McNabb was out of compliance with the state, not the EPA. The state then contracted out the enforcement to EPA. It would be safe to say that the state employees found McNabb to be abrasive and confrontational and advised the feds of this.
It is difficult to draw conclusion as to what McNabb may or may not done because of two things. First, the regulaters are not granting interviews and second, the media never gets the technical details correct.
There is one thing that is clear however. McNaab stated that his employees were required to clean the equipment with the Zep coumpound which is 90% hexane. The man should have his ass whipped and thrown in jail for that. This fact also gives one the insight into what else he may or may not have done.