5
Challenges in Restoring Water Quality

“Getting the water right” is a simple phrase that belies the inherent complexity of the overarching goal of the Comprehensive Everglades Restoration Plan (CERP). In Chapter 4, the committee discussed the challenges of water storage and distribution, and the necessity of making tradeoffs in the planning process to optimize the overall restoration benefits. Yet, water quality and water quantity are inextricably linked. Restoration planners cannot design projects to move large quantities of water south into the Everglades Protection Area to meet CERP goals without first ensuring that the water will meet established water quality criteria. Meanwhile, getting the water quality right has proven more difficult than originally imagined, and water quality has become a central technical, legal, and policy challenge that is affecting CERP progress.

In this chapter, the committee describes the legal context to water quality issues in the Everglades and analyzes the success of the water quality initiatives implemented to date. The committee also considers other possible water quality solutions and their cost implications. Water quality issues affecting aquifer storage and recovery (ASR) are not addressed in this chapter but are discussed briefly in Chapter 3.

PRE-DRAINAGE NUTRIENT CONDITIONS

Before construction of the canal and ditch networks began during the late 1900s, direct precipitation was the main source of water to much of the Everglades region. Although there are no water quality data extending back to that time, the general characteristics of the water quality can be reconstructed from measurements in the most interior sections of the marsh and from studies of the chemical composition of the dominant water sources. Recent hydroecological research, using a variety of methods including stable isotope analyses and chemical ratios (e.g., sulfate to chloride ratios), has demonstrated that under pre-drain-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 149
5 Challenges in Restoring Water Quality “Getting the water right” is a simple phrase that belies the inherent complex- ity of the overarching goal of the Comprehensive Everglades Restoration Plan (CERP). In Chapter 4, the committee discussed the challenges of water storage and distribution, and the necessity of making tradeoffs in the planning process to optimize the overall restoration benefits. Yet, water quality and water quantity are inextricably linked. Restoration planners cannot design projects to move large quantities of water south into the Everglades Protection Area to meet CERP goals without first ensuring that the water will meet established water quality criteria. Meanwhile, getting the water quality right has proven more difficult than originally imagined, and water quality has become a central technical, legal, and policy challenge that is affecting CERP progress. In this chapter, the committee describes the legal context to water quality issues in the Everglades and analyzes the success of the water quality initiatives implemented to date. The committee also considers other possible water qual- ity solutions and their cost implications. Water quality issues affecting aquifer storage and recovery (ASR) are not addressed in this chapter but are discussed briefly in Chapter 3. PRE-DRAINAGE NUTRIENT CONDITIONS Before construction of the canal and ditch networks began during the late 1900s, direct precipitation was the main source of water to much of the Ever- glades region. Although there are no water quality data extending back to that time, the general characteristics of the water quality can be reconstructed from measurements in the most interior sections of the marsh and from studies of the chemical composition of the dominant water sources. Recent hydroecological research, using a variety of methods including stable isotope analyses and chemi- cal ratios (e.g., sulfate to chloride ratios), has demonstrated that under pre-drain- 149

OCR for page 149
150 Progress Toward Restoring the Everglades age conditions, surface water and groundwater were relatively small components of the Everglades water inputs (see Table 4-1; Harvey and McCormick, 2009). The rainfall input is characterized by low ionic strength (median specific conductance of <20 microsiemens per centimeter [μS/cm]) and generally low concentrations of all major ions (i.e., largely <1 parts per million [ppm, or mil- ligrams per liter], except for sulfate and chloride, because of marine aerosol influences). Rain-fed areas of the Everglades (e.g., the interior of the Arthur R. Marshall Loxahatchee National Wildlife Refuge [LNWR]) have conductivities of <100 μS/cm. Rainfall is also notably low in nitrogen and phosphorus; estimates of phosphorus concentrations and loading in rainwater range from 30 parts per billion (ppb) (Davis, 1994) to more recent measurements of 9 to 10 ppb (Ahn and James, 2001; Richardson, 2008). Water quality data going back to 1978 show that the interior portions of the Water Conservation Areas (WCAs) and Everglades National Park are uniformly at or below 10 ppb total phosphorus (TP). Water samples taken between 1978 and 2003 in Everglades National Park have geometric mean TP concentrations of 4.5-5.6 ppb and geometric mean total nitrogen (TN) concentrations of 0.9-1.4 ppm (Payne and Weaver, 2004). A study conducted in 1953, prior to the intensive agricultural development of the Everglades Agricultural Area (EAA) but after con- struction of the major canals, showed “dissolved phosphorus” concentrations of 3–7 ppb in the Tamiami Trail canal and the lower portions of the canals bordering what is now WCA-3B, with concentrations about an order of magnitude higher in samples closer to Lake Okeechobee (Odum, 1953). In the absence of explicit data from the pre-drainage period, one can assume that the rain-driven system would have had similar water quality characteristics (i.e., low alkalinity, low total nitrogen and phosphorus concentrations) derived primarily from atmospheric deposition. Any phosphorus inputs from Lake Okeechobee overflows were gen- erally thought to have been assimilated by the former pond apple swamp that existed between the lake and the sawgrass plains (Noe et al., 2001). LEGAL CONTEXT FOR WATER QUALITY IN THE SOUTH FLORIDA ECOSYSTEM Water quality criteria and standards (see Box 5-1) in the South Florida eco- system are governed by a mix of federal and state statutes, implementing regula- tions, and judicial consent decrees. Current and proposed standards are fiercely contested, and active litigation in federal courts continues to create uncertainty as to which regulations will apply to future restoration plans. Because these criteria and standards have important implications for the CERP as it moves forward, the current legal and regulatory context is described in this section. Current standards, including designated uses and supporting criteria, are designed to limit the nutrient content of waters (especially phosphorus) flowing

OCR for page 149
Challenges in Restoring Water Quality 151 BOX 5-1 Definitions of Water Quality Criteria and Standards Regulatory documents commonly use the terms “standards” and “criteria.” The two terms are not synonymous. Water quality standards consist of three elements (EPA, 1998): 1) The designated use or uses of a water body or segment of a water body; 2) Water quality criteria necessary to protect the designated uses; and 3) An antidegradation policy. Classes of designated uses are defined by states. In Florida, those classes are defined in Florida Administrative Code (FAC) §§ 62-302.400 as: CLASS I—Potable Water Supplies CLASS II—Shellfish Propagation or Harvesting CLASS III—Fish Consumption; Recreation, Propagation and Maintenance of a Healthy, Well-Balanced Population of Fish and Wildlife CLASS III-Limited—Fish Consumption; Recreation or Limited Recreation; and/or Propagation and Maintenance of a Limited Population of Fish and Wildlife* CLASS IV—Agricultural Water Supplies CLASS V—Navigation, Utility, and Industrial Use Water quality criteria are of two forms, numeric and narrative. Numeric criteria are maximum acceptable concentrations of specific chemicals or acceptable ranges of other parameters such as temperature that will protect human health and aquatic life in a particular water body. Narrative criteria are qualitative statements such as those in FAC §§62-302.500 that all waters shall be free of substances that cause specified nuisance conditions and those that are acutely toxic. *The Class III-Limited designation was added by the state of Florida in August 2010 and still needs EPA review and approval. into Lake Okeechobee and the Everglades Protection Area. In general terms, one set of criteria was established for water quality within the Everglades and other standards set limits on the actual discharges of phosphorus into water bodies. The controlling federal statute is the Clean Water Act (CWA). It requires states to establish water quality standards that will support designated uses of waterways, and it establishes a permit program for discharges of wastewater and stormwater into receiving waters of the United States. Although rather stringent limits can be placed on point sources under authority of the CWA, nonpoint sources are not subject to the federal permit program. In 1987, the state of Florida exercised its authority to address nonpoint sources by adopting the Surface Water Improvement and Management (SWIM)

OCR for page 149
152 Progress Toward Restoring the Everglades program (Florida Statute Chapter 373.453). SWIM directed Florida’s water man- agement districts to develop and implement plans to clean up and preserve the state’s lakes, bays, estuaries, and rivers. SWIM also directed that the water management districts’ operations not “adversely affect indigenous vegetation communities or wildlife.” Thus, Florida set narrative regulatory criteria to ensure that phosphorus concentrations would cause “no imbalance in flora or fauna,” which is now formalized in Florida Administrative Code (FAC) 62-302.5301 (see also Rizzardi, 2001). Water Quality Standards for the Everglades Protection Area In 1988, the United States sued the state of Florida and the South Florida Water Management District (SFWMD), alleging that the state had failed to ade- quately clean up waters flowing into Everglades National Park (ENP) and LNWR (also known as WCA-1).2 After several years of litigation the parties entered into a settlement agreement in 1991 that was implemented by a Consent Decree in 1992. The 1991 settlement agreement contained several provisions, including • a general commitment on the part of the SFWMD and the Florida Depart- ment of Environmental Protection (FDEP) to protect water quality in LWNR and ENP, • adoption of interim and long-term total phosphorus limits,3 • certain remedial measures, • a research and monitoring program, and • contingencies for enforcement. Remedial measures included a commitment by the SFWMD to construct 35,000 acres of stormwater treatment areas (STAs) and an interim and long-term regula- tory program to require permits on all discharges from the EAA. Interim regula- tions for the EAA were to require a 10 percent reduction in phosphorus loads, Florida’s narrative water quality criterion for nutrients provides that “in no case shall nutrient 1 concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora or fauna.” (F.A.C. rule 62-302-530(47)(b)). United States v. South Florida Water Management District, 847 F. Supp. 1567 (S.D. Fla. 1992). 2 Interim limits for phosphorus were to be achieved by July 1997 (later amended to October 2003), 3 including annual flow-weighted concentration goals in Shark River Slough of no more than 14 ppb in a dry year and 9 ppb in a wet year. Long term limits were to be achieved by 2002 (later amended to 2006) including annual flow-weighted concentration goals in Shark River Slough of no more than 13 ppb in a dry year and 8 ppb in a wet year, and the long-term concentration limit for Taylor Slough and the Coastal Basins was set at 11 ppb. Interim and long-term limits for Everglades National Park and LNWR were specified by complex formulas in Appendices A and B of the Settlement Agreement. Interim levels for LNWR were to be between 8 and 22 ppb depending on water levels as measured.

OCR for page 149
Challenges in Restoring Water Quality 153 and the long-term regulations were to require source control efforts resulting in a 25 percent reduction. The state of Florida took action in 1994 to implement the primary features of the 1992 Consent Decree with enactment of the Everglades Forever Act (Fla. Stat. §373.4592). A crucial feature of the act directed the FDEP to develop numeric criteria for phosphorus within the Everglades Protection Area, defined as WCAs 1 (LWNR), 2A, 2B, 3A, and 3B, and Everglades National Park (FAC §§ 62-302.540). However, the Act provided that if no phosphorus criterion was adopted by the end of 2003, a 10 ppb criterion would automatically take effect in 2004 (see Fla. Stat. § 373.4592(10)). Scientific support for that criterion, added to the administrative code in July 2004, is discussed in Box 5-2. Modifications to the Consent Decree4 in 2001 deferred the compliance date for long-term phosphorus limits to 2006. The state of Florida amended the Everglades Forever Act in 2003 and formally adopted the revised phosphorus rule (FAC §§ 62-302.540).5 That rule states that for Class III waters in the Everglades Protection Area, the phosphorus criterion is a long-term geometric mean of 10 ppb, but not lower than natural conditions, taking into account temporal and spatial variability. Achievement of the criterion in Everglades National Park is governed by methods in Appendix A of the 1991 Settlement Agreement, and achievement of the criterion in the WCAs is evaluated across a network of sampling stations using a four-part test6 to determine whether a violation of Class III standards has occurred. Current methods for calculating values for Consent Decree compliance in LWNR and Everglades National Park, considering interannual variations in water levels, are described in the December 2009 report of the Technical Oversight Committee (SFWMD, 2009b). Several important changes were also made in the 2003 Everglades For- ever Act amendments. Long-term permit conditions were modified, and new “Technology-based Effluent Limitations (TBELs) established through Best Avail- able Phosphorus Reduction Technology (BAPRT)” were established to govern STA discharges (FAC §§ 62.302.540). Water-quality-based effluent limitations were held in abeyance until 2016. In addition, paragraph (6) allows net improvement as a moderating provision for “impacted” areas, where those areas are defined as being in the Everglades Protection Area with total phosphorus concentrations in the upper 10 centimeters of the soils greater than 500 milligrams per kilogram. See http://exchange.law.miami.edu/everglades/litigation/federal/usdc/88_1886/orders/2001_ 4 amend_ Settlement_Agreement.pdf. See also Miccosukee Tribe of Indians of Florida v. United States, 2008 WL 2967654 (S.D. Fla.). 5 The four-part test is used to assess compliance according to the following four provisions: (1) five- 6 year geometric mean is less than or equal to 10 ppb, (2) annual geometric mean averaged across all stations is less than or equal to 11 ppb, (3) annual geometric mean averaged across all stations is less than or equal to 10 ppb for three of five years, and (4) annual geometric mean at individual stations is less than or equal to 15 ppb (FAC §§ 62.302.540).

OCR for page 149
154 Progress Toward Restoring the Everglades BOX 5-2 Scientific Support for the 10 ppb Criterion The determination of the 10 ppb total phosphorus (TP) criterion was based on extensive research (McCormick et al.,1999; Payne et al., 2001, 2002, 2003; reviewed in Noe et al., 2001; Richardson, 2008). The data overwhelmingly demonstrate that even low levels of enrichment in total phosphorus concentrations result in elevated phosphorus in macrophyte tissues, soil, the water column, and periphyton, leading to undesirable changes in periphyton and macrophyte biomass and productivity and faunal communities. Under pre-disturbance conditions, isolation of the surface-water system from bed- rock meant that the only significant inputs of phosphorus were from atmospheric sourc- es, estimated to be in the range of 0.03 grams per m2 per year (Noe et al., 2001). In interior (undisturbed) portions of the Everglades, phosphorus concentrations in plant and periphyton biomass and in soil are very low compared to other wetlands and other peatlands, and the nitrogen:phosphorus ratios in these compartments suggest extreme phosphorus limitation, which Noe et al. (2001) ascribe to several factors, including • its occurrence on a limestone platform, which promotes removal and sequestra- tion of phosphorus through abiotic chemical reactions; • the very large spatial extent of the system, such that groundwater from other regional sources are isolated from all but the periphery of the system and most of the system receives the bulk of its nutrients from precipitation (ombrotrophic); • conservative cycling of phosphorus by the dominant macrophytes; • periphyton mats that maintain highly oxidized sediments, so that any phosphorus becomes adsorbed to iron minerals and is not bioavailable; and • the ability of Everglades plants (notably, Cladium, Eleocharis, and related spe- cies) to grow at unusually low tissue phosphorus concentrations. These changes were challenged by the Miccosukee Tribe in the U.S. Dis- trict Court as violating both the 1992 Consent Decree and the federal CWA. In July 2008, the court agreed that the changes (e.g., deferrals) violated the CWA, enjoined the FDEP from issuing any permits under the revised program, and ordered federal EPA to rigorously review the state program to ensure compliance with the CWA. The effect of this ruling was to effectively reinstate the 10 ppb rule and other features of the 1992 Consent Decree and the 1994 Everglades Forever Act. Subsequently, in April, 2010, the court reaffirmed that deferring compliance until 2016 violated federal law. New orders were issued for EPA to issue instructions to compel the state of Florida to comply with the 10 ppb crite- rion and for the State to complete new rulemaking to that effect in early 2011.7 Miccosukee Tribe of Indians of Florida v. United States of America, Lead Case No. 04-21448-CIV- 7 GOLD; Order Granting Plaintiffs’ Motions in Part; Granting Equitable Relief, Requiring Parties to Take Action by Dates Certain, April 14, 2010.

OCR for page 149
Challenges in Restoring Water Quality 155 Water Quality Standards for Lake Okeechobee and Tributaries Section 303(d) of the CWA requires that when a water body does not meet applicable water quality standards, the state or U.S. Environmental Protection Agency (EPA) must set numeric limits on point and nonpoint source discharges to assure that the water body will satisfy the standards. Following a 1999 Consent Decree,8 Florida enacted the Lake Okeechobee Protection Act in 2000 (Chapter 00-103, Laws of Florida), requiring limits on phosphorus inflows into the lake. FDEP developed and EPA approved a phosphorus total maximum daily load (TMDL) for Lake Okeechobee of 140 metric tons (mt) annually (105 mt from nonpoint surface runoff and 35 mt from atmospheric deposition; FDEP, 2001; Chapter 62-304, Laws of Florida). In addition, the rules prescribed a 40 ppb TP goal for the pelagic zone in the lake, and a target of 113 ppb was established for the lake’s tributaries, as recommended by FDEP, to provide protection of aquatic life within each tributary while maintaining consistency with the Lake Okeechobee TMDL (EPA, 2008a). The 113 ppb target was selected for the Lake Okeechobee tributaries as a numerical interpretation of Florida’s narrative criterion until a numeric criterion was developed. In March 2009 a group of environmental organizations filed suit challenging the EPA action and arguing that the “interim” TMDL violates the CWA.9 This case is pending. Statewide Numeric Limits for Nutrients Recent actions have been taken to establish statewide numeric criteria for nutrients (i.e., phosphorus and nitrogen) in Florida’s waters. In 1998 EPA for- mulated a national strategy for development of regional nutrient criteria (EPA, 1998). In doing so it cited evidence that nutrients were among the leading causes of impairment in rivers, lakes, and estuaries, and noted that 51 percent of lakes and 57 percent of the nation’s estuaries were impaired by over-enrichment of nutrients (EPA, 1996). At the time the only national criterion for nitrogen was a health-based limit for the protection of domestic water supplies, and the only national phosphorus criterion was based on “a conservative estimate to protect against the toxic effects of the bioconcentration of elemental phosphorus to estuarine and marine organisms.” That strategy was revisited in 2007 (EPA, 2007). A 2008 national status report on numeric nutrient criteria showed that 31 states had no numeric criteria for nutrients in lakes and reservoirs, 36 had none for rivers and streams, and half of the 24 states with estuaries had none (EPA, 2008b). See Florida Wildlife Federation v. Carol Browner, No. 4:98CV356-WS (N.D. Fla. Tallahassee 8 Div., April 22, 1998). Florida Wildlife Federation, et al v. The United States Environmental Protection Agency, Case 9 4:09-cv-00089-SPM-WCS (N.D. Fla.).

OCR for page 149
156 Progress Toward Restoring the Everglades FDEP began development of statewide numeric nutrient criteria in 2002, soon after reaching agreement with EPA on a plan for the process. A technical advisory committee was appointed and met 22 times between 2002 and 2010 (FDEP, 2009). A lawsuit over the lack of progress prompted EPA to intervene, and in August 2009, EPA entered into a phased Consent Decree to settle the suit.10 EPA committed to propose numeric nutrient criteria for lakes and flowing waters in Florida by January 14, 2010. Proposed criteria for lakes, flowing waters, springs, and South Florida canals were published in the Federal Register on Janu- ary 26, 2010 (75 FR 4174-4226). The approach and the criteria are summarized in Box 5-3. EPA intends to issue a final rule for lakes and flowing water (outside of South Florida) by November 15, 2010, and by August 2012 for estuarine and coastal waters and South Florida canals, unless Florida submits and EPA approves state numeric nutrient criteria before a final EPA action. The implications of the new statewide numeric nutrient criteria are uncer- tain at the time of this report, most importantly because the proposed criteria for lakes, flowing waters, springs, and canals are subject to change during the public comment period. Proposed criteria for estuaries are not scheduled for publication until 2011. Additional determinations will also be needed regarding which data are to be used in analyses and evaluated against the criteria. Proposed nutrient limits for South Florida canals (42 ppb TP, 1.6 ppm TN, 4 ppb chlorophyll a) could present yet another challenge to management of the system, depending upon how these criteria are enforced and how the Class III-limited designation (see Box 5-1) is applied. A requirement for all canals to achieve these nutrient concentrations would require significant changes in cur- rent nutrient control and treatment efforts at immense cost. Water Quality Standards: Attainability and Cost The CWA established water quality standards to protect aquatic life and human health without regard to available technology and the cost associated with attaining the standards. The cost of attaining and maintaining the standards may be considered during formulation and implementation of water quality management programs, but options for doing so are quite burdensome. As discussed later in this chapter, attaining water quality standards in the Everglades system may take decades of sustained effort at very substantial costs. In proposing numeric nutrient criteria for Florida, EPA requested comments on a possible new option, a “restoration water quality standard” for impaired waters that would enable the state to take incremental steps toward attainment Florida Wildlife Federation et al. v. Stephen L. Johnson and the U.S. Environmental Protection 10 Agency, No. 4:08-cv-324-RH-WCS (N.D. Fla.).

OCR for page 149
Challenges in Restoring Water Quality 157 BOX 5-3 EPA Proposed Numeric Nutrient Criteria for Lakes and Flowing Waters The U.S. Environmental Protection Agency (EPA) used correlations between nu- trients and biological response parameters to derive nutrient criteria for lakes using stressor-response models. EPA concluded that relationships between nutrients and chlorophyll-a in Florida’s rivers and streams were affected by so many variables that derivation of reliable criteria using models was not possible. EPA chose instead to use the statistical distribution-reference site approach for those water bodies as the bet- ter basis for setting criteria. Numeric criteria were also derived for springs and clear streams. They were derived from laboratory and field investigations that supported development of a dose-response model for nuisance algal and periphyton responses to doses of nitrite and nitrate nitrogen. Criteria for canals in South Florida were derived using the statistical distribution approach (see 75 FR 4174-4226 and EPA [2010] for more details). Proposed criteria for the Peninsula watershed region, which includes the Caloosa- hatchee, St. Lucie, and Kissimmee watershed, are instream limits of 0.107 ppm for total phosphorus (TP) and 1.205 ppm for total nitrogen (TN) based on an annual geometric mean not to be surpassed more than once in a three-year period. In addition, the pro- posed criteria state that the long-term average of annual geometric mean values shall not surpass the listed concentration values. The 10 ppb TP criterion for the Everglades Protection Area was not affected by the proposed rule. A protective TN and TP load for Lake Okeechobee also was not calculated, because a total maximum daily load (TMDL) is in effect for TP. Numeric criteria for canals in the South Florida bioregion were proposed as 42 ppb TP, 1.6 ppm TN, and 4 ppb chlorophyll a (75 FR 4174-4226). Criteria for canals are applicable to all Class III canals in the South Florida bioregion as shown in Figure 5-1 except for canals within the Everglades Protection Area, where the TP criterion of 10 ppb currently applies. FIGURE 5-1 South Florida bioregion. SOURCE: ftp.epa.gov/wed/ecoregions/fl/fl_eco_lg.pdf. Figure 5-1.eps bitmap

OCR for page 149
158 Progress Toward Restoring the Everglades of permanent standards over a stated time period. EPA provided an example of an interim standard that would require progress during years 1-5, a more stringent interim standard during years 6-10, and attainment of the permanent standard beginning in year 11 (EPA, 2010). That particular option would not be applicable to the phosphorus standard in the Everglades Protection Area, which is explicitly excluded under EPA’s current proposal for Florida. Implementing a similar strategy in the Everglades Protection Area would require significant changes to existing policy. The CWA offers to states two options to address an unattainable standard, namely the use of attainability analysis and discharge-specific variances, neither of which may be appropriate to the Everglades ecosystem. A state can remove a designated use, other than an existing use, if it can demonstrate through a formal use attainability analysis that attaining the standard is not feasible for one of several reasons, including cost and widespread economic impacts. When implementing changes through a use attainability analysis, a designated use for a particular water body is changed, not the criteria applicable to the original class of uses. Because criteria are specific to designated uses, however, a change in use may trigger a change in applicable criteria. In August 2010, FDEP amended FAC Rules 62-302.400 and 62-302.530 to refine the existing surface-water classification system, creating a new sub-classification of waters, Class III-Limited would applicable to wholly artificial waters or altered waters: Thus, a new set of criteria applicable to the new class of waters will have to be established. The implications of this change for water quality management in the Everglades system are not clear at this time. Discharge-specific variances, normally applied to municipal and industrial point source discharges, have not been applied to discharges from permitted sources within the Everglades and are therefore an untested option. Under Florida rules, an affected party may also petition for site-specific alternative criteria (SAC) when “a water body, or portion thereof, may not meet a particular ambient water quality criterion specified for its classification, due to natural background conditions or man-induced condi- tions which cannot be controlled or abated” (FAC 62.302.800). No such petition has been requested for phosphorus in the Everglades Protection Area (E. Marks, FDEP, personal communication, 2010). TOWARD A SYSTEMWIDE PHOSPHORUS BUDGET Phosphorus is the primary nutrient of concern in the Everglades system. Therefore, it is especially important that the storage and transport of phosphorus through the system be understood in considerable detail if water quality concerns are to be addressed effectively and comprehensively.

OCR for page 149
Challenges in Restoring Water Quality 159 Stored Phosphorus in the South Florida Ecosystem Phosphorus retention is an important function in basin nutrient cycling. Phosphorus can be stored over the short term in above- and below-ground plant tissues, microorganisms, periphyton, and detritus. Over the long term, phosphorus can be stored in inorganic and organic soil particles and organic matter. The fate of phosphorus in these long-term storage compartments needs to be considered in any comprehensive water quality management approach. In the Lake Okeechobee basin, Reddy et al. (2010) estimated TP storage in upland and wetland soils to be 215,000 mt.11 Approximately 80 percent of the stored phosphorus (or 169,800 mt) is located in soils and stream sediments, with the remainder stored in lake sediments in the Upper Chain of Lakes, Lake Istokpoga, and Lake Okeechobee. Reddy et al. (2010) performed a thought experiment that illuminates the long-term role of stored (or legacy) phosphorus on loading to Lake Okeechobee. Based on chemical extraction tests, they assumed that approximately 35 percent of the phosphorus stored was stable (i.e., not able to be released) because it was not soluble either in acid or base or both. Reddy et al. (2010) conservatively esti- mated that 10 to 25 percent of the reactive phosphorus in the soils was available to be exported from the system (see Figure 5-2). Given estimates of phosphorus leaching rates from stored phosphorus in the Lake Okeechobee basin of 500 mt per year (estimated based on assessments of long-term phosphorus discharges into Lake Okeechobee) and the estimates of stored reactive phosphorus, legacy phosphorus could maintain a phosphorus load to the lake of 500 mt per year for the next 22 to 55 years. This loading rate only considers legacy phosphorus stored in the soils and sediments and does not take into account new phosphorus additions in the basin. A recent report suggests that 11,000 mt of phosphorus is currently imported annually into the basin, and 6,700 mt is exported out of the basin, resulting in 5,300 mt net phosphorus accumulation in the system (SFWMD, 2010b). Internal loads from sediments in Lake Okeechobee to the water column are also significant, especially from the mud zone sediments. These sediments are fine grained and are readily suspended into the water column. Based on several earlier research reports, internal flux from mud sediments to the water column was estimated at 112 mt of phosphorus per year. Based on the available reactive phosphorus in the sediments (using the assumptions described above), this supply will continue for 12 to 31 years (Figure 5-2). Managing internal load through chemical amendments may not be cost-effective considering the size of One metric ton equals 2,200 pounds. 11

OCR for page 149
194 Progress Toward Restoring the Everglades BOX 5-4 Sources of Sulfur in the Everglades There have been few studies on the sources of sulfate to the Everglades (Wright et al., 2008; Gabriel, 2009). Potential sources include atmospheric deposition, deep groundwater, and sulfur supplied from the Everglades Agricultural Area (EAA). Inputs of atmospheric sulfate deposition are small compared to fluxes in canals. Therefore, atmospheric deposition is a limited component of sulfate contamination in the Ever- glades. Deep groundwater exhibits high sulfate concentrations and could potentially be an important source of sulfate. However, deep groundwater is not geochemically consistent with canal water, and it is not thought to be an important source. There have been few mass balances of sulfur for the Everglades. Schueneman (2001) concluded that Lake Okeechobee and soil mineralization (the degradation of soil organic sulfur) were the largest sources of sulfate to the Everglades. Gabriel (2009) conducted a pre- liminary mass balance of sulfur for Lake Okeechobee, the EAA, Water Conservation Area (WCA)-1, and WCA-2 for wet (2004), dry (2007), and intermediate (2003) years. His analysis showed that atmospheric deposition was a small input, and evasion of reduced sulfur gases was a minor loss. During the intermediate and wet years, Lake Okeechobee was a net source of sulfate. The WCAs were generally net sinks for sulfate inputs. Based on canal water fluxes, the EAA was a large net source of sulfate during the wet and intermediate years and a slight sink during the dry year. Gabriel’s analysis suggests that soil sulfur mineralization and direct agricultural application were important sulfur sources for the EAA and the annual harvest of sugar cane was an important sulfur loss. Although soil sulfur oxidation is clearly an important source of sulfate to down- stream drainage waters, relatively little is known about controls on this source and how it has varied over time. Using sulfur stable isotope measurements, it appears that sulfur applied for agriculture is a major contributor to the excess sulfate concentrations in the Everglades (Bates et al., 2002). However, the relative contribution of recent vs. legacy sulfur additions to sulfate concentrations in the Everglades is not clear. (<10-20 ppm) methylation is sulfate limited (Figure 5-15), and under these condi- tions increases in sulfate will stimulate methylation of ionic mercury (Gilmour et al., 2009). This sulfate-limited condition coincides with sulfide concentrations below 0.2-0.3 ppm in sediment porewaters. At high concentrations of surface- water sulfate (>10-20 ppm) and/or high concentrations of sulfide (>0.2-0.3 ppm), production of methyl mercury becomes curtailed because of immobilization of ionic mercury by sulfide (Benoit et al., 2003). In the northern Everglades the high supply of sulfate coupled with reducing conditions result in high concen- trations of sulfide in wetland porewaters (often exceeding 1 ppm), which may limit methyl mercury concentrations (Scheidt and Kalla, 2007). With decreases in sulfate and sulfide concentrations there is an increase in methyl mercury pro- duction rate in WCA-2B and -3A with subsequent decreases through Everglades National Park toward the south (Gilmour et al., 2007). An additional factor that may influence the spatial patterns in fish mercury

OCR for page 149
Challenges in Restoring Water Quality 195 FIGURE 5-15 Conceptual diagram showing the response of methylation of mercury to varying sulfate con- centrations. At low concentrations of sulfate, methylation is stimulated; at higher sulfate concentrations, the production of high concentrations of sulfide inhibits methylation. Figure 5-15.eps bitmap SOURCE: Modified from Gilmour et al. (2009). in the Everglades is phosphorus supply. Water concentrations of phosphorus exhibit a distinct decreasing gradient north to south due to inputs from the EAA (Scheidt and Kalla, 2007). This elevated supply of phosphorus increases aquatic productivity, which may result in “biodilution” of fish mercury (Pickhardt et al., 2002; Chen and Folt, 2005). However, it does not appear that this hypothesis has ever been tested for the Everglades. The Everglades mercury problem arises from the convergence of two con- taminant sources (mercury and sulfate). Ecosystem-wide sampling indicates that zones of elevated methyl mercury production appear to be controlled by sulfate transport, which varies in time and space. Increases in water discharge since

OCR for page 149
196 Progress Toward Restoring the Everglades the mid-1990s appear to have increased sulfate transport southward, resulting in mercury contamination in the southern portions of the Everglades (Krabbenhoft et al., 2009). Possible Approaches to Decrease Sulfur Contamination and Research Needs Previous mass balance studies have demonstrated the importance of the EAA as a major source of sulfate to the Everglades. Transport of sulfate south- ward largely occurs via canal discharge. To date there has been limited effort to control or restrict sulfate contamination in the Everglades. Watershed BMPs could be implemented in the EAA to decrease sulfate loads. Recently, Ye at al. (2009) found that rates of sulfur application commonly used in the EAA do not significantly decrease the pH of soils and may not be effective in enhancing the availability of phosphorus. Application of sulfur could be limited in the EAA to the minimum quantity needed for sustained crop yields. Sulfur application (e.g., gypsum [CaSO4] for pH adjustment, sulfur based fungicides, sulfur containing fertilizers) could also be minimized. An opportunity to mitigate sulfur contamination may result from the pur- chase of land in the EAA from the U.S. Sugar Corporation. Taking EAA land out of cultivation should decrease both land application of sulfur and soil oxidation of sulfur associated with soil mineralization, limiting two of the most impor- tant sources of sulfate to the Everglades. The initial flooding of lands that were formerly in agriculture could likely result in a very large flux of phosphorus, sulfate, mercury, and other contaminants in drainage waters, creating a short- term environmental problem. If EAA soils are re-wetted, detailed monitoring should be conducted to characterize the extent of this disturbance. However, over the long-term prolonged flooding and saturation of soil should stimulate the accumulation of soil carbon and reducing conditions and limit the mobili- zation of sulfate. Restoration of sheet flow within the Everglades ecosystem will help pro- tect sensitive areas like the WCAs, Everglades National Park, and Big Cypress National Park from the effects of sulfate contamination. Canals promote distant transport of sulfate under oxidizing conditions. The re-establishment of sheet flow should promote sequestration of sulfur (as sulfide) under more reduced conditions and should decrease the transport of sulfate. STAs have not been designed to remove sulfate, and, in fact, monitoring data suggest that STAs have limited effectiveness in removing sulfate. Research could be conducted to investigate how STAs can better remove sulfate, within the context of the primary objective of removing phosphorus. Possible approaches might include increasing the hydrologic residence time in STAs, using plants

OCR for page 149
Challenges in Restoring Water Quality 197 that are more effective in sequestering sulfur, and using chemical amendments such as iron. It appears that some planned hydrologic improvements in the CERP may have the undesired consequence of enhancing transport of sulfate to the south- ern more pristine portions of the Everglades, increasing mercury contamination in these areas. For example, within the proposed eastern flow-way, water from WCA-2 is transferred to Lake Belt storage areas prior to discharge into Everglades National Park south of Tamiami Trail. As a consequence, increasing (or changing) discharge patterns without considering associated water quality may exchange one problem for another. CALCIUM, ALKALINITY, AND SPECIFIC CONDUCTANCE The related issues of the supply of calcium concentrations, alkalinity, and specific conductance in the water quality of the Everglades have received some attention, but they may deserve more careful consideration as factors in eco- system restoration. The effects of elevated conductivity on native vegetation and the implications of changing calcium concentrations on phosphorus are discussed below. Effects on Wetland Biota Waters draining the Everglades are thought to be historically soft. Harvey and McCormick (2009) found that the development of thick, low-hydraulic- conductivity peats isolated surface water and shallow groundwater from deep groundwater with higher ionic strength. In the northern portions of the Everglades Protection Area (i.e., LNWR, WCA-2), water near the perimeter canals is elevated in specific conductance, with values in the range of 1,000 μS/cm (Surratt et al., 2008; Harvey and McCor- mick, 2009). Canal water discharging into the LNWR has specific conductance values up to two times greater than interior waters (231.5 μS/cm vs. 121.8 μS/ cm) (USFWS, 2009e). This condition creates a zone of elevated surface-water specific conductance extending up to 2.8 miles into the LNWR and is associ- ated with the absence of yelloweyed grass (Xyris spp.), a key indicator plant for undisturbed communities. The conductivity of water in the interior of WCA-2A is generally in the range of 1,000 μS/cm; in contrast, within Everglades National Park, specific conductances are rarely above 600 μS/cm, despite thin peat and greater surface water-groundwater exchange in that region. The input of waters with high concentrations of cations from the EAA into the northern WCAs has been demonstrated in spatial analyses of calcium concentration in the soil (Rivero et al., 2007) and occurred as far back as the 1940s.

OCR for page 149
198 Progress Toward Restoring the Everglades There is some evidence to indicate that elevated mineral content in the surface waters of the areas receiving canal waters from the EAA may have sig- nificant impacts on the ecology of these areas. Experimental work suggests that some characteristic species, including Rhynchospora spp., Xyris smalliana., and Eriocaulon aquaticum germinate and grow better under unenriched (low cal- cium, phosphorus) conditions and are typically found only in softwater areas (R. Gibble, USFWS, and P. McCormick, SFWMD, personal communication, 2009). In northern peatlands, species’ distributions are well known to be strongly influ- enced by calcium concentrations (Glaser, 1992; Bridgham et al., 1996; Payette and Rochefort, 2001), with large changes in plant community composition as calcium concentrations decrease below 10 ppm. However, the role of calcium in Everglades plant ecology has received very little attention, and so it is not clear whether the patterns observed in the northern peatlands is relevant here. There is stronger evidence that periphyton communities are altered by changes in water hardness. Swift and Nicholas (1987) showed that calcium- enriched waters affected by canal and agricultural drainage had a lower overall diversity of algae and cyanobacteria than the softwater interior-marsh sites and were dominated by filamentous cyanobacteria and other characteristic “pollu- tion indicators,” in contrast to the desmid and acid-preferring species of diatoms found in the softwater sites. Harvey and McCormick (2009) reported similar results in the LNWR. Paleoecological data (Slate and Stevenson, 2000) show that diatom species preferring acidic conditions were more widespread in the pre-drainage Everglades than currently. Contemporary data also show that cal- careous communities are more common in the more minerotrophic waters of the southern Everglades. Studies of food web relationships suggest that a transition from the diatom-desmid community to a calcareous community has effects on fish species and food web structure (Williams and Trexler, 2006), although these authors found that the dominant detritivores appear to be feeding on a mixture of periphyton species from both diatoms and cyanobacteria. Calcium Trends and Implications In contrast to the pattern of elevated calcium and alkalinity observed in the WCAs in association with inputs from the EAA, Lake Okeechobee has shown trends of decreasing calcium concentrations since the 1970s (Figure 5-16). Cal- cium concentrations in the lake have decreased from 45-50 ppm in the 1970s to 30-35 ppm in 1999, a trend correlated with a slight decrease in pH and alkalinity and an increase in temperature. This pattern is likely due to a decrease in back-pumping of calcium-enriched water from the EAA and a trend toward wetter conditions, which lead to lower concentrations of lake calcium (Walker, 2000; Zhang et al., 2007).

OCR for page 149
Challenges in Restoring Water Quality 199 FIGURE 5-16 Monthly average values of (A) calcium, (B) specific conductivity, and (C) sulfate Figure 5-16.eps at eight long-term monitoring stations in Lake Okeechobee. bitmap SOURCE: Zhang et al. (2007).

OCR for page 149
200 Progress Toward Restoring the Everglades The role of calcium in the lake is strongly linked to the fate of phosphorus, as 58-70 percent of the phosphorus accumulating in the bottom sediments is bound to calcium and magnesium, and the fraction of phosphorus in the benthic sediments that is bound to calcium also shows a decreasing trend (Walker, 2000). The settling rate of phosphorus in the lake is strongly correlated with calcium concentrations (Figure 5-17), so decreasing inputs of calcium to the lake results in higher quantities of total phosphorus maintained in the lake water column. Calcium loading would appear to be an important component of the phosphorus management of the lake (Walker, 2000). This mechanism is likely associated with precipitation of calcium carbonate and the immobilization of phosphorus by sorption and flocculation. Precipitation of calcite likely facilitates the removal of turbidity, but long-term declines in calcium carbonate precipitation could enhance the persistence of phosphorus and turbidity in the lake. Changes in the dynamics of calcium may also have implications for the long-term success of the STAs. Short-term immobilization of phosphorus in the STAs seems to occur by biological removal by periphyton and macrophytes and FIGURE 5-17 Relationship of phosphorus settling rate in Lake Okeechobee to calcium con- centration in the water column, based on data from 1973 to 1999. Figure 5-17.eps SOURCE: Walker (2000). bitmap

OCR for page 149
Challenges in Restoring Water Quality 201 particulate settling. However, over the longer term it is likely that immobilization by calcium is important. STAs exhibit net retention of alkalinity, probably largely as a result of calcite precipitation (W. Walker, consultant, personal communica- tion, 2009), and phosphate is readily co-precipitated with calcite (Wetzel, 2001; Reddy and Delaune, 2008). Walker (2009) reported outflow TP concentrations from the STAs that were highly correlated with inflow calcium concentrations, showing the importance of calcium as a control on water column TP. Long-term decreases in the inflow of calcium to STAs associated with changes in agricul- tural activities in the EAA will likely decrease the formation of calcite and may limit associated immobilization of phosphorus. Research Needs This brief review suggests that calcium and alkalinity may play a larger role in controlling both phosphorus management and the composition of the biota than has been previously recognized. It is important to determine the extent to which changes in conductivity alone, separately from phosphorus enrichment, cause undesirable changes in both the periphyton mat and in the macrophyte communities. In addition, research should be directed toward understanding the co-variation and dynamics of conductivity and other pollutants (phospho- rus, sulfate) to verify the suggested utility of conductivity alone as an indicator of polluted water impact (Harwell et al., 2008; Surratt et al., 2008). Most of the research on the extent and impacts of high-conductivity water on plant and periphyton communities has been done within the LNWR; it is important to understand the extent of impact of high-conductivity canal waters on other receiving areas. Finally, the potentially important role of calcium as a control on phosphorus chemistry both within Lake Okeechobee and the STAs deserves further attention, as tradeoffs in water quality management may be necessary. CONCLUSIONS AND RECOMMENDATIONS Ten years after the CERP was launched, “getting the water right” is proving to be more difficult and expensive than originally anticipated. It has taken decades (more than 60 years) for the ecosystem to degrade to its current state, and it will likely take a similar timeframe or longer to restore. Legacy phosphorus storages in the Lake Okeechobee watershed, the lake itself, and the EAA suggest that cur- rent phosphorus release rates into the system will persist for decades. Attaining water quality goals throughout the system is likely to be very costly and take several decades of continued commitment to a systemwide, integrated planning and design effort that simultaneously addresses source controls, storage, and treatment over a range of timescales.

OCR for page 149
202 Progress Toward Restoring the Everglades Additional information on phosphorus mass balances, particularly within the EAA, are needed to support effective decision making. NRC (2008) recom- mended a systemwide accounting for phosphorus and other contaminants such as sulfur, nitrogen, calcium, and mercury, and this remains a pressing need. There are notable gaps in the published phosphorus budgets between Lake Okeechobee and the inflows to the STAs and also in the contributions from atmospheric deposition for phosphorus and other elements. The lack of informa- tion synthesis of inputs and pathways of phosphorus and other contaminants in key areas, such as the Everglades Agricultural Area, hinders the development of targeted strategies to improve water quality management. The current acreage of STAs, as managed, is not sufficient to treat exist- ing water flows and phosphorus loads into the Everglades Protection Area. Although new construction of STAs is underway in Compartments B and C, these STAs are located far from where the recent Consent Decree violations have occurred. With increased volumes of water planned for the CERP, substantially more water quality treatment and/or additional load reductions will be needed if the new flows are to meet the water quality criteria. If these new CERP loads are addressed with STAs alone, an estimated 54,000 additional acres of STAs will be required, costing approximately $1.1 billion to construct, $27 million per year to operate and maintain, and approximately $1.1 billion to refurbish every 20 to 25 years (2010 dollars). Additional STAs will further increase the large cost of restoration (last estimated at nearly $13 billion) and add to the fiscal challenges of federal and state agencies, although additional source control measures could reduce the magnitude of this cost increase. EPA’s recently announced phospho- rus and nitrogen water quality standards for lakes, rivers, and canals introduce additional technical and financial challenges. The SFWMD should complete a comprehensive scientific, technical, and cost-effectiveness analysis as a basis for assessing potential short- and long-term restoration alternatives and for optimizing restoration outcomes given state and federal financial constraints. This analysis is needed to facilitate management decisions that focus on improving systemwide water quality, bringing the water- shed into compliance with the Lake Okeechobee TMDL, and addressing recent violations of the Consent Decree. In addition to considering additional treat- ment and source control, this analysis should evaluate urban and agricultural water supply management approaches and accelerated sequencing for seepage management projects to determine whether changes could address water quality and water quantity concerns in a more efficient manner. A rigorous research, analysis, and modeling program is needed to develop improved best management practices and to examine the long-term sustain- ability and performance of STAs to meet the desired outflow water quality. To

OCR for page 149
Challenges in Restoring Water Quality 203 support the comprehensive scientific, technical, and cost-effectiveness analysis recommended above, additional research is needed in the following areas: • STA sustainability and performance. The SFWMD’s extensive STA soil and water quality monitoring program should be supported by a systematic research program that evaluates the long-term ability of STAs to sustain or improve upon their current level of functioning. Further research should examine the biogeo- chemistry, vegetation dynamics, and hydrology of the STAs, and should couple the resultant data with predictive models to improve performance and support management decisions. Useful improvements could also be realized through an external peer review of the STA research and monitoring program, including the design criteria and modeling efforts. • Source control effectiveness. A rigorous research, monitoring, and mod- eling program focused on developing improved BMPs is needed to improve the efficiency of phosphorus source control efforts and to inform systemwide phos- phorus management decisions. Long-term monitoring of the efficacy and costs of BMP implementation across multiple sites will be required to evaluate source control practices across variable hydrologic, geomorphologic, and soil regimes present in the South Florida ecosystem and to validate and build confidence in predictive models. Given that restoration as originally envisioned in the CERP remains decades away and the ecosystem continues to decline, CERP agencies should conduct a rigorous scientific analysis of the short- and long-term tradeoffs between water quality and quantity for the Everglades ecosystem. The committee does not endorse such tradeoffs at this time, because scientific analyses to explain the repercussions of such decisions are lacking. However, the scientific analysis of potential tradeoffs is critical to inform future water management decisions, including the prioritization of projects. In particular, the analysis should address the following questions: • What are the short- and long-term consequences of providing too little water to the Everglades ecosystem but maintaining sufficient quality? • What are the short- and long-term consequences of providing water of lower quality to the Everglades ecosystem but maintaining sufficient flows? • Are the negative consequences reversible, and if so, within what timeframes? Effective water quality management would be best served by consideration of a multi-contaminant approach in the future. Water quality conditions in the Everglades are affected not only by the input of contaminants, but also by the

OCR for page 149
204 Progress Toward Restoring the Everglades inputs of other elements that alter their behavior. For example, the bioavail- ability of mercury and its accumulation in fish and other wildlife appears to be controlled not only by inputs of mercury, but also by the supply of sulfate, phosphorus, and dissolved organic carbon. Likewise the transport and removal of phosphorus may be coupled with the supply of calcium in Lake Okeechobee, the STAs, and other portions of the Everglades. Additional research is also needed to clarify the linkages between water quality constituents to support sound multi- contaminant water management decisions.