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GRASS LAKE WATER MANAGEMENT ORGANIZATION -APRIL 23, 2009 6 <br />Minnesota. Sobiech responded that iron control can be used in shallower portions <br />of the lake where there are no anoxic conditions. Alum should be used in deeper <br />parts of the lake. <br />Several scenarios for Best Management Practices (BMPs) were presented. <br />Recommended combinations for treatment are: <br />• Curly leaf Pondweed management (Scenario 2) plus 10% reduction <br />in the watershed internal load (Scenario 3); <br />• Curly leaf Pondweed management (Scenario 2) plus 50% reduction <br />in the watershed internal load (Scenario 4); <br />• Curly leaf Pondweed management (Scenario 2) plus select <br />infiltration throughout the watershed (Scenario 8); and <br />• Curly leaf Pondweed management (Scenario 2) plus alum <br />treatment (Scenario 9). <br />Overall recommendations include: <br />1. Four-year curly leaf pondweed management plan at an estimated <br />cost of $649,000, or $162,000 per year; <br />2. Additional studies <br />3. Water quality monitoring in Central Park -east and west wetlands <br />and the Charlie Pond System -cost estimate $7,000 to $9,000; <br />4. Fisheries Impact Study -focus on carp movement in Lake Owasso, <br />Central Park, West wetland and Bennett Lake system through a <br />potential partnership with the University of Minnesota or the DNR; <br />5. Sediment Core Analysis in Central Park -east and west wetlands, <br />Charlie Pond System and Bennett Lake -estimated cost $7,900; <br />6. Water quality monitoring in Lake Owasso shallow site -estimated <br />cost of $1,800 to $2,800 <br />7. Implementation of infiltration BMPs throughout watershed as <br />opportunities occur and where site conditions allow; <br />8. Continue implementation of nonstructural BMPs, such as rain <br />gardens in parks, promotion of vegetated shoreline buffers to filter <br />direct runoff and discourage geese and waterfowl, street sweeping <br />and public education. <br />If problems continue after treatment of curly leaf pondweed, consider a full lake <br />treatment with alum to bind the phosphorous to the sediment. <br />Westerberg asked the long-term effect of alum treatment. Aichinger responded <br />that it varies depending on a number of factors. One complicating factor could be <br />