2014 NGWA Groundwater Summit: Alphabetical Content Listing

2014 Birdsall-Dreiss Lecture: Critical Zone Processes at the Watershed Scale: Hydroclimate and Groundwater Flowpath Mediated Evolution of Forest Canopy Patterns

Lawrence E. Band

2014 NGWREF Darcy Lecture — Optimizing Capillary Trapping as a Carbon Dioxide Mitigation Strategy: Pore-Scale Findings in Support of Larger-Scale Implementation

Dorthe Wildenschild, Ph.D.

Academic Contributions to Groundwater Science

Rory Cowie

Changes to Subsurface Metal Mobility in a Bark Beetle-Infested Forest

Kristin M. Mikkelson

Recent large-scale mortality in conifer forests due to beetle infestations has led to changes in terrestrial biogeochemical carbon cycling through the cessation of rhizodeposition and associated large needle drop. As subsurface carbon cycling is altered, aqueous metal transport can also change through complexation with dissolved organic carbon (DOC) that increases its mobility. This study compared DOC and metal concentrations in field soil-water samples beneath beetle-killed trees, along with using laboratory column experiments to determine if subsurface aqueous metal concentrations and loading will increase after beetle infestation. The columns mimicked field conditions by leaching pine needle tea and artificial rainwater through duplicate homogenized soil columns and measuring effluent metal (specifically Al, Cu, and Zn) and DOC concentrations. All three metals were found in higher concentrations in the effluent of columns receiving pine needle leachate. Correlations between DOC and specific metals were observed in both the field and the lab, supporting the hypothesis of DOC-enhanced metal mobility beneath beetle-killed trees after needle drop. Pine needle leachate also contained high concentrations of zinc, which corresponded to high effluent concentrations in the columns along with sorption to the soil matrix. Field concentrations of zinc beneath trees that had already lost their needles were twice as high as samples from under trees that still held their needles, corroborating the observations seen in the column studies. While unclear if manifested in adjacent surface waters, these results demonstrate an increased potential for Zn, Cu, and Al mobility in the subsurface in association with beetle-impacted trees.

Characterization of Groundwater Flow at a Mountainous Watershed, Niwot Ridge, Front Range, Colorado

Sarah Evans

We present a 3D coupled flow and solute transport hydrogeologic model for the Niwot Ridge Watershed in the Front Range of Colorado. This is the first 3D modeling attempt at detailing groundwater recharges at this site. The 7.6 km²watershed ranges in elevation from 3241 to 4082 m and is representative of an alpine setting. Its climate is characterized by a mean annual precipitation of 1.95 m, mean annual air temperature of -2.1ºC, and extensive snow coverage six months of the year with 80% of the precipitation falling as snow. In the middle of the watershed are six paternoster lakes connected by North Boulder Creek, the headwaters of the South Platte River. We use a transient flow and steady state solute transport 3D finite element model to characterize the groundwater and solute transport systems and quantify mountain recharge under averaged long-term conditions.

Field data including effective porosity, hydraulic conductivity, and solute concentration in surface water are utilized to constrain and calibrate model parameters. Preliminary model results indicate that regional groundwater flow is from northwest to southeast, towards North Boulder Creek. This groundwater flow pattern is consistent with field observations. The average hydraulic head gradient over the entire modeled area is approximately 0.12 m/m. Groundwater velocity varies from 1.4 × 10^-6 to 1.8 × 10^-3 m/s. Groundwater flow is primarily driven by a topographically influenced precipitation regime, with 7% of the total precipitation recharging into the subsurface. Modeled baseflow oscillates annually, with peak baseflow occurring after peak snowmelt runoff. Groundwater contribution to baseflow of North Boulder Creek is at an average rate of 0.03 m³/s or 23% of streamflow, which is on the same magnitude as observed values. Modeled discharge solute concentration (Na⁺) output values corroborate with observed surface water values, increasing with a decrease in elevation.

Climatological and Anthropogenic Impacts on Contributions to Urban Groundwater in Los Angeles, California

Tristan Acob

The urban environment greatly alters the paths through which water travels to and from the groundwater system, including increases in imperviousness, groundwater pumping, artificial recharge, leaking infrastructure, and urban irrigation. Many of these pathways are poorly understood, especially in the context of the urban semi-arid environment. Moreover, seasonality, climatic phenomena, and climate change may have notable effects on the characteristics of these urban groundwater fluxes. To analyze the interplay between climate signals and anthropogenic effects, four major groundwater basins in the city of Los Angeles (Central, San Fernando Valley, West Coast, and Santa Monica Basins) are used as a case study. We create a spatially and temporally discretized dataset of the groundwater budget for the years 1990 through 2010 at a monthly time step utilizing observed groundwater level data from wells maintained by the Los Angeles County Department of Public Works (LADPW), precipitation measurements from PRISM, runoff from USGS and LADPW stream gauges in Ballona Creek and the Los Angeles River, evapotranspiration estimates using the Penman Monteith method, and artificial recharge values obtained for the relevant spreading grounds. The effects of various drought restrictions, El Niño/La Niña Southern Oscillation phenomena, and seasonality on the groundwater budget are assessed using correlation coefficients, a principal component analysis, and the Mann-Kendall trend test. Further, projections of the state of the urban semi-arid groundwater system are made with respect to future climate and urban water management scenarios. This study will create a more complete understanding of anthropogenic fluxes and climatic signal effects on urban groundwater and create an important dataset for future work.

Seasonality of Groundwater Recharge in the Basin and Range Province, Western North America

Kirstin Neff

Groundwater recharge is the primary source of replenishment to aquifers, an important source of freshwater for human consumption and riparian area sustainability in semi-arid regions. It is critical to understand the current groundwater recharge regimes in groundwater basins throughout the Western U.S. and how those regimes might shift in the face of climate change, land use change, and management manipulations that impact the availability and composition of groundwater resources. Watersheds in the Basin and Range Province are characterized by a bimodal precipitation regime of dry summers and wet winters. The horst-graben structure of these basins lends itself to orographic and continental precipitation effects that make mountain block and mountain front recharge critical components of annual recharge. The current assumption is that the relative contributions to groundwater recharge by summer and winter precipitation vary throughout the province, with winter precipitation dominating in the northern parts of the region, and summer monsoonal precipitation playing a more significant role in the south, where the North American Monsoon extends its influence. To test this hypothesis, stable water isotope data of groundwater and precipitation from sites in Sonora, Mexico and the U.S. states of California, Nevada, Utah, Arizona, Colorado, New Mexico, and Texas are examined to characterize and compare groundwater recharge regimes throughout the region. Preliminary stable water isotope results from a field site in the Rio San Miguel Basin in Sonora, Mexico indicate that groundwater is composed primarily of summer monsoon precipitation, in contrast to more northern basins where winter precipitation is the dominant source of basin groundwater.

Streambed Hydraulic Conductivity Structures: Enhanced Hyporheic Exchange in Model and Constructed Stream

Skuyler Herzog

Hyporheic exchange is an increasingly prominent topic in stream and groundwater chemistry. The hyporheic zone (HZ) plays a unique role in improving water quality, mitigating temperature fluctuations, and shielding aquifers from contaminated surface water. Whereas streams generally act as transport conduits, the HZ is a dynamic mixing environment that can provide longer residence times necessary for contaminant biodegradation. This study presents the influence of a streambed hydraulic conductivity structure on hyporheic exchange in a constructed stream. The structure, termed a Biohydrochemical Enhancement for Streamwater Treatment (BEST), consisted of a relatively high hydraulic conductivity gravel box in an otherwise coarse sand HZ. Hyporheic exchange was measured during salt tracer additions using time-lapse electrical resistivity surveys. Observations are compared to a MODFLOW and MODPATH (particle tracking) model, and the results are placed in the context of biodegradation of contaminants in recycled water and stormwater.

Announcements

Brine and Deep Aquifers

Robert Sterrett, Ph.D.

Locating, Investigation, and Defining the Pawnee Aquifer, Northeastern Colorado

Theresa Jehn-Dellaport, P.G.

The Cheyenne Basin in northeastern Colorado has been explored and exploited for oil and gas reserves. Due to the numerous oil and gas wells that have been drilled in this basin, there is a proliferation of geophysical logs that has provided a wealth of information that enabled locating and defining an unexplored aquifer. The aquifer is defined through geophysical logs, test holes, production wells, cores, and outcrop data. The aquifer is a fine sandstone, siltstone and is continuous throughout northeastern Colorado.

The Pawnee aquifer is overlain by the Laramie-Fox Hills aquifer which is overlain in some locations by Quaternary eolian and alluvial deposits. The Pawnee aquifer is located in the upper portion of the Pierre Shale and ranges in saturated thickness from 600 to 800 feet. The Pierre Shale was deposited in the deeper waters of the Cretaceous Interior Seaway. The upper units are comprised mainly of shale with the upper several hundred feet containing persistent layers of saturated siltstone and fine grain sandstone, known as the Pawnee aquifer.

MODFLOW modeling of the aquifer indicates that the withdrawal of groundwater is nontributary to the stream system, based on 100 years of continuous withdrawal. A digital model of the base of the South Platte River alluvium was acquired and used for the model.

The Pawnee aquifer is an unexplored deep aquifer that can provide water to local municipalities especially in time of drought.

The Search for “New” Groundwater Sources: Assessing Unconventional Aquifers

Joshua W. Brownlow

The rising demand for energy has driven the innovation for new methods of unconventional natural resource extraction. While the use of such methods remains highly controversial, “new” resources not previously considered accessible, are now economically feasible to produce. Recently, the demand for groundwater has followed a similar trend. Traditional aquifers, highly stressed by rapidly changing demographics, provide an impetus to explore groundwater systems previously disregarded. Brackish water in deep confined systems is currently being discussed as a potential source where treatment or blending with fresher water may allow for increased production. Shallow systems, susceptible to contamination and often considered unappealing as drinking water sources, are now targeted for a variety of non-potable uses. Thin or slowly permeable units with varying water quality may be able to supplement currently produced groundwater or surface water. However, these “new” unconventional sources are neither isolated nor completely independent. The effective and efficient development of these unconventional aquifers will depend upon an organized and discerning approach that evaluates positive attributes and negative consequences. A broad assessment of several unconventional groundwater sources are presented in response to the current Texas drought experience. “New” sources of potential groundwater in the Edwards, Trinity, and Brazos River alluvium aquifers are evaluated along with shallow seasonal flow systems not officially considered aquifers.

Brine and Deep Aquifers (cont.)

Robert Sterrett, Ph.D.

Geologic Carbon Storage in the Lower Ordovician Arbuckle Group Saline Aquifer in Kansas

W. Lynn Watney, Ph.D.

A small scale field test at Wellington oil field operated by Berexco LLC in Sumner County, Kansas will inject up to 40,000 tonnes (770,000 MCF) of CO₂ over approximately nine months into the lower 46 m thick porous and permeable interval of the Gasconade Dolomite in the 300 m thick Lower Ordovician Arbuckle Group saline aquifer. The objective is to validate the predicted CO₂ plume based on a 3D geocellular geomodel obtained from a 3D multi-component seismic volume and two new wells (one cored and both tested) drilled to basement. The plume behavior obtained from a compositional simulation will be tested and validated through visualization, sampling, and indirect detection using an array of monitoring technologies including in situ fluid sampling via U-tube, downhole continuous active seismic monitoring (CASSM), and vertical seismic profiling using acoustic recording from a continuous fiber optic cable installation. Also, CGPS and InSAR for potential surface deformation and a seismometer array will be installed. The CO₂injection, funded by DOE-NETL and cost sharing partners, is pending approval of a Class VI geosequestration permit.

Besides mapping the CO₂ plume dispersal, the test will estimate the tonnage of CO₂ sequestered and refine estimates of the regional carbon storage in the Arbuckle in southern Kansas. The current estimates range between 9-75 billion tonnes in a 9650 km²area that has been extensively characterized by geological and geophysical methods.

Wells in the overlying Mississippian oil reservoir at 460 m above the injection zone and a nest of wells in the USDW will be monitored to detect any leakage. Encompassing static and dynamic models that incorporate Arbuckle injection, caprocks, and freshwater aquifers will evaluate flow, storage, seals, and risk. Best practice methodologies for modeling, monitoring, verifying, and accounting of the CO₂ should provide a framework for carbon management in the midcontinent.

Hydrochemical Implications of Brine Leakage from Subsurface Operations into Freshwater Aquifers

John E. McCray

Subsurface operations that pressurize deeper saline formations, such as energy extraction operations or CO₂ injection for carbon geosequestration, raises concerns that leakage of saline waters will impact water quality of overlying aquifers. This work aims to characterize the geochemical composition of deep brines, with a focus on constituents that pose a human health risk and are regulated by the U.S. Environmental Protection Agency (USEPA). A statistical analysis of the NATCARB brine database, combined with simple mixing model calculations, show total dissolved solids and concentrations of chloride, boron, arsenic, sulfate, nitrate, iron and manganese may exceed plant tolerance or regulatory levels. Twelve agricultural crops evaluated for decreased productivity in the event of brine leakage would experience some yield reduction due to increased TDS at brine-USDW ratios of < 0.1, and a 50% yield reduction at < 0.2 brine-USDW ratio. A brine-USDW ratio as low as 0.004 may result in yield reduction in the most sensitive crops. The USEPA TDS secondary standard is exceeded at a brine fraction of approximately 0.002. To our knowledge, this is the first study to consider agricultural impacts of brine leakage, even though agricultural withdrawals of groundwater in the United States are almost three times higher than public and domestic withdrawals.

Hydrogeological Model of the West Siberian Megabasin

Arcady Kurchikov

Hydrogeological model of the West Siberian megabasin is based on the fluid-geodynamic concept of underground water reservoirs. The concept was presented at the XXVII Session of the International Geological Congress (Moscow, 1984). Allocated three separate hydro pools—Cenozoic, Mesozoic, and Paleozoic. The entire section is divided into seven hydrogeological systems: Oligocene-Quaternary, Turonian-Paleogene, Aptian-Albian-Cenomanian, Neocomian, Upper Jurassic, mid- lower Jurassic, and Triassic-Paleozoic. Due to the accumulated data the Paleozoic-Triassic hydrogeological complex is divided into two independent—Triassic (7) and Paleozoic (8).

To date, based on the deep and ultra-deep bores, 2D and 3D-Geophysical Research set litho-facies composition and reservoir properties of the rocks at great depths, projected oil and gas siliciclastic and igneous rocks of the pre-Jurassic basement of the West Siberian Plain. In various areas established Triassic intrusions in the rift zones and the overlying sedimentary-volcanic rock complexes. In the context of the Paleozoic clastic stand—carbonate strata of the Permian, Carboniferous, and Devonian. Viewing inversion model of ion-salt composition and decrease water salinity with depth. Inversion and micro component composition of the water indicate the shear main zone of oil accumulation in the north megabasin to depths of 5-7 km, in the Triassic and Paleozoic complexes. Thus, as previously performed by V.M. Matusevich hydrogeological parameters regional forecast oil and gas, is confirmed.

Brine and Deep Aquifers (cont.)

Robert Sterrett, Ph.D.

A New Method for Characterization of Porewater Chemistry in Low-Permeability Sedimentary Rocks

Magda Celejewski

Characterization of porewater chemistry in low-permeability rocks can provide insight into the origin and residence time of porewater, the history of fluid movement, and the nature of transport and reaction processes. However, the measurement of porewater chemistry in low‑permeability rocks is challenging because of the small fluid volume and the difficulty of extracting representative samples. Several techniques for porewater characterization are available, but the results they provide can be affected by ion exchange and mineral dissolution, and they may require independent porosity measurements. The objectives of this work are to develop and test a method of extracting representative samples of in situ porewater from low‑permeability rocks and to accurately quantify solute concentrations in the extracted porewater. The method involves extraction of porewater by absorption into hydrophilic cellulosic membranes. The masses of solutes extracted with the porewater are measured by inductively coupled mass spectrometry (ICP‑MS), and the mass of extracted water is measured by near infrared (NIR) spectrometry. In-situ porewater solute concentrations are obtained by normalizing solute mass to water mass. Laboratory experiments using controlled additions of brine to cellulosic membranes confirm that the method is capable of providing porewater solute concentrations with precision and accuracy that are within the limits suggested by USEPA Method 6020A for analysis of saline water samples by ICP-MS. This presentation will provide a detailed description of the absorption method and show the results of a field trial in which concentrations of major porewater ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cl^-, Br^-) in a low-permeability shale (K < 10^-12 m/s, porosity < 10 %) were quantified and compared to results from the crush-and-leach method obtained from paired samples. The results of the comparison demonstrate that the absorption method provides precise porewater chemistry data that are free from ion exchange artefacts.

Application of Resistivity Imaging in the Assessment of Groundwater in Areas of Springs

Mohsen Sherif, Ph.D

A 2D Earth Resistivity Imaging (ERI) survey was conducted in selected water springs areas in the northern region of the United Arab Emirates to assess the available groundwater resources and the possibilities of their rehabilitation for recreational activities. Drilling information of the existing monitoring wells as well as their records of water table elevations and groundwater salinity were used to measure the horizontal and vertical variations in lithology and degree of saturation. The interpretation results of the resistivity data were used to define the potentiality of the fractured limestone and ophiolites aquifer as a strategic resource and determine the location of new production wells. The ERI method was very successful in detecting water-filled fractures and cavities in both of the carbonate and ophiolites aquifers. The results indicated the feasibility of further development of Khatt spring in the carbonate aquifer and Madab spring in the ophiolite aquifer. Results confirmed that the rehabilitation of the Al Ghomur as a recreational spring is feasible.

Characterization of Deep Groundwater Resources at Owens Lake, Inyo County, California

Victor Harris, CHG, CEG, PG

The Los Angeles Department of Water and Power (LADWP) is implementing a dust mitigation program to reduce emissions of fine particulates from over 50 square miles of the dry (terminal) Owens Lake bed in Inyo County, California. Historic total water use has exceeded approximately 80,000 acre-feet per year of high-quality water. With the goal of continuing dust control measures while conserving potable water, the LADWP has evaluated the use of deep groundwater under Owens Lake to supply a portion of the water demand for dust suppression. Methods of characterization of deep groundwater resources have included (1) compilation of existing data and development of a preliminary conceptual model, (2) identification of data gaps, (3) field data collection and revision of the conceptual model, and (4) development and use of a 3-dimensional groundwater model. Field data collection methods utilized include construction and testing of 28 deep clustered monitoring wells, borehole geophysics combined with seismic (reflection) data interpretation, and isotope measurements in groundwater to evaluate the source region of groundwater recharge and the age of the groundwater. The new data, combined with re-analysis of existing data, dramatically improved the hydrogeologic conceptual model for the study area by better defining the hydrostratigraphy, updating the location of key faults, improving estimates on the location and amounts of groundwater recharge, characterizing the interaction between groundwater and surface water, and evaluating sensitive resources such as springs, artesian wells, and domestic wells. The field program identified five discreet aquifer horizons formed by variable depositional environments as lake levels varied through geologic time. A 12-layer MODFLOW numerical groundwater model was developed and used to evaluate groundwater development alternatives and the associated effects on sensitive environmental elements. The model was also used to optimize future well locations, develop protocols for pumping and monitoring, and provide recommendations regarding new well locations.

Characterization of Zonal Variation of Water Chemistry in Deep Groundwater Through Application of Miniaturized Technology

Noah Heller

Over the past decade there has been an increasing need to explore, develop, and monitor deeper groundwater supplies. Critical upfront data to support these efforts comes from test holes and existing wells utilized for groundwater production, agriculture, industry, and monitoring. Impediments to characterize the water chemistry for these depths include the limited lift capacity of small pumps, pump size, and the cost, mobilization, and labor expense of employing large-scale pumps to obtain groundwater samples from depths greater than 1000 feet below ground surface (bgs).

A new class of miniaturized pumps is used on a routine basis over the past10 years with continued improvements. Ranging in in size from 3/4˝ OD to 2˝ OD, these pumps have lift capabilities in excess of 3000 feet bgs. The smallest of this pump class is currently being used to enter groundwater production wells without having to remove line shaft pump turbines and large electric submersible pumps, using the small diameter to successfully catheterize these wells and reach required sampling depths. We will present and explore the advantages and limitations of such devices and provide real world examples from the groundwater and mining industries.

Brine and Deep Aquifers (cont.)

Robert Sterrett, Ph.D.

Effect of Deep Groundwater on Karstification of the Lower Ordovician Carbonate Rocks in Tazhong Area

Wang Lidong

The Lower Ordovician carbonate rocks in the Tazhong area is one of the most important oil and gas reservoirs in the Tarim Basin of China. The heterogeneity of the rocks is very strong. There are mainly three types of karstification: syn-sedimentary karstification, unconformity karstification, and burial karstification in this area. Karstification has an important role in controlling the development and distribution of karst reservoir. The precipitation trend of the buried carbonate calcite or dolomite is affected by the deep groundwater and may control the development and distribution of the karst reservoir. Using geochemical modeling theory of water-rock interaction and combined with the depth and the geothermal gradient, calculation of geochemical thermodynamic parameters of interaction of deep groundwater and calcite or dolomite is carried out. The results suggest that modern burial environment for calcite is in a dissolving tend, and for dolomite in precipitation tend. Strong dissolution trend area of calcite occurs mainly along the fault zone, i.e., along the Tazhong 1 fault and the intersection part of the Tazhong 1 fault and the Tazhong 2 fault.

Passive Grab Sampling for Dissolved Methane at Depth with the Sealed-In-Situ Snap Sampler Device

Kathleen A. Mihm, PG

Deep groundwater sampling has always been challenging due to difficulties with physical retrieval, high pressure pumping lift, and degassing. A relatively new approach, the Snap Sampler, allows the user to deploy double-end-opening sampling containers to depths of at least 2700 feet, limiting some of the problematic aspects of deep sampling. Sample containers are deployed downhole with both ends in an open position, and an electric or pneumatic triggering system is used to release (i.e., “snap”) an internal Teflon-coated spring that secures end caps on the individual sample containers. The pneumatic system is particularly useful for sampling groundwater with potentially ignitable gases (e.g., methane) since the device is made of plastic components and low air pressure (<50psi) is required to trigger closure. Up to six containers can be deployed simultaneously. Different container sizes (40ml, 125ml and 350ml) and materials (clear or amber borosilicate glass and HDPE) are available for the sample bottles so that multiple analytes can be collected together. The sampler system is reusable with replaceable individual sample bottles.

The Snap Sampler system was used for methane sampling at moderate depth (400-800 feet) at a location in Mississippi. Several rounds of samples were collected from 15 wells to assess the effectiveness of the system and to characterize the deep groundwater. Methane concentrations were measured using the Snap method and closely approximated calculated saturation concentrations. Degassing within the Snap Sampler bottles did occur upon retrieval because the bottles are not pressure sealed; however, because degassed vapor and fluid is contained within the vessel, the methane concentrations measured in the Snap vials appear to be representative of downhole concentrations.

Unlock the Opportunity!—A Re-Evaluation of the Lower Trinity Aquifer in Central Texas

Michael Keester

Prolonged drought and regulatory limitations on groundwater production have forced entities to explore alternative sources for water. Recent drilling and successful completion of new production wells to depths as great as 2850 feet in the Central Texas area has revealed that the Lower Trinity Aquifer is much more productive than previously thought and as modeled by the Texas Water Development Board. Examination of drill cuttings from this aquifer revealed thick gravel beds near the base of the formation along with intervals of interbedded coarse sand. The inspection of drill cuttings and subsequent evaluation of geophysical logging aided us in locating these favorable water-bearing zones. One of the production wells we will discuss in our presentation was completed with 342 feet of screen placed within these sand and gravel beds of the Lower Trinity Aquifer. After well completion, a single-well pumping test was conducted to evaluate the aquifer hydraulic properties at the well site. The production testing revealed that the hydraulic conductivity is more than an order of magnitude higher at this site than what is represented in the existing aquifer model used by the state for regulatory decisions. In addition, the thickness of the aquifer is greater than what has previously been reported and modeled. The hydrogeologic information recently collected from the drilling and testing program may unlock the opportunity for producing large water supplies to help meet the demands of this rapidly growing area. This presentation will provide a review of the information collected along with our interpretation of the data and the implications for assessing groundwater availability for the future from this prolific aquifer.

Use of Hydrochemistry and Stable Isotopes for Groundwater Evolution and Contamination Investigations, Jabal Hasouna Reservoir

Fathi Ali Swaid

Hydrochemical and isotopic studies in groundwater was attempted in Jabal Hasouna reservoir to gain knowledge on geochemical evolution and water quality status. The results of the chemical analysis indicate the sources of ions into the groundwater are from dissolution and leaching from source rocks, cation exchange. The saturation index calcu-lated specify over-saturation of carbonate species and undersaturation of amorphous silica indicating groundwater chemical evolution controlled by water rock interactions. Water type alters from Ca-HCO3 to Na-Cl indicating groundwater chemistry controlled by rock-water interaction. The plots of various ionic ratios point out groundwater chemistry affected by ion exchange process, silicate and carbonate weathering. The water type's classification designate 5 distinct groups ranging from low EC and highly depleted isotopes to very high EC with enriched stable isotopic composition indicating longer residence time of groundwater.

Water Sources, Lower Virgin River Basin: Evidence for Deep Groundwater Contribution from Geochemical Tracer Analyses

Joseph Asante, PhD

In the Basin and Range Province deep carbonate groundwater has been suggested as a significant source to many overlying alluvial groundwater basins. Notwithstanding, our knowledge of the deep groundwater is limited because data from such considerable depths are costly and scarce, the geology is complex, and the wells in the alluvial groundwater, which provide most available data, are unevenly distributed.

Lower Virgin River Basin presents an opportunity for testing geochemical tracers in diagnosing deep groundwater contribution to basin-fill aquifers. In this study, historical and newly collected samples from springs, rivers, and wells tapping basin-fill groundwater were classified using major ions and total dissolved solids. Classification is based on a combination of Multiple Discriminant Function and Cluster Analysis allowing for unbiased, reproducible results. Using geologic and hydrologic information and from ordination of the classes based on Na⁺, K⁺, SO₄^2-, and Cl^- ions, six hydrochemical classes are characterized as recharge and discharge end-members and used to define potential sources and movement of water through the basin. Flow dynamics are tested using box-and-whisker plots of deuterium and oxygen isotopic data. The isotopic data reveal that potential recharge waters have significantly high isotopic values whereas the discharge waters have low values. A Wilcoxon Rank Sum test of deuterium isotopic data confirms the difference between recharge and discharge end-members is significant. Except for the class containing floodplain groundwater and surface water, linear and non-parametric regressions, combined with Spearman Correlation, show no significant relationship between isotopic and chloride data. A bivariate plot of deuterium versus oxygen shows that recharge and discharge end-members have significantly different gradients. These data support conclusions that the deep groundwater is an important source to the alluvial groundwater, except for floodplain groundwater, and that combining the classification approach with chemical and isotopic tracers is a powerful tool for diagnosing deep groundwater.

Committee Remarks

Engineers Without Borders

Peter Waugh, PE

Ethics for Groundwater Consulting Professionals

Buie Seawell

Fluids in Human Bodies and Some Parallels to Global Resources and Reactions

Catherine Skinner

Freshwater/Saltwater Interactions

John Jansen, Ph.D., PG

A Design Model for a Scavenger Well Couple in Baton Rouge, Louisiana

Vic Kelson, Ph.D., PE, CGWP

Baton Rouge satisfies much of its public water-supply demands by withdrawing water from deeply buried aquifers that underlie the city. Since the 1960s, brackish water has been migrating into the "1500-foot sand" aquifer, and that brackish water now threatens the long-term sustainability of the Lula pumping station. The author participated in a pair of studies, funded by Baton Rouge Water Company, to assess the potential for halting the migration of chlorides towards the Lula station.

Since the chlorides are concentrated at the bottom of the aquifer, it is desirable to recover as much of the fresh water as possible without resorting to desalinization. It was proposed to construct two nearby wells, one completed in the brackish section of the aquifer and the other completed in the fresh section. By carefully regulating the pumping rates of the two wells, it is expected that the fresh water can be retrieved. However, there were many questions about the design of the "well couple," including the choices of screen length, the locations of the two wells relative to the ambient flow direction, and how well the system would work as brackish water intrusion continued over time.

The author developed a 3D model of a well couple using the 3D analytic element code TimML (Bakker 2005) to evaluate the performance of the well couple, and the effects of various design options. The model made it possible to compare alternative designs and to determine the best arrangement of well screens, evaluate screen length options, and to manage the future continuing encroachment of brackish water in the aquifer. The results of the model were used in the final design of the scavenger-well couple that is now being constructed in Baton Rouge. It is expected that the well couple will be brought online in 2014.

Determination of the Location of the Fresh-Salt Water Interface in Coastal Unconfined Aquifers

Xun Zhou

Mathematical description of the relationship between the fresh-salt water is of important significance in the investigation of groundwater hydraulics in costal zones and evolution of the coastal environment. Examination of the equilibrium status of a point in the salt water zone and the description of piezometric heads at two points in both the salt water and fresh water zones reveals that the location of the fresh water/salt water interface in a coastal homogeneous, isotropic unconfined aquifer can be estimated based on piezometric heads at two points in the same vertical line tapping respectively the salt water zone (including the interface) and the fresh water zone (from the water table to the interface) when the groundwater flow system is in a steady state and satisfies the Dupuit assumption. The Ghyben-Herzberg relation is a special case of these methods and the Hubbert relation is also a special case of these methods. They require two nearest piezometric wells which respectively tap the fresh water and salt water zones. In addition, considering a linear increase or decrease in the hydraulic head in the fresh water zone where the Dupuit assumption is not met, another method for estimating the location of the interface is described based on fresh water heads at two points in the fresh water zone and salt water head at one point in the salt water zone in the same vertical line in the coastal zone. This method using corresponding pressures at the points is also given. The Ghyben-Herzberg relation is a special case of this method. It requires three nearest piezometric wells, two tapping the fresh water zone and one tapping the deeper salt water zone, or three transducers installed in one well, two in the fresh water zone and one in the deeper salt water zone.

Evaluating Coastal Aquifer Recharge as a Barrier to Saltwater Intrusion and Improving Aquifer Water Levels

Richard Walther, P.G.

West Central Florida has exhibited declining groundwater levels in the Upper Floridan aquifer over the last 50 years in the area of southern Hillsborough County and western Polk County. These water level declines have caused saltwater intrusion along the coastal area of Hillsborough County. The Southwest Florida Water Management District (District) designated this area as the Southern Water Use Caution Area (SWUCA) to limit additional groundwater withdrawals and implemented a recovery strategy to mitigate the Most Impacted Area (MIA) that exhibited the greatest water level decline.

The District initiated an aquifer recharge feasibility study to identify recharge concepts that may provide the highest level of beneficial use of locally available reclaimed water flows. This study concluded that coastal aquifer recharge can be a viable permittable solution to support recovery of declining water levels in the SWUCA. The District implemented a regulatory water level mitigation policy that would allow groundwater mitigation offset credits to be earned for up to 90 percent of the regional water level improvements within the SWUCA which may be used to develop future water supplies further inland.

The county has taken the regional initiative by implementing an aquifer recharge pilot project to beneficially utilize available reclaimed water as a saltwater intrusion barrier and for the improvement of aquifer water levels. The pilot project includes construction and injection testing of an aquifer recharge well and development of a semi-regional variable-density groundwater model to assess the system’s ability to impede saltwater intrusion and improve aquifer water levels. The pilot project will also evaluate the potential for mobilization of arsenic within the aquifer recharge zone during operation of the recharge system.

This presentation will explain site hydrogeology, conceptual site model, and numerical model development, as well as the results that will be used to evaluate the regional aquifer recharge system.

Hydrogeochemical Investigations and Solute Transport Modeling of Polluted Coastal Aquifer

Venkateswara Rao Bekkam

In this paper, the extent of sea water intrusion and groundwater contamination due to aqua ponds are investigated through hydrogeochemical studies along with solute transport modeling of the aquifer. The study area is an interstream region of the Pennar and Upputeru Rivers located in the Nellore district of Andhra Pradesh, India, covering an area of 529 km². The groundwater levels and samples are collected in the 196 observation wells to prepare groundwater contour maps and to analyze the groundwater samples for various chemical parameters. Occurrence of saline water in certain localized pockets due to intensified aquaculture and occurrence of saline water along the coast due to sea water intrusion are verified by various ionic ratios like Ca⁺²/Mg⁺², TA/TH, Na⁺/Na⁺+Cl^- and Cl^-/CO₃^-2+HCO₃^-.

The above investigations have revealed that all along the coast, with a strip width of 2 to 5 km, groundwater levels are below the sea level at an average depth of 3 m below ground level; consequently there is seawater intrusion with TDS concentrations ranging from 1500 to 2500 mg/L along this strip. Similarly, the TDS values were found to be as high as 5000 mg/L at a localized pocket at T.P.Gudur due to storing of sea water meant for aquaculture. The ionic ratios are confirming the presence of seawater in these localities and along the coast. In general, the seawater spreading is more during the pre-monsoon season and it is considerably diluted in the post-monsoon season. The solute transport model indicates that the lateral spread of saline water towards inland is not occurring farther beyond a 2 to 5 km strip due to higher topographic elevations and the groundwater is following the topography. In the contaminated strip, the model predictions are made up to the year 2052 with respect to its vertical and lateral spread.

Freshwater/Saltwater Interactions (cont.)

John Jansen, Ph.D., PG

Geophysical Exploration of the Solidaridad Municipality, Riviera Maya, Mexico

Rosa María Leal Bautista

As water availability in Mexico is decreasing (Marín et al, 2014), there has been strong interest in developing hydrogeologic reserves, particularly in the Peninsula of Yucatan. Escolero and others (2005) proposed a hydrogeologic reserve for NorthWestern Yucatan Peninsula. Other scientists both from the Centro de Invesitación Científica de Yucatán and from the Universidad Autónoma de Yucatán have been conducting studies to identify potential sites for reserves for the City of Merida, in the State of Yucatan.

In this abstract, we present the results of the geophysical exploration in the Municipality of Solidaridad, which is located in the Riviera Maya. This area is one of the fastest growing urban areas in Latin America. Thus, assessing groundwater resources in the region is critically important for the future of this region.

Throughout the area there are numerous sinkholes, locally known as cenotes. We were able to field truth the vertical electrical soundings at one of the sinkholes. In this particular case, we have a very thin unsaturated zone, followed by approximately 12 meters of fresh water. The fresh/salt water interface is less than one meter thick.

We also surveyed a number of wells and we tied in our survey to INEGI´s (Instituto Nacional de Estadística, Geografía e Informática) first-order survey benchmark close to the study area. Thus, we were able to calculate the thickness of the freshwater lens using both the Ghyben-Herzberg ratio, and the geophysical exploration.

Mapping Shoreline Groundwater Interactions in Southern California Using Geophysical Methods

John Jansen, Ph.D., PG

The interface between fresh groundwater and saline water in coastal areas is frequently complex. The natural discharge of groundwater to the near shore zone is controlled by multiple factors, including the permeability of the aquifer system and the hydraulic gradient in the aquifer. The natural balance is often disturbed by heavy pumping on shore that can cause significant intrusion of salt water into the onshore portion of the aquifer. The shape of the salt water wedge is affected by the pattern of pumping, the properties of the aquifer, and hydraulic boundaries like faults and confining units.

Generally it is impossible to accurately map the pattern of the salt water/fresh water interface with boreholes and monitoring wells due to the cost of drilling, the limited three-dimensional resolution that can be provided by wells with long screened intervals, and the expense of drilling offshore. Several electrical geophysical methods can be used onshore and offshore to map the location of the interface. These methods are faster, much less expensive, and can provide a higher level of three-dimensional detail on the position of the salt water plume. The methods can be used to select optimal locations for monitoring wells, confirm the performance of salt water intrusion barriers, or calibrate solute transport models.

This presentation uses three case histories from southern California to demonstrate how electrical resistivity and time domain electromagnetic induction methods have been used to map salt water intrusion as it moves onshore in a faulted and layered multiple aquifer system, map the migration of remnant salt water plumes behind barrier wells systems, and map the differences in offshore discharge of groundwater in undisturbed aquifer systems as a function of aquifer properties.

Geochemistry, Isotopes, and Tracers

A. Scott Andres

Evaluation of Physico-Chemical Characteristics of Ground Water of Bhiloda Taluka, Sabarkantha District, Gujarat, India

Manisha N Desai, Ph.D.

The present investigation deals with the assessment of water quality of a well and tube well situated at different villages of Biloda Taluka. A total of 149 sources were selected from different locations for this study. The investigations were made in the pre-monsoon, monsoon, and post-monsoon season of 2011-2012 to evaluate the suitability of water for domestic, agricultural, and drinking purposes. Water parameters regarding temperature, turbidity, pH, electrical conductivity, dissolved oxygen, biochemical oxygen demand, bicarbonate, chloride, calcium, magnesium, and total hardness were analyzed. Variation in the values of these parameters is not significant in different seasons. Comparison of water quality with national and international standards revealed that all the parameters were within permissible limits of drinking water standards. Attempts were also made to find out reasons for degradation of water quality and bring awareness to villagers for taking care to use this water for drinking purposes.

Geochemical Control of Arsenic, Gross Alpha, and Ra-226/Ra-228 Groundwater Impact at a Coal Combustion Plant

Matthew Gozdor, MS

An electric power utility company conducts routine groundwater sampling at its facility in central gulf coast Florida (“site”) according to the facility’s industrial waste water permit. Results of this sampling have identified select areas of groundwater with elevated concentrations of arsenic (As), radium (Ra-226 and Ra-228), and gross alpha (GA). A Plan of Study (POS) was developed as required by the State to evaluate potential sources and transport mechanisms for these constituents, site geology and hydrogeology, and potential remedial alternatives. The POS included: (i) evaluation of in-well and intra-well geochemical changes between subsequent groundwater monitoring events; (ii) evaluation of major ion chemistry and stable isotope data; (iii) performance of As, GA, and Ra 226/228 seawater leachability tests on site soils and limestone; and (iv) performance of a column soil and bedrock test to evaluate Eh changes on As solubility.

The evaluation indicated that As, Ra-226/228, and GA have been liberated from the soil and native limestone at the site and neither the lined coal pile nor the coal combustion product ash storage/disposal area, nor other sources such as plant industrial wastewater being directed to percolation ponds, is the main source of arsenic within the groundwater monitoring wells. Rather, the constituents of concern are a result of geochemical changes in the shallow groundwater due to anthropogenic activities (e.g., compaction grouting, installation of large liners, presence of storm water features, etc.) and as a result of sea water intrusion in the vicinity of the discharge canal. Overall, the evaluation of geochemical data has allowed us to support and confirm the assertion that site processes did not cause groundwater contamination.

Use of Radiocarbon Dating to Evaluate Sustainability of Groundwater Pumping in Delaware

A. Scott Andres

New test data that show the presence of groundwaters with conventional radiocarbon ages between 9,600 and 16,200 years in test wells finished in the Piney Point, Rancocas, and Mt. Laurel aquifers in the Coastal Plain of southern New Castle and northern Kent Counties, Delaware. Sample depths range from 155 to 525 feet below land surface. Model corrections to radiocarbon ages, done to adjust for aquifer matrix effects, range from 10 to 30 percent.

Conceptual models and simulations both show that prior to onset of groundwater use, groundwater entered the system in the northwest and flowed to the southeast down the regional dip of the geologic units and toward the regional discharge areas in Delaware Bay or the Atlantic Ocean. Pumping has reduced the potentiometric surfaces in the aquifers by tens of feet. Though heads still exceed the tops of aquifers by significant amounts, there is concern for intrusion of deeper saline water.

Comparison of these ages with flow-model estimated ages for pre-pumping groundwater flow conditions indicates that observed ages are thousands of years older than expected suggesting that pumping has significantly altered both potentiometric surfaces and flow paths. Older water is now being pumped back from deeper, previously downflow sections of the aquifer. Regular salinity and monitoring and additional radiocarbon dating will continue to be done to evaluate trends.

Geochemistry, Isotopes, and Tracers (cont.)

Marcia Schulmeister, Ph.D., P.G.

Detection of Discontinuities in a Discontinuous Permafrost Aquifer Using Stable Isotopes and Groundwater Temperature

David Barnes, Ph.D., P.E.

Both stable isotopes and temperature have been used as tracers in many hydrogeological studies. In the study we present here we use both tracers to delineate the location of discontinuities in a contaminated aquifer located in a region of discontinuous permafrost in the Interior of Alaska and to understand groundwater flow in the aquifer. In areas impacted by permafrost, frozen ground acts as an impermeable barrier between the suprapermafrost and subpermafrost portions of the aquifer. Discontinuities in permafrost are areas of possible connection between these two main portions of the aquifer. In contaminated aquifers these areas of connection between the two portions of the aquifer influence the transport of contaminants, necessitating the delineation of these discontinuities and the determination of the influence they have on the groundwater flow. To locate possible discontinuities in this study, multiple groundwater samples were obtained in the supra and subpermafrost portions of the aquifer prior to the 2013 spring thawing period and analyzed for ¹⁸O and ²H. During this period the groundwater aquifer is thought to be close to steady state owing to an overall slowing of recharge during the winter months when atmospheric temperatures rarely rise above freezing. Groundwater temperatures with depth were also measured. Results from these measurements show contrasting trends in δ¹⁸O and δ²H as well as temperature between areas known to contain permafrost and areas of no documented permafrost. Moreover, the spatial trend in δ¹⁸O and δ²H indicate areas of possible groundwater interaction with surface water. Additional rounds of sampling occurred during the 2013 summer and fall seasons for further delineation and comparison.

Groundwater Dye Tracing in Lusaka, Zambia: Delineation of Contribution Areas for Drinking Water Sources

Jonathan Levy, PhD

Lusaka, Zambia is a fast-growing city with more than 2 million people straining the karst groundwater which supplies 50% of its population. A well-developed epikarst underlying much of the city is often exposed by mining, increasing groundwater vulnerability. In densely populated areas, without proper waste or sewage disposal, drinking-water quality is severely degraded. To sustainably manage groundwater quantity and quality it is important to know groundwater recharge areas, flow paths, and travel times. Groundwater dye tracing is a commonly applied tool for such investigations but has not previously been used in Zambia.

Investigations focused on the community of Muloni, an unplanned development on the Cheta Limetsone west of Lusaka. Adjacent to Muloni is a commercial quarry where groundwater is intensively extracted. Muloni residents derive water from springs, boreholes, and hand-dug wells. Dye-tracing goals included delineation of source-water areas, quantification of groundwater travel times, and assessment of the possible effects of pumping at the quarries on drinking-water sources. Water quality assessments, based mainly on E. coli concentrations, were used to select the initial sites for the dye-trace injections.

Water quality results suggested separate recharge areas for some of the deep boreholes and the quarry (15 m below the village) which were relatively free of E. coli. The springs, shallow wells, and some boreholes seemed directly plumbed into the epikarst with E. coli concentrations in excess of 300 CFU/100 mL. Pumping from the quarries has resulted in no apparent reduction in spring flow.

Charcoal dye receptors were placed at springs, quarries, and shallow wells. Five liters of approximately 400 ppb Rhodamine WT and Fluorescein were injected into two different latrines upgradient of springs and wells. Receptors were collected and analyzed weekly over about three months, but no breakthrough was observed. Dye tracing experiments continue with higher dye concentrations at additional injection points.

Hydrologic Controls on the Extent of the Kasota 7 Calcareous Fen, Le Sueur County, Minnesota

Matthew Uliana

Calcareous fens are defined as ground- and surface-water supported wetlands that contain a plant assemblage dominated by calciphilic (i.e., “calcium-loving”) plant indicator species. These fens are also defined by a set of criteria that include continuous groundwater discharge that is sufficient to maintain soil saturation, histosol soils containing a significant fraction of calcium carbonate minerals, and various water quality parameters.

The Kasota 7 calcareous fen is a legally protected wetland area located in Le Sueur County, Minnesota, in the floodplain of the Minnesota River. Geochemical and head data indicate that fen waters are derived from about 35% fresh water (river and local meteoric water) and 65% groundwater discharge from the Cambrian Jordan Sandstone aquifer, with no contribution from other potential surface and groundwater sources.

Soil samples from the calcareous fen indicate average Ca concentrations of about 21% (dry weight) for the calcareous fen soils vs. <8% for non-calcareous peat soils adjacent to the fen. Geochemistry and stable isotope data indicate that the carbonate material in the fen soils are precipitates from groundwater discharge rather than detrital carbonate minerals derived from overlying Ordovician Prairie du Chien Group sediments. Carbon-14 data indicate a maximum age of 850 (±100) years bp for fen peat material.

Based on the local groundwater hydrology, we should expect to see calcareous fens throughout the local floodplain of the Minnesota River. Fen occurrence, however, is limited to a few isolated locations, suggesting that some non-groundwater-related factor is controlling and limiting floodplain fen occurrence. Using field observations, survey data, and historic river stage data, we have concluded that calcareous fen occurrence is controlled by the maximum river stage during major flooding events. We hypothesize that fresh water flood events flush out carbonate particulate matter, rendering the most frequently flooded peat soils unsuitable for the calciphilic plant species.

Sorption and Transport of Bisphenol A (BPA) in a Palygorskite-Montmorillonite: Effect of Granule Size

Tedros Berhane

Bisphenol A (BPA), a basic monomer used for synthesis of epoxy and polycarbonates, is a frequently detected endocrine disrupting compound in the environment. Palygorskite-montmorillonite (PM) has high sorption capacity for a variety of organic compounds and was studied as a potential inexpensive and recyclable supplementary wastewater treatment technology for removal of BPA. The emphasis was on determining an optimum granule size (0.6, 1.7-2.0 and about 2.8 mm) for maximizing water flow while still achieving contaminant attenuation. Laboratory batch sorption and column-transport experiments were conducted. Continuous-source, 1-D, BPA transport experiments along with bromide as a conservative tracer were run. Contaminant breakthroughs were simulated and transport and all reaction parameter values under flow-through conditions were estimated using CXTFIT, a USGS 1D contaminant-transport model. Parameter estimation was compared to and constrained by results from batch sorption experiments.

Kinetic and equilibrium sorption experiment data fit a pseudo-second-order kinetic and Freundlich sorption models, respectively. In addition to a higher overall R-squared value, the pseudo-second-order kinetic sorption model estimated a more accurate maximum sorption capacity. The rate of BPA sorption was faster during the first 50 minutes with an intermediate rate followed by very slow sorption before reaching an apparent equilibrium. We hypothesize that during the first stage, sorption dynamics was fast due to faster BPA diffusion rate across a liquid-solid boundary layer followed by a gradually slower sorption rate limited by intra-particle diffusion. The final stage of very slow sorption may indicate diffusion across the boundary layer and the intra-particle pore spaces.

Generally, the BPA sorption capacity was highest for the smallest granule material followed by the medium and the largest granules. BPA removal percentages varied from 50-70, 27-38, and 15-20 for the smallest, the medium, and the largest granules, respectively. Sorption-desorption hysteresis was observed by the three granules, indicating irreversible sorption process taking place.

Stable Isotopes of Hydrogen and Oxygen as Hydrologic Tracers of Aquifer Recharge

Nathan Moxley

Groundwater levels have been declining in the Grande Ronde basalt aquifer of the Palouse Basin in southeast Washington and northern Idaho at an average rate of approximately 0.4 m (1.3 ft) per year for more than 80 years. Repeated studies have demonstrated the apparent age of this water to be >10,000 years, suggesting primary recharge during the Pleistocene, and implying modern recharge is extremely limited. Approximately 60,000 people across the Basin depend on this aquifer for drinking water, and although much has been learned over the past 50 years of study, no sources of recharge have been definitively identified.

Utilizing data from precipitation and surface water across the Basin, stable isotopes of oxygen and hydrogen (δ¹⁸O and δ²H) were used as hydrologic tracers to investigate water movement along a portion of the South Fork of the Palouse River (SFPR). Stable isotope data and more traditionally collected hydrologic information, including water levels and tritium (³H), are all consistent with the premise that this reach of the SFPR is a losing stream. Combined with X-ray fluorescence spectroscopy (XRF) data from previously unsampled basalt outcrops, the isotope data suggest that stream loss is contributing recharge to the deeper basalt aquifers.

Groundwater stable isotope data have also yielded unexpected clues to the structural geology along the study reach, suggesting the orientation of subsurface folding or faulting, inferred from what appears to be directional recharge. In addition, stable isotope data have proven to be a valuable tool in identifying anthropogenic input to the hydrologic system, clearly identifying input from wastewater treatment plants.

This study illustrates the increasing usefulness of stable isotopes for water resource groundwater investigations, providing high quality data at a fraction of the cost of alternatives such as ³H, ¹⁴C, and more involved traditional hydrodynamic methods which may not always be feasible.

Groundwater Management

Paul Barlow

Economic Effects of Removing the Permit Exemption for Domestic Wells

Shane Johnston

Water scarcity in the western United States has forced elected officials and water resource managers to reconsider the appropriateness of exempting “de minimus” water withdrawals from state permitting processes. A number of western states have attempted to either remove or significantly restrict the permit exemption in recent years, mostly with limited success (Bracken 2010, 2012). Through a case study of Kittitas County, Washington, this article assesses common criticisms of removing the exemption, namely that the policy makes the price of acquiring water unaffordable, drives the rate and location of local development, and redistributes the property tax burden. I report descriptive statistics of transaction costs and gross selling prices for over 230 county water right transactions since 2006. Gross selling prices paid for previously permit-exempt water ranges between $5900 and $11,000 per estimated residential unit (approximately 0.17 acre-feet). On a per acre-foot basis, this is high relative to prices observed for agricultural-to-urban water transfers in the western United States. I also forecast property tax redistribution through use the Assessor’s Property Database and a public records request for 711 Petitions for a Reduction in Assessed Value filed by county residents following rule adoption. Redistribution effects depend on the scale and type of public service provision for each of the county’s 56 tax code areas. Sensitivity analysis is conducted on the effect size, which varies from as little as 2.0% for some countywide services with greater and more variable effect sizes found for individual tax code areas in the Upper County. A Difference-in-Difference model examines the policy’s impact on development, measured through approved applications for (1) new wells and (2) new building permits since 2006. This is one of the first ex post analyses of the economic effects of removing a permit exemption for “de minimus” water withdrawals.

Groundwater Deficit and Land Subsidence in the Lerma-Santiago-Pacifico Watershed, Mexico

Pascal Castellazzi

Groundwater is the main source of water supply in the Lerma-Santiago-Pacifico watershed. In the last decades, overexploitation of the aquifer led to environmental and socioeconomic issues, impacting more than 25 million Mexicans.

In this project, gravimetric data from GRACE satellites, radar data from Radarsat-2, and field data are combined and interpreted. The study aims to evaluate: (1) the deficit at the scales of major cities (Toluca, Aguascalientes, Guadalajara, Querétaro, Morelia, León, and Celaya); (2) the consequences of this deficit: land subsidence and surface deformation; and (3) the accumulated impacts of the local deficits on the hydrogeological dynamics of the watershed.

GRACE data have been generated since 2002, measuring large scale gravimetric variations. Total water storage variations are extracted from these data, resulting in a combination of four signals: (1) unsaturated soil water storage; (2) surface water storage; (3) snowpack water storage; and (4) groundwater storage. A proper estimation of these parameters allows the user to extract the remaining parameter. In this study, groundwater storage variation are extracted and interpreted along with field and InSAR data.

InSAR techniques allow a complete monitoring of the land surface deformations over the watershed. Results can be interpreted along with lithology and water extraction data. A numerical model combined with a subsidence module can be calibrated using results of land subsidence gradient maps from InSAR. Nowadays, new PS-InSAR techniques of land subsidence monitoring are evolving toward a better understanding of spatial and temporal variations of soil surface, allowing a better estimation of underlying hydrogeological processes.

In this session techniques, principles, and limitations are presented, as well as the first results on the evaluation of the groundwater storage variations and mapping of land subsidence over the watershed.

Groundwater Management and Governance: A Policy Perspective

Sharon B. Megdal, Ph.D.

Groundwater availability, utilization, and quality are worldwide concerns. In the context of some international efforts related to groundwater governance and transboundary groundwater assessment, the presenters will discuss the methodology utilized and results from an initial nationwide survey conducted on U.S. groundwater governance. General findings include the following. There is diversity in terms of the users of groundwater subject to state groundwater regulations and in the tools and strategies employed to manage groundwater use and quantity. Groundwater governance priorities vary by state. Significant variance exists in recognizing the connection between surface and groundwater and in considering the water needs of groundwater-dependent ecosystems. Survey respondents report differences in terms of agency capacity to carry out policies and responsibilities, and the public accessibility of groundwater information. The presenters are very interested in interacting with attendees to solicit feedback and suggestions regarding additional research. The report, Groundwater Governance in the U.S.—Summary of Initial Survey Results, can be found at wrrc.arizona.edu/groundwater.

It’s Not a Savings Account: Using an Accurate Analogy for Groundwater’s Role in Ecohydrology

Gilbert Barth, Ph.D.

Groundwater can significantly buffer surface water variability and drought impacts on ecohydrology. As such, groundwater is often considered a sort of savings account, a resource that can be tapped with minimal costs. However, this analogy is misleading. In most cases groundwater is more analogous to a credit card with transaction fees, limited grace periods, interest rates, and potential penalties. The credit card analogy is a simple, effective way to convey to a wide audience the potential for propagation of groundwater impacts in the ecohydrologic system. A series of examples are used to demonstrate the credit card analogy, show how the savings analogy does not work, and motivate a more accurate understanding of groundwater pumping on ecohydrology. Approaching groundwater as a credit system improves our ability to anticipate future ecohydrologic impacts, assess potential costs, and make decisions based on a better conceptualization of the hydrologic system.

The State of Water Resources Around the World and Future Challenges in the United States

Nicholas Albergo, P.E, DEE

The world has a total of 1.4 billion cubic kilometers of water, but almost 98% of this is saline. Of this limited fresh water, more than half is permanently locked away in ice or exists as deep fossil water which is not, at present, economically reachable. Demand for fresh water has increased eightfold since the beginning of the 20th century. It will double again by 2050. Historically, about 20% of the earth’s land surface experiences drought at any one time. This has now risen to 28%, and is set to rise to 35% by 2020. Over the last 10 years, areas affected by the most severe droughts have risen from 1% to 3% of the planet’s landmass.

Today, 80% of all disease and more than a third of the deaths that occur in developing countries are caused by contaminated water. The situation is always worse in the teaming slums and shantytowns that grow up on the edge of great cities, often as a result of migration from rural areas. History has confirmed that a lack of clean water can not only cause health problems such as diarrhea, dysentery, and cholera, but also leads to mass migrations and failed governments and that is the subject of my talk. Groundwater professional engineers will benefit by focusing their expertise in the areas of surface water management, storage, and treatment and reuse, in addition to protecting our groundwater supplies, as this expertise will be in great demand in the United States and abroad in the years to come.

What Lies Beneath? Assessing and Compensating for Groundwater Contamination

David Askman, JD

Contamination of groundwater from industrial and disposal facilities and practices can pose a significant threat to ever important groundwater resources. That groundwater is typically owned, managed, and/or held in trust by governmental entities which have the ability to regulate ongoing activities and, importantly, remedy past ones. Many federal, state, and Tribal governments have undertaken assessment of groundwater contamination and identified approaches to compensate for the years of contamination. This presentation will discuss the key legal and economic approaches and challenges to assessing the extent of groundwater contamination, and determining appropriate types and amount of compensation. In any situation, there are a variety of economic and equivalency options for valuing both a contaminated or lost groundwater resource and the services which it provides. We will address several of those options and the manners in which compensation for those losses can be pursued, and provide case examples.

Groundwater Management (cont.)

Paul Barlow

Adventures in Designating the Mahomet Aquifer of Illinois as a Sole Source Aquifer

Allen Wehrmann, P.E., P.H. (GW), D.WRE

The Sole Source Aquifer (SSA) Program was an original part of the Safe Drinking Water Act of 1974. SSA designation is intended to protect critical groundwater resources for public health and long-term economic development and is designed to protect aquifer quality by adding a USEPA review component to certain federally-funded projects. Some 73 aquifers have been designated as Sole Source Aquifers, but none in almost 20 years. Recent threats to the Mahomet Aquifer in Illinois spurred a coalition of communities to seek ways to protect the aquifer, one of which was to seek designation of the aquifer as an SSA. The Mahomet provides drinking water to an estimated 700,000 people including ~120 communities and thousands of rural residents. SSA designation efforts were initiated when application to USEPA Region V was submitted in December 2012. On a purely technical level, the aquifer clearly falls within the definition of a SSA. However, concerns have been raised regarding possible unintended consequences resulting from designation. A discussion of the designation process and pitfalls, and the importance of public education and input, will be presented. As of November 2013, no decision on designation had been made.

Alabama Groundwater: Policy and Management Based on Comprehensive Hydrogeologic Data

Marlon Cook

Alabama is blessed with abundant groundwater resources from more than 25 major aquifers that provide public water supplies for more than 70% of the geographic area of the state. Alabama Governor Robert Bentley and the Permanent Joint Legislative Committee for Water Policy and Management have joined to initiate the development of a water resource management plan and water policy legislation in Alabama. These state leaders understand that water policy must be based on sound scientific data. Therefore, the Groundwater Assessment Program at the Geological Survey of Alabama has been mandated to conduct a comprehensive statewide assessment of groundwater resources. This assessment consists of 15 parameters that include quantitative and qualitative evaluations that will guide legislation and future development of groundwater resources in Alabama. The assessment includes methodologies modified from oil and gas exploration as well as traditional hydrogeologic and geochemical investigations. Groundwater availability is determined by a combination of aquifer storage and recharge estimates and current production impacts from evaluations of groundwater levels and drawdowns.

Improving Groundwater Management in the South Platte Alluvial Aquifer

Reagan Waskom, Ph.D.

Groundwater pumping from high capacity wells located in the South Platte alluvial aquifer in northeast Colorado was estimated to be nearly 500,000 AF annually prior to significant administrative changes that occurred in the early 2000s. Currently, it is estimated that closer to 450,000 AF are pumped annually in the basin, while augmentation of pumping has increased dramatically over the past decade. Concerns have arisen in recent years about well curtailments and possible over-augmentation leading to high water tables. In 2012 the Colorado Legislature passed House Bill 12-1278, titled Concerning the Authorization of a Study of the South Platte River Alluvial Aquifer. The Act directed the Colorado Water Institute at Colorado State University to conduct a study of the South Platte alluvial aquifer to identify and delineate areas within the basin adversely impacted by high groundwater levels and to conduct a feasibility-level evaluation of the causes of high groundwater levels in the affected area, and determine if expanded utilization of the aquifer is feasible. HB1278 did not authorize modeling studies, but rather an evaluation of the available data to address the objectives of the Act. Our general plan of work for this study was to use the existing data tools in the South Platte Decision Support System (SPDSS) developed for CWCB as part of the Colorado DSS (CDSS). We used the SPDSS to develop datasets on groundwater levels, surface and groundwater diversions, river flow, call records, stream gain and loss, augmentation, artificial recharge, phreatophytes, and other factors for analysis. While high groundwater levels are found throughout the basin, problems impacting homeowners are observed to be localized and care must be exercised not to overreach when applying solutions.

Water Management Improvement Strategies for the Kansas Lower Republican River Basin

Susan Stover, P.G.

Kansas’ Lower Republican River (LRR) basin has competing needs for its limited water supplies: irrigation, recreation, wildlife areas, municipalities, and minimum streamflow requirements. To improve management options, Kansas entered into a WaterSMART Basin Study with the Bureau of Reclamation and the states of Colorado and Nebraska. The study covers the entire basin and evaluates proposed structural and operational changes in both Nebraska and Kansas. Five alternatives and a no action baseline are examined through hydrologic modeling, economic analysis, and public input to determine their ability to meet demands, be interstate compact compliant, be cost effective, and maintain the ecological function of the river under current and future conditions. Alternatives evaluated within Kansas are the expansion of Lovewell Reservoir by 16,000 AF, 25,000 AF, and 35,000 AF, with the automation and winterization of the Courtland Canal and the off-season storage of water from Lovewell or Courtland Canal in Jamestown Wildlife Area, which is then re-released to the Republican River when other demands increase.

To evaluate these alternatives, the Kansas research team coupled an integrated surface water/groundwater flow model (HydroGeoSphere) and a surface water operations model (OASIS) to characterize the response of the LRR to changing climate conditions and upstream management alternatives. The LRR hydrology is complex with many natural and engineered components that control water flow, and these components are well captured in the coupled model framework for the LRR. For future climate projections, precipitation and temperature conditions are downscaled data from 112 global climatic projections and reflect a central tendency, the 25% (warmer and wetter) and the 75% range (more warmer and drier).

The basin study paves the way for funding a feasibility study and implementation of the best suited alternatives to improve water management in the basin.

Groundwater Management (cont.)

Paul Barlow

A Groundwater Management Toolbox—Anticipating Coordinated Management of Indian and Non-Indian Water Rights

Deborah L. Hathaway, PE

A Groundwater Management Toolbox was developed to support water resource management on the Flathead Indian Reservation in Montana, one component of unitary management of Indian and Non-Indian water rights envisioned during negotiations towards quantification agreements. The proposed water rights settlement agreement was not ratified, sending parties into an alternate adjudication path. Nevertheless, some form of coordinated groundwater management may ultimately develop, and management can benefit from information easily accessed through the Toolbox.

The Toolbox provides a graphical user interface through which groundwater declines and stream depletion from existing and proposed wells can be evaluated. Water managers can specify information on well location and pumping rates, then implement simulations of impacts using an underlying groundwater model developed with MODFLOW. Results including maps, tables, and graphs are provided as on-screen graphical displays for rapid evaluation and can be exported as GIS shape files or to Excel files. Simulations of permitted wells, proposed wells, and custom simulations can be executed without the need to locate, open, and manipulate the actual MODFLOW files.

The Toolbox is illustrated for the Jocko Basin, located in the southernmost part of the Flathead Reservation. The underlying Jocko Basin Model simulates groundwater flow within the alluvial aquifers and exchanges with surface streams. Modeled recharge includes mountain-front recharge, stream and canal seepage, and infiltration of excess applied irrigation water. Groundwater discharge occurs through pumping wells, evapotranspiration, springs, and to streams. The Toolbox initiates with a historical base case condition. From user input, the Toolbox runs the groundwater model and provides summaries of existing conditions, incremental drawdown from proposed pumping, cumulative drawdown from existing and proposed wells, and stream depletion impacts. Coordinated groundwater management can be achieved if administrative criteria for acceptable levels of decline and depletion are developed, and used as a basis for permitting changes or new water uses.

Contribution of the GIS (Geographic Information System) in the Management of Foggara

Ansari Taha

The water resources in Adrar are important because that aquifer is part of the North Western Sahara Aquifer System shared between Algeria, Libya, and Tunisia. The static level is between 6 m to 30 m. That aquifer is exploited by boreholes, wells and the foggaras. Foggara is an ingenious and traditional technique of groundwater exploitation in an, arid area.

707 foggaras irrigate 11,353.04 hectares (28,042 acres) of palm groves, and perpetuates the greenery in the desert. We have inventoried 1829 foggaras through Adrar, Whose 707, perennials foggaras. Until today we have positioned 149,250 foggara wells, and 1690 combs by GPS. For each perennial foggara we measured the well depth and the water level every 250 m by a depth indicator tool, measured the foggara flow rates by a mini current meter, and we have sampled 680 samples to know the foggara’s water quality. The project’s goal is the establishment of the depth map of foggara wells. In the second time we established a piezometric map. The association of the depth map of foggara wells with the piézometric map allows us to extract the first information about the foggaras’ state.

In GIS we can extract the depth for all foggara wells from the depth map. We can also extract the water level for all the foggara wells from the piezometric map. In GIS you can visualize all kinds of foggaras: the perennials foggaras, foggaras dried, foggara dried and banked up, and foggara dried with stagnant water in an underground tunnel. We have established the foggara’s water quality map. The Algerian state continues to rehabilitate that traditional irrigation system and to put all the necessary means to safeguard it, because the foggara in Algeria continues to irrigate our palm groves, and perpetuates the greenery in the desert.

Improving Groundwater Management in the Peninsula of Yucatan Through Virtual Training

Luis E. Marin, Ph.D.

Water availability in Mexico has decreased from almost 18,000 m³/inhabitant per year in 1950 to almost 4000 m³/inhabitant per year in 2013 according to the Comisión Nacional del Agua (National Water Commission). Drinking water supplies for the Peninsula of Yucatan come from a sole-source aquifer which consists of a thin, fresh water lens. Water-related decisions originally were taken in the central offices in Mexico City of the National Water Commission. Recently, however, there has been a shift to manage water through 26 basin councils. The responsibility for water management in Yucatan falls under the auspices of the Peninsula of Yucatan Basin Council. One current weakness of this arrangement, however, is the lack of training of the members of the Peninsula of Yucatan Basin Council, both in hydrogeology and in the legal aspects.

A group of concerned citizens from academia, civil society, and the Mexican Federal Government have put together an online course to start teaching the “A-B-C´s” of water management and give an introduction into the Ley de Aguas Nacionales (National Water Law). The title of the course is “Water Management in Mexico” (Gestión del Agua en México). The course shows how the basin councils operate, what federal guidelines must be followed to comply with the National Water Law, and what are the legal requirements that all “water users” must follow.

The course is currently being offered as a graduate-level course at both Universidad Nacional Autónoma de México and Unidad de Ciencas del Agua of the Centro de Investigación Científica de Yucatán. To date, more than 35 persons are taking the course. This course will be followed with a second online course on Transparency, Accountability, and Integrity in the Water and Sanitation Sector in Mexico.

Groundwater Modeling

Jason R. House, C.G., P.G.

Analysis of Colloid Enhanced Contaminant Transport in Sets of Parallel Fractures with Fracture Skin

Vinish V. Nair, Ph.D.

Groundwater often contains significant populations of natural colloids as well as waste- and repository-derived colloids that may interact with pollutants and influence their transport. A triple continuum one-dimensional transport model is developed to analyze radioactive contaminant transport in the presence of colloids in fractured geological formations. The model accounts for contaminant transport in the fracture, reversible deposition onto fracture surfaces and onto the colloids, diffusion into the rock formation, and irreversible deposition of colloids onto the fracture surfaces. Sorption of the contaminant onto the fracture surfaces and onto suspended and deposited colloids are assumed to follow the linear equilibrium assumption (LEA), whereas the irreversible deposition of colloids onto the fracture skin surface is assumed to be governed by the linear kinetic sorption isotherms. The model also accounts for penetration of colloids into the rock formation. A fully implicit finite difference method-based formulation is employed for solving the numerical model. The impact of different colloid parameters on contaminant transport is investigated. Results clearly demonstrate that the distribution coefficient for contaminant sorption onto the suspended colloids is found to be the most significant colloid-related parameter influencing radioactive contaminant migration in fractured formation with fracture skin.

Hydraulic Conductivity and Permeability of Sediments in Irrigation Canals

Janka Ovcharovichova

The objective of this paper is to assess the hydraulic conductivity and associated permeability of the sediments in irrigation canals in Zitny Ostrov (Rye Island), Southern Slovakia, Europe. The irrigation canal network was built to provide for irrigation water in this region. The main source of water for irrigation canals is the Danube River, one of the largest streams in Europe. The water level in the irrigation canals and the groundwater level in the Danube River aquifer affect each other. The irrigation canals continuously experience silting process. Deposition of the sediments reaches 0.5 m to more than 1.0 m in thickness. Sediments permeability is one of the influential parameters in regards to infiltration and exfiltration of water into and out of the canals into the Danube River aquifer. As a result, the groundwater flow within the Danube River aquifer and the surface flow in the irrigation canals continuously interact. This study uses numerical methods to produce hydraulic conductivity and permeability estimates. Future study will focus on field experiments to assess the computed values.

Integrated Water Management Using Remote Monitoring for an Open-Pit Limestone Quarry

Joanna Moreno, PH

Engineered water management is crucial to development of a long-term strategy that emphasizes safety and efficiency. Key factors include characterizing groundwater flow direction and volume, characterizing interaction of surface water and groundwater, and operating constraints as the mine pit develops. Advances in remote monitoring allow for monitoring of flow rates and water levels, during planned or unplanned flow events, and permit robust analyses of the groundwater-surface water flow system around mines.

This paper presents the analysis of future pumping rates and volumes for an open pit mine located in an area of outcropping formations and faults. Pit lake levels are largely a function of groundwater inflow, pumping, and precipitation. Important factors relating to water management at this site include:

Historically, pit water levels were monitored periodically, but recently water levels and discharge flow rates have been remotely monitored, continuously.
A pit lake pump-off test was used as an areally extensive aquifer test to provide valuable data on the hydrogeologic properties of the groundwater system.
Pit lake water is discharged to a nearby creek and is hypothesized to be re-infiltrating and reporting back to the quarry.
Data from the transducers were communicated wirelessly to a database. This approach, though more costly than manual data collection, provided continuous water level and flow data even during unexpected events, without setting foot on the site.

The modeling analyses included calibration to pumping tests, implementation of pit progression, prediction of stream leakage for various outfall configurations, and analysis of seasonal and storm events on groundwater flow patterns and pit inflow rates. The results of this analysis were used to reduce pumping and related costs by approximately 30% and plan for future dewatering requirements under normal and extreme precipitation events.

Recent Enhancements to MT3DMS for Simulation of Solute Exchange in Hydraulically Connected Stream-Aquifer Systems

Eric Morway

MT3DMS is the most widely applied groundwater solute transport code used in concert with the U.S. Geological Survey’s groundwater flow model, MODFLOW. Due to the increasing number of packages available with MODFLOW, including those that simulate flow in the unsaturated-zone and in surface water networks (lakes, streams, and their corresponding groundwater/surface-water interaction), recent efforts have focused on expanding MT3DMS capabilities to include simulation of solute transport in the unsaturated-zone and surface water networks. The enhanced MT3DMS model is compared against analytical solutions as well as against results from other published codes, including the U.S. Geological Survey’s OTIS and VS2DT models. Results demonstrate the accuracy of the surface water and unsaturated zone transport solutions, as well as the ability to simulate stream-aquifer solute exchange. Because enhancements are applied to the familiar MT3DMS model framework, current users can expand upon existing MODFLOW and MT3DMS model applications by activating the appropriate packages in both codes (e.g., the Unsaturated-Zone Flow (UZF1) and Streamflow Routing (SFR2) packages). The enhanced version of MT3DMS is an effective tool for helping practitioners, researchers, and managers address increasingly complex solute transport concerns in settings that consider transport processes in the saturated and unsaturated zones, as well as in stream networks in hydraulic-connection to underlying aquifers.

Simulating the Predevelopment Groundwater-Surface Water Flow System in the San Joaquin Valley, California

Ben Bolger, BASc, MSc.

The San Joaquin Valley (SJV) in central California has significant water management concerns, given the high water demand for an increasing state population and for intense irrigation. The groundwater-surface water system in the area has undergone drastic changes since the employment of groundwater and surface water extractions for irrigation and mining, and is still responding to past and present stresses. The physically-based surface-subsurface numerical HydroGeoSphere model is used to examine the regional-scale hydrologic budget of the SJV at predevelopment conditions, constrained by available historical data. This study is distinguished from previous investigations by covering more of the SJV, incorporating a true predevelopment condition, and using a physically-based surface-subsurface hydrologic model. As a result, complex hydrologic processes, including groundwater-surface water interaction along the major rivers and within wetland areas formed by flooded surface water, as well as evapotranspiration (ET) and impacted root zone processes, were identified in the area. The presence and path of the major rivers in the domain are well defined in the model output. The general location and formation of the major wetlands simulated by the model, and the hydrologic processes that occurred within them, have a fair agreement with historical records. There is also a fair match between simulated and estimated water table elevations. ET is a significant sink of both surface water and groundwater. Successful simulation of the hydrologic processes and features, and the water balance of the natural system, underscores the importance of using an integrated model to analyze watershed-scale systems. This predevelopment hydrologic condition could serve as a reasonable initial state for future transient runs that bring the model up to current hydrologic conditions in order to estimate present and future water budgets.

The 3D Geological Modeling of the Milk River Transboundary Aquifer: Challenges and Solutions

Marie-Amélie Petre

The Milk River Aquifer spans southern Alberta (Canada) and northern Montana (USA) in a semi-arid region, considered water-short. Since 2009, the Milk River Aquifer is part of the inventory of the UNESCO ISARM-Americas initiative, which encourages riparian states to work cooperatively toward mutually beneficial and sustainable aquifer development.

In this context, the Geological Survey of Canada has launched MiRTAP (Milk River Transboundary Aquifer Project) in order to produce a unified hydrogeological model of the aquifer and make recommendations for the sustainable management of this shared resource. The Milk River Aquifer had already been studied during the 20th century; however, most of the previous studies were limited by the international border, preventing a sound and complete understanding of the aquifer dynamics.

A prerequisite for the hydrogeological model is the three-dimensional geological model of the aquifer. The building of the transboundary 3D geological model implies dealing with many diverse geological data, which do not have the same units or spatial reference. On a regional scale, many stratigraphies coexist; the geological formations are neither named nor recognized in the same way and may not include the same geological members on both sides of the border. Therefore, finding the equivalent geological and hydrogeological strata in the two countries could be challenging.

In the case of the Milk River Aquifer, a unified 3D geological model has been developed. It covers 50,000 km². The harmonization and unification of various sources of geological data was needed to build this uninterrupted 3D model, including the testing of a few new hypothesis not studied before. This model forms the basis of the future numerical hydrogeological model of the transboundary aquifer.

Groundwater Modeling (cont.)

Jason R. House, C.G., P.G.

Achieving Dramatic Improvements in Model Efficiency and Accuracy Using MODFLOW-USG: A Case Study

Wayne E. Hesch, B.Sc.

One of the main benefits of MODFLOW-USG is that it is capable of delivering shorter simulation run times than traditional structured versions of MODFLOW. In order to quantify these performance gains, we ran a benchmark test that compared the run time of MODFLOW-USG to the run time of an equivalent MODFLOW-2005 and FEFLOW model for a regional scale groundwater flow model. Our benchmark tests demonstrate that MODFLOW-USG is faster than MODFLOW-2005, reducing run times by 90% while delivering the same level of accuracy. The shorter run times are crucial for an iterative approach to model development, and also for Parameter Estimation runs. This paper will also discuss some of the challenges that must be overcome when creating unstructured grids for MODFLOW-USG.

Groundwater Model Sensitivity and Uncertainty Analyses: Methods, Results, and Recommendations

Mary C. Hill

Sensitivity and uncertainty analysis provide insights into and reveal consequences of the often complex set of processes needed to simulate groundwater and other environmental systems. Sensitivity analysis identifies observations important to parameters, parameters important to predictions, and observations important to predictions. Uncertainty analysis quantifies the precision with which predictions are calculated given the observations and other knowledge available for model development, including model construction. Model construction uncertainties can be evaluated using multiple alternative models that use alternative boundary conditions, numerical formulations, computer codes, and so on. Alternative models and more complicated models can be explored when sensitivity and uncertainty analyses are conducted using computationally frugal methods that require fewer model runs amenable to high performance computing. In this talk, recent investigations of computationally frugal methods are reviewed, including comparison with the computationally demanding Sobol and cross-validation methods. The new hybrid DELSA (Distributed Evaluation of Local Sensitivity Analysis) method is also discussed. Examples use groundwater and surface water models (MODFLOW, MODPATH-OBS, FUSE, and TOPKAPI). Results illustrate the insights that can be obtained from sensitivity and uncertainty analyses in general, and what is compromised and achieved using computationally frugal and demanding methods. Some examples include: (1) Differences between alternate groundwater models were more important than differences between local and Sobol measures of prediction uncertainty, suggesting that computational effort be focused on exploring alternative models. (2) A variance-based local method is used in a new way to display the information provided by observations for parameters from defined observation types. The local methods were found to be useful except for difficulties with FUSE models revealed using DELSA. Recommended methods and diagnostics for choosing between methods are discussed.

Numerical Model for Mexico Valley Aquifer

Adriana Palma Nava

A numerical model for the Mexico Valley Aquifer is presented which is intended to be a tool in planning the curtailment of excessive pumping from the aquifer that has caused serious and expensive damage to city infrastructure as a result of associated land subsidence. This is within a larger planning effort to provide potable water from other sources, mainly avoiding losses from the water supply network and incorporating water today used in irrigation.

The model integrates the differential equation of water motion using a finite volume mesh in space and an implicit finite difference scheme in time. The main aquifer is connected to a phreatic aquifer through a clay layer (aquitard); the interaction between layers is computed with the integration of the vertical flow differential equation in the aquitard. The model accounts for the hysteresis effect of pressure recovery. Model boundary conditions are only of Neumann type representing the aquifer recharge at the surrounding impermeable mountain piedmonts or at volcanic permeable formations. Interaction with the surface permits the determination of spring discharges.

The simulation spans a period of 150 years starting in year 1900. A large effort was made to collect historical information about pumped water volumes, spring discharges, piezometric heads and land subsidence; also about detailed characteristics of underlying geologic formations and hydrogeology. Calibration is made comparing measured against simulated evolutions of piezometric levels, land subsidence and spring discharges.

Results indicate that pumping curtailment raises water levels substantially and immediately, but that land subsidence exhibits inertia and takes a long time before terminating. Demand management, while politically difficult, is a necessary measure to avoid further costly damage to city infrastructure and buildings.

Parameter Uncertainty for Capture Zone Delineation in a Complex Hydrogeologic Environment

Martinus Brouwers, MASc

Groundwater flow models are useful tools for the management of groundwater resources. While a vast amount of data can be collected and implemented in the development of a numeric model, it remains only an approximation of the real-world system. As such, data gaps and uncertainties exist in the parameterization of a model. These uncertainties carry forward when using the model to make predictions such as capture zones.

Capture zones are typically delineated by applying backward (advective) particle tracking to a calibrated model and projecting the encompassed footprint to ground surface. It is recognized that considerable uncertainty exists in the size and shape of these capture zones. To compensate, professional judgment is typically applied to provide a degree of conservatism. This is done to account for features that cannot be explicitly represented in a numeric model such as the degree of heterogeneity and variability of the natural system.

In an effort to address this uncertainty, a backward-in-time advective-dispersive transport approach has been applied as an alternative approach to delineating capture zones. This technique has the advantage of representing local scale heterogeneity through the inclusion of the dispersion term. The resulting capture zones can be delineated within the context of a probabilistic framework.

This paper presents an alternative approach to developing capture zones that encapsulates the uncertainty of the hydraulic conductivity distribution. One hundred statistically equivalent models are generated by randomly sampling log-normal hydraulic conductivity distributions that are centered about model calibrated values. Each model explicitly simulates different flow paths, thereby sampling the variability of the flow system. A composite capture zone is created by combining all these capture zones. The composite capture zone can be likened to a spatial probability distribution of groundwater contribution to a given well. A comparison of the capture zones created using these two approaches is presented.

Wellhead Protection Area Delineation Methods and the Influence of Heterogeneity, Anisotropy, and Aquifer Surface Recharge

Djaouida Chenaf

The decisive parameter for a wellhead protection area (WHPA) is attributed to a time of travel value. The available analytical methods that define the time of travel are based on simplistic assumptions of reality. These methods assume a one layer aquifer to be homogeneous and isotropic and the layered aquifer to be equivalent to a homogeneous and anisotropic one layer aquifer. In the absence of surface recharge for an aquifer, Chenaf, Boukemidja, and Kettab (Chenaf et al. 2013) have shown that it is important to consider the anisotropy and heterogeneity of the aquifer as naturally encountered. They have shown, in particular, that the calculated times of travel for the equivalent models dangerously underestimate the WHPA. In this article, the influence of the heterogeneity and the horizontal and the vertical anisotropies on the time of travel in an aquifer is examined when a surface recharge exists. It is found that the time of travel and therefore the WHPA are affected by the surface recharge beyond a certain distance from the pumping well, in all aquifer configurations.

Groundwater Remediation

Edward Gilbert, CPG

Fracture-Emplacement and 3D Mapping of a Micro-Iron/Carbon Amendment in TCE-Impacted Sedimentary Bedrock

Kent Sorenson, Ph.D., PE

An in situ pilot remediation project was carried out on behalf of the U.S. Army Corps of Engineers at the Former Atlas “E” Missile Site No. 12 in Colorado that featured an innovative application of drilling, treatment, fracture-emplacement, and geophysical technologies to mitigate impacts from chlorinated volatile organic hydrocarbons.

The former missile site complex is underlain by silty sandstone bedrock sediments impacted by trichloroethene (TCE) exceeding 3000 μg/L and associated volatile organic hydrocarbons. The purpose of the pilot test was to evaluate the performance of technologies prior to developing the proposed remedy. Two pilot test areas (source area and dissolved plume area) were selected to evaluate the effectiveness of biotic and abiotic in situ chemical reduction for reducing trichloroethene concentrations to less than maximum contaminant levels.

The pilot work involved the emplacement of over 100 tons of a micro-iron/complex carbon treatment amendment into deep bedrock sediments to attain optimal distribution throughout the contaminant plume, including underneath the former Launch and Service Building. Hydraulic fracturing was conducted in pre-drilled boreholes to deliver the amendment slurry between depths of 35 ft. to 63 ft. in bedrock. Tiltmeter geophysics was used to verify the final distribution and geometric configuration of the micro-iron fractures placed. Initial groundwater quality results after the first round of sampling conducted 90 days after EHC placement indicated a reduction in VOCs of 50% to 90% compared to pre-treatment concentrations.

The implications of this demonstrated ability to distribute and map massive quantities of micro-iron amendment in challenging bedrock formations include: a drastic reduction in the amount of injection wells required to treat large plume areas, vastly improved remedial performance monitoring, and significant cost savings compared to conventional remedial approaches.

Groundwater Remediation Using a Chlorine/Ultraviolet Advanced Oxidation Process

Andrew Boal

Advanced Oxidation Processes (AOPs) use a variety of means to generate hydroxyl radicals, potent oxidants which can rapidly degrade a large variety of organic chemicals. AOPs are commonly used in groundwater remediation applications to remove chemicals such as 1,4-dioxane, methyl-tert-butyl ether (MTBE), or trichloroethylene (TCE) from a contaminated water source. Combining hydrogen peroxide and ultraviolet light (H₂O₂/UV) is the most commonly used AOP, and this process works through the action of UV light on hydrogen peroxide, which produces hydroxyl radicals. While H₂O₂/UV AOPs are effective, they are often costly due to the high price of hydrogen peroxide, the low amounts of hydrogen peroxide actually used in the process, and the need for quenching residual hydrogen peroxide after AOP treatment is complete. Recently, researchers have been exploring the combination of aqueous chlorine and ultraviolet light (Cl₂/UV) as an alternative AOP. Similar to H₂O₂/UV, Cl₂/UV produces hydroxyl radicals from the photolysis of aqueous chlorine. Laboratory testing had indicated that, in some situations, Cl₂/UV AOPs are expected to be far less expensive than a comparable H₂O₂/UV process. Until now, such observations had not been corroborated through field studies, where parameters outside the control of a laboratory setting can impact AOP treatment outcome.

This presentation will describe pilot study results comparing H₂O₂/UV and Cl₂/UV AOPs for the removal of TCE from contaminated groundwater. These studies were conducted on the full scale operations of two Ground Water Extraction and Treatment facilities operated by Aerojet-Rocketdyne, and compared the TCE removal efficacy of the in-place H₂O₂/UV AOP with Cl₂/UV AOP. Data was then used to determine the expected operational costs of a full scale Cl₂/UV AOP treatment process. The impact of Cl₂/UV AOP on the photolytic removal of N-nitroso-dimethylamine (NDMA) and the acute toxicity of the AOP effluent water were also explored.

Limitations of Vacuum-Enhanced Extraction: Residual LNAPL in Sandy Soils as a Long-Term Source of Contamination

Jacob Hartsock

Vacuum-enhanced extraction (VEE) of LNAPL is commonly implemented to prevent LNAPL migration, remove free-phase product, and reduce dissolved-phase constituents from groundwater. However, subsurface heterogeneities, proximity to groundwater recharge boundaries, and incorrect assumptions often reduce the effectiveness of VEE. Additionally, fluctuating water table conditions, which are exacerbated by VEE, create large “smear zones” of residual LNAPL. Residual LNAPL within these smear zones is relatively immobile and difficult to remove, providing a long-term source of dissolved phase constituents. Residual LNAPL is also capable of sufficient remobilization to induce additional migration, which could lead to persistent seeps and sheens if the site is adjacent to a surface-water receptor. Developing accurate conceptual site models to address LNAPL source zones and migration pathways is essential in implementing effective remedial technologies. However, analytical and numerical models used to calculate LNAPL saturation and recoverability are often based on outdated theories or parameter assumptions that are capable of outputs that produce order-of-magnitude variability. In practice, these methods have been known to exaggerate recoverable LNAPL, overestimate VEE capabilities, and set unrealistic remediation timeframes.

A case study will be presented to illustrate common pitfalls of VEE in shallow unconfined sandy aquifers contaminated with diesel fuel and gasoline and located adjacent to engineered waterways. The site has been undergoing VEE for over 15 years, with over one billion gallons of impacted groundwater treated. Less than 60,000 gallons of free-phase LNAPL have been recovered, and daily recovery rates are currently approaching less than one gallon. Benzene concentrations in monitoring wells frequently exceed regulatory limits, and surface-water discharges range from a light sheen to visible product. Contemporary LNAPL theories are used to develop an updated conceptual site model and a more refined evaluation of the effectiveness of VEE in sandy soil conditions.

Rising and Falling Contaminant Concentrations After Flooding at the Riverton, Wyoming Uranium Mill Tailings Site

William Dam

A uranium mill operated from 1958 to 1963 in Riverton, Wyoming. An unlined tailings disposal pond and pile covered about half of the 140-acre site, resulting in groundwater contamination. In 1988 and 1989, the tailings were relocated to a disposal site 45 miles away.

The Riverton mill site is located on an alluvial terrace between the upgradient Wind River and the downgradient Little Wind River and both rivers periodically flood. In June 2010, melting snowpack and rainfall resulted in the mean monthly discharge of the Little Wind River equaling 5829 cubic feet per second which was more than 2.5 times higher than the mean discharge for the same month measured since 1941 and caused the highest recorded flood, 4 feet above the National Weather Service flood stage.

The groundwater plume has migrated about one mile downgradient with the highest solute concentrations found near the Little Wind River based on over 20 years of monitoring. After the 2010 flood, dramatic increases in contaminant concentrations including molybdenum and uranium were observed in four groundwater monitoring wells. For example, uranium increased at one well measured two weeks after the peak flooding from about 0.8 mg/L to 2.7 mg/L. The EPA maximum concentration limit in groundwater for uranium is 0.044 mg/L. Subsequently, molybdenum and uranium concentrations have returned to pre-flood levels.

As a result of changing groundwater concentrations from flood events, an enhanced characterization program is evaluating additional sources of contaminants in the unsaturated and saturated zone soils and sediments and re-examining hydrologic and geochemical mechanisms controlling contaminant transport. Field, laboratory, and numerical modeling results indicate that the natural attenuation compliance strategy may not be achievable as previously thought. To protect public health, DOE works with local groups to restrict access and provides a potable water supply.

Utilizing High Resolution Site Characterization to Maximize Remediation Value in Groundwater and Soil Remediation

Eliot Cooper

Historically, high resolution site characterization (HRSC) techniques including ultraviolet optical screening tool (UVOST), membrane interface probe (MIP), and electrical conductivity (EC) have been utilized as a troubleshooting technique following months or years of diminishing returns and/or non-performance during in-situ remediation including injections and mechanical system use.

Following a release from an underground storage tank at a site in North Carolina, typical investigative methodologies including direct push sampling, temporary and permanent monitoring well installation, and sampling were utilized to characterize the release and subsequent downgradient migration of BTEX and TPH. Based on limited investigation data including wells which were screened across a large interval, a caustic persulfate injection was designed to oxidize dissolved phase BTEX and TPH in groundwater. Total proposed costs including field work and persulfate topped $100,000.

Based on review of these data, HRSC field activities were suggested to better define contaminant distribution in both the vertical and lateral directions, and to obtain site-specific geochemical data. A limited HRSC program was completed in approximately four field days which included MIP, injection testing including EC evaluation of persulfate distribution, and site-specific analysis of soil oxidant demand.

Following completion of HRSC, total injection volumes in the revised design decreased by more than 40% because of a more refined understanding of contaminant distribution in the subsurface.

This platform presentation will demonstrate the effective use of HRSC techniques from the beginning of investigative activities and provide metrics for total dollars proposed to be spent prior to HRSC and actual dollars spent following a more complete understanding of contaminant mass, distribution, and injection parameters. Total remediation costs can be demonstrated to have been reduced by 35% over the lifespan from release to near closure.

Groundwater Remediation (cont.)

Edward Gilbert, CPG

Dual Domain Transport Impacts on Projected Groundwater Remediation

Robert H. Fitzgerald, P.E.

Contaminant plume “tailing” is a commonly used description of a groundwater cleanup that proceeds slower than expected, based on routine contaminant transport analysis. One cause of tailing is slow diffusion of dissolved contamination from lower permeability portions of an aquifer into higher permeability zones that may continue for a long time after remediation of the source. Diffusive exchange of contaminant mass may occur between a relatively low permeability rock matrix and high permeability fractures in a bedrock aquifer or between silt or clay lenses and adjacent high permeability sandy fractions within a heterogeneous overburden aquifer.

Using a dual domain transport algorithm developed in DYNSYSTEM, mass transport simulations were conducted for an industrial remediation site to evaluate the potential impacts of dual domain transport on the duration of groundwater remediation and to inform remediation operation cost projections.

Test simulations of historical plume development were used to estimate an appropriate range of dual domain parameter values for future projection simulations. Projection simulation results indicated that factoring in matrix diffusion has the potential to more than double the estimated time required to achieve the remedial objective and system shutdown compared with the original estimate based on conventional transport modeling.

Field Demonstration of a Monitoring Toolbox for In Situ Biogeochemical Transformation

Patrick Evans

In situ biogeochemical transformation involves biological formation of reactive minerals that can destroy chlorinated solvents without accumulation of intermediates like vinyl chloride. An AFCEC-funded field demonstration was conducted to develop a monitoring toolbox to assess biogeochemical transformation at two existing mulch biowalls at Altus AFB to treat VOC-contaminated groundwater. Three segments of the Altus OU1 biowall were monitored—(1) segment recently rejuvenated with electron donor and iron, (2) segment recently rejuvenated with electron donor only, and (3) segment with no rejuvenation. In addition, a segment of the Altus SS-17 biowall (no rejuvenation) was monitored.

Monitoring data were collected quarterly for 18 months for groundwater velocity, electron acceptor loading rates (i.e., mass per day per unit volume of treatment zone), electron donor concentrations, geochemical conditions, reactive minerals, microbiological activity, and VOCs.

The SS17 biowall showed a biogeochemical transformation pattern based on a high VOC destruction without accumulation of daughter products. Factors that appeared to promote VOC removal included: (1) high volumetric sulfate consumption rates, (2) high concentrations of total iron in the biowall matrix, (3) low dissolved sulfide concentrations, and (4) relatively high oxidation-reduction potentials. These results contrast to the low total molar VOC destruction observed in the unamended OU1 biowall section, which had (1) low volumetric sulfate consumption rates, (2) low total iron concentrations, (3) high dissolved sulfide concentrations, and (4) more negative ORP.

For the organic-amended and organic-iron amended OU1 biowall segments, sulfide concentrations decreased and total molar VOC destruction increased following rejuvenation. These data suggest that amendment with organics and not iron was primarily responsible for biowall rejuvenation.
Monitoring tools that provided useful data during this demonstration were VOC removal, dissolved sulfide concentration, oxidation-reduction potential, volumetric sulfate consumption rate measured using passive flux meters, total biowall iron concentrations, total volatile fatty acids, pH, and electron microprobe analysis.

Solubility Enhanced in Situ Chemical Oxidation of VOC Contaminated Soil and Groundwater: Pilot Field Test

Dylan E.H. Eberle

In situ chemical oxidation (ISCO) is an increasingly accepted treatment technology for groundwater and sediments contaminated with hydrophobic volatile organic compounds (VOC). ISCO reactions occur predominantly in the aqueous phase and as a result ISCO is more effective at treating dissolved phase contaminants than sorbed compounds or dense non-aqueous phase liquids (DNAPLs). We hypothesize that it may be possible to increase the efficiency of ISCO by using a solubility enhancing agent which increases the mass of aqueous phase VOC that is available for oxidation. In this pilot scale field test we studied the solubility enhancing agent hydroxypropyl-beta-cyclodextrin (HPCD) in combination with an advanced oxidation process at a former fire training area. The oxidant used in this study is a perxone (O₃ + H₂O₂) activated sodium persulfate (Na₂S₂O₈) mix known as OxyZone®. Major pollutants at the site include VOC such as 1,1,1-trichloroethane (1,1,1-TCA), dichlorobenzenes (tDCB), and tetrachloroethene (PCE). Other contaminants include the solvent stabilizer 1,4-dioxane and perfluorinated compounds (PFC), which were widely used as flame retardants. The most abundant PFC detected at the test site is perfluorooctanesulfonic acid. Preliminary results suggest that HPCD facilitated the transfer of VOC to the aqueous phase and their subsequent destruction by ISCO. The results of the solubility enhanced treatment of VOC, as well as 1,4-dioaxne and PFC co-contaminants, will be presented.

Groundwater Remediation (cont.)

Joseph Quinnan, PE, PG

Drilling an Array of Columns to 95 Feet to Install Deep ZVI Permeable Reactive Barrier

Sarah Conkle

The Wyoming Air National Guard Base is part of the Cheyenne Municipal Airport, approximately 2 miles north of downtown Cheyenne, Wyoming. As a result of historic solvent use for aircraft maintenance operations, a groundwater plume with carbon tetrachloride (CCl₄) and trichloroethylene (TCE), two orders of magnitude above remedial goals, extends 1200 feet offsite. CH2M HILL installed a 95-foot deep zero valent iron (ZVI) permeable reactive barrier (PRB) to intercept the groundwater at the base boundary and accelerate the attenuation of the off-base plume.

A Continuous Flight Uncased Hollow Stem Auger method was used to install the ZVI PRB, which is made up of 192 three-foot-diameter columns, placed in two offset rows perpendicular to groundwater flow. The columns were installed on five-foot centers (two feet between columns) to create a PRB with an aggregate length of 480 feet. Based on groundwater modeling, this configuration would provide the same residence time and treatment effectiveness as a conventionally installed three-foot-wide trench.

Because of site and plume characteristics, each column included three vertical layers to address the horizons of interest: Layer 1 (40-65 feet bgs) included up to 100 percent iron and the reciprocal volume of sand; Layer 2 (52-84 feet bgs) included a low permeability grout to limit downward vertical groundwater migration through the columns; and Layer 3 (72-95 feet bgs) included 15 percent ZVI and 85 percent sand. The amount of ZVI was based on the groundwater velocity and column study results.

The presentation will review the critical design elements for the drilled column ZVI PRB and key challenges associated with its construction. Groundwater data from the first year of monitoring will also be presented.

First Year Progress Report: In Situ CO2 Sparging into a Caustic Brine Plume

Robert D. Mutch Jr., P.Hg., P.E.

In situ sparging of gaseous CO₂ is being conducted on a nine-acre, caustic brine plume in southeastern Georgia to neutralize the plume and to reduce levels of mercury and other heavy metals. The plume exhibits high pH levels ranging from 10.5 to 12, densities as high as 1.08 g/mL, high dissolved silica concentrations, and mercury ranging from 50 to 1000 μg/L. The plume lies at the base of the moderate to low permeability Satilla Aquifer in the Georgia coastal plain at depths ranging from 30 to 50 feet below ground surface.

Planned as a three year implementation, this paper presents the findings of the preliminary laboratory testing, a major pilot-scale test, and the results of the first year of implementation of the full-scale system. The pilot test involved a single sparge well and 13 monitoring wells at varying depths and radial distances up to 100 feet. Monitoring wells were equipped with Hach field electrodes to monitor pH continuously and in real time and Solinst automatic data loggers to monitor water level mounding and collapse during intermittent sparging operations. The pilot test demonstrated that pH within a radial distance of up to 60 feet table and encompassing a total aquifer volume of approximately 6500 cubic feet could be reduced to near neutral pH. Mercury levels declined by 80% to 90% and significant declines in silica, arsenic, and chromium were also observed. The first year of operations involves CO₂ sparging into 64 sparge wells and pH monitoring in more than 30 observation wells. Pressure transducers will also be deployed to monitor transient mounding caused by the sparging activities.

Modeling of Groundwater Contamination by Light Nonaqueous Phase Liquids (LNAPLs)

Wonyong (Alan) Jang

The groundwater contamination by dissolved components of light nonaqueous phase liquids (LNAPLs) was detected in the Hadnot Point Industrial Area at U.S. Marine Corps Base Camp Lejeune in North Carolina. Field investigation found lens of free-phase LNAPLs on the top of groundwater. The thickness of the free phases highly varied in the study area. The dissolution and migration of their components polluted the groundwater, which was drawn for public supply. Using numerical tools, including TechFlowMP and TechNAPLVol, we investigated the distribution of free-phase LNAPLs, their dissolution, and groundwater contamination in the area. This paper will present the transport of dissolved LNAPL component and vertical variation of contaminant migration under influence of pumping in the study area. In addition, it will show the temporal profiles of contaminant concentrations in pumping wells near the LNAPL sources.

Perfluorochemicals: How Groundwater-Surface Water Interactions Helped Create a Megaplume

Virginia Yingling

Perfluorochemicals (PFCs) are a class of persistent and highly mobile compounds used in a wide range of industrial and consumer products. They have been detected globally in environmental media, humans, and wildlife and research suggests possible human health effects may result from exposures at environmental levels. Migration of PFCs from three legacy disposal sites in Washington County, Minnesota have contaminated over 100 square miles of groundwater; an area much greater than predicted by early modeling based on regional groundwater flow regimes. Investigations revealed that a “perfect storm” of complex groundwater-surface water interactions, regional- and local-scale bedrock features, and the extreme environmental persistence of PFCs combined to create a co-mingled “megaplume” that contaminated over 1,500 private wells and 8 community water supplies. This talk will focus on the role of groundwater-surface water interactions and bedrock features in the creation of this “megaplume”, but will also touch on the fate and transport of PFCs, their possible health concerns, and clean-up options.

Removal of Arsenic and Mercury with Permeable Reactive Barrier Consisting of Iron Oxide Particles

Xin Song

Groundwater contamination by heavy metals such as arsenic (As) and mercury (Hg) is of a significant concern because the toxicity exhibited by these heavy metals can pose a severe threat to human health and the environment. In recent years, passive treatment technologies such as permeable reactive barriers (PRBs) have increased rapidly due to lower long-term operation and maintenance costs compared with the traditional active treatment technologies such as pump and treat.

Zero-valent iron (ZVI) has been one of the most widely used barrier materials in PRBs due to its effectiveness in removing a wide range of contaminants. However, barriers consisting of ZVI often experience reduction in porosity, chemical reactivity, and hydraulic conductivity over time due to corrosion and mineral precipitation. This study presents the evaluation of alternatives to ZVI (such as Fe₃O₄ and Fe₂O₃) that can be used in the PRBs. The specific objective of the study is to improve the fundamental understanding of the performance of individual corrosion products for As and Hg removal. Batch experiments have been carried out and it was found that the removal efficiency of Fe₂O₃ was influenced by the presence Cl^- and SO₄^2-; however, 100% removal of As and Hg were achieved with both ZVI and Fe₃O₄, with no detectable influence of both anions. Iron oxide particles are being developed electrochemically as a barrier material for PRBs to allow for simultaneous As and Hg removal. The removal efficiency will be evaluated in column experiments and field-scale applications. In addition, the effects of several parameters, including the initial concentrations of As and Hg, the presence of cations and anions, pH, and dissolved oxygen, on the performance of iron oxide particles will be examined.

Groundwater Remediation (cont.)

Andrew Manning, Ph.D.

High Recharge at Semi-Arid Site Explains Wide-Spread Perchlorate in Groundwater with a Deep Water Table

Daniel B. Stephens, Ph.D., PG

Perchlorate, a highly water soluble compound, was detected in groundwater near Rialto, California beneath much of a 160-acre area where the depth to groundwater is about 250 to 400 feet below ground surface. Mean annual precipitation is about 20 inches. The soils are permeable alluvial gravels with sparse vegetation. Assumptions that diffuse recharge is about 0.5 to 5 percent of mean annual precipitation, an assumption used in regional groundwater studies, cannot explain the depth of perchlorate migration through the vadose zone. Model studies and field data show that even under non-ponded conditions, perchlorate can migrate to much greater depths than otherwise expected. This behavior is attributable to localized focused recharge, the permeability of the alluvium, and the absence of vegetation during site operations. The high local recharge, 20 to more than 50 percent of mean annual precipitation in places, also explains why shallow soil sampling did not detect significant concentrations of perchlorate in some areas.

Introduction of Per- and Polyfluorinated Substances into Groundwater Samples Using Industry-Standard Sampling Equipment

Doug Winter

Per- and polyfluoroalkyl substances (PFAS) have emerged in the environmental arena as unexpected groundwater contaminants, potentially present at many existing sites worldwide. Because of increased regulatory awareness, groundwater sampling will be increasingly performed in the future to assess the nature and extent of groundwater impacts from these emerging contaminants. Unfortunately, the chemical characteristics that made PFAS such excellent products for consumer and industrial use, including low coefficient of friction, hydrophobicity, and lack of sorption to organic materials, make them ideal products for construction and coatings for environmental sampling equipment. Many impeller pumps and bladder pumps contain or are coated with fluoropolymers and fluorotelomers, such as Teflon and Viton. Internal parts include O-rings, seals, impellers, bladders, thrust washers, wear plates, and wire jackets and sample tubing is often coated as well. Many of these parts contact the groundwater sample during collection and have the potential to introduce low-level contamination that may be incorrectly attributed to the facility or aquifer. With regulatory standards in the sub-part per billion range, such as New Jersey’s 0.04 µg/L drinking water regulatory criteria, introduction of low levels of PFAS into a sample could lead to unnecessary regulatory alarm and possible remedial actions.

Equipment blanks were created using the most common sampling equipment by exposing the equipment to Type II Reagent Grade distilled water, collecting the water in Teflon-free sample bottles, and analyzing the samples for a defined list of PFAS at Oregon State University’s analytical laboratory. Detailed analytical data will be presented for the six PFAS that are on the US EPA’s Unregulated Condiment Monitoring Rule 3 (UCMR3) and recommendations will be provided to ensure that samples collected are representative of the subsurface groundwater conditions and not the sampling equipment utilized.

Nuclear Magnetic Resonance—A New Tool for Enhanced Environmental Investigations

Matt S. Spurlin, PG

Nuclear magnetic resonance (NMR) logging tools have been widely used in the oil industry since the 1960s and have improved in the last two decades. NMR provides estimates of bulk porosity and fluid content, quantification of bound versus mobile fluids, and semi-quantitative estimates of hydraulic conductivity. Although the size and cost of oil-field tools historically limited their use for environmental applications, smaller and more economical NMR logging tools are now available for detecting and characterizing the formation water content and hydraulic conductivity as part of environmental investigations. It can be used in direct-push mode or can be lowered into existing PVC wells. Using the tool in existing wells is a safe alternative compared to drilling new boreholes. In either mode, NMR can provide useful hydrostratigraphic information if historical drilling logs are unavailable or limited in geologic detail, and can help refine the overall conceptual site model.

NMR investigations at two sites in Texas and one site in New Mexico demonstrate the viability of this technology as a site characterization tool for environmental investigations. NMR measurements were compared to data from lithologic logs and prior field hydraulic tests. Use of NMR detected vadose zone water, including previously unidentified perched groundwater zones, and provided hydrostratigraphic details that could not be gleaned from historical well drilling logs. NMR also produced hydraulic conductivity estimates similar to those from conventional hydraulic tests, but the improved vertical resolution from NMR provided additional information regarding the vertical heterogeneity of the formation along the entire length of the well or borehole.

Remedial Performance Evaluation of Dual PRBs Installed in a Historical Arroyo

Aaron D. Kempf

Passive treatment technologies for groundwater remediation are an attractive choice for sites where future use and minimizing operation and maintenance are a priority. Permeable reactive barriers (PRBs) can provide effective groundwater treatment while minimizing site disturbance and long-term interruptions. However, careful design and implementation is required to ensure performance that achieves remedial objectives.

Historical lead and copper smelting operations conducted over 100+ years have resulted in site groundwater primarily impacted with arsenic. Groundwater flow and the majority of arsenic mass flux are concentrated in buried arroyos at the site, which present an opportunity to provide a focused groundwater remedy as part of a larger site restoration strategy. In the largest arroyo, two zero-valent iron (ZVI) PRBs were constructed in series to passively treat site groundwater and reduce the mass flux to sensitive receptors. Pre-design activities included column testing to determine the site-specific ZVI groundwater arsenic uptake characteristics, as well as detailed hydrogeologic and contaminant characterizations.

Site arroyos consist of coarse alluvial deposits resulting in a high-permeability and high flux groundwater flow system, which required PRB designs including both high permeability and widths and iron content consistent with contaminant loading rates and desired treatment longevity. PRBs were constructed of a ZVI and sand backfill with a hydraulic conductivity of greater than 1000 ft/day, and were approximately 8 feet thick to provide sufficient residence time and meet the targeted design lifetime.

Monitoring data including high-resolution water levels, hydraulic conductivity estimates, tracer testing, and water quality analyses are presented and compared to the PRB design parameters and performance objectives, which included effective hydraulic groundwater interception, contaminant removal efficacy, and continued reactivity of the ZVI and positive geochemical indicators. Results indicate that the PRBs are intercepting groundwater and resulting in reductions in arsenic groundwater concentrations.

Groundwater and Energy

William L. Cunningham

Data Management for the New and Expected Petroleum Baseline Sampling Rules

David W. Rich, Ph.D.

In February 2013, the Colorado Oil and Gas Conservation Commission (COGCC) published Rules 609 and 318A. The rules made Colorado the first state in the country to require pre- and post-drilling sampling of water sources near new oil and gas wells permitted after May 1, 2013. A number of oil and gas operators predict that requirements similar to these will be implemented by other states in the near future.

This talk will discuss the new Colorado rules and the data management requirements for the sampling. For example, all laboratory results must be uploaded to the COGCC website in one of their specified formats, to be made available to the public. Integrating these requirements into a comprehensive data management process lets project staff perform in-house quality control, reporting, and mapping, and then upload the data to COGCC, properly handling data details like Facility IDs and Sample IDs generated by the state, and allowing easy comparison of pre- and post-drilling samples. As with any other petroleum-related data, the process needs to take into consideration issues like QC samples, reanalyses, and non-detected results, comparison to regulatory limits, and so on, but effective automation of the process can streamline project work and minimize errors.

Groundwater Quality In the Vicinity of Oil and Gas Development in the Denver-Julesburg Basin

Joseph Ryan

We reviewed water quality data made available by the Colorado Oil and Gas Conservation Commission for water wells in the Denver-Julesburg Basin in northeastern Colorado as a function of proximity to oil and gas wells. The likelihood of elevated concentrations of methane and certain inorganic constituents increased with proximity to oil and gas wells. Based on carbon-13 isotope abundance in the methane, the methane in water wells was mostly biogenic, not thermogenic. Based on the available data, the occurrence of water well contamination associated with oil and gas development is infrequent.

Pre-Drill or Baseline Water Quality Testing for Oil and Gas Operations

Robert Puls, Ph.D.

Several states and other groups have recently put forward guidelines for sampling private water wells where oil and gas operations are occurring as public service information (e.g., Penn State Agricultural Extension; Oklahoma State Agricultural Extension; NGWA/GWPC; Louisiana Department of Health and Hospitals). Several states have recently promulgated regulations that address pre-drill sampling of drinking water supplies/wells (CO, OH, ND, PA, WV, WY, IL). While these are steps in the right direction, there continues to be variation in what is covered under these rules and guides as well as gaps. While leading the field technical portion of the USEPA Hydraulic Fracturing Study in 2010 and 2011, the single most glaring deficiency in all state programs for oil and gas operations was the absence of any rules or guides for baseline water sampling. When complaints were lodged with state agencies, there was almost never any pre-drill data to compare to post-drill suspected impacts. The best available data was typically historical regional water quality collected by the USGS, some of which could be decades old. Because of the natural variability of subsurface systems, this data was usually insufficient to allow for comparisons between pre- and post-drill water quality data. This presentation will provide an overview of state rules on this topic and emphasize the importance of proper sampling methods.

Stream Methane Monitoring for Evaluating Groundwater Impacts Associated with Shale Gas Development

Victor Heilweil

The baseflow of gaining streams can provide an integrated chemical signal for groundwater systems. It may be possible to evaluate impacts from unconventional gas development by sampling such streams. The stream-reach methane (CH₄) mass balance method is one approach for establishing baseline groundwater quality prior to development and detecting subsequent contamination. This method has the advantage of using gaining streams to monitor groundwater quality at the watershed scale, rather than the point scale provided by monitoring wells. A tracer injection in Nine-Mile Creek, Utah, showed the downstream persistence of CH₄ for over 1.5 km downstream, with an “apparent” (atmospheric loss plus any microbial degradation) gas transfer velocity of 4.5 m/d. In West Bear Creek, North Carolina, injected CH₄persisted for more than 2.5 km downstream. A noble gas (krypton) was also injected in order to separate atmospheric CH₄loss from any microbial degradation. Comparison of the gas transfer velocities determined from CH₄ and Kr will indicate whether microbial degradation is a significant process (work is in progress). These methods are now being tested in pilot-scale studies in the Marcellus shale-gas play of Pennsylvania. Preliminary reconnaissance sampling has yielded stream methane concentrations of up to 70 ppb (background is generally < 2 ppb). Follow-up work along Sugar Run using an uncalibrated mass balance with transport modeling suggests that inflowing groundwater may have CH₄concentrations of up to 3000 ppb; sampling along Tunkhannock Creek showed ¹³C-CH₄ enrichment (from -55 to -39 permil), indicating a possible thermogenic source. These results illustrate the utility of the method for locating areas of anomalously high stream CH₄, but more detailed assessment is needed. Future work in both streams includes additional ¹³C-CH₄and noble gas fingerprinting to evaluate methane sources (biogenic or thermogenic) and tracer injections for quantifying groundwater inflow and gas transfer velocities.

Groundwater and Energy (cont.)

William L. Cunningham

Investigating Groundwater Chemistry in the Coal Seam Gas Fields of the Surat Basin, Queensland, Australia

Lucy Reading

Large volumes of water must be pumped from coal seams in the Surat and Bowen basins in Queensland, Australia, in order to produce coal seam gas (CSG). Therefore, significant depletion of adjacent aquifers might be expected to occur. Management of the impacts of coal seam gas activities on groundwater therefore focuses on impacts on water levels. However, there is potential for groundwater quality impacts to occur in response to altered hydraulic gradients causing mixing between adjacent aquifers. While there have been previous studies of these processes in other countries such as the United States, there has been very limited research in this area in Australia.

A research project has been initiated at The University of Queensland to analyze groundwater chemistry data from coal seam gas fields across the Surat Basin. The data that has been used for this project has been obtained from the Queensland government and from CSG companies. Evaluation and interpretation of geochemical data is currently carried out in conjunction with stratigraphic interpretations. Preliminary results of these geochemical interpretations indicate that inclusion of trace elements in the analyses of basin-wide trends may improve our understanding of potential impacts of CSG activities on groundwater chemistry.

Natural Hydraulic Fracturing, Fluid Pressure, and Saltwater Disposal in the Arbuckle: Implications for Induced Seismicity

Kyle Murray, PhD

Although petroleum has been produced in the midcontinent for more than a century, water management by the industry has only recently been in the foreground. After separating water from oil and gas at the wellhead, producers are left with co-produced brine that is typically disposed of via saltwater disposal (SWD) wells. The Cambrian to Ordovician age Arbuckle Group is the primary zone for SWD in the midcontinent. Recent research has suggested a link between fluid injection and seismicity in the midcontinent; however, mechanisms for transferring pore pressure from zones of fluid injection to critically-stressed faults haven’t been well documented. The objectives of this research were to explore geologic processes that resulted in natural hydraulic fracturing of the Arbuckle, and to describe recent spatial and temporal variability of fluid pressures in the Arbuckle.

It is believed that accumulation and loading from rapid sedimentation caused abnormally high fluid pressures (i.e., fluid pressures above hydrostatic) in the Arbuckle when the midcontinent was part of an inland seaway. Other overpressuring processes such as hydrocarbon generation, diagenic dehydration, and aquathermal pressuring followed and caused fluid pressures within the sealed Arbuckle to exceed lithostatic pressures and result in natural hydraulic fracturing. Subsequently, abnormally low fluid pressures (i.e., fluid pressures below hydrostatic) resulted from uplift, erosion, and unloading of the same geologic materials that caused natural hydraulic fracturing. Present-day pressures in the Arbuckle, as a function of depth, in comparison to a pressure gradient of 0.456 psi/ft indicate that the Arbuckle is widely underpressured. Preliminary data also shows that pressure distribution varies with time and local zones of increasing and overpressuring are beginning to emerge. Follow-up research will examine the process of pore pressure diffusion from SWD wells and be integrated with seismological data to develop SWD best management practices for reduced risk for seismicity.

H2O Talks

William M. Alley, Ph.D.

Exploring the Adaptive Sports for the Disabled on the Ski Slopes and Outdoors

Thomas Hanna, RPG

An active member of the 29-year-old Adaptive Sports Association (ASA), long-time NGWA member Tom Hanna pursues his passion to help those with disabilities enjoy skiing and other outdoor sports. Through his involvement with ASA, he is able to work with students to overcome physical and cognitive challenges in a supportive environment.

Dave Spencer, the founder and driving force behind ASA, lost a leg to cancer while in college in Wisconsin. He came to Purgatory, Colorado, through a ski magazine advertisement after returning to skiing as part of his rehabilitation program. “When I discovered I could ski, I suddenly had the feeling I could accomplish anything I wanted,” Spencer said.

Through the years ASA has grown to encompass additional activities including rafting, kayaking, rock climbing, canoeing, bicycling, and overnight camping. ASA also provides sport and recreation activities for special education classes within the local school districts and trains Special Olympics athletes during the winter months. ASA serves more than 450 individuals with the help of almost 250 active volunteers. ASA’s programs help to enrich and transform the lives of people with disabilities through sports and recreation.

Hydrophilanthropy: What Can You Do?

Michael E. Campana, Ph.D.

Hydrophilanthropy, a term coined by NGWA member David Kreamer, Ph.D., refers to the practice of providing water, sanitation, and hygiene (WaSH) access to those who struggle to achieve these benefits that those in the developed world often take for granted. When you realize what the term means, your first inclination is to say, “Oh yeah, I understand. That’s what the Gates Foundation, World Vision, Save the Children, Water For People, and those other groups do. Not much I can do, except maybe write a check.” But there is more you can do. “What?” you ask.

Stay tuned as Campana, 40-year NGWA member, and founder and president of the Ann Campana Judge Foundation, a hydrophilanthropy he established in 2002 in memory of his younger sister, shows you what others like you are doing to bring safe water to the world’s forgotten people.

The ACJF works in Central America building WaSH systems and provides funding to others to do the same.

Managed Aquifer Recharge

Kyle Murray, PhD

An Evaluation of Aquifer Heterogeneity at the ASR Site, Sukhothai, Upper Chao Phraya Basin, Thailand

Rungruang Lertsirivorakul, Ph.D.

The Aquifer Storage and Recovery (ASR) system at Sawankhalok, Sukhothai Province is the first ASR project in Thailand. The site is located approximately 100 meters from the southeast bank of the Yom River. Recharge water is pumped from the Yom River during the region’s rainy season, and treated prior to injection. There are two main unconsolidated aquifers (upper and lower) at depths of 33-42 and 73-84 meters, respectively. The aquifer materials are mainly sand and gravel with intercalated clay lenses. The volume of water injected in the aquifers depends on the porosity and heterogeneity of aquifers. The heterogeneity in unconsolidated aquifers complicates predictions of flow gradient and direction. Wells installed in this area were expected to provide low yields and large drawdown during pumping. Groundwater and treated water samples were analyzed for a full suite of chemical analyses during the cycles of recharge and recovery tests. To identify the heterogeneity in an unconsolidated aquifer, two methods were used: groundwater-level analysis from injection or recovery schemes, and silica concentration gradients. The high heterogeneity area is identified by slow response of water levels in observation wells when injected water was recovered, as some observation wells showed higher water levels than others. Dissolved silica behaves conservatively in native groundwater at the site. Silica concentrations were evaluated to differentiate the zones of heterogeneity. The zones were also mapped and used as input data in groundwater modeling. The combination of hydrogeologic and chemical methods allow for more valid groundwater flow models and reliable predictions than those based on water levels alone. A final solute transport model is being simulated using total dissolved solids to predict the flow directions of the injected water.

Aquifer Storage Recovery for Agriculture—Experience in Northeast Oregon

Said Amali, Ph.D., PE

Aquifer Storage and Recovery (ASR) is a mechanism for storage of water from a surface water source in natural underground aquifers during the times when the surface water is available, for use when that source is no longer available due to natural causes or management rules. Several ASR projects have been implemented across the U.S. to supply municipal uses during peak demand periods. The relatively high cost of initial testing, infrastructure construction, and ongoing monitoring and management for these systems is balanced by favorable municipal rate structures. In the western U.S., the lack of available summer surface water and dwindling groundwater resources has focused attention on storage of more plentiful winter river water for summer use. However, the use of ASR for agricultural purposes has not become prevalent due to various factors, mainly that their cost has to be primarily borne by relatively few irrigators and cannot be passed down to consumers. Information from testing such a system in the Umatilla Basin of northeastern Oregon is used herein to evaluate the key parameters that are important in testing and implementing of such systems for agricultural uses. The Umatilla Basin system targeted storage of up to 100,000 acre feet of winter water from the nearby Columbia River. The system parameters such as hydrogeology, water treatment requirements, availability of existing infrastructure, role of power cost, and regulatory framework will be explored in the context of basin-wide cooperation and competition, consideration of conjunctive groundwater and surface water uses, and inter-state and trans-boundary water agreements.

Discussion of Aquifer Storage and Recovery (ASR) Permit Program, Thirteen Years’ Experience in Iowa (2000-2013)

Michael K. Anderson, PE

In March 1998, Iowa’s Governor signed House File 2292. The bill required the Iowa Department of Natural Resources to initiate a permit program for persons to inject, store, and recover treated water from aquifers for potable use. Rules were written in consultation with an advisory committee consisting of 10 representatives of professional/technical organizations, water utilities, and industry groups. The rules include the clarification of legal rights and obligations affecting ASR permit holders, the technical definition of the affected area within the aquifer, and provisions for “limited registration” for aquifer pre-testing before a 20-year ASR permit is issued. The rules were adopted in September of 1999. Engineering/hydrogeological criteria for the Department’s ASR project application review will be discussed. Four separate permits, covering six injection sites, have been issued in the ensuing years; Iowa’s policy experience with these types of wells will be discussed. Additional discussion will cover incorporating these “atypical” wells into the Department’s water allocation database.

Environmental Study of the Underground Dam on the Recharge of Om Lagsab's Underflow

Asma Gahrbi

The objective of this study is to develop a numerical groundwater model for the Om Lagsab system, localized in the area of Gafsa in the Tunisian Southwest, to bring out the impact of the underground dam on the groundwater resources and on the artificial recharge.

In a first stage, we started by collecting the data relative to the different variables as the climate and the hydrogeologic and physical characteristics of the Om Lagsab system; then we proceeded to the development of the hydrogeologic model of this aquifer.

In a second stage, the developed numerical model has been calibrated in steady conditions. The hydrodynamic parameters, which were obtained from the calibrated model, were later used in the simulations of various scenarios. We began with two scenarios: with and without the dam to determine its impact on the recharge of the groundwater system. The obtained results were not also satisfactory; the measured piezometric values and those calculated present important gaps.

Then a third scenario, with new hypotheses based on the geology, was essential to explain these gaps and estimate the role of the dam. The main conclusion stemming from these works is that the underground dam of Om Lagsab had no effective role in the recharge of the groundwater system. This dysfunction was due to the existence of permeable zones which engendered leaks in our reservoir.

Geochemistry of an Artificial Storage Recovery (ASR) System in Sukhothai Province, North-Central Thailand

Marcia Schulmeister, Ph.D., P.G.

A two-year ASR pilot project was initiated by the Thailand Department of Groundwater Resources as a means of alleviating flood and drought crises in the Upper Chao Phraya River basin in Sukhothai Province, Thailand. The injection site is located in central Thailand near the Yom River, which provides the recharge source when the river stage is high. Four short-term (30- and 51-day) cycle tests, conducted during the first year, were used to evaluate ASR system efficiency and site heterogeneity. Groundwater geochemistry and aquifer mineralogy were determined in 18 monitoring wells and continuous core samples from shallow and deep aquifer zones. Low, average total dissolved solid levels exist in both groundwater (166 mg/L) and river water (159 mg/L). The concentration ranges of chloride (<1 to 8 mg/L) and most major ions in river and native groundwater also overlap. Native groundwater is undersaturated with respect to quartz, carbonate minerals, and iron oxides identified in XRD and SEM analysis. The formation of amorphous iron oxide is indicated during storage, based on dissolved ion concentrations and geochemical modeling, while sorption and precipitation of other minerals are not observed. Dissimilar dissolved silica concentrations in river water (15, and higher average values in the aquifer, 39 mg/L), allow dissolved silica to be used to index groundwater and recharge water mixing during injection, storage, and recovery phases of the tests. Chemical aquifer heterogeneity and adjustments made to recharge water during the tests complicate conclusions made regarding ASR efficiency, but overall recoveries of 70%-97% were observed after 140% of the volume of injected water was recovered. Geochemical changes in the aquifer and during injection, storage, and recovery phases of long-term tests are being evaluated in the ongoing second year of testing.

Monitoring and Data Management

James J. Butler, Ph.D.

An Integrative Approach for Understanding Groundwater Processes Using Multi-Scalar Data in a Shallow Karst Aquifer

Stephanie S. Wong

In the Northern Segment of the Edwards Balcones Fault Zone Aquifer in Central Texas, managing groundwater-surface water interactions has been challenging during an epic drought, but has never been more pertinent. This karst aquifer is the source of local drinking water, spring flow is a desired future condition of the local groundwater conservation district, and an endemic salamander that inhabits the springs is a candidate for the endangered species list. Knowledge of groundwater recharge and its relationship to spring discharge are important for managing both water supply and critical habitat. However, these process relationships are difficult to characterize and quantify due to complex patterns of anisotropy and heterogeneity.

A study employing physical and chemical sampling methods and analysis of high-resolution topographic data is ongoing in the Northern Segment. Integration of both field-collected and remotely-sensed data increased understanding of aquifer processes. In the initial phase of the study, several physical and chemical sampling methods were applied to the Salado Springs area of the Northern Segment. Water levels from wells were measured to create a synoptic potentiometric surface under low-flow conditions (drought). The synoptic surface was compared to historical data to better understand aquifer change over a large interval of several years. Water level, temperature, and specific conductance were monitored over small sampling intervals using a multi-parameter datalogger revealing responses not visible at larger intervals. These data were related to precipitation data during recharge events, giving insight to aquifer responses. Dye tracing conducted in a key location confirmed old flowpaths and revealed flowpaths near springs discharging along Salado Creek. Utilizing multi-scalar physical and chemical methods resulted in different but complementary data providing new insights into groundwater recharge, storage, and flowpaths in this important Central Texas aquifer.

Enhanced Multi-Objective Optimization of Groundwater Monitoring Networks

Felix Bode

Drinking-water well catchments include many sources for potential contaminations like gas stations or agriculture. Finding optimal positions of monitoring wells for such purposes is challenging because there are various parameters (and their uncertainties) that influence the reliability and optimality of any suggested monitoring location or monitoring network.

The goal of this project is to develop and establish a concept to assess, design, and optimize early-warning systems within well catchments. Such optimal monitoring networks need to optimize three competing objectives: (1) a high detection probability, which can be reached by maximizing the “field of vision” of the monitoring network; (2) a long early-warning time such that there is enough time left to install countermeasures after first detection; and (3) the overall operating costs of the monitoring network, which should ideally be reduced to a minimum. The method is based on numerical simulation of flow and transport in heterogeneous porous media coupled with geostatistics and Monte-Carlo, wrapped up within the framework of formal multi-objective optimization. In order to gain insight into the flow and transport physics and statistics that control the optimality of monitoring wells, and thus in order to perform the optimization in a more formal targeted manner, we first use an analytical model based on the 2D steady-state advection-dispersion equation. Monte-Carlo simulation techniques are applied to represent parametric uncertainty. From this, we can obtain maps of contaminant detection probability for all possible placements of one individual monitoring well. Its optimal position is defined by the highest detection probability and describes a limit for meaningful solutions considering additionally early-warning time. Thus, a significant number of potential positions can be excluded from the optimization of entire networks, improving the computational efficiency of network optimization. Finally, we demonstrate that the individual well optima can indeed be found to be part of the results.

Monitoring and Data Management (cont.)

James J. Butler, Ph.D.

Best Practices for Reaching out to Private Well Owners

Steven D. Wilson

The Private Well Class is a free, online class for private well owners that has been very successful in reaching out nationwide to both private well owners and to those that serve them. Partners, that include managers of various private well owner outreach and sampling programs from around the country, have also provided insight regarding approaches and practices that have been successful from their own experiences. Applying the information gathered to date about best practices for reaching out to well owners, this presentation will discuss the motivations and factors that influence well owner participation, approaches that are more likely to get well owners engaged in outreach programs, and provide suggested best practices that will lead to a more informed well owner.

Collaboration Is Key to Successful Implementation of the National Ground Water Monitoring Network

Robert P. Schreiber, PE, BCEE, D.WRE

Reliable, accurate, and sustained groundwater monitoring is more important than ever. Groundwater resources are under new pressures because of increased energy demand, a focus on stream and wetland ecosystem health, and the impacts of climate variability and change. As these pressures increase, such legislation as the SECURE Water Act, which authorizes the National Groundwater Monitoring Network (NGWMN), offers hope that the federal government will provide the support needed. However, the tough economic conditions and federal budgeting problems have so far severely limited the appropriation of federal funds for the Network. In addition, many states report similar budgeting-related problems in securing funding for groundwater monitoring resources. Thus, it is even more important now than ever to leverage existing monitoring programs that are expected to receive ongoing support, while also exploring innovative means and methods that are anticipated to yield improvements in data-yield and cost-effectiveness.

Multiple examples will demonstrate the collaboration-focused efforts involved in the implementation of the NGWMN, which is being led by the federal Advisory Committee on Water Information (ACWI) Subcommittee on Ground Water (SOGW). The NGWMN is a collaborative effort among federal, tribal, state, nongovernmental organizations, private industry, and academia volunteers. The collaboration examples will focus on (1) inclusion of states in which prior collaboration between state agencies and the USGS has facilitated joining the NGWMN; (2) exploration of collaboration between USEPA Regional Laboratories and state data-providers for the labs to test samples sent by participating states; (3) discussions with other federal agencies that maintain monitoring networks whose objectives and designs align nicely with the NGWMN; and (4) consideration of promising technologies from ongoing R&D and proof-of-concept testing that have been identified through SOGW and other ACWI subcommittee initiatives. Input from conference participants will be encouraged, to enhance the collaborative efforts already underway.

National Ground-Water Monitoring Network Data Portal: Continued Collaboration from Concept to Version 2.0

William L. Cunningham

The development and implementation of the National Ground-Water Monitoring Network (NGWMN), spearheaded by the Subcommittee on Ground Water (SOGW) of the federal Advisory Committee on Water Information, serves as a shining example of collaboration and cooperation. The Network’s data portal stands as a key product of the collaborative effort, which included groundwater professionals from federal and state government agencies, professional organizations, private sector firms, and academic institutions. The Data Portal facilitates access to groundwater data through one seamless web-based application from data providers in partner agencies. A pilot scale portal was developed by the U.S. Geological Survey’s (USGS) Center for Integrated Data Analytics (CIDA) in 2011, which functioned as a proof of concept for enabling the retrieval of and access to groundwater data on an as-needed basis from multiple, dispersed data providers in a standard format. The system was also designed to allow the data to continue to be housed and managed by participating data providers, who hold the responsibility for data quality and maintenance, while being accessible for the purposes of the Network. The success of this pilot testing led to the rollout of Version 1.0 of the NGWMN Data Portal for wider use, including the addition of data providers as facilitated by the USGS in states with prior data collection and sharing arrangements. Subsequently, the developers at CIDA conducted usability testing in order to inform improvements to the portal and its underlying infrastructure, resulting in the recent release of Version 2.0 (http://cida.usgs.gov/ngwmn). The production portal now features enhanced search and download capabilities as well as improved stability and reliability. In the face of federal government budget appropriation difficulties and other challenges, the SOGW continues to press forward with its multi-sector collaborative approach toward full implementation of the Network, and further improvement of the Data Portal.

The Trials and Tribulations of Developing a County-Wide Water Level Monitoring Program

Sara Chudnoff, PG

Bernalillo County, located in central New Mexico, encompasses 1160 mi²and has a population of 662,564 (2010 census). The majority of the population resides in Albuquerque and adjacent unincorporated areas in the Rio Grande Valley (RGV). Much of that population is served by the local utility, which utilizes surface water and groundwater. To the east are the Sandia and Manzano Mountains, referred to locally as the East Mountain Area (EMA). The population in the EMA relies solely on groundwater, with roughly 53% of the population relying on domestic wells.

Water rights in New Mexico are governed by the Office of the State Engineer (OSE), which provides only limited monitoring in the EMA. County personnel began to hear anecdotes from residents and to notice rapid declines in water levels in county wells. In 2010 the county responded by implementing a voluntary domestic water level monitoring program, which increased the number of monitoring points, allowed for better water level tracking, and has saved the county thousands of dollars in monitoring well costs. Ongoing issues include methodology, clustering of volunteer sites, jurisdictional boundaries, and determining the appropriate scope of the program.

Since 2010 the program has grown to over 200 wells that are monitored biannually or quarterly. The program has helped educate residents about the complex hydrologic conditions, the limited groundwater supply, the effect of drought on water levels, and the necessity of ongoing interaction with the OSE. The program is still growing through word of mouth, public awareness, and the media. An internal database has been created to manage the dataset and the county is working towards a publicly accessible e-portal.

Monitoring and Data Management (cont.)

James J. Butler, Ph.D.

Detecting Distant Drawdowns with Water-Level Modeling

Keith J. Halford, Ph.D.

Pumping-induced changes of less than 0.1 ft have been differentiated reliably from environmental fluctuations with models of continuous water-level records. Environmental fluctuations are simulated by summing time series of barometric pressures, earth and gravity tides, and water levels in background wells. Pumping effects are simulated by superimposing multiple Theis solutions that translate pumping schedules into water-level responses. Environmental and pumping signals in water levels are differentiated with the water-level modeling software SeriesSEE, which is an Excel add-in. Once differentiated, drawdowns estimated from water-level models can be input into analytical or numerical models to estimate the transmissivity and storage coefficient of the aquifer being tested.

Drawdowns on the Nevada National Security Site (NNSS) have been detected definitively in observation wells more than a mile from pumping wells with water-level modeling in SeriesSEE. Pumping-induced changes from aquifer testing in volcanic rock beneath Pahute Mesa in the northwestern corner of the NNSS were detected in dozens of wells at distances of up to two miles. Elsewhere, drawdown was detected more than 30 miles from a pumping well in the southeastern part of the NNSS. A strong and unique signal was induced in the regional carbonate aquifer beneath Yucca Flat by a 500-gallon per minute, 90-day aquifer test at well ER-6-1-2 during 2004. Continuous water levels in Tracer Well 3, located in Amargosa Desert, responded to pumping and environmental fluctuations. A maximum drawdown of 0.05 ft was estimated in Tracer Well 3 from pumping ER-6-1-2.

Water Balance in the Guarani Aquifer Outcrop Zone, Brazil

Edson Wendland

The Guarani Aquifer System (GAS) is the largest transboundary aquifer in South America with an area of 1.2 million km²spread over four countries (Argentina, Brazil, Paraguay, and Uruguay). Despite the importance of the GAS as a major source of fresh water in the region, little is known about its recharge processes. The main recharge is supposed to occur in the outcrop zones of the Botucatu and Pirambóia Formations, representing approximately 10% of the total aquifer area. Aiming to estimate the groundwater recharge, a monitoring network has been deployed in the Ribeirão da Onça watershed, which appears to be representative for the GAS outcrop zones. Water table observation wells have been installed under different land uses (grassland, eucalyptus, sugar cane, and citrus cultures) and monitored since 2004. Direct recharge was estimated using a point-scale method (Water-Table Fluctuation) for each land use, after a careful determination of the specific yield. The average results indicate that the direct recharge strongly depends on the land use: eucalyptus forest (135 mm.y^-1), sugar cane (248 mm.y^-1), citrus (296 mm.y^-1), and grassland (401 mm.y^-1). The main climatological variables (precipitation, temperature, solar radiation, wind velocity) as well as the discharge at the draining creek have also been monitored, allowing the evaluation of the water balance in this watershed. The recharge contribution to the regional groundwater system was estimated to be approximately 3% of the annual average precipitation (1400 mm). The estimated recharge is important information for water management purposes since it can be used as an input parameter for regional groundwater models to predict water table levels and to assess potential future climate changes impacts in the GAS.

Panel: Is The New Generation of Professionals Adequately Trained To Meet the Current and Future Challenges?

Daniel B. Stephens, Ph.D., PG

Presentation by Brent V. Aigler

Brent V. Aigler

Presentation by Deborah L. Hathaway, PE

Deborah L. Hathaway, PE

Presentation by James F. Barker, Ph.D.

James F. Barker, Ph.D.

Panel: Superfund Combined Remedies - The Time Has Come

William M. Alley, Ph.D.

A Combined Abiotic- and Bio-Remediation Approach Saves Money while Improving Performance for In-Situ Anaerobic Remediation

Clint Bickmore, Ph.D.

Background/Objectives. The in-situ destruction of halogenated compounds is readily done by providing electrochemically reducing conditions. The chemistry is straightforward: simply provide electrons. However, the engineering and economics are a bit more challenging.

Approach/Activities. Many laboratory and field studies over the last decade have shown bio-remediation to be a valuable tool for chlorinated compound remediation, where the focus has been primarily on electron donor formulations that stimulate dehalogenating microorganisms. More recently, the science has advanced beyond the electron donor to include the pH stability of microorganisms, such that bio-remediation sites are now being engineered to include pH control and acid-tolerant cultures.

Organic compounds are not the only electron source. In fact, metals provide an effective electron source under corrosive conditions. In-situ zero-valent metal (zvm) injections and permeable reactive barriers (PRB’s) are common tools in the remediation field. The zvm sources vary in size and chemistry, including microscale and submicron options of iron, zinc, aluminum, and many alloys. The interesting aspect about in-situ metal corrosion is that it complements bio-remediation. The same process that provides the desired electrons for the chlorinated compound destruction also provides protons for bio-stimulation while generating counter ions for raising the aquifer pH. Combining injectable metals into a bio-remediation design makes a cost-effective “combined approach” strategy for site-wide performance.

We will present injection strategies for the three general site zones: source areas, detached sources, and plumes. Each zone has a different design approach that should reflect both the cleanup goals and budget priorities. Adding a network of real-time monitoring points provides insight into the transformation to an active reductive treatment area. Real-time physical parameter monitoring through time during and after a pilot study allows adjustment to injectate amendments, such as pH modifiers, electron donors, and metal powders in the full-scale design.

Results/Lessons Learned. A tailored approach to each of the remediation zones provides cost-savings by minimizing amendment costs and improving performance. Biasing the chemistry to abiotic reactions in source areas has a greater bang for the buck than pure biological reaction. Similarly, bio-remediation in the downgradient plume is cost-effective when enhanced by kick starting the chemistry with zvm addition.

Combined Remedies: Success by Design or Default?

Daniel Cassidy

Implementing a single technology often supports one or more unintended remedial process by default, which contribute to site cleanup. In some cases two or more processes occur simultaneously, or nearly so, but in others a transition period of weeks to months may be required for the follow-on remediation process(es) to ensue. Understanding the transition and relative contribution of each remediation process allows for all the contributing technologies to be incorporated into the remedial design. Data from numerous bench-scale treatability studies on combined remedies contaminated soil, groundwater, and sediments will be presented. Examples of combined remedies include in situ chemical oxidation (ISCO) with bioremediation, ISCO with in situ stabilization/solidification (ISS), and a combination of ISCO, ISS and bioremediation. Many commonly used ISS amendments can aid in chemical oxidation. Both aerobic and anaerobic bacteria can be exploited for biological polishing of organics. Sulfate-reducing bacteria can promote the precipitation metal sulfides.

Introductory Remarks and Framing of the Issues

James Cummings

Presentation by Kent Sorenson, Ph.D., PE

Kent Sorenson, Ph.D., PE

Panel: Water Quality is Not Expensive, it is Priceless

Kelly L. Warner

Presentation by Catherine Skinner

Catherine Skinner

Presentation by Joseph D. Ayotte

Joseph D. Ayotte

Presentation by Melissa Lenczewski, Ph.D.

Melissa Lenczewski, Ph.D.

Presentation by Sandy M. Eberts, P.H.G.

Sandy M. Eberts, P.H.G.

Poster Reception

A Method of Estimating Groundwater Return Flow to Rivers from Riparian Irrigation Districts

Jianting Zhu

An improved understanding of the water budget components in floodplain aquifers is necessary to implement and support water accounting requirements for use of river water. Of critical importance is the groundwater return flow as a result of recharge from irrigated water in a typical irrigation district near a river, which is the most uncertain and difficult component to be estimated. The objectives of this study are to (1) develop an effective but simple approach to estimate the amount of groundwater return flow to the river due to irrigation recharge, and (2) conduct uncertainty and sensitivity analyses of groundwater return flow to various recharge scenarios. The approach takes advantage of comprehensive drainage network typical in irrigation districts. The approach is evaluated and tested against numerical model results. It is found that the approach is accurate in calculating groundwater return flow for practical purposes with less than 10% error. We further examine how groundwater return flow may change in response to variations in recharge distributions using the proposed approach. As long as information about river stage, drain stage, and distributions of irrigation water is available, the approach could forecast changes in the amount of return flows.

Application of WSR-88D Precipitation Estimates to Shallow Groundwater Recharge in Complex Terrains

Andrew M. Worsley, Student

Quantifying shallow groundwater recharge in complex terrains is challenging from the standpoint of local variations in rainfall, runoff, and infiltration. Variability of terrain, vegetation, land cover, soils, and aquifer characteristics can mean that recharge rates are easily over- or underestimated using average rainfall amounts even in small watersheds. The use of radar-derived rainfall estimates from the National Weather Service’s Weather Surveillance Radar–1988 Doppler (WSR-88D) can provide critical information on the spatial distribution of rainfall. The radar-derived estimates, including those from the new dual-polarization rainfall algorithm, provide new opportunities to assess rainfall-recharge relationships. The goal of this research is to evaluate the role of WSR-88D rainfall estimates in refining recharge estimates for shallow aquifers with complex heterogeneity. Two shallow groundwater systems in central Texas have been chosen to assess the importance of spatially referenced precipitation in estimating shallow aquifer recharge. The Brazos River Alluvium Aquifer is a direct recharge aquifer system with heterogeneous soils and sediments that are sensitive to areal precipitation and complex land use patterns. The northern segment of the Edwards Balcones Fault Zone Aquifer is a karst aquifer that is sensitive to local precipitation on specific recharge features. WSR-88D rainfall estimates will be calibrated using rain gauge networks, while recharge estimates will be calibrated with spring flow, stream flow, and groundwater levels. Compared with data using only rain gauges, radar-derived rainfall estimates using WSR-88D provide more data on spatial distribution of rainfall that can enhance recharge estimates for shallow groundwater systems.

Assessment of Heavy Metals Contamination in Groundwater from Ain Azel Area, Algeria

Lazhar Belkhiri

Multivariate statistical methods and risk assessment were jointly used to define the spatial variation of heavy metals in groundwater and to assess the adverse health effects on the population. Three significant factors were extracted by FA, explaining 75.69% of total variance. These factors were in turn described by the clusters C3, C2, and C1, respectively, resulting from the Q-mode HCA. Multivariate FA and CA revealed significant anthropogenic contributions and water-rock interaction effects of the metals in groundwater. The ANOVA results showed that the variation of each of the heavy metals between the three clusters is highly significant (p < 0.05). The mean values of HEI and C_deg indices indicated that the water samples were contaminated with a high degree of pollution by Cd and Pb. The hazard quotients (via ingestion) of Cd and Pb were found to be higher than the safe limits, posing a threat to the consumers. However, no risk related to the dermal contact was associated with the measured metal levels.

Conserving Groundwater for Farming in Developing Countries: The Case of Mbaise, Imo State, Nigeria

Nduwuisi Anosike, BTech, OCA, OCP

Groundwater protection and management is of paramount importance in Nigeria's Niger Delta, where more than 80% of the inhabitants depend on groundwater as a source of drinking water, domestic uses, irrigation, and production of goods. Groundwater has been polluted by biological, chemical, and physical processes as a result of careless disposal and discharge of chemicals; industrial (mainly mining and petroleum) and agricultural activities and operations; and materials and structures on the earth’s surface through which contaminants percolate and seep into the soils and aquifers to contaminate the groundwater system and water supply.

In order to protect and manage the Niger Delta's groundwater system, it is wise to involve the community so as to implement certain community-based approaches, such as stakeholder participation. The community is enlightened and taught the use of microbial degradation processes to detoxify environmental contamination (bioremediation), which was first applied to petroleum hydrocarbon-contaminated groundwater systems in the early 1970s. In current practice, intrinsic bioremediation of petroleum hydrocarbons requires a systematic assessment to show that ambient natural attenuation mechanisms are efficient enough to meet regulatory requirements, and a monitoring program to verify that performance requirements are met.

The Niger Delta is one of the largest deltas in the world, the largest wetland in Africa, and also the third largest drainage basin in Africa. The environment is broken into four ecological zones: coastal barrier islands, mangrove swamp forests, freshwater swamps, and lowland rainforests. This is why the delta is highly polluted. Lack of community participation in the Niger Delta has been the bane on continuous groundwater contamination because the oil-contaminated sediment systems in the Niger Delta occur as a result of both point source pollution and non-point source pollution.

Estimating Evapotranspiration from Groundwater Level Fluctuations

Peng Deng

Groundwater evapotranspiration (ET) by phreatophytes in riparian zones is an important component of the water budget of many arid and semiarid environments. Diurnal fluctuations in groundwater levels have been used to estimate groundwater ET, but interference between nearby surface water (e.g., rivers, streams) and groundwater levels complicates the ET estimate. The objective of this study is to examine the influence of surface water level changes on the ET estimates in a riparian environment, thereby elucidating the potential caveats of using groundwater level diurnal fluctuations to estimate groundwater ET in riparian zones. The groundwater level and river stage data were monitored in a stand of Tamarisk Ramossisima on the Colorado River near Blythe, California, USA. Tamarisk Ramossisima is an obligate phreatophyte that requires direct access to groundwater for its source of water. Recently, several federal agencies are focusing efforts on eradicating or otherwise controlling Tamarisk. Results show that the most significant diurnal signal from the measurement of groundwater levels of monitoring wells can be attributed to ET; however, distance of the groundwater level monitoring wells to the river directly impacts our ability to separate the different signals from ET and river stage changes. For groundwater levels monitored near the river, the spectral analysis in both time and frequency domains gives strong indications of sensitive variations of groundwater fluctuation to water stage in the river. For wells closer to the river, although diurnal fluctuations also exist during high ET season, other site conditions were found to interfere with the fluctuations. As a result, ET estimates based on diurnal fluctuations of groundwater levels from wells closer to the river would have large errors.

Evaluation of Artesian Pressures in a Multi-Layered Aquifer System

Chris Beza, BS Geology, PG

Several pumping tests were performed in Washington D.C. in support of the District of Columbia Water and Sewer Authority’s DC Clean Rivers Project to control combined sewer overflows (CSOs) to surface waters of the District. The test site is located on the west bank of the tidally influenced portion of the Anacostia River approximately 3 miles northeast of its confluence with the Potomac River. The tests were conducted to evaluate the hydraulic properties of aquifers underlying the locations of two proposed large diameter deep shafts. These shafts will provide access to miles of future large diameter tunnels that will provide storage capacity to control the CSOs. During drilling of exploratory borings, two zones with significantly different groundwater pressure conditions were discovered within the confined aquifer beneath the site. While the artesian pressures in the confined aquifer were apparent, the higher pressures at depth within this same unit were not well understood. Pressures in the deeper zone were high enough to cause flowing conditions at the surface with its potentiometric surface more than 10 feet above the ground surface. A pumping well supplemented with observation wells was designed with two discrete screened intervals to evaluate the two zones and two pumping tests were performed. The first pumping test was performed with the pump intake placed between the two screens. Prior to the second test, the well was modified by filling the bottom portion of the well with sand and installing a K-type packer to test only the upper zone. Information from both tests was used to calculate the flow contribution and the hydraulic conductivities of each zone. The information was critical for the design of a groundwater control system for construction of the shafts.

Groundwater and Stream Water Dynamics in a Premontane Transitional Rainforest Using Stable Isotope Techniques

Andrea DuMont

Hydrologic, geologic, and biologic processes are critical to understanding the ecosystem in the tropical forests of Costa Rica. Precipitation is significantly lower during the dry season, and incoming rainfall can be completely intercepted and re-evaporated by the forest canopy during light events. Thus groundwater supplies the majority of water for streamflow, making it important for downstream use for drinking water and hydropower facilities. By using stable isotope signatures, we were able to reliably and precisely characterize the nature of these ecohydrologic processes to determine the influences on the groundwater system in a challenging environment with limited accessibility and complex subsurface conditions.

This study focuses on research conducted at the Texas A&M Soltis Center for Education and Research, near San Ramón, Costa Rica. We have monitored a 2.2 ha watershed there, measuring precipitation (averaged 4.4 m/yr) and transpiration rates for over two years (averaged 1.2 mm/day), and groundwater levels and stream flow (runoff, spring flow, baseflow) rates for nearly one year (averaged 0.09 m³/sec). Over a 40-day span during summer 2013, we collected a combination of daily and rain-event based samples throughout the watershed. Sources included: the main stream, two small tributaries, groundwater, pore water, throughfall and stemflow, and xylem water from 8 tree species across the watershed.

We then measured stable isotope fractions (δ¹⁸O and δD) in the water using a Picarro L2120i CRDS. Isotope ratios for surface water averaged -5.50‰ for δ¹⁸O and -28.00‰ for δD; baseflow was measured at -5.45‰ for δ¹⁸O and -29.18‰ for δD. Results of baseflow partitioning confirm that groundwater is the dominant source for stream water even in the wet season. We additionally conclude that in this watershed, groundwater transport to the stream is characterized by short residence times attributed to macropore flow in the subsurface, despite a low permeability of the andisol clay.

Groundwater Degradation in Nigeria's Niger Delta: When Oil Theft and Illegal Bunkering Take Center Stage

Innocent Kelechi Anosike, BEng, MEng, LLM

Rising incidents of oil theft in Nigeria's Niger Delta come at a significant environmental and groundwater cost. While several estimates have been made regarding the cost to the national economy in lost revenue and pipeline repair, no one has calculated the cost to the environment, groundwater resources, and the livelihood of the residents of the Niger Delta. No one has ever calculated the cost of restoring the environment, and treating as well as protecting the water resources and the marine ecosystem. But extrapolating from the cost of aquatic life in the Gulf of Mexico following the BP Gulf Coast spill of 2010, the cost to Nigeria's Niger Delta will amount to more than one trillion dollars. 2012 had an unprecedented level in environmental and groundwater degradation in Nigeria's Niger Delta due to oil theft and spillage; Shell Nigeria experienced 137 spills as a result of sabotage, pipeline vandalization, and theft, with the volume of oil lost amounting to 3.3 thousand tons. Nigeria puts the volume of oil stolen significantly above the 150,000 barrel a day estimate given by the United Nations. It is impossible to estimate the exact figures, because a well-financed and highly organized criminal enterprise exists on a phenomenal scale. Most of the stolen oil does not end on being deposited on the groundwater systems alone; rather it ends up in ocean-going tankers that transport it to refineries in other parts of West Africa, Europe, and beyond. A conservative waste/leakage/spill rate of 10%, which amounts to a crude oil spill rate of 40,000 barrels per day amounting to a cumulative annual spill volume of about 14.4 million barrels of crude oil, spilled into Niger Delta's environment and groundwater as a result of the crude oil theft enterprise and has left the region more devastated than ever before.

Hydrogeologic Guidelines for Large Scale Geothermal Heat Pump Systems

Kevin B. McCray, CAE

Lack of adequate hydrogeologic investigation is presenting major
challenges for some recent large scale (non-single family housing)
geothermal heat pump systems and surrounding groundwater.
In response, the National Ground Water Association is developing
guidance to help the HVAC system designer understand and use
hydrogeologic information to prepare project specifications and
achieve optimal system performance.
The National Ground Water Association has long been an advocate
for the sound application of ground source heat pump technology
and has developed guidelines for the proper construction of closed
loop heat pump systems, as well as advocated to Congress on behalf
of more widespread national utilization of the technology.
The Association recently compiled a database of state regulatory
oversight of GSHP installations.

Revisiting the Radial Collector Well: Applying New Technologies To Enhance Value

Michael D. Lubrecht, LG

Ranney collector wells have a time-proven history in the development of groundwater from connected surface water bodies. The general design and configuration of a Ranney well would be adaptable to other situations, however the cost and technological barriers to placing these wells limits their use typically to large municipal or industrial users.

Ranney collector wells entail extensive engineering and construction. A large caisson is constructed, then operators and equipment enter the caisson to work at depth to extend the radial segments from the caisson into the surround formation. The caisson itself must be constructed with a large enough diameter to permit down-hole work, and the extended laterals are limited in length and are not guided or steered in their construction.

In contrast, a Horizontal Directional Drilling (HDD) enhanced radial collector well may be scaled down considerably in construction and cost, while increasing flexibility in installation.

In practice, the HDD-enhanced collector is installed by first drilling a large diameter vertical well or installing a small-diameter caisson, with a maximum diameter of three feet. Then horizontal directional drilling is used to stand off remotely from the central caisson and extend the laterals to it, either terminating the laterals in the central well, or continuing through it to terminate either at the surface or at depth some distance away. Many configurations of this well are possible, depending on the water source and location, and the capture area desired.

Collector wells constructed in this manner may be considerably less expensive and of smaller construction and infrastructure footprint than larger Ranney collectors. This opens the technology for applications with fewer financial resources, as well as for locations with more limited groundwater availability.

Source, Migration, and Occurrence of the Potassium Rich Subsurface Brines in the Sichuan Basin

Wang Lidong

There are multiple salt-forming stages, from the Sinian to early Cretaceous, and multiple stable halogen layers in the Sichuan Basin. Some potash deposits have been found and the potassium rich subsurface brine structure also has entered the exploration stage. By the theory of modern sedimentology, geochemistry, hydrology geology, structural geology, mineral deposit geology, and the comprehensive analysis of outcrop, drilling, seismic, water chemistry, and geochemical data, the basin tectonic background of potassium bearing strata is reconstructed, and the main potassium sedimentary strata, the main types of sedimentary facies, the distribution of sedimentary facies, and paleogeography are found out. Combined with the hydrogeological data, it is thought: (1) the combination of the regional depositional model and the potassium rich subsurface brine genesis mechanism, and potassium element enrichment research and the rule of formation, migration of brine can effectively predict the regional potassium target zones and regional halogen containing structure delineation; (2) the marine evaporate basin, developed in geological period, is the main source of potassium rich brine; (3) the multi-period fault and fold structures, developed during when the basin formed, control the migration and accumulation of the potassium rich subsurface brine; and (4) pores and fractures, widely distributed in carbonate rocks of the basin, provide a good space for the potassium rich subsurface brine storage.

Poster Reception (cont.)

Communication Microcomponents Underground Waters of the West Siberian Megabasin with the Staging of Oil Formation

Vladimir Matusevich

Analysis of the conditions of migration of microcomponents in the underground waters at different lithogenesis stages shows that the redistribution of substance becomes most active starting at the later stages of diagenesis and the early stages of catagenesis (after N.B. Vassoevich). The main oil forming stage thus appears from the point of view of underground water geochemistry as a period of maximum enrichment of the waters in trace elements and organic matter.

Microcomponents of underground waters are very clear indicators of the processes in the oil formation. The set-in of the main stage is marked by a distinct jump in microcomponents concentration, which in West Siberia occurs at depths of 1500-2000 m.

A more detailed study of microcomponents distribution in waters, taking account of the temperature regimes in the various areas of the West Siberian basin, shows a differentiation in the depth of the concentration jump (in the Urals province, 1000-1500 m; in the Nizhnevartovsky province, 1500-2000 m; and in the Surgut province, 2000-2500 m). By the absence of decaying branches in the graph formation of oil we have predicted "big oil" in the north of Western Siberia.

The attenuating stage in the microcomponents concentration pattern differs less sharply from the main one than the preliminary stage does, although the drop in the content is clear in the Urals province at depths of more than 2000 m, and in the Surgut and Nizhnevartovsky, beneath 2500 m. Regional factors of the evolution of the geochemical picture of underground waters are intrinsically linked with lithogenesis and the stage in oil formation. This allows underground water geochemistry data to be used in solving theoretical problems of oil and gas geology and in making regional forecasts of oil gas prospects.

Determining Discharge from the Fallasburg Dam and the Hydrology of the Flat River Bypass Channel, Lowell, Michigan

Seth Kuiper

River channel discharge is determined by surface flow and groundwater interaction. Flow meter readings taken repeatedly over months at a transect 0.5 mile downstream from the Fallasburg Dam show that the Flat River Bypass Channel in Lowell, Michigan, is receiving less than the required dam release of 110 cfs. Monitoring wells and a minipiezometer were used to determine whether the river was gaining or losing between the dam and the transect location. Four monitoring wells installed along the river provided groundwater levels and the groundwater gradient. Minipiezometer readings in the streambed point to a losing river. Flow meter readings taken at the dam and 0.5 mile downstream on the same afternoon reveal losing conditions. River level data combined with discharge data indicate that the river shifts seasonally from gaining to losing conditions. The river valley topography and local climate suggest gaining conditions, but results show that the hydrology of the river is complicated. More work is underway to understand the interactions between surface water and groundwater.

Effect of Flow Rate on Physical, Chemical, and Biological Clogging Processes in Column Flow-Through Experiments

Angela Thompson

This study investigates clogging at slower injection rates through laboratory column experiments and geochemical analyses. Clogging in recharge wells is a major concern for aquifer storage and recovery (ASR) systems. Many of the current methods used to predict recharge well clogging assume a rapid injection rate. These methods may not adequately identify the clogging processes occurring at slow flow rates.

Further understanding of clogging factors at slow flow rates will aid in the selection of the most beneficial redevelopment and pretreatment methods for new ASR technologies, such as an ongoing project at the Kansas Geologic Survey (KGS) investigating a low-cost alternative to traditional ASR systems. This project utilizes gravity-induced recharge and small-diameter wells installed with direct-push technology to recharge and store groundwater in an alluvial aquifer in the Lower Republican River basin, Kansas. The KGS ASR system will have significantly slower injection rates than common ASR wells due to increased frictional losses in small-diameter wells and the absence of injection pumps.

To examine clogging processes at slow flow rates, laboratory columns packed with sand and gravel cores taken from the Pleistocene Belleville formation during direct-push well installation at the Lower Republican River field site are used for clogging experiments. Changes in geochemistry, turbidity, and hydraulic conductivity are monitored in three column sets running at rates of 1 m/d, 2 m/day, and 3 m/day. Each column set contains three columns circulating one column each of sterilized surface water, native aquifer water, and treated surface water. After a 20-day period, flow is stopped and biomass is quantified with PLFA analysis.

High-Resolution Quantification of Groundwater Flux Using a Heat Tracer: Laboratory Sandbox Tests

Brant Konetchy

Groundwater flux is the most critical factor controlling contaminant transport in the aquifer. High-resolution information about groundwater flux and its variability is essential to properly assessing and remediating contamination sites. Recently, we developed a new thermal method that has shown considerable promise for obtaining such information in an efficient fashion. This new approach is based on the previously proven concept of using a heat tracer to track groundwater movement and the development of fiber optic distributed temperature sensing technology for high-resolution temperature measurement (cable wrapping). Results of an initial field application indicated that heat-induced temperature profiles are very consistent with the hydraulic conductivity data from the same location, providing new insights into subsurface flow variations at the site. However, the relation between the thermal profiles and groundwater flux is only qualitative; a quantitative analysis is highly desirable in order to obtain a more definitive relationship between the heating-induced temperature increase and groundwater flux. In this work, a sandbox was constructed to simulate a sand aquifer, and a series of heat tracer tests are performed under different flow rates and heat inputs. By analyzing the temperature responses among different tests, we will develop a quantitative temperature-flux relationship, which can be used for the new thermal approach to directly predict groundwater flux under different field conditions.

Hydrogeologic Guidelines for Large Scale Geothermal Heat Pump Systems

Kevin B. McCray, CAE

Inventory and Monitoring of Groundwater-Dependent Ecosystems on National Forests and Grasslands

Joseph T. Gurrieri

Groundwater-dependent ecosystems (GDEs) are located across the landscape in every ecoregion of the United States. Although largely unrecognized, GDEs play an important role for both ecological and human communities. Groundwater-dependent ecosystems support a diversity of species, including a suite of rare biota and habitats, often serving as critical refugia during extreme climatic conditions. In addition to being ecologically important, GDEs provide key services to society, including high-quality water for human consumption, agriculture and industry, support for fisheries, and production of specialty commodities.

The Forest Service, in cooperation with The Nature Conservancy, has produced a set of Field Guides for inventory and monitoring of GDEs. These Field Guides will provide a consistent and scientifically sound approach to characterizing and monitoring groundwater-dependent resources. Rigorous field testing at several locations across the U.S. resulted in a user-friendly product and proved that the methodology is applicable in a wide range of different ecological and climatic locations.

Measuring Contaminant MASS Flux/Groundwater Velocity in a Fractured Rock Aquifer Using Passive Flux Meters

John N. Dougherty, PG

The development of cost effective techniques for the assessment and remediation of contaminated fractured rock aquifers has been identified as a science priority in EPA Region 2. This project, funded by EPA’s Regional Applied Research Effort Program, will research the ability of an innovative tool—a passive flux meter (PFM)—to measure groundwater flow velocity and mass flux in a fractured bedrock setting and to compare the results to current technology. The study will be implemented at a Superfund site in Puerto Rico where bedrock aquifers are an important source of drinking water. The goal is to research the ability of a fractured rock PFM (FRPFM) and standard PFM to measure groundwater flow velocity and mass flux in fractures in a fractured bedrock setting and to compare the results to current technology. A PFM consists of a cylinder of activated carbon impregnated with tracer compounds that can be installed in a well screened in unconsolidated deposits to measure groundwater flow velocity and contaminant mass flux. The fractured rock PFM (FRPFM) is an experimental system developed by the University of Florida. In this unit, the activated carbon fabric material of the meter is placed against the bedrock in the borehole wall and uses packers to isolate different sections of the open borehole. Both PFM designs are proposed to be installed in one existing borehole at three or four depths so that the data generated can be compared to information obtained by current technology from this and other boreholes at the site. Use of both PFM designs in the research borehole will allow comparison of the results generated by the different methods.

Reactive Transport Model for Drilling Fluid Contamination, South McMurdo Sound, Antarctica

Ellen Raimondi

This study explored the potential fate and transport of seawater-based drilling fluid used in the Antarctic Drilling Program South McMurdo Sound project (SMS). The SMS drilling reported a loss of 5.6 × 10³ liters of drilling fluid to the surrounding formation throughout a borehole depth of 1142 m. The objective of this study is to create reactive transport scenarios to model the extent of fluid migration into the borehole formation. To achieve this, the model included the effects of long term biodegradation on the fluid, changes in microbiological activity and geochemical parameters over time, and created a reactive model from the data to simulate fluid flow. The biodegradation experiment was designed as a microcosm set up and divided into aerobic and anaerobic samples which were incubated at different temperatures. For six months samples were collected for δ¹³C isotope fractionation, pH, dissolved oxygen, conductivity and major cations and anions. Supporting biological data observed the changes in microbial populations using Biolog EcoPlatesand polymerase chain reaction methods. The model used the RT3D program in USGS Groundwater Vistas package of MODFLOW. The model accounted for biodegradation kinetics and chemical processes, advection, and dispersion. This study compared the reactive model to a density model to illustrate the variation of the drilling fluid transport. The preliminary results indicated that drilling fluid will migrate from a few centimeters to meters within the pristine environments based on different scenarios.

The Ground Water Ammonium Sorption onto Activated Clinoptilolite Column

Azel Almutairi

The use of nitrification filters for the removal of ammonium ion from waste-water is an established technology deployed extensively in polluted ground water. The process involves the development of immobilized bacterial films on a solid packing support, which is designed to provide a suitable host for the film, and allow supply of oxygen to promote aerobic action. Removal of ammonia and nitrite is increasingly necessary to meet drinking water and discharge standards being applied in the US, Europe and other places. Ion-exchange techniques are also effective for removal of ammonia (as the ammonium ion) from polluted water. The capital and operating costs of ion exchange can be significant, particularly for large volume applications. Here we explore the performance of ion exchange columns in which nitrifying bacteria are cultivated, with the goal of a “combined” process involving simultaneous ion-exchange and nitrification. A combined process offers the potential reduction in the use of regenerant chemicals thus reducing costs and lowering environmental impact. Earlier studies show that limitation of oxygen supply can be an impediment to operation of fixed bed nitrifying filters in flooded mode. In this poster, the integration of a membrane module for in-situ introduction of air into biologically active ion exchange columns is described. The performance of fixed beds of clinoptilolite in the presence of nitrifying bacteria is compared to that in columns in which only ion exchange is occurring. Further comparison with columns equipped with in-situ aeration using the membrane-module is described. A number of different membrane materials were compared including polyethersulfone (PE), polypropylene (PP), nylon, and polytetra-fluoroethylene (PTFE). The results demonstrate the potential of combined nitrification and ion-exchange, and the effectiveness of in-situ aeration using a novel membrane module.

Tracing Creosote Contamination Through Slag Waste in a Hyper-Alkaline Environment, Chicago, Illinois

Kathryn Quesnell

The Calumet area of southeastern Chicago remains a legacy to industrialization and industrial blight. This area contained wetlands which were filled in with waste—especially slag waste—to make the area suitable for building. The slag not only creates heterogeneous underlying geology, but also produces a hyper-alkaline environment where the pH of the groundwater has been recorded as high as 13.3 and surface water precipitates calcium carbonate sediment. This complicated hydrogeological system also creates a unique environment for microorganisms specifically adapted to the hyper-alkaline environment. On the adjacent property is a decommissioned coking plant; creosotes, coke, and coal lie openly on uncovered ground. As hydrocarbons weather, depending on their original chemical composition, they will degrade into characteristic polycyclic aromatic hydrocarbons (PAHs). The goal of this research is to identify PAHs present in the nearby surface waters and groundwaters through use of GC/MS to determine if these organic compounds are influencing the alkaline environment. By comparing the ratios of certain target PAHs present, the forensic source of the parent material may be determined and potentially determine if they are the source of organic carbon in the adjacent alkaline sites. As remediation efforts are currently occurring in the area, understanding the geochemistry, weathering and decomposition, and distribution of known contaminants is vital for effective local clean-up. PAHs can be hazardous and toxic to both humans and the environment, and thus serve as a target contaminant for remediation efforts. However, PAHs may also serve as energy sources for the unique microorganisms in the area. Investigating the geochemistry of this site is critical to ongoing research of the unusual microbiology and groundwater patterns in the area, as well as providing information that could be used in current and future remediation projects.

Remarks by Department of Interior Assistant Secretary for Water and Science

Anne Castle

Remarks by Groundwater Editor Henk Haitjema

Research to Solutions: Contributions from UNESCO-IHP

Alice Aureli, Ph.D.

Skill Building for Early Career Professionals

Fine Tuning Your Interviewing Skills

Melissa Lenczewski, Ph.D.

Resume Writing for Graduate and Undergraduate Students

Melissa Lenczewski, Ph.D.

In the session, we will explore what goes into your resume and cover letter. We will also discuss the hiring process from start to negotiations. While this session is designed for undergraduate and graduate students that are initially entering the workforce, anyone who needs to write or review resumes in encouraged to attend. Bring a laptop or a copy of your current resume.

Superfund

Mike Wireman

Groundwater Tracer Investigations to Support Remedial Investigation—Rico Mining District, Southwest Colorado, USA

Mike Wireman

Stream water quality throughout the western United States continues to be degraded by acid mine drainage (AMD), a legacy of hard rock mining. The Rico-Argentine Mines in southwestern Colorado consist of complex, multiple-level, inter-connected mine workings connected to a drainage tunnel discharging AMD to a series of passive treatment ponds that discharge to the Dolores River. The mine workings are excavated into hill slopes on either side of a tributary stream with workings passing directly under the stream channel. Identification and characterization of hydrologic connections between surface water, groundwater, and underground mine workings was necessary to: (1) understand the source of water and contaminants in the AMD and (2) support feasibility assessments which will allow targeted remediation strategies to be developed. To identify hydrologic connections, we utilized a combination of natural and applied tracers including isotopes, ionic tracers, and fluorescent dyes. Stream tracing was conducted to characterize stream-groundwater and stream-mine workings connections. Two sets of tracers were introduced into mine workings at multiple locations to characterize flow through the workings. Stable water isotopes (d¹⁸O/dD) show a well-mixed hydrological system, while tritium isotopes indicate a fast flow-through system with residence time of years, not decades or longer. Addition of multiple independent tracers indicated that water is traveling through mine workings with minimal obstructions. The results from a simultaneous salt and dye tracer application demonstrated that both tracer types can be successfully used in acidic mine water conditions.

Isotopic and Geochemical Characterization of Water Movement Through Abandoned Mine Workings, Nelson Tunnel, Creede, Colorado

Rory Cowie

Long term acid mine drainage (AMD) discharging from the portal of the Nelson Tunnel near Creede, Colorado is currently impacting water quality in West Willow Creek and the Rio Grande River. We are using established isotope and geochemical tracer techniques to quantitatively determine the sources, ages, and pathways of waters in the mine. Preliminary results indicate that waters draining the mine are well mixed and composed to some degree of old groundwater, not just meteoric inputs. The stable isotope (¹⁸O) of the mine water is steady at -15 ‰ throughout the year, suggesting a well-mixed groundwater system composed of equal parts winter snow (-20 ‰) and summer monsoon rain (-10 ‰). Strontium ratios (⁸⁷Sr/⁸⁶Sr) suggest that most of the mine source waters are traveling through similar medium. Tritium (³H) values within the tunnel are primarily “tritium-dead” indicating water that is at least older than the “bomb-spike” waters of nuclear weapons testing in the 1960s. Additionally, dissolved inorganic carbon (DIC) δ¹⁴C testing indicates mine water on the order of hundreds to thousands of years of age. Results therefore suggest that mine waters are largely not directly connected to surface waters, or to the shallow groundwater (sampled from springs and domestic wells), but rather are likely entering the tunnel at intersections with a system of watershed-wide faults. To provide age verification for the DIC δ¹⁴C results, the mine water samples were also analyzed for the δ¹⁴C of humic components of dissolved organic carbon (DOC). Additionally, fluorescence index values of the final DOC isolates were produced to identify if the organic carbon sources were of terrestrial origin or microbially influenced.

The results from this study have helped develop a hydrogeologic conceptual model of the mine complex, which will aid in the development and feasibility analysis of targeted remediation strategies.

Superfund (cont.)

Mike Wireman

Bioremediation as a Full-Scale Remedy for a Trichlorethene-Contaminated Source Area and Diffuse Plume

Nathan Smith

The US EPA is completing a full-scale remedial action for a trichloroethene (TCE) source area and diffuse plume using bioremediation at the Bountiful/Woods Cross Operable Unit 1 Site in Utah. The site includes a high-concentration source area, with solvent concentrations as high as approximately 80 parts per million, and a diffuse plume that stretches approximately one-half mile downgradient. The contamination is present within the shallow aquifer, consisting of interbedded sands, silts, clays, and gravels. Initially, a pilot study was completed at the site to select the most appropriate amendment for stimulating reductive dechlorination. The selected remedy includes injection of emulsified oil into the subsurface to stimulate bioremediation; use of emulsified oil provides a long-term source of carbon (up to two years), while also enhancing mass transfer of contaminants from the non-aqueous phase into the groundwater. The source area remedy includes flooding the subsurface through injection into a grid-pattern of permanent injection wells, while the downgradient plume remedy includes injection into rows of injection wells (biobarriers). Advanced characterization using a membrane-interface probe was completed to identify areas requiring treatment.

Initial injections in the source area and first biobarrier were completed in late 2008, with a second injection completed in 2010. Reductive dechlorination was established within the source area within nine months after initial injections were completed, and complete destruction of groundwater contaminants was achieved within approximately three years after initial injections, with the exception of two hot spots. Targeted treatment of the hot spots has continued, with periodic injections of a sodium lactate solution to increase degradation rates of TCE and its daughter products. The downgradient biobarriers were installed in 2011, with injections completed during the summers of 2011 and 2013. Results indicate that substantial progress has been made in remediating contaminants in the diffuse plume using the biobarriers.

Delivery and Performance of Oil-Based EAB Amendments in a Heterogeneous Aquifer Using Shear-Thinning Fluids

Neil Smith, P.E.

Enhanced anaerobic biodegradation is being implemented to treat a residual chlorinated solvent source and dissolved phase plume at the Well 12A Superfund Site in Tacoma, Washington. The remedial objective is to reduce contaminant mass discharge from the source by 90 percent. The aquifer comprises a heterogeneous mixture of coarse-grained glacial outwash overlying fine and coarse-grained sedimentary deposits. Consequently, the hydraulic conductivity of the aquifer is highly variable. A thin silt unit containing high concentrations of trichloroethene and cis-1,2-dichloroethene is present over much of the site, acting as a continuing source of contamination. The treatment zone was defined as the area containing greater than 300 parts per billion TCE or cis-DCE, and soil concentrations in the silt greater than 5000 micrograms per kilogram TCE or cis-DCE. Treatment is targeted immediately adjacent and within the silt to reduce mass flux to the more permeable layers above and below. Shear-thinning fluid tends to increase flow through low permeability zones relative to high permeability zones, because the viscosity of the fluid is lower in the fine-grained units, allowing for amendment to remain in close proximity, and potentially penetrate, the silt.

The pilot study consisted of injection of shear-thinning amendment containing xanthan gum, waste vegetable oil, and a tracer blended using a high-shear mixer. Injection was completed into three wells, including one screened across the silt. An additional injection was completed using shear-thinning fluid containing a lipophilic dye, followed by soil core sampling for dye and indicators of oil amendment above and below the silt.

Results indicate that the shear-thinning amendment can be distributed as desired, and amendment was not lost to high-conductivity units. Areas where the amendment was delivered quickly exhibited reductive dechlorination.

Groundwater and Superfund on Long Island, New York—It's Not What You Drink

Robert Alvey

Long Island has a population of more than 3 million people, and is a designated “Sole Source Aquifer.” This designation was established to protect the drinking water supply as there are no alternate sources available, other than groundwater, for Nassau or Suffolk Counties. Long Island also is the home of more than 250 “Superfund” sites, the highest concentration in the nation. Discharges from a variety of sources have led to a significant decline in the quality of the underlying aquifer system. Significant efforts have been made to ensure that the distributed drinking water is “safe and clean.” The expense of ensuring a safe, clean, water supply for customers is increasing as treatment systems are added to public supply wells to meet tightening regulatory requirements, compounded by the frequency of contaminated plumes impacting the wells.

The paper focuses on efforts and coordination among agencies to investigate and manage Superfund sites on Long Island and the impacts of other, non-Superfund sources of contamination or threats to the groundwater aquifer system. The anticipated effects of “climate change” are also presented in relation to the sustainability of Long Island and its groundwater aquifer systems.

Groundwater Remediation in Karst Terranes: State of the Practice

David S. Lipson, Ph.D., PG

Groundwater remediation at sites located in karst terranes can be extremely challenging, impracticable, or even impossible within reasonable timeframes due to the presence of conduits that are difficult to locate, very high and even turbulent groundwater flow velocities, extreme geologic heterogeneity, dual-porosity and dual-permeability regimes, and sediment transport. Successful groundwater remediation can be further impeded when contaminants are transported deep within karstic geologic formations because the cost of investigating, remediating, and monitoring deep groundwater flow paths can be very high.

The fact that successful groundwater remediation in karst is at best very challenging within reasonable timeframes is highlighted by the fact that few peer-reviewed papers have been published on the topic, and little to no attention has been given to this topic at professional conferences. Nonetheless, the problem of groundwater contamination in karst terranes is both persistent and widespread because approximately 20% of the earth’s land surface is underlain by karst, and the presence of karstic features has not prevented the siting of chemical storage or hazardous waste disposal facilities within these terranes.

To better understand the state of the practice regarding groundwater remediation in karst and provide insights regarding future prospects, we retrieved records of decision (RODs) from USEPA’s superfund database for 71 sites in karst terranes. We reviewed the RODs and extracted information regarding site conceptual models and the evaluation, selection, and implementation of groundwater remedies. Lastly, we looked for trends in types of remedial strategies employed. Key results are that 53% of Superfund sites in karst had no active groundwater remedy, 37% of sites utilized pump and treat, and 21% of sites utilized some form of in-situ remediation technology. Only one Superfund site in karst had a technical impracticability waiver. Furthermore, performance-monitoring data generated at many Superfund karst sites may be inadequate for their intended purpose.

Setting the Stage: A Groundwater Transport Model Used to Support an Innovative MNA Approach

Mike Apfelbaum

A groundwater extraction and treatment system began operation in 1993 to provide hydraulic capture and limit off-site migration of volatile organic compounds (VOCs) at a Superfund site in southern New Hampshire. In 2003, following 10 years of effective operation and numerous optimization measures, 1,4-dioxane was analyzed for and detected in groundwater, which led to an Explanation of Significant Differences to modify the remedial action set forth in the 1988 ROD and establish a clean-up goal of 3.0 µg/L for 1,4-dioxane. Through December 2011, 149 million gallons of groundwater were treated; however, concentrations of select VOCs and more importantly 1,4-dioxane remained above ROD levels. To address these residual levels stemming from source area depletion effects, a detailed approach to evaluating the potential for MNA was predicated (and supported) by a groundwater flow and transport model. This model included two overburden units and two bedrock zones to simulate fracture flow using data obtained from local household well drilling, borehole geophysics, and hydraulic conductivity testing. The calibrated model was incorporated into a transport model using MT3D (Zheng 1990) to develop an understanding for both total VOC and 1,4-dioxane plume development and migration over time, based on key system operational periods. A series of forward-looking simulations were then used to evaluate plume configuration and contaminant magnitudes in the absence of remedial actions and with only natural attenuation affecting the respective VOC and 1,4-dioxane plumes. The simulations were conducted by adding an extended stress period with multiple time-steps after the stress period, simulating the most recent round of sampling data. The predictive capabilities of modeling were substantiated by a series of statistical and interpolative evaluations to assess plume size retraction and stability. The potential for in situ biodegradation of 1,4-dioxane was evaluated one-step further using environmental molecular diagnostics with a favorable outcome.

Superfund or Superwaste??????

Sudhir Burgaard

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) was as an answer to questions raised by Love Canal, Times Beach, and the Valley of the Drums. While one would think CERCLA would be a very useful tool for water providers dealing with contamination in their wells, its usage of late has turned against water providers. They have become targets of lawsuits, just as though they were the industry that caused the various contaminants and pollutants to impact the environment. They have also become the target of defendants who are brought into court by the water providers themselves. Cases filed by water providers result in counterclaims based mostly on the theory of “moving the plume.” That is, the well is pumped to serve water, but that pumping moves the contamination and this is actionable under CERCLA. And this outcome is technically correct, but in practicality it means that if a water provider finds a manmade chemical in its wells, it must stop pumping the well and never use it again. That way it won't have liability.

The only way to fix this problem is to have CERCLA amended to exclude from its scope of liability water providers who are pumping wells (and most likely removing the contaminants as a matter of public health and legal requirements). It sounds simple, but it isn’t.

To understand the dilemma facing water providers in this new world of responsibility for doing the right thing, will be discussed.

Superfund (cont.)

Andrew Schmidt

Challenges in Planning for Groundwater Remedy Transition at a Complex Site

William N. O'Steen

Complex groundwater contamination sites require comprehensive, structured groundwater monitoring in planning for transition to a new groundwater remedy. An example is the Medley Farm Superfund Site, a former waste solvent dump located in South Carolina. Groundwater contaminants at the site are primarily tetrachloroethene, trichloroethene, and their degradation products. Groundwater remedial action began at Medley Farm in 1995, using a groundwater extraction and treatment system. In 2004, in response to declining efficiency, groundwater extraction was suspended. Enhanced reductive dechlorination (ERD) via injection of lactate solution into the groundwater was initiated as a remedial optimization measure. Between October 2004 and April 2012, lactate solution was injected on multiple occasions. Responses of the hydrogeochemistry and groundwater quality to lactate treatment have been positive. In August 2012, EPA issued an Amended Record of Decision, changing the groundwater remedy to ERD. Monitored natural attenuation (MNA) was selected as a contingency remedy with the anticipation that as cleanup progresses, ERD may transition to MNA.

The Medley Farm Site presents challenges to transitioning from ERD to MNA. Prior lactate injections have varied with respect to injection volumes, locations, and timing. Groundwater monitoring and data analysis during the injection period have been structured to evaluate responses to the individual, irregular injection events. These factors limit data interpretation and predictive analysis. Site geologic features create variable and complex groundwater flow patterns. The spatial and temporal extent of lactate influence and sustainability of favorable conditions without lactate treatments are incompletely understood but are apparently highly variable, consistent with Site complexities. Transition from ERD to MNA and evaluation of MNA as a potential final remedial action will require changing the current site monitoring and data evaluation paradigm. EPA is planning for restructuring the monitoring and data evaluation program to better discern treatment effects and facilitate MNA evaluation.

Evaluation of Selected Groundwater Cleanup at NPL Sites

Linda Fiedler

OSRTI will present the findings of a new report that analyzes selected groundwater cleanups at National Priority List sites. The 43 groundwater cleanups in the report have achieved, or made significant progress towards achieving, their remedial action objectives (RAOs). The remedies evaluated include less difficult cleanups involving small dilute groundwater plumes in simple hydrogeologic settings to more difficult cleanups such as large plumes with high concentrations, complex hydrogeologic settings, and dense nonaqueous phase liquids (DNAPLs). The report analyzes key aspects of the groundwater remedies, including progress towards achieving RAOs, the remedial approaches applied, the contaminants addressed, hydrogeology, and the magnitude of the cleanup. Based on the analysis of the remedies in this report, the Superfund program has demonstrated that even challenging sites, such as those with DNAPLs and in fractured rock, can achieve significant reductions in contaminant concentrations and plume size, under a wide range of conditions. The program has also remediated sites to stringent RAOs, including those based on federal and state drinking water standards.

Water Quality Outside of Capture Zone Improves with System Operation

Jason R. House, C.G., P.G.

A CERCLA site in Central Maine is currently being addressed with source control via containment based on a pump and treat system designed using groundwater modeling of the flow system in fractured bedrock. Appropriately targeted field data collection efforts and monitoring allowed the development of a comprehensive fate and transport model vetted and accepted by State and Federal agencies for use in evaluating plume containment operations. A Technical Impracticability (TI) Evaluation conducted to address whether Source Area Groundwater could be restored to drinking water standards within a reasonable period of time supported the conclusion that a TI Waiver of chemical-specific ARARs would be appropriate for the Source Area portion of the Site. The final remedy selected for the site included Hydraulic containment of the Source Area Groundwater based on the groundwater flow model and a TI Waiver for the Source Area Groundwater, coupled with continued monitoring of and institutional controls for the Non-Source Area Groundwater. Operational groundwater piezometric monitoring results show strong agreement with model predictions. The data collected to date indicate that capture of the source zone effectively controls migration from the Site. Groundwater quality data from the first Five-Year review since the system became operational suggest that target VOC concentrations in Non-Source Area Groundwater beyond the capture zone are decreasing.

Superfund Perspective on Groundwater Remediation

James Woolford

Teaching and Training Tomorrow’s Groundwater Professionals?

Kathryn J. Butcher, CMP

Discussion Session: Mentoring Early Career Professionals

Kathryn J. Butcher, CMP

The groundwater industry, like others, is competing for talented individuals with solid science and good mathematics skills. How do we not only encourage young people to pursue a career in groundwater, but guide and nurture their professional growth when they’ve made that choice. Consulting firms and regulatory agencies are invited to share what has and hasn’t worked and new/early career professionals encouraged to share the activities that have and continue to benefit them. This is an open discussion and all Summit participants are invited to attend.

The NGWA Experience with Education and Core Competencies for Groundwater Scientists and Engineers

Kevin B. McCray, CAE

KEY WORDS - professionalism, standards, education, licensing, certification ABSTRACT Since 1988, the National Ground Water Association has formally supported recognition, through certification or some other means, of the unique qualifications necessary to perform hydrogeologic investigations. NGWA has believed reliance on professional engineers or individuals certified in an allied field without a determination as to their knowledge of groundwater science is not a justified position. The Association developed and maintained for a number of years a voluntary certification designation, the Certified Ground Water Professional. The lack of economic market drivers for the designation, one of more than one-hundred serving the environmental sector at one time, made the designation largely honorary, rather than a statement of marketable differentiation. Observation today suggests a need remains for greater hydrogeologic awareness among those that may create infrastructure intrusions into the groundwater environment, such as those designing and installing large-scale installations of geothermal heating and cooling systems. NGWA has responded with development of hydrogeologic guidelines for such projects. Also in partial response to the above named circumstances, the Association has developed an ANSI/NGWA standard defining the skills and competencies of groundwater personnel – from the trades to the science. Historically, NGWA scientific members have resisted the idea of accreditation of academic geosciences programs, including those for hydrogeology, although such discussions continue to be raised from time to time by groups such as the Geological Society of America and the American Geosciences Institute. The resistance seems to have been born out of recognition of the multi-disciplinary reality of groundwater science. NGWA funded research found that more than half of the respondents to a study of the business development practices for consulting groundwater professionals had been involved with groundwater issues for more than 20 years, and less than one percent had worked in the field for fewer than two years, raising the question of whether too few young people are being attracted to hydrogeology. Some speculate the seemingly minor emphasis on Earth science education in the U.S. K-12 system may lead to (1) employers of ground water hydrologists finding, on average, fewer applicants; (2) applicants with less depth of training in ground water hydrology; (3) need for additional on-the-job training among entry level personnel; and (4) greater salaries of all hydrology professionals.

The Contaminated Site Remediation Industry in China

Xin Song

The West and Water: Filtering Out the Conventional Wisdom and Producing More User-Friendly Historical Lessons

Patty Limerick

Twilight Session: Dynamics of Groundwater Flow

Klaus Udo Weyer, Ph.D., P.Geol., P.HG

Twilight Session: Specifier/Owner - Contractor Conflict during Well Construction Projects

Thomas Hanna, RPG

Twilight Session: Use of electrical resistivity in hydrogeologic problems

Kamini Singha

Twilight Session: Watershed Hydrology: Fracking, climate change, glaciers and other fun topics

Mark Williams

Welcome

Wells and Drilling

Thomas Hanna, RPG

Detecting Vertical Movement of Fluid in Wells and Aquifers with High Resolution and Over Long Times Using Fiber Optics

John Selker

There are few methods by which high-resolution, in-situ characterization of flow in aquifers is possible. We present a new method which has the potential to quantify both lateral and vertical components of flow in wells and nearby aquifers with 2-meter resolution. The method is based on a novel heating system combined with temperature measurements using a fiber optic distributed temperature sensor (DTS) that provides temperatures each 0.25 m and the ability to detect relative differences of about 0.01 °C on a sub-hour time scale. The method has three phases. In phase one, the background temperature profiles are recorded from which the vertical profile of thermal diffusivity may be obtained. In the second phase the borehole is heated uniformly over the depths of interest. Based on differential in cooling, this provides data to estimate lateral flux with depth. A key innovation is the third phase in which we apply energy to localized short sections (0.5m) of the cable, or heated “dots,” that are equally spaced (2m) along the well. The vertical migration of these warmed zones relative to the heated “dotted line” provides data from which the vertical fluid flow can be estimated. The concept is demonstrated in a 600 m borehole which had 300 heated patches. The method allows for high-resolution detection over an entire well’s depth and can remain in place and operable for many years. Numerical simulations are presented which further illustrate expected behaviors.

Exploring the Value of Manual Drilling to Academic Research and Training

Michael F. MacCarthy

Manual drilling techniques are increasingly being promoted as a cost-effective way of providing water for drinking and irrigation purposes in developing communities throughout the world. The relatively low cost of manually drilled wells, compared to machine-drilled wells or hand-dug wells, as well as the low cost and relative portability of their equipment, make them an attractive water supply option when hydrogeological conditions are favorable. Manual drilling techniques include the basic categories of hand auguring, percussion, sludging, and jetting. Hybrid techniques consisting of use of more than one of these techniques, alternately or simultaneously, often allow for improved drilling efficiency and increased drilling depth.

This research considers how manual drilling techniques can be of value in academic research and training environments, and consists of an assessment of percussion-jetting-rotation manual drilling, a low-cost hybrid technique developed in Bolivia. The equipment set-up is assessed for relevance in academic field research, where collection of hydrogeologic data is often limited by the expense of conventional machine drilling. The study also considers how manual drilling can be used to teach essential aspects of drilling concepts and groundwater science from a field perspective.

Ten monitoring wells were installed at the University of South Florida GeoPark using the manual percussion-jetting-rotation drilling technique, up to a maximum depth of 9 meters, through sand, clay, and thin layers of limestone. Drilling, well installation, and well development experiences were recorded. Geology was observed and logged during drilling. For training purposes, groundwater flow was determined between three wells. Hydraulic head and hydraulic conductivity were measured in each well. Well drilling techniques, basic groundwater hydrology, and well installation procedures were taught to engineering students. An additional, deeper well was being manually drilled in Fall 2013, to further test feasible drilling depths in an academic setting.

Wells and Drilling (cont.)

Thomas Hanna, RPG

Connate Groundwater from the Precambrian, South Park, Colorado

Terrance R Birdsall, P.G.

Groundwater supply investigations in fractured Precambrian metamorphic rocks for a cattle ranch near South Park, Colorado have revealed two separate aquifers: an upper, low-TDS aquifer fed by meteoric recharge, and an anomalous deeper aquifer of trapped, highly saline, CO₂-saturated water. The ranch is located near the western margin of the Elkhorn Thrust, where during the Laramide Orogeny, Precambrian igneous and metamorphic rocks were thrust over existing sedimentary rocks, such as the Cretaceous Pierre Shale. Geochemical and stable isotopic analyses of the water reveal the water is near-connate. It is postulated that the underlying sedimentary rocks are the source of this carbonated connate water.

After grouting the lower portion of the well to minimize the boundary effects of the lower aquifer, a method for tapping the upper, high-quality groundwater was developed and implemented. The method includes an in-hole transducer that measures and records electroconductivity, turning the well on and off using set upper and lower thresholds found to be acceptable to the cattle operation.

Estimation of Hydraulic Conductivity in Unconsolidated Near-Surface Aquifers Using NMR Geophysics

David Walsh, Ph.D.

In this research, we investigated the use of surface and borehole nuclear magnetic resonance (NMR) geophysical measurements to estimate hydraulic conductivity (K) at sub-meter to several-meter resolution in unconsolidated near-surface aquifers. Co-located surface NMR, direct push (DP) NMR, and direct push permeameter (DPP) K measurements were performed over three geologically-distinct unconsolidated aquifers with varying degrees of magnetic mineralization. At each location, multiple co-located NMR and DPP K measurements were performed over lateral distances ranging up to 1000 meters. K estimates from DP NMR measurements were directly compared to DPP K measurements at 0.5-meter vertical intervals at all locations. Optimized NMR-K calibration coefficients computed at different sites within each geographical location varied by less than a factor of 3, and the root mean square deviation between DPP and DP-NMR K was approximately 0.64 orders of magnitude. A significant and unexpected finding was that a single set of fixed NMR calibration coefficients performed nearly as well (at matching the DPP-K measurements) as locally optimized NMR-K coefficients. The surface NMR measurements provided adequate resolution to identify the high-K and low-K sections of each aquifer. Optimized NMR-K estimates for the surface NMR Carr-Purcell Meiboom-Gill CPMG sequence closely matched the optimized DP NMR-K coefficients across all data sets. In contrast, the optimized NMR-K coefficients for the surface NMR free induction decay measurements varied by more than an order of magnitude over the three geographic regions, due to differences in magnetic mineralization among the three aquifer materials. Overall, the results indicate that existing NMR-K transforms, originally developed and used to estimate K in consolidate limestone and sandstone oil reservoirs, can be employed to estimate K in near-surface unconsolidated reservoirs, but the optimized NMR-K transform coefficients can be up to two orders of magnitude different from those used in oilfield NMR logging.

Flowing Artesian Well Field Development in the Central Chi River Basin Project, Northeast Thailand

Tussanee Nettasana, Ph.D.

The flowing artesian aquifers in the Central Chi River basin are composed of a sequence of unconsolidated gravel, sand, silt, and clay units that were deposited by ancient rivers, the Chi River, and its tributary channel sediments. It is located in parts of Khon Kaen, Kalasin, and Roi-Et Provinces. While having been announced to be repeatedly a drought area, this area has been found to be hydrogeologically promising for a groundwater spring. The aquifers in this area consisted of an unconfined aquifer and two confined aquifers. The unconfined aquifer is composed of gravel, sand, silt, and lateritic soils. The thickness of this aquifer ranges from 10 to 30 meters. The confined aquifers are sandy gravel which is intercalated by clay layers. The depths to these aquifers are 30-50 and 40-150 meters, respectively. Many flowing-artesian wells were developed from not only unconfined but also confined aquifers with the potentiometric surfaces ranging from 0.5 to 8 meters above the ground surface. Three high potential areas were selected by the Department of Groundwater Resources to develop the flowing artesian well field pilot project for agricultural use. In each pilot area, three flowing wells 28 inches in diameters were drilled. The water from these wells was piped to five cylindrical fiberglass water tanks with a total capacity of 300 cubic meters. The irrigation piping system about 5000 meters long was installed and the agricultural group was formulated for the future sustainable management of this groundwater resource and its pilot system. Additional hydrogeological studies show that these aquifers are high productive aquifers and contain very good water quality, and can be the large source of drinking water. The detailed groundwater modeling, long-term monitoring of water levels, and chemical parameters will be conducted to ensure the sustainable development in this area.

Losses in Denver Basin Well Efficiency Due to Declining Aquifer Water Levels

Tara Meininger

Groundwater from municipal Denver Basin aquifer wells is the primary water supply for many communities between Denver and Colorado Springs, Colorado. The Denver Basin aquifers include Cretaceous and Tertiary age interbedded sandstone, siltstone, and shale subdivided into the Dawson, Denver, Arapahoe, and Laramie-Fox Hills sub-aquifers. The Arapahoe aquifer is the most prolific, with municipal well yields ranging from 200 to over 700 gallons per minute and depths ranging from 700 to over 2000 feet.

The Denver Basin aquifers are confined, and pumping exceeds recharge. As a result, groundwater is mined, and reported water level declines range from 10 to over 30 feet per year. Well efficiency is impacted by water level declines and dewatering of well screens during pumping. There has been ample water level decline research, but little analysis regarding changes in well efficiency with pumping water levels below the top well screen. Projections of future well yields with increasingly deep pumping water levels are critical for municipal water supply planning.

A municipal Denver Basin water provider has collected up to seven years of hourly water level measurement and pumping rate data from one Denver aquifer well and five Arapahoe aquifer wells. These data have been evaluated on the basis of specific capacity from more than 4800 individual pumping cycles to assess changes in well efficiency with varying pumping water level depths. No loss in well efficiency was identified with pumping water levels above 75% of the well screens (25% of screens dewatered). Two of the wells exhibited efficiency losses with pumping water levels below 75% of the well screens. These trends are used to project well yield with future water level declines and plan for development of new water supplies.

Zipliner Technology: Improving Safety and Implementability of Direct-Push Soil Sampling

Michael Gefell

One of the most common tasks in characterizing environmental sites is the collection of soil samples using direct-push tools with rigid, plastic liner sleeves. We estimate that tens of thousands of these sleeves are used annually in the U.S. alone. They traditionally have been opened using sharp blades that pose a serious hazard and have caused laceration injuries. The tearing action of the blade can leave a jagged edge at the line of opening, which itself creates a laceration risk. The study introduces a sampling sleeve with pull-tabs, which allow it to be opened without a sharp blade, thus improving safety and ease of use.

Zipliner technology (U.S. patent No. 8,459,374) was invented by ARCADIS. Geotech Environmental Equipment Inc. holds the trademark and license to manufacture Zipliner sleeves for AMS PowerProbe direct-push sampling equipment. Zipliner prototypes were tested in the field in shallow, fine- and coarse-grained soils (up to 6 meters depth). Zipliner sleeves are opened using a battery-powered drill with a specially designed bit known as a "ZipTool" or with needle-nose pliers.

As of September 2013, more than 1000 Zipliner sleeves have been used at field sites. Zipliner has operated comparable to standard liner sleeves under field conditions at depths up to 12 meters. Soils have ranged from compacted clays to silty sands to angular gravels. They have opened successfully without a sharp blade using Ziptool. Additional use in various geologic settings and depths may lead to further design refinement and will provide an understanding of the full range of Zipliner applicability in terms of depth, geologic settings, and temperature conditions. Future planned developments include the manufacture of Zipliner for use with other types of drilling equipment. The lead author received the 2013 National Ground Water Association (NGWA) Technology Award in recognition of the development of Zipliner.

Wells and Drilling (cont.)

Thomas Hanna, RPG

Comparison of Water Supply Well Drilling Methods

Steve Schneider, MGWC

Selecting, specifying or approving an appropriate well drilling method for large capacity water supply wells is often challenging. This presentation will discuss the pros and cons of the most commonly used methods. The comparison includes but is not limited to: equipment requirements and relative costs, geologic formations, artesian conditions, aquifer damage, development considerations, construction time, formation sample quality, interim water quality or quantity testing, site considerations, cuttings and fluid disposal.

Developing and Rehabilitating Water Supply Wells

Kriss Schneider

All large capacity water supply wells require development when they are initially constructed and they require rehabilitation during their expected productive years. This presentation will discuss different tools and techniques used for well development and rehabilitation and their appropriate applications for varying well designs. The discussion will also discuss the need for an appropriate plan and the generally accepted contents of a well-planned rehabilitation project.

Harmonics—Clean Power at the End of the Line

Larry R. Stanley

Within the pumping community, variable frequency drives (VFDs) have become an accepted control method for flow, pressure, and level regulation. The practical application of VFDs for control and tremendous energy savings may be overshadowed by the feasibility of power harmonic problems resulting from the use of these same VFDs.

This harmonic issue will be presented in an open and friendly discussion supported with a deliverable PowerPoint of 35 slides. We will start the presentation on a very basic note of "Why worry, what's there to be concerned about?" to document issues ranging from unexpected downtime to catastrophic failures.

Defining the problems will provide the gateway to discussing true harmonic abatement, utilizing readily available industry products such as line reactors, filters, and industrial grade variable frequency drives from competitive vendors, ensuring that you will have "Clean Power at the End of the Line".

Water Well Asset Management: Complying with the “Revised Total Coliform Rule” with Preventive Well Maintenance

Neil Mansuy

Water wells are becoming recognized as the most important asset in a groundwater system. As water systems age, deterioration is an almost inevitable consequence. In groundwater systems water wells will experience deposits building up, depending upon many factors. Formation damage as well as biological and mineral deposits will result in lost capacity problems and associated water quality problems, including total coliforms being detected in pumped water samples. Complying with the Revised Total Coliform Rule is often not as simple as disinfection of wells but more importantly requires that the well be cleaned and kept clean on a periodic basis. The occurrence of total coliforms most often do not suggest contamination of water wells but can suggest that the well needs to be cleaned. Novel ideas and understanding about well problems and solutions will be presented, based on many years of experience. Effective rehabilitation and maintenance can be very effective at maintaining peak efficiency as well as maintaining more consistent water quality. With budgets getting tighter and ever increasing energy costs of water production, cost-effective well maintenance can be used for fixed budget pricing and driving down life cycle costs. New effective and economical methods of well maintenance will be presented with case studies of cost savings and solving very difficult total coliform issues.