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  <element name="CompanyMatchingPercentageOnFirstTenThousandDollarEmployeeContributions" id="nwpx_CompanyMatchingPercentageOnFirstTenThousandDollarEmployeeContributions" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostOfRemedyExpectedToBeAllocatedAmongPotentiallyResponsibleParties" id="nwpx_CostOfRemedyExpectedToBeAllocatedAmongPotentiallyResponsibleParties" type="xbrli:integerItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostsAndEstimatedEarningsInExcessOfBillingsAndBillingsInExcessOfCostsAndEstimatedEarningsNet" id="nwpx_CostsAndEstimatedEarningsInExcessOfBillingsAndBillingsInExcessOfCostsAndEstimatedEarningsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsAndBillingsInExcessOfCostsAndEstimatedEarningsTextBlock" id="nwpx_CostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsAndBillingsInExcessOfCostsAndEstimatedEarningsTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostsAndEstimatedEarningsOnContractsInExcessOfBillingsBalanceSheetAbstract" id="nwpx_CostsAndEstimatedEarningsOnContractsInExcessOfBillingsBalanceSheetAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostsIncurredAndEstimatedEarningsOnUncompletedContracts" id="nwpx_CostsIncurredAndEstimatedEarningsOnUncompletedContracts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CostsIncurredOnUncompletedContracts" id="nwpx_CostsIncurredOnUncompletedContracts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="CustomerPrepaymentsPolicyTextBlock" id="nwpx_CustomerPrepaymentsPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetNetOperatingLossCarryforwardsCurrent" id="nwpx_DeferredTaxAssetNetOperatingLossCarryforwardsCurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetOtherAssetsNoncurrent" id="nwpx_DeferredTaxAssetOtherAssetsNoncurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetsCostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContracts" id="nwpx_DeferredTaxAssetsCostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContracts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetsNetOperatingLossCarryforwardNoncurrent" id="nwpx_DeferredTaxAssetsNetOperatingLossCarryforwardNoncurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetsOtherNoncurrent" id="nwpx_DeferredTaxAssetsOtherNoncurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefitsNonCurrent" id="nwpx_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefitsNonCurrent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxAssetTradeReceivableNet" id="nwpx_DeferredTaxAssetTradeReceivableNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxExpenseBenefitFromStockOptionsExercised" id="nwpx_DeferredTaxExpenseBenefitFromStockOptionsExercised" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DeferredTaxLiabilitiesNetNonCurrentClassificationAbstract" id="nwpx_DeferredTaxLiabilitiesNetNonCurrentClassificationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DefinedContributionPlanNumberOfInvestmentOptions" id="nwpx_DefinedContributionPlanNumberOfInvestmentOptions" type="xbrli:integerItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DividendDistributionUnderShareholderRightsPlan" id="nwpx_DividendDistributionUnderShareholderRightsPlan" type="xbrli:integerItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DocumentAndEntityInformationAbstract" id="nwpx_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeContributionPercentageForWhichCompanyWillMatchAtFiftyPercent" id="nwpx_EmployeeContributionPercentageForWhichCompanyWillMatchAtFiftyPercent" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EquipmentUnderCapitalLeaseMember" id="nwpx_EquipmentUnderCapitalLeaseMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EstimatedCostOfEpaSelectedRemedy" id="nwpx_EstimatedCostOfEpaSelectedRemedy" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EstimatedEarningsOnUncompletedContracts" id="nwpx_EstimatedEarningsOnUncompletedContracts" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EstimatedTimeToCompleteSelectedEpaRemedy" id="nwpx_EstimatedTimeToCompleteSelectedEpaRemedy" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FederalAndStateDeferredIncomeTaxExpenseBenefit" id="nwpx_FederalAndStateDeferredIncomeTaxExpenseBenefit" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="IncomeTaxImpactsDueToReclassification" id="nwpx_IncomeTaxImpactsDueToReclassification" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InventoryCurrentAndNonCurrentNet" id="nwpx_InventoryCurrentAndNonCurrentNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InvestmentsInNonqualifiedRetirementPlanAssets" id="nwpx_InvestmentsInNonqualifiedRetirementPlanAssets" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LongTermDebtAnnualRepaymentDueAmount" id="nwpx_LongTermDebtAnnualRepaymentDueAmount" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaturityPeriodForForwardContracts" id="nwpx_MaturityPeriodForForwardContracts" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumDurationOfOperatingLeases" id="nwpx_MaximumDurationOfOperatingLeases" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumMaturityPeriodForForwardContracts" id="nwpx_MaximumMaturityPeriodForForwardContracts" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumPerformanceAwardsIssuedMultiplier" id="nwpx_MaximumPerformanceAwardsIssuedMultiplier" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MinimumPercentageOfLikelihoodOfTaxBenefitBeingRealizedUponSettlement" id="nwpx_MinimumPercentageOfLikelihoodOfTaxBenefitBeingRealizedUponSettlement" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MinimumPerformanceAwardsIssuedMultiplier" id="nwpx_MinimumPerformanceAwardsIssuedMultiplier" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NonQualifiedRetirementSavingsPlanActuarialYearlyAssetGrowthPercentageAssumption" id="nwpx_NonQualifiedRetirementSavingsPlanActuarialYearlyAssetGrowthPercentageAssumption" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NonQualifiedRetirementSavingsPlanTargetBenefitAmount" id="nwpx_NonQualifiedRetirementSavingsPlanTargetBenefitAmount" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NonrecurringFairValueMeasurementImpairmentCharge" id="nwpx_NonrecurringFairValueMeasurementImpairmentCharge" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NotionalAmountOfForwardContractsWithMaturityPeriodsGreaterThanTwelveMonths" id="nwpx_NotionalAmountOfForwardContractsWithMaturityPeriodsGreaterThanTwelveMonths" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfActiveStockIncentivePlans" id="nwpx_NumberOfActiveStockIncentivePlans" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfCustomersWithReceivableBalanceInExcessOfTenPercentOfReceivables" id="nwpx_NumberOfCustomersWithReceivableBalanceInExcessOfTenPercentOfReceivables" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfDefinedBenefitPensionPlans" id="nwpx_NumberOfDefinedBenefitPensionPlans" type="xbrli:integerItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfInactiveStockOptionPlans" id="nwpx_NumberOfInactiveStockOptionPlans" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfManufacturingFacilityLocationsWaterTransmission" id="nwpx_NumberOfManufacturingFacilityLocationsWaterTransmission" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfNonContributoryDefinedBenefitPlans" id="nwpx_NumberOfNonContributoryDefinedBenefitPlans" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfSeriesJuniorParticipatingPreferredStockSharesReserved" id="nwpx_NumberOfSeriesJuniorParticipatingPreferredStockSharesReserved" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OfficerContributionForWhichCompanyWillMatchAtFiftyPercent" id="nwpx_OfficerContributionForWhichCompanyWillMatchAtFiftyPercent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingLossCarryforwardExpirationYearLowerLimit" id="nwpx_OperatingLossCarryforwardExpirationYearLowerLimit" type="xbrli:gYearItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OperatingLossCarryforwardExpirationYearUpperLimit" id="nwpx_OperatingLossCarryforwardExpirationYearUpperLimit" type="xbrli:gYearItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PermalokCorporationMember" id="nwpx_PermalokCorporationMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PortlandHarborNaturalResourcesTrusteeCouncilMember" id="nwpx_PortlandHarborNaturalResourcesTrusteeCouncilMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyPlantAndEquipmentNetLocatedInMexico" id="nwpx_PropertyPlantAndEquipmentNetLocatedInMexico" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PurchasePriceUnderRights" id="nwpx_PurchasePriceUnderRights" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="QuarterlyFinancialDataLineItems" id="nwpx_QuarterlyFinancialDataLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="QuarterlyFinancialDataTable" id="nwpx_QuarterlyFinancialDataTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="RangeFiveMember" id="nwpx_RangeFiveMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RangeFourMember" id="nwpx_RangeFourMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RangeOneMember" id="nwpx_RangeOneMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RangeThreeMember" id="nwpx_RangeThreeMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RangeTwoMember" id="nwpx_RangeTwoMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReclassificationsRecognizedInCostOfSales" id="nwpx_ReclassificationsRecognizedInCostOfSales" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ReclassificationsRecognizedInNetSales" id="nwpx_ReclassificationsRecognizedInNetSales" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RestrictedStockUnitsAndPerformanceAwardsMember" id="nwpx_RestrictedStockUnitsAndPerformanceAwardsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RetirementPlanExpense" id="nwpx_RetirementPlanExpense" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="RightRedemptionValue" id="nwpx_RightRedemptionValue" type="num:perShareItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfChangesInAccumulatedOtherComprehensiveIncomeLossTableTextBlock" id="nwpx_ScheduleOfChangesInAccumulatedOtherComprehensiveIncomeLossTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfCostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsAndBillingsInExcessOfCostsAndEstimatedEarningsTableTextBlock" id="nwpx_ScheduleOfCostsAndEstimatedEarningsInExcessOfBillingsOnUncompletedContractsAndBillingsInExcessOfCostsAndEstimatedEarningsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfInventoryCurrentAndNonCurrentTableTextBlock" id="nwpx_ScheduleOfInventoryCurrentAndNonCurrentTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfSegmentReportingInformationBySegmentBalanceSheetsTextBlock" id="nwpx_ScheduleOfSegmentReportingInformationBySegmentBalanceSheetsTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ScheduleOfSegmentReportingInformationBySegmentStatementOfOperationsTextBlock" id="nwpx_ScheduleOfSegmentReportingInformationBySegmentStatementOfOperationsTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SelectEmployeeContributionForWhichCompanyWillMatchAtFiftyPercent" id="nwpx_SelectEmployeeContributionForWhichCompanyWillMatchAtFiftyPercent" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesBTermLoanMember" id="nwpx_SeriesBTermLoanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesCTermLoanMember" id="nwpx_SeriesCTermLoanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesDTermLoanMember" id="nwpx_SeriesDTermLoanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SeriesTermLoanMember" id="nwpx_SeriesTermLoanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberAtTargetLevelOfPerformance" id="nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberAtTargetLevelOfPerformance" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAwardExpirationPeriod" id="nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAwardExpirationPeriod" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByStockBasedPaymentAwardGrantDateFairValue" id="nwpx_ShareBasedCompensationArrangementByStockBasedPaymentAwardGrantDateFairValue" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAbstract" id="nwpx_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRange" id="nwpx_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRange" type="num:perShareItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeAbstract" id="nwpx_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareholderRightsPlanDisclosureTextBlock" id="nwpx_ShareholderRightsPlanDisclosureTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShortTermInventoriesAbstract" id="nwpx_ShortTermInventoriesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SummaryOfSignificantAccountingPoliciesLineItems" id="nwpx_SummaryOfSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SummaryOfSignificantAccountingPoliciesTable" id="nwpx_SummaryOfSignificantAccountingPoliciesTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="TaxCreditCarryForwardExpirationYear" id="nwpx_TaxCreditCarryForwardExpirationYear" type="xbrli:gYearItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ThresholdForDisclosureSalesRepresentedByIndividualCustomer" id="nwpx_ThresholdForDisclosureSalesRepresentedByIndividualCustomer" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TotalReclassificationsForPeriod" id="nwpx_TotalReclassificationsForPeriod" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ValueOfExercisedRight" id="nwpx_ValueOfExercisedRight" type="xbrli:decimalItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WorkersCompensationInsurancePolicyTextBlock" id="nwpx_WorkersCompensationInsurancePolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>
