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Leon County
Board of County Commissioners Agenda Item#13 April 9, 2024 |
| To: | Honorable Chairman and Members of the Board |
| From: | Vincent S. Long, County Administrator |
| Title: | Lake Munson Action Plan Status Update |
| Review and Approval: | Vincent S. Long, County Administrator |
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Department/Division Review and Approval: |
Ken Morris, Assistant County Administrator Ben Pingree, Assistant County Administrator Brent Pell, Director, Public Works Charles Wu, Director, Engineering Services |
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Lead Staff/ Project Team: |
Anna Padilla, Stormwater Management Coordinator |
Statement of Issue:
This item provides a status update on the implementation and ongoing efforts related to the Lake Munson Action Plan, as approved by the Board at the October 11, 2022 meeting and modified at the March 21, 2023 meeting, including an update on next steps following the anticipated conclusion of the drawdown in May. As directed by the Board, these Action Plan updates shall occur every six months during the ongoing drawdown of Lake Munson and two years following the refilling of the lake.
Fiscal Impact:
This item has no fiscal impact.
Staff Recommendation:
Option #1: Accept the status report on the Lake Munson Action Plan.
Report and Discussion
Background:
This item provides a status update on the implementation and ongoing efforts related to the Lake Munson Action Plan (Action Plan) (Attachment #1), as approved by the Board at the October 11, 2022 meeting and modified at the March 21, 2023 meeting. The item details the progress of the drawdown, implementation of the emergency action plan, the benefit of a full lake, and an analysis of the improving water quality and stabilizing system, the implementation of the invasive exotic vegetation management program, and a summary of the next steps following the anticipated refill of the lake in May. As directed by the Board, these Action Plan updates shall occur every six months during the ongoing drawdown of Lake Munson and two years following the refilling of the lake.
This status report advances the following FY2022-FY2026 Strategic Initiatives:
This particular Strategic Initiative aligns with the Board’s Environment Strategic Priorities:
Lake Munson, located on the south side of Tallahassee, receives much of its flow from densely developed areas. Decades of development prior to environmental regulations, wastewater treatment facility effluent discharges into the system, and activities focused on flood reduction resulted in severe water quality and ecological problems.
Since the 1980s, $290 million has been invested by local governments in ongoing efforts to restore Lake Munson and improve the water quality. More than 28 projects and 21 best management practices (Attachment #2) have been completed including infrastructure and restoration projects that provide water quality treatment, reduce sediment transport, and collect trash. Leon County’s Lake Munson Restoration Project was a major effort with the primary goal of improving the water quality in Lake Munson. The project included the construction of the Lake Henrietta stormwater facility, improvements to Munson Slough with the creation of living shorelines and reduction of erosion, removal of trash and the sediment delta from Lake Munson, and restoration of the wetlands around Lake Henrietta and Lake Munson.
The water quality and ecological health in Lake Munson have continued to noticeably improve with the $290 million of investments in capital projects and restoration activities resulting in a steady decline of nutrient concentrations. The water quality in Munson Slough (upstream of the lake) has improved such that the nutrient concentrations are below the target levels established by the State. Within Lake Munson, the nitrogen concentrations have been consistently below the State’s target and the phosphorus concentrations have steadily declined to approach the State’s target. Last year, nutrient concentrations in Lake Munson rose due to the explosion of invasive exotic vegetation and instability in the system.
Water quality improvements are not always immediately noticeable or profound and sometimes waterbodies experience setbacks as the system stabilizes with the improving conditions. Despite the measurably better water quality and investments in upstream infrastructure, Lake Munson experienced a minor setback in the summer of 2022 with an algal bloom, rapid growth of invasive exotic aquatic vegetation, and a fish kill. The extremely warm weather, shallow water, and stagnant nature of the lake create favorable conditions for algal blooms, invasive vegetation, and fish kills. These challenges presented an opportunity for immediate mitigation and evaluation of long-term strategies for managing Lake Munson. From this, the Lake Munson Action Plan was developed based on industry best practices for lake management with input from State agency partners, professional consultants under contract with the County for environmental and engineering support, and citizen stakeholders.
The Lake Munson Action Plan, approved by the Board on October 11, 2022, includes short- and long-term strategies to continue restoration and ecological improvement of Lake Munson and articulates the decades of investments, improving the water quality and ecological health of Lake Munson through upstream infrastructure projects. The Action Plan takes a holistic approach through a drawdown coupled with enhanced monitoring of the lake’s response, while also providing long-term strategies to supplement the State’s in-lake vegetation management activities and deliver a higher level of service to County residents (Attachment #1). Updates to the Board on the progress of the drawdown every six-months highlight the Action Plan implementation and provides new data and information.
The drawdown, which has been ongoing since November 2022, allows the nutrient-rich sediments in the lake to de-water, compact, oxidize, and form a hardened crust over the lake bottom. This hardened crust serves to “cap” the underlying sediment which provides a habitat for fish spawning and reduces nutrient recycling into the water once the lake is re-flooded. At the March 21, 2023 meeting, the Board approved modifications to the Action Plan, which included extending the drawdown through the Spring of 2024. The extended drawdown was a result of higher than anticipated winter 2021-2022 rainfall and in coordination with the Florida Fish and Wildlife Commission (FWC).
Enhanced monitoring provides information on the progress of the drawdown and on the lake’s response in the two years following the drawdown. In conjunction with the drawdown extension, the Board approved a Drawdown Water Quality Study including monthly water chemistry samples of the water flowing into and out of Lake Munson, which provides valuable information on the stability of the system as the drawdown progresses. Quarterly aerial topographic surveys throughout the drawdown are providing information on how much the sediments are compacting and will give an indication on the effectiveness of the drawdown. Following the refill of the lake, monthly water chemistry samples and flow data of the water entering and leaving Lake Munson will be useful tracking the lake’s response with the shock to the system but also provides information on the effectiveness of the drawdown.
The Lake Munson Action Plan includes long-term strategies centered around proactive management of the lake vegetation and sediment. An invasive exotic vegetation management program will supplement the State’s program and will provide more frequent treatments over smaller areas, impacting the system less. These treatments will be complemented by an algal bloom management program to mitigate the naturally occurring blooms on Lake Munson. Looking to the future, routine periodic drawdowns every 5-10 years will be utilized for sediment management, continuing to improve the water quality in Lake Munson. The Action Plan also includes exploration of new technologies and scientific data for new opportunities and strategies that could benefit Lake Munson. As these opportunities arise, they will be presented to the Leon County Science Advisory Committee (SAC) and State-agency partners, with viable solutions brought to the Board.
And finally, engagement with various entities is key in the Action Plan. Coordination with State-agency partners remains ongoing, evaluating the progress of the drawdown. Quarterly updates on the progress of the drawdown and the data collected through the enhanced monitoring are presented to the SAC for review and evaluation. Status updates to the Board every six months will continue through the enhanced monitoring period, providing updates on the progress of the Action Plan and a summary of the data collected and results.
Key Findings of the Past Six Months
As detailed in this item, since the previous update to the Board in September 2023, the drawdown resumed following Hurricane Idalia and continued until a second temporary suspension in December 2023 due to heavy rain. The benefit of a full lake during this period was the germination of Hyacinth seeds that were then killed off during a cold spell and the draining of the lake. These seeds are no longer available to germinate when the lake refills.
The enhanced monitoring continued through the previous six months. Water quality sample results indicate the lake bottom sediments continue to consolidate and the system is further stabilizing. Overall, the nutrient concentrations leaving the lake are trending lower while the nutrient concentrations entering the lake generally remain the same. Only one aerial topographic survey was collected during the previous six-month period, but results continue to indicate sediment compaction.
The invasive exotic vegetation management plan has been implemented. An initial treatment was applied in mid-March in Lake Henrietta, Munson Slough, and the flow through channel in Lake Munson. Additional treatments will be applied in April, prior to refill of the lake. Treating this vegetation prior to refill of the lake slows down or prevents the spread of the invasive exotic vegetation when the lake is refilled and gives the native species a head start in growth.
Looking ahead to the next six months, a final aerial survey will be collected, the drawdown will conclude and refill of the lake will begin in May, and invasive exotic vegetation and algal blooms will be treated.
As detailed in the analysis section, this item provides a status update on the implementation and ongoing efforts related to the Lake Munson Action Plan. In addition, this item provides an update on activities and progress since the update in September 2023. More information on the implementation of the Action Plan since adoption can be found on the dedicated Lake Munson website at www.LeonCountyWater.org/LakeMunson.
Analysis:
This six-month status update provides updates on the drawdown and implementation of the Lake Munson Action Plan since the previous update to the Board and outlines next steps following this update. Since the previous six-month update in September, the drawdown resumed following the temporary suspension during Hurricane Idalia and continued until December 2023 when the Emergency Action Plan for the lake was implemented a second time after frequent rainfall in late November. In the last six months, the monthly water quality data collection and aerial topographic survey continued and an analysis is provided in the following sections. In addition, the invasive exotic vegetation management program has begun and engagement with the SAC has been ongoing. This update also includes details regarding next steps for the Lake Munson Action Plan, including the final aerial topographic lake bottom survey, conclusion of the drawdown and refill of the lake anticipated to begin in May, water quality monitoring of the lake following refill, and continuation of the invasive exotic vegetation and algal bloom management programs.
The Lake Munson Action Plan employs a holistic approach to lake management with short-term strategies to mitigate algal blooms and aquatic vegetation growth, comprehensive enhanced monitoring of the water quality and sediment, and long-term strategies to continue water quality and ecological improvements into the future. Leon County staff and State-agency partners are continuously monitoring Lake Munson and evaluating the progress of the drawdown against ecological targets.
Lake Munson Drawdown
At the March 21, 2023 meeting, the Board approved an extension of the Lake Munson Drawdown through Spring of 2024. The drawdown is expected to conclude in early May, pending collection of the final aerial survey. The extended drawdown was intended to allow the sediment additional time to dry out, oxidize and form a “cap” which will reduce the nutrient recycling between the sediment and the water once the lake is refilled. In early September 2023, the drawdown was temporarily suspended in an abundance of caution due to Hurricane Idalia. However, the drawdown resumed on September 6, 2023 and continued in coordination with FWC. As addressed in more detail in the following section, in December 2023, the Emergency Action Plan for the dam was implemented a second time, which kept the lake full of water into January 2024. With a full lake in December and January, sediment drying and compaction was lower than projected over the past six months; however, water in the lake and several cold periods had unexpected positive effects on the invasive aquatic vegetation in the lake.
Emergency Action Plan
In early December 2023, consistent with the Emergency Action Plan for Lake Munson implemented to address the impact of heavy rainfall, the dam gates were closed to prevent downstream flooding. On December 2, 2023 Leon County received total rainfall depths ranging from three and one-half to six inches, depending on the area. This large rainfall resulted in high water levels at Ames Sink and Lake Munson rapidly filling. To protect downstream properties from flooding and allow Ames Sink time to recover, the gates on Lake Munson dam were closed on December 4, 2023. Weekly rainfall events during the next six weeks kept water levels high at Ames Sink and the lake remained at full pool (Attachment #3). During this period, staff coordinated with FWC and continued to monitor downstream conditions and the water quality at Lake Munson. On January 17, 2024, County staff observed the conditions at Lake Munson and downstream. The water in Lake Munson was not turbid (appeared clear) and downstream water levels were low with ample storage capacity. As per the Emergency Action Plan, and consistent with conversations with FWC, all conditions at Lake Munson were appropriate for the reopening of the gate. At that time, the gate was opened to slowly lower the water level in the lake to resume the drawdown without adversely affecting downstream properties. Over the following month and a half, staff monitored the downstream conditions as the lake drained. By the beginning of March, the lake had fully drained.
Benefit of a Full Lake
Lake Munson held water, primarily at full pool, for a period of three months during the winter (December 2023 thru February 2024). While this period did not allow the sediment to dry out as planned, the lake’s response during this period had positive and unexpected results. When the lake refilled, it woke up the invasive exotic water hyacinth seeds in the sediment and they began to germinate (grow). The longer the water stayed in the lake, the more seeds germinated. Hyacinth shades out and hinders the growth of the native (good) vegetation, which are important to wildlife. The hyacinth normally blooms in the spring through early fall, so the hyacinth that grew this winter did not replenish the seed bank in the lake. During this period, the area experienced several nights of cold weather, which stressed or killed off much of the hyacinth. As the lake drained, any hyacinth that was not killed with the cold were stranded and dried out with no water. This filling and then draining of the lake used up some of the hyacinth seeds in the seed bank, leaving them unavailable to germinate when the lake is refilled following the drawdown. This blooming and dying of the hyacinth will be beneficial when the Lake refills because there will be less hyacinth that will need to be treated and it provides more opportunity for native vegetation growth.
Enhanced Monitoring
The current Leon County Water Quality Monitoring Program is a comprehensive data collection and evaluation program to ensure the long-term health of the County’s waterbodies, including quarterly water quality sampling and biological assessments, summarized in an Annual Report. The Action Plan expands on the existing County Water Quality Program to provide for enhanced monitoring of Lake Munson and is centered around data collection and analysis, focusing on the overall health of the lake during the drawdown and in the two years after the lake is refilled. Since the September 2023 update, the Drawdown Water Quality Study has continued, and an additional aerial topographic survey has been conducted. Results of the enhanced monitoring so far show that the water quality leaving Lake Munson continues to meet the Wakulla Springs TMDL for nitrates, the lake bottom sediments continue to consolidate, and the system is further stabilizing. The complete results of the Drawdown Water Quality Study and Aerial Topographic Survey will be provided to the Board at the next six-month update.
Drawdown Water Quality Study
With the extension of the drawdown through Spring of 2024, the Board approved the addition of a Drawdown Water Quality Study to the Lake Munson Action Plan. The Drawdown Study supplements the County’s quarterly water chemistry sampling with additional sampling to attain monthly water quality data in Munson Slough both immediately upstream and downstream of Lake Munson until the Post-Drawdown Study begins in May 2024 with the refill of the lake. The samples collected during the drawdown provide information on the water chemistry concentrations entering and leaving the lake and insight into how the lake is reacting during the drawdown.
Staff has reviewed the sample results from August 2023 through February 2024 and, along with previously collected drawdown samples, evaluated for trends (Attachment #4). Throughout the drawdown, the water leaving the lake has continued to meet the State’s Total Maximum Daily Load (TMDL) for nitrates for Wakulla Springs. Since October, the water leaving the lake has also met the TMDLs for nitrogen and phosphorus in Munson Slough. Overall, the nutrient concentrations leaving the lake are trending lower while the nutrient concentrations entering the lake generally remain the same.
While the water quality leaving the lake continues to generally improve through the drawdown, nutrient concentrations spiked in September 2023. This spike was due to a higher amount of very fine loose sediment leaving the lake. As discussed, the drawdown was temporarily suspended due to Hurricane Idalia. When the drawdown resumed, the September water quality samples were collected at the tail end of the renewed drawdown, capturing nutrient levels that were associated with a syphoning effect. As the last of the water drained out of the lake, a syphon was created, where water pulled very fine loose sediment from the channel of the lake into the water column. This transported sediment caused a temporary nutrient spike. The phosphorus concentrations spiked higher than nitrogen because phosphorus binds to the sediment better than nitrogen.
Sample results continue to indicate the lake bottom sediments continue to consolidate, the system further stabilizing, and the nutrient concentrations of the water entering and leaving the lake continue to converge, or grow closer together. The significant investment in upstream improvements within the Lake Munson drainage basin have thereby improved the water quality entering Lake Munson, which has not changed with the drawdown. Since April, in Munson Slough below the lake, the nitrogen and phosphorus concentrations have primarily been just above or better than the State TMDL. County staff continues to evaluate the data and provide updates to the SAC.
Aerial Topographic Survey
The original Lake Munson Action Plan included two aerial surveys of the lake bottom, one at the beginning of and one at the end of the drawdown. With the extension of the drawdown through Spring 2024, quarterly aerial surveys through the drawdown were added to the Action Plan. These surveys will provide data on the elevations of the lake bottom and can be used to determine the amount of compaction of the sediment as the drawdown progresses and to evaluate the benefits of the additional drawdown time for consideration during future routine drawdowns.
An aerial survey was flown at the beginning of the drawdown in November 2022, followed by aerial surveys in April 2023, August 2023, and October 2023. The first survey in 2024 was planned for January; however, most of the lake was submerged through the month and information on the sediment could not be obtained so a survey was not flown. Data comparison of the exposed lake bottom elevations since beginning the drawdown continue to show that the sediment has compacted, with the most compaction around the edges, which is expected as the outer portions of the lake will be exposed more often than the middle of the lake. The aerial photos show the progression of the beneficial vegetation in the lake through the drawdown and data indicates sediment compaction.
Long-Term Best Management Practices
The Lake Munson Action Plan includes an expanded role of the County in managing Lake Munson, in coordination with State agencies on long-term restoration opportunities. In preparation of the lake refill, anticipated to begin in May, staff has conducted initial treatments for invasive exotic aquatic vegetation. In addition, a Water Quality Grant application was submitted to the Northwest Florida Water Management District for an expanded Munson Slough Bank Stabilization project. The long-term strategies and invasive exotic vegetation management program are based on best practices for lake management. The County’s management program has been tailored to the needs of Lake Munson including use of a single contractor for vegetation and algal bloom management and treatment in Lake Henrietta, Munson Slough, and the flow through channel prior to refill of the lake in May.
Invasive Exotic Vegetation Management Program
The Action Plan includes an invasive exotic vegetation management program to supplement the State’s treatment of Lake Munson. Invasive exotic plants adversely impact native plant communities and, if left untreated, will rapidly colonize and take over a waterbody. Native species create a healthier ecosystem; they allow a variety of plants to grow and serve as food and nesting habitat for fish and wildlife. As a State-managed waterbody, the County historically relied on the State for sole treatment of invasive exotic aquatic vegetation.
An algal bloom management program was included in the Action Plan at the request of area residents to mitigate the naturally occurring blooms on Lake Munson by treating them when they occur, providing relief to area residents effected by the blooms. Neither the County nor State agencies have historically treated algal blooms on Lake Munson.
The invasive exotic vegetation and algal bloom management programs will be implemented at the same time utilizing a contractor for the treatment of invasive aquatic plants and algal blooms at Lake Munson. In November 2023, the County selected Estate Management Services from the County’s Continuing Service Contractor list to perform long-term lake management services. The scope of work the contractor will perform includes applying treatment chemicals to the water in Lake Henrietta, Munson Slough, and Lake Munson to reduce algal blooms and invasive plants, while ensuring public safety by minimizing chemical use in and around the waterbodies.
This scope of work has been agreed to by FWC’s Invasive Plant Management section. FWC has issued an Aquatic Plant Permit to the County for the invasive exotic vegetation and algal bloom treatments for this plan. Detection of invasive plants and algal blooms will be conducted by proven methods that fully analyze the entire lake.
This winter, Lake Henrietta, Munson Slough, and the Lake Munson flow through channel had several invasive exotic aquatic species including hydrilla and some hyacinth that survived the cold. Treating this vegetation prior to refill of the lake slows down or prevents the spread of the invasive exotic vegetation when the lake is refilled and gives the native species a head start in growth. The native plant species can then colonize the waterbodies more efficiently and become well established, resulting in a lower level of competition against the invasive exotic species. The initial treatment for invasive exotic aquatic vegetation occurred in Lake Henrietta, Munson Slough, and the flow through channel in Lake Munson in mid-March. Additional treatments prior to refill of the lake will occur through April, with the frequency determined by the condition and health of the lake system.
Area residents requested the use of a peroxide treatment of the algal blooms using a product called Lake Guard, which was developed by BlueGreen Water Technologies (BlueGreen). In mid-February, staff met with representatives from BlueGreen to learn more about the potential use of Lake Guard on Lake Munson. BlueGreen does not have the capability to apply the chemical but instead contracts the work. More information on product specifics and pricing has been requested from BlueGreen. This information will be discussed with the County’s contractor, who has developed and permitted a plan including selecting specific products for algal bloom treatment that will be effective on Lake Munson. If Lake Guard is found to be a viable alternative treatment method for the lake, BlueGreen can work with the County’s contractor for application.
Staff continually coordinates with multiple State agencies to identify grant opportunities at Lake Munson. In prior years, our coordination has led to great success with Leon County having been awarded grants from FWC for invasive exotic treatment within County parks. As outlined in the Lake Munson Action Plan, staff will continue to coordinate with State agencies to identify both routine and innovative technologies future grant opportunities for use in Lake Munson. Those grant opportunities will include support for long-term lake management.
Munson Slough Embankment Repair Project Funding
At the February 20, 2024 meeting, the Board approved a $2 million grant request from the Northwest Florida Water Management District (District) for the Munson Slough Embankment Repair Project to design and construct ecosystem and habitat improvements within Munson Slough between Lake Henrietta and Lake Munson. The County’s current budget includes $2 million funding for the design and construction of the Munson Slough Embankment Repair Project, with construction occurring in 2026. This project is to mitigate bank erosion along Munson Slough.
If approved by the District, the grant would generate $2 million in new state funds for this project and would enable the County to expand the project beyond bank repair (current project scope). This expanded scope would include creating pools and rapids in Munson Slough that is similar to a natural channel ecosystem and would further improve water quality and wildlife habitat downstream.
Notice of awards for approved projects is anticipated in late 2024. If awarded, design of the project would begin in 2025 with construction to follow in 2026.
Each year, Leon County submits appropriation requests to the Florida Legislature based on the Board’s priorities and this year, a $250,000 request to support the Lake Munson Embankment Repair project was included in the State Fiscal Year (SFY) 2024-2025 budget as approved by the legislature. The SFY 2025 budget is awaiting signature of the Governor. If approved by the Governor, the additional state fundings will be incorporated into the project budget.
Next Steps
In the next six-months, a final aerial topographic survey will be collected, the drawdown will conclude, and the lake will be slowly refilled. The Post-Drawdown Water Quality Study will commence, and the invasive exotic vegetation management program will continue in conjunction with the addition of the algal bloom treatments, as needed. County staff will continue to evaluate the information collected through the enhanced monitoring program, which will be presented to the SAC in quarterly updates. Coordination on the progress of the drawdown with State-agency partners and engagement with the Workgroup remain ongoing. And finally, staff will continue to provide six-month updates to the Board on the progress of Lake Munson throughout the enhanced monitoring.
Aerial Topographic Survey
The final aerial topographic survey is planned for April, which will provide information on the total sediment compaction through the course of the drawdown. After the County has received the final survey, County Water Resources and GIS staff will analyze the data to determine the amount of compaction and compare water depths to historical information. This information will be reviewed by the SAC and presented to the Board.
Drawdown Conclusion and Lake Refill
In early May, following collection of the final aerial topographic survey, the drawdown will conclude and the lake will slowly be refilled. FWC has recommended that the target rate of refill is to raise the water elevation up approximately one foot per month. At this time, the goal is to raise the elevation at this slow rate; however, given the large drainage area that flows through Lake Munson, the rainfall through the summer may change this process. Staff will coordinate closely with FWC through the refill process.
A slow refill process is best for the lake and will minimize the risk of shocking the ecosystem. By gradually raising the water level in the lake, the aquatic vegetation in the lake has the opportunity to adapt to the new conditions and what does not adapt will slowly die off. A quick and permanent refill of the lake could result in a total plant kill and subsequent algal bloom. The slow refill results in better water quality and aesthetics. The slow refill of the lake in conjunction with the invasive exotic aquatic vegetation management will allow the native species to survive and give them a head start.
Consistent with the efforts throughout the drawdown, the County will continue to monitor water levels and conditions in the lake and downstream, as well as potential significant rainfall events in coordination with FWC.
Post-Drawdown Water Quality Study
Once the lake begins to refill, it will take time for the nutrient levels and ecosystem to stabilize. Water quality sampling for two years following the drawdown will provide an excellent opportunity to monitor and quantify the effects of the drawdown on water quality in Lake Munson. Beginning in May, monthly water quality and flow samples will be collected at four locations, two upstream of Lake Henrietta, one upstream of Lake Munson, and one downstream of the lake. The samples will be analyzed for the County’s standard water quality parameters. The results will be evaluated over the two years following the drawdown to track the lake’s response and gauge the effectiveness of the drawdown.
Invasive Exotic Vegetation and Algal Bloom Management Programs
As a long-term lake management strategy included in the Lake Munson Action Plan, invasive exotic aquatic vegetation management will follow the March and April treatments into the months ahead and will be supplemented with algal bloom treatments in Lake Munson as needed. Treatments will be applied in Lake Henrietta, Munson Slough, and Lake Munson using timing and algae control strategies that reduce blooms and invasive plants, while ensuring public safety by minimizing hazardous chemical use in and around the lake. The treatments will be routine with the frequency determined by the condition and health of the lake system.
Conclusion
This item provides a six-month status update on the implementation and ongoing efforts related to the Lake Munson Action Plan. This item highlights the $290 million investment over four decades including 28 projects and 21 best management practices to restore Lake Munson, the measurably improved water quality in the lake and in Munson Slough, and an overview of the Lake Munson Action Plan. This item also provides an update on the implementation of the Action Plan over the past six months, implementation of the Emergency Action Plan and the resulting benefits, the enhanced monitoring data collected with a summary of the trends and observations, the implementation of the long-term invasive exotic aquatic management program, the submission of a grant to improve water quality in Lake Munson, and next steps.
Since the 1980s, $290 million has been invested to restore Lake Munson including infrastructure and restoration projects that provide water quality treatment, reduce sediment transport, and collect trash. These significant investments have resulted in noticeable water quality improvements in Lake Munson such that the nutrient concentrations in Munson Slough (upstream of the lake) are below the target levels established by the State. Within Lake Munson, the nitrogen concentrations have been consistently below the State’s target and the phosphorus concentrations have steadily declined to approach the State’s target. Despite the measurably better water quality, in-lake mitigation, and investments in upstream infrastructure, Lake Munson experienced a minor setback in the summer of 2022 with an algal bloom, rapid growth of invasive exotic aquatic vegetation, and a fish kill.
The Lake Munson Action Plan, approved by the Board on October 11, 2022, includes short- and long-term strategies to continue restoration and ecological improvement of Lake Munson and articulates the decades of investments, improving the water quality and ecological health of Lake Munson through upstream infrastructure projects. The Action Plan takes a holistic approach through a drawdown coupled with enhanced monitoring of the lake’s response, while also providing long-term strategies to supplement the State’s in-lake vegetation management activities and deliver a higher level of service to County residents. During a six-month status update at the March 21, 2023 meeting, the Board approved modifications to the Action Plan including extending the drawdown through Spring of 2024 as a result of higher than anticipated winter rainfall, to be carried out in coordination with the FWC and with additional enhanced monitoring.
Since the September 2023 update, the drawdown and enhanced monitoring continued, the Emergency Action Plan for the lake was implemented in early December and continued through January after frequent rainfall in late November, the invasive exotic vegetation management program has begun, and monthly water quality data has been collected and analyzed. Overall, the nutrient concentrations leaving the lake are trending lower while the nutrient concentrations entering the lake generally remain the same and nutrient concentrations in the Slough (above and below the Lake) are primarily better than the State’s TMDL for Munson Slough . Throughout the drawdown, the water leaving the lake has continued to meet the State’s TMDL for nitrates for Wakulla Springs.
The long-term strategies in the Action Plan are centered around proactive management of the lake vegetation and sediment, including an expanded role of the County in managing Lake Munson, in coordination with State agencies. In preparation of the lake refill this Spring, staff has conducted initial treatments for invasive exotic aquatic vegetation and algal bloom treatments will commence upon refill of the lake. In addition, a $2 million Water Quality Grant application was submitted to the Northwest Florida Water Management District for an expanded Munson Slough Bank Stabilization project. That grant is under review by the District and an award is anticipated later this year. Importantly, a State Legislative appropriation for $250,000 for this same project was awarded by the Florida Legislature during the 2024 legislative session.
And finally, the drawdown will conclude in May 2024. Staff is already working in preparation for this and the Post-Drawdown Water Quality Study will coincide with the refilling of the lake to monitor the response and gauge effectiveness of the drawdown. Coordination with State-agency partners to evaluate the progress of the drawdown remains ongoing and quarterly updates on the progress of the drawdown and the data collected through the enhanced monitoring are presented to the SAC for review and evaluation. The next status update will be presented to the Board at the October meeting and will continue every six months through the enhanced monitoring period, providing updates on the progress of the Action Plan and a summary of the data collected and results.
Options:
Recommendation:
Option #1
Attachments: