Debra Reid, File, Associated Press
FILE - In this Nov. 30, 2004 file photo, an evaporation pond holds contaminated fluid and sediment at the former Anaconda copper mine near Yerington, Nev. Federal environmental regulators are waiting to hear any last-minute objections from Nevada's governor before formally moving ahead with their proposal to add a contaminated, abandoned mine in rural Yerington to the national list of priority Superfund sites. The U.S. Environmental Protection Agency wants to place the former Anaconda copper mine on the Superfund's National Priority List. That would make the site 70 miles southeast of Reno eligible for federal funds to pay for 90 percent of the tens of millions of dollars needed to begin permanent cleanup efforts.

RENO, Nev. — Gov. Brian Sandoval was still wrestling Friday with whether to end the state's opposition to adding a toxic, abandoned mine in western Nevada to a list of the country's most contaminated sites that would make it eligible for federal money to begin cleanup.

U.S. Environmental Protection Agency officials notified Sandoval last month that if they don't hear from him by the end of Friday, they intend to publish a proposed rule as early as March to put the former Anaconda copper mine in Yerington on the Superfund's National Priority List.

The World War-II era mine is already a federal Superfund site, a designation that secured federal help with pinpointing the pollution's source and keeping it from spreading. Adding it to the priority list would make the mine eligible for federal funds to pay for 90 percent of the tens of millions of dollars needed to begin cleaning up the site that was abandoned 16 years ago.

Critics fear the listing would be a black eye for the rural community, creating a stigma that could affect property values

Last month, Sandoval directed state experts to revisit the matter and come up with a recommendation before the deadline. The governor's aides said Friday afternoon he had not yet provided the EPA with an answer.

In 2013, rural neighbors of the mine won a $19.5 million settlement from companies they accused of covering up the contamination of drinking water wells. EPA tests showed rural wells were tainted by uranium and other toxic chemicals that had leaked for decades from the mine about 70 miles southeast of Reno.

EPA regional administrator Jared Blumenfeld last month told Sandoval he needed to know by Jan. 29 whether the state has an alternative cleanup proposal.

Blumenfeld said the agency is running out of time to get funding proposals in the pipeline and head off concern about the risk of hazardous chemicals escaping from the aging site in the next few years. He said in a letter that Sandoval could provide input during the rule-making process that will take more than a year.

The mine covers 6 square miles of land owned partly by the U.S. Bureau of Land Management. Atlantic Richfield acquired the property in 1977 from Anaconda Copper, which built the mine in 1941.

Blumenfeld said the most immediate threat is the estimated 90 million gallons of acidic solution that was left in the heap leach and fluid management system.

"The reason for urgency is that funding needs to be in place well before the current pond capacity is exceeded," Blumenfeld wrote in a Dec. 22 letter, noting the Nevada Division of Environmental Protection made a concerted effort to secure private funding but has been unsuccessful.

The situation demands constant management to avoid further leakage from the storage ponds, or an overflow, Blumenfeld said.

"The consequence of either could result in significant additional threat to the Mason Valley Groundwater Basin," he said.

Construction on a remedy needs to start by summer 2019, Blumenfeld said.

The state projected last year it would cost $30.4 million to address the most pressing concerns at the mine.

Sandoval has said local officials and agriculture leaders in the area continue to contact his office with concerns about the EPA's proposal.

"The state must weigh the financial responsibility of managing the site exclusively and the risk associated with labeling the community as a Superfund site indefinitely with any potential health concerns that might exist," he said.