Executive Summary

The Comprehensive Everglades Restoration Plan (CERP) is a framework and guide to restore, protect, and preserve the water resources of central and southern Florida, including the Everglades. It covers an 18,000-square-mile area, includes more than 60 elements, and will take more than 30 years to implement. It is designed to capture, store and redistribute fresh water previously lost to tide and to regulate the quality, quantity, timing and distribution of water flows. The need for water storage for the CERP has led to the proposal to drill over 300 aquifer storage and recovery (ASR) wells in south Florida (Figure 1). ASR is “the storage of water in a suitable aquifer through a well during times when water is available, and recovery of the water from the same well during times when it is needed” (Pyne, 1995). The CERP would use porous and permeable units in the Upper Floridan aquifer (UFA) to store excess surface water and shallow groundwater at rates of up to 1.7 billion gallons per day (bgpd) (6.3 million m3 per day) during wet periods for recovery during seasonal or longer-term dry periods.

ASR has advantages and disadvantages compared to surface storage. ASR systems generally require less land and may avoid water losses due to seepage and evapotranspiration. ASR wells can be located in areas of greatest need, thus reducing water distribution costs, and ASR permits recovery of large volumes of water during severe, multi-year droughts to augment deficient surface water supplies (USACE, 1999). Potential disadvantages of ASR wells include low recharge and recovery rates relative to surface storage, which limit capture rates of excess water, and losses due to mixing within brackish or saline aquifers (USACE, 1999). While slightly brackish water may be acceptable for drinking water, increases in salinity, and other water quality changes resulting from inputs of ASR water to surface ecosystems, may have unknown ecological effects. Operations and maintenance costs may also be higher for ASR, largely due to high energy requirements.

While ASR technology has been employed successfully in Florida since 1983, concerns have been expressed about the use of large-scale ASR in south Florida. Many of these concerns were outlined in a report prepared by the Aquifer Storage and Recovery Issue Team of the South Florida Ecosystem Restoration Working Group. These included suitability of proposed ASR source waters, paucity of regional hydrogeologic information, hydraulic fracturing of the aquifer, impacts on existing wells, water quality concerns, mercury bioaccumulation, and others. The Committee on Restoration of the Greater Everglades Ecosystem (CROGEE) held a workshop to examine two ASR pilot projects, and subsequently issued a report in 2001 that recommended additional research on regional science and water quality issues.

The ASR Regional Study, conceived just prior to the workshop, was designed to answer many of these questions concerning the feasibility of full-scale ASR implementation, reduce



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Regional Issues in Aquifer Storage and Recovery for Everglades Restoration Executive Summary The Comprehensive Everglades Restoration Plan (CERP) is a framework and guide to restore, protect, and preserve the water resources of central and southern Florida, including the Everglades. It covers an 18,000-square-mile area, includes more than 60 elements, and will take more than 30 years to implement. It is designed to capture, store and redistribute fresh water previously lost to tide and to regulate the quality, quantity, timing and distribution of water flows. The need for water storage for the CERP has led to the proposal to drill over 300 aquifer storage and recovery (ASR) wells in south Florida (Figure 1). ASR is “the storage of water in a suitable aquifer through a well during times when water is available, and recovery of the water from the same well during times when it is needed” (Pyne, 1995). The CERP would use porous and permeable units in the Upper Floridan aquifer (UFA) to store excess surface water and shallow groundwater at rates of up to 1.7 billion gallons per day (bgpd) (6.3 million m3 per day) during wet periods for recovery during seasonal or longer-term dry periods. ASR has advantages and disadvantages compared to surface storage. ASR systems generally require less land and may avoid water losses due to seepage and evapotranspiration. ASR wells can be located in areas of greatest need, thus reducing water distribution costs, and ASR permits recovery of large volumes of water during severe, multi-year droughts to augment deficient surface water supplies (USACE, 1999). Potential disadvantages of ASR wells include low recharge and recovery rates relative to surface storage, which limit capture rates of excess water, and losses due to mixing within brackish or saline aquifers (USACE, 1999). While slightly brackish water may be acceptable for drinking water, increases in salinity, and other water quality changes resulting from inputs of ASR water to surface ecosystems, may have unknown ecological effects. Operations and maintenance costs may also be higher for ASR, largely due to high energy requirements. While ASR technology has been employed successfully in Florida since 1983, concerns have been expressed about the use of large-scale ASR in south Florida. Many of these concerns were outlined in a report prepared by the Aquifer Storage and Recovery Issue Team of the South Florida Ecosystem Restoration Working Group. These included suitability of proposed ASR source waters, paucity of regional hydrogeologic information, hydraulic fracturing of the aquifer, impacts on existing wells, water quality concerns, mercury bioaccumulation, and others. The Committee on Restoration of the Greater Everglades Ecosystem (CROGEE) held a workshop to examine two ASR pilot projects, and subsequently issued a report in 2001 that recommended additional research on regional science and water quality issues. The ASR Regional Study, conceived just prior to the workshop, was designed to answer many of these questions concerning the feasibility of full-scale ASR implementation, reduce

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Regional Issues in Aquifer Storage and Recovery for Everglades Restoration uncertainties related to full-scale CERP ASR implementation by conducting scientific studies based on existing and newly acquired data, develop a regional groundwater model of the Floridan Aquifer System (FAS), and identify an appropriate magnitude of ASR capacity with minimal impact to the environment and existing users of the FAS. A fourth draft of the Project Management Plan (PMP) for the study (http://www.evergladesplan.org/pm/mgmtplns.shtml) was prepared by the USACE and the SFWMD in May 2002, and the Task Force requested that the CROGEE conduct a technical review of this document. To accomplish this task, the CROGEE formed a working group, composed of existing members of the committee and supplemented with special consultants. The PMP is organized primarily into a series of “technical tasks,” each having a budget, a timetable, subtasks, and a list of assumptions. The Executive Summary and Table of Contents of the PMP are in Appendix A of this report. Most of this report focuses on Chapter 3 of the PMP, which outlines the technical tasks. There is also considerable discussion of Appendix L, which contains many of the details of Tasks 10 through 13 (water quality and ecological studies). Overall, this report evaluates the draft PMP with respect to the adequacy of the proposed scientific methods to address key issues raised in the 2001 NRC CROGEE report and other issues previously raised by the ASR Issue Team. The Regional ASR PMP clearly responds to issues identified earlier by the South Florida Working Group ASR Issue Team and later by the CROGEE. The report recognizes the importance of acquiring information through the proposed Regional Study to resolve or better understand the issues that are involved with the consequences of implementation of ASR regionally in south Florida at the unprecedented scale of 1.7 billion gallons per day. The PMP goes a long way to providing the needed information. It is comprehensive, for the most part, and is integrated well with the pilot ASR studies. The authors of the document should be commended for the effort that went into producing the plan and for the comprehensiveness of the proposed study. The most important overall improvement to the document would be a greater attention to the CERP principle that “each incremental step [be] viewed as an experiment accompanied by one or more hypotheses that predict how that step will improve the system” (USACE, 1999), a concept generally termed adaptive management. Some of the task descriptions suggest that the study will be conducted as a relatively routine engineering exercise rather than a comprehensive and integrated scientific study to “investigate regional technical and regulatory issues governing the feasibility of full-scale ASR implementation…and develop tools to assess the feasibility and increase the level of certainty of successful ASR implementation,” which is the stated objective of the study. This structure is of some concern given that results of the regional study may show that ASR at the scale being proposed is not feasible due to hydrogeological, geochemical, ecological, or other reasons. In such cases, the proposed plans to (1) apply the model (or collect the sample), (2) collect the results, and (3) move on to the next task will not be appropriate. Additional advanced consideration is warranted concerning what to do if the results of some phase(s) indicate that ASR, as originally planned, will not work. The regional modeling described in Task 9 may come closest to this ideal; in this task the plan specifically discusses multiple model runs for a range of alternatives (in terms of well locations and numbers). Likewise, the flow chart of Figure 3, which shows “adaptive feedback” loops between water quality, ecological, and toxicological investigations, is a useful tool that might be more broadly applied elsewhere in the report. The PMP acknowledges the need for some flexibility in modification of the plan if early results warrant changes, and this is

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Regional Issues in Aquifer Storage and Recovery for Everglades Restoration commendable. However, the question remains whether the overall study plan will be sufficiently flexible to allow for evaluation of alternative plans/procedures if a particular aspect of the original plan is problematical. Articulation of specific hypotheses within the PMP is highly desirable, and this approach should be coupled with a plan that ensures evaluation of results in each step in a timely manner to assure flexibility and implementation of alternative procedures or approaches in place of those that are problematical or do not work. A moderate number of the tasks in the PMP are not described in enough detail to allow for a substantive critique of methods at this stage. While this is understandable given the scope of the effort, these include such important topics as tracer tests, numerical modeling, interpretation of bioassay results, packer test intervals, and sampling frequency. These topics deserve additional attention in later drafts. Ecological and water quality studies are described both in the descriptions of Tasks 10 through 13 and, somewhat independently, in Appendix L. Unfortunately, the task descriptions and the appendix are not well integrated, and sometimes appear contradictory. The writers of the PMP are urged to make these sections more consistent with each other. In addition to these general recommendations on the overall structure and organization of the PMP, recommendations related to more specific tasks of the Regional Study are as follows: The proposed additional monitoring at the pilot sites is a good step, but probably still does not go far enough in terms of numbers of wells and well nests to characterize both hydraulic and biogeochemical processes. Vertical and horizontal heterogeneity of the aquifer system will make this a difficult task that will require extensive testing. Likewise, recharge of the ASR wells should continue, if at all possible, until some time after the injection water is detected at all of the monitor wells, to understand the physical and chemical behavior of the system as fully as possible. Likewise, improved understanding of potential geochemical reactions should be a priority at all pilot sites. This may require additional monitoring during cycle testing beyond that anticipated in the PMP. Given the heterogeneity of the FAS with respect to salinity and physical properties at existing ASR sites, there may be significant variability in these properties from site to site. Some of the funds necessary to expand such monitoring and sampling should come through de-emphasizing continuous coring. While coring can be useful, it is costly and may yield unreliable and non-representative data. Given these limitations, it might be prudent to reduce the coring program and use the savings to support installation of additional monitoring wells for field tests of hydraulic properties and for hydrogeochemical characterization. Column studies are proposed to assess interactions between microorganisms and the subsurface materials. Due to the presence of fractures and other features in the Florida Aquifer system, it will be difficult, if not impossible, to obtain representative, quantitative information on transport using column studies. Such results should be treated with caution. The proposed bioassays and mesocosm studies emphasize response of individual taxa rather than community- and ecosystem-level effects. However, these studies may reveal only sublethal effects (e.g., altered growth rates) of contaminants on the sampled organisms. Such results would be difficult to extend to impacts on the larger ecosystem (e.g., shifts in community composition or changes in frequencies of algal blooms), for which little monitoring is proposed. Thus, the ASR Regional Study’s ecological monitoring and research components are poorly connected to the ecosystem- and community-level restoration objectives of CERP. This can be

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Regional Issues in Aquifer Storage and Recovery for Everglades Restoration remedied by adding monitoring and assessment of ecological indicators to the proposed bioassays of Task 13. In coordination with other CERP science initiatives such as RECOVER (REstoration Coordination & VERification), an opportunity exists to develop indicators that can be employed in both system-wide monitoring and the ASR Regional Study. The extended bioassay testing and monitoring of biological impacts are expected to occur over six- to twelve-month cycles. This sampling period may need to be longer to allow assessment of potential long-term effects on community composition, especially given interannual variability in factors such as rainfall, temperature, extreme events, etc. Surface water quality modeling and ecosystem modeling tends to focus on Lake Okeechobee. However, it appears more likely that negative effects of ASR-recovered water could occur within the Everglades itself. This is where surface waters are low in nutrients and dissolved solids, and where input, either directly or via pathways that include Lake Okeechobee, of recovered ASR water with relatively high ionic strength would represent a major ecological change. More emphasis should be placed on modeling of these more sensitive ecosystems and identifying water quality changes that could cause irreversible shifts in community composition.