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The Anaconda Copper Mine on Sept. 11, 2019. (David Calvert/The Nevada Independent)

The Nevada Division of Environmental Protection (NDEP) is defending a groundwater report that reduced the extent of uranium and arsenic contamination linked to the former Anaconda Copper Mine in Yerington, an agricultural town about 70 miles from Reno. 

In a letter sent to tribal leaders, local politicians, state legislators and two federal agencies on Tuesday, NDEP Administrator Greg Lovato said he stood by the process used for the report. 

The letter came about one week after The Nevada Independent published NDEP emails and documents that highlighted concerns about the science and process used in the report.

“While groundwater geochemistry and contaminant hydrology at the Site are complex, the process NDEP used to revise the estimated extent of groundwater with contamination from the mine is straightforward,” Lovato wrote in the letter. “As NDEP Administrator, drawing on my career of more than 14 years at US EPA and 15 years at NDEP, I stand by it 100%.”

Under federal pollution laws, ARCO, a one-time mine owner, is responsible for cleaning up the tainted water. In 2016, consultants for ARCO wrote and submitted a key document known as a Background Groundwater Quality Assessment, or BGQA. The BGQA, approved by the EPA, found extensive groundwater contamination associated with the past practices at the mine. 

In 2017, ARCO filed a draft report that relied on the BGQA and appeared ready to use the model to guide the cleanup. At the time, ARCO consultants noted that it was using the BGQA findings, at the EPA’s direction “to conservatively-establish the extent of mine-impacted water.” 

Then, a few months later, in early 2018, the dynamic of the mine cleanup shifted.

In February 2018, the Trump administration deferred oversight of the cleanup to NDEP. After the deferral, ARCO submitted new analyses arguing that the past mining was responsible for far less contamination. Much of the contamination, the company argued in new technical memos, was the result of naturally-occurring processes or associated with irrigation from nearby farms.

Two years after the oversight of the mine was deferred from the EPA to NDEP, state regulators signed off on a revised groundwater report that significantly reduced the scope of contamination estimated in 2016 and approved by the EPA. A recent Nevada Independent story, which relied on emails and documents obtained through the Nevada Public Records Act, outlined concerns raised by technical experts related to the science and process that went into the revised report. 

In the letter, Lovato noted that NDEP and the company differed on some issues, and in March 2020, the agency pushed back. NDEP notified the company that it must make certain changes, or face a work takeover and potential fines. But the letter acknowledges that the report did reduce the extent of mine-related groundwater contamination, compared to the BGQA.

“In the end, the extent of mine related groundwater contamination in the approved report was less than in the EPA’s previous estimate in the BGQA Report but more than what ARC was attempting to demonstrate,”  Lovato wrote (the line was formatted in bold text).

Starting in December, NDEP declined multiple opportunities to respond to most of The Nevada Independent’s questions or provide additional context to explain the public records and process.

But in the letter Tuesday, Lovato offered additional background on how the revision came to be. 

Lovato said the original groundwater report, approved by the EPA, recognized that farming and naturally occurring mineralization could influence water quality. But where the EPA-approved report offered a broad, conservative estimate of the mine-impacted groundwater contamination, NDEP’s approach was to separate, as best as possible, the role of each contamination pathway. 

That process led to a reduction in how much groundwater was linked to the mine, and a large portion of the previously documented mine contamination was attributed to naturally occurring processes and agriculture. After the site was deferred in 2018, the letter said, “NDEP recognized that selecting and enforcing a cleanup solution” in the complicated aquifer “would be difficult and contested.”

Under NDEP, the company, Lovato wrote, was required to “analyze different and additional lines of evidence related to understanding the extent of the Site related groundwater contamination.”

That process did not substantiate the findings in the EPA-approved BGQA, Lovato wrote. 

Based on the additional technical information, including analyzing groundwater hydraulics, “NDEP determined that a complete analysis of all the lines of evidence did not reasonably support the extent of mine related contamination included in the BGQA report,” Lovato said. 

The report is part of a larger process to develop a solution for cleaning up the tainted water. 

On Tuesday, Lovato argued that “the potential effect of the change in estimated extent of groundwater contamination from the mine on [ARCO] responsibility has yet to be determined.”

“It is not yet clear that the reduced extent of groundwater contamination attributed to mine activity will result in a different cleanup plan for this multiple use, interconnected aquifer system north of the former mine Site,” Lovato wrote, noting that future assessments will be conducted.

The letter was addressed to Lyon County Commission Chair Vida Keller, Yerington Mayor John Garry, Yerington Paiute Tribe Chairman Ginny Hatch and Walker River Paiute Tribe Chairman Amber Torres. The Yerington Paiute Tribe shares the same aquifer used by the former mine.

NDEP sent a copy of the letter to four state legislators, the chair of the State Environmental Commission and representatives from the EPA and the U.S. Bureau of Land Management.

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