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Wet Excavation-Pond is too large, limiting access from the shore <br /> Light Blocking with Dyes-Use of dark dyes to prevent growth of algae but pond is too large <br /> and flushes too often <br /> Mechanical Removal-Pond is too large and algae is dispersed <br /> Selective Withdrawal-Removes poor quality water at the bottom but since the pond is often <br /> mixed, it would not be effective and would re-locate the problem downstream <br /> Algaecides-Potentially toxic to other organisms and a short term solution <br /> Sediment Oxidation-A newer technique making use of oxygenated agents and ph adjustors to <br /> oxidize the sediments; other locations have presented mixed results and suggested the possible <br /> release of nitrogen and unsure of longevity <br /> Nutrient Addition-Add nitrogen to diminish the blue-green algae, but not an option on Cape <br /> Cod <br /> Biologic Controls-Increase bass to decrease smaller fish, which increases zooplankton which <br /> eats more algae and could be used in conjunction with other techniques <br /> Mr. Kretchmer described the benefits of circulation and the action of mixing algal cells below the light <br /> in the dark zone where it would be difficult to survive. As the algal cells are continually mixed into <br /> the dark zone,they will begin to die off. The scum formation may be reduced by continual mixing and . <br /> the species may change. Circulation during the calm periods could also reduce the internal loading of <br /> phosphorus as oxygen is moved from the surface to the sediment and the water with low oxygen will <br /> be moved to the surface to pick up oxygen and rotate back to the bottom. A windy day would provide <br /> a similar benefit. However, many of the systems are large and located on the surface, creating limits to <br /> navigation and recreation. Allen Waxman of The Santuit Friends offered to provide AECOM with <br /> cost estimates for alternative techniques that had been researched by his organization. Copies are <br /> attached to these minutes. <br /> Alternative Techniques-To Be Considered: <br /> Circulation-Fountains which are typically used in small ponds; Air Flotation where air bubbles <br /> from the bottom create a vortex to mix the water; Solar Circulators where, in Santuit Pond, 5- <br /> 10, 9 foot tall units would be needed; COST $200,004400,000 <br /> Hydraulic Dred in -Sediment would be removed in a slurry with a pipe, left to de-water on <br /> land and the remaining solids would be removed by truck; a large land area would be needed to <br /> de-water; nutrients and algal cell seed bank would be removed directly; all soft sediment would <br /> need to be removed to the sand; the amount of sediment at the bottom of the is unknown; <br /> process is expensive compared to other options; COST $12-$16 million <br /> In-Lake Phosphorus Inactivation with Alum-Process would change the binder from iron to <br /> aluminum to prevent the release of phosphorus; process would affect the upper 2-4 inches of <br /> the sediment; the treatment would last for some time provided no additional sources of <br /> phosphorus were added; other issues include knowing incoming sources of phosphorus, system <br /> hydrology, water chemistry, sensitive species, where the alum could travel; in order to avoid <br /> 6 <br />