2

Restoration Progress

This committee is charged to discuss restoration accomplishments and assess “the progress toward achieving the natural system restoration goals of the Comprehensive Everglades Restoration Plan [CERP]” (see Chapter 1 for the statement of task and Appendix A for a discussion of restoration goals). In this chapter, the committee updates the National Academies’ previous assessments of CERP and related non-CERP restoration projects (NASEM, 2016, 2018, 2021, 2023; NRC, 2007, 2008, 2010, 2012, 2014). The committee also discusses programmatic and implementation progress and the ecosystem benefits resulting from the progress to date.

PROGRAMMATIC PROGRESS

To assess programmatic progress, the committee reviewed primary issues that influence CERP progress toward its overall goals of ecosystem restoration. These issues, described in the following sections, relate to project authorization, funding, and project scheduling.

Project Authorization

Once project planning is complete, CERP projects with costs exceeding $25 million must be individually authorized by Congress before they can receive federal appropriations. Water Resources Development Acts (WRDAs) have served as the mechanism to congressionally authorize U.S. Army Corps of Engineers

$413 million for the CERP,¹ and the FY 2025 President’s Budget includes a request for $444 million for this program (OMB, 2024). In FY 2024, the State of Florida budgeted $470 million for the CERP (State of Florida, 2023), and the governor has recently signed the budget for FY 2025 with $664 million for the CERP (State of Florida, 2024). Continuation of these record-high budgets will help sustain a rapid pace of project implementation, which will expedite natural system restoration progress.

Through FY 2023 the federal government and the State of Florida have each spent $2.6 billion on CERP planning and construction (USACE, 2023d). Current projections estimate that CERP completion will total $23.2 billion (in FY 2020 dollars; USACE and DOI, 2020), although future project authorizations and modifications may affect that estimated total.

Project Scheduling and Prioritization

The anticipated future progress of CERP projects and the relationships among all the federally funded South Florida ecosystem restoration projects and some

TABLE 2-1 CERP Project Implementation Status as of May 2024

NOTES: Does not include non-CERP foundation projects. NA = not applicable.

SOURCES: Data from NASEM, 2023; Parrott, 2024; USACE, 2023e; Velez, 2024; G. Ralph, USACE, personal communication, 2024.

TABLE 2-2 CERP Projects or Components That Have Not Been Addressed in Prior or Ongoing CERP Planning Initiatives as of June 2024

NOTES: Remaining unplanned CERP projects include all projects more than $5 million (2019 dollars) as reported in USACE and DOI (2020), for which the components have not been incorporated in other planning efforts or formally removed from the CERP. Letters in parentheses represent project component code from Yellow Book. Estimated financial requirement derived from SFERTF (2023).

SOURCES: Data from SFERTF, 2023; USACE, 2023e; USACE and DOI, 2020.

The discussions of restoration progress that follow are organized into four major sections based on implementation status.

1. Operating CERP projects (or project increments)
   • Picayune Strand Restoration Project
   • Melaleuca Eradication
   • CEPP New Water
   • C-111 Spreader Canal
   • BBCW
2. Regional operations plans
   • Kissimmee Headwaters Revitalization Schedule
   • Lake Okeechobee System Operating Manual (LOSOM)
   • Combined Operational Plan (COP)
3. Authorized CERP projects/components not yet operating (or constructed)
   • CEPP South, CEPP North, and the EAA Reservoir
   • C-43
   • IRL-South
   • Loxahatchee River Watershed
   • C-11 Impoundment
4. CERP projects in planning
   • Western Everglades Restoration Project (WERP)
   • Lake Okeechobee Watershed Restoration Project (LOWRP)
   • Biscayne Bay and Southeastern Everglades Ecosystem Restoration (BBSEER)

The committee’s previous report (NASEM, 2023) contains additional descriptions of the projects and progress through mid-2022. The South Florida Environmental Report (SFWMD, 2024a) and the 2023 Integrated Financial Plan (SFERTF, 2023) also provide detailed information about implementation and restoration progress.

CERP Projects with Recent Information on Restoration Benefits Delivered

The committee’s review in this section is based on reported monitoring data to date for CERP projects for which construction has begun, with emphasis on progress and new information gained during the past 2 years.

Picayune Strand Restoration Project

The Picayune Strand Restoration Project (Figure 2-2, No. 1) was the first CERP project under construction. The 55,000 acre (86 mi²) Picayune Strand area in southwest Florida was drained for an intended real estate development,

Golden Gate Estates-South, which was abandoned before completion. Construction of drainage canals and an extensive road network drained a large area of wetlands, reduced sheet flow to the south into the Ten Thousand Islands National Wildlife Refuge, and altered regional groundwater flow into surrounding areas (Figure 2-3). Restoring the predrainage hydrology should bring multiple

ecological and environmental benefits, including an increase in the spatial extent of wetlands, decreased frequency and intensity of forest fires, and increased habitat for endangered species such as the wood stork and Florida panther. The project is also expected to improve groundwater recharge to the City of Naples’ eastern Golden Gate well field, as well as coastal estuarine salinities affected by freshwater point discharges from the Faka Union Canal (RECOVER, 2019).

Project components include plugging drainage canals, degrading roads, and removing logging trams (Figure 2-4; USACE and SFWMD, 2004). Construction has

occurred in stages starting with the easternmost portion of the area and proceeding west (Figure 2-5, Table 2-3). The Eastern Stair-step canal was plugged in summer 2021, and 8.4 miles of the Faka Union Canal were plugged by May 2024. The Miller Canal, the westernmost canal, is scheduled to be plugged in late 2024 and 2025 after completion of the Southwest Protection Feature, a levee on the southwest edge of the project intended to reduce flood risk to the agricultural lands to the west of the project. Because of the staged plugging of drainage canals, the degree of hydrologic restoration varies both spatially and temporally. Prior to the 2019–2021 construction, only the northeast corner was considered to have full hydrologic restoration; as of May 2024, roughly half of the project footprint is considered to have full hydrologic restoration, with considerable additional hydrologic restoration expected by the end of 2025 (Figure 2-5).

Recent data on natural system restoration progress.

NASEM (2018, 2023) provided a comprehensive review of the hydrologic and vegetation monitoring program. Ongoing groundwater monitoring since release of the committee’s last report suggests that the area south of the Merritt Pump Station continues to show natural hydrological patterns, with target hydroperiods attained for cypress habitat (Figure 2-6). No additional vegetation data are being collected until 2025, with analysis expected in 2026. Thus, the remainder of this section focuses on information obtained during the past 2 years on invertebrate and vertebrate survey data in relation to hydrologic and vegetation outcomes from restoration efforts.

TABLE 2-3 Phases and Progress of the Picayune Strand Project

SOURCES: NASEM, 2023; data updates from M. Duever, consultant to the SFWMD, personal communication, 2024.

There is some early evidence that animal communities are responding to the changes in hydrology and vegetation enabled by restoration. In comparison to baseline data on the relative abundance and species diversity of aquatic macroinvertebrates collected in 2005–2007 (Bartoszek et al., 2007; Ceilley, 2008), macroinvertebrate assemblages by 2019 in some of Picayune Strand’s cypress habitats had started to exhibit shifts toward the species composition found in reference wetland communities. These shifts included an increase in species richness and recolonization of sites by longer hydroperiod (wetter) indicator species such as freshwater sponges, limpets, and crayfish (Ceilley et al., 2020). Additional monitoring in 2021–2022 revealed similar patterns, including evidence of further convergence of restored sites toward reference conditions since the 2019 macroinvertebrate sampling (Figures 2-7 and 2-8; Ceilley, 2022; Gaglia, 2022). Data on how fish and anuran (frogs and toads) communities are responding to restoration activities in Picayune Strand are limited compared to data on macroinvertebrates but yield important insights for future monitoring of

these taxonomic groups. As of 2019, the spatial extent of successful sampling remained constrained by short hydroperiod conditions not conducive to supporting fish. Moreover, Ceilley et al. (2020) reported abundant capture of the African jewelfish, a nonnative, invasive species, which may complicate the ability to track native fish community recovery. Anuran diversity and abundance surveys have thus far been limited to monitoring of artificial structures (i.e., PVC pipes that treefrogs use for shelter). The results have primarily yielded invasive treefrogs to date; more than 90 percent of frogs sampled from 2005 to 2019 in Picayune Strand have been Cuban treefrogs (Ceilley et al., 2020; Clark, 2020), obfuscating the ability to discern how native species are responding to restoration. Although this sampling technique has benefits such as ease of standardized, repeated sampling over time, it has several limitations. For example, only refuge-seeking species such as treefrogs typically utilize these artificial habitats, leaving the presence of other species (e.g., Ranid frogs) in the anuran community unknown. Adopting the use of automated audio recording technology (e.g., “frog loggers”;

De Solla et al., 2006; Dorcas et al., 2009; Measey et al., 2017; Stevens et al., 2002), with the possibility of employing artificial intelligence to support analyses of recordings (Gan et al., 2021; Lapp et al., 2021), would provide a more comprehensive assessment of the species of amphibians using restored habitats and might help to overcome possible sampling biases toward a single invasive species. Automated audio recordings offer the additional benefit of documenting broader changes to the soundscape in response to restoration activities. For example, ecoacoustics are increasingly used to document bird diversity and even underwater fauna (Desjonquères et al., 2020), as well as responses of ecosystems to restoration (Ramesh et al., 2023) and the invasion of nonnative species (Barney et al., 2024; Hopkins et al., 2022; Ribeiro et al., 2022).

The committee’s overall conclusion is that restoration of hydrology in the Picayune Strand Restoration Project appears to already be generating benefits to the local flora and fauna, with vegetation and macroinvertebrate communities responding favorably. Additional longitudinal monitoring will be needed to continue documentation of recovery, especially given the magnitude of seasonal and inter-annual variation. Sampling methods for some species (e.g., amphibians) need to evolve to generate a clearer picture of what species are responding to restored hydrology. Modern passive acoustics are one example of a sampling

In response to the projected adverse impacts on RCW habitat, the Project Delivery Team is proposing to leave a section of Miller Boulevard from 64th Avenue to 80th Avenue to act as a berm. This option does not require new features or significantly increase costs, nor is its implementation likely to delay construction (A. McKenzie, SFWMD, personal communication, 2024). Whether resolving this issue delays completion of the final stage of construction of the Picayune Strand Restoration Project instead depends on the length of time it takes to move the selected option through the approval process. This issue is discussed further in Chapter 5 in the context of adaptive management.

Melaleuca Eradication and Other Exotic Plants

CERP funds were used to construct the Biological Control Rearing Annex, adjacent to the U.S. Department of Agriculture’s Invasive Plant Research Laboratory (IPRL) in Davie, Florida, and CERP operational funding ($660,000 per year) supports biocontrol efforts for invasive plants in the Everglades (A. Dray, USDA, personal communication, 2024). The IPRL evaluates potential insect or fungal natural enemies in the native range of an invasive plant, obtains permits to export and import those species, raises them in quarantined conditions, evaluates how best to produce large numbers and release them to the wild, obtains permits for those releases, and then monitors the success of the releases. In general, biological control measures complement physical control measures (e.g., cutting or herbicide application) (Dray et al., 2023).

Five particularly problematic invasive plants that are the focus of recent and ongoing management and biocontrol in the South Florida ecosystem are listed in Table 2-4. Figure 2-10 shows recent information on the locations, numbers of release events, and numbers of released insects for two major biocontrol species. Melaleuca was once the most vigorously managed invasive plant, but integrated control measures, including biocontrol by a weevil, a sap-sucking psyllid, and a midge, have reduced the area dominated by Melaleuca by approximately 75 percent (Smith, 2022). In South Florida, Melaleuca control is considered to be in maintenance mode and is no longer targeted by active control methods except in areas where other invasive species are being controlled. The biological control agents drastically reduce establishment of seedlings except in persistently wet areas where the weevil—the most effective biocontrol agent—does not pupate (Smith, 2022). IPRL identified another midge species from the Melaleuca native range, the tip-galling midge, Lophodiplosis indentata, that was able to complete its life cycle in wet areas. Lophodiplosis indentata was granted a release permit in April 2022 and was introduced at one site in June 2023. A monitoring grid has been set up to confirm establishment of a field population and detect spread from the release site (Dray et al., 2023).

TABLE 2-4 Biocontrol Agent Rearing for Invasive Plant Species Control from 2019 to 2024

SOURCE: Data from Dray et al., 2022.

Brazilian pepper is one of the most invasive upland shrubs in Florida and is problematic elsewhere. It has been primarily controlled by chemical and mechanical means, but biocontrol is now provided by two insect species. The Brazilian pepper thrips, Pseudophilothrips ichini, was first released in July 2019 and is currently being mass reared and distributed. Monitoring has demonstrated that it has established persistent populations in the field and is spreading into new areas (Dray et al., 2023). A second species, a leaf galler (Calophya latiforceps), was approved for release in 2019 but as of 2022 has not been released because the rearing colony at IPRL was lost during the pandemic and has not yet been replaced by collecting new insects in Brazil (Cuda et al., 2023).

Water hyacinth is an extremely invasive aquatic nuisance. Control efforts using herbicides started in the 1940s. Frequent repeated herbicide sprays are required because water hyacinth rapidly regrows after being sprayed. Biocontrol was started in the 1970s in an attempt to provide more sustainable biological control (Goode et al., 2021). The three biocontrol insect species introduced in the 1970s effectively reduced biomass of water hyacinth but did not substantially reduce cover (Tipping et al., 2014), and immature stages were killed by herbicide use. Since 2007, IPRL has used CERP funding to identify biocontrol species that are less effected by herbicide use. The water hyacinth planthopper, Megamelus scutellaris, was released starting in 2010. In experimental conditions, the combination of biocontrol and herbicide use reduces water hyacinth biomass to zero or near-zero and reduces regrowth, which increases the time between required herbicide sprays (Tipping et al., 2017). Megamelus scutellaris is less effective in the field because dispersal of the planthopper makes it difficult to maintain high densities on water hyacinth plants.

The Old World Climbing Fern is one of the worst invasive plants in moist areas of central and southern Florida. First reported as naturalized in 1965, it spreads horizontally and vertically to form thick mats covering other vegetation.

It is a difficult plant to control because it is widespread, it covers large areas, and herbicide use is expensive. Two species, brown lygodium moth, Neomusotima conspurcatalis, and the lygodium mite, Floracarus perrepae, were released in 2008, but in the field, neither has a consistent effect on Lygodium spread (Walker et al., 2024). The brown lygodium moth is no longer being reared and released because of disease issues and labor-intensive maintenance (Dray et al., 2023). IPRL is evaluating the suitability of additional natural enemies as biocontrol agents (Walker et al., 2024).

The air potato vine is invasive across the southeastern United States. Like the Old World Climbing Fern, it spreads horizontally and vertically and covers extant vegetation. Large-scale field releases of a beetle, Lilioceris cheni, started in 2012 (Rayamajhi et al., 2019) and continued until 2019. Field monitoring shows that greater than 90 percent of air potato vines are damaged by L. cheni and vegetative reproduction is greatly reduced, to the extent that additional releases and herbicidal measures are not needed. The plant is no longer considered a priority invasive species by land managers (Overholt et al., 2016; Rayamajhi et al., 2019). Rearing and release of L. cheni was terminated in 2022 (Dray et al., 2021).

Evaluating the success of biocontrol measures is complicated because biocontrol has the potential to impact large areas but usually has a chronic, not an acute, effect that acts over long time frames. Current species-specific monitoring has focused on assessing population persistence in and dispersal from introduction sites (Dray et al., 2022). There are examples of substantial impact in limited areas (Figure 2-11), but landscape-scale effects are more difficult to monitor. In general, biocontrol has generally been viewed as a success for Melaleuca and air potato vine but has been less effective for other species for various reasons.

Vegetation mapping using remote sensing is the best way to assess large-scale effects of invasive species management, using trained staff to identify species-specific signatures in remote-sensed imagery. The recently completed vegetation map of Everglades National Park, using color-infrared aerial photography taken in 2009 (Ruiz et al., 2021), includes maps of locations and cover of Brazilian pepper, Melaleuca, and Lygodium, although Lygodium was difficult to detect. Because these maps are based on aerial photography, they only show areas where an invasive species is apparent in the canopy, but they provide a baseline landscape-scale assessment. An updated vegetation map based on more recent imagery would provide a useful means to assess large-scale progress in the control of invasive plants in the Everglades.

Central Everglades Planning Project

The CEPP is the keystone project in the restoration of the central heart of the Everglades. It will provide the means to send additional water south through

the Water Conservation Areas (WCAs) and Everglades National Park to Florida Bay, reduce harmful discharges to the northern estuaries, and improve the timing and distribution of flow in the central Everglades (USACE, 2024a). The CEPP continues to progress at the rapid pace that has characterized it throughout its development, authorization, and implementation (NRC, 2014). The CEPP is a complex project with four phases, each with multiple components: CEPP South, CEPP North, CEPP New Water, and CEPP EAA. Its many parts include improvements in seepage management; improvements in conveyance through filling of canals, levee removal, and addition of new structures such as pump stations and

C-111 Spreader Canal Western Project

The C-111 Canal, originally designed to provide flood protection in Dade County, spurred agricultural development on lands to the east while draining water from the Southern Glades and Taylor Slough in Everglades National Park. A principal source of the freshwater in the canal is seepage from Everglades

project component—the S-198 Spillway (Figure 2-15)—is currently on hold. The SFWMD reports that it “may be implemented” if it is “anticipated to increase restoration and can be implemented without adversely impacting pre-project levels of flood protection” (Gottlieb et al., 2024); it remains unclear whether it will be constructed, because it is not included in the next 10-year schedule in the 2023 IDS (USACE, 2023e).

The C-111 Spreader Canal Western project pumps excess water from the canal into the 600-acre Frog Pond Detention Area and into the Aerojet Canal impoundment (Figure 2-15), thereby creating a 6-mile hydraulic ridge along the eastern boundary of Everglades National Park to reduce seepage from the park and improve the hydrologic conditions of Taylor Slough. Rather than a persistent feature, the hydraulic ridge is present and functions only when water is available to fill the detention area. The project is also intended to contribute to improved distribution of flows in the Southern Glades through emplacement of earthen plugs along the C-110 Canal and through modified operations of structures located principally along the southern segment of the C-111 Canal.

Annual SFWMD reports show prior year data on flow and stages (e.g., Gottlieb et al., 2024), but no recent long-term analysis is available on the hydrological or ecological outcomes of the project relative to expectations or baseline conditions. Gottlieb et al. (2024) report, “Within Taylor Slough, dry-season water levels have risen, and dry season tidal creek flows have increased” since operations began, although the data analysis is not presented. Given the overlap in downstream footprint of the project with other CERP and non-CERP projects, the SFWMD concluded that potential interactions will make it difficult to tease out specific direct benefits of the project (Gottlieb et al., 2024). The project features are operated as part of the COP, which outlines the integrated operations of CERP and non-CERP projects in the region. The benefits of the COP are discussed later in this section.

Biscayne Bay Coastal Wetlands, Phase 1

Historically, Biscayne Bay received freshwater from overland flow passing through the coastal ridge and wetlands, and from extensive groundwater seepage. As a consequence of historical hydrologic alteration and development, freshwater delivery to Biscayne Bay has been greatly reduced, particularly in the dry season, resulting in loss of wetlands and an increase in salinity along the western margin of the bay. At the same time, controlled freshwater pulse discharges as point sources create altered flow, salinity, and nutrient inputs into the bay. Freshwater wetlands in the Southern Everglades have been reduced in area, altered, and degraded because of water management practices, land development, and sea-level rise, and much of the Model Lands, Southern Glades, and South Dade Wetlands are drained. These factors have contributed to landward

the canal stage high enough (stage target level is 2.2 feet National Geodetic Vertical Datum [NGVD]) to promote outflow through the culverts. The USACE is expected to finish construction of the L-31E Flow-way component in 2025, which will include a total of five pump stations (USACE, 2023e).

Several coastal wetland vegetation transects downstream from the L-31E culverts were sampled in 2022 and 2023. All transects remained dominated by a mangrove overstory, and a large decrease in mangrove with freshwater inflows has not been observed. New establishment of herbaceous species was limited and largely consisted of salt-tolerant species. The presence or increase of other freshwater species such as sawgrass outside of a few meters of established culverts was not observed (Charkhian, 2024). Charkhian (2024) stated,

Regional Operations Plans

Kissimmee River Headwaters Revitalization Schedule

The Kissimmee Basin includes more than two dozen lakes in the Kissimmee Chain of Lakes, their tributary streams and associated marshes, and the Kissimmee River and floodplain (Figure 2-17). The Kissimmee River Restoration Project was authorized in 1992 with the goal of restoring more than 40 mi² (or one-third) of the river-floodplain ecosystem and 44 miles of the river channel. Project features, which included backfilling 22 miles of the C-38 Canal, removing water control structures, and reconnecting remnant river segments, were completed in 2021, setting the stage for implementation of the new Headwaters Revitalization Schedule, which is beginning phased implementation in 2024.

Once fully implemented, anticipated in 2026, the new stage regulation schedule for the S-65 water control structure will allow water levels to rise up to 1.5 feet higher than the current S-65 schedule and will increase the water storage capacity of the Upper Kissimmee Basin by approximately 100,000 AF (Koebel et al., 2024). This increased capacity will allow releases to more closely approximate the historic flows needed for restoration of the Kissimmee River and its floodplain wetlands and is also expected to improve littoral zone conditions in Headwaters Lakes.

The ultimate goal of hydrologic restoration for the entire Kissimmee River is to restore the single, continuous floodplain inundation event that occurred

most years prior to channelization that typically began late in the wet season, continued well into the dry season, and extended throughout all seasons in some years. Floodplain inundation supported wetland vegetation along the Kissimmee River floodplain and provided important foraging habitat for wading birds and waterfowl and nursery areas for native fish. Modeling results project that floodplain inundation will improve with the 1,400-cfs discharge plans while also improving conditions to the Headwaters Lakes (Koebel et al., 2024).

Lake Okeechobee System Operating Manual

Management of Lake Okeechobee is challenged by its fast inputs and limited managed outflow, allowing high precipitation events to raise water levels quickly. Prolonged high-water levels result in the loss of submerged aquatic vegetation (SAV) in the littoral zone (because of low light transmissivity) and extreme high-water levels can pose dike safety issues, thereby requiring releases to the northern estuaries. These releases alter salinity and increase turbidity and nutrient loads, which can negatively affect SAV in the estuaries and exacerbate harmful algal blooms. In contrast, extended periods of low precipitation can lower water levels in the lake, leading to expansion of invasive species in the littoral zone and threats to water supply deliveries to utilities, agricultural producers, and residential populations (see NASEM, 2018, for in depth discussions of Lake Okeechobee and the northern estuaries).

In 2022, after extended stakeholder input, the USACE released a draft of LOSOM as the updated plan to manage the water levels in the lake after completion of the Herbert Hoover Dike rehabilitation efforts (USACE, 2022b). Zone D of the proposed operating schedule provided considerable flexibility compared to previous plans as to when to hold or release water from the lake, but with this flexibility comes uncertainty regarding the criteria for operational decisions within Zone D (Figure 2-18). LOSOM also resulted in substantially less water storage (between 460,000 and 800,000 AF) compared to the operations in place when the CERP was originally designed (for more information, see NASEM, 2023). Implementation of LOSOM was scheduled for March 2023 but was delayed pending final agency review after recent consultation and a biological opinion from the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service (NMFS, 2023).

The LOSOM Final Environmental Impact Statement (EIS; USACE, 2024b) was published in May 2024. The EIS reemphasizes the USACE operational strategy to balance the needs of managing flood risk, water supply, navigation, recreation, and the ecological health of fish and wildlife. The committee acknowledges the greater flexibility in LOSOM to make releases to improve water supply and enhance fish and wildlife, as well as use whole-system behavior to make

real-time decisions, because of the latitude in Zone D. NASEM (2023) recommended that the USACE implement a process for periodic multi-stakeholder review of Lake Okeechobee operations relative to the objectives of LOSOM to build confidence that the flexibility of the new operational schedule is being used as designed and to support learning to enhance future decision making. USACE (2024b) noted that it plans to hold three seasonal periodic scientist call meetings per year for agency and stakeholder communication and input.

The Combined Operational Plan

The COP is a comprehensive, integrated water control plan that defines the operations of the constructed features of the Modified Water Deliveries to Everglades National Park (Mod Waters) and C-111 South Dade projects (Figure 2-13) and other water management structures in the region. These non-CERP projects whose capabilities it incorporates are considered foundation projects for the CERP because they alter the delivery and flow of existing water in ways that are critical to the CERP’s capacity to deliver additional flow volumes and restoration benefits. In addition, completion of Mod Waters and its operations plan was required before federal funding could be appropriated to begin construction of the CEPP. Therefore, the implementation of the COP marks not only the largest step by far toward restoring the hydrology and ecology of the central Everglades yet achieved but also the beginning of the next phase of the restoration of the heart of the Everglades embodied in the CEPP.

Two features of Mod Waters and other related projects are especially critical to the capacity of the COP to make significant changes to the hydrology of the central Everglades. First, raising the Tamiami Trail and bridging extensive portions of it enables increased flows into Northeast Shark River Slough and Everglades National Park, and much more as sheet flow (Box 2-1). Second, seepage management and flood mitigation features along the eastern boundary of Everglades National Park (Figure 2-13) reduced flood risk management constraints that limited flows into Northeast Shark River Slough. The C-111 South Dade Project improved seepage management along the eastern boundary of Everglades National Park further south, enabling more flow through Taylor Slough to Florida Bay, while continuing to honor flood risk management constraints for the agricultural lands east of the park (USACE, 2022c). The C-111 Spreader Canal Western project extends this hydraulic ridge southward, providing additional restoration benefits to Taylor Slough.

The ongoing ecological degradation of the central Everglades (see NRC, 2012 for a review) has long been a major concern motivating restoration efforts, and management of water in this area is a source of controversy. The COP is the latest in a series of water management plans that attempts to address the issues in this region. The development of the COP was informed by data gathered during a period of incremental operational testing, beginning in 2015. Thus, the hydrologic and ecological changes discussed in this section reflect incremental operational changes from 2015 to 2020 and full implementation of the COP in September 2020, which were made possible by the new infrastructure available from the Mod Waters, C-111 South Dade, and Tamiami Trail Next Steps projects.

A comprehensive assessment of observed COP benefits can be found in the COP Biennial Report (USACE et al., 2023a), which summarizes COP operations,

BOX 2-1
Tamiami Trail Next Steps Project

The 10.7 miles of the Tamiami Trail between the L-31N and L-67 extension levees have been an impediment to surface flow from WCA-3 into Northeast Shark River Slough located in Everglades National Park since the completion of this highway in 1928. Reducing the impact of this barrier has been an important component of the restoration. The Modified Water Deliveries Project created a 1-mile bridge, completed in 2013, near the eastern end of this portion of the Trail. Phase 1 of the Tamiami Trail Next Steps project, completed in 2019, addressed an additional 2.6 miles of highway with 2.3 miles of bridging at the western end of the 10.7 miles of the Trail (Figure 2-19). The Tamiami Trail Next Steps Phase 2 project will reduce the impact of the remaining 6.7 miles of highway on sheet flow through the addition of six new 60-foot-wide slab bridges, improvements to seven culverts, and raising of the highway in unbridged segments. Phase 2 construction began in 2021 and is projected to be completed in 2026 (USACE, 2023e). With the completion of this project, the entire 10.7 miles of the Trail will have been modified, which will enable raising of the maximum water level in the L-29 Canal to 9.7 feet to accommodate the CEPP, which will have a profound effect on capacity to manage water moving through WCA-3 into Everglades National Park. At that time managers anticipate implementing a new water management plan (CEPP 1.0) that will replace the COP and that incorporates these new features.

---

the USACE decision-making rationale for any deviations, and the hydrologic and ecosystem status for the period September 1, 2020, through April 30, 2022. The COP Biennial Report seeks to address whether the plan is achieving its objectives and whether adjustments are recommended. The report also evaluates the adaptive management uncertainties identified in the design of the COP based on recent monitoring results.

Hydrologic responses.

The COP Biennial Report (USACE et al., 2023a) presents an analysis of the hydrologic performance of the COP, employing the performance metrics used in the development of the COP as a reporting and evaluation framework. Monitoring results from before and after COP implementation and simulated COP performance from the Regional Simulation Model for the Glades and Lower East Coast Service Areas (RSM-GL) are compared. This comparison enables assessment of actual COP performance relative to the expectations based on modeling, and thus provides insight on the predictive performance of the modeling in terms of recent historical conditions (termed baseline, WY 2002–2015), which sheds light on the actual improvements achieved on the ground. Although encompassing only approximately 2 years of full COP operations, the report includes both a wet (WY 2021) and dry water year (WY 2022), signaling some early hints at COP performance. The biennial reports will be increasingly informative and important as the period of COP implementation lengthens.

For the current report period, the hydrologic results have been consistent with or better than the expectations based on model simulations and better than historical conditions. Even in the dry year of WY 2022, the water deliveries across Tamiami Trail were well above the typical deliveries prior to 2016 (note that the period after 2016 and prior to the COP consisted of incremental field testing of the Mod Waters features and emergency deviations and is less useful for comparisons) (USACE et al., 2023a). As the committee noted previously, the COP has been remarkably successful so far in not only increasing water deliveries across Tamiami Trail, particularly during the dry season (Figure 2-20), but also restoring the historical distribution of those flows between Western and Northeastern Shark River Slough (Figure 2-21; NASEM, 2023).

Water deliveries to Taylor Slough have also shown improvements from COP implementation to date. The longer hydroperiods have been observed relative to the pre-2016 baseline for most of the Everglades National Park region and especially in Northeastern Shark River Slough, Taylor Slough, and the western and eastern marl prairies. Again, the results compare well with the modeled expectations and generally show improvement relative to the historical baseline. Dry days and risk of soil oxidation within Everglades National Park have been reduced under the COP relative to the baselines even in the dry year, although risk of soil oxidation increased as was anticipated in north-central WCA-3A. In terms of increases in freshwater flows to Florida Bay, the results are modest and reflect the need for additional projects to come online before improvements can be expected there (USACE et al., 2023a). Overall, the early hydrologic results from the COP are promising and provide confidence in the modeling, coordination, and evaluation process used to produce it.

Ecological responses.

To assess ecological performance, the COP Biennial Report (USACE et al., 2023a) employs a similar process as that used to assess hydrological performance. Of the four ecological performance measures monitored—freshwater fish, tree islands, wood stork and wading bird nesting, and slough vegetation—there are, as yet, too few data to definitively assess COP performance for freshwater fish and tree islands. For wood stork and wading bird nesting (see also below), the variation in rainfall over the period of review was deemed too large to evaluate the impact of the COP (USACE et al., 2023a). The fourth performance measure, slough vegetation, however, is highly informative. Coincident with increased hydroperiods in Northeastern Shark River Slough under the incremental field testing and the COP, long hydroperiod species such as sawgrass and slough species such as Eleocharis are expanding (USACE et al., 2023a). Nocentini et al. (2024) further document this pattern, including transitions to wetter plant communities along the gradient from dry marl prairie to beaksedge (Rhynchospora tracyi) marsh to sawgrass marsh to slough communities, as well as loss of marl prairie species. These results indicate that a predicted ecological benefit of the COP is being achieved.

Additional ecological monitoring associated with the COP addresses impacts on threatened and endangered species (see Table 2-5 for the committee’s summary of results of monitoring for the Cape Sable seaside sparrow [Ammodramus maritimus mirabilis], Everglade snail kite [Rostrhamus sociabilis plumbeus], and wood storks [Mycteria americana]) related not only to performance measures but also to criteria for incidental take, exceedances of which could require reinitiating consultation with the FWS over COP operations.² The prior period

TABLE 2-5 Committee Assessment of COP Effects on Threatened and Endangered Species Relative to 2016–2020 Conditions

NOTES: Three types of measure are included: criteria for incidental take (Take), performance measures (PM), and hydrological parameters indicating potential for incidental take of Cape Sable seaside sparrows (Parameter). Results are shown for the incremental testing baseline period (baseline performance) and for full COP operations (COP performance) and summarized in Assessment.

SOURCES: Data from USACE, 2023f, 2023g; USACE et al., 2023a.

of incremental testing (2016–2020) was used as the baseline for comparisons to COP performance (2021–2023), limiting the ability to assess the full benefits of the COP relative to previous management plans (NASEM, 2021). No comparisons to a baseline have been made for performance measures for threatened and endangered species; performance is instead assessed in terms of success in meeting targets.

The monitoring results summarized in Table 2-5 highlight the challenges that the COP faces in meeting precise, complex targets over extended periods, such as water levels and especially recession rates during the nesting season for snail kites and wood storks. The COP and the infrastructure it employs likely lack the capacity to adjust sufficiently to achieve such precise goals under all rainfall regimes, a conclusion evidently reached by FWS in its decision not to reinitiate consultation in response to exceedance of incidental take of snail kites based on recession rates (Table 2-5). Impacts on wood storks and snail kites were not expected to be sufficiently adverse to result in constraints on operations, and no constraints have been placed on operations. For these two species, performance related to incidental take criteria, as anticipated, has instead improved under the COP relative to the 2016–2020 baseline, with the exception of the recession rate criterion for kites.

Results for the Cape Sable seaside sparrow present a very different picture. Simulations of COP performance predicted that the hydrologic targets for the sparrow will not be met (USACE, 2020a), and monitoring confirms this prediction. If anything, performance has declined under the COP relative to baseline (Table 2-5). The evidence is abundant that the COP is reducing short hydroperiod wetlands (see above; see also NASEM, 2023). That the acres of short hydroperiod wetlands within the core foraging areas of stork colonies experiencing long hydroperiods exceeded the target by an order of magnitude in each of the first 2 years of the COP (USACE, 2023g) adds to this evidence. Because of these changes, sparrows are losing habitat in the areas they currently occupy, and to date, they have not colonized new suitable habitat created by the COP. Data as of July 2024 indicate that their estimated population size has fallen below the threshold for incidental take (2,387 sparrows) (M. Meyer, FWS, personal communication, 2024). The future of the sparrow under the COP and subsequently the CEPP is an issue that requires creative solutions, sooner rather than later.

Water quality responses.

The 2023 COP Biennial Report highlighted ongoing water quality concerns, noting an exceedance in the 12-month average phosphorus concentration for inflows to Shark River Slough during WY 2019. Since then, exceedances have occurred in WY 2021–2023 (Qiu, 2024a,b).

Uncertainty #16b in the COP adaptive management plan (USACE, 2020a) specifically addressed water quality changes due to COP operations:

During the reporting period, monitoring data were analyzed to investigate the potential to reduce concentrations by shifting flows from the S-333 structure to the S-333N structure and/or making adjustments to the S-12 structures, but the analysis showed that such changes would not reduce total phosphorus (TP) concentrations. Concerns were raised about water quality resulting from S-333 operations, but during the COP biennial reporting period, management options were not implemented. Water quality issues associated with increased restoration flows are discussed in more detail later in the chapter.

Summary of COP results.

The initial monitoring results indicate that the COP has met expectations in changing the quantity, distribution, and seasonal patterns of flow and improved conditions relative to the baseline period. Initial results also indicate that these hydrologic changes are producing some of the predicted broader ecological responses that are COP objectives, as illustrated by changes in plant communities and risk of soil oxidation. The COP has achieved much less success with more complex objectives that involve creating fairly precise hydrologic conditions over extended periods of time, as illustrated by recession rates and water levels during the nesting season for threatened and endangered species. Thus, the COP is proving to be what it was intended to be—not a complete solution but rather the first major step toward restoring the central heart of the Everglades. Additional efforts will likely be needed to sustain the Cape Sable seaside sparrow, including but not limited to translocation. The first COP Biennial Report is an effective means of conveying progress toward restoration that should be emulated through the remaining years of the COP and beyond.

CEPP 1.0 operational plan.

Lessons learned from the COP can be applied to the next system operating plan, CEPP 1.0, which is currently in planning to adapt operations to recently completed or soon-to-be-completed CERP features. CEPP 1.0 will incorporate CEPP components scheduled for completion by 2025, including CEPP New Water and several CEPP South features.³ Several non-CERP projects will also be included for the development of this regional operations

plan, including the Tamiami Trail Next Steps Phase 2 project (Box 2-1), the 2.3-mile seepage barrier adjacent to the 8.5 Square Mile Area constructed by the SFWMD, the 5.0-mile CEPP New Water seepage barrier (Figure 2-13), and LOSOM (Figure 2-18). Crucially, CEPP 1.0 will raise the constraint on water levels in the L-29 Canal from 8.5 up to 9.7 feet, enabling movement of even higher flows of freshwater through the central Everglades and into Everglades National Park. Thus, CEPP 1.0 represents a major increment in the restoration of historic flow volumes and distribution beyond that achieved by the COP. Currently alternatives are being developed and compared, with the expectation that CEPP 1.0 will be implemented in 2026 (USACE and SFWMD, 2024).

Authorized CERP Projects Not Yet Constructed or Fully Operating

Six CERP projects are actively under construction, of which four—the C-43 Reservoir, IRL-South, the C-11 Impoundment, and the CEPP (including CEPP South, CEPP North, and CEPP EAA)—are too early in their construction to have documented restoration benefits. Additionally, the Loxahatchee River Watershed project has been authorized, but construction has not yet begun. These projects are described briefly here to understand the context of implementation progress.

C-43 Reservoir

Early in the 20th century, the course of the Caloosahatchee River was deepened and straightened, and canals were excavated in the river basin that connected the river to Lake Okeechobee and drained agricultural lands and urban areas. As a result, during prolonged dry periods, freshwater flow to the estuary is greatly reduced, and saline water can migrate far up the river, killing beds of freshwater submerged plants. Conversely, during periods of heavy rainfall, large volumes of nutrient- and sediment-rich freshwater are transported into the Caloosahatchee River estuary, affecting habitat quality for seagrasses, oysters, and other aquatic organisms. The Caloosahatchee River (C-43) West Basin Storage Reservoir (Figure 2-2, No. 8) is a CERP project designed to impound up to 170,000 AF of stormwater runoff from the C-43 drainage basin or from Lake Okeechobee during wet periods (USACE and SFWMD, 2010), hence protecting the estuary from excessive freshwater. During dry periods, this stored water can be released to supplement low river flows to maintain optimal salinity levels in the estuary. Additionally, the SFWMD is planning to construct a non-CERP in-reservoir alum treatment system to reduce phosphorus loading to the Caloosahatchee River estuary to address concerns that storage of high phosphorus water in the reservoir could contribute to algal blooms (J-Tech, 2020). Reservoir construction has been delayed by the need to replace the contractor (A.B. Williams, 2023),

near the feature, thereby enhancing municipal and agricultural water supply and reducing saltwater intrusion (USACE and SFWMD, 2012). This feature was listed as a dependency for CEPP construction in USACE and SFWMD (2014). Construction began in 2017 on an initial Mitigation Area A berm, and a new contract award for continued construction is expected in September 2024 (G. Ralph, USACE, personal communication, 2024). No natural system restoration benefits are expected from construction to date.

CEPP North

CEPP North (Figure 2-2, No. 10) is designed to improve the distribution of flows into northern WCA-3, which has long been subject to overly dry

by a subgroup of the South Florida Ecosystem Restoration Task Force (Task Force) formed in response to concerns raised by the Seminole Tribe about lack of restoration progress in the western Everglades.

The planning process has been challenging. The initial preferred alternative—Alternative H (Alt-H)— was deemed not cost-effective. The high project costs, together with unmet need for an extensive real estate takings analysis, led to the suspension of WERP planning in 2019. Through strong stakeholder support, the planning was restarted and the project re-scoped, resulting in the Hybrid Revised Alternative (Alt-Hr), which included two STAs that were to cover nearly 7,500 acres and treat runoff entering the northern portion of the project area. Stakeholder objections to the placement of one STA in an area of remnant cypress led to further project revisions. Alternative Hybrid Natural Flow Revised (Alt-HNFR) was ultimately identified as the tentatively selected plan, and the draft PIR was released in December 2023 (USACE and SFWMD, 2023a). The recommended WERP plan is shown in Figure 2-24, although as of August 2024, the final draft PIR was not publicly available. Therefore, the following information is largely derived from the December 2023 draft PIR.

Within the northern portions of the recommended plan (Figure 2-24), several canals will be modified, and a variety of other structures including a weir, spreader canals, and culverts are designed to direct flows into the Seminole Big Cypress Reserve Native Area—an area of great cultural importance to the Seminole Tribe—and the Big Cypress National Preserve to rehydrate these areas. Better hydration in the Big Cypress National Preserve will help reduce the risk and severity of wildfires in the preserve. Further work is planned to restore vegetation in WCA-3A in an area currently dominated by cattail due to water quality impacts near the intersection of the L-28i and L-28N, within the Miccosukee Alligator Alley Reservation. The recommended plan (Figure 2-24) includes one STA to provide treatment for flows from the North Feeder subbasin and areas within the C-139 annex basin, with the objective of improving water quality conditions in the L-28N Canal. Water quality concerns in the West Feeder Basin (where an STA was eliminated in Alt-HNFR) will be addressed using a source-control approach through non-CERP components. Natural removal processes within the Kissimmee Billie Slough are also expected to reduce phosphorus concentrations. Upstream phosphorus levels must be addressed so that WERP does “not cause or contribute to water quality violations in Big Cypress National Preserve, the Seminole Tribe of Florida Reservation or other areas as determined by the regulatory agencies” (USACE and SFWMD, 2023a).

In the southern portion of the project area, portions of the L-28 Tieback and L-28S Canals will be filled; gated control structures will be built on L-28S to increase exchange between Big Cypress and WCA-3A; and culverts will be added beneath 11-Mile Road, US-41, and the Loop Road to enhance hydrologic

connectivity and flows to the southwest, while protecting Tribal tree islands and camps. Overall, WERP features, if implemented as planned, should improve hydration, hydrologic and ecological connectivity, and water quality, which have been longstanding concerns in the WERP study area. The WERP Project Delivery Team has targeted September 2024 for a Chief’s Report, with the goal of authorization in WRDA 2024 (Velez, 2024).

The Adaptive Management Plan for WERP (Annex D of USACE and SFWMD, 2023a) identifies nine key uncertainties, monitoring plans, trigger points and or thresholds for management action, and potential management actions (see also Chapter 5). Continuous monitoring and assessment will enable a comparison between what is expected and actual system response, and in turn support an iterative process to guide subsequent management decisions and any needed improvements or adjustment to the current plan. In this regard, it is important that the WERP project team works closely with Miccosukee and Seminole Tribes to continue to refine performance measures and targets/trigger points based on Indigenous Knowledge (see also Chapter 3).

Water quality and WERP implementation dependencies.

The 2023 Draft PIR (USACE and SFWMD, 2023a) states that implementation of WERP and its project dependencies will occur in stages over approximately 10 years following authorization, starting with implementation of non-CERP best management practices (BMPs) on privately owned lands in contributing areas. The timely implementation of several WERP features, including modification of the Lard Can and Wingate Mill Canals, backfilling the L-28i and L-28i extension canals, and construction of the L-28i weir and plug, depends on achievement of water quality objectives. In the draft PIR, a “numeric planning placeholder” of 17 μg/L TP was used “for the area influenced by the WERP . . . West Feeder Project components,” assessed areawide as an annual geometric mean that must be met at least 2 of every 3 years. The PIR estimates that concentrations of 31–34 μg/L TP at the West Weir (Figure 2-24) would be sufficient to reach this 17 μg/L TP placeholder target in Big Cypress National Preserve, although additional studies are ongoing to establish baseline conditions, investigate appropriate targets, and determine the probable natural treatment likely to be afforded as the water travels through Kissimmee Billie Slough. By comparison, annual flow-weighted mean TP concentrations over the past 10 years at the West Weir have generally ranged between 40 μg/L and 90 μg/L (Figure 2-25; Wang and Mahmoudi, 2024). The proposed implementation schedule estimates a 7-year time frame for non-CERP water quality initiatives to meet these levels (USACE and SFWMD, 2023a).

In essence, much of the implementation of WERP features depends upon achievement of water quality objectives, with a 3- to 7-year time frame for non-WERP efforts to achieve their objectives before WERP implementation is delayed,

depending on the WERP feature in question. An inherent assumption of this component is that BMP implementation will be accomplished as envisioned and as scheduled. Julian and Davis (2024) show potential reductions of 25-51 percent in flow-weighted mean TP concentrations associated with BMP implementation in the region compared to up to 73 percent reduction if an STA were included. However, the effectiveness of BMPs can vary substantially based on a variety of factors and with time (Ator et al., 2020; Gitau et al., 2005). Furthermore, BMP implementation often relies on a voluntary process, although Florida has regulatory processes that could be implemented if necessary. Initial voluntary and regulatory efforts will be reviewed approximately 3 years into the project with the plan to refine existing source control projects, initiate new projects, and/or move toward mandatory source control, if needed. A mandatory state source control program would incorporate water quality monitoring, data collection and analysis protocols, and compliance inspection, in addition to BMP selection, and its development is expected to take 3 to 5 years. Because of this dependence on the BMP component, there is the need to closely monitor BMP implementation and functionality, and consider alternate solutions as needed, to ensure timely WERP implementation.

Operation of gated culvert S-223 on Kissimmee Billie Slough.

As part of WERP features in Region 2 (Figure 2-24), a 180-cfs culvert (S-223) will be constructed and used to direct and control flows from the Kissimmee Billie Slough into the Seminole Big Cypress Reservation Native Area. The Seminole Tribe requested inclusion of gates in this structure, as well as to control structure operations using Indigenous Knowledge (Osceola, 2022; see also Chapter 3). Osceola (2022) explained:

Thus, the success of this part of this part of WERP will depend on water quality in the Western Basin. The WERP adaptive management plan includes a review of gate operations if the desired conditions are not met considering prevailing gate operations.⁴

Other issues that may impact progress.

There is concern that WERP-related increases in water levels will negatively impact areas occupied by endangered and threatened species, particularly the Florida panther (Puma concolor coryl). Although it historically occupied a vast area of the southern United States, stretching from Arkansas to the Carolinas, the panther now only exists as a single breeding/reproductive population, located south of the Caloosahatchee River. However, there has been recent documentation of panther activity north of the Caloosahatchee River, which could potentially signify population expansion north of the river (FWS, 2020). According to the draft PIR (USACE and SFWMD, 2023a), the North Feeder STA (Figure 2-24) will increase water levels in areas that are important to the Florida panther, including currently occupied areas and contiguous areas necessary for its long-term viability and persistence. The USACE Biological Assessment included in the draft PIR concluded that the project will not intersect any travel corridors and will, thus, not limit panther movement between areas south and north of the Caloosahatchee River. The 2024 Biological Opinion (FWS, 2024) outlined a plan for the USACE to use habitat units from the CERP Picayune Strand Panther Conservation Bank to offset losses due to the North Feeder STA with an anticipated 24,831 units needed. Concerns have also been raised about potential impacts on the panther’s primary prey, the white-tailed deer (Odocoileus virginianus) (FWS, 2020), whose survival is greatly impacted by water levels in the wet prairies (Bled et al., 2022;

MacDonald-Beyers and Labisky, 2005). MacDonald-Beyers and Labisky (2005) recommend that water rise no higher than 0.5 m (1.6 ft) to reduce deer mortality and improve its viability. Expected water levels fall within this recommended threshold. Analyses in the Biological Assessment (USACE and SFWMD, 2023a, Annex A) show that concerns about potential water level increases in the Wingate Mill and Lard Can Canal areas due to proposed canal modifications have been alleviated, and no adverse impacts are expected to the Florida Panther Conservation Bank as a result of WERP.

Risk of increased flooding due to WERP has been identified in the Feeder Canal and L-28 Gap basins. The Savings Clause (WRDA 2000, Section 601) requires that CERP projects maintain existing levels of flood protection (relative to time of CERP enactment) or work with affected landowners to mitigate the impacts of flooding. For western areas along L-28i, upstream of canal modifications, simulated ponding depths show an up to 70 percent probability of exceedance in wet years attributable to WERP. Model results suggest increased risk of flooding in areas immediately west of L-28i, including the Looneyville community (USACE and SFWMD, 2023a). Unless the plan is modified, this increase in flooding would necessitate solutions such as the raising of structures, perpetual flowage easements, or land acquisitions for impacted privately owned properties. More localized assessments will be conducted in the pre-construction engineering and design phase to better delineate areas and structures that might be impacted.

Lake Okeechobee Watershed Restoration Project

Located north of the lake, the LOWRP was designed to capture, store, and redistribute water entering the northern part of Lake Okeechobee. Its goals are to “improve water levels in Lake Okeechobee; improve the quantity and timing of discharges to the St. Lucie and Caloosahatchee estuaries; improve water supply for existing legal users of the Lake Okeechobee Service Area (LOSA); and increase the spatial extent and functionality of wetlands” (USACE, 2023b).

LOWRP planning has been actively ongoing since 2016. In November 2020 a revised final PIR was released with a draft report of the Chief of Engineers proposing a 46,000-AF above-ground water storage feature (termed “wetland attenuation feature”), 80 ASR wells, and approximately 4,800 acres of wetland restoration.⁵ Under a new administration, this plan was not approved by USACE headquarters “due in part to concerns raised by the Seminole Tribe of Florida” (USACE, 2024f) (see Chapter 3); the project was subsequently revised to remove the wetland attenuation feature and reduce the number of ASR wells

uncertainties identified by NRC (2015) and summarizes 26 studies involving geochemical measurements, hydrogeophysical characterization, laboratory experiments, field testing of reactivated ASR wells, and clusters of new ASR wells to be located along the northern perimeter of Lake Okeechobee. The studies described in the 2021 ASR Science Plan are expected to be completed in 2030.

The 2022 ASR Science Plan (USACE and SFWMD, 2022b), developed under the guidance of an independent peer-review panel, is intended to serve as an update of the 2021 ASR Plan and was released in draft form in October 2022. The 2022 ASR Science Plan is organized around the following principal uncertainties identified in the 2015 NRC report: (1) project sequencing, (2) future construction and testing to evaluate aquifer properties, (3) understanding phosphorus reduction potential, (4) operations to maximize stored-water recovery, (5) disinfection and treatment of recharge and recovered waters, (6) ecotoxicology and ecological risk assessment, (7) water quality, and (8) ASR cost-benefit analysis (USACE and SFWMD, 2022b). Progress on the 2022 ASR Science Plan is discussed in Box 2-2.

North of Lake Okeechobee Storage Reservoir Section 203 study.

In a rapid planning effort started in April 2023 and led by the SFWMD, three above-ground storage alternatives, including previous and newly developed alternatives, were analyzed. By October 2023, a tentatively selected plan was identified for the North of Lake Okeechobee Storage Reservoir (also known as the Lake Okeechobee Component A Reservoir [LOCAR]). By February 2024, the SFWMD released the final feasibility study (SFWMD, 2024b), and the USACE released the final EIS (USACE, 2024c). The plan proposes a deep reservoir (average depth = 18 ft) that would add 200,000 AF of above-ground storage north of Lake Okeechobee. The reservoir is adapted from a design that was previously screened out in the LOWRP process (for more details, see Box 3-4; USACE and SFWMD, 2020b). The reservoir would contribute much needed storage to the CERP as described by the University of Florida Water Institute (2015) and NASEM (2016) at an estimated cost of $3.5 billion (SFWMD, 2024b).

Modeling for the project suggests that LOCAR will increase the percent of time that Lake Okeechobee spends within the preferred stage envelope (11.5–15.5 ft NGVD29) and the number of events of optimal flows to the Caloosahatchee and St. Lucie Estuaries. The analysis also showed an increase in the percent of time (to a small degree) when lake water levels are below preferred levels, potentially causing harm to the lake’s littoral zone. However, the comparisons against existing conditions can be difficult to interpret because the existing conditions baseline (ECB) and alternatives are modeled using the most recent LOSOM while the future without (FWO) uses the 2008 Lake Okeechobee Regulation Schedule (LORS); thus, the results are not solely demonstrating the

effects of additional storage, but rather they illustrate the effects of storage addition coupled with Lake Okeechobee operational changes. Overall, however, the additional storage in the system should have positive effects, assuming reasonable operations (Julian and Reidenbach, 2024). Future studies will need to identify the system operations that work best with LOCAR as it comes online, similar to the LOSOM planning study.

Biscayne Bay and Southeastern Everglades Restoration

The freshwater and coastal wetlands and subtidal habitats of Biscayne Bay and the southeastern Everglades have been affected by over-drainage and by

the northwest area, optimization of water volumes across the coastal ridge, maximum conveyance flexibility, and storage of enough water to rehydrate the largest extent of BBSEER’s target footprint. Because the analyses are ongoing, the committee did not review outcomes or the alternative selection process in detail.

NASEM (2023) noted that several of the performance measures are closely related to each other (e.g., near-shore salinity, wetland salinity, freshwater depth, hydroperiod, and timing and distribution of flow), such that the relative impact of other performance measures such as resilience and connectivity is likely diluted. The committee also recommended a nuanced approach to comparing alternatives including evaluating performance measures for each

A positive development in the monitoring of Lake Okeechobee is the expansion of phytoplankton sampling sites over the past 3 years; the number of fixed phytoplankton monitoring stations was increased from six year-round stations to nine stations during the dry season (November 1–April 30), and to 32 stations during the wet season (May 1–October 31). This expanded coverage has helped fill data gaps in lake response, which is important given the spatial heterogeneity of the lake (Carrick and Steinman, 2001). Because this expanded monitoring period includes only 3 years of monitoring, trend analysis is not appropriate. However, as shown in Figure 2-29, WY 2023 had not only a higher percentage of samples that met bloom conditions (defined as chlorophyll a concentrations > 40 μg/L) but also greater chlorophyll a concentrations than in the prior 2 years. At present, there is no clear evidence of improving water quality conditions in Lake Okeechobee.

Stormwater Treatment Areas

The STAs are critical components of Everglades restoration managed by the SFWMD, and they play major roles in reducing TP concentrations and loads from agricultural and urban runoff and Lake Okeechobee. The Everglades STAs are essentially constructed freshwater treatment wetlands built on acquired agricultural lands located north of the Everglades Protection Area (Figure 2-30). To protect the Everglades ecosystem, the construction and operation of STAs were mandated under the 1992 Consent Decree⁸ and subsequently by the Everglades Forever Act (Section 373.4592, Florida Statutes). A total of five STAs (STA-1E, -1W, -2, -3/4, and -5/6) with a combined treatment area of 62,000 acres have been built and have been operating over varying periods (Figure 2-30). Using interior levees, each STA is divided into multiple cells dominated by emergent aquatic vegetation (EAV), SAV, or a mixed marsh plant community, which includes both EAV and SAV in the same cell (Armstrong et al., 2023; Chimney, 2024). The STAs are spatially positioned along three flow paths: the Eastern Flow Path (STA-1E and STA-1W), the Central Flow Path (STA-2 and STA-3/4), and the Western Flow Path (STA-5/6) (Figure 2-30).

The Restoration Strategies Plan, launched in 2012, provides for expanding existing STA acreage and additional infrastructure improvements to meet the water quality–based effluent limit (WQBEL). The WQBEL requires that the annual flow-weighted mean outflow TP concentrations from each STA not exceed 13 μg/L in more than 3 out of 5 years (on a rolling basis) and not exceed 19 μg/L in any year (FDEP, 2012a,b). The Restoration Strategies Plan (SFWMD, 2012) included construction of approximately 6,500 acres of additional treatment

area, repairs to STA-1E and STA-5/6, and three flow equalization basins (FEBs) to moderate low and high flow conditions into the STAs (Figure 2-30). Restoration Strategies Plan projects are expected to be fully implemented and operational by December 31, 2025. The first year of discharge data to be incorporated into assessment of WQBEL attainment begins in WY 2027 (May 2026-April 2027). Progress on implementing the Restoration Strategies Plan is described in Table 2-6. Nearly all components of the original Restoration Strategies Plan have been completed as of early 2024, except the G-341 structure and subregional source controls in the Eastern Flow Path and internal improvements to STA-5/6 and full operation of the C-139 FEB in the Western Flow Path.

In NASEM (2023), the committee presented a detailed data analysis to determine the long-term performance of STAs during the operation period (WY 2004-2022). This analysis showed that high inflow TP concentrations coupled with high phosphorus loading rates are key external drivers of the overall performance and treatment efficiency of STAs. In this section, the committee briefly updates that review based on data focused on the recent 5 water years

TABLE 2-6 Summary Status of Major Restoration Strategies Projects

SOURCES: Data from Chimney, 2024; Shuford et al., 2024.

(WY 2019–2023). During this period, all STAs were affected by extreme events, including hurricanes, regional droughts, and continued changes in the operation and maintenance of STAs.

Status of STAs in WY 2023

NASEM (2023) provided a detailed analysis of STA treatment performance, so this section provides an update based on new information (i.e., WY 2023 data)

TABLE 2-7 Select Water Quality Parameters for Five STAs During the Operation Period of WY 2023 (May 1, 2022 to April 30, 2023) and the Period of Record of Operation

NOTES: FWM = flow-weighted mean. Conversion factors are 1 acre = 0.4047 hectares (4,047 m²); 1 AF = 1,234 m³; 1 metric ton = 1,000 kg; 1 cm per day = 0.3937 inches per day.

SOURCE: Modified from Chimney, 2024, with additional analysis of treatment efficiency from the committee.

89 percent load-based treatment efficiency (Figure 2-31; Table 2-7). The addition of STA-1W Expansion #2, which will provide an additional 1,600 acres of treatment area (Shuford et al., 2024), is expected to decrease outflow TP concentrations further and bring STA-1W closer to meeting WQBEL requirements.

Performance of STAs in the Central Flow Path (STA-2 and STA-3/4).

STA-2 and STA-3/4 receive agriculture runoff from EAA basins and releases from Lake Okeechobee. Inflow TP concentrations to STA-2 and STA-3/4 have been significantly lower than those to the other STAs, both recently and over the period of record (Chimney, 2024), which eases the challenge of attaining the WQBEL. The Restoration Strategies Plan in the Central Flow Path included the A-1 FEB and STA-2 Expansion (see Table 2-6; Shuford et al., 2024).

Substantial refurbishment and vegetation management was under way in STA-2 during WY 2023, with one of five flow-ways (equal to 15 percent of the treatment area) offline the entire year. Despite a low TP loading rate (0.9 g/m²-yr), outflow TP concentrations increased from 15 μg/L to 29 μg/L from WY 2022 to

S-333 complex and installing low-sill weirs upstream of the S-333s to reduce canal velocities and bedload transport. Completion of this project is estimated for 2026 (Hutchins, 2024). Monitoring will be conducted to evaluate the effectiveness of these actions, identify opportunities to continue to mitigate TP loading to Everglades National Park, and inform future management actions (Bartlett et al., 2023). Depending on the results of these initial actions, the S-333 Working Group (2023) noted that further work could be warranted, including a comprehensive study of an expanded portion of the canals and marsh within WCA-3A area upstream of the S-333s to determine the dominant sources (sediment, floc, and suspended in the water column) of phosphorus and the mechanisms by which these materials are contributing to TP loading to Everglades National Park.

Biogeochemical Dynamics in the Decomp Physical Model and CEPP South

The potential for enhanced transport of previously deposited phosphorus along canals or in wetland sediments has been illuminated from work in the Decomp Physical Model (DPM), with important implications for CEPP South.

One of several unanticipated outcomes of DPM was that high velocity inflows with low surface-water concentrations of TP (i.e., ≤10 μg/L TP) produced phosphorus-impacted conditions downstream because of transport of phosphorus-enriched sediments and increased loads to the previously unimpacted area. This change resulted in the loss of the slough periphyton community and invasion of cattails (Saunders, 2020; Saunders et al., 2016, 2021; Sklar, 2020). Cattails continue to spread downstream within WCA-3B toward the L-29 Canal and Everglades National Park at a rate of 100 m/yr (Saunders and Newman, 2023). Ongoing work to address this issue in an adaptive management framework is discussed in more detail in Chapter 5.

Long-Term Monitoring Trends and Data Issues

Observations of TP concentrations from the Florida Coastal Everglades Long-Term Ecological Research program (FCE LTER) may yield important insight on

phosphorus dynamics in the Everglades in response to increases in discharge. The FCE LTER has established long-term monitoring stations in Shark River Slough and Taylor Slough along transects from the headwater reaches of Everglades National Park through the mangroves and into Florida Bay. The FCE LTER observed increasing trends in TP concentrations over the past decade in wetlands in Shark River Slough and Taylor Slough. However, this pattern of increasing TP concentrations in water grab samples is inconsistent with observations reported for nearby sites by the SFWMD, which do not show temporal trends (Gaiser, 2023; Figure 2-37).

The FCE LTER and Everglades National Park are collaborating to understand the reason for this discrepancy in temporal trends. They have collected and analyzed paired samples using their standard methods and compared results, which show no differences due to sample collection procedures or analytical methods. They continue to investigate whether this discrepancy is due to differences in locations or daily timing of sample collections or methods of preservation.

The FCE LTER has also been collecting two types of water samples since the early 2000s: 3- to 6-day integrated, diurnal sequential samples and daytime grab samples. Interestingly, TP concentrations in diurnal composite samples are considerably greater than values in grab samples. The reason for this discrepancy between the two sampling approaches is not clear but could potentially