Exxon Valdez was built with a single hull; this could be for many different reasons many of them we will never know for sure. But speculating on a couple is possible one could be for the purposes of cost. With a company owning the Exxon Valdez they want to be making money instead of spending it. Another reason could be that they just did not see the need for a double hull. A double hull does provide more protection but does reduce the capacity of the tanker as they are adding another hull in, or a tank to old the oil within the tanker.
No matter the reason the company of Exxon choice to only have one hull within the Exxon Valdez they did not mitigate the risks associated with what they were doing. It can be said that when you do something all the time, it becomes habit for you and you no longer see the risks and dangers associated with it. Exxon has been transporting and dealing with oil for so long it that it is now second nature.
The company could have over looked the risk involved with transporting oil within the sound due to a spill like this never happening before. The risks that were present and they did not take steps to avoid them by simply placing a double hull on the Exxon Valdez. Having a double hull might have avoided the spill all together. Although this is an assumption this is plausible. The side of the tanker was not ripped open very deeply but instead just enough and for a very long way. Having a double hull would have meant that the tanker would not have been able to sail. This is due to the tanker being stuck on the reef but also because the space between the hull and the tank with the oil could have been filled with water thus making it possible for the ship to sink.
Within history we always look back and say this could have been done because we know the outcome of the event. But with disasters it is always slightly different due to the nature of people more times than not being harmed in the process. But we can look at the risks and what mitigations of risks were known about and taken previous to the disaster. The single hulled ships were something that was a known risk as other tankers had double hulls. The fact that Exxon did not have a double hull and was one of the newer ships was a risk. But this risk did not play out for the company as the tanker ran onto the reef and was ripped open. Within risks of transporting something like oil in waters that were known to have icebergs, which are harmful to all ships if it, and in and around such a diverse ecological place was dangerous. The simple fact that it was oil was also a very large risk. All of these risks have to be mitigated to some point even if this point is knowing they are there and then choosing to do nothing about them.
Leacock, Elipheth. The Exxon Valdez Oil Spill. Facts on File Inc., 2005.
Hernan, Robert Emmet., Bill McKibben. This borrowed Earth: Lessons form the 15 Worst Environmental Disasters Around the World. St. Martin’s Press, 2010.