Committee told by N.D. group that circulators will work in lake Another lake proposal
By SETH TUPPER The Daily Republic
A North Dakota company has proposed placing 10 circulators in Lake Mitchell for two summers at a cost of $246,561 to demonstrate how the technology could rid the lake of blue-green algae. After the trial period, or any time during it, the city could buy the circulators with 60 percent of the rental payments applied to a purchase price of $425,537. Representatives of the eightyear-old Solar Bee division of Pump Systems Inc. made the pitch Thursday at City Hall to Mitchell’s Lake Development Committee, an appointed group that advises the City Council. Solar Bee’s Joel Bleth and Michael Christensen said they have installed their solar-powered circulators in 180 bodies of water with a 95 percent success rate. Bleth said circulators can produce a permanent improvement in water quality within two weeks. “We would expect you to have an 80 percent chance that you would have one major bloom sometime within a year to two years after they were installed,” Bleth said, “but then that would be it.” The Solar Bee presentation was the latest in a string of proposed algae fixes heard by the Lake Development Committee. The committee already has rejected another circulator
proposal, as well as a proposal to treat the lake with calcium. For each of the past four summers, the city has applied aluminum sulfate, or “alum,” to the lake on the advice of a paid consultant from Minnesota. The results have been debatable, and the city has dumped nearly $300,000 into the applications. Another $130,000 application is tentatively planned next summer. Bleth said alum treatments are futile and have only been shown to work in two of the 130 lakes they’ve been tried in worldwide. “Alum is worthless,” Bleth said. “I’m sorry to break that to you, but that’s shown by two separate independent studies.” Alum is supposed to work by trapping phosphorus, an algae food source, in sediments. The treatments in Lake Mitchell were meant as a short-term attack on the existing phosphorus in the lake. Meanwhile, a long-term attack has been under way since 1998 to reduce the amount of phosphorus that enters the lake via its tributary, Firesteel Creek, and the 350,960-acre Firesteel Creek watershed. Both the Lake Development Committee and the City Council have reached a general consensus in recent times that phosphorus is the enemy, and most of the phosphorus enters the lake via the creek. Bleth contradicted that theory. Reducing phosphorus inputs is good for the watershed, Bleth said, but it is not a proven way to reduce blue-green algae in lakes. “What we do is we say, ‘We don’t care about how much phosphorus you have,’ ” Bleth said. “It’s not the amount that you have, it’s what happens to it.” Bleth said the algae that bloom in the lake are an “inedible” type that thrives on warm, stagnant water. Circulation, he said, disrupts the bad algae and promotes small edible algae that are consumed by organisms in the lake’s food chain. “That’s what we’re doing is changing what happens to the nutrients,” Bleth said. “Give us all the phosphorus you want. We don’t care.” The proposal calls for 10 circulators to be anchored at crucial areas in the lake. The tops of the circulators would protrude from the water, and a long tube would extend down into the water. Water from the bottom of a lake is drawn up through each circulator in the same manner as a straw and pumped horizontally across the surface with power supplied by solar panels. The circulators are said to move 10,000 gallons of water per minute. Each circulator is 16 feet in diameter, weighs 700 pounds and extends to varying depths, depending on the situation. They are said to run quietly, require little maintenance, are lit at night, can be left in place through the winter and have an expected life of 25 years. They can be operated remotely with software that the city is already buying for the water plant. Solar Bee says it has more than 1,000 circulators currently installed nationwide. To the company’s knowledge, Christensen said, only one circulator has been struck by a boat. The company says the circulators are safe for swimmers, because the force of the current coming out of the machines makes it difficult for most swimmers to get too close. The proposed $246,561 rental price for 10 circulators would cover an 18-month period — long enough for two summers. The company also has some used circulators that could be rented or purchased at a lower cost, depending upon availability. Solar Bee’s invitation to Mitchell came after Mayor Lou Sebert, former owner of Dakota Pump Inc., visited the company’s booth at a trade show earlier this year in Dallas. After the presentation Thursday, Sebert said the proposal deserves serious consideration. “For the cost and the maintenance and the upkeep, this is certainly cheaper than any other method we’ve seen,” Sebert said. The Lake Development Committee expects to meet sometime this month to discuss the proposal further before possibly making a recommendation to the City Council.
Photo courtesy of Solar Bee PICTURED HERE IS a Solar Bee circulator on Lake Wildwood in California. Similar circulators would be placed on Lake Mitchell under a proposal presented Thursday to the city’s Lake Development Committee.
Laura Wehde/Republic Joel Bleth, of the Solar Bee division of North Dakota-based Pump Systems Inc., presents a proposal Thursday at Mitchell City Hall to install 10 circulators in Lake Mitchell to battle blue-green algae blooms.
