With much of the recent focus on the Cement Creek drainage, the major sources for metal loading into the reaches of the Upper Animas River remain a bit of a mystery for researchers.
Yet Sunnyside Gold Corp.’s four massive tailings ponds along the Upper Animas River – about a mile northeast of Silverton, above the confluence with Cement Creek – have long been under suspicion.
“From Arrastra Gulch down to Silverton, there is a substantial amount of metal loading, and it’s not clear where that is coming from,” said Peter Butler, a coordinator with the Animas River Stakeholder’s Group. “The sources are not as identifiable as Cement Creek.”
From the late 19th century to the early 20th century, miners routinely dumped any by-product from metal extraction directly into rivers or lakes throughout the highly productive Silverton caldera.
In the 1930s, Sunnyside began hauling ore from Gladstone through Silverton and up what is now County Road 2 to the Mayflower Mill for processing. Only 5 percent of the ore contained precious metals.
The leftover 95 percent of waste rock, which usually contained heavy metals that included cadmium, copper and lead, was dumped beside the mill until 1992. The four piles now stretch about a mile and a half.
Sunnyside over the years has conducted numerous projects to reduce the leeching of metals into the Upper Animas, including covering the piles with clay to reduce the entry of water and digging diversions to prevent groundwater from seeping into the ponds.
Still, high concentrations of metals continue to load, according to data collected by the stakeholder’s group. Butler said in March and April, more concentrations of metals can enter the river along that stretch than all the loading that discharges from Cement Creek, considered the worst polluter in the mining district.
On Tuesday, Silverton native Larry Perino, a spokesman for Sunnyside, revealed the results of sampling conducted last year during high-flow and low-flow points to the stakeholder’s group.
Water samples taken within the tailings pond showed levels of cadmium, copper and six other metals that exceeded Colorado Department of Public Health and Environment standards. Within the Animas River along that stretch, cadmium and copper were the only metals in excess.
However, the results leave many gaps for researchers characterizing the watershed. Testing occurred only a few days in May and September, and neglected the historically high period of metal concentrations that occur in March and April.
When questioned, Perino doubted the veracity of the historical data and cited the company’s tight time frame for testing. He later added those months would have been difficult to take samples given the inclement weather.
“I think it’s impossible (to draw conclusions) unless you’re out there weekly,” said Perino, adding the company has no further plans to test this summer.
Regardless, the next steps for remediating the tailings ponds are unknown. The site, owned mostly by Sunnyside, a subsidiary of mining conglomerate Kinross, is included on the Environmental Protection Agency’s proposed Superfund listing, raising uncertainty over jurisdiction and responsibility. Sunnyside, one of the region’s largest and longest running mining operations, could be targeted as a potentially responsible party, despite years of undergoing voluntary cleanup projects aimed at being cleared of further liability.
“Right now, there are no formal agreements between EPA and Sunnyside,” said Rebecca Thomas, the EPA’s manager for the Superfund site. “So if they chose to collect data, that’s certainly their prerogative. We’ve had a cooperative relationship historically, and I think that will stay.”
Doug Jamison with the state health department said it’s too early to draw conclusions on just how much Sunnyside’s tailings contribute to the overall metal loading in the Animas watershed.
“I think there’s a lot of evaluation that needs to be done,” he said. “On the other side of the valley, there are also some potential sources.”
Indeed, of the 48 mine-related waste sites included in the Superfund listing, nearly 30 are along the stretches of the Upper Animas.
Perino said testing was done at Howardsville, above the tailings, to compare how water quality changed during its flow downstream, but he did not have that information available.
In the coming summer months, the tailings – designated a National Historic Landmark in 2000 – will be the subject of further scrutiny.
“In general, I think people were hoping (Tuesday) for a more definitive answer,” Butler said. “But I think what we learned is that it’s a difficult thing to figure out.”