Last night HAB completed the second dose of the Fish Lake alum project and we demobilized our equipment from the work site at the boat launch this morning. As planned and ahead of schedule, an exact dose of 95,000 gallons of alum was applied to the lake. Between our 2017 & 2019 projects, all of the total prescribed alum dose for Fish has now been applied and the improved water quality is expected continue!
This is the last of our postings for the 2019 application, but check back periodically (or receive automatic notifications by entering your email address below) for more project updates in the future. Thanks for your interest and following our progress. Don’t forget to follow HAB on Facebook, Twitter and Instagram too. Finally, a big thanks to the Fish Lake community and the Three Rivers Park District for all of their support and kind words about HAB’s performance. Much appreciated!
We previously discussed the importance phosphorus in determining lake water quality. Today’s article (see below) address the question “Where Does This Phosphorus Come From?”
At Fish Lake, phosphorus in the lakebed sediments has increased over the years and is released when oxygen levels decrease at the lake bottom. The water column periodically mixes during high summer winds and cool conditions, bringing phosphorus-rich water to the surface for algal uptake and growth. Samples from the bottom of the lake confirmed that phosphorus is very high in the sediments and available to be released into the overlying water column. The alum application produces a “floc” that settles to the bottom of the lake. The floc has sites where phosphorus in the sediments become chemically bound as it leaches from the bottom. The floc effectively intercepts and binds the phosphorus, which makes it unavailable for the algae to use for growth. The goals of the project are to reduce the internal loading of phosphorus from the sediments, lower the amount of phosphorus available to algae in the water, reduce the amount of algae and potential toxins and improve the recreational opportunities for lake users.