Fines levied against those responsible for certain environmentally damaging accidents are now so high that it costs a company responsible for such an accident more to pay the fine than it would have cost to adopt measures that would have prevented the accident.
Conclusion (Therefore)
Businesses that might have environmentally damaging accidents will now install adequate safeguards.
Evidence (since)
Fines for such accidents are now higher than the cost of the measures that would have prevented them.
Businesses value their profits.
Evaluate
The author's logic is a cost comparison. Prevention is cheaper than the fine. Businesses want to keep their money. So businesses will choose prevention.
How could we argue that "businesses won't install adequate environmental safeguards"? We'd have to try to argue that it is still somehow more cost effective to be environmentally delinquent than to pay for the preventative measures.
The fine is higher than the preventative measures, but are those the only costs we need to consider?
Is the chance of getting fined so low, that over time it's worth gambling on the idea that you won't get fined? (There's a passage in RC that talks about how the penalty for corporate crimes would have to be like 10x the money they save/make from committing those crimes, because there's only like a 10% chance they get caught. You have to factor in that detection ratio when you consider the cost of the fine vs. the cost of compliance.)
Goal
Look for an answer that gives us a way to say that profit-seeking businesses might still skip the safeguards, either by showing how that is still the cheaper route or by showing that they are not deterred by the large fines (because they don't know about them or don't think it'll happen to them).