2017 NGWA Summit : Alphabetical Content Listing
Adam Arnold, MASc
New legislation passed in Ohio in 2014 added ‘recycled water’ as a source for private water systems serving fewer than 15 service connections or 25 people on average. An on-site DPR pilot study was run from 2013 through 2016, and the system is now indefinitely approved as a potable water source for the office building that it serves. Following an initial testing period with purified water discharged to the septic system, the water has been plumbed into the building since 2014 and approved for all indoor uses including drinking and cooking since 2015. Extensive testing overseen by regulators and reviewed by an international panel of water experts demonstrated the excellent quality of the purified water and reliability of the advanced water treatment process. To date, this on-site DPR system has reduced dependence upon the well and volumetric loading to the septic system by upwards of 1.5 million liters.
Charles Dunning, Ph.D.
Steven D. Wilson
F. Edwin Harvey, Ph.D.
William Alley, Ph.D.
Christian D. Langevin, Ph.D.
William L. Cunningham
Karilyn Heisen, P.E.
Murray Fredlund, Ph.D., PE
Developing a Regional Model of the Coastal Lowlands Aquifer System—Using Uncertainty Quantification as a Guide
Groundwater and Nitrogen Modeling to Prioritize Management Strategies for Suffolk County’s Estuaries
Daniel O'Rourke, P.G.
Utilizing groundwater models allows for a better understanding of the impacts of historic, existing and potential future land uses on aquifer nitrogen concentrations and ultimate discharge to water supply wells and estuaries. Groundwater models were utilized to better understand nitrogen loading from various land uses within watersheds as well as the impact of potential nitrogen reduction strategies such as the use of innovative alternative onsite wastewater treatment (I/A OWTS), clustered/decentralized treatment, or traditional sewering. Nitrogen loading models have been coupled with groundwater models to simulate the fate and transport of parcel-specific nitrogen loading throughout the County.
Suffolk County has launched a Subwatersheds Wastewater Plan in which baseflow contributing areas (subwatersheds) were simulated for more than 180 surface water bodies. For each subwatershed, time of travel (from the water table to surface discharge) zones are quantified and nitrogen loading from surface activities including wastewater, fertilizer application and atmospheric deposition are calculated. The nitrogen loads were simulated as parcel based point sources using fate and transport groundwater models which ultimately provided discharge loads to the subwatersheds and more than 700 community water supply wells. Simulated nitrogen loads to surface waters were compiled with quantitative and qualitative data and utilized in a decision support tool to rank and prioritize the subwatersheds for future management strategies.
Brianne Hastings, P.G.
A digital groundwater model was prepared for the facility to compare closure alternatives and to evaluate environmental implications of the facility after closure. The model consisted of nine layers and over 140,000 cells. It was constructed and calibrated to match observed aquifer conditions and groundwater levels within and surrounding LBR.
As part of the selected long-term closure program, the CCR impoundment will be capped with a geosynthetic liner and soil cover. An anticipated result of closure is a significant drop in the water level and subsequent settlement within the CCR material inside the impoundment. Recognizing that significant settlement could impact the surface drainage and final cover system following closure, the groundwater model was used to predict post closure groundwater levels. A long-term simulation was run to predict the water table draw-down 50 years after the final cover system will be placed. The simulated timeline included disposal, site closure options, and liner placement.
The post-closure water level is predicted to drop more than 100 feet with the maximum amount occurring where the CCR deposits are the thickest. The reduction in water levels appears to be greatly dependent on the areal extent of standing water on top of the impoundment. The majority of water drawdown within the CCR occurs within the first 24 years after closure. This analysis assisted in the selection of the final closure design for LBR.
Groundwater Modeling of a Deep Coastal Aquifer System in Tanzania Guided by Hydrocarbon Exploration Data
Matthew Gamache, P.E., D.WRE
The conceptual model was used as the basis for numerical model development. A three-dimensional groundwater model of the aquifer system was built, calibrated and applied to examine sustainability of aquifer development alternatives (including risk of seawater intrusion) and potential environmental impacts (stream reductions, wetland depletion). The regional-scale model, which covers 4,400 mi2 (73% of which are off-shore) simulates the hydraulic interaction between fresh and saline groundwater (with the deep aquifer interface estimated to be over 10 miles offshore) as well as discharges to surface water onshore.
Based on the modeling, the estimated quantities of groundwater that can be developed in the long-term from the KAS can be as high as 70 MGD, depending on how wellfield development proceeds. Different wellfield configurations were tested with the model, which indicated that sustainable yield is more likely to be constrained by available drawdowns in production wells and other operational constraints than by seawater intrusion. For the wellfield configurations selected for further development, the groundwater model was used to examine potential protection zones, potential environmental impacts, times of travel, and groundwater age.
Investigating Uncertainty of Groundwater/Surface-water Interactions in the Lower San Antonio River Basin, Texas
MODFLOW Validation of FEFLOW Model to Assess Sea Level Rise and Climate Change Drive Effects: Miami Beach Case Study
Carlos Tamayo, Civil, Engineer, M.S.
Miami Beach, FL, is a quite interesting example to analyze considering that it experiences a lot of what was mentioned above. It is a densely urbanized coastal city that is exposed to extreme weather events, sea level rise, and its residents and infrastructure are in a very vulnerable position. Residential and commercial high rises, high end neighborhoods, and preserved historic buildings are the general makeup of the city. Moreover, highly permeable formations, shallow groundwater levels, rising sea levels, and tidal effects, create a perfect setting for saltwater intrusion (SI) to occur and worsen through the years.
As part of a larger study, a FEFLOW groundwater model is being developed for coupling with a Mike 21 surface water model for assessing interactions between them. The City is the testbed and the broader goal is to evaluate soft and hard engineering solutions for adapting to SLR.
For this specific study, the main goal is to validate the FEFLOW model by taking the developed conceptual model and running it in a MODFLOW environment. The same baseline and time-dependent scenarios are simulated to perform an accurate verification of the FEFLOW model and compare equivalent results. Scenarios will assess the influence of sea level rise, tidal flooding, and extreme storm events with projections for year 2100. This exercise will allow for the robust coupled model to be validated and refined in order to make it scalable and replicable in similar coastal environments.
Multiple Tracer Testing Approaches for Improved Groundwater Flow and Reactive Transport Modeling Input Parameters
Raymond Johnson, Ph.D.
Tracer testing will be completed in the summer or fall of 2017 using multiple tracers and techniques at LM’s Grand Junction, Colorado, Site, which is located on a shallow alluvial aquifer adjacent to the Gunnison River. This tracer testing will include the use of borehole dilution, push-pull, and cross-hole techniques that focus on identified areas with elevated solid-phase uranium concentrations. The test data will be analyzed to estimate groundwater flow directions, velocities, and uranium transport parameters (sorption and dual-porosity influences) and be compared to previous estimates. This presentation will discuss how these multiple tracer tests were completed, interpreted, and then used to provide updated input parameters for revising the site groundwater flow and reactive transport models (conceptual and numerical).
Melinda Erickson, PhD, PE
Sasmita Sahoo, Ph.D.
Robert D. Mutch Jr., P.Hg., P.E.
N. Benoit1,2, D. Marcotte2, A. Boucher3, D. D’Or4 and A. Bajc5
1Geological Survey of Canada, Québec, Canada
2École Polytechnique de Montréal, Canada
3Advanced Resources and Risk Technology, LLC, Denver, USA
4Ephesia Consult, Belgium
5Ontario Geological Survey, Sudbury, Canada
In groundwater flow modelling, geological uncertainty characterization is a key input for risk assessment. The most influential geological uncertainty is attributed to the relative proportions, properties and spatial arrangement of the hydrostratigraphic units (HSU). The directional ordering of HSU is a critical component of sedimentary environments. This feature controls, to a large extent, the response of the system under a given external stimulus. Geostatistical algorithms, such as Bayesian Maximum Entropy method (BME) and Markov-type Categorical Prediction (MCP), present interesting features to impose directional constraints in categorical data simulation. In this study, we illustrate the ability of the MCP method to allow for trends and directional ordering in simulation. The MCP approach was tested first on a simple synthetic model and then applied to a regional 3D model in the Innisfil Creek sub-watershed. The required asymmetric transition probabilities between categories for MCP were extracted by Fast Fourier Transform computation from the transitional deterministic model. This model includes 15 hydrostratigraphic units displaying lateral variability and defined vertical ordering. The MCP realizations all reproduced hydrostratigraphic units in logical arrangements and proportions. The set of realizations appear globally unbiased with variations around the deterministic model. The resulting ensemble of geological models allows for the assessment of uncertainty of groundwater flow and transport as well as aquifer vulnerability and the delineation of wellhead protection areas.
Keywords : units ordering, categorical simulation, model uncertainty
Leslie Duncan, PhD
Katherine Knierim, PhD
Scott Morie, PG, CGWP, CHMM
Joseph Fillingham, Ph.D.
Farid Achour, PhD
These methods are hypothesis-free, and therefore, unbiased. They can be used to analyze multivariate data such as ground water level fluctuations and water chemistry simultaneously, collected over several sampling events in several wells. The purpose of the analyses is to evaluate and group wells based on the similarity in their temporal and spatial behavior. The methodology does not provide a "push button" solution, but requires the thoughtful and informed application of the various mathematical tools to provide output that can be used to meet the project requirements.
We present two studies focused on floodplain and sub-lake taliks in Interior Alaska that use chemical and physical tracers to characterize seasonal groundwater flow dynamics of supra- and sub-permafrost groundwater in discontinuous permafrost aquifers. Results from our study of the Tanana River floodplain near Fairbanks show that stable water isotopes, deuterium (δ2H) and oxygen-18 (δ18O), can be used to distinguish supra- and sub-permafrost groundwater. At a different study site consisting of two lakes with varying degrees of talik formation in the Goldstream Creek Basin near Fairbanks we combine the analysis of major cations and anions, alkalinity, basic field parameters, and stable water isotopes to distinguish sources of water and contributions to the lakes. Both studies demonstrate the complexity and seasonal variability of flow dynamics in open taliks as well as provide several conceptual models for the flow of groundwater within open taliks that can be used as a baseline for groundwater models in discontinuous permafrost regions.
Drilling and Installation of Deep Groundwater Monitoring Wells: Los Alamos National Laboratory, New Mexico
Mark Everett, PG
Major challenges to the characterization approach at LANL are to obtain maximum information during drilling and to meet sample quality requirements while minimizing drilling costs. Current drilling practice makes limited use of fluid additives to supplement air circulation methods to advance through the vadose zone. Starting about 100 feet above the water table, drill casing is advanced to the regional aquifer using only air and municipal water for circulation. The ability to retract casing for video and geophysical logs allows for robust characterization of perched groundwater systems and accurate definition of the top of regional saturation.
Current well design emphasizes a minimal annulus, maximum screen slot size, and thorough well development to mitigate formation damage due to drilling. Careful subsurface characterization at depths ranging up to 1,400 feet bgs, while retaining the ability to collect representative groundwater samples, may have application at a number of sites throughout the environmental industry. Optimizing each well to meet program objectives while reducing total project costs benefits all environmental investigations. (LA-UR-17-23451)
Evaluating Water Levels in the Northern Atlantic Coastal Plain using National Groundwater Monitoring Network Data
Data currently available for the NACP in the NGWMN are provided by water resources agencies in seven states. Differences in the procedures used to collect data and classify sites are presented because they affect the use of the data. Available water-level data for wells in the NACP from the NGWMN are used to begin to address questions listed in the Network Objectives section of the NGWMN Framework Document (2013). Spatial variations in water-level changes are shown using maps of changes observed over the past 10 and 30 years, respectively. Selected hydrographs over the extent of the aquifer system are shown to complement the change maps. Water-level change maps over the past 30 years in each of the five major aquifers of the NACP show the variability within the aquifer system. The current status of water-levels is shown by visualizing the most recent water-level in comparison to long-term monthly statistics. Other potential uses of NGWMN data in the NACP will be briefly presented.
Sara Chudnoff, PG
Adam Hobson, PG
Lead and Manganese in Untreated Drinking Water from Aquifers in the Atlantic and Gulf Coastal Plain, Eastern USA
Jeannie Barlow, PhD
The MBMG shares data through its Ground Water Information Center (GWIC) website (http:// mbmggwic.mtech.edu/), and web mapping applications. Data also are available through web services hosted on ESRI’s ArcGIS Server or Geoserver.
The MBMG selected its NGWMN wells based on Framework Document and “Tip Sheet” guidance available from the NGWMN web page (http://cida.usgs.gov/ngwmn/learnmore.jsp). Candidate wells had at least five years of water-level record and a monitoring frequency of at least quarterly. Other criteria included the aquifer extent, groundwater development, flow system position, and monitoring well density.
The selection process identified 227 wells for inclusion in the NGWMN. Each well’s hydrograph was evaluated against local hydrogeologic and land-use data to assign it to a Background, Suspected Changes, or Documented Changes subnetwork. Most wells show little-to-no anthropogenic influence and became part of the Background subnetwork. Hydrographs with anthropogenic signals (Documented Changes subnetwork) showed:
- Seasonal irrigation recharge—mostly from the irrigated alluvial aquifers.
- Seasonal irrigation withdrawals—mostly from the irrigated intermontane basins and buried glacial aquifers.
- Long-term depletion—locally from the upper Cretaceous Fox Hills-Hell Creek aquifer system in eastern Montana.
Data from Montana NGWMN wells are available through the NGWMN Data Portal (https://cida. usgs.gov/ngwmn/).
Radium Mobility and the Age of Groundwater in Drinking-Water Supplies from the Cambrian-Ordovician Aquifer System
Robert P. Schreiber, PE, BCEE, D.WRE
Tidal Influence on Remediation Sites: Understanding Predominant Gradients and Flow Inversion Effects on Mass Flux
Robert J. Stuetzle, P.Geo.
Seth Kellogg, PG
Kevin Svitana, Ph.D.
Jason Downey, PE
Down to Part Per Trillion Levels on a Remediation Site
As discharge regulations continue to tighten across North America, solution providers are required to evolve and adapt products and designs to meet new regulations.
In 2015, newterra developed a process design and created a treatment plant for remediating a heavily contaminated Superfund site situated on the environmentally sensitive shore of Lake Superior. As a former Manufactured Gas Plant (MGP), the site contained large volumes of weathered LNAPL and DNAPL that were collected and treated along with the heavily impacted groundwater and solids drawn from multiple extraction wells on the property.
The effluent from the treatment plant discharged to Lake Superior and was subject to strict permit requirements with discharge limits in the part per trillion range for the difficult to treat PAH compounds.
This presentation will guide the audience through the treatment objectives and challenges faced in developing the solution for this site. The presenter will walk through the process steps of bench testing, pilot testing and full scale design of the treatment plant – and share the lessons learned through commissioning and startup.
By sharing our challenges, technology selection process and experience from this project, delegates will be able to apply and build on the lessons we learned for their own remediation/water treatment initiatives.
Development of Klozur SP with a Built in Activator: Safe Storage / Mixing and Maintaining Treatment Effectiveness
Brant Smith, Ph.D.
Activated Klozur® persulfate has been implemented for over 10 years to successfully remediate sites impacted with a wide assortment of contaminants of concern ranging from petroleum hydrocarbons, oxidizable chlorinated solvents, and reducible organics such as carbon tetrachloride and 1,1,1-trichloroethane. The ability to treat different contaminants has been attributed to the activation method and the formation of the sulfate, hydroxyl, and superoxide radicals. Conventional methods of activating persulfate include iron chelates, alkalinity, heat, zero valent iron, and hydrogen peroxide. As these chemistries react with persulfate, it has required that the activator reagents be stored and mixed separately from the persulfate.
Certain sites can benefit from having the persulfate and activator delivered as a single bag and mixed into a single solution. However, activators can promote the decomposition of persulfate. This is the intended result in the subsurface needed to generate the oxidative and reductive radicals but should be eliminated or minimized when stored or once mixed into solution.
The objective of this work was to identify a blended activator-persulfate system that could be safely stored, transported, and batched together while still effectively treating the different contaminants of concern.
This presentation will discuss the existing methods of activating persulfate, conditions used to generate oxidative and reductive pathways, and then review key stability data and treatment efficacy of an all-in-one blend containing Klozur SP and a novel activation system. The stability data will show that the blend can be safely stored and transported. Stability and losses measured over time upon mixing will be compared to that of different organic activators. Finally the treatment efficacy of different activation systems in treating common contaminants of concern such as 1,4-dioxane, TCE, carbon tetrachloride, and benzene will be presented.
Keywords: ISCO, Klozur, persulfate, activation, organic
Evolving Regulatory Requirements, Health Effects & Cost-Recovery/Affirmative Litigation Options for PFAS
Laboratory tests were conducted in a series of batch and column studies. Batch tests included comparing solubility under different conditions, and evaluating characteristics of several activation methods. Column studies were conducted evaluating the treatment efficacy of common aqueous phase contaminants such as MTBE and 1,4-dioxane, and potential longevity under difference treatment conditions.
Field application included hydraulic placement of activated Klozur KP at 3 locations to address dissolved petroleum constituents and chlorinated volatile organic compounds at a former drum storage area. The targeted vertical profile was between approximately 7 to 11 m below ground surface, where a relatively large contaminant mass was concentrated in a relatively small aquifer volume. Injected solutions included a total of 1,350 kg of Klozur KP and 200 kg of ferrous lactate. Post injection monitoring for 1 year indicated successful distribution of activated Klozur KP and resulted in reductions of up to 99% contaminant concentrations.
The laboratory and field data show that persulfate derived from potassium persulfate is capable of treating a multitude of contaminants of concern and that potassium persulfate exhibits key characteristics that can be used by design engineers and implementers for a variety of site specific applications.
Seth Kellogg, PG
NGWA published this PFAS document to assist members and other groundwater professionals who may be tasked with investigating the transport pathways and extent of PFASs in groundwater and surface water, assessing potential risks to receptors, or designing and constructing engineering controls to manage subsurface PFAS contamination. The main purpose of this document is to summarize the current state of knowledge and practice regarding PFAS fate, transport, remediation, and treatment, recognizing that knowledge in this field is advancing. This document also aims to summarize current technologies, methods, and field procedures being used to characterize sites and test remediation and treatment technologies.
Jason R. House, CG, PG
Gregory Beyke, PE
Some hydrolysis reactions can be faster at high or low pH (alkaline or acidic). Some compounds undergo rapid neutral hydrolysis that is independent of pH. In addition, elevated temperatures speed up the hydrolysis reaction rate defined by the Arrhenius equation. ERH has been used as the method for temperature increases to escalate the rate of hydrolysis.
A half-life is how long it takes for half of a compound to be destroyed through the hydrolysis reaction. Seven half-lives produce 99% destruction; ten half-lives is 99.9% destruction. A half-life faster than 10 days is ideal and half-lives as long as about 40 days are still fast enough to be cost-effective.
Thermally enhanced hydrolysis is generally the most cost-effective remediation method for halogenated alkanes and many fumigants and pesticides. Thermally enhanced hydrolysis is also an important degradation reaction for pesticides, TNT, RDX, and trace amounts of Mustard Gas. ERH can now provide a reduced cost solution for heat enhanced hydrolysis of contaminants in soil and groundwater.
Research behind heat-enhanced hydrolysis of energetics and field case studies will be presented.
Impacted Groundwater to Drinking Water: Large Potable End Use Groundwater Remediation System Design & Permitting
Kirk Craig, P.E.
This presentation will then discuss where and why drinking water end uses for impacted groundwater are applicable to urban areas. It will touch upon what specific interests should be considered with respect to reclaimed groundwater, whether state-specific regulatory guidance should be developed and what we can learn from the associated policy implemented by California.
An accurate conceptual site model (CSM) was constructed in EVS displaying the bedrock stratigraphy and fracture network. Prior to remediation, a dye tracer test was conducted to provide further understanding of the fracture network and contaminant transport to improve remedial design. 3D models were generated to document the time elapsed dye distribution and transport within fracture regimes. The remedial approach was developed to accommodate observed groundwater velocities and target the preferential pathways identified during the tracer test. 3D visualization and analysis were performed on the contaminant mass and distribution, amendment distribution, and redox conditions. Modeled contaminant plume volumes in EVS were also used for mass calculations over time, providing a quantitative assessment of biodegradation.
Simultaneous display of both the hydrogeologic framework and groundwater chemistry data provided both a qualitative and quantitative assessment of bioremediation performance. 3D visualization illustrated contaminant migration along the fractured bedding-plane partings and tectonic fractures, position of subcropping discrete fracture zones with respect to source areas and injections, and evolving redox conditions. Delivery of amendments to targeted pathways and source areas within the fracture network was visually confirmed through 3D display. Mass reduction and dechlorination were assessed using the 3D volumetric contaminant and daughter product plume models. The ability to display geochemistry data within a 3D hydrogeologic setting provided a powerful tool identifying active biodegradation zones and assessing hydrogeologic conditions promoting or inhibiting the remediation of the source area.
George Losonsky, PhD, PG
While a complete HRSC in advance of remediation is an appropriate goal and defines an environmental management paradigm shift, many legacy, abandoned, and underfunded sites do not offer the luxury of this approach. Iterative cycles of site characterization, CSM refinement and remediation become fruitful when implemented using high density data and DPT investigative tools.
An example site in Louisiana has been the subject of iterative investigations which identified a retail gas station as the source of a petroleum hydrocarbon plume in groundwater seeping into and impacting a down-gradient stream. A dense DPT grid of in-situ chemical oxidation (ISCO) injection points near the stream bank identified localized pockets and channels of non-aqueous phase hydrocarbons not easily discernable using a traditionally drilled network of monitoring wells. Pressure and flow monitoring allowed injection of large volumes of oxidant into heterogeneous sediments. Data collected throughout the remediation effort led to a revised CSM and a cost-effective remedial strategy.
A corrective measures study recommended application of In Situ Chemical Oxidation (ISCO) using activated Klozur SP sodium persulfate to destroy residual TPH-D mass. A Soil Oxidant Demand (SOD) test was performed on soil and groundwater from the site to ensure sufficient oxidant would be applied to address both the non-target and target demands. Appropriate permitting for injections was secured. Preparation of field equipment, including injection well installation was completed prior to injection. The first injection of approximately 94,635 liters of 20% Klozur SP and 20 % NaOH solution was performed in 2016, followed by monitoring of oxidant persistence for 60 to 90 days. Subsequent TPD-D monitoring indicated a concentration reduction between 50% and 95% in treated soils. The TPH-D mass reduction was more pronounced along the perimeter of the targeted injection area. A second round of ISCO injections focused on the remaining TPH-D mass is planned, and results will be presented.
Thinking Outside the Boxcar: Combined Remedies using Single Application of Multi-Functional Amendments
Case studies are presented that demonstrate efficacy of this combined remedies approach. The sustainability of the approach is also assessed by evaluation of economic viability, social productivity and environmental protection. The case studies include combined abiotic and biotic degradation of chlorinated ethenes and ethanes compounds, combined reductive and microaerophilic treatment of chlorinated benzenes, and combined chemical oxidation and biodegradation of petroleum compounds. Case studies are supported with conventional concentration trends and advanced diagnostics including compound specific isotope analysis (CSIA) and genetic-based molecular biological tools (MBTs).
Eric Henry, LEP, LSP
The Water Resources of Louisiana Parishes project is about 70 percent finished achieving this goal with the publication of an online and hard-copy fact sheet for each of Louisiana’s 64 parishes (equivalent to a county). These 64 publications, which are generally 6 pages in length, provide summaries of groundwater and surface-water availability, water quality, current and historical water usage, and an extensive list of references for readers looking for more in-depth treatments of the topic.
William Greg Hamer, CHG, CEG
Adjudication of the Mojave River Basin is helping to reduce groundwater overdraft. Under the adjudication, nearly all groundwater pumpers have had to gradually reduce their pumping. As agricultural, municipal and industrial water users are faced with reduced supplies, a local water market has developed for both annual water allotments and permanent water rights. The value of annual and permanent water rights are related to the cost of imported water, which is also available in the basin, although in limited supply. The Mojave water market is helping to promote better planning for droughts, water conservation, and increased water system reliability.
Yu-Feng Lin, Ph.D., P.G., GISP
How best to deal with these challenges requires reassessment of energy policy, infrastructure, and efficiency. The U.S. Energy Information Administration reports production of renewable energy is the fastest-growing sector and will be for many decades to come. Production and utilization of fossil fuels is often limited by their geographical distribution. In contrast, geothermal energy is distributed more widely in volcanic rocks and groundwater. Estimated total amount of heat contained in hot dry rock is ~10 billion quads, 300 times greater than fossil fuels. Some studies have predicted that the growth of geothermal energy could be average 6.5% annually to 2040.
Heating, ventilation and cooling of buildings is a significant contributor to greenhouse gas emissions (~33% worldwide). Energy usage in buildings accounts for 34.8% of the total in the US and 27.5% in China. To power a building requires energy be converted into different forms, mechanical energy to electricity to heat, and potential energy to mechanical energy, electricity to heat, nuclear energy to mechanical energy to heat, etc. These conversions result in significant energy losses that ultimately lower overall efficiency. However, the use of groundwater (aquifers) to store and transfer heat would be much more efficient, but require the installation ground-source heating exchange system. To address energy efficiency issues, the role of groundwater in global energy security will be evaluated.
Thad Kuntz, PG
In the Nebraska Panhandle, two modeling efforts have been developed to provide decision support information, tools, and analyses of water resources management decisions. The Western Water Use Management Modeling covers the Southern Nebraska Panhandle and was created for two Natural Resources District's (NRD) and the Nebraska Department of Natural Resources (NeDNR). The Upper Niobrara-White Ground Water Model covers the Northern Nebraska Panhandle and was created for the Upper Niobrara White NRD and the NeDNR. The NRDs are governmental entities with locally elected Board of Directors that are responsible for regulating and managing ground water pumping over several counties.
These modeling efforts encompass nearly the entire Nebraska Panhandle between the Wyoming, Colorado, and South Dakota borders. The primary surface water bodies within the models are the North Platte River, South Platte River, Niobrara River, and Lodgepole Creek. The principal ground water system in the area is the High Plains Aquifer that locally consists of alluvial, aeolian (Nebraska Sandhills), Ogallala, and Arikaree aquifers. Each modeling effort utilizes three partially integrated models that consist of a surface water operations model of the North Platte and Niobrara Rivers; a regionalized soil water balance model to determine consumptive use; and a ground water model to simulate the ground water/surface water system and the effects of well pumping.
Recent analyses of the Ogallala and Arikaree aquifers have been conducted using the ground water models to simulate different ground water pumping allocations and climate scenarios which provide estimates of future aquifer drawdown, saturated thickness, and percent saturated thickness used. Ultimately, the results of these analyses are used to help educate and inform the public, open up a dialog on aquifer management, and provide the NRD Boards with information to aid their aquifer management decisions to determine future ground water pumping allocations.
In recent years, citizens, community interest groups, non-governmental organizations (NGOs), and professional associations have had considerable influence on the way in which groundwater resources are managed. Greater public awareness about the significance of groundwater has been a motivating force on public involvement. Issues such as hydraulic fracturing, bottled water and emerging contaminants have forced elected representatives to pay attention to resource protection and allocation policies.
Information, awareness and education about groundwater, much of it provided by NGOs and professional associations, has helped widen the suite of groundwater stake-holders. It is no longer just senior staff in state and federal agencies or the direct vested interests of groundwater end-users who have the ear of the political policymakers. Individuals and organizations with environmental, ecological, health related and socioeconomic priorities have shown they can impact decisions about groundwater use and source protection.
Groundwater governance strategies are principally developed to achieve sustainability while protecting a diverse range of vested interests by balancing economic, environmental and social issues within institutional political frameworks. Many agencies and units of government play a role in creating, implementing and policing groundwater regulations which are the basic building blocks of groundwater governance. Citizen pressure and the interventions of associations and NGOs can have a major influence on regulations and policy.
Leslie Dumas, P.E.
Fran Kremer, PhD
David S. Gould, P.E.
Opportunities and Challenges for Incorporating Threshold Effects in Linked Surface/Groundwater Management
S Andrew McGuire
James Schneider, Ph.D.
There are two fundamental requirements for this approach: 1) an intimate understanding of the water manager’s objectives for constructing the model, and 2) a very detailed understanding of the format of specific MODFLOW packages that may be incorporated into the model, and the ability to produce computer code that will manipulate the data in these packages. This is in addition to the traditional components that generally include the ability to construct and calibrate a groundwater model that is scientifically defensible.
This presentation will explore several projects that we have completed in Nebraska that have put water managers in the “decision making” driver’s seat. It has also empowered them with a tool that can keep their models current. They are now able to answer management questions in real-time in their own office faster and more efficiently than if they employed the hydrogeologists necessary to otherwise conduct these evaluations.
Todd Giddings, Ph.D., PG
Using High Resolution, High Accuracy Topography Data to Improve Water Management on the High Plains Aquifer
Douglas Hallum, P.G.
John Jansen, Ph.D., PG, PGp
Water scarcity due to climate changes and over abstraction make it very important to establish groundwater sustainability plans based on accurate hydraulic flow models. Often scattered and uneven spatially distributed boreholes and general geological maps are the only information available knowledges of subsurface conditions. Geophysical data, including TDEM, are therefore used in order to minimize model uncertainties.
TDEM is a non-intrusive, effective and cost-efficient method for obtaining information about the subsurface to 400m and sometimes even deeper. With the TDEM method, the hydrogeology can be described as variations in electrical resistivity. By comparing the resistivity with information from boreholes, the distribution of the different sediments can be described and thus create a valuable base for defining the basin boundaries or setting up flow models.
Due to high contrast in conductivity of fresh and brackish groundwater, the TDEM method is particularly suitable for mapping the mixing zone between fresh and saline water, which is important when sustainably managing groundwater abstraction in coastal areas or well fields influenced by saltwater intrusion.
When designing Aquifer Storage and Recovery (ASR) solutions, the TDEM method can be used for delineating areas having hydraulic conditions suitable for infiltration of surface water or treated waste water. In same way, data can help minimizing uncertainties when designing where to extract recharged resources.
The presentation will showcase different case studies where the TDEM method has played a key role in creating insight in the hydrogeological conditions. The method has been applied since the early 90’s and is the basis for the development of airborne systems for large scale mapping purposes.
Investigations of the Spiritwood aquifer in southern Manitoba by the Geological Survey of Canada and other workers, have demonstrated the value of helicopter time domain electromagnetic (TDEM) surveys in aquifer mapping and characterization using the contrasts between Quaternary glacio-lacustrine sand-gravels (high resistivity) that are relatively permeable and clay-tills (low resistivity) that are relatively impermeable, as well as the deeper, much less resistive Cretaceous Pierre Formation Shale basement rocks. This success provided the impetus for the North Dakota State Water Commission to fly a VTEM helicopter EM survey in the Jamestown, ND region in October, 2016.
The VTEM data collected over the Spiritwood-JT block allowed for geological mapping from near surface to depth, in spite of relatively weak resistivity contrasts (<10X). These data were inverted with a layered-earth algorithm to produce resistivity-depth models. These models were able to resolve the location and depths to the top and bottom of the Spiritwood aquifer throughout the central portion of the block providing more detailed pictures of the aquifer’s geometry. In addition to resolving the main aquifer as well as its deeper channels, the VTEM data and models highlighted several smaller, previously undiscovered aquifers that cross-cut/branch-off from the main Spiritwood channel. These are interpreted as probable transverse low-K barriers that were apparent from the existing test drilling and aquifer testing.
Combined use of Transient Electromagnetics, Passive Seismic, and Nuclear Magnetic Resonance Methods to Characterize an Unconsolidated Aquifer on Cape Cod, Massachusetts
Carole D. Johnson
The borehole was drilled using the sonic drilling method, requiring injection of freshwater during drilling. Bedrock was encountered at 93 m bls. The borehole was completed to bedrock using polyvinyl chloride (PVC) casing. Differencing of electromagnetic (EM) logs collected ~10 and 100 days after drilling delineated intervals where formation water displaced drilling fluids in discrete zones of higher porosity and k. These zones were confirmed with borehole nuclear magnetic resonance (NMR) logs that provided water content and k estimates every 0.5 m. NMR results indicate that porosity ranges from 0.19 to 0.42 with an average of 0.33, and k ranges from 0.5 to 405 meters per day (m/d) with an average of 54 m/d, results that are consistent with local- and aquifer-scale measurements. HVSR- and TEM- derived depths to bedrock were within 5 and 1 percent of the drilled depth, respectively. The TEM-estimated saturated thickness and fresh/saline-water interface was within 2 percent of the contact interpreted from the EM logs.
These results demonstrate the utility of combined TEM and HVSR methods for mapping the subsurface conductivity structure and thickness of unconsolidated aquifers and the efficacy of NMR logging to provide continuous logs of hydrologic properties in PVC-cased boreholes.
Estimating the Distribution of Hydraulic Properties Using Resistivity Models Derived from Airborne Geophysics
Inhomogeneity of topsoil often exceeds what can be verified by boreholes. Non-invasive Geophysical investigations can efficiently increase our knowledge and thereby minimized structural uncertainties in near surface hydraulic modelling.
High resolution geophysical multi coil Ground Conductivity Meter DualEM421 investigations have shown to be a successful tool for detailed mapping of the soil conductivity within the upper 5-7 m. Combined with shallow boreholes, hydraulic head measurement and simple infiltrations test, detailed description of the hydraulic conditions of the near surface groundwater is obtained. Surveys can be scaled according to size of area and needs for resolution.
Experiences shows a strong relation between electrical conductivity measured with DualEM421 and geological conditions which again are strong related to hydraulic conductivity obtained by infiltration test e.g. double ring infiltrometer test. Site specific relation leads to significant improvement of data input for near surface 3D geological and hydraulic modelling, and thereby optimizes the assessment of hydraulic consequences for specific LID/SuDS and aquifer recharges solutions.
Knowledge of the spatial distribution of high permeable sand layers and less permeable clay layers is crucial when pointing out the optimum location for artificial infiltration.
LID/SuDS solutions for handling rainwater are often a necessity and an integrated part in the development of urban and suburban areas. Aquifer storage and recovery (ASR) is a commonly used tool for sustainable water resource management. Beside rainwater the reuse and infiltration of treated wastewater is an important source for maintaining water availability in water stressed environment.
Presentation will showcase example from both urban and suburban investigation, where integrated investigation has provided an improved knowledge and minimized uncertified when planning LID/SuDS solutions.
Rick A. Hoover, PG
John Jansen, Ph.D., PG, PGp
Seismic reflection surveys collect data on the propagation of seismic waves to depths of several thousand feet. Developed by the oil and gas industry, seismic data can be used to map structural features in fine detail. Modern processing and interpretation techniques can map aquifer units, faults, and other structural features that can control well yield. With a little more processing, the shape of the waveforms can identify changes in the stratigraphy, porosity, and pore fluid characteristics in a unit. Seismic attribute processing can be used to identify permeable features such as narrow channel sand deposits at depths of thousands of feet to target permeable zones.
The cost to acquire reflection data is relatively high, which has limited the application of the method for water supply applications. Fortunately many areas have libraries of existing reflection data from previous oil and gas exploration activities. This data can often be purchased for a few thousand dollars per mile and used to map units that can potentially serve as aquifers.
Several case histories will be presented to demonstrate how modern interpretation methods can be used on 2D or 3D seismic reflection data to map features such as sand channels, faults, and pinch outs in aquifer units and direct drilling programs toward higher yielding sites.
Robert M. DiFilippo, P.G.
Evaluating Best-Practice Capacities for a Carbonate Island Karst Aquifer: Northern Guam Lens Aquifer, Guam, USA
John Jenson, PhD
We present results from an ongoing modeling study directed at estimating aggregate production that could be achieved by a system of about the same number of vertical wells as in the present system but in which well locations and well-field production are chosen to maximize production for specified standards of salinity. Natural limits are imposed by specifying the same recharge and aquifer properties employed in the recent successful modeling study of the existing system.
Although an ideal production system as defined above may not be feasible in the near term, if ever, an estimate of the total production that could be obtained by such a system for specified salinities provides helpful insights for long-term planning and future decisions regarding sustainable management of the NGLA.
For a Better Understanding and Management of Karstic Aquifers: Characterization of the Properties of the Big Spring Karstic System (Missouri)
Alain Mangin, Ph.D.
To better study, exploit, and manage karstic aquifers, a new approach using systemic analysis is currently used by Ramboll Environ. The overall behaviour of the aquifer is no longer considered to be the result of the sum of spatially individualized behaviours, which is assumed and imposed by the differential approach, but as the sum of the interactions of these individual behaviours that most of the time are unknown. The karst is thus conceived as a set of dynamic processes (flows) whose study and understanding must lead to the identification of its properties, allow a description, and ultimately facilitate its exploitation and management. While this concept is easy to understand, and seems able to solve the difficulties encountered, its implementation remains subtle.
The Ramboll Environ approach derives from a philosophy different from the conventional hydrogeological approach and requires abundant robust collection of continuous data, using transducers of the various parameters that monitor the functioning of the karstic aquifer (discharges, water levels, rainfall, etc.). This approach involved the development of a set of methods and high-performance software to extract information from the collected data in order to recognize the physical signatures that are responsible for the observed hydrodynamic behaviour, and thus, whatever the difficulty encountered, including non-linearities, characterize the dynamics of systems and predict their behaviours. These methods are called correlative and spectral analyses, continuous or discontinuous wavelet analyses, rescaled range analysis, fractal or multifractal analyses and attractor analyses.
The application of these analyses to Big Spring, Missouri allowed the establishment of an “Identity Card” of the spring, encompassing all information necessary for an optimal management of the spring.
Michael Alfieri, P.G., P.Hg., CGWP
Keywords: “ground-truthed”, “ground-truthing”, photolineament, photolinear, fractures, fissures, joints, faults, fracture trace, geology, stratigraphy, karst, sinkholes, conduits, ground penetrating radar (GPR), seismic refraction, seismic reflection, standard penetration test (SPT) borings, cone penetrometer test (CPT) soundings, and Hillsborough County, Florida
Alan E. Fryar
Volatilization of Trichloroethene from Groundwater in Karst, Mitigating a Human-Health Concern in a Show Cave
In 1990, the U.S. Geological Survey (USGS) detected TCE in a spring within a commercial show cave near a Superfund site, subsequently (2002) the Missouri Department of Natural Resources (MDNR) detected TCE in air inside the cave. TCE levels inside the cave became a concern after the U.S. Environmental Protection Agency (USEPA) lowered allowable TCE concentrations in air, resulting in the owner closing the cave for several months during 2016. Collaborative efforts between the USGS, USEPA, MDNR, cave owner, and a potentially responsible party (PRP), investigated TCE transport within the cave system using a network of airflow and temperature monitors and periodic water and air sampling.
Volatilization from groundwater in the karst system beyond the mapped cave extent generates substantial TCE concentrations in cave air. During the summer when outside air concentrations are higher than cave air, convection moves this TCE-contaminated air “downcave” though toured areas to the cave mouth. During the winter when outside temperatures are lower than the cave, flow reverses with fresh air entering the cave mouth dramatically decreasing TCE concentrations inside the cave. In the summer nearly 20% of the TCE flux occurs in the cave air. Concentrations peak during fall and spring when outside temperature approximates cave temperature and airflow stagnates. A mitigation system was designed to reproduce “winter-like” airflow that have historically produced the lowest TCE concentrations in air and allowed the cave to reopen for tours.
Garrett Rapp, PE
Surface water models for the watersheds overlying the Chino Basin were developed to: estimate the benefits of the recharge projects throughout the basin, understand the interaction of recharge facilities on the same stream system, optimize the scale of the projects, estimate the recharge from low impact development projects, and estimate downstream impacts on the Santa Ana River. This methodology is transferable to most areas where increasing groundwater recharge is desirable.
The facilities included in the 2013 RMPU range from redesigns of passive storm water retention basins to new stormwater storage and transfer facilities. The project stakeholders include regional and retail water agencies, private companies and 300 overlying pumpers. CBWM and IEUA are currently implementing the 2013 RMPU. The recommended 2013 RMPU projects are presently in design, and CBWM and IEUA anticipate that construction will be completed by 2020.
This talk will focus on the process used by CBWM and IEUA to conduct and implement their recharge master plans, the use of surface water modeling as a tool for evaluation, how well the master plan facilities performed compared to the plan, and how this same master plan process can be extended elsewhere.
Wes McCall, PG
During field work, subtle variations in the EC log across the coarse-grained aquifer were observed where the corrected HPT pressure log was flat. A strong relation also was observed between groundwater specific conductance and bulk formation EC in the coarse-grained aquifer facies. Modeling of field data found that the DP EC logs follow Archie’s Law in the aquifer facies even at the relatively low dissolved ion concentrations observed. Negative EC anomalies were observed where fresh water recharge was occurring below local storm water retention basins. Conversely, positive EC anomalies were observed where brine from the underlying shale bedrock was impacting the water at the base of the aquifer. These results demonstrate that the HPT-GWS can be used to define formation hydrostratigraphy at the centimeter-scale and sample for contaminants at multiple depths (profiling) in unconsolidated, permeable formations. The system also could be used to effectively assess seawater/brine impact and evaluate sites for placement of aquifer recharge basins or wells. Additionaly, the logs and profile samples may be useful in assessing the changes in groundwater geochemistry and extent of artificial recharge in unconsolidated aquifers.
Hexavalent Chromium Concentrations In Urban Runoff, Soil Moisture And Groundwater In The Los Angeles Basin
On-Farm Storage Reservoir Water as a Potential Water Source in Managed Aquifer Recharge in Eastern Arkansas
Deborah Leslie, PhD
Michael W. Bradley
Characterizing Groundwater and Surface-Water Interaction in the Mississippi Delta Using Hydrograph Separation
Development of Monthly Water Budget Estimates for the CONUS and Application to the Mississippi Alluvial Plain
Geophysical Surveys to Characterize Geologic Controls on Aquifer Recharge and Surface Water–Groundwater Exchange
In 2016-17, the USGS conducted several waterborne geophysical surveys to characterize the near-surface (<12 m) lithology that controls recharge to the MRVA aquifer and surface water-groundwater exchange at selected locations within the Mississippi Alluvial Plain (MAP). Two-dimensional vertical profiles of resistivity identified differences in geoelectrical properties of the streambed. High resistivity values are associated with coarse grained sediments and low values are indicative of fine grained materials. These resistivity-derived lithologies were then transformed using several techniques to inform the estimated hydraulic conductivity of the simulated streambed and refine the characterization of streamflow interactions in the MERAS groundwater-flow model.
These techniques have been applied to the existing Mississippi Embayment Regional Aquifer System (MERAS) model to guide data collection and model dataset construction for the proposed Mississippi Alluvial Plain (MAP) aquifer model. The focus of the MAP model is to forecast aquifer water levels and surface-water/groundwater (SW-GW) exchange under different climatic and water-use conditions. Forecasts of interest (FOIs) simulated by the MERAS model include water levels and SW-GW exchange along major surface-water features under conditions of less recharge and increased water use. Preliminary results from the uncertainty analysis indicate streambed conductance values may better constrain uncertainty in water-levels and streamflow, which can be used to guide data collection in the field. These results will be presented and discussed in the context of data collection and model data preparation.
After the Dam Comes Down: Groundwater-Stream Interactions & Water Quality of Restored and Unaltered Reaches in Ohio
At Kelsey Creek, interaction between the stream and shallow groundwater is evident. The stream tends to contribute shallow groundwater flow toward the western side of the site and north, parallel to the stream. The well closest to the stream shows variability in specific conductance, indicating bidirectional groundwater-stream exchange and all wells show rapid response to precipitation events. Hydraulic conductivity calculated using the Hvorslev method ranged 2.84x10-2 to 7.38x10-6 m/s and poorly correlate with the bulk sediments in Kelsey Creek.
Despite the wetland and groundwater-stream exchange in the unrestored Kelsey Creek, there is little change in stream water quality within the former reservoir site, similar to the restored Plum Creek site. This suggests that there is little water quality benefit to be gained from stream restoration at dam removal sites. Left unaltered, Kelsey Creek provides flood control and groundwater recharge in wetland areas.
Prashanth Khambhammettu, PE
This spreadsheet is currently being used at two operating units of a contaminated site.
In the first operating unit, water levels in an unconfined aquifer respond to pumping, and fluctuating stage in a neighboring river. Here, the spreadsheet is used to calculate efficiencies for 160 pump-and-treat wells. The second operating unit is inland and not impacted by the fluctuations in the river stage. However, the pumping wells in this operating unit are periodically cleaned resulting in sudden increases in well efficiencies. The spreadsheet tool was successfully able to model the water levels and efficiencies at these pumping wells after factoring in the maintenance history.
This spreadsheet tool can be used at other contaminated sites, provided, the local geology and hydrological processes are consistent with the underlying theoretical assumptions. The interactive and visual nature of the tool enables better communication with stakeholders and regulators.
Development of a New, Direct-Push-Based, Geophysical and Geochemical Approach for Groundwater Tracer Tests
Rob Rice, MS
Estimation of Spatial Distribution of Specific Yield by Using Hydraulic Tomography and Gravity Measurements
Larry McKay, Ph.D.
Here we present the hydrological, geochemical, and microbiological data and analyses in hand from the study site and the experimental well pair. This includes: (1) the magnitude and variability of hydraulic conductivity, hydraulic gradient, and effective porosity, (2) the potential for diffusive mass transport, (3) the temporal variability of specific discharge, (4) ethanol transformation to acetate and removal of nitrate and sulfate, (5) utilization/limitation of metal nutrients and/or co-factors, (6) microbial community structure (16S rRNA sequencing), and (7) microbial community function (GeoChip). Finally, we discuss the implications of the memory effort in terms of groundwater remediation with emphasis on the immobilization of redox sensitive metals and radionuclides.
Fraction of Young Water as an Indicator of Aquifer Vulnerability Along Two Regional Flow Paths in the Memphis Aquifer
Groundwater Impacts and a Complete Exposure Pathway: Vapor Intrusion (VI) Case Studies with Mitigation Options
Bryant Hoffer, LPG, CHMM
Various parameters of groundwater impacts affect the potential for a complete VI exposure pathway. These parameters include contaminant concentrations, depth to groundwater, lateral distance from groundwater impacts to occupied buildings, lithology of the unsaturated zone, and the individual characteristics of the Potential Contaminant (PC) at the Site.
There are several mitigation techniques currently available for sites with a complete/potentially complete VI exposure pathway. While numerous techniques are available for new construction (such as a vapor barrier, preemptive passive/active systems, and other new industry-specific products), the most common/effective strategy for existing buildings continues to be the installation/operation of Sub-Slab Depressurization Systems (SSDSs). These SSDSs introduce a pressure differential between the indoor air and sub-slab air. This pressure differential prevents the site PCs from entering the occupied building.
This poster will enable the reader to discover new sampling techniques, how to evaluate analytical data to determine the VI potential (with a focus on contaminant concentrations, depth to groundwater, and lithologic conditions), and learn about the common VI mitigation techniques. This poster will include case studies in which groundwater impacts have led to a potentially complete VI exposure pathway and the VI mitigation techniques used to effectively mitigate VI.
William Asquith, Ph.D., P.G.
Surface and Downhole Geophysics for Determination of Light Non-Aqueous Phase Liquid Migration in Faulted Dolomite
James Berndt, LPG
There are a number of approaches to estimating cost-to-closure, from simplistic “best guesses” to more sophisticated cost modeling techniques using Monte Carlo simulations. The challenge for accurately determining cost for closure comes down to the client risk tolerance, regulatory acceptance, available reserves, timeframes, and other variables. Cost modeling provides a more statistically rigorous analysis of all the potential costs and their likelihood of being incurred as the site proceeds to closure. The interpretation of the results provides a mathematically defensible estimate of the cost-to-closure. However, like with all models, it is only as good as the data used to build it. The more that is known about a site, the more confidence can be placed on the model results.
Using a Groundwater Model To Analyze Depletion Mapping For The Mississippi Alluvial Plain Groundwater Project
Steven Peterson, Peterson
For a depletion mapping analysis, a model of an area for a specified time period is first run under a baseline condition. Simulated groundwater flows to various simulated boundary conditions are recorded, such as for streams, groundwater levels, and wells. Next, a new well is added to one model cell, the model is rerun, groundwater flows to various boundaries are again recorded, and the results are compared with the baseline condition. Results are commonly expressed as the change in the boundary flow as a percentage of the new well’s flow. Subsequently, the new well is moved from one cell to the next, and each cell is mapped. Depletion maps have been used to establish water resources management boundaries in Nebraska for more than a decade. In addition, these maps reveal characteristics of the groundwater system of an area and of the simulation representing that system. Depletion maps generated for the MAP area demonstrate where the new wells caused increased groundwater level declines (loss of storage) or decreased groundwater discharge to streams. The depletion maps also show some characteristics and details of the groundwater model inputs, such as variations in the hydraulic conductivity assigned to simulated streams.
Hendrik Haitjema, Ph.D.
Neven Kresic, Ph.D., PG
Christian D. Langevin, Ph.D.
Juliette Woods, PhD
Due to the complicated interdependencies between processes moving water and salt within the floodplain, a series of inter-linked models have been developed to assist with management decisions. The models differ by hydrological domain, scale, and dimensionality. Together they simulate surface water, the unsaturated zone, and groundwater on regional, floodplain, and local scales. Outputs from regional models provide boundary conditions for floodplain models, which in turn provide inputs for the local scale models.
Two linked numerical groundwater models simulate floodplain processes in detail. One simulates 3D groundwater flow and solute transport across Pike Floodplain, while the other simulates density-dependent flow and transport in a cross-section through a riverine freshwater lens. The results are interpreted based on (i) ecohydrological requirements for key species of tree, and (ii) impacts on river salinity for downstream users. When combined, the models provide an integrated and interdisciplinary understanding of the hydrology and management of saline floodplains.
Hydrogeologic Evaluation of a Radial Collector Well as a Water Supply for the City of Manchester, New Hampshire
James Wieck, PG
Hydrogeologic evaluation included a step drawdown and two over 30-day constant rate withdrawal tests to evaluate groundwater capture, sustainable yield, and potential adverse impacts. Groundwater-surface water interactions and relative contributions to the withdrawal were evaluated. Constant rate tests were conducted during summer and winter conditions to evaluate effects of seasonal variations in viscosity on yield, capture, and groundwater-surface water interactions. Relative contributions of surface water and groundwater were also evaluated based on water quality including anion and cation data.
Hydraulic head data were collected from over 25 monitoring wells and selected residential water supply wells including wells screened in shallow and deep overburden and bedrock. Hydraulic head and water temperature data were also collected from the caisson and three multilevel monitoring locations constructed within the riverbed. Riverbed monitoring data were also used to identify the presence of restrictive layers within the riverbed.
The results of the withdrawal testing indicate a sustainable withdrawal rate of over 5,000 gallons per minute, with over eighty percent of the withdrawal from induced infiltration. The relative percentage of contributions to the well varies by up to 10 percent dependent upon temperature.
Understanding Surface Water and Groundwater Interactions at a Mining District Superfund Site near Silverton, CO
Rory Cowie, Ph.D.
A conceptual model of how black spruce trees impact the winter hydrology of peatlands will be presented. The importance of incorporating ecology into physically based model which simulate the interactions between surface water and groundwater will be discussed. Brief modeling examples using the USDA Simultaneous Heat and Water (SHAW) model will be used to demonstrate the differences in groundwater recharge between black spruce, lodgepole pine, and burnt forested ecosites, including the additional processes that are required to properly simulate black spruce peatlands. Finally the importance of ecohydrology will be emphasised by demonstracting how simulating groundwater infiltration under varying tree species will provide reclamation specialists an important tool for designing future peatlands.