5.8.1 Halsteds Bay Internal Load Management

ProjectHalsteds Bay Internal Load Management
DescriptionDesign and implementation of strategies to reduce internal phosphorus loading, including: feasibility study; aquatic vegetation survey update and management plan; fishery survey update and management plan; biomanipulation strategies that may include aquatic vegetation management, zooplankton community and fishery manipulation, and chemical treatment.

The modeled watershed phosphorus wash-off load to Halsteds Bay is not sufficient to explain the in-lake concentration of total phosphorus that exceeds the bay’s total phosphorus goals. An “unknown load” is attributed to internal loading, and is likely a combination of bottom sediments, aquatic vegetation, and model accuracy. A watershed and internal diagnostic / feasibility study will be required to confirm the internal and external phosphorous loading to the lakes, as well as the necessary load reductions. In particular, the “unknown load” must be identified as either an external or internal load before specific strategies can be selected. A variety of strategies would be investigated in the diagnostic and treatment study proposed in this plan.

This project would identify and implement a suite of strategies to manage aquatic vegetation, the fishery, and zooplankton community to achieve water quality and clarity goals. The project includes an ongoing vegetation and fishery management plan. Management of invasive aquatic vegetation that contributes to lake water quality and usability issues would require annual treatment for three to five years.

OutcomeReduction in phosphorus load from internal sources; improved water clarity; more diverse aquatic vegetation community; improved aesthetics.
Estimated Cost and Funding
Investigation, permitting, fish, vegetation, and
zooplankton surveys, design, implementation.
Funding source is the District capital levy.

$17,900 Feasibility

$520,500 Construction

$538,400 Total


2014 Fish, vegetation, and zooplankton surveys, development of management plans

2015 Implementation of strategies