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5.8.2 Stubbs Bay Internal Load Management

ProjectStubbs 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, hypolimnetic withdrawal, and chemical treatment.

The ?unknown load? to lakes or bays is usually attributed to the bottom sediments, though it could be a combination of bottom sediments, aquatic vegetation, and model inaccuracy. A diagnostic and feasibility study that includes a more intensive evaluation of Classen Creek improvement options than was conducted in the Upper Watershed Steam Assessment would be required to determine the appropriate means of addressing internal loads in Stubbs Bay as well as potential reductions that could be achieved through restorations on Classen Creek. A variety of strategies may be employed to achieve the most cost effective reduction in phosphorus loading, including vegetation management, biomanipulation, and chemical treatment.

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 from internal sources estimated at 307 pounds annually; improved water clarity; more diverse aquatic vegetation community; improved aesthetics
Estimated Cost
Investigation, permitting, fish, vegetation, and
zooplankton surveys, design, implementation.
Funding source is the District capital levy.

$15,300 Feasibility

$504,600 Construction

$519,900 Total


2007 Fish, vegetation, and zooplankton surveys, development of management plans

2007 Implementation of strategies