Wyoming environmental regulators who tested the waters of a crowded and stunning Wind River Range lake last summer did not detect the same worrisome concentrations of fecal bacteria that federal regulators uncovered three years earlier.
At issue is Lonesome Lake, a 35-acre waterbody at the base of the Cirque of the Towers that generated headlines after the Environmental Protection Agency published its most recent National Lakes Assessment. The western Wyoming backcountry lake contained more Enterococci — a bacteria indicative of fecal matter — than any of the other 981 lakes surveyed randomly around the country. The concentration registered 384 times greater than the EPA’s safety criteria for swimming.
The concerning one-time test result from a summer 2022 water sample triggered a multi-agency investigation. Last summer, water quality specialists on five occasions made the 20-plus mile roundtrip to and from the headwaters of the North Popo Agie River to take additional tests for E. coli, a more commonly used fecal bacteria marker. On Wednesday, the Wyoming Department of Environmental Quality published its results.
“We’re not showing any indications of public recreation risk, based on our E. coli sample,” said David Waterstreet, the state agency’s watershed protection manager.
Lonesome Lake was well below the DEQ threshold designed to protect people from getting sick from swimming, he said.
“Currently, it is meeting that criteria,” he said.
In fact, zero of 10 Lonesome Lake samples had any detectable E. coli. The water was gathered from both the east and southern shorelines in the peak summer backpacking and climbing seasons.
The complete absence was unexpected and a stark contrast to the results from the EPA’s summer 2022 Enterococci reading, which remains “unexplained” in the view of DEQ surface water monitoring supervisor Jeremy ZumBerge.
“I can’t explain why the value was as high as it was,” ZumBerge said. “Whether that was real or not real remains a bit of a mystery.”
In some regards, the EPA’s earlier test results were not completely surprising.
‘Poop Lake’
Lonesome Lake has long had a reputation for being unsafe due to human feces, with some even giving it the moniker Poop Lake. A staffer at Pinedale’s Great Outdoor Shop told WyoFile last summer that his shop advises Wind River Range travelers to steer clear of standing water in the Cirque of the Towers.
“I tell people definitely do not swim in there, I tell people definitely do not drink the water,” Brian Cromack said. “It’s been heavily contaminated for a long time, just via the negligence of outdoor recreation enthusiasts over the years.”
Seated at between 10,000 and 13,000 feet in the Shoshone National Forest, the Cirque of the Towers and its Lonesome Lake have long been among the most visited destinations in the Winds. There’s a camping prohibition within a quarter mile of the shoreline due to crowding, and a trail counter shows that use crests at 400 visitors a week during the peak summer. Many of the backpackers, climbers, dogs and livestock using the basin have to go poop while traveling through the cirque’s small, 2-square-mile watershed.
“There’s a longstanding view that there potentially are water quality issues there due to the amount of recreation in the area,” ZumBerge said.
Shoshone National Forest spokesman Evan Guzik reiterated the point.
“Considering the historical anecdotal reports and elevated Enterococci from 2022, visitors should continue to use caution when recreating in Lonesome Lake or using it as a drinking water source,” Guzik said.
No corroboration
But at least for now, the DEQ has not found any data corroborating the human health hazard.
Wyoming water quality specialists would typically proceed to their next sampling target if they don’t detect a pollutant in the first year of looking, but they’re considering replicating their efforts in summer 2026 because of the public interest in Lonesome Lake.
“It’s not an easy undertaking — 20-mile day hikes — to get samples,” ZumBerge said. “We discussed whether the effort was really worth it, but … we are seriously evaluating doing this again.”
Wyoming Department of Environmental Quality staffers who sampled Lonesome Lake five times in 2025 also sampled Big Sandy Lake, another highly trafficked waterbody on the opposite side of the Continental Divide. They again detected no E. coli.
There are flowing waters in the region that contain unsafe concentrations of E. coli, however.
Lander Creek, just to the southwest, has long suffered from a feces-related impairment, though DEQ has proposed to reclassify and delist the Wind River Range stream. A 14-mile stretch of the Sweetwater River has also been tagged as unfit for immersive recreation because of bacteria that could make swimmers sick.
“Our monitoring targets both reservoirs and rivers and streams,” said Waterstreet, DEQ’s watershed protection manager. “Over the history of evaluating different types of waters, we typically find E. coli pathogens more often when we’re in a stream network.”