Groundwater Resources Association of California Western Groundwater Congress
The Eighth Annual Western Groundwater Congress (WGC) hosted by the Groundwater Resources Association of California will take place on October 6 to 9, 2025, in San Diego, California. DBS&A is proud to be the WGC Diamond Sponsor. Staff from the Geo-Logic companies will be at our exhibit, and presenting throughout the event. DBS&A Principal Hydrogeologist Tony Morgan, PG, CHG, will present “Tried and True v. New and Innovative – A Comparison of Aquifer Hydrologic Characterization Techniques.” Clear Creek Associates Hydrogeologists Geno Mammini will present “Siting, Design, and Permitting Challenges from a Newly Permitted Underground Storage Facility” and Dustin Graves will present “Applied Recharge Effects on Solute Transport in the Vadose Zone and Potential Groundwater Impacts,” respectively. Staff attending also include Luis Busso, PG; Matias Gibertoni; and Gus Tolley, PhD, PG, who will be moderating the Student Networking and Participation Program (SNAPP).
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Abstracts
Tried and True v. New and Innovative – A Comparison of Aquifer Hydrologic Characterization Techniques Presented by Tony Morgan, PG, CHG
Practicing hydrogeologists are well-acquainted with traditional aquifer testing methods, such as slug tests, variable rate (step) tests, and constant rate pumping tests, which are commonly used to estimate key physical aquifer properties like transmissivity and hydraulic conductivity. These methods are widely considered the “gold standard” for subsurface characterization due to their direct measurement approach. However, they often come with logistical challenges, including disruptions to field schedules, higher labor demands, and increased project costs. As a result, there is growing interest in alternative, less invasive geophysical techniques—such as seismoelectric surveys and borehole nuclear magnetic resonance (NMR)—which can provide indirect estimates of aquifer properties more rapidly and at lower cost. Despite these advantages, adoption of these methods has been limited due, at least in part, to uncertainty about their accuracy and lack of widespread validation against standard hydrogeological tests. A well construction project in Ukiah, California, provided a unique opportunity to perform a comparative study of these methods. Hydraulic parameters were obtained using a combination of surface-based seismoelectric surveys, borehole NMR logs, zone-specific slug tests, and conventional step and constant rate pumping tests. Preliminary findings suggest that the seismoelectric method may be valuable during the early stages of site selection, offering a broad overview of subsurface conditions, but lacked precision in estimating aquifer properties at discrete depths. In contrast, borehole NMR showed consistent relative trends with slug and pumping test data across three tested zones, although it significantly underestimated absolute values when compared to the more established methods.
Siting, Design, and Permitting Challenges from a Newly Permitted Underground Storage Facility
Presented by Geno Mammini, RG
Underground Storage Facilities (USFs) are an excellent means for storing excess water supplies so that they may be used to augment future supplies. USF permitting is required for water to be stored in an aquifer through percolation basins, vadose zone wells, Aquifer Storage and Recovery (ASR) wells, streams, washes and/or a combination of thereof. This presentation will detail key components and lessons learned from a recently permitted USF in the Phoenix area, where numerous logistical and hydrologic challenges were encountered, including: siting within an existing master planned community, limited land availability, low subsurface permeability, overhead utilities, groundwater quality concerns, accurate accounting/metering needs for multiple water sources, and the development and programming of 9 separate recharge operation scenarios. This presentation is recommended for any individual interested in managed aquifer recharge (MAR) projects and gaining insight on the wide range of challenges that often arise while designing and permitting a MAR project.
Applied Recharge Effects on Solute Transport in the Vadose Zone and Potential Groundwater Impacts
Presented by Dustin Graves, RG
The use of infiltration basins or vadose zone wells for managed aquifer recharge is a common practice in Arizona, especially for treated effluent from Water Reclamation Facilities. Effluent (now commonly referred to as reclaimed water) used for recharge is typically treated to water quality standards that are as good as or better than the ambient groundwater quality of the receiving aquifer(s). In some cases, however, compliance monitoring data following the introduction of new recharge applications may reveal an increase in concentrations of select dissolved solutes in the groundwater which may ultimately exceed the Arizona Aquifer Water Quality Standards. This phenomenon has been attributed to an initial flushing of solutes, including nitrate, from the vadose zone. This can lead to regulatory challenges and a perception of potential aquifer degradation which violates Arizona’s Aquifer Protection Permit rules. Assuming the quality of the reclaimed water is superior to that of the native groundwater, continued recharge should ultimately improve the overall groundwater quality once the solutes within the vadose zone have been depleted. This presentation will detail a case study of this occurrence in the West Salt River Valley, discuss challenges with predicting future water quality changes from continued recharge, and will introduce a site conceptual model with potential mechanisms for explaining the phenomenon of groundwater quality impacts.