Lake Demontreville and Olson Association – Manage Invasive species, preserve, protect, and improve water quality and shoreline health Lake Demontreville and Olson Assn preserve protect and improve water and shoreline health Clean Drain Dry Instruction video MN DNR Boat and Water Safety Protect our Lakes The Lake Demontreville and Olson association LDO was founded in 1985 with a primary focus of maintaining water levels. In 1987 the Valley Branch Watershed District completed 1007 project managing water levels across the TriLakes area and Washington County. The LDO is now a IRS approved 501c3 organization focused on managing the Invasive Species in the Lakes and monitoring the water quality. Our Sponsors and Supporters City of Lake Elmo Minnesota Aquatic Invasive Species Research Center Valley Branch Watershed District Washington County MN DNR PLM Lake and Land Management Corp .