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Parks director pitches health guidelines for Lake Mitchell

If guidelines proposed Tuesday were approved in 1991, the city would have discouraged people from direct contact of Lake Mitchell at least 66 times. In an effort to protect swimmers and recreational users of Lake Mitchell, Parks and Recreation Di...

Green algae flows along the western bank of Lake Mitchell just north of the amphitheater on Wednesday afternoon. (Matt Gade/Republic)
Green algae flows along the western bank of Lake Mitchell just north of the amphitheater on Wednesday afternoon. (Matt Gade/Republic)

If guidelines proposed Tuesday were approved in 1991, the city would have discouraged people from direct contact of Lake Mitchell at least 66 times.

In an effort to protect swimmers and recreational users of Lake Mitchell, Parks and Recreation Director Nathan Powell proposed a set of guidelines for closing or discouraging use of the lake in the event of "harmful algal blooms." The proposal was approved by the Lake Mitchell Advisory Committee on Tuesday, and will next head to the Parks and Recreation Board to consider making a formal recommendation to the City Council.

Powell's plan would discourage contact with the lake or recommend all accesses to the lake be closed if a certain level of cyanotoxins and cyanobacteria are found. If between 10 micrograms per liter (ug/L) and 50 ug/L of chlorophyll is found in the lake - which Powell said is an indicator of toxins - a public health watch would be issued and direct contact with the affected portion of the lake would be discouraged.

Between 50 ug/L and 5,000 ug/L would spark a warning, and more than 5,000 ug/L would lead to a recommendation to close the lake.

According to tests between 1991 and 2016, Lake Mitchell topped 50 ug/L 66 times, reaching as high as 419.964 parts per billion in 2006. Parts per billion is approximately equivalent to ug/L.

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The plan would also address microcystin, which the U.S. Environmental Protection Agency says can cause abdominal pain, headaches or even liver and kidney damage.

If between 4 and 20 ug/L of microcystin is found, a public health watch would be issued, and between 20 ug/L to 2,000 ug/L would discourage recreational use of the entire lake. More than 2,000 ug/L of microcystin would recommend the closure of all lake access points.

Powell did, however, reiterate two of the notices would not bar access to the lake.

"It's discouraging, so we're not saying 'no,' " Powell said.

Also, if more than 235 colony-forming units per 100 milliliters of E.coli is found, a closure recommendation would be issued.

Committee member Mark Puetz suggested the idea has some merit, but speculated how the public might react to the proposal.

"There might even be some pushback with it, but I don't see it as bad when you're looking at the health risk generated by a source of something that people just haven't known about," Puetz said.

Another committee member, Brian Temple, was more hesitant about the plan.

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"We just don't have a lot of precedent out there, so I think we need to move a little slow, I think we need to be cautious," Temple said.

Lake restoration project makes progress

The city's $73,725 preliminary restoration study for Lake Mitchell is underway with the help of Omaha-based water quality firm Fyra Engineering, and two groups pegged to work between Fyra and Mitchell residents will first meet on March 7.

And, according to Fyra's report, the firm has created graphs, reviewed lake history and conducted analysis of the lake.

In its report, Fyra also backed the harmful algal bloom guidelines pitched by Powell.

The city is also planning to install cattails and artificial fish habitat in the lake in the spring. Committee President Joe Kippes said the group will likely need help from the public to install the habitats, know as fish cities.

"There's some process to it, and they don't come with instructions," Kippes said.

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