Entirely apart from the economic and political question of cost, a double hulled tanker might be more at risk of capsizing in some circumstances.
Other questions were scientific. The short term environmental cost of the spill was clear enough. The Exxon Valdez spill caused, it was to be reported, the greatest toll to wildlife of any industrial accident in history, including Chernobyl (Egan, 1990). But what of the long term? What of the wildlife that wasn't killed outright, but was made sick, or whose descendents might be made sick? What would be the effect of oil ingestion as it moved up the food chain, as fish ate oil rich microorganisms; as birds ate oil polluted fish? How long would the damage persist, and in what known or unexpected) forms (Laycock, 1990)?
Still other questions were political and administrative and therefore, ultimately, ethical. The Exxon Valdez oil spill was a marine accident, not, as in the Persian Gulf in late 1990 and early 1991, a deliberate act of war, crime, or "ecocide." In almost all marine accidents, some human factor is ultimately identified, but in the case of the Exxon Valdez, the human factor loomed particularly large. The Exxon Valdez did not go aground in a raging storm. It went two miles off course and ran aground, in perfect sea and navigating conditions, only a few miles from the terminal from which it had departed. In command on the ship's bridge was its third officer, who was not licenced to command a ship like the Exxon Valdez in those waters. The Captain was below, at his desk, tending to paperwork when his ship went aground. Coast Guard officers and emergency response personnel who encountered him several hours later reported smelling alcohol on his breath. Had he been operating the ship (or rather, delegating its operation) while intoxicated? He turned out to have several drunk driving convictions. Should Exxon have intrusted a man with such a record with...