Proposals to close the Minneapolis Upper Harbor, and convert the area to housing, light industry and recreational uses, would eliminate the barge movement of commodities to/from the Upper Harbor. Several proposals have assumed that this would also eliminate associated freight movement through this area of Minneapolis. However, there would still be a need to move materials such as sand and gravel, cement, steel products, and other construction materials into Minneapolis; and scrap metals from Minneapolis. Truck movements of grain, fertilizer and other commodities from/to northwest of Minneapolis would be rerouted over land through or around Minneapolis to utilize downstream harbors. This study estimates the private costs and public externality costs imposed by this 'modal shift' from barge to truck. These cost estimates include private haulage costs, the public costs due to changes in highway maintenance requirements, and externalities due differences in fuel consumption, changes in air emissions, highway congestion impacts, and highway accident impacts. Facility relocation and required public and private infrastructure investments were not estimated. Coefficients from the FHWA Highway Cost Allocation Study (HCAS) are used to monetize the estimated public and externality costs. Results from the "most likely" scenario indicate an addition of 66,000 truckloads traveling 1.2 million miles in the metro area each year. Increases in transport costs to shippers or customers exceed $4 million annually, increases in highway maintenance exceed $.6 million while public externality costs estimated with the HCAS coefficients exceed $.48 million annually. Results from the "transitional" scenario indicate an addition of 66,000 truckloads traveling 1.6 million miles in the metro area each year. Increases in transport costs to shippers or customers exceed $5.1 million annually; increases in highway maintenance exceed $.93 million while public externality costs estimated with the HCAS coefficients exceed $.68 million annually.