Evidence in an enforcement case is, well, yeah, important (as are rules governing clean up standards)
The important thing here is that the simple allegation that the lessee was responsible for drums of oil later to have found to have leaked wasn't sufficient evidence to convict without more proof of responsiblity and of the actual contents. On the first issue, the owner had apparently died after calling DEP to claim that the tenant had left the offending mess. Without any other evidence that the offending drums and items were put on the property while it was under the defendant/lessee's control, there wasn't competent substantial evidence to support responsibility. As to the content, DEP claimed that used oil had spilled, but never tested the substance to show it was used oil. It pled poverty, that it couldn't afford to test at all its sites. It then tried to claim that inspectors' examination of the oil was sufficient evidence that it was used to throw the burden on the lessee to show that it wasn't used oil. The Court rejected that approach, holding that the agency can't shift the burden of proof to the defendant this way.
And as to the last issue: DEP apparently had been using clean up standards for soil contamination that it had never adopted as rules, even though it had been specifically directed by statute to do so by July 1, 2004. The court not only held that DEP could not enforce the non-rule standards, it also remanded for the entrance of trial and appellate attorney's fees.
The lesson: in an enforcment action, the burden is on the agency, not the defendant, and that goes throughout the proceeding and to all the critical elements. And while not discussed here, remember that all such penal actions are governed by the clear and convincing evidence test.
And if you're an agency directed to adopt rules, you probably should adopt them.