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Floating Treatment Islands on Lake Anna

September 01, 2022 12:00 AM | Anonymous member (Administrator)

By Mike Gelber - September 2022

LACA started the study of Floating Treatment Islands (FTI) in 2021. Since Lake Anna was created as an impoundment naturally created wetlands were never established. To create a wetland buffer would cost millions of dollars and the removal of many acres of farmland. The creation of these Floating Treatment Islands was interesting because a 250 square foot island was found to be equivalent to an acre of natural wetland at a fraction of the cost. The initial trial was with homemade islands that were filled with marsh plants native to Virginia. 

There were some “growing” pains with the selection of some of the plants. We did not know how deep the islands would ride in the water and some of the plants did better than others in the deeper water. During the winter of 2021-2022 the tops of many of the plants died back which was expected.  By the Spring of 2022 new growth was seen in last year’s Islands. LACA and the Runnymede POA purchased commercially manufactured FTI and they were planted and deployed in the Spring of 2022. As seen in the photograph above; the plants are doing well and by mid-Summer the roots were starting to hang below the Islands.

Because the plants are growing with no root contact to the lake bottom, all the nutrients they are using come directly from the water. When the Island plants absorb the nitrogen and phosphorus from the water there are less nutrients available for the algae to use.  Notice in the photo below the visitor in the upper left corner.

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