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A dead fish is seen in Mill Creek after concrete was spilled into the water.

A dead fish is seen in Mill Creek on Thursday, July 29, 2021. According to state officials, some concrete was spilled into Mill Creek near 3800 South and Upland Drive this week during an I-215 reconstruction project. Biologists have confirmed that the increased PH levels in the water from the spill have caused a significant fish kill.

Patrick Fink

Residents urged to avoid Mill Creek water after concrete spill, ‘significant’ fish kill-off

SHARE Residents urged to avoid Mill Creek water after concrete spill, ‘significant’ fish kill-off
SHARE Residents urged to avoid Mill Creek water after concrete spill, ‘significant’ fish kill-off

Residents and people who recreate at Mill Creek west of I-215 are being urged to avoid the creek for the time being as environment crews continue to assess a concrete spill that entered the water Thursday.

The spill happened as crews continued to work on a massive project reconstructing I-215 in the area of 3540 South late Thursday afternoon, according to Utah Department of Transportation spokesman John Gleason. It's unclear what caused the spill, but UDOT environment specialists and the contractor working on the project worked to "try and address it right away," he added.

Crews were able to stop the spill from continuing to leak concrete into the creek but an unknown amount ended up in the water. Samantha Heusser, with the Utah Division of Water Quality, said concrete traveled from the spill point at I-215 to at least as far west as 500 East in South Salt Lake.

She added there is no known impact on any drinking water in the area but the span of dozens of blocks includes some popular walking and hiking spots and is near homes. The above-normal pH levels are why officials advise residents and those recreating in the area to avoid the water and to also keep their pets away from it at any location west of I-215.

"Increased pH levels can irritate the skin," Gleason said. "They can be harmful to pets, and we want to make sure we avoid any of those issues."

Teams from the Utah Department of Environmental Quality, Salt Lake County Health Department, and Utah Division of Wildlife Resources were called in to further assess the environmental impact on the creek. Those teams remained at the scene Friday.

"We're working to understand the environmental impacts of this spill," said Ashley Sumner, a spokeswoman with the Utah Department of Environmental Quality, adding that it's resulted in foam and water discoloration in the area.

Anyone who has come in contact with the water since the incident should wash off their skin and contact their health care provider if they experience any skin irritation, said Salt Lake County Health Department spokesman Nicholas Rupp. He added there isn't as much of a consumption concern for humans as there is for pets that may play in foam that has formed.

Spill leads to ‘pretty significant’ fish kill-off

What is known so far is that it had a devastating impact on the fish that swim in the creek. Patrick Fink, a nearby resident, posted photos of dead fish in the creek on social media after the spill, describing the creek as "chalk white."

Faith Heaton Jolley, a spokeswoman for the Utah Division of Wildlife Resources, told KSL.com Friday that there was a "pretty significant" fish kill-off but the full extent isn't clear because wildlife biologists had only been able to get from the I-215 spill site to about 2000 East as of Friday afternoon. Jolley said there have been some reports of dead fish as far west as the creek's confluence with the Jordan River, but it was unclear if that's tied to spill or unrelated factors.

Dead fish found in Mill Creek following a concrete spill on I-215 in Millcreek on Thursday, July 29.

Dead fish found in Mill Creek following a concrete spill on I-215 in Millcreek on Thursday, July 29.

Patrick Fink

The division doesn't have an estimate of the number of fish killed, but the creek is home to about 500 fish per mile — mostly Bonneville cutthroat and brown trout.

"We're not saying yet that it's a total fish kill in that area, but just from the initial surveys is does seem like it's been pretty significant," Jolley said. "We'll know more total numbers as we do more surveys."

Biologists believe the high pH levels detected in the creek are the largest factor for the kill-off.

"Typically concrete has a lime as a big ingredient and there's a high pH component due to its acidity, and that can kill fish because of the increased pH levels in the water. And they just can't really tolerate any significant changes in pH level, especially when it happens quickly like it did in this instance," Jolley added. "And then, obviously, that's in conjunction with some of the other stressors we're seeing right now like low, warm water levels due to drought."

Areas upstream of I-215, which include a trout restocking area and popular spots for fishing, weren't impacted by the spill.

Cleanup to last a few days

What caused the spill remains under investigation, Gleason said. He anticipates that cleanup from it will take at least a few days.

"(Crews are) anticipating that the cleanup should be completed within the next week or so but that, again, is initial information, and that information could change as we learn more," he said.

State environmentalists will continue to monitor the water throughout the weekend and through the end of the cleanup to ensure that it's "effective and protective" of both human and environmental health, Sumner added.

Meanwhile, residents who may have questions or concerns about the affected creek are encouraged to call a hotline set up at 844-909-3278.