ARSENIC AND AQUIFER STORAGE AND RECOVERY IN SOUTHWEST FLORIDA: SOURCE, ABUNDANCE,
 AND MOBILIZATION MECHANISM, SUWANNEE LIMESTONE, UPPER FLORIDAN AQUIFER

Roy E. Price and Thomas Pichler, University of South Florida Geology Department 4202 East Fowler Ave SCA 532
Tampa, Fl 36620

Recent analyses of recovered water from two aquifer storage and recovery (ASR) facilities in west-central Florida showed arsenic concentrations in excess of
100 gg/L, more than 10-times the current EPA drinking water standard. Detailed mineralogical and chemical analyses of the Suwannee Limestone, the primary
storage zone for ASR in west-central Florida, indicates that, while arsenic is ubiquitous throughout the Suwannee Limestone, it is highly concentrated in
framboidal pyrite. Elevated levels of arsenic in pyrite were documented by scanning electron microscope and electron probe microanalysis with energy
dispersive and wavelength dispersive x-ray capabilities, respectively, showing greater than 1000 ppm arsenic. The pyrite containing the arsenic is normally
stable in the reducing environment of the aquifer, but the artificial recharge of oxidized surface water during ASR changes the redox conditions and is believed
to cause the framboidal pyrite to become unstable, thus releasing the arsenic.



 AQUIFER STORAGE AND RECOVERY EXPERIMENTS IN THE LOWER HAWTHORN GROUP AQUIFER,
 LEE COUNTY: PREVIOUS SIMULATIONS AND ILLUSTRATION OF A DUAL-POROSITY APPROACH

Eberhard Roeder, 6854 Hanging Vine Way, Tallahassee, Fl 32317

High recovery efficiency of aquifer storage and recovery (ASR) systems requires that the injected water interacts little with ground water in place. The
existence of preferential flow paths influences the extent of interaction between injected and resident water and thus can be expected to affect recovery
efficiency. Most past numerical models of ASR in Florida have considered preferential flow paths in the storage zone indirectly, by using a calibrated low
value for effective porosity, or as explanation for residual error. An alternative, the dual-porosity approach, divides aquifer porosity into a mobile fraction
wherein advective transport occurs and another stagnant or immobile fraction in which concentrations change in response to diffusive mass transfer from the
mobile fraction.

In this modeling study, I revisit the injection, storage and recovery experiments in the Lower Hawthorn Aquifer in Lee County described by Fitzpatrick (1986)
and illustrate differences between single and dual-porosity approaches. Quifones-Aponte and Wexler (1995) previously simulated these experiments using a
single-porosity approach with a version of SUTRA. The simulator used in this study to represent the density-dependent transport of Chloride in single and
dual-porosity aquifers is a slightly modified version of the compositional FDM simulator UTCHEM.



 GUIDELINES FOR AQUIFER STORAGE AND RECOVERY REGULATION IN THE UNITED STATES

Catherine Shrier, Senior Water Resources Engineer, Golder Associates Inc., 44 Union Boulevard, Suite 300, Colorado
80228

Regulatory concerns and state and federal regulatory practices have been among the most pressing issues impacting the development of aquifer storage and
recovery (ASR) facilities in the United States. With at least 26 states having developed or investigated the development of ASR facilities, a wide range of
regulatory issues have been raised by state, federal, and some local or regional agencies. Issues have included the regulation of recharge and storage practices,
primarily to protect groundwater aquifers; recovery, treatment, and use of stored water, particularly for potable uses; and water rights or other water resources
management laws and programs. With multiple agencies involved in ASR regulation, several states have also investigated or implemented regulations to
streamline the permitting process. This paper reviews the major regulatory issues that have been considered in 20 states with operating or pilot ASR facilities,
as well as federal regulatory issues pertaining to ASR. This paper also highlights issues for regulatory agencies and water managers to consider for future ASR
facility development.



 LATTICE BOLTZMANN MODELING FOR AQUIFER STORAGE AND RECOVERY SYSTEMS

Mike Sukop and Danny Thorne, Florida International University, Dept. of Earth Sciences, PC 344, 11200 SW 8th
Street, Miami, Fl 33199

Lattice Boltzmann models of fluid flow and solute transport readily handle several well-know and important challenges that limit the ability of Darcy's law-
based models to accurately simulate flows and solute transport in aquifer storage and recovery (ASR) systems. In particular, we simulate flows in any complex
cave/conduit/pore spaces over a broad range of Reynolds numbers leading to complex flow phenomena such as vortex streets that have never been
incorporated into ground water models but undoubtedly play a significant role in solute transport and the recovery of stored water -especially in karstic
aquifers. The principal strengths of lattice Boltzmann methods in these areas are the ease of incorporating the details of complex geometry and the direct
computation of Navier-Stokes flow solutions in the complex space. Solute transport is intimately coupled to the flows so that eddy diffusion, for example,
becomes an integral part of the transport process. Concentration-dependent density-driven flow is important in ASR systems and is a highly non-linear process
that has proven difficult to solve with standard finite element and finite difference approaches; lattice Boltzmann methods are at least as good as the most
advanced standard approaches and have numerical advantages that could make them far superior for these problems.



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