I would say that in the last four or five years the major investments have been into new gasoline hydrotreaters for the new legislation on sulphur in gasoline, and also a new distillate hydrotreater, which is about $300 million, to remove the sulphur in the diesel. Also, we invested into a continuous—that may be a technical term—reformer. It's a profitability project to improve the yields in the molecules and the value of the yield in the refinery.
For the $600 million remaining in front of us over the next five years, it's made up of about $250 million of turnaround, and those are moneys you have to do maintenance in your processing unit after two years, four years, five years. So each unit has a different cycle for maintenance. The most obvious one is the catalytic cracking unit in September and the alkylation unit. It's about $50 million that we have to spend right now. Then in the springtime we have a crude unit in the hydrogen plant that needs to have a huge shutdown, which is about $70 million. So you have about $250 million of these kinds of moneys.
The remaining is money for process safety issues like control rooms. We do have to move control rooms to other locations for safety purposes of the people, especially based on BP toxicity and that kind of event. We do have a water treatment plant that is at the end of its life. So some vessels... We have derogation calculations for safety margins that can last a few more months, but they are at the end of their lives. That's about another $60 million for those.
We have a boiler that can go on like that for a while. We have a boiler on the catalytic cracker unit, which is $40 million, that is at the end of its life.
Those are basic units that are essentially at the end of their lives.