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Leon County
Board of County Commissioners Agenda Item#34 September 12, 2023 |
| To: | Honorable Chairman and Members of the Board |
| From: | Vincent S. Long, County Administrator |
| Title: | Lake Munson Action Plan and Drawdown Status Update |
| Review and Approval: | Vincent S. Long, County Administrator |
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Department/Division Review and Approval: |
Alan Rosenzweig, Deputy County Administrator 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. As directed by the Board, these Action Plan updates shall occur every six months during the drawdown (ongoing) of Lake Munson and will continue for 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 Drawdown.
Report and Discussion
Background:
This item provides a status update on the implementation and ongoing efforts related to the Lake Munson Action Plan (Attachment #1), as approved by the Board at the October 11, 2022 meeting and modified at the March 21, 2023 meeting. As directed by the Board, these Action Plan updates shall occur every six months during the drawdown (ongoing) of Lake Munson and will continue for two years following the refilling of the lake.
This item details the $290 million of investments over four decades including over 28 projects and 21 best management practices (BMPs) to restore Lake Munson, the measurably improved water quality in the Lake and Munson Slough, and an overview of the Lake Munson Action Plan. The item also provides an update on the implementation of the Action Plan over the past six months, the enhanced monitoring data collected with a summary of the trends and observations, sediment management strategies implemented by other communities, a resident petition calling for action at Lake Munson, public outreach by the County and the launch of a dedicated Lake Munson website, and an update on the State’s studies on health impacts from algal blooms and other topics tracked by staff.
This status report advances the following FY2022-FY2026 Strategic Initiatives:
These particular Strategic Initiatives aligns with the Board’s Environment Strategic Priorities:
Lake Munson, located on the south side of Tallahassee, receives much of its flow from urban and residential 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. In the early 1980s, Lake Munson was ranked one of the most polluted lakes in the state.
Since the 1980s, $290 million over four decades has been invested in ongoing efforts to restore Lake Munson and improve the water quality through more than 28 projects and 21 BMPs (Attachment #2). Leon County, the City of Tallahassee, and Blueprint Intergovernmental Agency have completed 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 erosion, removal of trash and the sediment delta from Lake Munson, and restoration of the wetlands around Lake Henrietta and Lake Munson. Additional best management practices have been implemented to preserve wetlands, improve water quality, and manage waterbodies. Routine drawdowns of Lake Munson have been conducted approximately every ten years to allow the nutrient-rich sediment to dry out and form a cap, reducing the nutrients leaving the sediment.
The water quality and ecological health in Lake Munson have noticeably improved with the $290 million of investments in capital projects and restoration activities resulting in a steady decline of nutrient concentrations (Attachment #3). 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, 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 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 Plan implementation and provides new data and information.
The drawdown is a key component of the Lake Munson Action Plan and was initiated to quickly mitigate the rapid growth of hydrilla and algal blooms but also as a sediment management strategy. The drawdown allows the nutrient-rich sediments 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. During the six-month 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 and in coordination with the Florida Fish and Wildlife Commission (FWC).
An enhanced monitoring program during, and in the two years following the drawdown, will provide valuable information on the lake’s response to the drawdown. A Drawdown Water Quality Study, approved by the Board at the March 21, 2023 meeting in conjunction with the drawdown extension, collects monthly water chemistry samples of the water entering and leaving the lake and provides information on the stability of the system with the changes in water levels. Quarterly aerial topographic surveys will provide data on how much the sediments are compacting through the drawdown and 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 long-term strategies in the Action Plan are 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 quicker response allowing smaller areas of treatment and less impact to the system. An algal bloom management program will mitigate the naturally occurring blooms on Lake Munson by treating them when they occur, providing relief to area residents effected by the blooms. 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. Engagement with area residents continues and the Lake Munson citizens group (Workgroup) are encouraged to attend the quarterly SAC update meetings to discuss their concerns. Status updates to the Board every six months will continue, providing updates on the progress of the drawdown and a summary of the data collected and results.
As detailed in the analysis section, this item serves as the status report on Lake Munson to be provided to the Board every six months through the drawdown and two-year enhanced monitoring of lake conditions. In addition, this report provides an update on activities and progress since the update in March 2023. More information on the implementation of the Action Plan since adoption can be found in in the March 21, 2023 agenda item (Attachment #4).
Analysis:
This six-month status update provides updates on the drawdown and implementation of the Lake Munson Action Plan. Since the previous six-month update in March, the drawdown and enhanced monitoring continued, monthly water quality data has been collected and analyzed, a review of sediment management strategies in other communities has continued, a new petition by the Workgroup has emerged, engagement with the SAC has been ongoing, public engagement has been expanded through the launch of a new Lake Munson website, and staff continues to monitor the State’s study of health-related issues related to algal blooms.
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 the Spring of 2024. Since then, the drawdown has continued in coordination with FWC. With the extension of the drawdown, the sediment has 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.
The bottom of Lake Munson has filled in with terrestrial plants, or plants that live on land (Attachment #5). The vegetation is predominantly native and include beneficial species such as wild millet, smartweed, riverhemp, and small amounts of dog fennel. These plants are beneficial to the ecosystem because they are attracters of birds, such as turkeys and ducks, and are great for erosion control. When the lake is refilled, the plant stalks will provide excellent fish habitat. Despite the benefits to the ecosystem, the Workgroup has called for the beneficial vegetation to be removed. The concept of removing the vegetation, through mowing or burning, was discussed with FWC and is not recommended or a viable option due to the loss and destruction of the ecological benefits as well as the physical constraints. Mowing or burning would eliminate the native and beneficial plant species and could allow invasive exotic vegetation to dominate. The vegetation roots hold the sediment in the bottom of the lake in place and prevent erosion. Should the root systems be destroyed during the vegetation removal, the sediment could be transported downstream. Even if removal of the vegetation was desirable, the physical conditions of the lake inhibit removal of the vegetation in the lake. The refilling and draining of the lake results in uneven surfaces, mucky areas, and pools of water that are not visible. These conditions prohibit equipment from accessing the lake to mow. For the same reasons, burning is not a viable option as the conditions limit the ability to create fire breaks needed for burning and full access for management. In addition, FWC has concerns about how the heat from a controlled burn would impact the contaminates in the sediment and the health of the lake.
With the extension of the drawdown approved at the March Board meeting, an emergency plan has been developed to close the dam in anticipation of flooding or severe weather events, such as a hurricane, until the sediment has an opportunity to settle. Between March and early August, Lake Munson held water on several occasions, but like last winter, the water receded within a few days with dry periods between storm events (Attachment #6). In late August, in anticipation of Hurricane Idalia, the Lake Munson dam gates were temporarily closed, slowing down the incoming water allowing sediments to settle as well as protecting downstream properties from potential flooding. Staff will assess the rainfall and impacts associated with Hurricane Idalia to determine the appropriate timing for reopening the dam gates. Staff will continue to monitor water elevations in the lake and downstream, as well as potential significant rainfall events, for the need to temporarily suspend the drawdown again in the future.
Dredging continues to not be viable for in-lake management and will cause more harm than good. Current information and monitoring results indicate drawdowns remain the preferred management strategy for Lake Munson. Dredging remains not viable with negative results including resuspending sediment and contaminants, potentially contaminating drinking water, degrading aquatic and wildlife habitats, microorganism death thereby reducing fish food source, neon green water from massive algal blooms and subsequent explosion invasive exotic vegetation due to no vegetation or seed source, and underlying karst features with sinkhole potential (Attachment #7). New and innovative technologies are continually developing and are reviewed by County staff and any opportunities will be presented to SAC and State agency partners for review. If the science changes and viable alternative lake management strategies emerge, the new opportunities for the Action Plan to evolve will be brought to the Board for consideration.
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. The program includes quarterly water quality sampling and annual sediment and biological assessments of 12 lakes, 27 streams, and 2 river systems at a total of 70 stations throughout the County. The County’s Water Resources Scientist, Water Resources Limnologist, and Engineers review and analyze the data for trends in the system and summarizes the information in the Annual Water Quality 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 years after the lake is refilled. Since the March 2023 update, the Drawdown Water Quality Study kicked off, additional aerial topographic surveys have been conducted, and point-source testing samples for PCBs and other contaminants in Munson Slough have been analyzed.
Drawdown Water Quality Study
At the March 21, 2023 meeting, with the extension of the drawdown, the Board approved the addition of a Drawdown Water Quality Study to the Lake Munson Action Plan. The 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 for the remaining duration of the drawdown. The samples provide information on the water chemistry concentrations entering and leaving the Lake and provide insight into how the lake is reacting during the drawdown.
Staff has reviewed the sample results from March through July and evaluated for trends. 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. The first samples collected (March 2023) showed the nutrient concentrations leaving the Lake were higher than the concentrations entering the lake, likely the result of an unstable system in the lake. Unstable systems can be caused by changes in vegetation in the lakebed or rising and lowering water levels, and can cause water quality parameter changes as the water moves through the lake. The exact cause of the instability in the system and elevated concentrations is unknown but based on other elevated water chemistry parameters (e.g., chlorophyll-a, biological oxygen demand, and suspended and dissolved solids) it is likely that an isolated shallow pool of water was breached and reconnected to the main flow-through channel, or a puddled area of water that started draining out into the main channel. The lake bottom had significantly less vegetative cover in March and this disturbance could have occurred by a significant weather event or even an animal, such as an alligator or deer breaching the edge of a shallow pool as they travel through the system, around the time of the sampling. Such an event could cause the breach by disturbing the lake bottom and allowing the pool to slowly drain out into the water flowing through the lake and into the downstream water sample.
Based on current data, the elevated concentrations in March appear to be an outlier or an anomaly in the data that is inconsistent with the data collected the following months. Sample results from each subsequent month indicate the lake bottom sediments continue to consolidate, the system further stabilizes, and the nutrient concentrations of the water entering and leaving the lake continue to converge, or grow closer together (Attachment #8). 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. The nutrient concentrations in Munson Slough above the lake remain lower than the target levels established in the State TMDL. Since April, in Munson Slough below the lake, the nitrogen and phosphorus concentrations have been just above and just below the State’s limit, with the July nitrogen concentrations and the August nitrogen and phosphorus concentrations better than the State TMDL. County staff continues to evaluate the data and provide updates to the SAC.
Aerial Lake Bottom Survey
The original Lake Munson Action Plan included two aerial surveys of the lake bottom, one prior to and one following the drawdown. With the extension of the drawdown through Spring 2024, quarterly aerial surveys through the drawdown were added to the 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.
Aerial surveys were flown at the beginning of the drawdown on November 29, 2022, in the spring on April 17, 2023, and again in the first week of August (Attachment #9). The second survey occurred shortly after a rainfall event, which meant more water was in the lake than during the first survey. Data comparison of the exposed lake bottom elevations between the first and second flights shows that the sediment is beginning to compact, with the most compaction around the edges. These results are expected as the outer portions of the lake will be exposed more often than the middle of the lake. At the time of this writing, the results of the third survey were still being analyzed by staff and will be reviewed by the SAC.
Point-Source Testing
The goal of the point-source testing is to validate the results of a 2019 study by the Florida Department of Environmental Protection Division of Florida Geological Survey (2019 FGS Sediment Study) and an associated review by Terracon Consultants, Inc. (2021 Terracon Report), which determined the contaminants are tightly bound to the sediment and not leaching into the water or contaminating the water. Water samples from Lake Munson and Munson Slough, upstream and downstream of the lake, were collected and analyzed for PCBs and the other contaminants identified in the sediment during the 2019 FGS Sediment Study. The results of the samples collected in the lake were included in the March 21, 2023 item (Attachment #4) and the sample results from Munson Slough are included in this item.
Contaminant sampling at the stations upstream and downstream of Lake Munson were taken at the beginning of March in conjunction with the County’s routine Water Quality Monitoring Program quarterly sampling. The routine quarterly samples on this day had various parameters with elevated nutrient and chlorophyll-a concentrations leaving the lake, indicating the lake was an unstable system at the time.
The results from the contaminant samples support the 2019 FGS Sediment Study and the 2021 Terracon Report to show that the PCBs and other contaminants in the sediment are not contaminating the water column. In short, of the 115 contaminants analyzed, only five were detected in the Munson Slough water samples, all of which were metals (arsenic, barium, chromium, iron, and lead). Upstream of the lake, of the five metals detected, all were well below the State’s water quality standards. Downstream of the lake, three of the five metals detected were below the State’s water quality standards, while lead concentrations in the water were at the State water quality standard and iron concentrations were above the State’s water quality standard. Both lead and iron are naturally occurring in soils.
Lead is currently included in the County’s routine water quality testing for waterbodies county-wide. Available data for stations across the County show random hits for lead at random times. The lead exceedances are thought to be caused by relic anthropogenic, or human caused, sources combined with enhanced metal mobility due to the naturally acidic soil and water conditions commonly found in Leon County. Because lead is a parameter included in the routine water chemistry suite, monthly samples collected as part of the routine quarterly sampling and the Drawdown Water Quality Study will test for lead and County staff will continue to monitor the results.
Iron is scientifically known to have a directly proportional relationship with chlorophyll, meaning elevated levels of iron will occur at the same time as elevated levels of chlorophyll-a, due to the photosynthesis process occurring in the water. The point-source samples with the elevated iron levels were collected at the same time as the routine quarterly water chemistry samples with the elevated chlorophyll-a concentration. Similar to the nutrient concentrations in the March sampling event, the exact cause of the elevated iron levels is not known. As a result, iron has been added to the County’s routine water chemistry suite; monthly samples collected as part of the routine sampling and the Drawdown Water Quality Study will test for iron so that staff can continue to monitor the results.
Monthly water quality sample results for Munson Slough in April through July had no additional exceedances of State water quality standards for lead or iron, further supporting the results of the 2019 FGS Sediment Study and the 2021 Terracon Report that PCBs and other contaminants are tightly bound to the sediment in the lake and are not affecting water quality. The elevated levels of lead and iron in the March samples downstream of the lake appear to be an isolated incident. County staff will continue to monitor water quality data and the results will be shared and discussed with the SAC.
Long-Term Best Management Practices
The long-term best management practices include a more proactive approach and expanded lake management role by the County, along with continued coordination with State-agency partners on long-term restoration opportunities. Components such as the Invasive Exotic Vegetation and Algal Bloom Management Programs will not commence until the lake is refilled while exploration and review of lake management strategies is ongoing.
Innovative Technology Exploration
Strategies for lake management continue to evolve and grow as new information becomes available and new technologies develop. County staff are constantly evaluating the data, science, and strategies for best practices and emerging opportunities toward the goal of water quality and ecological improvements that do the most good with minimal negative impacts. In the summer of 2022, Leon County applied for a Florida Department of Environmental Protection (FDEP) Fiscal Year 2022-2023 Innovative Technologies Grant for a pilot project on Lake Munson utilizing Biochar, a charcoal-like substance capable of removing the dissolved nutrients that facilitate algal blooms; however, Leon County was not selected as a recipient of this grant. Of the ten grants that were awarded, nine are for projects involving algal bloom prevention. These projects will test lake management strategies that may be viable on Lake Munson in the future. County staff will continue to monitor the development and results of these projects and review for applicability at Lake Munson. These opportunities will be discussed with State-agency partners and the SAC, with any viable options presented to the Board.
Sediment Removal Impacts and Strategies
Lake Munson is a unique system and strategies that work in other areas are not necessarily best for Lake Munson. Based on the science and knowledge of the system, dredging the lake would pose detrimental impacts to the ecosystem such as resuspending sediment and contaminants, potentially contaminating drinking water, degrading aquatic and wildlife habitats, death of microorganisms and reduction of fish food source, initiate massive algal blooms followed by uncontrollable invasive exotic vegetation growth, or potentially opening a sinkhole in the lake. While recent dredging projects have been implemented in other parts of the State, the different conditions between these systems and Lake Munson make dredging viable there, but not at Lake Munson.
In Pinellas County, a joint project with the Southwest Florida Water Management District (SWFWMD) and FDEP dredged Lake Seminole to improve water quality. The roughly $18 million project was funded by the County, SWFWMD, and State legislative appropriations. Lake Seminole was created when an arm of Long Bayou, a saltwater system, was dammed to create a freshwater lake. Unlike Lake Munson where the sediments are predominantly stable on the bottom of the lake and held in place with vegetation, the sediments in Lake Seminole were frequently disturbed which resulted in degraded the water quality. The poor water quality in Lake Seminole continued to degrade, whereas the water quality in Lake Munson has measurably improved over the years. Further, the sediment in Lake Seminole did not contain contaminants or metals so they were disposed of at a nearby park to create ball fields.
In Sumter County, Lake Panasoffkee, an Outstanding Florida Waterbody with good water quality, was dredged to improve the fish habitat, restore the shoreline, and improve navigation. The project was led by the SWFWMD and was a cooperative effort with the Lake Panasoffkee Restoration Council (a group established by the Florida Legislature) and funded by the Withlacoochee River Basin Board, Florida Department of Transportation (FDOT), and FWC, with additional funding from State and Federal legislative appropriations. The $29.5 million project was predominantly funded by State legislative appropriations. Unlike Lake Munson that receives water from runoff through Munson Slough, Lake Panasoffkee predominantly receives flow into the lake from the Floridian aquifer. Over time, low water levels have allowed trees and shrubs to fill in the lake. Sediment in Lake Munson was transported to the lake years ago; whereas, in Lake Panasoffkee, a chemical reaction occurs between the groundwater and lake water continually which creates sediment that settles to bottom of the lake and covers fish-spawning areas. In Lake Panasoffkee a chemical reaction occurs between the groundwater and lake water continually, creating sediment that settles to bottom of the lake and covers fish-spawning areas. The source of the sediment in Lake Panasoffkee makes it clean and good quality, free of relic nutrients and contamination.
When dredging is utilized for a site with sediment contamination, the sediments are considered high-risk to ecological and human health. Sites with unacceptable risks to human health and the environment are cleaned through the EPA Superfund program, in collaboration with other EPA programs. These sites are most often a result of hazardous waste being dumped, left out in the open, or otherwise improperly managed, and include manufacturing facilities, processing plants, landfills, and mining sites. The clean-up methods often utilized at these sites includes dredging or excavation, and many are done as a result of a lawsuit against a corporation accused of deliberate environmental pollution.
Based on the information and science today, the contaminants in Lake Munson are considered low-risk (to ecological and human health) in their present state because they are tightly bound to the sediment, as supported by the water quality contaminate testing, and pose a greater threat to the lake from dredging activities (Attachment #7). When the science or data changes or if dredging becomes a viable option, information will be brought to the Board at that time.
Lake Munson Workgroup Petition
On July 6, 2023 the Lake Munson Workgroup started an online petition calling for action from the Leon County and City of Tallahassee Commissioners to address eight concerns surrounding Lake Munson. The eight concerns primarily center around the areas where the County and Workgroup have different goals for Lake Munson and differing best management strategies to achieve a healthy system, specifically the drawdown, dredging, and upstream point-source testing. The eight concerns listed in the petition and a response to each concern by staff is included in Attachment #10. This petition began circulating approximately ten months after the Workgroup provided ten specific requests to the County in writing which were addressed in the October 11, 2022 status report (Attachment #11).
The County’s goals and vision for Lake Munson include water quality better than the State standards, a healthy ecosystem with native vegetation with minimal need for human intervention, a healthy and beneficial fish and wildlife habitat and population, and fewer algal blooms. The Action Plan was developed to achieve these goals based on best practices for lake management.
The Workgroup’s goal for Lake Munson is a clear water, sandy bottom lake, free of vegetation and algal blooms, that would be achieved through dredging. While this vision for the lake is well intended, it is not physically attainable without harmful processes and outcomes nor is it ecologically desirable. In this geographic area, unless the waterbody is chemically altered or treated, vegetation and algae will exist in a lake; this is a natural occurrence when light can penetrate the water surface and the water contains nutrients. Lake Munson has naturally clear water allowing for light penetration and it also has nutrients. Typical visibility in Lake Munson is approximately 3 feet down from the surface; on a good day, the bottom of the lake can be visible. This clear water allows light to penetrate and thus vegetation growth. Lakes with dark water naturally have less aquatic vegetation. For example, Lake Cascade has good water quality but due to various natural conditions has naturally tannic (i.e., dark color) water. The visibility in Lake Cascade is only about six inches below the surface, resulting in minimal aquatic vegetation in the lake because the water is so naturally dark that light cannot penetrate much beyond the surface. Even though Lake Munson is just downstream of Lake Cascade, the two lakes are fed from different sources and have much different aquatic plant communities.
Beyond the natural differences in water visibility, a system free of nutrients is not possible. Nutrients will always be present in Lake Munson even if the bottom were to be dredged and the relic nutrients in the sediment were removed. Nutrients are found in nature, even in the most isolated areas and untouched waterbodies. For example, atmospheric deposition of nutrients will cause an open container of distilled water to eventually turn green. Because light and nutrients will always be present in Lake Munson, aquatic vegetation and/or algae will always be present to some extent. Sunlight penetrating the water and the nutrients in the water are used by both aquatic vegetation and algae. If one of these is removed, there will be more light and nutrients for the other to use. Removing all the vegetation from the lake will result in a massive algal bloom. In 2004, apple snail populations exploded and consumed all of the aquatic vegetation in Lake Munson, resulting in lake-wide algal blooms. Removal of all aquatic vegetation in a lake gives way for invasive exotic species to establish. Once the invasive exotic vegetation takes over the Lake it is unlikely to ever be controlled. A lake-wide chemical treatment would be required to kill the invasive exotic vegetation and gain control, which would be followed by lake-wide algal blooms with the sudden loss of vegetation in the lake, and more invasive exotic species, in a perpetual cycle.
Lake Munson had a sandy bottom in the 1940s or 1950s and still has a sand layer under the sediment; however, dredging Lake Munson to pursue reclaiming a sandy bottom may well expose toxins and nutrients while also removing the healthy seed bank, an important component of the overall ecosystem. Seed banks are present in nearly all ecosystems and provide seeds for the redevelopment of plant communities in waterbodies, particularly wetlands and shallow lakes. Without vegetation to use the nutrients in the system, the lake will experience a massive algal bloom followed by an explosion of invasive exotic vegetation.
County staff will continue to engage the Workgroup and work toward the shared goal of improving Lake Munson and protecting and preserving the lake now and into the future.
Coordination and Public Engagement
State-agency partner coordination and public engagement are key to continued water quality and ecological health improvements at Lake Munson. Since the March 2023 update, County staff has coordinated with FWC on the status of the drawdown and vegetation in the lake. Quarterly updates were provided to the SAC at their May and July meetings. The September SAC meeting was cancelled due to Hurricane Idalia. Additional public engagement over the past six months includes two cleanup events and the launch of a Lake Munson website.
Cleanup Events
The drawdown exposed litter along the shoreline of Lake Munson and Lake Henrietta and presented an opportunity to educate and engage the public. On April 8, 2023, Leon County hosted a Lake Munson shoreline clean-up event with over 30 volunteers from the Boy Scouts of America Troop 23, Workgroup members, residents of adjacent neighborhoods, County employees, and elected officials. The shoreline cleanup removed 750 pounds of litter and demonstrated the County’s continued commitment to preserving our natural resources and water quality. Two weeks later, on April 22, 2023, the County hosted a Lake Henrietta cleanup event whereby over 70 community volunteers and elected officials collected more than 580 pounds of litter from the shorelines. Public Works Operations crews removed roughly 5 tons of litter and debris from the trash trap and water.
Lake Munson Website
In early August, Leon County launched a Lake Munson website that serves as an easy source for citizens to learn about the work and progress of Lake Munson including an outline of the Lake Munson Action Plan. The website provides an overview of the hundreds of millions of dollars invested into Lake Munson, an up-to-date status of the drawdown, a list of Frequently Asked Questions, and so much more. The website has an easy to remember dedicated link and can be found at www.LeonCountyWater.org/LakeMunson.
State Health-Related Studies
The Florida Department of Health (FDOH) is the lead agency to address the health effects of cyanobacteria algal blooms throughout the State. Studies are underway at four universities evaluating the prevention of toxic algal blooms, treatment for exposed individuals, health disparities related to the exposure of toxins, and better screening to quickly detect toxic blooms. Staff will continue to follow the progress of the studies and provide updates to the Board through future status updates on the drawdown.
Conclusion
This item provides a six-month status update on the implementation and ongoing efforts related to the drawdown of Lake Munson as part of the Lake Munson Action Plan. This item highlights the $290 million of investment through four decades including over 28 projects and 21 BMPs 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. The item also provides an update on the implementation of the Action Plan over the past six months, the enhanced monitoring data collected with a summary of the trends and observations, sediment management strategies implemented in other communities, a petition by the Workgroup calling for additional action at Lake Munson, and ongoing public outreach including the launch of a dedicated Lake Munson website.
Since the 1980s, $290 million has been invested to restore Lake Munson including infrastructure and restoration projects by Leon County, the City of Tallahassee, and Blueprint Intergovernmental Agency 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 was 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 Action Plan seeks to improve Lake Munson through a drawdown coupled with enhanced monitoring, while also providing long-term strategies to supplement the State’s ongoing in-lake vegetation management activities to deliver a higher level of service to County residents for a safe, sustainable, and healthy Lake Munson. 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 March 2023 status update, the extended drawdown and enhanced monitoring continued, monthly water quality data has been collected and analyzed, and County staff continue to monitor water elevations in Lake Munson and downstream. The bottom of the lake has filled with predominantly native and beneficial terrestrial plants that attracts birds such as turkeys and ducks, and are great for erosion control. Water quality sample results indicate the lake was likely in an unstable condition in March but sample results in subsequent months and the quarterly aerial topographic surveys indicate the lake bottom sediments continued to consolidate, and the system further stabilized. The point-source testing results for Munson Slough, downstream of the Lake, also indicates an unstable system in March with elevated lead and iron levels, followed by lower levels in subsequent months. Since March, the nutrient concentrations in Munson Slough below the lake have declined such that the July nitrogen concentrations and the August nitrogen and phosphorus concentrations are better than the State TMDL. In Munson Slough above the lake, the nutrient concentrations have remained lower than the target levels established in the State TMDL. Throughout the drawdown the water leaving Lake Munson has continued to meet the State’s Total Maximum Daily Load (TMDL) for nitrate for Wakulla Springs.
A review of sediment management strategies in other communities has continued over the past six months. Lake Munson remains a unique system and strategies that work in other areas are not necessarily best for Lake Munson. Dredging remains not viable in Lake Munson because it would result in resuspended sediment and contaminants, potentially contaminating drinking water, degrading aquatic and wildlife habitats, death of microorganisms and reduction of fish food source, neon green water from massive algal blooms due to no vegetation left in the lake followed by explosive invasive exotic vegetation with no remaining seed source, and underlying karst features with sinkhole potential. New and innovative technologies are continually developing and are reviewed by County staff and any opportunities will be presented to SAC and State agency partners for review. If the science changes and viable alternative lake management strategies emerge, the new opportunities will be brought to the Board for consideration.
On July 6, 2023 the Lake Munson Workgroup started an online petition calling for action from the Leon County and City of Tallahassee Commissioners to address eight concerns surrounding Lake Munson, primarily centered around the drawdown, dredging, and upstream point-source testing. While the County’s methods of restoration and vision for Lake Munson are different than those of the Workgroup, the ultimate goals of a healthy waterbody and ecosystem are fundamentally the same. County staff will continue to engage the Workgroup and work toward the shared goal of improving Lake Munson and protecting and preserving the lake now and into the future.
State-agency coordination and public engagement have continued throughout the past six-months with quarterly updates to the SAC and ongoing engagement with the Workgroup. Public engagement in Lake Munson included two cleanup events in April, one at Lake Munson and one at Lake Henrietta. For the combined events, over 100 volunteers removed over 1,330 pounds of litter from the shorelines and Public Works Operations crews removed roughly 5 tons of litter and debris from the Lake Henrietta trash trap and water.
Furthering public engagement, the launch of the Lake Munson website (www.LeonCountyWater.org/LakeMunson) serves as an easy source for citizens to learn about the work and progress of Lake Munson, including an outline of the Lake Munson Action Plan, an overview of the hundreds of millions of dollars invested into Lake Munson, an up-to-date status of the drawdown, a list of Frequently Asked Questions, and so much more.
Next Steps
The drawdown was temporarily suspended in advance of Hurricane Idalia to protect downstream properties from potential flooding and to protect downstream water quality by allowing any sediments in Lake Munson time to drop out and settle to the bottom. Staff will monitor the water levels downstream and the water in the lake to determine when it is appropriate to reopen the gates and resume the drawdown. In the next six-months, County staff will continue to work with State-agency partners to evaluate the benefits of the drawdown and will provide an update to the Board at the March 2024 meeting, in advance of the drawdown conclusion later that spring (2024).
County staff will continue to collect and evaluate the monthly water quality samples, including lead and iron, and the quarterly aerial topographic surveys with the information presented during the quarterly updates to the SAC. Coordination on the progress of the drawdown with State-agency partners and engagement with the Workgroup remain ongoing. Review of new and innovative lake management strategies and the status of the State’s study of health-related issues related to algal blooms will also continue. And finally, the Lake Munson webpage will be updated as new information or updates become available and staff will continue to provide six-months updates to the Board on the progress of Lake Munson throughout the extended drawdown and Enhanced Monitoring phase.
Options:
Recommendation:
Option #1
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