NGWA Focus Conference on Gulf Coast Groundwater Issues: Alphabetical Content Listing
2012 McEllhiney Lecture: Life-Cycle Economic Analysis of Water Wells—Considerations for Design and Construction
Marvin F. Glotfelty, RG
Balancing Environmental Concerns with Energy Production
J. Winston Porter
Energy and Groundwater
Aquatic Toxicity Testing of Various Freshwater Drilling Additives
Shantel J. Stone, Scientist, Chemist
The leading suppliers of drilling fluid solutions in the industrial drilling markets have begun to focus on the environmental impact of their products throughout their life cycle, from production and packaging to use and disposal. In the first phase of responsible stewardship, companies focused on the down-hole activity of their products, primarily using the ANSI/NSF Standard 60 Drinking Water Treatment Chemicals protocol as the benchmark for responsible use. Today, interest is focused on the effect of drilling fluid products in the environment. Fluid additives for the non-oilfield drilling markets commonly consist of the industrial mineral bentonite, natural cellulosic material and derivatives (PAC), and commonly accepted water treatment polymers such as partially hydrolyzed polyacrylamides (PHPA). These fluid systems routinely achieve certification to ANSI Standard 60 and are generally regarded as the best available fluid technologies for drilling water wells, horizontal directional bores, mineral exploration wells, and geothermal heat loop drilling and grouting. The U.S. Fish and Wildlife Service, administered by the U.S. EPA, offers the opportunity to assess the toxicity of products potentially introduced to the various aquatic habitats Specifically, common drilling fluid products can be tested on two freshwater species designated by the USFWS, these species being the Daphnia pulex (a freshwater copepod) and Pimephales promelas (fathead minnow). Tests on these species generate LC50 and NOEC data which determine the lethal concentration with a 50 percent survival rate and the no observable effect concentration of the exposed species. Using the USFWS Rating Scale, products fall in a range between relatively harmless and super toxic. The data generated through USEPA-accepted toxicity testing can aid government regulatory agencies, as well as the end user of drilling fluid products, in assessing the environmentally responsible use of drilling fluid products.
Gas Well/Water Well Subsurface Contamination—Plan for Investigation
Rickard R. Railsback, Professional Geologist
With the advent of horizontal drilling and frac technologies which allow the commercial production of oil and gas from very low permeability rocks, onshore North America is undergoing a historic drilling boom. Environmental concerns accompany this boom. Is oil and gas drilling, fracking, and production endangering the nation’s groundwater supplies? Or, more specifically, has your client’s water well been contaminated or is your client’s gas well being blamed for that contamination? This presentation provides a brief description (understandable to the layman) of the tools and methods of investigation which will be useful for litigation support in cases involving contamination of a water well by the operations conducted at an oil or gas well. None of these technologies are new, though they may be unfamiliar to the layman and to environmental consultants who have no specific background in oil and gas drilling and production. One of the oil and gas industry’s essential tasks is to figure out how and where gas, oil, and water are migrating in the subsurface and around wellbores. Every investigation will be unique, and the tools and methods may be utilized in any sequence or combination that satisfies the client’s needs and objectives.
Groundwater Challenges in the Five-Parish Capital Area
Anthony Duplechin, CPG
Groundwater Quality and Coastal Restoration
Assessment of Brackish Water Resources in the Texas Gulf Coast
Steven C. Young, Ph.D., PG, PE
The presentation discusses results from several brackish water assessments that cover multiple counties in the Texas Gulf Coast. These assessments were performed for groundwater conservation districts to identify alternative water supplies in response to 2011 drought conditions. The presentation discusses approaches used to determine volumes of brackish water and depths to base of freshwater. These approaches include methods for calculating total dissolved solids (TDS) from geophysical logs. Where possible, concentrations of TDS calculated from geophysical logs were checked against the measurements of TDS at wells in close proximity of the geophysical log location. The presentation will also provide results from detailed analyses of changes in groundwater quality near several salt domes. For these salt domes, transacts of lithology and water quality were generated to illustrate the geohydrochemical complexities affecting the transport of groundwater solutions near salt domes.
Groundwater Quality and Coastal Restoration (cont.)
Development of an Updated Hydrostratigraphic Framework for the Texas Gulf Coast Aquifer System
Steven C. Young, Ph.D., PG, PE
The presentation discusses results from a multi-year project to update the hydrogeologic framework of the entire Texas Gulf Coast Aquifer System. The project was funded by the Texas Water Development Board to refine aquifer layer boundaries and layer properties to better capture hydrogeologic variability for improved simulation of groundwater availability. Approximately 1500 geophysical logs were analyzed to define stratigraphy and lithogy. The Gulf Coast Aquifer System consisted of the following nine geological formations: Beaumont, Willis, Lissie, Upper Goliad, Lower Goliad, Upper Lagarto, Middle Lagarto, Lower Lagarto, and Oakville. The mapping approach focused on identifying two key types of chronostratigraphic surfaces: erosional unconformities and marine flooding surfaces. The approach constrains the correlations in the fluvial section by: (1) incorporating microfaunal age control from offshore wells; (2) correlating marine flooding-event shales in the lower part of the Miocene to help establish general structure; (3) following marine shales (marker beds) as far landward as possible; and (4) tying key marker beds to outcrop formation boundaries using genetic and sequence stratigraphic concepts. Loop-tying within the cross section grid and reference to deeper mapped structure horizons from the professional literature provides added quality assurance. For each geologic formation, sand percent maps and depositional facies maps were generated.
Multiple Risks of Saltwater Intrusion to Drinking Water Supplies
Treavor H. Boyer, Ph.D.
Increased pumping of coastal aquifers and sea-level rise driven by climate change are expected to increase saltwater intrusion and subsequent contamination of fresh groundwater. The primary constituents of saltwater are sodium and chloride, which are typically regulated as secondary drinking water standards. Severe saltwater intrusion can increase the total dissolved solids of fresh groundwater such that reverse osmosis (RO) is needed to produce potable water. Retrofitting an existing water plant with RO can be a daunting challenge, especially for small systems. An overlooked aspect of saltwater intrusion is the co-transport of bromide with chloride. Although bromide is present in seawater at a much lower concentration than chloride, the increased bromide in groundwater can form bromine-containing disinfection byproducts (DBPs). Recent toxicological studies have shown that incorporation of bromide into DBPs makes these chemicals much more toxic. However, the risk of saltwater intrusion on the formation of more toxic DBPs has not been previously investigated. This presentation will highlight a recent case of severe saltwater intrusion at a coastal water system in Florida, and also discuss the likely effects of saltwater intrusion on DBP formation and toxicity.
Saltwater Monitoring In Situ and in Real Time with a New Geophysical Observatory
Marc Cherpion, Engineer
The downhole imaGeau observatory provides an opportunity to deploy a vertical string of sensors probing outward into the reservoir in order to study changes over time of pore fluid electrical conductivity (hence salinity) and/or saturation. This in-situ set-up is based on near-field and high resolution (in space and time) measurements of formation electrical resistivity in aquifers.
This paper presents results related to the salinization of a coastal aquifer exploited for the city of Hossegor (SW France). The subsurface measuring device downhole observatory has been located in the near vicinity of the city pumping station for domestic use, where increasing water salinity has been measured over the past 10 years. More than nine months of daily probing show not only seasonal changes but also a heterogeneous profile of pore fluid salinity, far from the first order model expected from the Ghyben-Herzberg gravity model. These more detailed data lead to more adequate aquifer management strategy in Hossegor. As a consequence, the technology deployed by imaGeau demonstrates to provide an answer to a series of hydrogeological issues such as saltwater intrusion in coastal aquifers, ASR monitoring, pollution studies whether in a petrochemical or dump site context, or else pollution prevention or remediation and CO2 geological storage integrity.
Understanding Saltwater Intrusion Processes Using Laboratory-Scale Physical Models
T. Prabhakar Clement, Ph.D.
The objective of this research is to develop a better fundamental scientific understanding for saltwater intrusion and the associated transport processes occurring in coastal groundwater aquifers. Results of two sets of laboratory experiments will be presented. The first set of experiments simulated the transient movement of salt wedge in a coastal aquifer. The experiments were completed in a laboratory-scale sand tank model fitted with boundary conditions that can deliver two types of groundwater fluxes—areal-recharge flux and regional flux. The experimental results were modeled using the numerical code SEAWAT. Based on the transient salt wedge migration data collected from the study, we hypothesized that when the fluxes are perturbed, it would require relatively less time for a salt wedge to recede from an aquifer when compared to the time required for the wedge to advance into the aquifer. This, rather counter intuitive, hypothesis implies that saltwater intrusion and receding processes are asymmetric and the time scales associated with these processes are different. We use a combination of laboratory and numerical experiments to test this hypothesis and use the resulting dataset to explain the reason for the difference in salt wedge intrusion and recession time scales. The experiments were simulated using a numerical model. The laboratory data and the model results were then used to develop better understanding of the transport processes occurring beneath a steady-state salt wedge.
Groundwater and Food Production
Rice Cultivation in the Mid-South: Challenges and Solutions
Michele Reba, Ph.D., PE
The US is the fourth largest exporter of rice worldwide. The Lower Mississippi River Valley accounts for approximately 70% of US rice and Arkansas accounts for 46% of US rice. Production of rice uses a significant amount of water, which ranges from 8 cm to 16 cm and is related to management practices. In Arkansas, approximately 80% of irrigation water comes from groundwater sources, predominantly from the alluvial aquifer. Groundwater decline in the alluvial aquifer has long been documented, with water use exceeding recharge. The need to reduce water use and increase efficiency has been documented. Research presented here describes initial findings from water savings related to conservation practices in rice production typical of the Mid-South. Initial findings are described from a study that compared common field grading practices in rice and how these practices influenced water use. Three additional studies related to water management in rice production are also described and include (1) on-farm water storage and the resulting surface water use for irrigation, (2) water savings resulting from flood management, specifically the date when the flood was drained and (3) a detailed groundwater study related to rice production.
Water Withdrawals for Aquaculture in the United States
John Lovelace
In 2005, an estimated 8.8 billion gallons of freshwater were withdrawn from groundwater and surface water sources for use at aquaculture operations in the United States. Aquaculture is the farming of organisms that live in water—such as finfish and shellfish—for food, restoration, conservation, or sport. Aquaculture production occurs under controlled feeding, sanitation, and harvesting procedures primarily in ponds, flow-through raceways, and, to a lesser extent, cages, net pens, and tanks. Aquaculture ponds, raceways, and tanks usually require the withdrawal or diversion of water from a ground or surface source. Water typically is added for maintenance of levels, oxygenation, temperature control, and flushing of wastes. Freshwater aquaculture operations using ponds, raceways, and tanks in the United States typically raise catfish, trout, bass, perch, tilapia, bait fish, sport fish, ornamental fish, crayfish, shrimp, alligators, and turtles. Estimates of water withdrawals for aquaculture are often based on aquaculture statistics, such as pond acreage or stocking rate, and a water-use coefficient or water-replacement rate.
Impacts of Deepwater Horizon Oil Spill On Beaches – An Analysis of the Past, Present, and Future Status of Alabama’s Beaches
Joel Hayworth
Keynote Speaker: Groundwater Management for the Gulf Coast—Daily Challenges and Successes
Tom Michel
NOAA Update on the Deepwater Horizon Oil Spill Clean-Up, Assessment, and Early Restoration Planning
Troy Baker
State Panel: Challenges and Successes
Marlon Cook
Water Supply Systems
Innovative Ion Exchange for Multi-Contaminant Treatment and Regeneration
Treavor H. Boyer, Ph.D.
Ion exchange is a robust process that can selectively remove a wide range of chemical contaminants, can perform effectively under changing water chemistry, can operate for several hours per day or continuously, and can be used in different reactor configurations and at different locations in a treatment train, therefore contributing to more sustainable water treatment. This research investigated combining anion exchange resin with cation exchange resin (hereafter combined ion exchange) for multi-contaminant removal. The combined ion exchange process used a single reactor for simultaneous removal of dissolved organic carbon (DOC) and hardness followed by a single reactor for simultaneous resin regeneration using sodium chloride (NaCl). The combined ion exchange process generates one liquid waste stream that contains predominantly NaCl, DOC, and hardness cations. DOC and hardness were selected as the focus of combined ion exchange because of their different chemistry and numerous problems related to water treatment. In addition, combined ion exchange can be applied to other combinations of contaminants including nitrate, perchlorate, sulfate, strontium, and barium. Two applications of combined ion exchange that are supported by the results of this research are: (1) as an alternative to coagulation and precipitative softening, and (2) as an intermediate treatment step between primary and secondary nanofiltration or reverse osmosis. This presentation will highlight results from the combined ion exchange research and also discuss alternative approaches to ion exchange regeneration that are more environmentally friendly.