Massey lawyer Dan Stickler, however, insists the documents found there aren't new. He claims they were listed on an index provided to the plaintiffs in 2007, and the plaintiffs simply failed to follow up.
"They can't benefit from their own negligence in failing to look at the documents we provided,'' Stickler said. "Every time they've requested something, we've bent over backward to provide it. ... We don't have anything to hide.''
In that vault, investigators found maps in unmarked storage bags. But plaintiffs' attorney Kevin Thompson said his team found even more documents in the attic Wednesday, and they plan to keep searching.
The maps contain information about the location of injection bore holes, how long they were used and other facts the plaintiffs consider critical to their case.
Bunch argues that when one underground void was full, Massey simply diverted the flow to another one until the slurry levels dropped -- apparently migrating from one coal seam down into another.
"They knew the slurry would escape because it did on several occasions,'' Bunch said, claiming the company failed to properly seal the mine voids to prevent that migration.
It was, he argued, "calculated, long-term methodology'' to dispose of Massey's waste, dupe regulators about the extent of its operations and endanger neighboring communities solely to save money.
Massey denied lying to regulators and continued to insist its Mingo County operations harmed no one.
For decades, coal companies in Appalachia have injected slurry into worked-out mines as a cheap alternative to dams and other systems that can safely store or treat it.
Although the plaintiffs are now mostly served by a public water system, they say chronic exposure to metals and chemicals in the slurry are to blame for birth defects, developmental disabilities and a range of other ailments.
The judges are set to hear another round of motions in the case Friday and could rule on whether the parent corporation can be held liable for the activities of the subsidiary, which Massey claims was an independent company.