Federal judges on Tuesday dismissed Sunnyside Gold Corp.’s attempt to challenge some of the Environmental Protection Agency’s listing of mines in the Superfund site north of Silverton – its own properties included.

The U.S. Court of Appeals D.C. Circuit issued the decision Tuesday to deny Sunnyside’s petition, which was filed by the mining company – a “potentially responsible party” in the Superfund cleanup – in December 2016.

Sunnyside had argued that of the 48 mining sites in the upper Animas River watershed the EPA included in the “Bonita Peak Mining District Superfund” site, 29 had not been properly evaluated and should be removed.

Sunnyside owns two of the 29 sites mentioned, including the Sunnyside Mine and the Mayflower tailings.

“We have no objections to there being a Superfund listing,” Sunnyside spokesman Larry Perino previously said. “The petition is only challenging the unlawful listing of sites that were not assessed at all under the EPA’s own Hazard Ranking System.”

Perino did not immediately respond to requests for comment Tuesday afternoon.

However, the U.S. Court of Appeals D.C. Circuit decision says the EPA did act lawfully and within its own protocols in the Superfund process.

In determining whether the mining district around Silverton qualified for a Superfund listing, the EPA scored 19 pollution sources under the agency’s Hazard Ranking System.

Each of the sources received a high enough score that indicated pollution was bad enough to be eligible for a Superfund listing. As a result, EPA proposed the entire mining district, scored and unscored sources, should be listed.

The Bonita Peak Mining District Superfund site was declared in September 2016.

Months later, Sunnyside argued the EPA was wrong to create a Superfund site that had unscored sources, claiming the EPA must score each contributing source of contamination before adding it to the broader Bonita Peak site.

But the court said text of the HRS process “alone is enough to refute this assertion,” which says a Superfund “may include multiple sources and may include the area between sources.”

“The BPMD is a site (comprised) of the 19 scored sources and the areas ‘between’ them, as the HRS explicitly permits,” the court said. “Sunnyside’s mine falls into the category of an ‘area between sources’ and therefore did not need to be scored.”

The court said: “Sunnyside’s real concern became apparent at oral argument. It claims its mine has been fully remediated and had no part in the present pollution of the site, but it may nevertheless be required to pay for some or all of the cleanup.”

Sunnyside Gold is considered the largest “potentially responsible party” in the district – a term the EPA uses for entities it considers financially on the hook for cleanup.

The company – now owned by international mining conglomerate Kinross Gold Corp. – formed in 1985 and shuttered Silverton’s last operating mine in 1991.

Sunnyside has performed millions of dollars worth of cleanup projects over the years, but the vast mining network, located up Cement Creek, is largely recognized as contributing to the worst area of mine pollution in the drainage.

An agreement with the state of Colorado to place three bulkheads in the 1990s to stop drainage from the Sunnyside Mine released the company of its liability under the Clean Water Act, but not from responsibility from Superfund.

The bulkheads are believed to have backed up mine wastewater to the point where it has caused other mines to start to discharge, specifically the Gold King Mine, where the EPA triggered a blowout in August 2015.

Recently, Sunnyside released two reports arguing “further study would be wasteful and is not required” in understanding the mines around Silverton, and that the best solution would be for EPA to continue its water-treatment plant near Gladstone.

Sunnyside’s other site – the Mayflower tailings along the Animas River north of Silverton – is also considered a major culprit of pollution. Yet the company in its recent report claimed metal loading comes from elsewhere.

The company went onto say the only “potentially responsible parties” in the district are the EPA, Bureau of Land Management and the U.S. Forest Service.

jromeo@durangoherald.com