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Posters with Abstracts


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EFFECTS ON FLORIDAN AQUIFER WATER QUALITY IN EAST-CENTRAL FLORIDA FROM LONG-TERM STORMWATER RECHARGE THROUGH WELLS - A PROGRESS REPORT

Alan W. Aikens, CH2M Hill, 225 E. Robinson St., STE 505, Orlando, FL 32803

Management of stormwater through recharge wells is a practice in the Orlando, Florida area that has been employed and effective since the early 1900's. Nearly 500 recharge wells were recently inventoried in Central Florida. The wells divert an estimated average of 30 to 50 million gallons per day of stormwater to the Upper Floridan aquifer. The wells are of two types: direct urban runoff wells and lake-level control wells. The St. Johns River Water Management District is sponsoring a program, with local cooperators, to quantify changes to chemical and microbial quality of groundwater resulting from this practice. This is applicable to proposed aquifer storage and recovery (ASR) applications of surface water in the Floridan aquifer in that these recharge systems have been in place and operating in the Orlando area for 50 to 100 years. Monitoring these systems will provide valuable insight to the potential success of applying ASR to surface water management techniques.

The on-going project is at two sites, one for each type of recharge well system: Festival Park in Orlando - direct urban runoff, and Lake Orienta in Altamonte Springs - lake-level control. The project has six phases: dry-period characterization (corresponding with a prolonged drought during the late 1990's), baseline characterization, groundwater tracer test, operational characterization, enhanced treatment evaluation and possible implementation, enhanced treatment effectiveness evaluation. Water flowing into the recharge wells and groundwater from monitoring wells is sampled for an extensive list of inorganic and organic chemical parameters and selected microbes (bacteria, protozoa, and a virus).

This paper presents a progress report of the current results of the program. To date, completed activities at Festival Park are the groundwater tracer test, baseline sampling, and four of the six operational characterization samplings. Results for Festival Park indicate connection between a recharge well and two monitoring wells indicate rapid groundwater transport between these wells, indicate 3 to 4 orders-of-magnitude reduction of coliform concentrations from the recharge well to the monitoring wells. This reduction occurs over distance of 250 to 450 feet and a duration as short as two weeks. Very few detections of organic chemicals with no concentration greater than Maximum Contaminant Levels were encountered. The inorganic chemical data indicate a shift in the character of the groundwater from the stormwater recharge. The potential for mobilizing arsenic and other trace elements from the aquifer matrix is present. Site activities at Lake Orienta began January 2004 with the installation of the four monitoring wells. Baseline sampling and a groundwater tracer test are scheduled for the summer of 2004. Operational characterization sampling is scheduled from fall 2004 through spring 2005.



GEOPHYSICS AS AN INTEGRAL PART OF THE AQUIFER STORAGE AND RECOVERY PROCESS

Thomas L. Dobecki (1) and Jennifer L. Hare (2)

1 - SDII Global Corporation, 4509 George Road, Tampa, FL 33634
2 - Zonge Engineering & Research, 3322 E. Ft. Lowell Rd. Tucson, AZ 85716

Aquifer storage and recovery (ASR) has very many basic similarities, unknowns, and needs as compared with a variety of in situ processes that have been investigated in the past. These include, among others, pumped storage, secondary and tertiary petroleum recovery (hydraulic fracturing, CO2 flooding, brine flooding), and in situ combustion processes (coal gasification, oil shale retorting). A central concern to each of these as well as ASR is an accurate depiction of how/where the process develops (process monitoring). Geophysical surveying techniques, principally methods relying on the electrical resistivity contrast between native and stored waters, are viewed as the most probable means for mapping the shape and progress/growth of injected water during ASR activities. Model studies are presented using typical ASR depths, formation (ambient) water and injected water resistivities, which indicate that electrical resistivity-based surveys (e.g., controlled source audio magnetotelluric profiling [CSAMT] and transient electromagnetic sounding [TEM]) have the potential to track growth and shape of the ASR injected waters.



THE EFFECTS OF HETEROGENEITY OF THE UPPER FLORIDAN AQUIFER ON ASR SYSTEMS

Bill Hutchings (1), Vacher, H.Len (2), and Budd, David (3)

1 - HSA Engineers & Scientists, 4019 East Fowler Avenue, Tampa, FL 33617
2 - Geology Department, University of South Florida, 4202 E. Fowler Ave., Tampa, FL 33620
3 - Department of Geological Sciences, University of Colorado, Campus Box 250, Boulder, CO 80309-0250

The matrix permeabilities of approximately 1200 meters (m) of the Upper Floridan aquifer (UFA) in the southern SWFWMD area were measured from cores in eight wells with a minipermeameter at one-foot intervals and classified by depositional texture. A wide range of lithologies ranging from permeable grainstones to low-permeability high-mud packstones are present. The bulk of the intrinsic transmissivity is contributed from the grainstones and dolostones, although they represent a minor percentage of the thickness of the aquifer.

We selected a 200-foot interval from the Suwannee Limestone as a representative section to study the effects of bed-scale, layered heterogeneity on a theoretical Aquifer Storage and Recovery (ASR) well. The wide range of permeabilities at the core scale was modeled with a highly discretized (200-layer), three-dimensional flow (MODFLOW) and solute-transport (MT3D) model to ascertain the distribution, storage, and recovery of injected water. The models reveal that units of high permeability facilitate the depth of penetration of injected water into the aquifer. The domain of injected water is not at all like a bubble, but instead much like a bottle brush. Taking into account the effects of buoyancy, which we did not do in this study here, one can easily picture the inverted Christmas tree proposed by Missimer and associates for the geometry of the invaded domain.



THE RELATIONSHIP BETWEEN PYRITE STABILITY AND ARSENIC MOBILITY DURING AQUIFER STORAGE AND RECOVERY IN SOUTHWEST CENTRAL FLORIDA

Gregg Jones (1) and Thomas Pichler (2)

1 - Southwest Florida Water Management District, 2379 Broad St. Brooksville Fl, 34609
2- University of South Florida Geology Department 4202 East Fowler Ave SCA 532 Tampa, Fl 36620

Elevated levels of arsenic are common in water recovered from aquifer storage and recovery (ASR) systems that store oxygenated surface water in southwest central Florida. Mineralogical investigations of the Suwannee Limestone, the preferred storage zone for ASR systems, have shown that the highest concentrations of arsenic are associated with framboidal pyrite in zones of high moldic porosity.

This investigation employed geochemical modeling to examine the stability of pyrite in limestone during simulated injections of oxygenated surface water. Injections were simulated for 20 wells with intervals in the Suwannee Limestone with known chemical composition. The goal was to determine if aquifer redox conditions could be altered to the degree of pyrite instability. Increasing amounts of injection water were added to the formation water in a series of steps and the resulting reaction paths were plotted on pyrite stability diagrams. The pre-mixing formation water in the wells plotted within the pyrite stability field indicating that redox conditions were sufficiently reducing to allow for pyrite stability. Since arsenic is immobilized in pyrite, its concentration in the formation water should be low. This was corroborated by actual analysis of arsenic in water samples; none of the 20 wells sampled had concentrations above 0.1 g/l. During simulation, however, as the ratio of injection water to formation water increased, redox conditions became less reducing and pyrite became unstable. As a result, arsenic would be released from the aquifer matrix. The simulation also showed that the ratio of injection water to formation water necessary to cause pyrite instability was highly variable and seemed to be controlled by the chemical composition of the formation water.



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 g/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. Quiones-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.



Last updated: September 22, 2010

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