Lake Rebecca

In 2009, Three Rivers Park District was awarded a Lessard-Sams Outdoor Heritage Fund (LSOHF) grant in the amount of $450,000 to implement the water quality improvement projects for Lake Rebecca, including a shoreline restoration project, a multi-year curly leaf pondweed control project, and an alum (aluminum sulfate) treatment for the lake.  Previously, a project had been completed to signficantly reduce watershed nutrient inputs from horse farm , the only known source of signficant "external" loading in the drainage area of the lake.  The total cost of the LSOFH project was estimated at $480,000 with the Park District providing an in-kind service match valued at $30,000.  


The most critical component of the LSOHF project was the application of alum to the lake to reduce internal cycling of phosphorus from lake bottom sediments.  Contractors were hired to to make two applications of alum to the lake, one in the fall of 2010 and the other in the spring of 2011.  In each case the alum was applied at a dose of approximately 740 gallons per acre over about 220 acres of the 258 acre lake (total dosage rate of about 1,480 gallons/ac).  The dosage was split in order to prevent unacceptable affects of the ph in the lake and minimze the potential for negative impacts to the biological community, including the fish community.  Three Rivers Park District is intending to achieve a decrease in the mean summertime (June-September) phosphorus concentration in the lake from pre-project levels in excess of 100 ppb to levels of 40 ppb or less.  The latter should correspond to water clarity values of at least 1.4 meters for the summertime period.  The District also anticipates that the effects of the alum treatment should last at least 10-15 years.


Interested in seeing the some scenes from the alum treatment? Click the links for a photo of a reload dock and application barge!