Kitsap Lake Algae Control and Aquatic Vegetation Management

Project Status

Algae control and aquatic vegetation management were budgeted and approved in the City’s 2022 annual budget process. AquaTechnex LLC. completed the first whole lake Phoslock treatment in May and the second deep water treatment in July of 2022. This took a total of 5 days to complete while the lake remained open for use. The lake is safe to use for direct contact within 2 hours of application and we are monitoring water quality every two weeks until October to track free reactive phosphorus levels and algae speciation as well as dissolved oxygen and temperature.

Project Overview

Kitsap Lake water quality and aquatic vegetation have been studied for the past two decades. The lake is fed by streams, springs, and stormwater runoff which carries nutrients into the lake. The lake has a very limited exchange of water, so pollutants tend to “hangout” in the lake and settle to the bottom. Nutrients, in the accumulated sediment, support aggressive aquatic vegetation growth and feeds potentially toxic cyanobacteria (blue-green algae) blooms. Further, the lake attracts waterfowl whose waste contains bacteria including E-coli that impairs water quality. Historically, elevated bacteria levels and cyanobacteria algae blooms prompted lake contact recreation advisories and closures each year.

The AquaTechnex LLC. scope of work for 2022 include:

$80,000 - Phoslock application to entire lake with a second deep water application
$40,000 - Harvesting of excess aquatic vegetation
$2,500 - Reapply herbicide to invasive shoreline vegetation and aquatic species
$750 - Reapply for NPDES Permit
$2,000 – Water quality sampling (used for sediment sampling)
$35,000 Second Phoslock application in deep water portions of the lake
Tax: $14,422.50
Total contract - $175,000

Mayor Wheeler and City Council identified Kitsap Lake as a priority concern and dedicated resources to improve lake quality and restore recreational opportunities to the community. In late 2018, the City met with lakefront property owners to discuss lake water quality and developed a partnership committed to lake cleanup. Baseline water quality and lake sediment testing were completed in 2019, which defined corrective actions needed. City staff completes seasonal water testing to track improvements or issues associated treatment. Kitsap Public Health tests lake water to ensure it is safe for direct contact during recreational use and fishing.

Water quality has improved significantly with no closures reported during the high use months of June through August over the past three years. This is the third year of the project using Phoslock® (an environmentally safe product) to control cyanobacteria (blue-green algae) growth in the lake which can release toxins that can affect humans, wildlife, and pets. Algae blooms have occurred outside of the high use periods. By comparison with pre-project blooms, these have been smaller and shorter in duration and often not of the blue-green species. Continued project support will be needed over the coming years to maintain water quality and control free reactive phosphorus in the lake.

Needs/Benefits

Blue-green algae blooms need to be reduced or eliminated to protect public health, wildlife, and pets. Controlling free reactive phosphorus levels in the water column has reduced and will continue to reduce food that the blue-green species need to grow. This effort provides clean and safe water that is used by various fish stocks, wildlife, as well as our general population for recreation.

Timeline/Schedule

Initial treatment of the lake will be completed in May, with a second Phoslock application in July if needed. Submerged aquatic vegetation harvesting will be completed in August to help reduce the amount of phosphorus released during plant decomposition over the fall and winter months. Submerged aquatic vegetation is a risk to swimmers as it tends to wrap around arms and legs as the swimmer moves through it which can be life threatening. Harvesting reduces boat prop fouling and opens areas of the lake for use. City staff is conducting bi-weekly water quality and clarity monitoring of the lake from April to October to track the benefits of the Phoslock application and harvesting efforts.

Funding

Is provide by an allocation of funds from the City of Bremerton General Fund and Stormwater Utility.

End Result

The goal of the project is to improve water quality of the lake and provide a safe environment for all lake users including people, fish, wildlife, and pets. Improved water quality has a significant positive impact on downstream users including shellfish at the Chico Creek outlet in Dyes Inlet. By using safe products and processes to remove phosphorus, and excess submerged vegetation we are protecting the lake and habitat without damaging sensitive fish stocks, or vegetation species.