Total Cost Assessment (TCA) is the consideration of all environmental and health costs associated with a decision, including direct costs, risks and liabilities and costs borne by others.  A TCA enables a better decision making process by evaluating all the "what if's" correlated to the choices. The process allows the key stakeholders to look beyond the obvious costs to those that aren't typically on a company's balance sheets, like public image, brand value and employee morale to name just a few.
A TCA would have brought  experts together beforehand to analyze the probability and the costs (environmental, social and economic) of the risks associated with drilling an oil well a mile below sea level in the Gulf of Mexico.  They would have come up with scenarios, both positive and negative, that could occur as a result of the decision to drill the well. Some of the scenarios would have included an approximate, let's say, 0.5% probability of failure of the blowout preventer, a 5% probability of a methane burst, and some probability of a failure of the shut off valve, a series of cascading probabilities that result in some small probability that the well would simply gush its contents into the gulf. 
During the TCA process a discussion would have been had about an explosion and the potential liabilities around that including whether the spill was contained or not contained.  It is likely that a BP human resource person would talk about the affect the deaths of the workers might have on employee morale, while the BP public relations person would raise concern over a quick containment foreseeing the costs borne by others, specifically the gulf coast fishing industry, if large amounts of oil were released in to the sea.  The BP brand value person would have given an estimate on the costs if the well was contained or not contained; likely saying that "it would cost very little" if it was contained, and "it could cost BP billions" if not contained.  With these expert's opinions, the TCA would have placed a range of let's say $0-$5B on brand value cost if the current scenario happened in the future.
And right then in the discussion, someone might say, "What can we do to eliminate that risk? And if we can't eliminate it, what can we do to keep it at the low end of that cost range? Let's include that in our planning." If they didn't, the potential costs of the spill to the company would continue to add up and up, resulting in a small, but real probability that they would have huge losses.

So with the TCA showing potential for significant losses, the next step would be to conduct a sensitivity analysis into what situation could cause that to happen. As before, the team would look at the costs to eliminate or contain these situations and add these into the analysis. Most likely, they would have found a relatively inexpensive backup (including additional testing and inspections at each step in the process) and also had several containment options at the ready.

We invite your thoughts and comments and hope to get your wheels spinning about your own sustainability pathways!