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Water and sediment samples from Lake Powell indicate that the reservoir, including its San Juan arm, is returning to normal after last month's Gold King Mine spill.
Levels of 24 heavy metals — including arsenic, cadmium, mercury and lead — remain unchanged from those seen before the Gold King Mine spilled into the Animas and San Juan rivers, according to data released by the EPA. The samples, taken in mid-August, also show that previously elevated levels of metals have returned to normal in the San Juan.
The concentration of heavy metals in both water bodies is well-below recreational screening levels, meaning contact with the water should be safe for even the most vulnerable populations.
According to a release from the National Parks Service, the concentration of heavy metals at Lake Powell also meets drinking water standards. However, the service continues to advise visitors to bring their own water or to purify lake water before drinking.
There are no safety advisories or closures in place at Lake Powell, according to the NPS. Local watercraft businesses, including those offering boat tours and rentals, are operating as normal.
The EPA test results confirmed the results of independent samples collected by state scientists, which also indicated Lake Powell and the San Juan were safe for recreational use.
Donna Spangler, a spokeswoman for the Utah Department of Environmental Quality, said the state plans to continue monitoring water quality for long-term impacts.
"Even though we're happy that the water results are good, we're still going to continue our long-term monitoring," she said. "We're not going to call it good just yet, because we still need to understand the long-term impacts."
Water quality experts have said the water reaching Utah and Lake Powell was less contaminated by the spill because the initial plume from the Gold King Mine was diluted as it traveled downstream. Additionally, they said, most of the heavy metals the plume contained fell out of the water column and settled into the river's sediment upstream.
But some scientists have expressed concerns that this metal-laden sediment could enter the water column again and wash downstream when the river's flow picks up in the future.