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        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:href="nwpx-20140630_cal.xml" xlink:title="Calculation Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:href="nwpx-20140630_def.xml" xlink:title="Definition Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:href="nwpx-20140630_lab.xml" xlink:title="Label Links, all"/>
      <link:linkbaseRef xlink:type="simple" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:href="nwpx-20140630_pre.xml" xlink:title="Presentation Links, all"/>
    </appinfo>
  </annotation>
  <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <import namespace="http://fasb.org/us-types/2013-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2013/elts/us-types-2013-01-31.xsd"/>
  <import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd"/>
  <import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd"/>
  <import namespace="http://fasb.org/us-gaap/2013-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/country/2013-01-31" schemaLocation="http://xbrl.sec.gov/country/2013/country-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/currency/2012-01-31" schemaLocation="http://xbrl.sec.gov/currency/2012/currency-2012-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/dei/2013-01-31" schemaLocation="http://xbrl.sec.gov/dei/2013/dei-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/exch/2013-01-31" schemaLocation="http://xbrl.sec.gov/exch/2013/exch-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/invest/2013-01-31" schemaLocation="http://xbrl.sec.gov/invest/2013/invest-2013-01-31.xsd"/>
  <import namespace="http://xbrl.sec.gov/stpr/2011-01-31" schemaLocation="http://xbrl.sec.gov/stpr/2011/stpr-2011-01-31.xsd"/>
  <element name="AmountAnticipatedToSpentForFurtherSourceControlWork" id="nwpx_AmountAnticipatedToSpentForFurtherSourceControlWork" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="AssetsAndLiabilitiesOfDiscontinuedOperationsTableTextBlock" id="nwpx_AssetsAndLiabilitiesOfDiscontinuedOperationsTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessAcquisitionPurchasePriceAmountHeldInEscrowToSecureIndemnificationObligations" id="nwpx_BusinessAcquisitionPurchasePriceAmountHeldInEscrowToSecureIndemnificationObligations" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="BusinessCombinationIncreaseDecreaseToReflectLiabilitiesAcquiredAtFairValueAbstract" id="nwpx_BusinessCombinationIncreaseDecreaseToReflectLiabilitiesAcquiredAtFairValueAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ContingentConsiderationLiabilityFairValue" id="nwpx_ContingentConsiderationLiabilityFairValue" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTax" id="nwpx_DiscontinuedOperationIncomeLossFromDiscontinuedOperationNetOfTax" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DisposalGroupIncludingDiscontinuedOperationCostOfGoodsSoldRefunded" id="nwpx_DisposalGroupIncludingDiscontinuedOperationCostOfGoodsSoldRefunded" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" 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="EstimatedCostOfEpaSelectedRemedy" id="nwpx_EstimatedCostOfEpaSelectedRemedy" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" 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="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="MaturityPeriodForForwardContracts" id="nwpx_MaturityPeriodForForwardContracts" 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="MinimumPerformanceAwardsIssuedMultiplier" id="nwpx_MinimumPerformanceAwardsIssuedMultiplier" type="num:percentItemType" abstract="false" xbrli:periodType="duration" 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="NumberOfInactiveStockOptionPlans" id="nwpx_NumberOfInactiveStockOptionPlans" type="xbrli:integerItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfPotentiallyResponsibleParties" id="nwpx_NumberOfPotentiallyResponsibleParties" type="xbrli:integerItemType" abstract="false" xbrli:periodType="instant" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OilCountryTubularGoodsMember" id="nwpx_OilCountryTubularGoodsMember" type="nonnum:domainItemType" abstract="true" 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="ReclassificationsForPeriod" id="nwpx_ReclassificationsForPeriod" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" 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="ScheduleOfChangesInAccumulatedOtherComprehensiveIncomeLossTableTextBlock" id="nwpx_ScheduleOfChangesInAccumulatedOtherComprehensiveIncomeLossTableTextBlock" 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="ScheduleOfSegmentReportingInformationBySegmentStatementOfOperationsTextBlock" id="nwpx_ScheduleOfSegmentReportingInformationBySegmentStatementOfOperationsTextBlock" type="nonnum:textBlockItemType" abstract="false" 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="ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceStockAwardVestingPeriod" id="nwpx_ShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceStockAwardVestingPeriod" 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="ShortTermInventoriesAbstract" id="nwpx_ShortTermInventoriesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TubularProductsMember" id="nwpx_TubularProductsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WaterTransmissionGroupMember" id="nwpx_WaterTransmissionGroupMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>
