Neither Whittier or Seward have the capacity to handle that volume of freight, and I don't think either is configured for large container ships at present. The Alaska Railroad is single track, this means only one train at a time can travel most sections. We would have to significantly improve the railroad to accommodate this extra traffic. Even if the trains were running 24x7 and all passenger /tourism travel was suspended it would be hard to move everything in and out of Whittier or Seward in a timely fashion, both are remote locations clinging to rocks on the edge of a mountain and far removed from the bulk of the population. This plan would be a logistical nightmare, the port of Anchorage could be built and rebuilt several times over for the costs of railroad improvements, fuel, dock upgrades, etc.