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Alum dosagu was calculated by two methodologies. n.e tot yields the maximum dose a <br />lake can receive and still maintain a pH above 6.0 (Cooke et al, 1986). A pH of 6.0 is <br />considered environmentaUy safe from an aluminum toxicity perspeedve and meets MPCA <br />water quality standards. <br />The second method esdmates the actual required dose based on phosphorus loading data and <br />the number of years the treatment is to be effective. Method one requi.es approxim y <br />280,000 gauons of alum (approximately 1,300 gallons/aae). Method two requues <br />approximately 50,000 gallons of alum (approximately 230 gaUons/acre for five y^s of <br />internal loading control). TTe alum dosages were calculated for Ali(SO,),. 4 H,0 and are <br />equivalent to approximately 610 pound of aluminum/acre and 100 pounds of aluminum/acre <br />respectively. <br />The design dose was selected by multiplying the dose calculated by method two by an <br />empirical factor ot 2.5 used in the industry. The above approach allows for uncertainues m <br />phosphonis loading but lull drasUcally reduces alum quandties from an environmental and <br />approximately 270 pounds of alummum/acre. <br />representing the actual alum requirements. If it is later determined that addiuonal ^um« <br />required to meet previously determined water quality goals for Ixmg lake, a second DNR <br />approval for aiutc Application can be considered. <br />; ' <br />i * <br />• r