When the Nevada Division of Environmental Protection released a revised report on polluted groundwater in May 2020, the agency’s administrator said in a press release that the report would “chart a path forward based on the best available science” for cleaning up a toxic mine. But a review of more than 2,000 pages of records shows the “best available science” was the product of negotiation between NDEP and a company.

In May, state regulators approved a revised report holding the mine responsible for less than half of the potential contamination previously modeled, a conclusion far more favorable for ARCO. In the long term, it could mean a less extensive and less expensive aquifer cleanup.

Nearly two decades since the mine’s last operator declared bankruptcy, workers are starting to cut off contamination pathways under an EPA deal deferring oversight of the vast cleanup to state regulators. The trickiest and potentially most long-lasting decision will come in selecting how to address the contaminated groundwater.