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Re-Engineering Water Storage in the Everglades: Risks and Opportunities 2 Major Storage Components Storage is at the heart of any attempt to restore the Everglades. A brief examination of the Restoration Plan components (Figure 2-1) shows that many of them either directly or indirectly involve storage. This chapter contains a summary and comparison of the major existing storage components (Lake Okeechobee and the Water Conservation Areas), conventional above-ground surface reservoirs (Kissimmee Basin, Everglades Agricultural Area and vicinity, and the Upper East Coast region), below-ground storage using aquifer storage and recovery (ASR; multiple projects), and in-ground storage in the Lake Belt region. Water-quality considerations are also discussed for each component in this chapter. While seepage management and water reuse and conservation, strictly speaking, are not storage projects, they also are discussed because they affect the overall water budget and ultimately the amount of storage required in the system. Water-quality considerations are also discussed for each component. Conversely, while stormwater treatment areas provide some storage, they are addressed only with respect to their primary function of improving water quality and where they are closely associated with major storage components. Other Restoration Plan features that are not discussed in detail in this chapter include features that are small or were designed primarily as “flow-through” structures in conjunction with ASR projects. To understand the storage components and the fluxes between them, it is helpful to be familiar with how the Everglades planners have conceptualized and modeled the hydrologic system. The primary tool used to physically model the system in the past, present, and future is the South Florida Water Management Model (SFWMM). The SFWMM simulates the hydrologic regime and the management of the system from Lake Okeechobee to Florida Bay using both lumped and distributed modeling techniques. Most of the domain is covered with a finite-difference mesh of 2 mile × 2 mile cells. However, Lake Okeechobee is modeled (or “lumped”) as a single point in space, and a simple flow balance procedure is used for other areas. The model simulates rainfall, evapotranspiration, infiltration, overland and groundwater flow, canal flow, canal-groundwater seepage, levee seepage and groundwater pumping. It incorporates current or proposed water management control structures and current or proposed operational rules (SFWMD, 1997a). The model has been used to simulate numerous scenarios, of which three are applicable to this chapter. The first (Figure 2-2) is of the system infrastructure and operations as they were around 1995 (the “1995 Base,” often referred to as the “current condition” or “existing condition”). The input data include a 31-year climatic record (1965-1991), recently extended in the Initial Comprehensive Everglades Restoration Plan (CERP) Update to 36 years. Both very wet and very dry years are included. The update, which is ongoing, will soon be reflected in new
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-1. Restoration Plan components. SOURCE: Available online at http://www.evergladesplan.org/images/cerpmap_200.jpg.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-2. Primary water budget components for a 31-year simulation of the SFWMD model using the structures in place in 1995 (the “1995 Base” case of the Restoration Plan). It is considered by restoration managers to reflect the typical “current condition” of the system. SOURCE: Available online at http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/95BSR/WBUD/95BSR.pdf.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities base scenarios and model runs, but until then, the 1999 CERP still is the reference. Information on the update is at http://www.evergladesplan.org/pm/recover/icu.cfm. The second scenario uses the same climatic record as the 1995 Base, but reflects the likely system infrastructure and operations as they would be around 2050 without any of the Restoration Plan projects in place (the “2050 Base,” also referred to as the “future without project” condition or the “no-action alternative”). Despite increased water-use demands and other differences, this has many similarities with the 1995 Base and is not shown here. The third (Figure 2-3) is a simulation using the same projected land use and water demands as in the 2050 Base, but also assuming completed Restoration Plan (and other) projects. It is known as alternative D13R after its SFWMM run number. Note the additional components in Figure 2-3 relative to Figure 2-2, including aquifer storage and recovery, surface storage, and wastewater reuse. Comparing the storage and flows estimated by alternative D13R and similar runs with those of the 1995 Base and 2050 Base is a major approach used to evaluate potential achievement of hydrologic goals for the restoration effort. We use the simulation results for the 1995 Base and the alternative D13R to provide estimates of storage capacity for various current and planned storage components. This committee has not conducted a critique of the SFWMM, and recognizes—as do the USACE and the SFWMD—that it probably is not a perfect representation of current or future conditions. Nonetheless, the simulation results are useful for comparing the relative magnitudes of storage capacity associated with current and planned elements of the Restoration Plan. Figure 2-4 illustrates, qualitatively, an estimate of flow patterns before any of the human modifications to the system that began in the 1880s. CURRENT STORAGE COMPONENTS In the current system, the major available storage components are Lake Okeechobee and the Water Conservation Areas (Table 2-1; Figures 2-1 and 2-2). When fully implemented, the Restoration Plan anticipates capturing a large amount of the water currently discharged to the sea and storing it using a variety of structures and operational strategies that are major components of the plan. The major storage components of the plan discussed in this chapter are described in subsequent sections in terms of land requirements; costs for construction, operation and maintenance; constraints on sequencing of construction or implementation; design and operational complexity and flexibility; potential environmental risks and benefits; water quality issues; and advantages and disadvantages relative to other storage options. A map of existing facilities and structures managed by the South Florida Water Management District can be found at http://www.sfwmd.gov/images/pdfs/facility_map_overview.pdf. Lake Okeechobee Historically, the lake (Figures 1-1 and 2-5) served as the key hydrologic link between the mostly upland ecosystems in its large drainage basin to the north—the Kissimmee River Basin—and the sawgrass marshes and prairies of the Everglades proper to the south. Water storage provided by the large lake moderated the effects of low rainfall periods on the Everglades. Over the past century, the lake and its drainage basin have been greatly modified for flood control and other water management purposes, and it has become a highly engineered reservoir with numerous options for managing inflows, outflows, and water levels.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-3. Primary water budget components for the June 1998 model run D13R of the Restoration Plan. This is a simulation using the same 31-year climatic record (1965–1991) as the 1995 (and 2050) Base simulations, but using projected 2050 land use and water demands and assuming the Restoration Plan and other related projects have been implemented. There are very slight differences in the flows in this figure and the flows in Table 2-1, which is based on a slightly updated (November 1998) version of D13R. SOURCE: http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/ALTD13R/WBUD/D13R.pdf.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-4. A qualitative depiction of the original flow patterns in the Everglades. SOURCE: Available online at http://www.evergladesplan.org/maps/historic_flow.jpeg. On an annual basis under current operating conditions, Lake Okeechobee receives approximately 1.6 million acre-feet of inflow from the Kissimmee River and discharges approximately 416,000 acre-feet of coastal waters through the Caloosahatchee River and St. Lucie Canal. An additional 227,000 acre-feet of water are discharged to the Water Conservation Areas from Lake Okeechobee in a combination of regulatory releases to control stage in Lake Okeechobee and environmental releases to replace reductions of flow due to implementation of best management practices (BMPs). A total of 471,000 acre-feet from Lake Okeechobee is sent to agricultural areas in the Caloosahatchee and St. Lucie Basins to the west and east, and to the Everglades Agricultural Area to the south. The Water Conservation Areas (WCAs) receive additional inflow from drainage canals in the Everglades Agricultural Area (EAA; 917,000 acre-feet) and other adjacent areas (Figure 2-2).
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities TABLE 2-1 Storage Components of the Restoration Plan STORAGE COMPONENT Avg Annual Acre-feet in Avg Annual Acre-feet out MaxAnnual Acre-feet In MaxAnnual Acre-feet out Max annual inflow-outflow Total Capacity Acre-feet ASR capacity for 30% inj loss Construction Costs O&M Costs (per yr) Land Acres Land Costs Lake Okeechobee 2,537,300 1,803,400 4,263,200 4,022,700 2,231,900 2,250,000 Water Conservation Areas 1,633,200 316,100 3,138,600 567,200 2,879,200 1,882,000 Conventional Surface Reservoirs North Storage Reservoir (Kissimmee) 127,000 51,700 450,200 311,700 267,000 200,000 95,134,000 1,515,245 20,000 189,720,000 EAA Reservoirs 440,900 418,100 1,036,900 959,400 260,700 360,000 350,112,000 14,458,409 17,500 86,536,000 C44 Reservoir 19,530 9,550 57,960 58,870 43,820 33,150 118,859,000 ? 3,315 125,879,375 Other Upper East Coast Reservoirs 97,000 174,199,000 ? 9,458 130,055,433 Taylor Creek/Nubbin Slough 93,700 168,800 50,000 79,326,000 2,164,114 10,000 189,720 Caloosahatchee (C-43) Basin 395,140 337,650 725,570 661,810 167,590 160,000 inc. in C-43 ASR inc. in C-43 ASR 20,000 132,621,000 Central Palm Beach Reservoir 77,200 73,200 106,400 96,100 20,000 19,920 inc in CPB ASR Inc. in CPB ASR 1,660 57,657,000 Site 1 Reservoir 81,200 82,200 116,000 116,500 5,700 14,760 inc in Site 1 ASR inc in Site 1 ASR 2,458 23,587,000 Bird Drive Reservoir 138,300 18,800 150,900 38,000 147,800 11,600 52,459,000 1,470,869 2,877 71,625,000 Acme Basin 4,950 Seminole Tribe Big Cypress 7,440 Total conventional reservoirs 1,279,270 1,084,900 2,643,930 2,411,180 912,610 958,820 870,089,000 19,608,637 87,268 817,870,528 ASRs Lake Okeechobee ASR 259,100 134,600 1,120,100 521,700 1,120,100 3,859,500 1,449,870 1,108,797,000 25,000,000 300 7,515,000 Caloosahatchee (C-43) Basin ASR 97,910 47,630 170,500 139,200 170,500 1,558,680 648,117 313,574,000 6,707,889 inc. in C43 res C-51 (North Palm Beach II) ASR 80,500 24,200 135,700 73,000 132,000 1,745,300 996,650 122,391,000 1,496,000 34 9,945,000 West Palm Beach ASR (L-8 ASR) 37,800 11,700 54,600 32,800 54,600 809,100 457,560 53,428,000 ? ? ? Central Palm Beach Reservoir ASR 42,300 28,500 74,700 48,700 59,500 427,800 34,410 66,442,000 1,019,500 inc in CPB res Site 1 Impoundment (Hillsboro) ASR 55,700 23,000 106,800 56,200 100,300 1,013,700 495,690 116,792,000 2,052,608 inc in site 1 res Total ASRs 573,310 269,630 1,662,400 871,600 1,637,000 9,414,080 4,082,297 1,781,424,000 36,275,997 334 17,460,000 In Ground Reservoirs North Lake Belt 146,600 142,600 180,400 189,600 34,300 90,000 381,193,000 1,241,234 5,861 154,868,000 Central Lake Belt 100,500 95,000 237,100 238,700 196,000 190,000 402,502,000 1,964,519 5,770 100,359,000 L-8 Basin 76,000 76,700 101,900 118,600 55,300 48,000 ? ? 1,200 ? Total in-ground reservoirs 323,100 314,300 519,400 546,900 285,600 328,000 0 783,695,000 3,205,753 12,831 255,227,000 Seepage Management WCA3A/3B Levee Seepage Mgmt 128,600 57,526,000 783,432 5,887 167,646,000 C-11 Reservoir (part of 3A/3B seepage) 68,300 80,700 121,300 144,000 0 (gw inflow makes updeficit) L-31N Seepage Mgmt 161,900 89,514,000 4,647,234 3,947 94,704,000 Total seepage management 371,200 147,040,000 5,430,666 262,350,000 Water Reuse West Miami-Dade Water Reuse 111,000 to Bird Dr. Rech 112400(to Bird Dr. Rech) 435,998,000 36,500,000 100 3,540,000 South Miami-Dade Water Reuse 73,730 (south to C-102) 359,700,000 47,815,000 200 3,324,000 73,000 (north to C-100) Total water reuse 257,730 795,698,000 84,315,000 6,864,000
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Data sources and other notes for Table 2-1 Many values in the table are based on simulation output, which are reported to more significant figures than can be verified. These values provide only general comparisons of the magnitudes of flows and storage capacity, as no quantitative estimates of uncertainty are available. While every attempt has been made to verify the information in this table, the Restoration Plan is continually being modified, so storage, flux, acreage, and cost information are evolving with it. Likewise, quantitative information for closely related projects, such as reservoirs and stormwater treatment facilities, is sometimes lumped. Up-to-date information on these projects can be obtained at any time from the USACE and SFWMD. There are very slight differences in the flows given in this table and those shown in Figure 2-3. Both are based primarily on output from alternative D13R of the South Florida Water Management Model; however, this table is based on a slightly updated (November 1998) version of D13R relative to Figure 2-3, which is based on a June 1998 version of D13R. Fluxes Most fluxes are from water budget for D13R (11/98 version) (http://www.sfwmd.gov/org/pld/restudy/hpm/frame1/maps/mapdir/D13R1198/WBUD/annbud). South and West Miami-Dade water reuse fluxes from Appendix B, section B.18.104.22.168, p. B-192 of USACE and SFWMD (1999), except for Average Annual West Miami-Dade Reuse, which is from M. Irizarry, SFWMD, personal communication, November 2004. See Fig. B.3-88 for bar graph of volumetric savings from water use reductions. Inputs to reservoirs do not include local precipitation or seepage. Outputs from reservoirs do not include evapotranspiration or ASR injection losses. Water fluxes to and from Water Conservation Areas (WCAs) include overland flow and groundwater seepage. Seepage management “annual acre-ft out” for WCA3A/3B and L31-N from J. Obeysekera, SFWMD, written commun., May 2004, and computed as “seepage prevented” between D13R and 2050base. Capacities Most capacities are from individual project descriptions at http://www.evergladesplan.org/pm/projects/project_list.cfm. Reservoir capacities for C-44 and Upper East Coast Reservoirs taken from the Indian River Lagoon Project Implementation Report Lake Okeechobee capacity approximated from data summarized in table 3-2 of this report, and is the volume at max allowable stage (18.5 NGVD) minus the volume at min allowable stage (13.5 NGVD). WCA capacity from Light and Dineen (1994); also based on current regulation schedule. ASR “capacities” refer to injected water remaining in the aquifer after the 31 year simulation and are calculated as (avg. annual acre-feet in - avg. annual acre-feet out) × 31 years ASR “capacities” for 30% injection loss refer to usable (non-saline) water remaining in the aquifer after the 31 year simulation and are calculated as (0.7 × avg. annual acre-feet in - 1 × avg. annual acre-feet out) × 31 years. Construction, O&M, and Land Costs; Acreage Acreages from Table 9-1 of USACE and SFWMD (1999). Construction and Real Estate Costs in 1999 dollars from Table 9-2 of USACE and SFWMD (1999). O&M Costs in 1999 dollars from Table 9-3 of USACE and SFWMD (1999). Construction and land costs for C-44 and Upper East Coast Reservoirs taken from the Indian River Lagoon Project Implementation Report. These costs are in 2003 dollars.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-5. Drainage basin of Lake Okeechobee. SOURCE: SFWMD et al. (2004).
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities Although Lake Okeechobee no longer provides the hydrologic services to the Everglades that it provided in its natural state, it still provides substantial water storage under current operating conditions. The lake’s surface elevation and associated area and volume vary considerably both intra-annually and inter-annually in response to wet and dry climatic conditions, but at a normal high-water stage of 15 feet (4.6 m) above mean sea level, the lake has a surface area of 700 mi2 (1814 km2), an average depth of 9 ft (~2.7 m), a maximum depth of 15.5 ft (4.6 m), and a volume of 4.0 × 106 ac-ft (4.9 × 109 m3). The lake has a maximum north-south (open-water) length of 35 miles (56.5 km) and maximum east-west length of 29.6 miles (48 km). The natural drainage basin for Lake Okeechobee is primarily north of the lake (Figure 2-5), and the Kissimmee River is by far the largest tributary. The Kissimmee River Basin extends north almost 100 miles to near Orlando, Florida and accounts for about 60 percent of the lake’s 5,022 mi2 (13,000 km2) drainage basin (including the area of the lake itself) (http://www.esg.montana.edu/gl/huc/03090101.html). As noted above, annual water inputs to the lake vary substantially, but typical values are in the range 1,500,000 to 3,300,000 ac-ft (2.0-4.7 × 109 m3), resulting in a range of water residence times in the lake of about 1-3 years. A lake-stage regulation schedule has been used to manage lake levels for several decades. The schedule is modified periodically to reflect changes in management goals. The most recent of these is the “Water Supply/Environmental” (WSE) regulation schedule that was approved in July 2000 (http://www.sfwmd.gov/org/pld/hsm/reg_app/lok_reg/). In general, the schedule provides for maximum lake stage in winter and spring and lower stage during summer and fall to provide storage capacity for inflows associated with the summer rainy period and hurricane season. The storage volume available in Lake Okeechobee is a function of the regulation schedule (Figure 2-6). The maximum available storage under current operating conditions may be considered simply as the difference between the maximum allowed stage, 18.5 ft NVGD (National Vertical Geodetic Datum, essentially equivalent to mean sea level) and the minimum stage under which regulatory discharge is allowed (13.5 ft NVGD), if we assume that over a wet-dry climatic cycle there is no net loss of this storage to the sea. This volume (interpolated from Table 2-2) is 2,250,000 acre-feet (3.2 × 109 m3). This maximum storage volume is insufficient to accommodate the average annual inflows of approximately 2.5 million acre-feet from sources excluding local precipitation during the 31-year record used to evaluate the Restoration Plan and is much smaller than the maximum annual inflow of over 4 million acre-feet in that record. The Restoration Plan will modify the current operating rules, but the objective of these modifications is not to provide additional water storage. Based on the maximum change in lake storage simulated in the D13R run, 2,231,800 acre-feet (Table 3-1), the potential storage capacity of the lake will be virtually unchanged by implementation of the Restoration Plan. Use of Lake Okeechobee as a storage option was explored in a screening phase of the Restudy (i.e., the formal evaluation process that culminated in the Restoration Plan) but was not included in any of the project alternatives. The goals used in the screening evaluation of Lake Okeechobee were to prevent discharge to the Caloosahatchee and St. Lucie estuaries, provide water supply, and maintain water levels in the lake that were consistent with levee stability and healthy lake conditions. In the initial modeling runs the latter objectives were ignored, in that no restrictions were placed on water levels. These runs demonstrated that maximal use of storage in Lake Okeechobee would be “cost effective and hydrologically efficient” (USACE and SFWMD, 1999). They also demonstrated that such use would cause extreme fluctuations in lake levels, fluctuations that would be expected to adversely affect the littoral zone of the lake. The planned
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-6. “Water Supply/Environmental” (WSE) regulation schedule for Lake Okeechobee. SOURCE: Redrafted from http://sfwmd.gov/org/pld/hsm/reg_app/lok_reg/wse_support/wse_sched.pdf.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities maintenance and repair costs to consider as well. Operational costs in terms of pumping and distribution should be similar to those of other surface reservoirs. Water-Quality Considerations Water quality of the stormwater runoff used to supply Lake Belt reservoirs will depend on land uses in the drainage areas from which the runoff is derived. The Northern Lake Belt reservoir will receive local basin runoff and, ultimately, some water recovered from WCA 3A/3B seepage-management efforts. The Central Lake Belt reservoirs are intended to store excess water from WCAs 2 and 3, routed to the reservoirs via improved L-37 and L-33 borrow canals. Most local basins likely will be in urban/suburban land use, but some lands used for intensive agriculture also may contribute runoff. Consequently, some water supplying these reservoirs is likely to be contaminated with constituents usually associated with these land uses: elevated nutrients (nitrogen and phosphorus) and oxygen-demanding biodegradable natural organic matter; suspended solids; potentially pathogenic microorganisms of animal and possibly human origin; a variety of heavy metals, including zinc, cadmium, and lead; and low levels of a wide variety of synthetic organic contaminants (e.g., herbicides, pesticides, and polycyclic aromatic hydrocarbons) used on urban landscapes or formed in urban environments. Certain characteristics of the reservoirs may lead to improvements in the quality of the water stored there for extended periods. The morphometry of the reservoirs—steeply sloping sides, small littoral zones, and large mean and maximum depths—should promote settling of suspended material and minimize resuspension of bottom sediments by wind-induced mixing. If annual nutrient loading rates are not too high and water residence times are fairly long, nutrients will be assimilated by algae and conveyed to the bottom by natural settling processes, such that the reservoirs may have moderately high water clarity and relatively low chlorophyll levels, making them suitable for certain kinds of aquatic-based recreational activities. On the other hand, reservoir morphometry also is likely to promote strong thermal stratification in the water column that may persist for long periods (possibly several years). This will lead to highly anoxic conditions in the stagnant hypolimnion (cooler bottom layer of water), which is likely to comprise a large fraction of the total volume of Lake Belt reservoirs, and to the build-up of undesirable constituents, including sulfide, ammonia, methane, dissolved iron, and manganese. This will cause a large fraction of the stored water to be unsuitable for municipal water supply—or at least render it much more difficult and expensive to treat. In addition, such water would violate state water-quality standards for direct release into surface drainage canals in the Everglades drainage network, although it could be made to meet state standards by treatment involving aeration before release. Alternatively, it may be desirable to maintain oxygenated conditions throughout the water column of Lake Belt reservoirs by installing aeration devices in the reservoirs. Although such devices are technically feasible, they would be costly to operate and maintain, given the size and depths of the reservoirs (and the volumes of water that would need to be aerated).
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-12. Map showing the location of the proposed Central and North Lake Belt Storage Areas, L-31N Seepage Management, and the West Miami-Dade Wastewater Reuse Facility. Water Conservation Areas 3A and 3B Levee Seepage Management would be located just north of this map and the proposed reuse facility associated with the Miami-Dade South Wastewater Treatment Plant about 15 miles to the south. SOURCE: Available online at http://sflwww.er.usgs.gov/publications/ofr/02-325/introduction.html.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities The major ion composition of the lakes also could be an issue. Constructed in a limestone stratum, the lakes will have hard water (high in calcium, magnesium and bicarbonate alkalinity). Although these constituents are desirable from many perspectives, they have the potential to substantially increase the hardness and ionic strength of water flowing through the southern Everglades, a system driven primarily by rainfall chemistry and thus historically a soft-water environment. The flora and possibly associated fauna of this part of the Everglades are adapted to soft water, and major shifts in plant community composition could result from use of the Lake Belt to supplement water flows to the Everglades during periods of low rainfall. Finally, water-quality concerns regarding the Lake Belt reservoirs include the potential for contamination of the shallow Biscayne Aquifer, which is used for drinking-water supply. This potential depends on the source and level of pre-storage treatment applied to water that will be added to the reservoirs, as well as on the hydraulic connection that remains between the reservoirs and the aquifer once seepage barriers have been constructed. The Lake Belt Pilot Project includes a water-quality evaluation to address these concerns. Changes in the groundwater flow field associated with reservoir construction and operation could also affect operations at municipal well-fields near the Lake Belt. The pilot project includes a regional hydrologic evaluation to evaluate these potential impacts. Seepage Management Differences in hydraulic head across levees that bound the Water Conservation Areas and Everglades National Park result in significant seepage losses to the east, toward the coast through adjacent canals. For the overall Everglades system, the Governor’s Commission for a Sustainable South Florida (1997) estimated seepage losses at over one million acre-feet per year, a significant amount in relation to other components of the Restoration Plan. Seepage management reduces the losses or recovers this water and returns it to the Everglades as a water conservation measure. Two locations are planned for this Restoration Plan component: Everglades National Park Seepage Management. The purpose of this project (Figure 2-12) is to improve water deliveries to Northeast Shark River Slough and restore wetland hydropatterns in Everglades National Park by reducing levee and groundwater seepage and increasing sheet flow. This will be accomplished by a levee cutoff wall along levee L-31N, south of the Tamiami Trail, which reduces groundwater flows during the wet season and by capturing the groundwater with a series of wells adjacent to L-31N, then back-pumping those flows to Everglades National Park. This project is expected to conserve about 162,000 acre feet annually (J. Obeysekera, SFWMD, written communication, May 2004). This conserved volume, and the value for WCA 3A/3B below, is estimated from modeling the difference between seepage at these sites without the Restoration Plan (2050 Base) and with it (D13R). Water Conservation Areas 3A and 3B Levee Seepage Management. The goal of this project is to reduce seepage loss from these WCAs in order to improve hydroperiods within the Conservation Areas by allowing higher water levels in the borrow canals and longer inundation within the marsh areas that are located east of the WCAs and west of US Highway 27. New levees will be constructed west of US Highway 27 from the North New River Canal to the Miami (C-6) Canal to separate seepage water from the urban
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities runoff in the C-11 diversion canal. Higher-quality seepage from the WCAs and marshes will be collected and returned to the Water Conservation Areas via features associated with the C-11 Impoundment project or stored in either the C-9 or C-11 Impoundment. Collected seepage water will further be transported by canal to the Central Lake Belt, for distribution to Everglades National Park (S. Applebaum, personal communication, January 2005). The Western C-11 Diversion Impoundment and Canal will capture lower-quality water from urban runoff and agricultural areas that is presently back-pumped into WCA 3A through the S-9 pump station and discharge it either into the North Lake Belt Storage Area (once it is on line), C-9 Impoundment, or WCA 3A after treatment (USACE and SFWMD, 1999, p. 9-19). This project is expected to conserve about 129,000 ac-ft annually (J. Obeysekera, SFWMD, written communication, May 2004). The S-9 pump station will also be used to divert excess water above WCA 3A/3B target depths to the Central Lake Belt Storage Area or Shark River Slough via the improved L-37 or L-33 borrow canals, respectively. At the L-31N site, a pilot project will evaluate technologies to reduce levee seepage flow across L-31N adjacent to ENP via a levee cutoff wall (vertical subsurface barrier with a confining layer at its base) and to reduce groundwater flows during the wet season by capturing the groundwater with a series of wells adjacent to L-31N, then back-pumping those flows to ENP through the S-356 pump station (to be replaced by two new stations: S-356A and S-356B). Other technologies may also be explored, such as those reviewed and described in the Technical Advisory Report on Seepage Management (Governor’s Commission for a Sustainable South Florida, 1997). Uncertainties about these techniques are similar to those for creation of barriers to flow for the Lake Belt quarries. The L-31N pilot project is expected to contribute to a refined design and better understanding of construction technologies upon its completion. This activity is especially important given the 100 percent effectiveness (recovery of seepage) assumed for this Restoration Plan component (USACE and SFWMD, 1999). The final seepage-management strategies developed must not only reduce the loss of water from the Everglades but also prevent significant downstream impacts to water supplies, flood control, and wetland and estuarine systems. There is some urgency to initiate these projects because both are on the boundaries of the natural system, and adjacent land is threatened by urbanization. Using the November 2004 Draft Master Implementation Sequencing Plan (MISP, http://www.evergladesplan.org/pm/misp.cfm#docs) for estimates of “streamlined” completion dates and Figure M-1 from SFWMD and USACE (1999) for estimates of construction duration, the WCA 3A/3B project is scheduled to be completed in 2008 after about four years of construction, the Everglades National Park seepage-management project is scheduled to be completed in 2009 after about four years of construction, and the L-31N pilot project is scheduled to be completed in 2008 after about one year of construction (to which will be added an additional year of monitoring). Setbacks could occur if the cutoff wall technologies are unable to stem the loss of water through the levees. The anticipated cost for the L-31N pilot project is about $10 million (USACE and SFWMD, 2002a). The overall Everglades National Park seepage-management project will be constructed in conjunction with modifications to structure S-356, for an overall construction cost of about $90 million. Similarly, the WCA 3A/3B seepage-management project will be constructed in conjunction with the canal C-11 diversion impoundment, for an overall projected con-
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities struction cost of about $58 million. Even though the SFWMD owns the levees themselves, total land requirements for the Everglades National Park and WCA 3A/3B projects are 3,900 acres and 5,887 acres, respectively, corresponding to estimated real-estate costs of $95 million and $168 million (Tables 9-1 and 9-2, USACE and SFWMD, 1999). (The current web site, 8/27/04, for the WCA 3A/3B project lowers the land requirement to 4,323 acres, with 2,970 acres currently acquired.) The L-31N Pilot Project will be constructed entirely on public land and not require any land acquisition. The Everglades National Park seepage-management project involves back-pumping of recovered water into the park itself. Hence, there will be continuing operation and maintenance costs associated with this option compared to installation of the seepage barrier itself, which will be a one-time capital cost. The selection of seepage-management technology will include an evaluation of the trade-offs between higher capital costs (e.g., slurry walls, grout curtains) and higher operation and maintenance costs (e.g., back-pumping). Annual operation and maintenance costs estimated in the plan for this component approach $5 million. Environmental Considerations The proposed technologies to control seepage may have unintended consequences that must be investigated before full-scale implementation of the proposed project features; hence, the Everglades National Park project includes the L-31N pilot project intended to investigate seepage-management technologies. Possible unintended consequences to be investigated as part of this pilot project include negative impacts on the Miami-Dade West Well Field located just east of the project site; reduction of freshwater flows toward Biscayne Bay; and the potential to attract contaminated agricultural runoff due to the pumping component. Furthermore, this project includes relocation of the Modified Water Deliveries structure S-357 to provide more effective water deliveries to Everglades National Park. New discharges to Everglades National Park must be designed to meet applicable water-quality criteria. The Everglades National Park project is also dependent upon modification to S-356 structures to provide more effective water deliveries to the Park. Water Reuse and Conservation Treated wastewater from the Miami-Dade South Wastewater Treatment Plant currently is pumped over 2,000 ft deep into the “boulder zone” of the Floridan Aquifer. The Wastewater Reuse Technology Pilot Project for West and South Miami-Dade envisions two wastewater reuse facilities to increase the quantity of water available for ecological restoration. One facility would be associated with the existing Miami-Dade South treatment facility at the southern end of Biscayne Bay, and the other would be associated with a proposed wastewater treatment plant in the west Miami-Dade area near Bird Drive (Figure 2-12). Ultimately, reclaimed wastewater from the two plants is anticipated to provide an average of 230 MGD (258,000 ac-ft/yr) and maximum of 231 MGD (259,000 ac-ft/yr) (USACE and SFWMD, 1999, pp. 9-23 and 9-24; M. Irizarry, SFWMD, personal communication, November 2004) for restoration. The 131 MGD (147,000 ac-ft/yr) South Miami-Dade reclaimed wastewaters will be used primarily to augment freshwater flows to south Biscayne Bay that might otherwise be lost through restoration efforts closer to and within the Everglades. South Miami-Dade reclaimed flows are estimated to be 74,000 ac-ft/yr
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities directed south toward C-102 and 73,000 ac-ft/yr directed north to C-100 (USACE and SFWMD, 1999, p. A4-43). The 100 MGD (112,000 ac-ft/yr) West Miami-Dade reclaimed wastewaters will be used to elevate water levels in the Bird Drive Basin and thus reduce seepage losses from Everglades National Park buffer areas and enhance water supply for groundwater recharge, South Dade conveyance system demands, and northeast Shark River Slough demands. Other conservation efforts applied to water use (e.g., reduction of per capita potable water requirements) have not been factored into the plan explicitly. Rather, different future potable water-use requirements in 2050 range from 1,200 to 1,450 MGD (1.344 million to 1.769 million ac-ft/yr) reflecting greater or lesser conservation practices. These estimates are reflected in the background planning for the Restoration Plan (USACE and SFWMD, 1999). Overall, water conservation is expected to yield about 63 MGD or about 71,000 ac-ft/yr (J. Obeysekera, SFWMD, personal communication, May 2004). Although the Restoration Plan anticipated that the reused water would be treated to a level needed to sustain estuarine and wetland biological communities in the Bay area, the technology that will be required to effect this treatment and the associated costs are not well established. The Technology Pilot Project at the existing South Miami-Dade treatment plant is designed to address these issues. The plan anticipates adding a pretreatment and membrane treatment system to the existing secondary treatment facility (CDM, 2004). The plant will have a capacity of 131 MGD. It is anticipated that phosphorus will be the primary constituent of concern in the reclaimed water. Therefore, the treatment will be designed to remove total phosphorus to acceptable levels. Evaluating whether this system will perform as anticipated is another reason for the Pilot Project. The dual-membrane technology to be used is relatively new (NRC, 1998), and although it has been applied at several locations (del Pino and Durham, 1999), performance and costs are uncertain. The West Miami-Dade Wastewater Treatment Plant has not yet been constructed. Discharge of reclaimed water from this plant is planned for the Bird Drive Basin in western Miami-Dade County, east of Krome Avenue. In addition to the Miami-Dade facilities, the City of West Palm Beach is constructing a pilot facility to treat wastewater from the East Central Regional Wastewater Treatment Facility using advanced wastewater-treatment processes to remove nitrogen and phosphorus. After treatment, the wastewater will be used to restore 1500 acres of wetlands and to recharge wetlands surrounding West Palm Beach’s well field, as well as to recharge a nearby residential lake system. Results of this study will be used to evaluate the similar plan for distribution of reclaimed waters from the planned West Miami-Dade Plant. The assumption is that conditions will be similar at the two locations. Advanced waste treatment is expensive both in capital costs and in operation and maintenance costs. Depending on the treatment technology used, anticipated capital and annual operation and maintenance costs are about $800 million and $84 million/year, respectively (Table 2-1; USACE and SFWMD  Tables 9-2 and 9-3), making this one of the costlier components of the Restoration Plan. Indeed, costs for the 1 MGD South Miami-Dade pilot plant are estimated at about $8.9 million capital costs and $645,000/year O&M costs for the membrane technology that meets the low required effluent levels (described below) (CDM, 2004). Costs could increase or decrease by the 2013 target for completion of the pilot project, including four years of assessment (USACE and SFWMD, 2003). Decreasing costs are possible as a result of improvements in membrane and related technologies that may occur in the intervening decades before implementation of this Restoration Plan component (NRC, 2004c). However, large cost reductions
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities (i.e., >50 percent by 2020) will not likely be achieved through incremental improvements in existing technologies, but will require novel technologies. The South Miami-Dade reclamation plan must wait on the outcome of its pilot project in 2013, and the West Miami-Dade plan must wait on the outcome of the West Palm Beach Pilot Project. In essence, the wastewater reclamation scheme already is a contingency plan, inasmuch as it will be implemented only in the likely event that more economical sources of water are not discovered during the courses of the pilot projects. Water-Quality Considerations Biscayne Bay was designated a priority water body by the Florida Legislature pursuant to the Surface Water Management and Improvement Act of 1987. The area south of Biscayne National Park is included in the Florida Keys National Marine Sanctuary. Waters of Biscayne Bay Aquatic Preserve and Biscayne National Park are classified as Outstanding Florida Waters (OFWs), and as such are subject to the most stringent regulations, including Florida antidegradation standards, which prohibit permitted discharges that will degrade ambient water quality. Because reclaimed water from the South Miami-Dade Waste Water Treatment Plant is considered “new” water (as opposed to surface runoff that might be diverted toward the bay), the plant discharge must meet the most stringent OFW criteria for the bay, even though plant discharge will reach the bay via discharge to the adjacent brackish wetlands, which are classified as State of Florida Class III waters. Because of these stringent regulations, the quality of reclaimed wastewater from the South Miami-Dade Plant is likely to substantially exceed the quality of ambient waters in the coastal marshes. The standards are compared in Table 2-4 (CDM, 2004) from which it is clear that the total nitrogen and total phosphorus standards for the Biscayne Bay OFW necessitate a very high level of treatment for the South Miami-Dade Waste Water Treatment Plant. This highly conservative approach regarding effluent quality will result in correspondingly high treatment costs. In the recent study by Camp Dresser & McKee (2004), reverseosmosis membrane technology was the only one sufficient to meet the rigorous total nitrogen and total phosphorus OFW criteria. Capital costs for this scheme—for the 1 MGD pilot plant project—are estimated by CDM at $8.9/gallon; in contrast, 1993 capital costs for most wastewater reclamation were much less, in the range of $200-1,500 per acre-foot or about $0.00061-0.0046/gal (NRC, 1993), because of the much-less stringent water-quality requirements. High costs are recognized in the Restoration Plan, with the caveat that costly reclamation will be used only if “…other, more appropriate sources are not available…” (USACE and SFWMD, 1999). “Other sources” might consist of surface drainage that could be diverted toward Biscayne Bay that would not have to meet the OFW criteria, only the Class III criteria for the coastal wetlands. But if the reclaimed wastewater from the South Miami-Dade Waste Water Treatment Plant is not used to supply fresh water to Biscayne Bay, the (lower) cost of reclamation will not be funded by the Restoration Plan, creating other financial issues. It is difficult to foresee a south Florida future in which the non-saline wastewater from a population of millions will not be required for at least a part of the water-supply needs of the region. Consideration should be given to revisiting or possibly appealing the decision to require the stringent total nitrogen and total phosphorus effluent standards for reclaimed wastewater that will first pass through brackish coastal wetlands before entering Biscayne Bay, in order to ensure the most responsible expenditure of Restoration Plan funds for wastewater reuse.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities TABLE 2-4 Comparison of Water Quality Criteria for South Miami-Dade WWTP Variable Raw Wastewater 1999-2004 SMDWWTPa Effluent Reuseb Class IIIc Biscayne Bay OFW Total Suspended Solids, mg/L 110 9.06 5 3.5 Biological Oxygen Demand 5, mg/L 110 5 5 12 Total Nitrogen, mg/L 40 18.4 3 0.27 Total Phosphorus, mg/L 1.09 1 0.005 Fecal Coliform, no./100 mL 55,385 2.2 2.2 2.2 a South Miami-Dade Waste Water Treatment Plant b State of Florida standards for reuse of reclaimed water and land application (Chapter 62-610, FAC): meet at a minimum secondary treatment and the requirements for public access irrigation with a TSS concentration of 5.0 mg/L or less, and high level of disinfection. c Chapter 62-611 FAC. All values taken from CDM (2004). SUMMARY AND COMPARISON The conventional reservoirs, ASR systems, in-ground reservoirs, and stormwater treatment areas included in the Restoration Plan will provide a total of approximately 5.5 billion acre-feet of new storage, of which approximately 4 billion acre-feet can be attributed to ASR systems (assuming 30% injection loss). Values listed in Table 2-1 can be used to compare major storage features in terms of storage capacity, costs, and land requirements. The main storage components can also be compared on the basis of sequencing, potential water quality impacts, and the degree to which the technology is proven and requires active operation (Table 2-5). Of the new storage that will be created by the Restoration Plan, conventional storage reservoirs have clear advantages of using proven technology and of requiring less active operation than water reuse or ASR. Overall, the sequencing of storage components makes sense considering questions related to engineering feasibility. The storage components that rely on proven technology, namely the surface reservoirs, are slated to be completed considerably earlier than those that require pilot projects, i.e., the ASR systems, the in-ground reservoirs, and seepage management using subsurface permeability barriers. In addition, most of the novel technologies are associated with potential water-quality impacts, which must be carefully evaluated prior to construction. However, because these latter components make up approximately 80 percent of the new storage provided by the Restoration Plan, the long lead time required for their evaluation and construction is a major constraint on the availability of water that could provide earlier environmental benefits. Although Table 2-1 provides information on costs for each component, more informative cost comparisons might be those that include consideration of the water-storage benefits provided by the components. Several such comparisons are shown in Figure 2-13, 2-14, and 2-15. These figures are only illustrative of the kinds of comparisons that can be made; not all projects in each storage category were used due to incomplete information on costs, and results would vary somewhat with a more complete data set. In Figure 2-13, construction and land acquisition costs are normalized by average annual outflows during the 31-year simulation period for each type of component. This comparison indicates that ASR systems are the most costly to site and
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities TABLE 2-5 Comparison of Selected Storage Components in Terms of Sequencing, Water Quality and Technology Characteristics STORAGE COMPONENT Construction Complete Water Quality Impacts Proven Technology? Passive/Active Operation Lake Okeechobee YES Intermediate Water Conservation Areas YES Relatively passive Conventional Surface Reservoirs YES Intermediate North Storage Reservoir (Kissimmee) 2013 + EAA Reservoirs 2014 - Upper East Coast Reservoirs+STAs+natural storage 2010 + ASRs - NO Very Active Lake Okeechobee ASR 2026 C43 Basin 2018 C51 ASR (North Palm Beach II) 2020 West Palm Beach ASR (N Palm Beach II, L-8 ASR) 2020 Central Palm Beach Reservoir ASR 2019 Site 1 Impoundment ASR (Hillsboro) 2017 Lake Belt Reservoirs 0 NO Intermediate North Lake Belt 2036 Central Lake Belt 2036 Seepage Management NO WCA3A/3B Levee Seepage Mgmt 2008 + Intermediate (some back-pumping) C11 Reservoir (part of 3A/3B seepage) L31-N Seepage Mgmt 2013 0 Passive Water Reuse + YES Very Active West Miami-Dade Water Reuse South Miami-Dade Water Reuse Note: Water quality impact key: + likely no negative impact, 0 unknown, - unresolved concern.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities construct. A similar normalization of operation and maintenance costs, illustrated in Figure 2-14, indicates that waste-water reuse incurs the highest annual costs, followed by ASRs. While ASR systems are the most expensive to site and build when compared on the basis of average annual outflow, they are probably the least expensive when compared on the basis of the maximum storage they can provide in a year, based on dividing the land and construction costs by the maximum difference between inflows and outflows in any year of the D13R simulations. This comparison is illustrated in Figure 2-15. The issue of providing ecological benefits as soon as possible has not been considered in the committee’s analyses in this chapter. Some approaches to considering that important matter are discussed in the following chapters. FIGURE 2-13. Construction plus land costs in 1999 dollars normalized by average annual acre-foot of outflow. Data taken from Table 2-1. The analyses represented in Figures 2-13, 2-14, and 2-15 are illustrative only. A fuller economic analysis might discount expenditures based on timing of costs and benefits, convert all costs (i.e., capital and O&M) to present value, and account for uncertainty. Conventional surface reservoirs are North Storage (Kissimmee) and EAA reservoirs only. ASRs represent C-51 (North Palm Beach II) and Lake Okeechobee ASR only. The graphs shown in Figures 2-13, 2-14, and 2-15 would change somewhat with more complete cost information.
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Re-Engineering Water Storage in the Everglades: Risks and Opportunities FIGURE 2-14. Operation and maintenance costs in 1999 dollars normalized by average annual acre-foot of outflow. Data taken from Table 2-1. FIGURE 2-15. Construction plus land costs in 1999 dollars normalized by maximum annual change in storage. Data taken from Table 2-1.
Representative terms from entire chapter: