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  <xs:element id="clh_NumberOfPerformanceStockAwardsThatPerformanceCriteriaNotAttained" abstract="false" name="NumberOfPerformanceStockAwardsThatPerformanceCriteriaNotAttained" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="clh_StockRepurchasedAndRetiredDuringPeriodValueExcludingExerciseTax" abstract="false" name="StockRepurchasedAndRetiredDuringPeriodValueExcludingExerciseTax" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_CertainInterestRateSwapsMember" abstract="true" name="CertainInterestRateSwapsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="clh_A2020StockIncentivePlanMember" abstract="true" name="A2020StockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_PerformanceStockAwardsMember" abstract="true" name="PerformanceStockAwardsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_FederalAndStateEnforcementActionsMember" abstract="true" name="FederalAndStateEnforcementActionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_SuperfundProceedingsMember" abstract="true" name="SuperfundProceedingsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_ProductLiabilityCasesMember" abstract="true" name="ProductLiabilityCasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_SiteContingencyNumberOfSites" abstract="false" name="SiteContingencyNumberOfSites" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyNumberOfSitesOwnedByEntity" abstract="false" name="SiteContingencyNumberOfSitesOwnedByEntity" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyNumberOfSitesOwnedByThirdParty" abstract="false" name="SiteContingencyNumberOfSitesOwnedByThirdParty" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyEnvironmentalRemediationExpenseSettledNumberOfSitesOwnedByThirdParty" abstract="false" name="SiteContingencyEnvironmentalRemediationExpenseSettledNumberOfSitesOwnedByThirdParty" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyEnvironmentalRemediationExpenseNumberOfSitesOwnedByThirdParty" abstract="false" name="SiteContingencyEnvironmentalRemediationExpenseNumberOfSitesOwnedByThirdParty" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyNotRequiringEnvironmentalRemediationExpenseNumberOfSitesOwnedByThirdParty" abstract="false" name="SiteContingencyNotRequiringEnvironmentalRemediationExpenseNumberOfSitesOwnedByThirdParty" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_NumberofSitesPotentialLiabilityExceedsSubstantialQuota" abstract="false" name="NumberofSitesPotentialLiabilityExceedsSubstantialQuota" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_SiteContingencyNoticeReceivedNumberOfSitesOwnedByThirdParty" abstract="false" name="SiteContingencyNoticeReceivedNumberOfSitesOwnedByThirdParty" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="clh_DeductibleHealthInsurancePolicy" abstract="false" name="DeductibleHealthInsurancePolicy" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_DeductiblePerOccurrenceForWorkersCompensation" abstract="false" name="DeductiblePerOccurrenceForWorkersCompensation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_DeductiblePerOccurrenceForGeneralLiability" abstract="false" name="DeductiblePerOccurrenceForGeneralLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_DeductiblePerOccurrenceForVehicleLiability" abstract="false" name="DeductiblePerOccurrenceForVehicleLiability" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_RetentionforEnvironmentalImpairment" abstract="false" name="RetentionforEnvironmentalImpairment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AccruedSelfInsuranceLiabilities" abstract="false" name="AccruedSelfInsuranceLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsYearOne" abstract="false" name="AnticipatedSelfInsurancePaymentsYearOne" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsYearTwo" abstract="false" name="AnticipatedSelfInsurancePaymentsYearTwo" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsYearThree" abstract="false" name="AnticipatedSelfInsurancePaymentsYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsYearFour" abstract="false" name="AnticipatedSelfInsurancePaymentsYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsYearFive" abstract="false" name="AnticipatedSelfInsurancePaymentsYearFive" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_AnticipatedSelfInsurancePaymentsThereafter" abstract="false" name="AnticipatedSelfInsurancePaymentsThereafter" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_UndiscountedSelfInsuranceLiabilities" abstract="false" name="UndiscountedSelfInsuranceLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_SelfInsuranceDiscountRate" abstract="false" name="SelfInsuranceDiscountRate" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_ROUAssetsAbstract" abstract="true" name="ROUAssetsAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_LeaseLiabilityCurrentAbstract" abstract="true" name="LeaseLiabilityCurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_LeaseLiabilityNoncurrentAbstract" abstract="true" name="LeaseLiabilityNoncurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_FinanceLeaseCost" abstract="false" name="FinanceLeaseCost" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_WeightedAverageRemainingLeaseTermLesseeAbstract" abstract="true" name="WeightedAverageRemainingLeaseTermLesseeAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_WeightedAverageDiscountRateLesseeAbstract" abstract="true" name="WeightedAverageDiscountRateLesseeAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_CashFlowLesseeAbstract" abstract="true" name="CashFlowLesseeAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_ReportableSegmentsMember" abstract="true" name="ReportableSegmentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="clh_IncomeLossFromContinuingOperationsBeforeInterestTaxDepreciationAndAmortizationNet" abstract="false" name="IncomeLossFromContinuingOperationsBeforeInterestTaxDepreciationAndAmortizationNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_ReconciliationOfNetIncomeToAdjustedEbitdaAbstract" abstract="true" name="ReconciliationOfNetIncomeToAdjustedEbitdaAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="clh_CorporateCosts" abstract="false" name="CorporateCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_NonRecurringFacilityStartupCosts" abstract="false" name="NonRecurringFacilityStartupCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="clh_CanadaAndOtherForeignCountriesMember" abstract="true" name="CanadaAndOtherForeignCountriesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="clh_PropertyPlantAndEquipmentNetPercent" abstract="false" name="PropertyPlantAndEquipmentNetPercent" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="clh_IntangibleAssetsNetExcludingGoodwillPercent" abstract="false" name="IntangibleAssetsNetExcludingGoodwillPercent" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
</xs:schema>
