Excessive nutrients, called “phosphorous loads”, increase the amount of blue-green algae which imparts taste and odor compounds. To inhibit the growth of excessive algae several controls were implemented:
- Installation of ferric chloride feed systems
- Installation of aerators
- Restoring water levels to near-natural conditions in certain wetlands
The control measures targeting the Mississippi source water and the lake sediment loads have successfully reduced the phosphorus concentration from approximately 60 to 80 micrograms per liter to 20 to 40 micrograms—very near the goal of 25 micrograms.
For example, restoration work on the Lambert Creek watershed area was selected by the Governor's Clean Water Initiative in 2004 as one of two metro area clean water projects. The addition of a weir, pond, and ditch in the watershed will help us reduce the phosphorus levels of water coming into Vadnais Lake.