CITY OF EAU CLAIRE: LMI-Alum Treatment Half Moon Lake

Purpose

The City of Eau Claire is sponsoring a Lake Management Planning Implementation project aimed to control internal sediment phosphorus loading in Halfmoon Lake by applying alum. The lake received an initial AL treatment in 2011 and was effective at maintaining TP WQ goals for three years, however after five years the effects have diminished. The initial alum treatment dosage was adequate however the floc did not sink into the upper sediment due to higher bulk density characteristics allowing upward P diffusion and decreasing binding efficiency of phosphorus. The second treatment is needed to bind available TP limiting the amount available to algae uptake. The City continues to address other sources of TP including stormwater management, rain gardens etc. Project activities include: Apply a buffered AL dose to the western arm of Half Moon Lake that is encompassed by the 10 foot contour in late May or early June 2017. Dosage is based on sequestering the annual sediment P flux rate of 0.4g/m2 for 2 to 3 years and factors in an Al binding efficiency of 60% (James 2016 and 2017). Project deliverables: The outcome of AL treatment to the western arm will be control of internal P loading and reduction of cyanobaceterial biomanss and chlorophyll to target levels. Limnological monitoring will be conducted to verify outcomes. Special conditions: 1. The Half moon lake Team consisting of DNR, UW Stout, City of EC and Friends of Halfmoon Lake meet quarterly to assess current lake management actions. There continues to be open and ongoing communication with the group to inform residents on current lake conditions and management decisions. 2. All necessary permits must be issued prior to the project being implemented.

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Lakes Grant
Lake Protection Grant
LPT56417
2017
Active
 
Activities & Recommendations
Grant Awarded
The City of Eau Claire is sponsoring a Lake Management Planning Implementation project aimed to control internal sediment phosphorus loading in Halfmoon Lake by applying alum. The lake received an initial AL treatment in 2011 and was effective at maintaining TP WQ goals for three years, however after five years the effects have diminished. The initial alum treatment dosage was adequate however the floc did not sink into the upper sediment due to higher bulk density characteristics allowing upward P diffusion and decreasing binding efficiency of phosphorus. The second treatment is needed to bind available TP limiting the amount available to algae uptake. The City continues to address other sources of TP including stormwater management, rain gardens etc.
Lake Management Plan Implementation
The City of Eau Claire is sponsoring a Lake Management Planning Implementation project aimed to control internal sediment phosphorus loading in Halfmoon Lake by applying alum. The lake received an initial AL treatment in 2011 and was effective at maintaining TP WQ goals for three years, however after five years the effects have diminished. The initial alum treatment dosage was adequate however the floc did not sink into the upper sediment due to higher bulk density characteristics allowing upward P diffusion and decreasing binding efficiency of phosphorus.
 
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