Lake Holiday just turned 50 last year. You could say our lake has reached “middle age”, complete with a few aches and pains but overall doing quite well and ready to provide a wealth of recreational and ecological benefits for many more years to come. We got a bit of a scare back in the Fall of 2016 when a lake-wide harmful “blue-green” algae bloom temporarily closed the lake to all direct contact by humans and pets. Since then, LHCC’s consultants have performed several scientific and engineering studies, including collecting 7 years’ worth of lake data, to determine what key processes control lake health and what steps can be taken to protect our lake’s future health. The following is a summary of where things stand.
Q: What caused the 2016 blue-green algae bloom? A: Lake-wide phosphorus levels measured at this time were the highest ever recorded. This coincided with higher-than-average rainfall and higher-than-average water temperatures.
Q: Have there been any blue-green algae blooms in Lake Holiday since 2016? A: No, thankfully there has not been a blue-green algae bloom since 2016. Phosphorus has remained lower during all years since 2016, and annual rainfall and water temperatures have generally been lower as well. The key “triggers” for a harmful algae bloom have not repeated, however in the “wet” year of 2018 phosphorus levels rose “just shy” of 2016 levels.
Q: Where does the phosphorus come from and how much of it is in the lake? A: Phosphorus occurs naturally in soil, and can be at higher concentrations in soil eroding from agricultural areas. The large (8,000+ acre) watershed surrounding Lake Holiday was historically an agricultural area growing corn, hay, and cattle. Over the last 50 years at least 30 tons of phosphorus has accumulated in Lake Holiday, carried in by soil as it erodes from the land.
Q: How do we know there is “at least 30 tons of phosphorus” sitting at the bottom of the lake? A: Our consultants measured the phosphorus levels by collecting multiple sediment “cores”.
Q: What can be done to reduce the chance of a repeat of the 2016 blue-green algae bloom? A: We are working on a 4-part action plan to protect the lake’s future health – see status below.
Part 1 – Manage return of Submerged Aquatic Vegetation and create Emergent Wetlands. Status – Our consultant GKY is currently developing a plan to plant emergent wetlands (e.g., bull rush, cattails, etc.) along the banks and in the shallow areas of Isaacs Cove to act as a filter to capture sediment and phosphorus entering from Isaacs Creek. These types of plants would not be consumed by the existing grass carp. Future planting of other types of submerged aquatic vegetation will need to wait until the grass carp population is greatly reduced (another 5-10 years approximately).
Part 2 – Control local community-scale sources of sediment and phosphorus. Status – In Spring 2022 community volunteers conducted a visual survey of streambank erosion conditions throughout the Lake Holiday Community. Stream areas were ranked by existing erosion levels. We are now in the process of screening engineering consultants for bidding on select stream areas for restoration and erosion control. We expect the selection process to occur in Fall of 2023.
Part 3 – Implement a sediment removal action for Isaacs and Yeiders Coves. Status – A large percentage of the accumulated sediment and phosphorus within the lake lies within Isaacs and Yeiders Coves (30%+). The objective is to remove a large portion of this concentrated volume of phosphorus-rich sediment to reduce the “in-lake” source of phosphorus and reduce the likelihood of a triggering event for a future blue-green algae bloom. Our consultant GKY is currently developing the engineering plan which would include removal of cove sediment through dredging and storing that sediment in a “dewatering” or holding basin located at the top of the hill near the old “ski” area. The cove sediment has been tested and has been found to be clean of any organic chemicals, metals, or toxic contaminants. The dewatered sediment could be used by residents in the future for garden soil. The sediment removal plan requires permits from the US Army Corps of Engineers, State, and County agencies. We expect the plan, including permit approvals, to be completed by the Fall of 2023.
Part 4 – Create a HAB “Harmful Algae Bloom” Emergency Action Plan. Status – Our consultant Princeton Hydro is currently preparing this plan, and it should be ready for implementation later in 2023 or at the latest Spring 2024. This plan will provide specific steps, including clear guidelines and line of command in the event of a future HAB (who does what, when, where, and how ??). Hopefully this plan will never be needed but a prudent approach is to be well prepared.
Questions? We encourage all residents to become educated in key lake ecological processes and the steps all of us can take to help protect our beautiful lake. If you have any questions, please send them by email to: communityinput@lakeholidaycc.org.
Jim Pagenkopf, Natural Resources Subcommittee
