Kitsap Lake Algae Control and Aquatic Vegetation Management

Annual scope of work for AquaTechnex LLC. from May 2023 thru December 2025 includes: Mobilization / demobilization EutroSorb G application, 10% Lanthanum application to entire lake in May/June (a Phoslock replacement that is approved and readily available) Equipment, boats, barge Labor Reapplication for NPDES Permit Harvesting of excess aquatic vegetation Not to Exceed - $175,000 annually Total Contract - $525,000 over three years Kitsap Lake Cleanup Background 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. Lake water has a very limited exchange rate, so pollutants tend to “hangout” in the lake and settle to the bottom. Accumulated lake sediment has high levels of nutrients that support aggressive aquatic vegetation growth and feed potentially toxic cyanobacteria algae blooms. Further, the lake attracts waterfowl whose waste contains bacteria including E-coli that further impair water quality. Historically, elevated bacteria levels and cyanobacteria algae blooms prompted closures or advisories to be posted at the lake’s public access areas, restricting contact recreation. 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 issues 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 complete seasonal water testing to track improvements and/or issues associated treatment. Kitsap Public Health tests lake water to ensure it is safe for direct contact in support of recreational use and fishing. Over the past 3 years we have seen significant water quality improvement with no closures reported during the high use months of June through August. This is the fourth year of the project and we are switching treatment media to EutroSorb G, a 10 % Lanthanum based product that is more concentrated than Phoslock®, to control cyanobacteria growth in the lake. Algae blooms have occurred outside of the high use periods. A long-lasting algae bloom occurred in the fall of 2022 as a result of switching the order of Phoslock application and harvesting. This was a good learning experience and we’ve established a schedule to prevent this from occurring in the future. The pictures below show a before treatment and after the second year of treatment. Kitsap Lake Before and After A case study was completed and presented by SePro and AquaTechnex at various lake association meetings throughout the country highlighting the success of our project. City staff collects lake data every two weeks from April through October and uses SePro Laboratory services to analyze samples for free reactive phosphorus and algae speciation and counts. Data show greater than a 90% reduction of available phosphorus and increased water clarity by 3 times baseline equal to 20 feet of depth. Of course there is some variability in samples collected but the trend shows the lake is improving. Video Archive Inside Bremerton - Kitsap Lake Recovery: https://vimeo.com/745821631 Lake & Pond Heroes: Kitsap Lake, Kitsap County, WA: https://vimeo.com/748163014/309e2cad13 Supporting activities Stormwater treatment retrofits have been designed at 4 locations (3 in Dockside, and 1 at Kitsap Way and Northlake Way intersection) that discharge to the lake and construction funding is expected to be received in the fall of 2023 with construction in 2024. A 30% design for a treatment system at Francis Drive is almost complete and funding will be applied for in the fall of 2023 to complete the final design. These systems will further reduce phosphorus in the lake and help the city meet the Ecology issued TMDL for phosphorus at the lake. 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.

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