5.8.13 Other Projects

This Plan identified the need to consider additional projects not included in the prioritized 2007-2017 CIP. These include regional infiltration opportunities in subwatershed units CLC-3 and SB-2 (see Section 5.8.11 above), an alum injection system to treat flow out of Six Mile Marsh prior to discharge into Halsteds Bay, and vegetation management in Stubbs Bay. The Board may consider such projects during the time frame of this Plan if funds are available.

ProjectHalsteds Bay Tributary Alum Injection System
DescriptionDesign and implementation of strategies to reduce phosphorus loading from Six Mile Creek, 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 including alum injection.
Need

Six Mile Creek conveys a significant phosphorus and sediment to Halsteds Bay. Most of this load is contributed by Mud Lake and Six Mile Marsh, through which the stream flows, and is exacerbated by the poor water quality being discharged from Parley Lake. Initial modeling suggests that improving Parley Lake to meet its water quality goal will not significantly reduce the load conveyed to Halsteds Bay. Constructing a bypass around Six Mile Marsh may be financially infeasible.

An alum injection system may be considered to treat the discharge from Six Mile Creek at its discharge point into Halsteds Bay. A diagnostic / feasibility study should be conducted to better understand the potential causes for nutrient and sediment contribution from Mud Lake and Six Mile Marsh, and to further investigate the feasibility of the proposed system. Other strategies to be considered are biomanipulation in mud Lake and Six Mile Marsh, control of rough fish, and wetland vegetation management. The cost shown here is the estimated cost of construction of an alum injection system and a floc settling pond.

OutcomeReduction in phosphorus load contributed to Halsteds Bay; improved water clarity in Halsteds Bay; improved aesthetics
Cost Estimated and Funding
Application of vegetation management
techniques in Stubbs Bay. Funding source
is the District capital levy.

$288,500 Feasibliity, design

$2,958,800 Construction

$3,247,800 Total

ScheduleNo year has been assigned to this project. Operating costs of an alum injection system are estimated to be $635,900 annually.
ProjectStubbs Bay Aquatic Vegetation Management
DescriptionDesign and implementation of strategies to manage aquatic vegetation that contributes to internal phosphorus loading or degradation of water quality or biotic integrity
Need
As water quality in Stubbs Bay improves, the aquatic vegetation communities may change. Improved water clarity may result in accelerated growth of aquatic vegetation that may increase internal phosphorus loading, negatively impact fish or aquatic invertebrate habitat, or increase susceptibility to invasive aquatic species. Management of aquatic vegetation that contributes to lake water quality and biotic integrity issues may require annual treatment for three to five years.
Outcome
Improved water clarity; more diverse aquatic vegetation and biotic communities; improved aesthetics
Estimated Cost and Funding
Application of vegetation management techniques in Stubbs Bay. Funding source is the District capital levy.$34,200
ScheduleNo year has been assigned to this project, which would be implemented on an as-needed basis. Vegetation management is most effective if applied annually for at least three years in a row.