UPDATE 7/14/25: Rapid City Public Works and South Dakota Game, Fish and Parks officials this morning provided the following updates on Saturday’s fish kill at the lake in Memorial Park.
Jeremy Kientz, Area Fisheries Supervisor with the South Dakota Game, Fish and Parks Department, provided the following statement to city officials Monday morning:
“This weekend, we had a partial fish kill at Memorial Pond caused by an algal bloom. Hot weather, sunlight and nutrient-rich runoff (like lawn fertilizer) can fuel algae growth. When the blooms of algae die off, the decomposing matter rapidly consumes oxygen. This scenario results in low dissolved oxygen levels causing fish mortality.
“As a result the water may appear green or murky, and you may notice a foul smell in addition to dead fish and crayfish near the shorelines. We will continue to monitor the situation and crews will continue working to clean up fish carcasses.”
City Public Works officials also conducted tests Saturday and were conducting additional tests today (Monday). Tests have been conducted on the water, boat launch and discharge bridge.
“On Saturday, Water Reclamation lab staff collected water samples and conducted in-house testing for dissolved oxygen levels,” said City Water Reclamation Superintendent Dave Van Cleave. “Results indicated concentrations around 3 parts per million (ppm).
“These low levels are likely attributable to elevated temperatures and an algae bloom, which can deplete oxygen and render aquatic life unsustainable, a natural ecological occurrence.”
Testing is also being conducted for ammonia and E. coli. Some test results will not be available until later in the week. Additional analysis will be performed by the City’s external consultant, Midcontinent.
City parks officials indicate there will likely to be a foul odor around the lake for several days. Local and state officials will continue cleanup efforts at the lake Monday. State officials indicate Saturday’s incident was not a complete fish loss, estimating the fish kill at about a quarter of the lake’s fish population.
UPDATE: Rapid City Parks crews are continuing cleanup efforts today at Memorial Park Lake following a significant fish die-off. State Game, Fish and Parks crews are also expected to join the effort on Monday to assist with the ongoing situation.
State and local officials have been on-site since midday, assessing the situation and collecting water samples to determine the cause of the fish deaths.
The public is still advised to avoid contact with the water at Memorial Park Lake. Additionally, anyone fishing in the lake is urged to practice catch-and-release, returning any fish caught to the water until test results are available.
Further updates will be provided as more information becomes available from the testing and investigation.
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RAPID CITY, S.D. – City officials have closed access to Memorial Lake in Memorial Park following reports of numerous dead fish floating on the water and a foul odor emanating from the pond Saturday morning.
Authorities are on-site monitoring the situation and have advised the public to avoid the water. Investigations are underway, with the City of Rapid City’s water department and the South Dakota Game, Fish and Parks Department (SDGF&P) collaborating to determine the cause.
SDGF&P officials are expected to conduct cleanup efforts and water testing throughout the day. The public is urged to steer clear of the pond area for safety reasons and to allow crews to work.
Memorial Lake is a popular fishing spot within Memorial Park, a significant green space in the heart of Rapid City, offering recreational opportunities to residents and visitors of the Black Hills region. The city’s primary drinking water sources are not connected to Memorial Lake.
Further updates will be provided as information becomes available.