Hydrogeophysics and Deep Groundwater : Alphabetical Content Listing

PANEL: The Aquifer Exemption Process: Implementation for Groundwater Protection and Use

William Alley, Ph.D.

Aquifer Exemption Process Overview

Hal P. Demuth

How States Address Requests for Exempt Aquifers

Lily Lee

Relationship between the EPA and Delegated States

Lorrie Council, P.G.

Plenary Session (Joint with SAGEEP)

Mapping Brackish Aquifers: Future Water Resources

Andrea Croskrey, P.G.
Texas can be a land of meteorological extremes. Drought one year, flash flooding the next. In response to the “Drought of Record” in the 1950s, the Texas Water Development Board (TWDB) was born. Tasked with writing the State Water Plan every 5 years, this state agency estimates water supply and demands 50 years into the future. It then helps regional water entities create strategies for meeting potential water deficits. One of the strategies is the desalination of brackish groundwater. Though a few famous wells from Texas history were brackish, there is a much to learn about this resource which was often viewed as undesirable and avoided. The Brackish Resource Aquifer Characterization System (BRACS) at the TWDB is mapping brackish aquifers in the state to provide a foundational knowledge of the resource. One of the challenges of mapping brackish groundwater is the lack of water quality data in the deeper and more saline portions of the aquifers. To help fill this data gap, BRACS uses geophysical well logs to calculate interpreted water quality values. Since 2009, the BRACS program has amassed a database of more than 60,000 well locations that have an assortment of attributes including stratigraphic picks, lithologic descriptions, water quality, aquifer tests, and geophysical logs, 5 published reports, and 3 contracted reports. Per a state legislated mandate, the brackish groundwater in all 30 major and minor Texas aquifers will be evaluated by December of 2022. Current and completed studies are posted on our website, along with finished reports and data.

The Critical Role of Water in Critical Zone Science: An Exploration of Water Fluxes in the Earth’s Permeable Skin

Kamini Singha
Earth’s “critical zone” — the zone of the planet from treetops to base of groundwater — is critical because it is a sensitive region, open to impacts from human activities, while providing water necessary for human consumption and food production. Quantifying water movement in the subsurface is critical to predicting how water-driven critical zone processes respond to changes in climate and human perturbation of the natural system. While shallow soils and aboveground parts of the critical zone can be easy to instrument and explore, the deeper parts of the critical zone — through the soils and into rock — are harder to access, leaving many open questions about the role of water in this environment.
 
This presentation opens the black box in the subsurface and sheds light on a few key subsurface processes that control water movement and availability: linkages between changes in evapotranspiration and subsurface water stores, water movement in three dimensions over large areas, and potential control of slope aspect on subsurface permeability. Geophysical tools are central to the quantitative study of these problems in the deeper subsurface where we don’t have easy access for observation.

Registration

Registration

Track 1: Applications of Hydrogeophysics to Groundwater Characterization, Monitoring, and Management

Melinda Chapman

Advances in the Realm of Hydrogeophysics: the Role of Quantum Geoelectrophysics in Groundwater Exploration

Jon Fennell, Ph.D., P.Geol.
Water is integral to our economy, the health of our environment, and our survival as a species. Much of this water is accessed from surface sources, mostly rivers, which are now under increased threat due to over use and the resulting hydro-political forces. Yet, groundwater exists as a viable option in many countries facing these mounting challenges. Knowledge of our deeper groundwater systems, although increasing, is still quite limited due to our propensity to focus efforts in the lower cost, lower risk, near-surface environment. However, accessibility to shallower groundwater is tightening due to increasing use, changing regulatory requirements, and climate change.

The use of classical geophysics to explore for groundwater resources, such as seismic, gravity, magnetics, and resistivity, has been the industry standard for many decades. These technologies have proven quite effective both in the shallow and deeper environments. However, newer remote sensing and ground-based technologies are now emerging with the ability to significantly reduce costs and time, and increase success for groundwater exploration and development programs.

Quantum Direct Matter Indicator (QDMI) technologies, or applied methods of Quantum Geoelectrophysics, are poised to revolutionize the hydrogeophysical industry, much like electro-magnetic (EM) and electrical resistivity tomography (ERT) did years ago. QDMI utilizes resonant frequency remote and direct sensing technologies that detect perturbations in the earth’s natural electric and electromagnetic fields. Controlled source electromagnetic pulse methods with electromagnetic spectrum spectroscopy are used to identify aquifers, including thickness, water quality (fresh or saline) and temperature, to depths of 1000 m or more accurately. With multiple successes around the world, the deployment of this inventive and effective approach to groundwater exploration in North America is occurring today.

This presentation will present the basis of QDMI technologies and showcase some of the benefits and examples this emerging exploration tool can provide to groundwater exploration efforts.

Airborne Geophysics for Characterizing Aquifers with Examples from Antarctica to Nebraska

Bill Brown
Water-resource managers traditionally used borehole logs, surface geophysics and wells to gain an understanding of groundwater and its flow paths. This point source data may be scarce or difficult to obtain and often samples aren’t geographically dense enough to make decisions on groundwater management over large areas. The application of airborne electromagnetic surveys (AEM) has increased in recent years because the method can quickly and economically deliver high-quality subsurface data from which comprehensive hydrogeologic frameworks can be developed.

The principles of airborne geophysics will be introduced and case studies will present airborne data from groundwater surveys conducted in Antarctica, the USA and Canada. These studies will cover a variety of objectives and targets including identification of aquifer materials, freshwater/saltwater interactions and water volume estimations. It will be shown how the airborne data can be used to identify productive targets for drill planning as well as how the airborne data can be used to complement existing borehole data to produce geological interpretations.

3D visualizations and a short video will be used to show how geological interpretations are reinforced with benefit of a priori data (boreholes) which in turn leads to informed and economic selection of productive drill targets.

Characterization of a Complex Permafrost Aquifer System Using Airborne Electromagnetic Data

Steven Humphrey, PG
An airborne RESOLVE® electromagnetic geophysical survey was completed in a sub-arctic area near Fairbanks, Alaska, USA, containing a regional permafrost aquifer system in unconsolidated alluvium. The permafrost is discontinuous, highly heterogeneous, and separates a shallow unconfined supra-permafrost aquifer (i.e., above the permafrost) from a deeper sub-permafrost aquifer. The sub- and supra-permafrost aquifers have historically been used for water supply and are hydraulically connected by taliks, surface water features, and other discontinuities. Because of these complexities, characterizing the permafrost aquifer system has been challenging using conventional characterization techniques such as drilling, sampling, and hydraulic testing.

The purpose of the survey was to collect airborne electromagnetic data that would allow us to more precisely map the extent of discontinuities in the permafrost aquifer system and refine a numerical groundwater flow model. Permafrost has a higher electrical resistivity than thawed material, and its resistivity depends on the amount of frozen versus thawed material. Therefore, resistivity data can be used to differentiate zones of permafrost from thawed material.

The RESOLVE® system consists of a 9-meter “bird” containing electromagnetic transmitter and receiver coil pairs, five coplanar and one coaxial, attached to a 30-meter cable hung from a helicopter. As the helicopter is flown over an area, apparent resistivity is generated from the in-phase and quadrature electromagnetic components for multiple coplanar frequencies, using a pseudo-layer half-space model. The multiple frequencies of resistivity data are used to evaluate specified depths, with higher frequencies reflecting shallower depths. The survey area encompassed 12 square miles to a depth of approximately 400 feet below ground.

The data were used to create a geological model which differentiated permafrost from thawed zones in three dimensions and facilitated refinement of the groundwater flow model. Modeling results demonstrate that the model was more accurate after incorporating permafrost discontinuities mapped with the geophysical survey.

Corroborating Collapse Structures from Land/Marine Surveys in Carbonate Systems Using Borehole Geophysical Logs

Melinda Chapman
Subsurface carbonate systems are inherently complex as a result of dissolution of sedimentary rocks and collapse within the groundwater-flow system. These collapse structures may penetrate upper confining units that may have previously protected the aquifer. Increased resolution of subsurface collapse structures at depth from modern land and marine seismic surveys has greatly enhanced the ability to both detect and delineate these features that potentially control the upward migration of groundwater. The use of borehole geophysical logs to corroborate the surface geophysical survey interpretations is essential to understanding the physical collapse systems, including secondary fractures and other features.

In Miami-Dade County, Florida, USA, wastewater injection operations at the South District plant have been ongoing since the late 1970s. The target injection horizon has been the Boulder Zone, a permeable dolomitic unit present at depth from about 2,700-3,000 feet. A review of more than 500 borehole geophysical logs collected from the original pilot holes and injection wells in comparison to recent seismic surveys in the area have revealed the potential delineation of collapse structures. Such collapse structures may affect upward migration of injected wastewater from the Boulder Zone into shallower carbonate zones of varying permeability. Delineation of fractures, both within and potentially outward away from the wells, which are potentially associated with collapse structures tapped by the 17 injection wells, is part of a recent effort being conducted by the U. S. Geological Survey in cooperation with Miami-Dade County. Because groundwater modeling tools have evolved since publication of the original flow and transport model for the South District, the use of this more detailed physical framework information toward future modeling efforts should greatly improve the accuracy of those simulations.

Developing Groundwater Flow Nets Using Electrical Resistivity

Todd Halihan, Ph.D.
Flow nets provide an understanding of groundwater flow built on strong theoretical and numerical models. The simplest version is the solution to the Laplace equation and illustrates flow lines moving vertically and converging near discharge locations. In field settings, the amount of field data utilized to support these conceptual models is generally limited due to a small number of piezometers being used to structure the field flow net. Multielectrode electrical resistivity data in 2D can provide a strong addition to piezometers as it can illustrate flow lines in 2D with continuity unavailable from piezometer data. Utilizing contrasts in salinity, varying rock properties, or biological growth patterns, flow lines can be observed in systems to develop conceptual models of discharge and convection based on 2D data. These models would be difficult to impossible to build using piezometer data. Examples will be provided from porous and fractured media flow systems and contaminated sites near streams.

Exploration for Reliable Groundwater in an Igneous-Mantled Regional Carbonate Aquifer, Death Valley National Park

Steve Rice, PG
In October 2015, a flash flood of historic proportions in Grapevine Canyon, in the northeast portion of Death Valley National Park, caused major damage to the Scotty’s Castle area including the historic spring-water catchment system used as the potable water supply for the area. To replace this system with a more reliable and flood-resistant water supply, it was determined that development of groundwater was feasible, but that successful well siting could be difficult given the ambiguity of subsurface conditions. Grapevine Canyon is a largely east-west trending drainage in the northern part of the Amargosa Range, draining west into Death Valley. Quaternary alluvium and Tertiary intrusive and volcanic rocks fill Grapevine Canyon and overlie a Paleozoic regional carbonate aquifer system that was the target for groundwater development. The second-largest spring discharge complex in the National Park discharges from this aquifer to the northwest of the study area. Utilizing Controlled-source Audio-frequency Magnetotellurics (CSAMT) techniques, a geophysical survey of Grapevine Canyon was conducted to quantify the depth of the overburden above the carbonate aquifer, the depth to presumed production groundwater levels, and the location of candidate penetrative fractures that could enhance local transmissivity. Linear transects along the axis of Grapevine Canyon were coupled with shorter north-south survey lines to provide three-dimensional representations of the canyon and surrounding uplands. Not only were the results of the geophysical survey used to site the location of a test well, but provided information on the nature of the regional aquifer in this part of the National Park.

Locating, Investigating, and Defining the Upper Laramie Aquifer, Northeastern Colorado

Travis Brown
The Cheyenne Basin in northeastern Colorado has been explored and exploited for oil and gas reserves, resulting in a wealth of self-potential (SP) and resistivity borehole geophysical logs which have facilitated aquifer characterization in the basin. The Upper Laramie aquifer in the Cheyenne Basin was initially identified through geophysical logs and has since been further characterized through 3-D seismic data, test holes, production wells, cores, and outcrop data. The depth and thickness of the lower confining unit separating the Upper Laramie aquifer from the underlying Laramie-Fox Hills aquifer has been largely delineated using geophysical logs. Additionally, in areas where shallow geophysical data is sparse, the geometry of the bottom of the Upper Laramie aquifer and the underlying confining unit has been inferred by mirroring the geometry of the underlying Upper Pierre Shale, which is more commonly captured in deep geophysical logs for oil and gas wells. The Upper Pierre Shale exhibits a characteristic geophysical signature and is conformable with the Fox Hills Formation which is, in turn, conformable with the Laramie Formation.

Geophysical logging has thus played a crucial role in assessing the Upper Laramie’s potential connectivity to other aquifers and to surface water. A large portion of the aquifer which has been explored has been determined to be nontributary – that is, only negligibly connected to surface water - allowing water rights or regulatory determinations to be obtained which permit well owners to withdraw large quantities of groundwater from the aquifer without the need for augmentation. Future investigation will continue to delineate the geometry of the aquifer and its nontributary extent.

This talk will focus on where groundwater is located in the Upper Laramie aquifer, how an aquifer is determined to be nontributary, and the use of borehole geophysics in exploring and managing Colorado’s groundwater resources.

Spiritwood Valley Aquifer Characterization Using a New Helicopter TDEM System

Jean Legault
As part of continued testing of its new VTEMTM ET (early-time) time-domain electromagnetic (TDEM) system, a test survey was recently performed over the Spiritwood Valley Aquifer that compared results from both VTEM ET and our standard VTEM Plus system with Full-waveform processing.

The VTEM ET receiver uses a re-designed broadband receiver, a re-configured transmitter, and a new digital acquisition system to achieve precise, distortion free measurements of the time-domain EM decay as early as 0.005 msec after the transmitter turn-off. This allows VTEM ET to better characterize aquifers at shallow depth (<10-30m).

The Spiritwood Valley aquifer system extends from South Dakota to North Dakota, where it is 15-20km wide and up to 100-150 m deep, and into southern Manitoba. The Spiritwood aquifer system is a complex network of glacially deposited sand and gravel bodies that are interbedded with till and clay that are relatively impermeable. It is an important supply of water both in the United States and Canada, where in particular it has been successfully mapped and studied using helicopter time-domain EM.

Over the test area, the VTEM ET results appear to reveal more complexity within the aquifer than predicted based on available drilling. The results appear to define the lateral boundaries of the Spiritwood aquifer, as well as defining both an upper aquifer, at approximately 35m, and a lower aquifer at 100m depth. The lower aquifer also appears to deviate in direction relative to the upper aquifer. The 40-50 ohm-m gravel aquifers are relatively well differentiated from the 10-30 ohm-m till-clay host sediments. In addition to improved near-surface aquifer characterization, the 100-150m investigation depths achieved by the VTEM ET system are of the same order as those achieved by the VTEM Plus system.

Transforming Groundwater System and Critical Zone Mapping and Assessment in a ‘Big Data’ Environment

Ken Lawrie, Ph.D.
Our ability to explore, assess, monitor, and manage groundwater systems in the critical zone is being transformed by a range of new and/or improved geophysical and hydrogeophysical technologies including satellite, airborne, ground and borehole sensors, and supercomputing research infrastructure. Improved sensor technologies, including airborne electromagnetics (AEM) and ground magnetic resonance (GMR), provide an opportunity for rapid multi-scale mapping, measurement and monitoring of the physical state of the crust, including resolution of key elements of groundwater systems.

These advances in sensor technologies have been mirrored by the development of supercomputing research infrastructure which is now giving the groundwater research community access to high-resolution (spatial and temporal) biophysical datasets (e.g. climate, ecology, geoscience and geospatial) relevant to groundwater system and broader critical zone understanding. This infrastructure facilitates integration of multiple datasets and rapid and improved signal processing, inversion, and sophisticated analysis. These datasets provide a catalyst for collaboration, with inter-disciplinary approaches enabling new discovery science in a ‘big data’ environment, and enabling the qualitative and quantitative analysis and modelling of landscape and hydrological system processes. These advances are complemented by novel mathematical and statistical approaches that enable data mining, analysis and pattern-matching of large volume (spatial and temporal) datasets.

Recent investigations in Australia have successfully utilised both AEM and GMR technologies in groundwater resource exploration. These complementary technologies are ‘non-invasive’, and require limited heritage and environmental clearances, enabling rapid, cost-effective acquisition of key hydrogeological data in remote ‘frontier’ areas while minimising the need for expensive drilling. Integration of these data with other geospatial, geophysical, geological, hydrodynamic and hydrogeological data within a supercomputing environment is transforming groundwater resource exploration and assessment strategies. This novel approach has led to more cost-effective assessment of potential groundwater resources and managed aquifer recharge (MAR) targets in the western Murray Basin and the Kimberley Region of northern Australia.

Using Borehole Geophysics to Identify Potential Brackish Production Areas in the Rustler Aquifer, West Texas

Daniel Lupton, PG
Groundwater is a major source of water in Texas, providing about 60 percent of the water used in the state. House Bill 30, passed by the 84th Texas Legislative Session, requires the Texas Water Development Board (TWDB) to identify and designate brackish groundwater production zones in the aquifers of the state. For this study, the INTERA Team evaluated the brackish groundwater resources of the Rustler Aquifer.

The Rustler Formation is a Permian (Ochoan) Age deposit made up of a series of alternating dolomites, anhydrites, shales and limestones. It was anticipated that the majority of the water resources were within the dolomites and limestones as opposed to the entire formation, as the aquifer was previously characterized. In addition, given the brackish nature of the Rustler Aquifer, sampled water quality data was sparse and poorly distributed. However, since the project area was within the Permian Basin of West Texas, geophysical data from oil and gas logs would be available to evaluate structure and make calculations of water quality.

A total of 589 natural gamma logs were analyzed, making approximately 5,000 stratigraphic picks to gain further insight into the specific depositional and post depositional regime of the Rustler Formation and how this knowledge relates to the Rustler Aquifer. To augment sampled water quality data, we used state-of-the art petrophysical analysis techniques developed in the oil and gas industry to analyze old geophysical logs for both porosity (neutron and sonic) and water quality (resistivity, induction and spontaneous potential). Calculations of Rustler Aquifer water quality (total dissolved solids) using geophysical logs were both novel and provided the additional data needed to better define the groundwater salinity zones within the Rustler Aquifer.

This project represents a successful integration of the specific expertise possessed by hydrogeologists, stratigraphers and petrophysicists in anticipation of evaluating brackish groundwater resources.

Using NMR and Hydrogeophysics to Evaluate ASR Feasibility in the Denver Basin

Dave Colvin, PG
As part of long range planning, Denver Water is exploring the potential for aquifer storage and recovery (ASR) in the Denver Basin aquifers. There is limited well and subsurface information within the City and County of Denver available to characterize the Denver Basin aquifers and to assess key aspects such as well productivity. As a result, Denver Water has been filling data gaps within their study area by drilling exploratory boreholes. Use of Nuclear Magnetic Resonance (NMR) geophysical logging, packer testing, and borehole coring is allowing aquifer permeability testing without the expense of completing a well, thereby allowing funding to be directed to drilling more boreholes and reducing data gaps. While NMR data has been used extensively in oilfield and unconsolidated aquifer settings, it has not been widely used in the Denver Basin for water resource investigations. We will discuss the NMR and hydrogeophysical data Denver Water has collected, how it is being used to evaluate Denver Basin ASR potential, and the aquifer characterization benefits that these techniques offer.

Well Workovers – New Direction for Improvement of Groundwater Quality

Bruce Manchon, PG
This presentation is based on the key findings from the Nebraska Grout Study: properly sealed wells will prevent the preferential pathway in the annulus of a well. We will discuss closing the preferential pathway found in existing wells and how to prevent them from occurring in newly constructed wells.

Isolating the primary producing aquifer is crucial. An effective seal above and below the aquifer needs to be established. Neat cement sealing the annulus above the SWL for well workover while a chip bentonite should be used in new well construction for sealing the annulus above/below the SWL.

The key question to ask - what do we do with the 1,000,000+ wells around the country not properly constructed? The answer is either workover or abandonment - one well at a time. A case study will be presented showing the impact of a workover and the improvement of water quality.

Water Quality Isolation depends on; 1) Well Construction; 2) Borehole Geophysics; and 3) Geochemistry. The use of borehole geophysics or elogs is the critical component of the isolation. The elogs are being used to address the issue of inadequate groundwater protection in water wells, especially as it pertains to annular seals and zone separations. The use of borehole geophysics as used for this presentation and the project provides for the:

  • conducting of basin and hydrostratigraphic analysis;
  • identifying water producing zones along with water quality in well boreholes;
  • evaluating the thickness and distribution of transmissive units and aquitards; and
  • planning and evaluating well workovers/rehabilitation and abandonment.

The overall objection of each site is to assess water quality in the alluvial sand and gravel; identify production zones in the elogs; and to locate seals and target seal zones for Public Water Supply (PWS).

Track 1: Applications of Hydrogeophysics to Groundwater Characterization, Monitoring, and Management DAY 2

William Alley, Ph.D.

Brackish Groundwater as a Resource for the Nation

Jennifer S. Stanton
The U.S. Geological Survey has conducted a national assessment to gain a better understanding of the occurrence and distribution of brackish groundwater (BGW)(dissolved-solids concentration between 1,000 and 10,000 mg/L) as well as the geochemical and hydrogeologic characteristics of the resource. A conservative estimate for the volume of BGW for depths up to 3,000 ft below the land surface is more than 900 times the amount of saline groundwater (dissolved-solids concentration greater than 1,000 mg/L) currently used each year, and more than 40 times the amount of fresh groundwater (dissolved-solids concentration less than 1,000 mg/L) used. Compiled data indicated that in regions with the most BGW, many of the sampled wells that produce BGW have reported well yields that are at least 10 gal/min, with arid southwestern U.S. basins commonly providing yields of at least 100 or 1,000 gal/min. Consequently, BGW may be a substantial water resource available for potential use by the Nation, but further evaluation is needed to determine the sustainability of BGW development.

Brackish groundwaters were evaluated chemically to assess possible uses. Frequently, chemical constituents such as arsenic, barium, boron, fluoride, iron, nitrate, selenium, or uranium in untreated BGW exceed standards for drinking water, livestock or irrigation use; however, treatment may render the BGW usable, or the BGW may be suitable for use in energy development and industrial processes. Only 5 percent of the wells producing water with a dissolved-solids concentration of 1,000 mg/L or more exceeded a Langelier-Saturation Index (LSI) of 1 (increased scaling potential), and only 2 percent of samples had a LSI less than -1 (increased corrosion potential). The potential for BGW to form mineral deposits (scale) also was evaluated using PHREEQC software. Some minerals identified as potential scaling components include calcite, barite, and chalcedony (quartz), which vary depending on the source of the water.

Detailed Geological Modeling in Urban Areas: Focus on Surface Near Geology and Anthropogenic Layer

Tom Martlev Pallesen
In the last few years, there’s an increased focus on detailed geological modeling in urban areas. The models serve as important input to hydrological models. This focus is partly due to climate changes as high intensity rainfalls are seen more often than in the past, and water recharge is a topic too. In urban areas, this arises new challenges. There is a need of a high level of detailed geological knowledge for the uppermost zone of the soil, which typically are problematic due to practically limitations, especially when using geological layer models. Furthermore, to accommodate the need of a high detail, all relevant available data should be used in the modeling process. Human activity has deeply changed the soil layers, e.g. by constructions as roadbeds, buildings basements, pipelines, landfill etc. These elements can act as barriers or pathways regarding surface near groundwater flow and can attribute to local flooding or mobilization and transport of contaminants etc.

Geophysical methods are being developed with focus on mapping the uppermost geological layers in e.g. urban areas, and these data can be evaluated against e.g. borehole data and infiltration tests.

The different datatypes, including information from subsurface structural elements (road beds, pipelines, traces etc.) can be combined and interpreted together in geological voxel models.

A geological voxel model is built by small boxes (voxels). Each box can be assigned different parameters, ex. lithology, transmissivity or contaminant concentration. Human related elements can be implemented using tools, which gives the modeler advanced options for making detailed small-scale models.

This paper demonstrates opportunities, tools, workflow and a resulting geological model for a case area in Denmark.

High Resolution Hydrogeologic Characterization of the Central & West Coast Groundwater Basins, Los Angeles County

Everett Ferguson Jr., PG, CHG
Historic analysis by geologists from both the oil industry and academia have resulted in the delineation of the complex geologic structures which make up the oil fields of the Coastal Plain of Los Angeles County. The geologic history of the deep consolidated materials are better known than the younger unconsolidated materials that comprise the numerous groundwater bearing units. Since the first regional groundwater assessment of the Coastal Plain (Mendenhall, W.C., 1905 [USGS]), numerous studies have been conducted which have enhanced the overall understanding of the aquifers and groundwater movement. By incorporating thousands of data records including water and oil well logs, the California Department of Water Resources was able to produce one of the most widely used publication for the area entitled Bulletin No. 104, Planned Utilization of the Ground Water Basins of the Coastal Plain of Los Angeles County, Appendix A – Ground Water Geology. While heavily referenced, this document should be utilized more for guidance. Since the late 1990’s and continuing today, the United States Geological Survey and the Water Replenishment District of Southern California have been implementing recent technologies to better characterize the unconsolidated materials which make up the Coastal Plain groundwater basin in order to understand the horizontal and vertical connectedness of the large scale aquifer system. This recent work has included the drilling of deep (up to 3,000 feet) boreholes, application of advanced geophysical logging, construction of nested monitoring wells, and sophisticated geochemical analyses along with implementation of a host of other tools/technologies that have resulted in the extensive collection of high resolution three-dimensional hydrogeologic data for aquifer characterization in greater detail. This presentation will present the tools currently being utilized to improve the understanding of the Central and West Coast Groundwater Basins.

Identification of the Optimal Locations for Artificial Infiltration

Max Halkjaer
Inhomogeneity of topsoil often exceeds what can be verified by boreholes. Non-invasive geophysical investigations can efficiently increase our knowledge and thereby minimized structural uncertainties in near surface hydraulic modeling.

High resolution geophysical multi coil Ground Conductivity Meter DualEM421 investigations have shown to be a successful tool for detailed mapping of the soil conductivity within the upper 5-7 m. Combined with shallow boreholes, hydraulic head measurement and simple infiltrations test, detailed description of the hydraulic conditions of the near surface groundwater is obtained. Surveys can be scaled according to size of area and needs for resolution.

Experiences shows a strong relation between electrical conductivity measured with DualEM421 and geological conditions which again is strong related to hydraulic conductivity obtained by infiltration test e.g. double-ring infiltrometer test. Site specific relation leads to significant improvement of data input for near surface 3D-geological and hydraulic modeling, and thereby optimizes the assessment of hydraulic consequences for specific SuDS and aquifer recharges solutions.

SuDS solutions for handling rainwater are often a necessity and an integrated part in the development of urban and suburban areas. Aquifer storage and recovery (ASR) is a frequently used tool for sustainable water resource management. Reuse and infiltration of treated wastewater is an important tool for maintaining water availability in water stressed environment.

Knowledge of the spatial distribution of high permeable sand layers and less permeable clay layers is crucial when pointing out the optimum location for artificial infiltration.

Presentation will showcase example from both urban and sub-urban investigation, where integrated investigation has provided an improved knowledge and minimized uncertified when planning SuDS solutions.

Towards a Simple and Pragmatic Approach to Deriving Groundwater Salinity Mapping From Airborne Electromagnetics

Kok Piang Tan, Ph.D.
Based on Archies Law, there is not a direct relationship between AEM bulk conductivity and groundwater salinity as other variables such as porosity (lithology), moisture content and cementation come into play. These variables tend to be poorly characterised at the catchment scale, making any derivation of groundwater salinity mapping from AEM problematic. For a study area in the Darling River floodplain of western New South Wales, Australia, the relevant datasets of AEM depth slice conductivity, downhole induction conductivity, pore fluid salinity and pumped groundwater salinity were compared, with the goal of deriving simple AEM conductivity surrogate values for groundwater salinity thresholds. The comparison between pore fluid salinity and downhole induction conductivity highlighted the well-known effect of increased bulk conductivity due to increased clay content. Also, the pore fluid salinity from many shallow samples was relatively high compared to the measured downhole (and AEM) conductivity, due to low moisture contents. The best relationship was between AEM depth slice conductivity and the average pore fluid salinity for the depth slice. For the depth slices dominated by the target aquifer (22-61m), the R2 for the linear regression is reasonable (~0.67-0.83). A percentile ranking approach was then used to derive from these datasets the AEM surrogates for groundwater salinity thresholds. The pumped groundwater salinity data was not necessarily directly comparable with the AEM-derived salinity mapping. This was because the screened intervals could encompass multiple AEM depth slices, different groundwater sampling methods were used and the pumped salinities are biased to the fresh groundwater zones in the target aquifer. It is argued that the simple mapping approach gives inherently conservative estimates of groundwater salinity from the AEM data.

Track 2: Deep Groundwater Applications

Todd Halihan, Ph.D.

An Examination of Geophysical Tools Used in Guiding Assessment of Deep Groundwater – Alluvial versus Fluvial

Brian E. Caldwell, PG, CPG
Past industrial activities within the Rialto-Colton Basin in southern California have resulted in deep perchlorate groundwater impacts in alluvial basin-fill sediments. These sediments are alluvial fan deposits derived from the adjacent San Gabriel Mountains and host internal basin faults that offset groundwater potentiometric surfaces, indicative of a complex flow field which complicates assessment, which in turn necessitates support using geophysical tools. These deposits host groundwater at approximately 400 feet below ground surface, with the base of the flow system at approximately 800 feet. Assessment techniques involve installing well borings using mud rotary techniques, followed by geophysical runs (electric, resistance, gamma) down the borehole. The logs are correlated with the geologist log to identify discrete horizons with the presumed highest contaminant flow velocities, whereupon either a multi-port well or a multiple well cluster within the same borehole is installed to collect data that supports assessment and groundwater modeling. High gamma counts and resistivity generally equate to more permeable horizons due to the granitic component of the sands, and to the inflow of low total dissolved solids in groundwater. Similar assessment and geophysical techniques are used in contamination assessment of deep groundwater in the Long Island Magothy aquifer system, a mosaic of interbedded fluvial deposits. In contrast to the Rialto-Colton Basin example, high gamma counts in fluvial deposits of the Magothy aquifer system tend to correlate to finer-grained material and low permeability.

Applying Geophysical Methods to Estimate Hydraulic Parameters for the Saturated Zones in Lolo Creek, Montana

Ali Gebril
The relationship between aquifer hydraulic conductivity and electrical resistivity has been studied, both in laboratories and on field scale at different locations using different approaches. This relationship lacks dimensionality, therefore, most case studies produced empirical and site specific formulations. The Lolo creek area in Montana undergoes a broad geological and hydrogeological investigation to evaluate groundwater/surface-water interactions. Resistivity measurements taken in the vicinity of Lolo creek and HW 93 used to delineate the saturated zones. Drilling cuts and rock samples from newly drilled wells in the area - provide opportunity to perform successive resistivity measurements at different water salinity, as well as petro-physical and hydraulic measurements. Our goals are a) to use resistivity measurements to extrapolate hydraulic parameters in zones with no wells, and b) to compare between calculated and measured hydraulic conductivities to construct a robust model that could be used at different locations.

Aqueous Rare Earth Elements, Concentration, and Stable Isotopes in Deep Basin Brines, Wyoming

Charles Nye
Aqueous Rare Earth Elements (REEs), stable isotopes, and aqueous geochemistry where quantified in 40 Wyoming deep basin brine water samples from oil and gas (O&G) wells spanning four geologic basins. Measurement of REEs at the ng/L level in high-interference brines was possible thanks to the methods developed by INL co-authors. Isotope, geochemical, and trace analyses were performed at UW and by commercial laboratories.

These deep groundwaters are characterized by their: major ions (sodium-chloride and sodium-carbonate), novel trace-element geochemistry, isotopic shift to the right of the Global Meteoric Water Line (ranging from -87 to -39‰ for δD and -7 to +2‰ for δ18O), and also aqueous REE patterns. All sampled groundwater exhibits similar light REE behavior, but REEs heavier than europium exhibit at least two distinct styles of enrichment. Investigation of these diverse heavy REE behaviors is ongoing, but preliminary results suggest that gadolinium may record the depositional environment of the host aquifer.

The identified chemistry, stable isotopes, and especially the aqueous REE patterns may offer an opportunity to trace deep groundwater flow systems, and study aquifer-scale processes. The REEs are of particular interest as they offer a potential resource to support continued study of saline groundwater, and co-produced groundwater.

In addition to the above possibilities for tracing flow and characterizing deep groundwater. The study includes assessment of water-rock interaction and microbial involvement. The stable carbon isotopic ratios show evidence of microbial activity at some sample sites with ranges from -16.8 to 9.8‰ for δ13C. The above δD and δ18O data suggests prolonged water rock interaction at elevated temperatures, which agrees with the recorded temperatures exceeding 150˚C in some samples.

Future work will allow further characterization of these waters, identification of additional naturally occurring tracers, and improved interpretation of anomalies in REE patterns.

Borehole Characterization of Deep Groundwater in Selected Hydrogeologic Settings of the Marcellus Shale Play

John Williams

Deep groundwaters in selected hydrogeologic settings of the Marcellus shale play were characterized through borehole logging and sampling. The characterized boreholes and their hydrogeologic setting were: 1) three stratigraphic test holes on upland ridges underlain by lower Pennsylvanian, Mississippian, and upper Devonian bedrock; 2) a frac-water supply test well in an upland headwater valley underlain by lower Pennsylvanian, Mississippian, and upper Devonian bedrock; 3) a domestic water-supply well in a tributary stream valley underlain by till and upper Devonian bedrock; and 3) a geothermal wellfield in a major river valley underlain by stratified drift and upper Devonian bedrock The methods used to characterize the deep- groundwater zones penetrated by the boreholes included core and cuttings analysis; petrophysical logging; televiewer and video imaging; fluid-property and flow logging; and open-hole and discrete-zone hydraulic testing and water-quality sampling.

Sparse fractures below depths of 250 meters on the upland ridges and 100 meters in the upland headwater valley produced very small flows of saline water. In the river valley, a laterally extensive fractured zone at a depth of 80 meters produced large flows of saline water. The saline waters in the upland and valley settings were characterized as diluted brines and contained elevated methane of early thermogenic origin. Fractured zones at depths of 200 meters on the upland ridges, 85 meters in the upland headwater valley, and 50 meters in the tributary valley had transitional water quality and lower hydraulic head than the freshwater zones above and saline-water zones below. In the river valley, the fractured top of bedrock at a depth of 45 meters produced freshwater and had lower hydraulic head than the saline-water zones below.

Characterizing Hydrogeological Conditions to a Depth of 1 km in West-Central Alberta

Brian Smerdon, PhD
Unconventional shale-gas plays in west-central Alberta require approximately 30000 m3 of water per well for hydraulic fracturing, which is sourced from surface water and shallow groundwater during the early development stage. However, shallow groundwater availability varies widely and will not be reliable when industry transitions to commercial production. Non-saline groundwater deeper than typical domestic and agricultural uses is considered a potential source, but hydrogeological information is sparse. As part of evaluating Alberta’s groundwater inventory, the Alberta Geological Survey is completing a hydrogeological project for a 22000 km2 region in the west-central part of the province. Regional mapping of total dissolved solids (TDS), opportunistic isotopic sampling (3H, SF6, 4He), and 3D analysis of net-to-gross sandstone ratio begin to characterize deep groundwater. Geological characterization of the uppermost bedrock unit (Paskapoo Fm) shows the unit to be highly heterogeneous with sandstone bodies embedded within a dominantly siltstone and mudstone formation. Groundwater in the Paskapoo Fm has TDS <800 mg/L, and 3H and SF6 concentrations with an apparent age of 30 to 50 years. An underlying bedrock unit (Wapiti Fm) was found to have an upper portion dominated by siltstone and mudstone, and a lower portion with more widespread sandstone. In the Wapiti Fm, TDS varies from 600 to 8000 mg/L, spanning the important saline threshold (4000 mg/L) in Alberta. At one location in the Wapiti Fm where TDS is 1700 mg/L, elevated 4He concentration was found, corresponding to an apparent age of about 135000 years. This study suggests that bedrock units may provide sufficient vertical connectivity to promote circulation of non-saline water to depths of nearly 1 km, and the potential for a confluence of regional flow paths. Although sparse, these data contribute to an understanding of regional water resources and the potential of deep groundwater sources to support unconventional shale-gas in Alberta.

Seismic Attribute Processing to Find Deep Aquifers

John Jansen, P.G., P.Gp., Ph.D.
The scarcity of water in arid and semi-arid regions has increased interest in sources of water much deeper than traditionally considered economic. Many projects have targeted fresh to brackish water sources at depths of 2,000 to over 5,000 feet. In many formations the potential yield of a well varies based on stratigraphic changes making it difficult to predict the potential yield of a given location without more information. The cost of drilling to such depths limits the availability of data and makes developing these resources risky and expensive.

Seismic reflection surveys collect data on the propagation of seismic waves to depths of several thousand feet. Developed by the oil and gas industry, seismic data can be used to map structural features in fine detail. Modern processing and interpretation techniques can map aquifer units, faults, and other structural features that can control well yield. With a little more processing, the shape of the waveforms can identify changes in the stratigraphy, porosity, and pore fluid characteristics in a unit. Seismic attribute processing can be used to identify permeable features such as narrow channel sand deposits at depths of thousands of feet to target permeable zones.

The cost to acquire reflection data is relatively high, which has limited the application of the method for water supply applications. Fortunately many areas have libraries of existing reflection data from previous oil and gas exploration activities. This data can often be purchased for a few thousand dollars per mile and used to map units that can potentially serve as aquifers.

Several case histories will be presented to demonstrate how modern interpretation methods can be used on 2D or 3D seismic reflection data to map features such as sand channels, faults, and shale pinch outs in aquifer units and direct drilling programs toward higher yielding sites.

Ten + Years of Water Level Data from the Regional Deep Carbonate-Rock Aquifer System, Southeastern Nevada

Greg Bushner
This presentation focuses on the characterization of a deep groundwater flow system in southeastern Nevada using more than a decade of water level data collected from wells completed in the Regional Deep Carbonate-Rock Aquifer System (RDCA). These wells were constructed and developed to define the RDCA that occurs in Tule Desert Hydrographic Basin, located approximately 1 ½ hours north east of Las Vegas, Nevada, as part of a water resource development project. Deep groundwater is going to be developed from this basin as this is the available water source which is the principal aquifer in southeastern Nevada. Deep groundwater, as defined for this conference, as that groundwater that occurs beneath the “typical” depth limits of today’s water supplies. The “typical” depth limit is a constantly moving target, especially in the west, where drilling for access to deeper potable water supplies and piping it longer distances becomes economically feasible.

Characterization of deep groundwater begins with the use of field geologic mapping, surface geophysics, and any subsurface data. Once the basic data is collected, as in any well siting characterization study, the drilling program must be defined. Using the subsurface information that’s been collected from the drilling program, a picture of the groundwater flow system can start to be developed. To understand the deep groundwater flow system you first need to understand the geologic framework that supports the hydrology. Using the water level data that is collected overtime, an understanding of the groundwater flow system can be made.