Environmental officials said Thursday their long-term concern after the 3 million-gallon Gold King Mine spill centers around the metallic sediment left in its wake.
Specifically, the Environmental Protection Agency says it is worried about the potential stirring up of sediment during “high-water events” and the sludge’s effect on people who are continually recreating for long periods — several weeks — of time.
The EPA mentioned the concerns as part of a data release accompanying 77 pages of documents chronicling the minutes and hours before and after the agency-triggered spill. The Aug. 5 disaster sent yellow-orange sludge through three states and two American Indian tribes, prompting emergency declarations and leaving communities along hundreds of river miles angry.
The EPA says data, collected over the past two weeks, shows surface water metal levels at 24 sampling locations along the watershed below the spill are “trending toward pre-event conditions.” Metal levels in the sediment, the EPA says, are below the agency’s recreational screening level.
However, the EPA says it is not certain there are no health risks from the sediment.
“Risks to humans from metals in the sediments are based upon the total exposure a person may have over a given period of time,” David Gray, an EPA spokesman, said. “Exposure from sediments would be from hand-to-mouth exposures. We want to ensure that the concentration of metals in the sediments are sufficiently low enough to ensure that a recreational person will not be exposed to harmful levels of metals.”
The EPA says it is establishing a longer term watershed monitoring strategy for surface water affected by the spill to identify potential extended impacts.
The effects of the Gold King spill on aquatic life still remain unknown, state wildlife officials say, but no immediate, widespread impacts have been observed. Joe Lewandowski, spokesman for Colorado Parks and Wildlife, says his agency is looking into two dead beavers found north of Durango after the disaster.
Testing on the beavers, and fish placed in the river to study the impacts of the spill, have not been finished. A fish survey on the Animas River through Durango completed this week preliminarily indicated there were not any immediate problems, CPW said.
“Basically, the fish population doesn’t look any different from what it was last summer,” Lewandowski said. “We’re not seeing fish in distress or anything that would have been an acute effect.”
Lewandowski noted, however, fish populations in the Animas through Durango have been declining for about a decade from what officials believe is the ongoing leaching of mine contaminants into the river’s watershed. He said it won’t be known in the short term if the Gold King spill will have any impact on that trend.
“The effects or more long term,” he said.
Experts say metals lining the riverbed could continue impact agriculture, aquatic life and other life-forms along the Animas River for years.
The EPA specifically has been studying concentrations of arsenic, cadmium, lead and mercury in surface water. The acidic heavy metals that flooded into Cement Creek in Silverton and the Animas River through La Plata County after the spill initially broke state water quality limits.
The new data comes after the EPA on Wednesday released an internal review of the events leading up the Gold King spill showing crews underestimated waste pressure behind the mine’s collapsed opening.
The report called the underestimation of the pressure the most significant factor leading to the spill.
According to the report, had crews drilled into the mine’s collapsed opening, as they had done at a nearby site, they “may have been able to discover the pressurized conditions that turned out to cause the blowout.”