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20 <br /> EXECUTIVE SUMMARY ' <br /> (3) Greatest Risk <br /> Highest risks to attaining water quality management objectives for the reservoir are presented by: <br /> • Increased algal blooms associated with nutrient loading from future development. Summer algal blooms <br /> are already frequent in Cane Creek Reservoir. Most blooms are dominated by blue-green algae, including <br /> species associated with taste/odor problems and potential production of algal toxins. Increased residential <br /> development could worsen the problem(Figure E-3). <br /> so 40% <br /> =L 60 30% a <br /> 4 <br /> 0 <br /> 2p <br /> 40 20% <br /> .o <br /> o <br /> 20 10'/e <br /> U <br /> a w <br /> 4 <br /> M.. 0% <br /> Undeveloped Current Conditions 25%Buildout Full Buildow <br /> .P Concentration a Algal Bloom Frequency <br /> Figure E-3. Projected Eutrophication Impacts under Current Protecdon Measures <br /> • High manganese cows caused by naturally occurring lake conditions, which result in undesirable <br /> aesthetic conditions in finished water. The intake raw water will contain problematic concentrations of <br /> manganese when OWASA must draw water from below the depth of the thermocline (a temperature <br /> barrier that separates surface from bottom waters in the summer) and occasionally at times when anoxic <br /> (devoid of oxygen)bottom water is mixed into the surface water. <br /> • Total organic carbon levels,expected to remain high in the raw water supply because decaying vegetation <br /> and in-lake production are not amenable to control, which react to form harmful by-products during <br /> disinfection steps in the water supply treatment and distribution system. <br /> • Law dissolved oxygen concentration, reduced water clarity, and microbial pathogens also pose a moderate <br /> risk to attaining water quality objectives(See Chapter 2). <br /> E-5 <br />