• ASR proposed by Restudy as major water storage component to meet seasonal and longer dry period water needs.

• Plan calls for 300 ASR wells injecting combined total of 1,775 Mgal/d water from SW or shallow GW.

• ASR would provide environmental benefits of environmental water supply deliveries, flood water attenuation, and improved regulation of Lake Okeechobee stages. Would also augment urban and agricultural water supplies during dry periods.

• ASR is being implemented successfully at several locations in Florida and elsewhere in the country, but at a scale of a few to several million gallons per day.

• Use of ASR at proposed scale - 1,775 Mgal/d - has never been attempted, therefore regarded as unproven as a reliable large-scale technology.

• Governor's Commission for a Sustainable South Florida, in its conceptual plan, recommended that "ASR technology should be investigated to determine its feasibility at a regional scale."

• Various issues and uncertainties surrounding regional scale ASR were identified in a Public Workshop held June 18, 1998 by FDEP and USEPA, and led by panelists expert in various ASR aspects.

• In response to workshop outcome, South Florida Ecosystem Restoration Working Group formed the Aquifer Storage and Recovery Issue Team in September 1998.

• Purpose of Issue Team is to develop an action plan and identify projects to address surface water quality, hydrogeological, and geochemical uncertainties associated with regional-scale ASR facilities.

• Issue Team members are Sally Kennedy and Lou Devillon (SFWMD); Richard Deuerling, Will Evans, Paul Park, Jose Calas and Richard Orth (FDEP); Richard Punnett (USACE); John Vecchioli (USGS); Fred Rapach and Bill Cocke (Palm Beach County); Richard Harvey (USEPA); Tom Missimer (GSCSF), and Col. Terry Rice (Miccosukee Tribe). Technical Advisors are Pat Gleason, Mark Pearce, Phil Waller, David Pyne, Pat Lehman, Jim Cowart, Tim Sharp, and Mark Abbott - all from consulting firms except Pat Lehman (PR/MRWSA) and Jim Cowart (FSU).

• Issue Team has been active from September to current in preparing and finalizing an assessment report to the South Florida Ecosystem Restoration Working Group.

• Presentation based on draft report submitted to Working Group in January.

Identified Issues by Team

Description:

• The UIC Program regulatory requirement that ASR source waters meet drinking water standards before injection into a USDW needs to be addressed.

• Source waters will not meet drinking water standards - at least with respect to total coliform bacteria.

• Chlorination to kill off bacteria prior to injection is costly and will result in formation of undesirable disinfection byproducts owing to high organic content of source waters.

• USEPA is willing to consider a flexible approach to permitting raw water ASR wells proposed by the Restudy if "risk-based" analyses demonstrate that the USDW will not be endangered in a way that could adversely affect human health.

• Fundamental to EPA considering a flexible approach is the confirmation through a comprehensive evaluation of the quality of proposed source waters that total coliform bacteria is the only problematic parameter and the demonstration that the biological contaminants will experience "die-off" within the saline/brackish water aquifer such that the presence of these contaminants in the USDW will not cause a violation of the MCL or pose an adverse health risk.

Strategy:

• The SFWMD and the FDEP requested that USEPA articulate its willingness to pursue a flexible approach to ASR permitting. EPA, through Regional Administrator John Hankinson, has responded articulating its position and stipulating the conditions that must be met to allow "raw water" ASR.
• Prospective source water quality needs to be characterized, temporally and spatially, through evaluation of existing data and through additional sample collection. EPA and FDEP should participate in developing the water quality sampling protocols, including list of parameters.

Description:

• Limited information exists on the vertical distribution of potential injection zones, their regional extent and continuity, their hydraulic properties, and the quality of the native waters they contain, especially in inland areas where most of the ASR activity is proposed.

• This information is needed to evaluate hydraulic interaction (mutual well interference) between ASR sites, and overall hydraulic impact.

  Optimization of injection rates/recovery volume needs information on hydraulic properties and water quality of the potential injection zones.

• Some of this information can be collected from the pilot ASR installations discussed in Issue 7, but because of their cost, only limited sites will be installed over the next several years. Test drilling, along with pilot installations, would greatly accelerate acquisition of data.

Stragegy:

• Assemble all of the currently available data on the hydrogeology of the Upper Floridan aquifer in South Florida and evaluate its deficiencies.

• Plan and implement a test well drilling and testing program that provides the needed hydrogeologic information where lacking. Coordinate with pilot installations program.

• Select drilling sites in likely areas of ASR source waters and discharge points wherever possible.

• Test wells can later serve as monitor wells for ASR installations.
• From the existing data simultaneously installed pilot ASR facilities data, and test well data, develop maps and cross sections that define the hydrogeologic framework of the Upper Floridan aquifer - depths and continuity of potential injection zones, their water quality, and their hydraulic characteristics.

Description

• Simultaneous operation of hundreds of injection wells could cause a buildup in hydraulic head sufficient to initiate hydraulic fracturing or propagate existing fractures.

• Fracturing could result in upward migration of injected water or formation waters into USDW's of higher water quality than the injection zones.

Strategy:

• Estimate critical fracture pressure with formulas in the literature.

• Compare fracture pressure with likely injection pressure buildup.

• Perform fracture testing as part of test drilling program. Extent of fracture testing to depend on closeness of estimated fracture pressure with expected pressure buildup.

Description:

• Regional hydraulic head changes caused by the simultaneous operation of multiple injection wells will change subsurface flow patterns.

• These changes could impact existing ASR facilities, supply wells, and UIC monitoring wells.

• Simultaneous operation of injection wells will cause significant well interference among them owing to the highly diffusive nature of the Upper Floridan aquifer.

• Potential increases in hydraulic head would influence the design and pump sizing of the ASR installations and perhaps the overall feasible magnitude of the total ASR application.

• Ability to predict and evaluate the combined head changes due to regional scale ASR implementation is crucial to the assessment of large-scale ASR feasibility.

Strategy:

• A ground-water modeling effort is needed to predict the hydraulic impact of regional scale ASR.

• The model should be 3-D and capable of simulating variable density flow.

• Values of the hydraulic characteristics of potential injection zones are not well defined. Especially lacking is information on leakance.

• Definition of the hydraulic properties should be part of the ASR pilot installations program and also part of the test drilling program.

• Until sufficient information is available to construct a suitable model of ground water flow in the Upper Floridan aquifer, a superposition simulation approach is recommended.

• The superposition approach would be based on assigning reasonable ranges of values of aquifer hydraulic characteristics, rather than actually measured values. Ranges of potential changes in head would result.

• Results from the superposition modeling exercise could be used to evaluate quickly the viability of the regional ASR at the proposed scale.

Description:

• Operational ASR sites in Florida have never exceeded MCL's for Federal and State drinking water standards, or minimum criteria, nor have they posed a threat to public health due to geochemical interactions between injected waters and the storage aquifer rock matrix and native waters.

• Nonetheless, the extent to which adverse water quality changes may occur when oxygenated surface waters with their constituent loads are injected and geochemically interact with the storage zone rock matrix and contained native waters requires further study due to the vast amounts of water involved in regional ASR and the variability of the geochemical composition of the Upper Floridan aquifer.

• Focus of the geochemical studies will depend on source water quality, whether treated or untreated.

Strategy:

• Comprehensive characterization of source water quality, native water quality, and aquifer matrix composition is needed.

• In addition to characterizing the quality of water injected and ultimately recovered, of the changes occurring in the storage zone should be studied through sampling at on-site monitor wells associated with each ASR storage zone. Pre-injection geochemical modeling can be done to identify constituents and processes to investigate through sampling.

Description:

• Currently, there is no information about whether ASR will exacerbate the Everglades mercury problem.

• Research has shown that under certain circumstances, pH, chloride, and sulfate are correlates of methylmercury bioaccumulation. ASR has the potential to influence these water quality parameters, therefore study of the potential of ASR to make the Everglades mercury problem worse is needed.

• There is also the possibility that inorganic Hg in the injected water or in the aquifer matrix could be methylated by sulfate reducing bacteria during storage and thus be added to the recovered water. Sulfate reducing bacteria are likely to be present in the anaerobic environment.

Strategy:

• Continue basic biogeochemical studies and modeling to simulate the effects of chloride and sulfate concentrations on methylmercury production and its bioaccumulation.

• Evaluate the effects of ASR on chloride and sulfate concentrations at the point of discharge into the Everglades.

Description:

• For large scale regional ASR, uncertainty exists regarding storage intervals to be selected within the Upper Floridan aquifer, the hydraulic properties of these intervals, potential recharge and recovery rates, and associated volumes that may be injected, stored, and recovered.

• Pilot ASR facilities of demonstration-scale size are needed to demonstrate the viability of the proposed large scale regional ASR concept. Clusters of ASR wells, each having a capacity of 5 to 10 Mgal/d, are needed to demonstrate that regional ASR implementation at the proposed scale is feasible.

Strategy:

• Sites should be selected for demonstration tests that represent the geographic range of regional scale ASR opportunities and also the range of potential applications to meet urban, agricultural, and ecosystem needs.

• Several demonstration test sites are currently being planned or already underway, and the testing at these sites should be coordinated and made comprehensive for improving our understanding of the aquiferís response to ASR.

• Other demonstration sites should be planned in areas of source water availability and recovered water utility.

• About five to ten demonstration test sites are needed to address the range of hydrogeologic conditions and proposed ASR applications. Each site should include several large diameter ASR wells each equipped to recharge and recover water at 5 to 10 Mgal/d.

• Each demonstration test site should have initially a test hole constructed to obtain data on local hydrogeologic conditions, including transmissive intervals and their water quality. These test holes should be integrated with the test drilling program discussed in Issue 2.

• Little doubt that ASR will work nearly everywhere in South Florida at some scale.

• Much information must be obtained to evaluate viability of implementing regional ASR at a scale of 1,775 Mgal/d.

• Suitability of source water quality for injection with minimal pretreatment must be demonstrated.

• Hydraulic response of aquifer to large scale recharge needs evaluation.

• Assessment of recovered water quality is needed to alleviate concerns of environmental incompatibility.

• Finally, demonstration of large scale ASR testing with several large size/volume wells closely clustered is needed from which to gather operational data.

Related Links

What is Aquifer Storage and Recovery (ASR) and how does it work? (on-line version of posters from forum)