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  <xsd:element id="pwr_BusinessAcquisitionsProFormaNetIncomeLossAttributableToCommonStockFromContinuingOperationsNetOfTax" name="BusinessAcquisitionsProFormaNetIncomeLossAttributableToCommonStockFromContinuingOperationsNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses" name="BusinessAcquisitionsProFormaSellingGeneralAndAdministrativeExpenses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="pwr_BusinessCombinationCashConsiderationTransferredOrToBeTransferred" name="BusinessCombinationCashConsiderationTransferredOrToBeTransferred" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesTargetTerm" name="BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesTargetTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssetsCurrent" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssetsCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="pwr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="pwr_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetTangibleAssets" name="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetTangibleAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CanadianAndAustralianDollarsMember" name="CanadianAndAustralianDollarsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CapitalforInfrastructureProjectsMember" name="CapitalforInfrastructureProjectsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CommitmentAndContingenciesLineItems" name="CommitmentAndContingenciesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CommitmentAndContingenciesTable" name="CommitmentAndContingenciesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CommonStockClassUndefinedMember" name="CommonStockClassUndefinedMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" name="CommonStockWithheldForSettlementOfEmployeeTaxLiabilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_ContractWithCustomerAssetCumulativeCatchUpAdjustmentToGrossProfitChangeInEstimate" name="ContractWithCustomerAssetCumulativeCatchUpAdjustmentToGrossProfitChangeInEstimate" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="pwr_ContractWithCustomerContractValue" name="ContractWithCustomerContractValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="pwr_ContractWithCustomerPercentAggregateChangeInContractEstimatesImpactOnGrossMargin" name="ContractWithCustomerPercentAggregateChangeInContractEstimatesImpactOnGrossMargin" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_ContractWithCustomerPercentageOfCompletion" name="ContractWithCustomerPercentageOfCompletion" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="pwr_CrossDefaultProvisions" name="CrossDefaultProvisions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_CurriculumMember" name="CurriculumMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_DebtInstrumentCovenantAcquisitionThresholdForLeverageRatio" name="DebtInstrumentCovenantAcquisitionThresholdForLeverageRatio" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_DebtInstrumentCovenantInterestCoverageRatioMinimum" name="DebtInstrumentCovenantInterestCoverageRatioMinimum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:pureItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_DebtInstrumentCovenantLeverageRatioAcquisitionCompletedInCurrentAndTwoSubsequentQuartersMaximum" name="DebtInstrumentCovenantLeverageRatioAcquisitionCompletedInCurrentAndTwoSubsequentQuartersMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:pureItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_DebtInstrumentCovenantLeverageRatioMaximum" name="DebtInstrumentCovenantLeverageRatioMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:pureItemType" xbrli:periodType="instant" />
  <xsd:element id="pwr_DebtInstrumentIncreaseDecreaseInMaximumAdditionalInterestAndFeeRates" name="DebtInstrumentIncreaseDecreaseInMaximumAdditionalInterestAndFeeRates" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" name="DecreaseInFairValueOfReportingUnitsConsideredForImpairmentCalculation" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_DomesticBankAccountsMember" name="DomesticBankAccountsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_DomesticJointVenturesMember" name="DomesticJointVenturesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_EPCElectricTransmissionProjectMember" name="EPCElectricTransmissionProjectMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ElectricPowerDivisionMember" name="ElectricPowerDivisionMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ElectricPowerInfrastructureMember" name="ElectricPowerInfrastructureMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_EmployersLiabilityInsuranceClaimsDeductible" name="EmployersLiabilityInsuranceClaimsDeductible" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_EquitySecuritiesWithoutReadilyDeterminableFairValueOwnershipPercentage" name="EquitySecuritiesWithoutReadilyDeterminableFairValueOwnershipPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_EstimateMember" name="EstimateMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_EstimatedCostsToCompleteBondedProjects" name="EstimatedCostsToCompleteBondedProjects" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_EurocurrencyRateMember" name="EurocurrencyRateMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExcessOfBaseRateDomesticBorrowingsOnlyMember" name="ExcessOfBaseRateDomesticBorrowingsOnlyMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExcessOfEuroCurrencyRateMember" name="ExcessOfEuroCurrencyRateMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExcessOfEuroCurrencyRateOfCreditAgreementForForeignBorrowingsMember" name="ExcessOfEuroCurrencyRateOfCreditAgreementForForeignBorrowingsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExcessOfEurocurrencyRateApplicableToDomesticBorrowingsOnlyMember" name="ExcessOfEurocurrencyRateApplicableToDomesticBorrowingsOnlyMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExcessOfFederalFundsRateMember" name="ExcessOfFederalFundsRateMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExchangeableSharesAssociatedWithSeriesGPreferredStockMember" name="ExchangeableSharesAssociatedWithSeriesGPreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExchangeableSharesForCommonStockMember" name="ExchangeableSharesForCommonStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExchangeableSharesMember" name="ExchangeableSharesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ExchangeableSharesNotAssociatedWithPreferredStockMember" name="ExchangeableSharesNotAssociatedWithPreferredStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_FairValueInputsCustomerAttritionRates" name="FairValueInputsCustomerAttritionRates" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_FairValueInputsRateOfReturn" name="FairValueInputsRateOfReturn" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ForeignBankAccountsMember" name="ForeignBankAccountsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_GeneralLiabilityInsuranceClaimsDeductible" name="GeneralLiabilityInsuranceClaimsDeductible" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_GoodwillAndIntangibleAssetsLineItems" name="GoodwillAndIntangibleAssetsLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_GoodwillAndIntangibleAssetsTable" name="GoodwillAndIntangibleAssetsTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_HealthCareDeductible" name="HealthCareDeductible" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_IncomeTaxesLineItems" name="IncomeTaxesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_IncomeTaxesTable" name="IncomeTaxesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_InfrastructureInvestorsPartnershipMember" name="InfrastructureInvestorsPartnershipMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_InvestmentsInJointVenturesMember" name="InvestmentsInJointVenturesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_LatinAmericaandOtherMember" name="LatinAmericaandOtherMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_LengthOfTransmissionLine" name="LengthOfTransmissionLine" nillable="true" substitutionGroup="xbrli:item" type="num:lengthItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_LettersOfCreditAndBankGuaranteesMember" name="LettersOfCreditAndBankGuaranteesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_LineOfCreditFacilityIncreaseInMaximumBorrowingCapacity" name="LineOfCreditFacilityIncreaseInMaximumBorrowingCapacity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="pwr_LineOfCreditFacilityOptionToIncreaseAmount" name="LineOfCreditFacilityOptionToIncreaseAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_LorenzoBentonvTelecomNetworkSpecialistsIncMember" name="LorenzoBentonvTelecomNetworkSpecialistsIncMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_MaurepasProjectDisputeMember" name="MaurepasProjectDisputeMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" name="MinimumNumberOfSharesThatCanBeExchangedByExchangeableShareholdersUnlessNumberOfRemainingExchangeableSharesRegisteredInNameOfHolderIsLess" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_NaturalGasPipelineConstructionProjectNortheastUnitedStates1Member" name="NaturalGasPipelineConstructionProjectNortheastUnitedStates1Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_NaturalGasPipelineConstructionProjectNortheastUnitedStates2Member" name="NaturalGasPipelineConstructionProjectNortheastUnitedStates2Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NotesReceivableReduction" name="NotesReceivableReduction" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfBusinessesAcquiredWithPreferredStockIssuedToVotingTrusts" name="NumberOfBusinessesAcquiredWithPreferredStockIssuedToVotingTrusts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfCustomersRepresentingTenPercentOrMoreOfNetReceivablePosition" name="NumberOfCustomersRepresentingTenPercentOrMoreOfNetReceivablePosition" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="pwr_NumberOfCustomersRepresentingTenPercentOrMoreOfRevenue" name="NumberOfCustomersRepresentingTenPercentOrMoreOfRevenue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfInternalDivisions" name="NumberOfInternalDivisions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfReportingUnitsImpactedByImpairmentCharges" name="NumberOfReportingUnitsImpactedByImpairmentCharges" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfReportingUnitsWithFairValuesThatApproximatedCarryingValuesAfterSensitivityOfADecreaseInFairValue" name="NumberOfReportingUnitsWithFairValuesThatApproximatedCarryingValuesAfterSensitivityOfADecreaseInFairValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" name="NumberOfSharesOfCommonStockReceivedForEachExchangeableShare" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_NumberOfSubstations" name="NumberOfSubstations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_OilAndGasDivisionMember" name="OilAndGasDivisionMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_OilAndGasInfrastructureDivisionOperatingUnitsThatHaveBeenNegativelyImpactedByVariousFactorsMember" name="OilAndGasInfrastructureDivisionOperatingUnitsThatHaveBeenNegativelyImpactedByVariousFactorsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_OilAndGasInfrastructureServicesMember" name="OilAndGasInfrastructureServicesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_OperatingLeasesLineItems" name="OperatingLeasesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_OptionToIncreaseRevolvingCommitmentsUnderCreditAgreement" name="OptionToIncreaseRevolvingCommitmentsUnderCreditAgreement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_OtherCommitmentsPlannedOilAndGasInfrastructureProjectsMember" name="OtherCommitmentsPlannedOilAndGasInfrastructureProjectsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_OtherCreditFacilitiesMember" name="OtherCreditFacilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_OtherLongTermDebtMember" name="OtherLongTermDebtMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_PercentageOfCapitalStockOfDirectForeignSubsidiariesRequiredToSecureCreditAgreement" name="PercentageOfCapitalStockOfDirectForeignSubsidiariesRequiredToSecureCreditAgreement" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_PercentageOfForeignRevenue" name="PercentageOfForeignRevenue" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_PerformanceBasedAwardPerformancePercentage" name="PerformanceBasedAwardPerformancePercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_PerformanceLettersOfCreditMember" name="PerformanceLettersOfCreditMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_PerformanceUnitsMember" name="PerformanceUnitsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_PreferredStockSharesRetired" name="PreferredStockSharesRetired" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ProcessingFacilityConstructionProjectTexasMember" name="ProcessingFacilityConstructionProjectTexasMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" name="ReductionInCompanyMaximumFundedDebtAndMaximumSeniorDebtByAllCashAndCashEquivalentsInExcessOfAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ResidualValueGuaranteesMember" name="ResidualValueGuaranteesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_RestrictedStockUnitsToBeSettledInCashMember" name="RestrictedStockUnitsToBeSettledInCashMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_RestrictedStockUnitsToBeSettledInCommonStockMember" name="RestrictedStockUnitsToBeSettledInCommonStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_RevenueRecognizedRelatedToUnapprovedChangeOrdersAndClaims" name="RevenueRecognizedRelatedToUnapprovedChangeOrdersAndClaims" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_RevolvingLoansAndLetterOfCreditInAlternativeCurrenciesMember" name="RevolvingLoansAndLetterOfCreditInAlternativeCurrenciesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_ScheduleOfOperatingLeasesFutureMinimumPaymentsDueTable" name="ScheduleOfOperatingLeasesFutureMinimumPaymentsDueTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_ScheduleOfShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsValuationAssumptionsTableTextBlock" name="ScheduleOfShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsValuationAssumptionsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_SeniorSecuredCreditFacilityMember" name="SeniorSecuredCreditFacilityMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_StrongholdLtd.andStrongholdSpecialtyLtd.Member" name="StrongholdLtd.andStrongholdSpecialtyLtd.Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_SummaryOfSignificantAccountingPoliciesLineItems" name="SummaryOfSignificantAccountingPoliciesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_SummaryOfSignificantAccountingPoliciesTable" name="SummaryOfSignificantAccountingPoliciesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_SwingLinesLoanMember" name="SwingLinesLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingAccelerationOfCertainDeductionsProvisionalIncomeTaxExpense" name="TaxCutsAndJobsActOf2017IncompleteAccountingAccelerationOfCertainDeductionsProvisionalIncomeTaxExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit" name="TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingEntityRestructuringAndRecapitalizationIncreaseDecreaseInProvisionalIncomeTaxBenefit" name="TaxCutsAndJobsActOf2017IncompleteAccountingEntityRestructuringAndRecapitalizationIncreaseDecreaseInProvisionalIncomeTaxBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingEntityRestructuringAndRecapitalizationProvisionalIncomeTaxBenefit" name="TaxCutsAndJobsActOf2017IncompleteAccountingEntityRestructuringAndRecapitalizationProvisionalIncomeTaxBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingProvisionalIncomeTaxExpenseBenefit" name="TaxCutsAndJobsActOf2017IncompleteAccountingProvisionalIncomeTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="pwr_TaxCutsAndJobsActOf2017IncompleteAccountingTransitionTaxForAccumulatedForeignEarningsProvisionalIncomeTaxExpense" name="TaxCutsAndJobsActOf2017IncompleteAccountingTransitionTaxForAccumulatedForeignEarningsProvisionalIncomeTaxExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_TermLoanMember" name="TermLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_TreasuryStockAssociatedWithDeferredCompensationPlansMember" name="TreasuryStockAssociatedWithDeferredCompensationPlansMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_TwoThousandAndElevenPlanMember" name="TwoThousandAndElevenPlanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_UnearnedRevenueMember" name="UnearnedRevenueMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_UnitPriceContractsMember" name="UnitPriceContractsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="pwr_VehicleFleetCommittedCapitalMember" name="VehicleFleetCommittedCapitalMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_VoltageOfSubstations" name="VoltageOfSubstations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:decimalItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="pwr_WaterandGasPipelineInfrastructureContractorMember" name="WaterandGasPipelineInfrastructureContractorMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="pwr_WorkersCompensationInsuranceClaimsDeductible" name="WorkersCompensationInsuranceClaimsDeductible" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
</xsd:schema>
