequiresomeformofsoundattenuation.

Theaboveconcernsaremajorandcriticalissueswithanyworkplanthatincludesexcavation,shoring,anddewatering.ResolutionoftheseproblemswouldberequiredpriortogoingforwardwiththeproposedexteriorreinforcementoftheJunctionStructure.

Black&VeatchrecommendsthatasimilarconstructabilityreviewasdonebyDudekbeperformedfortheselectedrehabilitationalternative.

Ingeneral,thefindingsandrecommendationspresentedwithintheCRRareconsistentwithconventionalandacceptedconstructionandengineeringpractices.


BLACK & VEATCH | REVIEW OF HYDRAULIC CAPACITY EVALUATION 4‐1

4.0 Review of Hydraulic Capacity Evaluation InJune2006,SOCWAcompletedaHydraulicCapacityEvaluation.ThestudyrecommendedaManning’s“n”valueof0.0142fortheoutfallpipe.Thestudyalsoconcludedthat,basedonpaststudies,theoutfallsystemdoesnothaveanysurgeissues.

ForaccomplishingtheJunctionStructurerehabilitation,atemporaryriserpipemustbeinstalledovertheexistingJunctionStructuretopreventanyspilltothebeachduringtheconstructionperiod.Toestablishtheheightoftheriser,therecommended“n”valuewillbeused.A2footfreeboardisrecommendedbetweenthehydraulicgradelineandthetopoftheriser.

Theoutfallsystemhasatotallengthof11,816feettotheendoftheoutfallsystemfromtheJunctionStructure.Table4‐1providestheHGLattheJunctionStructurefordifferentflowratesassumingahightideelevationof6.00.

Table 4‐1: Hydraulic Grade Line at Junction Structure

FLOW FRICTION LOSS

HGL RISER

ELEVATION

MGD CFS FT

0 0 0 6 8

10 15.47 0.65 6.65 8.65

20 30.94 2.62 8.62 10.62

30 46.42 5.89 11.89 13.89

40 61.89 10.46 16.46 18.46

50 77.36 16.35 22.35 24.35

60 92.83 23.54 29.54 31.54

70 108.31 32.04 38.04 40.04

80 123.78 41.85 47.85 49.85

85 131.51 47.25 53.25 55.25

90 139.25 52.97 58.97 60.97

Figure4‐1showstherelationshipbetweentheflowandtheHGLattheJunctionStructure.



Figure 4‐1: Flow vs HGL at Junction Structure

AnenlargedviewofthelowerflowrangeswithrecommendedrisertopelevationisincludedinFigure4‐2.

Figure 4‐2: Flow vs HGL, Riser Elevation

0

10

20

30

40

50

60

70

0 20 40 60 80 100

HGL

Flow,mgd

FlowvsHGLatJunctionStructure

FlowvsHGL

0

5

10

15

20

25

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

HGL,RiserElevation

Flow,mgd

FlowvsHGL,RiserHeightatJunctionStructure(LowerRanges)

FlowvsHGLFlowvsRiserElevation



Theriserelevationshallbeselectedtomatchthemaximumanticipatedflowduringtheproposed

constructionwindow.Basedonavailableinformation,typicalflowsareinthe15to20mgd.


BLACK & VEATCH | DEVELOPMENT OF ALTERNATIVES 5‐1

5.0 Development of Alternatives Table5‐1summarizesthealternativesconsidered.

Table 5‐1: Summary of Alternatives


E. External Junction Structure Rehabilitation Alternatives

1A‐1 – Concrete Reinforcement

External Concrete Reinforcement of existing Junction Structure. Dowelling of rebars to the existing structure would be required (alternative developed by Carollo) (Reference Figure 5‐1)

1A‐2 – CFRP Reinforcement

External CFRP Reinforcement of existing Junction Structure (Reference Figure 5‐1).

1A‐3 – Wire Wrapped Concrete Reinforcement

External wire wrapped reinforcement of existing Junction Structure (Reference Figure 5‐1).

F. Internal Junction Structure Rehabilitation Alternatives

1B‐1 – Internal Stainless Steel Reinforcement

Install Internal Stainless Steel Pipe Liner on both sides and around the Junction Structure at the bottom using underwater construction. During underwater construction, the flow has to be reduced sufficiently to keep the velocities within acceptable limits to the specialty underwater construction company. Details are to be worked out during detailed design. This is applicable to all all alternatives requiring underwater work. Space between liner and outfall pipe will be grouted. Access from the top of Junction Structure. No bypass pumping is required (Reference Figure 5‐2).

1B‐2 – Internal Stainless Steel Liner Pipe with Internal Seals

Install Internal Stainless Steel Pipe Liner through the Junction Structure using underwater construction. Space between liner and outfall pipe will be grouted. Junction structure could be filled with light weight cellular concrete or left as is for future use as an access point. Since the length of the smaller diameter liner is very small compared to the overall outfall pipe length, the impact on the hydraulic performance is insignificant. Construction access will be from the top of the Junction Structure. No bypass pumping is required (Reference Figure 5‐2).

1B‐3 – Internal Stainless Steel Liner Pipe with Internal Seals

Install Internal Stainless Steel Pipe Liner through the Junction Structure using underwater construction. Space between liner and outfall pipe will be grouted. Junction Structure could be filled with concrete. Access from the metering port upstream of the Junction Structure. No Bypass pumping is required (Reference Figure 5‐2).


Install Internal Stainless Steel Pipe Liner through the Junction Structure in the dry using bypass pumping. Access could be either from the top of Junction Structure or from the metering port (Reference Figure 5‐2).

1B‐5 – Internal Stainless Steel Liner Pipe with External Seals

Install Internal Stainless Steel Pipe Liner through the Junction Structure with external pipe seals on both sides, inflate the seals, dewater the Junction Structure, and do the reinforcement in the dry. Access through Junction Structure. No bypass pumping (Reference Figure 5‐3).

1B‐6 – Cured in Place Pipe Install HDPE or FRP pipe using CIPP (Cured in Place Pipe) technology

1C – Internal Structural Reinforcement

Internal Structural Reinforcement after installing a temporary through sleeve through the Junction Structure with seals on either side, dewatering the Junction Structure, and then providing internal reinforcing (Reference Figure 5‐3).


Replace existing Structure with a new Box at Doheny State Park.



G. Construction Access Alternatives


Provide Access at the Junction Structure. Provide a Temporary Riser over the Junction Structure to avoid spills of Effluent and also to keep seawater away.


Provide Access at the Metering Structure by installing a riser.

2C – Access at Surge Structure

Provide Access at the JB Latham Plant or Old Surge Tower.


New Access Structure at Doheny State Park.

H. Permanent Access Alternatives


Watertight Access Hatch at existing Junction Structure (Reference Figure 5‐4).


Provide Access at the Metering Structure by installing a riser (Reference Figure 5‐4).


Provide Access at the JB Latham Plant or Old Surge Tower (Reference Figure 5‐4).


New Access Structure at Doheny State Park.

Preliminaryevaluationofeachofthealternativesisprovidedbelow.

5.1 JUNCTION STRUCTURE EXTERNAL REHABILITATION ALTERNATRIVES Table5‐2providesacomparisonofthethreeJunctionStructureExternalRehabilitation

alternatives.Figure5‐1providesdetailsofthethreealternatives.



Table 5‐2 Junction Structure External Rehabilitation Alternatives Comparison

ALTERNATIVE CONSTRUCTION ACCESS

TECHNICAL CHALLENGES PERMITS FROM PROS CONS RISK CONSTRUCTABILITY PUBLIC IMPACTS

1A‐1 – External Concrete Reinforcement

No access required into the structure, but all work would happen at the beach around the Junction Structure.

• Majorconstructionatthebeach

• DeepexcavationtoexposeJunctionStructure

• Dewateringrequired• Treatmentsystemforpumpedwater(fromdewatering)

• Cofferdammayberequiredtoprotectworkarea

• Rebardowellingtoexistingconcretecylinderwouldberequired

• CACoastalCommission(CCC)

• ArmyCorpsofEngineers(ACOE)

• StateParks• FishandGame• EnvironmentalProtectionAgency(EPA)(RegionalWaterQualityControlBoard(RWQCB)),and

• EnvironmentalImpactReport(EIR)

• Betterqualitycontrol,sincealltheworksareexternal

• Couldworkonregularshiftsor24/7,ifnecessary

• Nointerruptiontotheeffluentflow

• Nounderwaterwork

• Deepexcavationatthebeachwithassociatedissueslikedewatering,closureofbeachetc.

• PotentialinstabilitytotheJunctionStructurefoundation

• Possibly,highercostofconstruction

• Dowellingofanchorsrequiredontheexistingstructure

• Shoringconstructionrequired• Treatmentofdewateringflowsrequired

• Potentialspillatbeach

• PotentialcollapseofJunctionStructure

• Specialcarerequiredtoavoidstructuralcollapse

• Deepexcavation• Constructionatbeach

• Shutdownofpartofthebeachduringconstruction

1A‐2 – External CFRP Reinforcement






• CCC• ACOE• StateParks• FishandGame• EPARWQCB,and• EIR




• Nounderwaterwork• Nodowellingrequiredontheexistingstructure

• Smalleraccessareaaroundthestructurewouldbesufficient








• Deepexcavation• Constructionatbeach


1A‐3 – External Wire Wrapped Concrete Reinforcement






• CCC• ACOE• StateParks• FishandGame• EPARWQCB,and• EIR




• Nounderwaterwork• Nodowellingrequiredontheexistingstructure




• Largeraccessareaaroundthestructurewouldberequired





• Deepexcavation

• Constructionatbeach




5.2 JUNCTION STRUCTURE INTERNAL REHABILITATION ALTERNATRIVES Table5‐3providesacomparisonoftheJunctionStructureInternalRehabilitationalternatives.

Figures5‐2and5‐3providedetailsofthealternatives.



Table 5‐3 Junction Structure Internal Rehabilitation Alternatives

ALTERNATIVE CONSTRUCTION ACCESS LOCATION


1B‐1 – Internal Stainless Steel Reinforcement (Reference Figure 5‐2)

• JunctionStructure • Underwaterconstruction• Workispossibleonlyduringlowflowperiods,requiringmultipleentriesintotheoutfallpipe

• Formingthelinertosuittheshelvingisachallengeanddifficulttoinstall

• CCC• ACOE• StateParks• EPARWQCB

• Noexcavation,associateddewateringordischargesrequired

• Noriskofdamagingtheexistingstructure

• Workcanproceedonlyduringlowflowperiods,resultinginlongerconstructionperiod

• ExtensivecoordinationrequiredbetweenPlantOperationsandContractor

• Possibly,highercostofconstructionduetomultiplediverentries

• Risksassociatedwithdiving

• Accesstothebeachrequiredduringconstruction.Thisrequiresextensivecoordinationwiththepublicandauthorities.

• EntrytotheJunctionStructurewillbeatthebeach

1B‐2 – Internal Stainless Steel Liner Pipe with Internal Seals (Reference Figure 5‐2)











1B‐3 – Internal Stainless Steel Liner Pipe with Internal Seals (Reference Figure 5‐2)

• MeteringStructure(485feetupstreamofJunctionStructure)

• Underwaterconstruction• Workispossibleonlyduringlowflowperiods,requiringmultipleentriesintotheoutfallpipe

• Materialshavetobemovedunderwaterforalongdistance

• Moretimewouldbespentbythediverstoreachtheworkspot

• StateParks• EPARWQCB







• Nomajorissues.• Disruptionofmeteringandsampling.

• Aportionoftheparkwouldhavetobeisolatedfortheentry


• JunctionStructure • Constructionofbypasspumping. • CCC• ACOE• StateParks• FishandGame• EPARWQCB• EIR

• JunctionStructurerehabilitationcouldbedoneinthedry,withoutanytimerestrictions

• BypasspumpingwouldrequireconnectiontotheoutfallatalocationdownstreamoftheJunctionStructure(closertothebeach)

• Bypasspumpingarrangementwouldbeveryexpensive,especiallyiflinestopsareused

• Risksassociatedwithdeepexcavationatthebeach


• Partsoftheparkandbeachwouldhavetobeisolatedduringconstruction

1B‐5 – Internal Stainless Steel Liner Pipe with External Seals (Reference Figure 5‐3)





• Reinforcementwouldbedoneinthedry.






• EntrytotheJunctionStructurewouldbeatthebeach



ALTERNATIVE CONSTRUCTION ACCESS LOCATION


1B‐6 – Cured in Place Pipe

• NewAccesshatchupstreamofJunctionStructure

• Flowdiversionisrequiredforthismethod(itcanonlybedoneinthedry)

• Ameanstopressurizetheinsertisrequired

• Anaccesspointisrequired,typically,fromanupstreamlocation




• Flowdiversionrequired• Upstreamaccesspointrequired

• LongershutdownoftheOutfallSystemneededforimplementation.

• Notafeasiblemethodwithoutflowdiversion

• Forflowdiversion,workinthebeachwouldberequired

1C – Internal Structural Reinforcement (Reference Figure 5‐3)

• JunctionStructure • Underwaterconstruction• Underwaterworkispossibleonlyduringlowflowperiods,requiringmultipleentriesintotheoutfallpipe

• TheshelvinginsidetheJunctionStructuremayhavetoberemovedforsoundstructuralreinforcement

• Rebarshavetobedowelledintotheexistingstructure/pipe






• Reducedcrosssectionatthelocationofrepair

• RemovingtheshelvingmaydamagetheJunctionStructure


• Underwaterconcreteworkwouldrequireadditionalcareandqualitycontrol.



• JunctionStructure • Abypasswouldberequiredbetweenthenewboxstructureandtoapointdownstreamoftheexistingstructure

• Majorconstructionforthebypasspiperequiringdeepexcavation

• CCC• ACOE• StateParks• FishandGame• EPARWQCB• EIR

• Exceptforthetie‐intotheexistingoutfallpipe,allotherworkcouldbedoneindependently

• Nounderwaterwork


• Muchhighercostforconstruction

• BypasspumpingwouldrequireconnectiontotheoutfallatalocationdownstreamoftheJunctionStructure(closertothebeach)

• Bypasspumpingarrangementwouldbeveryexpensive,especiallyiflinestopsareused

• Risksassociatedwithdeepexcavationatthebeach


• Aportionoftheparkandbeachwouldhavetobeisolatedforconstruction

10'-0"

12'-0"

EXIST 57"OUTFALL PIPE

EXISTING JUNCTIONSTRUCTURE

NEW STAINLESSSTEEL LINERDESIGNED FOROPERATING PRESSURE

EXIST 57"OUTFALLPIPE

NEW STAINLESSSTEEL LINER

ANCHOR BOLTS(TYP)

A-

10'-0"

EXIST 57"OUTFALL PIPE

PIPE COUPLINGS(STRAUB, TEEKWAY,ROMAC OR EQUAL)

EXIST 57"OUTFALLPIPE

48" STAINLESSSTEEL LINER

LIGHT WEIGHTCELLULAR CONCRETE

EXIST JUNCTIONSTRUCTURE

INTERNAL PIPESEALS (WEKO,HYDRATECH, OR EQUAL)

ANCHOR BOLTS(TYP)

B-

36" ACCESSHATCH

B181812F

IG

-L

SA

VE

D:

PLO

TT

ED

:F

B181812F

IG

-L

FIGURE 5-2

JUNCTION STRUCTURE REHABILITATION

INTERNAL REINFORCEMENT ALTERNATIVES

SECTION A

ALTERNATIVE 1B-1

SECTION B

ALTERNATIVE 1B-2, 1B-3, 1B-4

PLAN PLAN



5.3 JUNCTION STRUCTURE CONSTRUCTION ACCESS ALTERNATIVES Table5‐4providesacomparisonoftheJunctionStructureConstructionAccessalternatives.

5.4 OUTFALL PIPE PERMANENT ACCESS ALTERNATIVES Table5‐5providesacomparisonoftheOutfallPipePermanentAccessalternatives.

Figure5‐4providesdetailsoftheproposedpermanentaccessalternatives.Figure5‐5istherecorddrawingofexistingSurgeStructureModifications.Theexisting36‐inchaccesshatchwithairvalvescouldbeusedforaccessingtheOutfallSystem.Basedonourinitialdiscussionswithfirmsexperiencedinlaunchingandretrievingremotelyoperatedvehicles,a36‐inchaccesshatchisadequate.



Table 5‐4 Junction Structure Rehabilitation Construction Access Alternatives

ALTERNATIVE TECHNICAL CHALLENGES PERMITS FROM PROS CONS RISK CONSTRUCTABILITY PUBLIC IMPACTS


• Nomajorchallenges • CCC• ACOE• StateParks• EPARWQCB• FishandGame

• Accessisveryclosetotheworkarea

• Accesstothebeachrequiresextensivecoordinationwiththepublicandauthorities.

• Minimal • Accesstothebeachrequiresextensivecoordinationwiththepublicandauthorities.

• Aportionofthebeachwouldhavetobeisolatedforconstruction


• NewaccesshatchrequiredatMeteringStructure

• Materialwouldnotfitthroughthenewaccesshatch

• Traveldistancewouldreduceproductivity

• CCC• ACOE• StateParks• EPARWQCB• FishandGame

• Accesscouldbecreatedbyhottappingoutfallpipe

• Noworkatthebeach

• Accessisawayfromworkarea,requiringmoreunderwatertraveltotheworkarea.

• Moreunderwatertravelrequiredduringconstruction.

• Theadditionalunderwatertravelwouldaffectproductivity.

• Aportionoftheparkwouldhavetobeisolatedforconstruction

2C – Access at Surge Tower Structure

• NewlargeraccesshatchrequiredatSurgeTowerStructure

• Materialmaynotfitthroughthenewaccesshatch

• Traveldistancewouldsubstantiallyreduceproductivity

• EPARWQCB • Accesscouldbecreatedbyhottappingoutfallpipe





• None


• TraveldistancetotheJunctionStructurewouldreduceproductivity

• StateParks• EPARWQCB






• Aportionoftheparkwouldhavetobeisolatedforconstruction.

Table 5‐5 Outfall Pipe Permanent Access Alternatives

ALTERNATIVE TECHNICAL CHALLENGES PERMITS FROM PROS CONS RISK CONSTRUCTABILITY PUBLIC IMPACTS


No major challenges • CCC• ACOE• StateParks• EPARWQCB

• Easyaccesstoconstruct • Accesswouldbeatthebeach,whichwouldbeadisturbancetothepublic.

• Minimal • Accesstothebeachrequiresextensivecoordinationwiththepublicandauthorities.

• Aportionofthebeachwouldhavetobeisolatedforconstructionimpactingbeachusebypublic.


No major challenges • CCC• StateParks• EPARWQCB



• Theexistingflowmeterhastobereplacedwithadifferenttypesuitableforinstallingattheriser

• Minimal • TheMeteringStructureisverycongestedmakingitdifficulttoinstalltheaccesshatchwithoutrelocatingtheexistingfacilities.

• Aportionoftheparkwouldhavetobeisolatedforconstruction


None. Existing 36‐inch access hatch is adequate for access.

• None. • Nopermitsrequired• Noworkatthebeach

• Accessisfurtherawayfromtheoutfallpipeaffectingthereach

• None. • None. • None


Significant effort required to construct





• Minimal • Nomajorissues • Aportionoftheparkwouldhavetobeisolatedforconstruction.

jay37537

Text Box

Figure 5-5: Record Drawing of Existing Surge Tower Structure Modifications



Figures 5‐6, 5‐7, and 5‐8 provide details of some of the components that would be used in the design.

Figure 5‐6: Typical Pipe Coupling

Figure 5‐7: Typical Internal Pipe Seal

Figure 5‐8: Inflatable External Pipe Plug


BLACK & VEATCH | SCREENING OF ALTERNATIVES 6‐1

6.0 Screening of Alternatives Thissectionprovidesaninitialscreeningofthealternativesdevelopedintheprevioussection.The

mainconsiderationsusedfortheinitialscreeningarelistedbelow:

Technicalfeasibility

Temporaryconstructionimpacts

Constructability

Constructionaccess

Constructionschedule

Plantshutdown(needforstorageofeffluent)

Beachuseimpacts,and

Permitting

Constructioncostisnotconsideredfortheinitialscreening.Summaryevaluationsforeachofthealternativesareprovidedbelow.

6.1 EXTERNAL REINFORCEMENT ALTERNATIVES Alternatives1A‐1,1A‐2,and1A‐3(ReferenceFigure5‐1)areforreinforcingtheJunctionStructureexternallyusingdifferenttechnologiestoinclude:conventionalconcretereinforcement,

CFRPreinforcement,andwirewrapconcretereinforcement.Forallthreealternatives,excavation

oftheJunctionStructuretothebottomwouldberequired.ExcavationneartheJunctionStructureposesamajorconcernofcausinginstabilitytothestructure.Inadditiontotheexcavation

challenges,therewouldbeextensivedewateringequipmentandpowerusagerequiredforthe

treatmentanddisposalofthesignificantquantitiesofwaterresultingfrompumping.AnextensiveEIRandpermittingprocesswouldberequiredforimplementingthesealternatives.These

alternativescarryahighlevelofriskandexposuretoadditionalcoststhataredifficulttopredict

andthereforearenotrecommended.

6.2 INTERNAL REINFORCEMENT ALTERNATIVES Alternative1B‐1(ReferenceFigure5‐2)isdifficulttoimplementduetotheirregularcontourof

theJunctionStructureatthebottom,mainlyduetotheshelving.Theshelving,inallprobability,is

madeofmassconcreteandhencemaynotprovidetherequiredstrength.Recommendnottopursuethisalternativeanyfurther.

Alternative1B‐2(ReferenceFigure5‐2)requiresaccessthroughtheJunctionStructure.Thepipe

linersegmentscouldbejoinedtogetherusingplainendedcouplingslikeStraubCoupling,Teekay,orRomaccouplings.Oncethetwopipesegmentsareinstalledinplaceandattachedtotheoutfall

pipe,internalpipesealsshallbeinstalledatthepipeends.Thenthemiddlesegmentwillbe

installedandjoinedusingplainendedcouplings.ThiswillsealthewaterflowtotheJunctionStructure.TheJunctionStructurecouldbedewateredandfurtherworkcouldbedoneinthedry.

Thisisafeasiblealternative.



Alternative1B‐3(ReferenceFigure5‐2)issimilartoAlternative1B‐2,exceptthatthematerials

willbemovedthroughanaccesshatchtobebuiltattheMeteringVault.Thedifficultyinthisalternativeisconnectingthepiecestogether.Therearenotmanyestablishedinternaljoining

mechanismsinthemarket.Alsothemaximumsizeofindividualpieceswillbelimitedbytheaccess

hatchsize.Thisalternativewillrequiremoredivingtimewithassociatedrisksandcosts.Overallthisalternativepresentsmorechallengesthanbenefits,andhenceisnotrecommendedandnot

consideredanyfurther.

Alternative1B‐4(ReferenceFigure5‐2)requiresbypasspumping,whichwouldcostalotmore,aswellaslongerconstructionduration.Notrecommendedandconsideredanyfurther.

Alternative1B‐5(ReferenceFigure5‐3)requiresaccessthroughtheJunctionStructure.Thepipe

linersegmentscouldbejoinedtogetherusingplainendedcouplingslikeStraub,Teekay,orRomaccouplings.Thepipesegmentsgettinginsertedintotheoutfallpipeswillbeprovidedwith

mechanicalinflatablesealsasshown,andwillbeattachedtotheJunctionStructureusing

temporaryattachments(detailstobedevelopedlater).Thesealswouldbeinflatedafterthemiddlesegmentisconnected.Oncethesealsareinflated,theoutfallpipewillbeisolatedfromtheJunction

Structure.Atthistime,theJunctionStructurecouldbedewateredandtheinsertedpipelinescanbe

fixedinplaceandtheJunctionStructurefilledwithlightweightconcrete.Thisisafeasiblealternative.

Alternative1B‐6isaCIPPprocedure,andwouldrequireadryenvironmentandalaunchingpit,

preferablyfromanupstreamlocationandareceivingpitatadownstreamlocation.BotharedifficultfortheJunctionStructurerehabilitation.Thisalternativeisnotfeasibleandnotconsidered

anyfurther.

Alternative1C(ReferenceFigure5‐3)willtemporarilyisolatetheJunctionStructureusingaflexiblehosewithinflatablesealsattheends.ThehosewillbeattachedtotheJunctionStructure

(detailstobedeveloped).Whenthesealsareinflated,theJunctionStructurewouldbetotally

isolatedfromtheoutfallpipe.TheJunctionStructurewouldbedewateredandreinforcedinternally.Afterthereinforcementiscompletedandtested,thetemporaryflexiblehosewouldberemoved

andtheJunctionStructureclosedatthetop.A24‐inchdiameterhoseisproposedtohandlethe

normalflowrateof15to17mgd.Thisisafeasiblealternative,butisadifficultfromaconstructabilitypointofview.Afterinstallingthe24‐inchbypass,verylimitedspacewillbe

availableforworkingwithintheJunctionStructure.

Alternative1DwillrequireabypasspipingconnectingtoalocationdownstreamoftheexistingJunctionStructure.Thisalternativehasallthedisadvantageslikedeepexcavation,dewatering,

workingalocationclosertothebeachthantheJunctionStructure.Thisalternativeisnot

recommendedandwillnotbepursuedanyfurther.

ApreliminaryevaluationmatrixisincludedasTable6‐1below.



Table 6‐1: Preliminary Ranking Summary for the Rehabilitation Alternatives

EVALUATION CRITERIA

EXTERNAL REINFORCEMENT ALTERNATIVES

INTERNAL REINFORCEMENT ALTERNATIVES

1A‐1 1A‐2 1A‐3 1B‐2 1B‐5 1C

Technical Feasibility 2 2 2 4 5 4

Temporary Construction Impacts 1 1 1 4 4 4

Constructability 2 3 3 4 4 1

Construction Access 1 1 1 3 3 3

Construction Schedule 3 4 3 4 4 3

Plant Shutdown 5 5 5 3 3 3

Beach Use Impacts 1 1 1 3 3 3

Permitting 2 2 2 3 3 3

Total Score 17 19 18 28 29 24

B&V Ranking 6 4 5 2 1 3

Ranking: A score of 1‐5 has been assigned for each evaluation criteria; a higher score represents a better

alternative based on the listed evaluation criteria

ALT 1A‐1 (Carollo Design) – Baseline

Based on the above discussion, Alternatives 1B‐2, 1B‐5, and 1C are recommended for further

consideration.

6.3 CONSTRUCTION ACCESS ALTERNATIVES Constructionaccessnecessarytoperformtheworkassociatedwitheachrehabilitationalternative

seemstobelimitedeventhoughatotaloffouraccessalternativeshavebeenpresented,onlyone

accessapproachappearstobefeasible.Sinceconstructionworkmustbecompletedduringliveconditions(whentheoutfallpipeisactiveandfullofwater)andtherearenotexistingaccess

structuresadjacenttheJunctionStructure,itseemsunfeasibletodeliverconstructionmaterialsto

theJunctionStructurefromaremotelocationalongtheoutfallpipe.Basedontheexistingconstraints,theonlyfeasibleconstructionaccesslocationisfromthetopoftheJunctionStructure

(Alternative2A).Theheightofthetemporaryaccessriserwouldbedeterminedbasedonthe

highestexpectedflowrateduringtheconstructionperiod.

6.4 PERMANENT ACCESS ALTERNATIVES

Forfuturepermanentaccess,atotaloffouralternativeswereevaluated.Basedonpreliminarydiscussionwithadivingresourcescompany,aminimumaccesshatchsizeof36‐inchdiameterwouldberequiredforinsertingaRemotelyOperatedVehicle(ROV)forfutureinspections.However,alargerhatchopeningwouldallowinsertingalargerROV,whichcouldaccommodateadditionaltoolsandoffermoreoptionsforfuturemaintenanceandrepairs.Hence,forthisstudy,anaccesshatchofminimum36‐inchdiameterisconsidered.



Alternative3AistoprovideapermanentaccessattheJunctionStructure.Thedisadvantageofthisalternativeisthatforfutureaccess,aportionofthepublicbeachwouldneedtobeshutdown.CoordinationandapprovalwiththeStateParkandCaliforniaCoastalCommissionwouldberequired.Theapprovalswouldrequirealotofplanning,coordination,andeffort.Duetotheselimitations,thisalternativeisnotrecommended.

Alternative3BistoprovideapermanentaccessattheexistingMeteringStructure.Themeteringstructureincludesaflowmetering,asamplingsystemcompletewithacompositesampler,asumppumpsystem,pressureinstruments,andaventilationsystem.Themanufactureroftheexistingflowmeterconfirmedthatanaccesshatchattheproximityoftheflowmetersensorwoulddrasticallyreducetheaccuracyoftheflowmeter.Thespaceistight,andincludesotheritems(pressuretransmitterandgauge,samplingpointetc.),whichwouldhavetoberelocated.Thisalternativewouldavoidtheneedforworkatthebeachtoprovideconstructionaccess,butconsideringthetightspaceandneedforreplacingtheflowmeter,thisalternativeisnotrecommended.Extendingthemeteringstructurewasalsoevaluated,butthiswouldresultinalargestructuretoprovideanunobstructedstraightlengthoftentimesthediameterupstreamoftheflowmeter.Thisalternativeisnotrecommendedforfurtherconsideration.

Alternative3CistoprovideapermanentaccessattheexistingSurgeTowerStructureorJ.B.LathamPlant.Itisfeasibletoprovidehatchesatbothlocations.Thisalternativewouldavoidtheneedtoworkatthebeachforaccess.

TheSurgeTowerStructureislocatedbythesideofSanJuanCreek.ThegroundlevelattheSurgeTowerStructurelocationisapproximatelyEl.15.00,whichishigherthanthenormalwaterelevationof11.00correspondingto20mgd.Thiswouldallowopeningtheaccesshatch(withadequateprotectionandsafetymeasures)evenatnormalflowrates.Thislocationisthemostpreferredlocationforapermanentaccesshatch.TheSurgeTowerStructurehasanexisting36‐inchaccesshatchwhichisadequateforfutureaccess.Nofurtherworkisrequired.TheonlycautionistopreciselycontroltheROVwhenpassingthroughtheMeteringStructure.Theinsertiontypeflowsensorsatthislocationwouldhaveslightprojectionwithinthepipe.

AsimilaraccesshatchcouldbeprovidedatJBLdirectlyonthepipeline,butthedownstreamsurgetowerstructurewouldmakenavigationdifficult.Thislocationisnotrecommended.

Alternative3DistoprovideapermanentaccessatalocationbetweentheexistingMeteringStructureandJunctionStructurewithintheDohenyStatePark.Thiswouldavoidtheneedforrelocatingtheflowmeter,pressureinstruments,andsamplingpointattheMeteringStructure.Thisalternativewouldavoidtheneedforworkatthebeachtoprovidepermanentaccessinthefuture.Thedrawbacksare:

AdditionalrealestatehastobeleasedfromtheStateParks.

Hottappingtotheoutfallpipeisrequiredtoinstalltheriser.

TheriserhastoextendatleasttoEL.11.00tofacilitateopeningthehatchwithnormalflowrates.

Largeareawouldberequiredduringconstructionasstagingarea.



Constructionhastobeplannedtohappenduringoff‐seasontoavoiddisturbancetothecampers

Forthesereasons,thisalternativenotpursuedfurther.

ApreliminaryrelativerankingofthealternativesisincludedasTable6‐2below:

Table 6‐2: Preliminary Ranking Summary for Permanent Access Alternatives

EVALUATION CRITERIA ALT 3A ALT 3B ALT 3C ALT 3D

Technical Feasibility 5 2 5 5

Structural Integrity 5 5 5 5

Temporary Construction Impacts 5 4 4 3

Constructability 5 3 5 3

Travel Distance 5 4 3 4

Beach Use Impacts 1 5 5 5

Permitting 1 3 4 3

Total Score 27 26 31 28

B&V Ranking 3 4 1 2

Ranking: A score of 1‐5 has been assigned for each evaluation criteria; a higher score represents a better alternative based on the listed evaluation criteria

Basedontheforegoingdiscussion,thefollowingalternativeswouldbeevaluatedfurtherforconstructabilityandcostestimates.

JunctionStructureRehabilitationAlternatives1B‐2,1B‐5,and1C

ConstructionAccessAlternative2A,and

PermanentAccessAlternatives3C(atSurgeTowerStructure)


BLACK & VEATCH | CONSTRUCTABILITY REVIEW 7‐1

7.0 Constructability Review Thissectionreviewsthefeasibilityofconstructionfortheshortlistedalternatives.

7.1 JUNCTION STRUCTURE REHABILITATION

ThefollowingthreealternativeswereshortlistedforJunctionStructureRehabilitation:

Alternative1B‐2:

Alternative1B‐5:

Alternative1C:

Alternatives1B‐2and1B‐5wouldresultinthesameendproduct:astainlesssteellinerpipeattheJunctionStructureandabandonmentoftheremainingoftheJunctionStructure.Alternative1Cwouldresultinaninternally‐reinforcedJunctionStructureandwouldretaintheJunctionStructureaspartoftheoutfallsystem.

7.1.1 Construction Access and Staging Area

Forallthreealternatives,thefirstrequirementistoprovideaccessandastagingareaforconstruction.Duringtheoriginalconstructionoftheoutfallproject,astagingareaof200feetx100feetwasprovidedclosetotheJunctionStructure.Thisareawouldberequiredduringtherehabilitationwork.

TheconstructionstagingareaandaccessrecommendedbyDudek(seeFigure7‐1)intheMarch2008CRRwouldbeadequateforconstructingtheproposedalternatives.CoordinationwiththeDohenyStateParkandCaliforniaCoastalCommissionwouldberequiredduringtheconstruction.Vegetationatthesouthwestcorneroftheparkmayhavetoberelocatedduringconstructionandreinstatedafterconstruction.Campsites37and38wouldbeunavailabletothepublicduringconstruction.Toavoiddisturbancetothecampers,theconstructionshouldbescheduledduringtheoff‐season.DohenyStateParkmayrequestcompensationforthelossofcampingrevenueduringtheperiodoftimethecampsitesarenotavailableforrent.SOCWAshouldmeetwithStateParkswellinadvanceoftheconstructiontonegotiatereimbursementforthelossofrevenue.

Forconstructionatthebeach,coordinationwithmultipleagenciesandanEIRwouldberequired.SOCWAshouldplanforthiscoordinationandapprovalwellinadvance.

South Oran

BLACK & VE

(1) – Constr(2) ‐ Sugges

Figure 7‐1

7.1.2 C

Theconst

a. Eb. Ec. Ind. C

ene. Cf. M

St

ge County Wast

EATCH | CONSTR

uction area (sizested access to th

1: Constructio

onstruction

tructionsequ

stablishtheaxcavatethesnstallatempreateanopentrytotheJuonductaninMakenecessatructureand

37 &

38

(1)

(2

Junction

tewater Authori

RUCTABILITY REV

e to be determinhe Construction

on Access and

Sequence f

uencewould

accessroutesoilaroundtoraryriseroeningonthetunctionStrucnternalinspearyadjustmendOutfallpipe

2)

Doh

n Structure

ity | SAN JUAN

VIEW

ned during DetaiArea from Dohe

d Staging Are

for Alternati

dinvolvethe

andconstrutheJunctionSorpressureatopoftheJuncture.ctionoftheJnttothefabres.

heny State Par

CREEK OUTFALL

iled Design Stageny State Park –

ea

ives 1B‐2 an

followingste

uctionstagingStructuretoaccesshatchnctionStruct

JunctionStruricatedpipe

rk

L JUNCTION STR

e) size to be deter

nd 1B‐5

epsinthesa

garea.thetopofth(aftercreatintureformate

ucturesectionstos

RUCTURE REHAB

rmined

meorderas

hestructure.nganopeninerialmoveme

suittheactua

BILITATION

listed:

ng).entandhum

alJunction

7‐2

man


BLACK & VEATCH | CONSTRUCTABILITY REVIEW 7‐3

g. Insertthethreepipesections,jointhemtogether,andanchortemporarilytotheJunctionStructurewallafterplacingtheminthefinalposition.

h. Enterthenewpipeandanchorthemtotheoutfallpipesatbothends.Closethemanwayonthenewpipeaftertheanchorsareinstalled.

i. Inflatethepipesealsatbothends.j. DewatertheJunctionStructure.k. Groutthespacebetweenthenewpipeandexistingoutfallpipe.l. Deflatethepipeseals.m. FilltheJunctionStructurewithlightweightconcretetothetop(optional).n. Removetheriserpipe/pressurehatchandfillthearea.o. Reinstatetheareausedforaccessandconstructionstaging.

7.1.3 Construction Sequence for Alternative 1C

Theconstructionsequencewouldinvolvethefollowingstepsinthesameorderaslisted:

a. Establishtheaccessrouteandconstructionstagingarea.b. ExcavatethesoilaroundtheJunctionStructuretothetopofthestructure.c. Installatemporaryriserorpressureaccesshatch(aftercreatinganopening).d. CreateanopeningonthetopoftheJunctionStructureformaterialmovementandhuman

entrytotheJunctionStructure.e. ConductaninternalinspectionoftheJunctionStructuref. Insertthebypassarrangementcompletewithpipesealsandflexiblehoseandanchortothe

wall.g. Inflatethepipesealsatbothends.h. DewatertheJunctionStructure.i. RemovepartoftheconcreteatthebottomoftheJunctionStructure.j. ReinforcethebottomoftheJunctionStructureperDrawings.k. Allowtheconcretetocureandtesttheconcretecubes.l. Aftertheconcretehasachievedtherequiredstrength,removethetemporarybypassafter

deflatingthepipeseals.m. Removetheriserpipe/pressurehatchandfillthearea.n. Reinstatetheareausedforaccessandconstructionstaging.

Thesealternativeswouldrequiremultipleentriesforunderwaterwork.Theflowthroughtheoutfallshouldbereducedasmuchasfeasibleforthesafetyofthepersonnelworkingunderwater.Theallowablewatervelocityduringunderwaterworkshallbedeterminedinconsultationwiththespecialtycompanyengagedforunderwaterwork.Asaninitialstep,SOCWAisplanningtoconductteststoestablishtheminimumrequiredflowandthedurationofminimumflowthroughtestsplannedinMay,2014.


BLACK & VEATCH | CONSTRUCTION COST ESTIMATES AND SCHEDULE 8‐1

8.0 Construction Cost Estimates and Schedule Thissectionprovidestheconstructioncostestimatesandcorrespondingconstructionschedulesforthealternativesunderconsideration.Thecostsprovidedbelowarebasedoncurrentrates.Escalationtomid‐pointofconstructionassumesoneyearfromnowforthestartofconstruction.CostsforEIR,coordinationwithagencies,detaileddesign,andconstructionphaseservicesarenotincludedinthisestimates.

8.1 CONSTRCUTION COST ESTIMATES FOR ALTERNATIVES 1B‐2 AND 1B‐5

Sincethesetwoalternativesarealmostidentical,thecostwouldbethesame.Table8‐1providestheestimatedcost:

Table 8‐1: Estimated Construction Cost for Alternatives 1B‐2 and 1B‐5

ITEM UNIT QUANTITY UNIT RATE COST, $

Excavation to top of Junction Structure Cu. Yard 48.00 12 576

Temporary Riser / Access Hatch Lump sum 1.00 12,000 12,000

Concrete demolition at top of Structure Lump sum 1.00 2,000 2,000

Inspection of Junction Structure Lump sum 1.00 12,000 12,000

Sleeve Material Cost (SS) Lump sum 1.00 36,000 36,000

Pipe Couplings No 2.00 6,000 12,000

Pipe Seals No 4.00 2,000 8,000

Miscellaneous Materials Lump sum 1.00 3,000 3,000

Labor for Installation Lump sum 1.00 48,000 48,000

Lightweight Concrete fill Cu. Yd 62.00 130 8,060

Site Restoration Lump sum 1.00 12,000 12,000

Sub Total 153,636

Contingency % 30.00 46,091

General Conditions % 20.00 39,945

Contractor Overhead and Profit % 15.00 35,951

Escalation to mid‐point % 3.00 8,269

Sales Tax % 7.75 22,002

Estimated Construction Cost 305,893

8.2 CONSTRUCTION COST ESTIMATES FOR ALTERNATIVE 1C

Table8‐2providestheestimatedconstructioncostforAlternative1C.



Table 8‐2: Estimated Construction Cost for Alternative 1C

ITEM UNIT QUANTITY UNIT RATE COST, $

Excavation to top of Junction Structure Cu. Yard 48.00 12 576

Temporary Riser / Access Hatch lbs 3,800.00 4 15,200

Concrete demolition at top of Structure Lump sum 1.00 2,000 2,000

Inspection of Junction Structure Lump sum 1.00 12,000 12,000

Temporary Bypass Material Lump sum 1.00 32,000 32,000

Miscellaneous Materials Lump sum 1.00 1,000 1,000

Labor for Installation (under water) Lump sum 1.00 36,000 36,000

Concrete work Lump sum 1.00 20,000 20,000

Site Restoration Lump sum 1.00 12,000 12,000

Sub Total 130,776

Contingency % 30.00 39,233

General Conditions % 20.00 34,002

Contractor Overhead and Profit % 15.00 30,602

Escalation to mid‐point % 3.00 7,038

Sales Tax % 7.75 18,728

Estimated Construction Cost $ 260,378

8.3 CONSTRUCTION COST ESTIMATES FOR PERMANENT ACCESS HATCH

Forpermanentaccesshatch,noadditionalcostisrequired.

8.4 CONSTRUCTION SCHEDULE FOR ALTERNATIVES 1B‐2 AND 1B‐5

ApreliminaryconstructionscheduleforAlternatives1B‐2and1B‐5isshownasFigure8‐1.Theconstructionscheduleassumesthattheflowcouldbeshutdownonceaweek.Theshutdownperiodisstilltobeestablished,butisexpectedtobeintherangeoffivetosixhoursforeachshutdown.Thetimerequiredforprocurementandfabricationofmaterialsisnotincludedintheschedulebelow.



Figure 8‐1: Preliminary Construction Schedule for Alternatives 1B‐2 and 1B‐5

8.5 CONSTRUCTION SCHEDULE FOR ALTERNATIVES 1C

ApreliminaryconstructionscheduleforAlternatives1CisshownasFigure8‐2.Theconstructionscheduleassumesthattheflowcouldbeshutdownonceaweek.Theshutdownperiodisstilltobeestablished,butisexpectedtobeintherangeoffivetosixhoursforeachshutdown.

Figure 8‐2: Preliminary Construction Schedule for Alternative 1C



8.6 CONSTRUCTION SCHEDULE FOR PERMANENT ACCESS HATCH

TheexistingaccesshatchattheSurgeTowerStructureisadequateforpermanentaccess.Noadditionalworkisrequired.


BLACK & VEATCH | RECOMMENDATIONS 9‐1

9.0 Recommendations ThissectionprovidesfinalrecommendationsfortheJunctionStructureandPermanentAccessHatch.

9.1 JUNCTION STRUCTURE REHABILITATION RECOMMENDATION

Table9‐1presentsthescreeningsummaryforthealternativesshowninTable6‐1andaddsalineitemforconstructioncost.

Table 9‐1: Junction Structure Rehabilitation Evaluation

EVALUATION CRITERIA INTERNAL REINFORCEMENT ALTERNATIVES

1B‐2 1B‐5 1C

Technical Feasibility 4 5 4

Temporary Construction Impacts 4 4 4

Constructability 4 4 1

Construction Access 3 3 3

Construction Schedule 4 4 3

Plant Shutdown 3 3 3

Beach Use Impacts 3 3 3

Permitting 3 3 3

Construction Cost 3 3 4

Total Score 31 32 28

Black & Veatch Ranking 2 1 3

Ranking: A score of 1‐5 has been assigned for each evaluation criteria; a higher score represents a better alternative based on the listed evaluation criteria

Alternatives1B‐2and1B‐5havesimilarscoresandwouldremovetheJunctionStructurefromtheOutfallSystem,eliminatingtheneedforanyfuturemaintenanceoftheJunctionStructure.AcombinationofAlternatives1B‐2and1B‐5consistingofbothinternalpipesealsandexternalpipesealswouldprovideaddedsafetyduringconstruction,whichcanbelefttothediscretionoftheContractor.

Alternative1B‐5hasthemaximumscoreandisrecommended.

TheconstructionaccesswouldbeattheJunctionStructureforallthealternativesconsidered.

Forthepermanentaccess,theexistinghatchattheoldSurgeTowerStructureisrecommended.


BLACK & VEATCH | RECOMMENDATIONS 9‐2

This page is intentionally left blank

san juan creek outfall junction structure …...apr 23, 2014 · the san juan creek outfall system...

Documents