Sunnyside Gold Corp. has offered one of its waste storage sites north of Silverton as a permanent solution for a place to put the sludge generated from the water-treatment plant that was built after the Gold King Mine spill in 2015.
The Environmental Protection Agency built a $1.5 million temporary water-treatment plant north of Silverton in October 2015, three months after a contracted crew triggered the Gold King Mine blowout, which sent a torrent of mine waste down the Animas and San Juan rivers.
The water-treatment plant, which takes in discharges out of the Gold King Mine, adds lime to the mine wastewater to raise the pH of the water so that dissolved, potentially toxic metals become solid and can settle in settling ponds.
The process, while highly effective in improving water quality, generates a lot of sludge. EPA officials said the plant puts out about 4,600 cubic yards of sludge a year, enough to cover an entire football field in more than 2 feet of the waste byproduct.
Where to put the sludge, however, has been a point of contention.
The EPA had initially stored the sludge – which is considered non-hazardous – at the site of the water-treatment plant in an area known as Gladstone, about 6 miles north of Silverton along County Road 110.
But in spring 2018, the EPA announced it was running out of room.
As a last ditch option, the EPA said it was going to haul the sludge over two mountain passes, through Durango, to the Bondad landfill – a more than 70-mile, one-way journey and include an estimated 700 trips a year.
The proposal, which was generally opposed by local officials in Durango and Silverton, became obsolete after the EPA entered an agreement with a property owner who owns the Kittimac tailings pile, a historic mine-waste pile about 6 miles northeast of Silverton along County Road 2.
In a sort of science experiment, the EPA mixed the sludge and the Kittimac tailings. The idea, agency officials said, is that the mixture will bind up metals in the tailings pile, and as a result, be less likely to leach metals into ground or surface water.
That project is expected to be complete this summer. EPA will then cover the mixture in more than a foot of soil, then restore the 8-acre site.
But the Kittimac tailings site was only a temporary solution. Cynthia Peterson, spokeswoman for EPA, said the agency has no further plans to transport sludge to Kittimac, and based on current conditions, Gladstone will again be at capacity in 2021.
Kevin Roach, a spokesman for Sunnyside Gold, said the company recently granted EPA access to evaluate the possibility of long-term storage at the Mayflower tailings repository, a large series of impoundments of mine waste rock along County Road 2.
“(The Mayflower impoundment) is an ideal and proven site for a repository for the water-treatment plant, and, in the interest of good faith and improving water quality, SGC has granted EPA access for this evaluative work,” Roach wrote in an email to The Durango Herald.
Peterson said EPA “appreciates” the offer and said the agency will start by conducting field observations and taking samples of surface and groundwater conditions.
“The investigation will determine the physical, chemical and moisture conditions that could affect the stability of the tailing impoundments in the event that a repository is constructed on them,” she said.
Sunnyside Gold’s offer comes just a month after the company denied an EPA work order to conduct various cleanup projects as part of the Bonita Peak Superfund Mining District site, declared a year after the Gold King Mine spill.
Sunnyside Gold, the last company to operate a mine in Silverton, which shut down in 1991, argued it has done its part to help improve water quality in the Animas River headwaters. The EPA, however, considers the company on the hook for additional cleanup costs.
Peterson said EPA has no further information to report about the situation.