Review of the Everglades Aquifer Storage and Recovery Regional Study (2015)

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Introduction

The Florida Everglades, a unique aquatic ecosystem that supports a diversity of habitats and 67 threatened and endangered species, has been greatly altered over the past century by water management to provide flood control, increase urban water supply, and enhance agricultural production. The remnant Everglades ecosystem now competes with urban and agricultural interests for available water and is impaired by contaminants from these two activities. The Comprehensive Everglades Restoration Plan (CERP), launched in 2000, is a joint effort led by the state and federal government to reverse the decline of the ecosystem. The CERP is designed to capture, store, and redistribute freshwater and to improve the quality, quantity, timing, and distribution of water flows. To “get the water right” and restore the Everglades, there is a critical need for new water storage because 130 years of canal drainage and water management have resulted in extensive losses of natural storage. Thus, in addition to surface reservoirs, the CERP included a project that would drill over 330 aquifer storage and recovery (ASR) wells (Figure 1-1). The CERP feasibility study proposed that up to 1.7 billion gallons per day could be stored in porous and permeable units in the Upper Floridan aquifer during wet periods for recovery during seasonal or longer-term dry periods.

ASR PILOTS TO ADDRESS UNCERTAINTIES

Although ASR technology has been employed successfully in Florida since 1983, concerns were expressed about this large-scale application of ASR in the Everglades. The South Florida Ecosystem Restoration Working Group’s ASR Issue Team (1999) identified seven technical issues in need of further examination before ASR should move forward:

1. Suitability of prospective source waters considering spatial and temporal variability in water quality,
2. Characterization of the regional hydrogeology of the Upper Floridan aquifer,
3. Understanding the potential for rock fracturing,
4. Site and regional changes in head and patterns of groundwater flow,
5. Water quality changes during movement and storage in the aquifer,
6. Effects on mercury methylation and bioaccumulation in the Everglades ecosystem, and
7. The relationship between hydrogeologic properties and recovery and recharge volumes.

FIGURE 1-1 Generalized ASR well locations from the original CERP plan for 333 wells. SOURCE: USACE and SFWMD (2014).

The U.S. Army Corps of Engineers (USACE) and the South Florida Water Management District (SFWMD) originally planned five pilot studies (Figure 1-2) to address these concerns—three ASR pilot sites around Lake Okeechobee (Kissimmee River, Port Mayaca, and Moore Haven), one at the Hillsboro Canal, and one at the Caloosahatchee River. All pilots were authorized, but due to limitations in funding and poor site conditions at the Caloosahatchee River site, only two pilot sites (Kissimmee River and Hillsboro) were ultimately constructed. The Hillsboro and Kissimmee River ASR pilot studies (USACE and SFWMD, 2013) examined water quality changes, local hydrogeology, recharge and recovery performance, effects on hydraulic head and local groundwater flow, costs, and energy use at these two sites, each with a single ASR well and several monitoring wells. Additionally, surface water and groundwater quality measurements were conducted at the proposed Caloosahatchee River and Port Mayaca sites.

After the National Research Council (NRC) Committee on the Restoration of the Greater Everglades Ecosystem held a workshop to examine plans for the two ASR pilot projects, NRC (2001) recommended additional research on regional science and water quality issues, including

• Aggregate hydraulic effects in a regional context,
• Performance under long (> 1 year) recharge periods,
• Subsurface geochemical changes, and
• Ecotoxicological effects on downstream receptors.

To respond to these recommendations, the USACE, in cooperation with the SFWMD, launched the ASR Regional Study to complement the site-specific ASR pilot studies. The Regional Study was designed to address uncertainties concerning the feasibility of full-scale ASR implementation related to its effects on water levels, water quality, and biota and any outstanding issues (e.g., hydrogeology, geophysics) that could not be addressed by individual pilot projects. The ASR Regional Study included development of a regional groundwater model of the Floridan aquifer system, which was used to assess the technical feasibility of the proposed 333-well ASR system and, if infeasible, identify an appropriate magnitude of ASR capacity with minimal environmental impacts. NRC (2002) reviewed the proposed ASR Regional Study plan.

The $25 million ASR Regional Study began in 2003, and the results of the study are described in the ASR Regional Study Final Technical Data Report (TDR; USACE and SFWMD, 2014). The ASR Regional Study project consisted of four main focus areas:

• A hydrogeologic analysis to evaluate the regional extent of permeable storage zones, confining units, and groundwater quality in the Floridan aquifer system;
• Evaluation of water quality changes during ASR cycle testing;
• Groundwater flow simulations to evaluate the feasibility of regional-scale ASR, specifically locations and numbers of ASR wells that can be constructed without exceeding hydraulic and regulatory criteria; and
• An evaluation of the ecological risks of the recovered water.

COMMITTEE STATEMENT OF TASK

At the request of the USACE, the NRC’s Water Science and Technology Board convened a committee of experts to review the ASR Regional Study TDR. The NRC was asked to assess progress toward the ASR Regional Study’s stated goals “to reduce uncertainties related to full-scale CERP ASR implementation by conducting studies based on existing and newly acquired data, develop a regional groundwater model of the Floridan Aquifer System (FAS), and identify an appropriate magnitude

FIGURE 1-2 Locations of the five originally planned CERP ASR pilot projects. Ultimately, pilots were constructed only on the Kissimmee River and the Hillsboro sites because of funding limitations or poor site conditions.
SOURCE: USACE and SFWMD (2008).

of ASR capacity with minimal impact to the environment and existing users of the FAS.” The committee was specifically tasked to review and comment on the following aspects:

• Validity of the data collection and interpretation methods,
• Integration of studies comprising the four focus areas mentioned above,
• Evaluation of scaling from pilot- to regional-scale application of ASR, and
• The adequacy and reliability of the study as a basis for future applications of ASR.

The committee also was asked to assess the scientific assumptions and logic on which the report’s conclusions are based. The committee was not asked to provide recommendations on the appropriate role of ASR in the CERP.

The committee’s report and its conclusions and recommendations are based on a review of the ASR Regional Study TDR, relevant technical literature, briefings and discussions at its December 11-12, 2014, meeting, and the experience and knowledge of the committee members in their fields of expertise. The committee did not review

the Hillsboro and Kissimmee River pilot results (USACE and SFWMD, 2013) in detail. Additionally, the committee did not perform an in-depth review of the regional groundwater model developed for the Regional Study, because the USACE has its own review process¹ (USACE, 2012) and such involved analysis was beyond the scope of this 6-month study.

Chapter 2 of this NRC report discusses the progress made in the ASR Regional Study to address major uncertainties, any technical issues of concern, and remaining uncertainties. The report discusses the major uncertainties raised by the ASR Issue Team (1999) and many of the uncertainties raised by NRC (2001), organized by topic: hydrogeology, recharge and recovery, hydraulic fracturing potential, groundwater modeling, water quality, and ecological risk assessment. Integration across focus areas is also discussed.

Chapter 3 highlights the most pressing uncertainties that need to be resolved to inform policy decisions on the future role of ASR in the CERP and discusses possible strategies to address these issues.

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¹ The ASR Regional Study groundwater model was developed using the SEAWAT modeling code (Guo and Langevin, 2002). Both the bench-scale ASR model and the Phase II model calibration report were reviewed by the CERP Interagency Modeling Center (see TDR appendix E), and the Phase I calibration report received review comments at a 2008 interagency meeting (C. Murray, USACE, personal communication, 2015).

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