Lake Riley Proposed for Removal From Impaired List
Minnesota regulators propose delisting the 297-acre Eden Prairie-Chanhassen lake after more than a decade of water-quality improvement.
Updated on Nov. 9, 2026 in Environmental
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Minnesota proposed removing Lake Riley from the state's impaired waters list, which it was first placed on in 2002 for excess nutrients. Three related Riley Purgatory Bluff Creek Watershed District water bodies are also poised for delisting.
Why it matters
Lake Riley's proposed delisting reflects sustained water-quality gains over more than a decade, including fewer beach closures for Eden Prairie residents who use Riley Lake Park. The change remains subject to final approval from the U.S. Environmental Protection Agency.
Lake Riley has met phosphorus standards for 10 years and water clarity standards for 12 years, while meeting chlorophyll-a standards in seven of the past 10 years. Final approval from the U.S. Environmental Protection Agency is still pending.
The players
Riley Purgatory Bluff Creek Watershed District
A special-purpose local government unit that manages water resources across the Riley Purgatory Bluff Creek watershed, including Lake Riley and its related water bodies.
Leslie Stovring
A longtime water resources coordinator who has served for 25 years and helped guide the lake's restoration efforts.
The details
Lake Riley, a 297-acre lake on the Eden Prairie-Chanhassen border, was listed as impaired for aquatic recreation in 2002 due to excess nutrients. Beach closures are now rare, and no hazardous algae blooms were detected in 2026, though a 2025 bloom followed an unseasonably warm spring.
Timeline
2002: Lake Riley first listed as impaired for aquatic recreation.
2016 and 2020: Alum treatments applied to Lake Riley.
2025: Algae bloom follows an unseasonably warm spring.
2026: No hazardous algae blooms detected in Lake Riley.
Fall 2027: Possible start of 1.5-mile Riley Creek restoration.
Big Picture
Lake Riley's proposed removal from Minnesota's impaired waters list, a designation tied to the federal Clean Water Act, follows a listing that began in 2002. The change would mark a formal end to a nutrient-pollution listing that had persisted for more than two decades.
Eden Prairie residents who visit Riley Lake Park may find fewer beach closures as water quality continues to improve. The lake's proposed delisting reflects long-term progress that could support recreation on the lake in coming years.
The takeaway
Sustained monitoring and targeted treatments, including carp control and stormwater filtration, have produced more than a decade of measurable gains at Lake Riley. Readers interested in local water health can follow city and watershed district updates as the delisting process moves forward.
What happens next
Work could begin as early as fall 2027 on a 1.5-mile restoration of Riley Creek, and an alum treatment is under consideration for Lake Susan. Final approval from the U.S. Environmental Protection Agency is still required before Lake Riley is delisted.
Further reading
For more on local water quality efforts, see Environmental coverage across the region.
Source note: This article includes information reported by Hometownsource.
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