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  <xsd:element name="NonmonetaryNotionalAmountOfPriceRiskDerivativesOfNaturalGas" id="mwe_NonmonetaryNotionalAmountOfPriceRiskDerivativesOfNaturalGas" type="num:energyItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="NonmonetaryNotionalAmountOfPriceRiskDerivativesOfNaturalGasLiquids" id="mwe_NonmonetaryNotionalAmountOfPriceRiskDerivativesOfNaturalGasLiquids" type="num:volumeItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
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  <xsd:element name="PaymentsOfDistributionsToCommonUnitholdersAndMinorityInterest" id="mwe_PaymentsOfDistributionsToCommonUnitholdersAndMinorityInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="PaymentsOfPremiumsOnRedemptionOfLongTermDebt" id="mwe_PaymentsOfPremiumsOnRedemptionOfLongTermDebt" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="PaymentsToAcquireInterestInSubsidiaries" id="mwe_PaymentsToAcquireInterestInSubsidiaries" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfAdditionalCapitalContributionRequiredToDevelopProjects" id="mwe_PercentageOfAdditionalCapitalContributionRequiredToDevelopProjects" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfAdditionalCapitalContributionRequiredToMaintainOwnershipInterest" id="mwe_PercentageOfAdditionalCapitalContributionRequiredToMaintainOwnershipInterest" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="PercentageOfCapitalContributionAfterNoncontrollingInterestRequiredContribution" id="mwe_PercentageOfCapitalContributionAfterNoncontrollingInterestRequiredContribution" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="PercentageOfCashGenerationReceived" id="mwe_PercentageOfCashGenerationReceived" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="PercentageOfInitialRequiredCapitalContribution" id="mwe_PercentageOfInitialRequiredCapitalContribution" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
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  <xsd:element name="PercentageOfRequiredCapitalContributionByNoncontrollingOwners" id="mwe_PercentageOfRequiredCapitalContributionByNoncontrollingOwners" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfRequiredCapitalContributionByReportingEntityAfterNCI" id="mwe_PercentageOfRequiredCapitalContributionByReportingEntityAfterNCI" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
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  <xsd:element name="PeriodForWhichCashReservesAreCreatedForDistributionToMembersOrLimitedPartners" id="mwe_PeriodForWhichCashReservesAreCreatedForDistributionToMembersOrLimitedPartners" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="ProceedsFromLiability" id="mwe_ProceedsFromLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ProceedsFromPaymentsForAdvancesToAffiliatesSubsidiariesAndHoldingCompanies" id="mwe_ProceedsFromPaymentsForAdvancesToAffiliatesSubsidiariesAndHoldingCompanies" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ProductSupplyAgreementFutureMinimumPaymentsDueCurrent" id="mwe_ProductSupplyAgreementFutureMinimumPaymentsDueCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element name="ProductSupplyAgreementFutureMinimumPaymentsServicesIncludedInPayment" id="mwe_ProductSupplyAgreementFutureMinimumPaymentsServicesIncludedInPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="ProductSupplyAgreementsFutureMinimumPaymentsInterestIncludedInPayments" id="mwe_ProductSupplyAgreementsFutureMinimumPaymentsInterestIncludedInPayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="PropaneContractMember" id="mwe_PropaneContractMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PropertyPlantAndEquipmentOtherThanMiscellaneousEquipmentAndVehiclesMember" id="mwe_PropertyPlantAndEquipmentOtherThanMiscellaneousEquipmentAndVehiclesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PurchasedProductCostsMember" id="mwe_PurchasedProductCostsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RealizedGainLossOnDerivativeInstrumentsNotDesignatedAsHedgingInstruments" id="mwe_RealizedGainLossOnDerivativeInstrumentsNotDesignatedAsHedgingInstruments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="ReceivablesAndOtherAssetsCurrent" id="mwe_ReceivablesAndOtherAssetsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="RestrictedCashAndCashEquivalentsNoncurrentThresholdPeriod" id="mwe_RestrictedCashAndCashEquivalentsNoncurrentThresholdPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RevenueAndExpenseAccrualPolicyTextBlock" id="mwe_RevenueAndExpenseAccrualPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="ScheduleOfDisposalsTreatedAsFinancingArrangementDisclosuresTextBlock" id="mwe_ScheduleOfDisposalsTreatedAsFinancingArrangementDisclosuresTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfFiniteLivedIntangibleAssetsBySegmentTable" id="mwe_ScheduleOfFiniteLivedIntangibleAssetsBySegmentTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="ScheduleOfFutureMinimumRentalPaymentsReceivableForOperatingLeasesTableTextBlock" id="mwe_ScheduleOfFutureMinimumRentalPaymentsReceivableForOperatingLeasesTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfOtherLongTermLiabilitiesTableTextBlock" id="mwe_ScheduleOfOtherLongTermLiabilitiesTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfPartnersCapitalAccountPublicEquityOfferingsTableTextBlock" id="mwe_ScheduleOfPartnersCapitalAccountPublicEquityOfferingsTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfPropertyPlantAndEquipmentTableTextBlock" id="mwe_ScheduleOfPropertyPlantAndEquipmentTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfReconciliationOfRevenueFromSegmentsToConsolidatedRevenuesAndOperatingIncomeBeforeItemsNotAllocatedToSegmentsToConsolidatedIncomeLossBeforeProvisionForIncomeTaxTableTextBlock" id="mwe_ScheduleOfReconciliationOfRevenueFromSegmentsToConsolidatedRevenuesAndOperatingIncomeBeforeItemsNotAllocatedToSegmentsToConsolidatedIncomeLossBeforeProvisionForIncomeTaxTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfValuationAndQualifyingAccountsDisclosureTableTextBlock" id="mwe_ScheduleOfValuationAndQualifyingAccountsDisclosureTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SecondSignificantCustomerMember" id="mwe_SecondSignificantCustomerMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="SeniorNotes5.5PercentIssuedAugust2012DueFebruary2023Member" id="mwe_SeniorNotes5.5PercentIssuedAugust2012DueFebruary2023Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes6.25PercentIssuedOctober2011DueJune2022Member" id="mwe_SeniorNotes6.25PercentIssuedOctober2011DueJune2022Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes6.5PercentIssuedFebruaryAndMarch2011DueAugust2021Member" id="mwe_SeniorNotes6.5PercentIssuedFebruaryAndMarch2011DueAugust2021Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes6.75PercentIssuedNovember2010DueNovember2020Member" id="mwe_SeniorNotes6.75PercentIssuedNovember2010DueNovember2020Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes6.875PercentIssuedOctober2004Due2014Member" id="mwe_SeniorNotes6.875PercentIssuedOctober2004Due2014Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes8.5PercentIssuedJulyAndOctober2006Due2016Member" id="mwe_SeniorNotes8.5PercentIssuedJulyAndOctober2006Due2016Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotes8.75PercentIssuedAprilAndMay2008DueApril2018Member" id="mwe_SeniorNotes8.75PercentIssuedAprilAndMay2008DueApril2018Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SeniorNotesDue2016And2018Member" id="mwe_SeniorNotesDue2016And2018Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberOfUnitsToVestBasedOnPerformanceRelatedToMarketCriteria" id="mwe_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberOfUnitsToVestBasedOnPerformanceRelatedToMarketCriteria" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberOfUnitsToVestBasedOnPerformanceRelatedToMarketCriteriaAndPerformanceCriteria" id="mwe_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNumberOfUnitsToVestBasedOnPerformanceRelatedToMarketCriteriaAndPerformanceCriteria" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformancePeriod" id="mwe_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformancePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="ShortTermSwinglineLoanCapacity" id="mwe_ShortTermSwinglineLoanCapacity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="SouthwestMember" id="mwe_SouthwestMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
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  <xsd:element name="SteamMethaneReformerLiabilityCarryingValue" id="mwe_SteamMethaneReformerLiabilityCarryingValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element name="SteamMethaneReformerLiabilityFairValue" id="mwe_SteamMethaneReformerLiabilityFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="SteamMethaneReformerLiabilityNonCurrent" id="mwe_SteamMethaneReformerLiabilityNonCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element name="TakeawayCapacityOfPipeline" id="mwe_TakeawayCapacityOfPipeline" type="xbrli:pureItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="ThresholdRelocationCostOfAssetsAsPercentageOfFairValueToBeClassifiedAsRealEstate" id="mwe_ThresholdRelocationCostOfAssetsAsPercentageOfFairValueToBeClassifiedAsRealEstate" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="TransfersToNoncontrollingInterestAbstract" id="mwe_TransfersToNoncontrollingInterestAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="UnrestrictedUnitsMember" id="mwe_UnrestrictedUnitsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="UticaSegmentMember" id="mwe_UticaSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ValuationAllowanceAsPercentageOfDeferredTaxAssetsCapitalLossCarryforwards" id="mwe_ValuationAllowanceAsPercentageOfDeferredTaxAssetsCapitalLossCarryforwards" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="VariableInterestEntitiesDisclosureAbstract" id="mwe_VariableInterestEntitiesDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="VariableInterestEntitiesDisclosureTextBlock" id="mwe_VariableInterestEntitiesDisclosureTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="VariableInterestEntitiesTextBlock" id="mwe_VariableInterestEntitiesTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NoncontrollingOwnersAccrualOfPreferenceAmount" id="mwe_NoncontrollingOwnersAccrualOfPreferenceAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="WeightedAverageNumberOfOutstandingCommonUnitsAbstract" id="mwe_WeightedAverageNumberOfOutstandingCommonUnitsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OwnershipPercentageOfGuarantorSubsidiaries" id="mwe_OwnershipPercentageOfGuarantorSubsidiaries" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="TemporaryCapitalContributionsByReportingEntityMaximum" id="mwe_TemporaryCapitalContributionsByReportingEntityMaximum" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="ScheduleOfEarningsPerShareByCommonClassTable" id="mwe_ScheduleOfEarningsPerShareByCommonClassTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="EarningsPerShareLineItems" id="mwe_EarningsPerShareLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OffsettingAssetsAndLiabilitiesTable" id="mwe_OffsettingAssetsAndLiabilitiesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RedeemableNonControllingInterestMember" id="mwe_RedeemableNonControllingInterestMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ReclassificationsBetweenPermanentAndTemporaryEquity" id="mwe_ReclassificationsBetweenPermanentAndTemporaryEquity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="ManagerFeesInConnectionWithIssuancesOfCommonUnit" id="mwe_ManagerFeesInConnectionWithIssuancesOfCommonUnit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfReconciliationOfEmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityTableTextBlock" id="mwe_ScheduleOfReconciliationOfEmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentWriteOffOfDeferredFinancingCostsAndUnamortizedDebtDiscounts" id="mwe_DebtInstrumentWriteOffOfDeferredFinancingCostsAndUnamortizedDebtDiscounts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ChesapeakeEnergyCorporationMember" id="mwe_ChesapeakeEnergyCorporationMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DivestitureDisclosureAbstract" id="mwe_DivestitureDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SummitMidstreamPartnersLPMember" id="mwe_SummitMidstreamPartnersLPMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SherwoodMember" id="mwe_SherwoodMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LengthOfGasGatheringPipelines" id="mwe_LengthOfGasGatheringPipelines" type="num:lengthItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="DisposalGroupIncludingDiscontinuedOperationNumberOfCompressorStations" id="mwe_DisposalGroupIncludingDiscontinuedOperationNumberOfCompressorStations" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DisposalGroupIncludingDiscontinuedOperationPowerOfCompressorStations" id="mwe_DisposalGroupIncludingDiscontinuedOperationPowerOfCompressorStations" type="num:powerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PartnersUnitsConversionBasis" id="mwe_PartnersUnitsConversionBasis" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PartnersUnitsConversionBasisInstallmentsNumber" id="mwe_PartnersUnitsConversionBasisInstallmentsNumber" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ClassBUnitsConversionFromDateOfIssuance" id="mwe_ClassBUnitsConversionFromDateOfIssuance" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="MAndRMWELibertyLLCMember" id="mwe_MAndRMWELibertyLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BuffaloCreekAcquisitionMember" id="mwe_BuffaloCreekAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionLengthOfNaturalGasGatheringPipeline" id="mwe_BusinessAcquisitionLengthOfNaturalGasGatheringPipeline" type="num:lengthItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionKeepWholeProcessingAgreementExtendedAdditionalTerm" id="mwe_BusinessAcquisitionKeepWholeProcessingAgreementExtendedAdditionalTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionLengthOfRightsOfWayAssociatedWithFutureConstructionOfHighPressureTrunkLine" id="mwe_BusinessAcquisitionLengthOfRightsOfWayAssociatedWithFutureConstructionOfHighPressureTrunkLine" type="num:lengthItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="EquityMethodInvestmentOtherThanTemporaryImpairmentNetOfTax" id="mwe_EquityMethodInvestmentOtherThanTemporaryImpairmentNetOfTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="CarryingValueOfDisposalAssets" id="mwe_CarryingValueOfDisposalAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfRestatedCondensedConsolidatedStatementOfCashFlowsInformationTableTextBlock" id="mwe_ScheduleOfRestatedCondensedConsolidatedStatementOfCashFlowsInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfRestatedCondensedConsolidatedStatementOfChangesInEquityInformationTableTextBlock" id="mwe_ScheduleOfRestatedCondensedConsolidatedStatementOfChangesInEquityInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfRestatedCondensedConsolidatedBalanceSheetInformationTableTextBlock" id="mwe_ScheduleOfRestatedCondensedConsolidatedBalanceSheetInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfRestatedCondensedConsolidatedStatementOfOperationsInformationTableTextBlock" id="mwe_ScheduleOfRestatedCondensedConsolidatedStatementOfOperationsInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ManagementFeeRevenues" id="mwe_ManagementFeeRevenues" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="NortheastSegmentMember" id="mwe_NortheastSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CommodityTypeAxis" id="mwe_CommodityTypeAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AtTheMarketOfferingProgramMember" id="mwe_AtTheMarketOfferingProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="StockIssuedByTypeOfProgramAxis" id="mwe_StockIssuedByTypeOfProgramAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="StockIssuedByTypeOfProgramDomain" id="mwe_StockIssuedByTypeOfProgramDomain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="November2012AtTheMarketOfferingProgramMember" id="mwe_November2012AtTheMarketOfferingProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="August2013AtTheMarketOfferingProgramMember" id="mwe_August2013AtTheMarketOfferingProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NumberOfSegmentsIntoWhichExistingOperationsCombinedDueToImmateriality" id="mwe_NumberOfSegmentsIntoWhichExistingOperationsCombinedDueToImmateriality" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RevenueDeferralAdjustmentAndOther" id="mwe_RevenueDeferralAdjustmentAndOther" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ContributionsToConsolidatedJointVenture" id="mwe_ContributionsToConsolidatedJointVenture" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfInitialRequiredCapitalContributionOriginalAgreement" id="mwe_PercentageOfInitialRequiredCapitalContributionOriginalAgreement" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ActualCapitalContributedByNoncontrollingOwners" id="mwe_ActualCapitalContributedByNoncontrollingOwners" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="SMRTransactionDisclosureTextBlock" id="mwe_SMRTransactionDisclosureTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodNumberOfUnitsRedeemed" id="mwe_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodNumberOfUnitsRedeemed" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="EquityMethodInvestmentContribution" id="mwe_EquityMethodInvestmentContribution" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="TaxEffectOfShareBasedCompensationPolicyTextBlock" id="mwe_TaxEffectOfShareBasedCompensationPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ThirdSignificantCustomerMember" id="mwe_ThirdSignificantCustomerMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DeferredTaxAssetsFederalNetOperatingLossCarryforwardsCurrent" id="mwe_DeferredTaxAssetsFederalNetOperatingLossCarryforwardsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxAssetsCapitalLossCarryforwardCurrent" id="mwe_DeferredTaxAssetsCapitalLossCarryforwardCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxAssetsStateNetOperatingLossCarrybackCurrent" id="mwe_DeferredTaxAssetsStateNetOperatingLossCarrybackCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="MarkWestUticaEMGCondensateMember" id="mwe_MarkWestUticaEMGCondensateMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OhioGatheringMember" id="mwe_OhioGatheringMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OhioCondensateMember" id="mwe_OhioCondensateMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BlackhawkMidstreamLLCMember" id="mwe_BlackhawkMidstreamLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SummitMember" id="mwe_SummitMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="TheEnergyAndMineralsGroupMember" id="mwe_TheEnergyAndMineralsGroupMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="VariableInterestEntityOptionAvailableToAcquirePercentageOfVotingInterest" id="mwe_VariableInterestEntityOptionAvailableToAcquirePercentageOfVotingInterest" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="PercentageOfRequiredCapitalContributionByReportingEntity" id="mwe_PercentageOfRequiredCapitalContributionByReportingEntity" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="AggregateCapitalContribution" id="mwe_AggregateCapitalContribution" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="OwnershipPercentageDeterminedUnderRequiredTrueUpTransaction" id="mwe_OwnershipPercentageDeterminedUnderRequiredTrueUpTransaction" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RedeemableNoncontrollingInterestPolicyTextBlock" id="mwe_RedeemableNoncontrollingInterestPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NumberOfManagersConsistedInBoardPriorToCondensateEqualizationDate" id="mwe_NumberOfManagersConsistedInBoardPriorToCondensateEqualizationDate" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="ReceivablesFromEquityInvestmentsForSaleOfAssets" id="mwe_ReceivablesFromEquityInvestmentsForSaleOfAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="OperatingLossCarryforwardsExpirationPeriod" id="mwe_OperatingLossCarryforwardsExpirationPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ConsolidationErrorAndImpairmentMember" id="mwe_ConsolidationErrorAndImpairmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DeferredTaxAssetsOperatingLossCarryforwardsNoncurrent" id="mwe_DeferredTaxAssetsOperatingLossCarryforwardsNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="ClassBPartnerCapitalMember" id="mwe_ClassBPartnerCapitalMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="March2014AtTheMarketOfferingProgramMember" id="mwe_March2014AtTheMarketOfferingProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LineOfCreditFacilityAccordionFeatureMinimum" id="mwe_LineOfCreditFacilityAccordionFeatureMinimum" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AllReportableSegmentMember" id="mwe_AllReportableSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageInvestmentBalanceTargetForDistributionOfAvailableCash" id="mwe_PercentageInvestmentBalanceTargetForDistributionOfAvailableCash" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="OffsettingAssetsAndLiabilitiesTableTextBlock" id="mwe_OffsettingAssetsAndLiabilitiesTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NaturalGasOrNaturalGasLiquidsInStorage" id="mwe_NaturalGasOrNaturalGasLiquidsInStorage" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="CommodityContractsSubjectToMasterNettingArrangementMember" id="mwe_CommodityContractsSubjectToMasterNettingArrangementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CommodityContractNotSubjectToMasterNettingArrangementMember" id="mwe_CommodityContractNotSubjectToMasterNettingArrangementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CurrentAssetsMember" id="mwe_CurrentAssetsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NonCurrentAssetsMember" id="mwe_NonCurrentAssetsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CurrentLiabilitiesMember" id="mwe_CurrentLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NonCurrentLiabilitiesMember" id="mwe_NonCurrentLiabilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OffsettingAssetsAndLiabilitiesLineItems" id="mwe_OffsettingAssetsAndLiabilitiesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionCryogenicNaturalGasProcessingPlantCapacity" id="mwe_BusinessAcquisitionCryogenicNaturalGasProcessingPlantCapacity" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CashPaidAsConsiderationForExtensionOfTermOfKeepWholeProcessingAgreement" id="mwe_CashPaidAsConsiderationForExtensionOfTermOfKeepWholeProcessingAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="BusinessCombinationCashPaidPriorToWorkingCapitalAdjustment" id="mwe_BusinessCombinationCashPaidPriorToWorkingCapitalAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="SouthwestSegmentMember" id="mwe_SouthwestSegmentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="September2013AtTheMarketOfferingProgramMember" id="mwe_September2013AtTheMarketOfferingProgramMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionNumberOfCryogenicNaturalGasProcessingPlantsAcquired" id="mwe_BusinessAcquisitionNumberOfCryogenicNaturalGasProcessingPlantsAcquired" type="xbrli:integerItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="AccountingForChangesInOwnershipInterestsInSubsidiariesPolicyTextBlock" id="mwe_AccountingForChangesInOwnershipInterestsInSubsidiariesPolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AccruedProductAndOperationsCurrent" id="mwe_AccruedProductAndOperationsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AccruedPropertyPlantAndEquipmentCurrent" id="mwe_AccruedPropertyPlantAndEquipmentCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AggregateRequiredCapitalContributedByNoncontrollingOwnersBeforeEntityOptionToContribute" id="mwe_AggregateRequiredCapitalContributedByNoncontrollingOwnersBeforeEntityOptionToContribute" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AdjustmentToAdditionalPaidInCapitalDeferredIncomeTaxImpact" id="mwe_AdjustmentToAdditionalPaidInCapitalDeferredIncomeTaxImpact" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="AmortizationOfPremiumPayments" id="mwe_AmortizationOfPremiumPayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionCostOfAcquiredEntityReceivablesForWorkingCapitalAdjustment" id="mwe_BusinessAcquisitionCostOfAcquiredEntityReceivablesForWorkingCapitalAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="BusinessAcquisitionCryogenicNaturalGasProcessingPlantAdditionalCapacity" id="mwe_BusinessAcquisitionCryogenicNaturalGasProcessingPlantAdditionalCapacity" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="BusinessAcquisitionRefrigerationNaturalGasProcessingPlantCapacity" id="mwe_BusinessAcquisitionRefrigerationNaturalGasProcessingPlantCapacity" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="TemporaryCapitalContributedByPartnershipActual" id="mwe_TemporaryCapitalContributedByPartnershipActual" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="CapitalContributionByPartnershipRetained" id="mwe_CapitalContributionByPartnershipRetained" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="CapitalLossCarryforwards" id="mwe_CapitalLossCarryforwards" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="ClassBPartnerMember" id="mwe_ClassBPartnerMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CollectionOfPaymentsToAcquireIntercompanyNotesNet" id="mwe_CollectionOfPaymentsToAcquireIntercompanyNotesNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="CommodityTypeDomain" id="mwe_CommodityTypeDomain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ConsolidatedAffiliateDividendsOrDistributions" id="mwe_ConsolidatedAffiliateDividendsOrDistributions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestChangesPurchaseOfInterestByParentIncomeTaxBenefit" id="mwe_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestChangesPurchaseOfInterestByParentIncomeTaxBenefit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestChangesPurchaseOfInterestByParentTransactionCosts" id="mwe_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestChangesPurchaseOfInterestByParentTransactionCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentAlternateBaseRateLoanMember" id="mwe_DebtInstrumentAlternateBaseRateLoanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentCovenantInterestCoverageRatio" id="mwe_DebtInstrumentCovenantInterestCoverageRatio" type="xbrli:pureItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentCovenantTotalLeverageRatio" id="mwe_DebtInstrumentCovenantTotalLeverageRatio" type="xbrli:pureItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentCovenantTotalLeverageRatioBeforeAmendment" id="mwe_DebtInstrumentCovenantTotalLeverageRatioBeforeAmendment" type="xbrli:pureItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentIssuePriceAsPercentageOfFaceValue" id="mwe_DebtInstrumentIssuePriceAsPercentageOfFaceValue" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentLIBORLoanMember" id="mwe_DebtInstrumentLIBORLoanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentVariableRateBaseFederalFundsMember" id="mwe_DebtInstrumentVariableRateBaseFederalFundsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DeferredRevenueAdjustment" id="mwe_DeferredRevenueAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="DeferredTaxAssetsDerivativeInstrumentsCurrent" id="mwe_DeferredTaxAssetsDerivativeInstrumentsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxAssetsDerivativeInstrumentsNoncurrent" id="mwe_DeferredTaxAssetsDerivativeInstrumentsNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsCurrent" id="mwe_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsNoncurrent" id="mwe_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxBalanceSettlementPeriodToBeClassifiedAsCurrent" id="mwe_DeferredTaxBalanceSettlementPeriodToBeClassifiedAsCurrent" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DeferredTaxLiabilitiesInvestmentInAffiliatedGroupsNoncurrent" id="mwe_DeferredTaxLiabilitiesInvestmentInAffiliatedGroupsNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="DeferredTaxLiabilitiesNonCurrentAbstract" id="mwe_DeferredTaxLiabilitiesNonCurrentAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DeferredTaxLiabilitiesPropertyPlantAndEquipmentAndIntangibles" id="mwe_DeferredTaxLiabilitiesPropertyPlantAndEquipmentAndIntangibles" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="DistributionEquivalentRightsMember" id="mwe_DistributionEquivalentRightsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DistributionMadeToMemberOrLimitedPartnerPaymentPeriod" id="mwe_DistributionMadeToMemberOrLimitedPartnerPaymentPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LimitedPartnerMaximumShareOfferingLimitedPartnerUnits" id="mwe_LimitedPartnerMaximumShareOfferingLimitedPartnerUnits" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DistributionReceivedAsReimbursementForTemporaryFunding" id="mwe_DistributionReceivedAsReimbursementForTemporaryFunding" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="DocumentAndEntityInformationAbstract" id="mwe_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ElectricityMember" id="mwe_ElectricityMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityContractRelatedAtInceptionOfExtendedPeriod" id="mwe_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityContractRelatedAtInceptionOfExtendedPeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityIncludingInceptionValueAllocableToHostContract" id="mwe_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiabilityIncludingInceptionValueAllocableToHostContract" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="EmbeddedDerivativeRenewalTerm" id="mwe_EmbeddedDerivativeRenewalTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="EmployeeServiceShareBasedCompensationCashFlowEffect" id="mwe_EmployeeServiceShareBasedCompensationCashFlowEffect" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="EquityChangesFromPurchaseOfNoncontrollingInterest" id="mwe_EquityChangesFromPurchaseOfNoncontrollingInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="FacilityCostsIncludingGainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToFacilityExpense" id="mwe_FacilityCostsIncludingGainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToFacilityExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="FacilityCostsLaborAndRelatedExpense" id="mwe_FacilityCostsLaborAndRelatedExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="FacilityExpenseMember" id="mwe_FacilityExpenseMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FacilityExpensesAdjustments" id="mwe_FacilityExpensesAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="FairValueInputsAssetsAndLiabilitiesQuantitativeInformationLineItems" id="mwe_FairValueInputsAssetsAndLiabilitiesQuantitativeInformationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FairValueInputsAssetsAndLiabilitiesQuantitativeInformationTable" id="mwe_FairValueInputsAssetsAndLiabilitiesQuantitativeInformationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FairValueInputsCommodityPrice" id="mwe_FairValueInputsCommodityPrice" type="us-types:perUnitItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="FairValueInputsCrudeOptionVolatilities" id="mwe_FairValueInputsCrudeOptionVolatilities" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FairValueInputsPropaneOptionVolatilities" id="mwe_FairValueInputsPropaneOptionVolatilities" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FairValueInputsPricePerMegaWattHour" id="mwe_FairValueInputsPricePerMegaWattHour" type="us-types:perUnitItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="FairValueInputsProbabilityOfRenewal" id="mwe_FairValueInputsProbabilityOfRenewal" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilitiesNetChangeInUnrealizedGainLossIncludedInEarningsContractHeld" id="mwe_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetAndLiabilitiesNetChangeInUnrealizedGainLossIncludedInEarningsContractHeld" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="FirstAmendmentToAmendedAndRestatedLineOfCreditAfterJoinderAgreementMember" id="mwe_FirstAmendmentToAmendedAndRestatedLineOfCreditAfterJoinderAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FirstSignificantCustomerMember" id="mwe_FirstSignificantCustomerMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FractionationAndStorageFacilitiesMember" id="mwe_FractionationAndStorageFacilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="FundingOfCapitalExpenditureInExcessOfSpecifiedThresholdLimit" id="mwe_FundingOfCapitalExpenditureInExcessOfSpecifiedThresholdLimit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="GainLossOnEarlySettlementOfDerivativeInstrumentsNotDesignatedAsHedgingInstruments" id="mwe_GainLossOnEarlySettlementOfDerivativeInstrumentsNotDesignatedAsHedgingInstruments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToFacilityExpense" id="mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToFacilityExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToProductCost" id="mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToProductCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToRevenue" id="mwe_GainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="GasGatheringAndTransmissionEquipmentAndFacilitiesMember" id="mwe_GasGatheringAndTransmissionEquipmentAndFacilitiesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ImputedInterestRateOnLiability" id="mwe_ImputedInterestRateOnLiability" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="IncomeLossFromAffiliatesSubsidiariesAndHoldingCompany" id="mwe_IncomeLossFromAffiliatesSubsidiariesAndHoldingCompany" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationLineItems" id="mwe_IncomeTaxExpenseBenefitContinuingOperationsIncomeTaxReconciliationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="IncomeTaxReconciliationExpenseBenefitOnIncomeFromClassAUnits" id="mwe_IncomeTaxReconciliationExpenseBenefitOnIncomeFromClassAUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="IncomeTaxReconciliationPriorPeriodAdjustmentsAndChangeInEnactedTaxRate" id="mwe_IncomeTaxReconciliationPriorPeriodAdjustmentsAndChangeInEnactedTaxRate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="IncomeTaxReconciliationTable" id="mwe_IncomeTaxReconciliationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="InitialContributionsRequiredFromNoncontrollingInterestsTotal" id="mwe_InitialContributionsRequiredFromNoncontrollingInterestsTotal" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="InvestmentInAffiliates" id="mwe_InvestmentInAffiliates" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="IsobutaneContractMember" id="mwe_IsobutaneContractMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="KeystoneMidstreamServicesLLCAcquisitionMember" id="mwe_KeystoneMidstreamServicesLLCAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LTIP2002PlanMember" id="mwe_LTIP2002PlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LTIP2008PlanAndHydrocarbonPlan2006Member" id="mwe_LTIP2008PlanAndHydrocarbonPlan2006Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LTIP2008PlanHydrocarbonPlan2006AndHydrocarbonPlan1996Member" id="mwe_LTIP2008PlanHydrocarbonPlan2006AndHydrocarbonPlan1996Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LTIP2008PlanMember" id="mwe_LTIP2008PlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LandBuildingOfficeEquipmentAndOtherMember" id="mwe_LandBuildingOfficeEquipmentAndOtherMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LangleyAcquisitionMember" id="mwe_LangleyAcquisitionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LengthOfRegulatedPipeline" id="mwe_LengthOfRegulatedPipeline" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="FairValueInputsAssetsAndLiabilitiesQuantitativeInformationTableTextBlock" id="mwe_FairValueInputsAssetsAndLiabilitiesQuantitativeInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LibertyMember" id="mwe_LibertyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AggregateContributionsToVIEThreshold" id="mwe_AggregateContributionsToVIEThreshold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="LimitedPartnerMaximumValueOfferingLimitedPartnerUnits" id="mwe_LimitedPartnerMaximumValueOfferingLimitedPartnerUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="LineOfCreditFacilityAccordionFeatureMaximum" id="mwe_LineOfCreditFacilityAccordionFeatureMaximum" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="LineOfCreditFacilityCapacityAvailableForLettersOfCredit" id="mwe_LineOfCreditFacilityCapacityAvailableForLettersOfCredit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="LineOfCreditFacilityRemainingBorrowingCapacityOnLongTermBasisBasedOnFinancialCovenantsRequirements" id="mwe_LineOfCreditFacilityRemainingBorrowingCapacityOnLongTermBasisBasedOnFinancialCovenantsRequirements" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="MarkWestHydrocarbonMember" id="mwe_MarkWestHydrocarbonMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="MarkWestLibertyMidstreamMember" id="mwe_MarkWestLibertyMidstreamMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NoncontrollingOwnersPreferenceThreshold" id="mwe_NoncontrollingOwnersPreferenceThreshold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="MinimumCapitalContributedByNoncontrollingOwners" id="mwe_MinimumCapitalContributedByNoncontrollingOwners" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="MinimumVariableInterestEntityOwnershipPercentage" id="mwe_MinimumVariableInterestEntityOwnershipPercentage" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="MinorityInterestInOperatingIncomeLossLimitedPartnerships" id="mwe_MinorityInterestInOperatingIncomeLossLimitedPartnerships" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="MinorityInterestOwnershipPercentageAcquiredByPartnership" id="mwe_MinorityInterestOwnershipPercentageAcquiredByPartnership" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="MinorityInterestPurchaseConsiderationCashPaid" id="mwe_MinorityInterestPurchaseConsiderationCashPaid" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="MiscellaneousIncomeNetMember" id="mwe_MiscellaneousIncomeNetMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NaturalGasContractMember" id="mwe_NaturalGasContractMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NaturalGasMember" id="mwe_NaturalGasMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NaturalGasMidstreamCostsIncludingGainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToProductCost" id="mwe_NaturalGasMidstreamCostsIncludingGainLossOnPriceRiskDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsRelatedToProductCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="NaturalGasolineContractMember" id="mwe_NaturalGasolineContractMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NetOperatingMargin" id="mwe_NetOperatingMargin" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="NoncontrollingInterestIncreaseFromContribution" id="mwe_NoncontrollingInterestIncreaseFromContribution" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="NonmonetaryNotionalAmountOfEmbeddedDerivativeInCommodityContract" id="mwe_NonmonetaryNotionalAmountOfEmbeddedDerivativeInCommodityContract" type="xbrli:pureItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="PeriodOfArrearsForPaymentOfManagementFeeRevenues" id="mwe_PeriodOfArrearsForPaymentOfManagementFeeRevenues" type="xbrli:durationItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OtherEquityInterestsDisclosureAbstract" id="mwe_OtherEquityInterestsDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OtherEquityInterestsDisclosureTextBlock" id="mwe_OtherEquityInterestsDisclosureTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfOtherEquityInterestsTable" id="mwe_ScheduleOfOtherEquityInterestsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OtherEquityInterestsLineItems" id="mwe_OtherEquityInterestsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageEquityInterestAcquired" id="mwe_PercentageEquityInterestAcquired" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="PercentageOfAdditionalEquityInterestAcquired" id="mwe_PercentageOfAdditionalEquityInterestAcquired" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DistributionReceivedFromSubsidiary" id="mwe_DistributionReceivedFromSubsidiary" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="OwnershipInterestSoldPercentage" id="mwe_OwnershipInterestSoldPercentage" type="num:percentItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LineOfCreditBearingInterestOf4.5PercentMember" id="mwe_LineOfCreditBearingInterestOf4.5PercentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="LineOfCreditBearingInterestOf2.4PercentMember" id="mwe_LineOfCreditBearingInterestOf2.4PercentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="RevenueAdjustmentForUnconsolidatedAffiliate" id="mwe_RevenueAdjustmentForUnconsolidatedAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="FacilityExpenseAndPurchaseProductCostAdjustmentsForUnconsolidatedAffiliate" id="mwe_FacilityExpenseAndPurchaseProductCostAdjustmentsForUnconsolidatedAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="PortionOfOperatingIncomeLossAttributableToNoncontrollingInterestsOfUnconsolidatedAffiliate" id="mwe_PortionOfOperatingIncomeLossAttributableToNoncontrollingInterestsOfUnconsolidatedAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
</xsd:schema>


