For three years the County has been testing the water in and around the lake. Those tests resulted in a decision in early 1999 to design and install a higher degree of water treatment to protect your water from volatile organic and synthetic compounds, that are suspected carcinogens, and that could possibly runoff from surrounding land uses into the water of the lake. In fall of 1999, we replaced the original filtration system at the water treatment plant at the lake and installed a granular activated carbon filtration system to remove taste and odor and any herbicides, pesticides and other organic and synthetic compounds that could runoff into the lake water supply and which could not previously be reliably and effectively removed by the original filtration system and operations. The manganese problem was not addressed during these treatment plant filtration modifications, as it was not thought to be a concern at that time. We have since learned that while the original filtration system was effective in removing manganese, it did so not by design, but rather as a result of the previous filtration media properties.
Water treatment is a complex and dynamic process.
Mother nature often has input. In the fall of the year, when we began the new activated carbon treatment process, lake water is cooler in temperature and relatively uniform in quality. That soon created layers of water in the lake with significant difference in temperature, amount of oxygen and water quality, all affecting the ability of the new filtration system to reduce higher manganese levels. The higher level of manganese then reacted with chlorine used to disinfect the treated water, discoloring it brown. In addition, as water production increased in the warmer months due to higher seasonal summer demand, the manganese deposited in the water mains was re-suspended and mixed with the drinking water, resulting in continuation of discolored water coming from pipes in several areas of the county.