The users created such a run of tongue-in-cheek photographs of supposed paradise that the company was forced to issue a warning.
The operator, Siberian Generating Co., acknowledged in a statement the site had become a "social media star" but urged people to take caution around it.
"It is not poisonous," the company said of the water, adding that "the radiation level is normal" according to tests by two laboratories.
But the water has a high pH value from the coal ash that is pumped into it, and the conditions can cause allergic reactions, the company said. "We strongly ask that while hunting for selfies you don't fall in the ash dump!"
And although the company warned people that it's "almost impossible" to get out of the dump's muddy bottom, some social media users ventured to the lake's edge or even onto paddleboards on the water. Beside the effluent pond, women in bikinis and summer dresses struck poses as if enjoying the tropical sun on a sandy beach. One woman posed with an inflatable pink flamingo.
Some people delicately inserted a foot into the chemical slurry, as if testing the temperature for a dip.
And a newlywed couple posted a series of pictures by the blue water, so iridescent it seemed nearly to sparkle, as a backdrop for their new life together. In a comment with one of the photos, the photographer wrote that no one had held a picnic at the site or actually splashed in the water.
"At the same time, it seems to me that the 'danger' has been slightly exaggerated," she wrote. "Naturally, you shouldn't swim there, but for the length of an hourlong photo shoot, you won't grow a third hand."
Other users posted less inviting photos: Some showed the hulking, rusting pipes that carry the ash slurry from the power station to the pond or caught in the background the smokestacks, a feature the city is more typically known for.
Written by: Andrew E. Kramer
© 2019 THE NEW YORK TIMES