Ohio Groundwater Forum: Protecting and Managing Groundwater for the Future : Alphabetical Content Listing

Data Collection, Analysis, and Utilization

Numerical Groundwater Flow Modeling of a Northern Appalachian Coal Basin Bedrock Valley Exhibiting Stress-Relief Fractures

Andrew Ashton
Permitting of fly ash impoundments requires a solid understanding of the groundwater system, both the physical properties governing flow and the natural variability of the groundwater geochemistry. At the site in this case study, sandstones of the Monongahela, Conemaugh, and Allegheny formations form the major water-bearing aquifers with thick shale sequences forming intervening aquitards. Borehole geophysics conducted at the site indicates that fracture flow plays a dominant role in the movement of groundwater. The fly ash ponds in this study are located in a high-relief, upland setting and stress-relief fracturing is expected to play an important role near the valley sides. Groundwater monitoring conducted at the site during the last 28 years, including stable isotope analysis, has provided considerable data on the flow system. As part of a recent permit application to increase the capacity of the existing fly ash pond, we developed a 20-square-mile, 10-layer, steady-state groundwater flow model using MODFLOW-NWT, a stand-alone version of MODFLOW 2005. Pre-processing of the model, including development of the geological conceptual model, was conducted in GIS to increase the efficiency of the modeling process. The challenge at the site is to distinguish constituents naturally present in groundwater and those potentially due to leaching from the fly ash reservoirs. Impacts from extensive coal mining and petroleum exploration over the last 100 years further complicate the interpretation of groundwater geochemistry. Particle tracks were generated from the numeric modeling simulations and the results helped to verify the groundwater flow-paths as indicated by groundwater contours and geochemical data. Ultimately the model was a key component in the permit, allowing an understanding of future conditions and guiding development of future monitoring plans.

Hydraulic Fracturing/Shale Gas Development and Groundwater Protection

Alternative Methods to RSK 175 for the Analysis of Dissolved Gases in Drinking Water

Nathan Valentine
With the growing price of oil, many alternative energy sources are being explored. Natural gas prices are actually decreasing, in large part to the use of hydraulic fracturing in areas like the Marcellus Shale in Pennsylvania. Due to increased concern over the hydraulic fracturing process and the release of methane and other chemicals into the local drinking water, a need has developed for fast and accurate analysis of methane in water. This study will evaluate methods developed for the determination of methane, ethane, ethene, and propane in water using a purge-and-trap concentrator and automated headspace analysis with GC/FID. Calibration curves, method detection limits, and carryover data will be presented, and comparisons between the methods will be made.

Real-Time Monitoring System for Evaluating Long-Term Variability in Methane in Domestic Water Wells in Pennsylvania

Richard Wardrop, PG
Naturally occurring methane is present in many domestic groundwater wells in Pennsylvania.  A significant amount of data is currently being collected by the oil and gas industry as a result of sampling efforts and investigations, much of which is from pre-drilling (“baseline”) sampling conducted prior to any drilling activity. However, gaps remain in understanding and quantifying the natural temporal variation in methane concentrations in these wells. This is of significant importance in assessing claims of gas migration when there is nearby anthropogenic activity. This presentation will discuss a research project developed and implemented to gain an understanding of the long-term variability of methane in domestic water wells.  

Real-time remote monitoring and data trend analyses are being utilized to understand natural dissolved methane fluctuations in groundwater and correlations between methane headspace concentration in the well annulus and other physical and chemical parameters, which could correlate to changes in headspace concentration. Significant efforts were made to select, evaluate, and prepare the wells for the study including borehole geophysics, well equipment upgrades, and installation of water-treatment systems. Descriptions of the customized real-time remote monitoring equipment, array of well headspace and water-quality sensors utilized, and equipment setup will be presented, as well as the associated challenges and logistics. Barometric pressure, water use, water quality, well recharge, water-level fluctuations, and pump cycling are examples of the variables monitored. 

The results from the study will be presented, including discussion of well construction, geologic settings, water quality, initial trends and findings, and real-time display of data. The usefulness of the data and the accuracy/precision of sensors will be discussed. The long-term study will provide further information to better understand the occurrence and potential causes of methane fluctuations in groundwater and associated water well quality issues in northeast Pennsylvania.

Hydraulic Fracturing/Shale Gas Development and Groundwater Protection (cont.)

Groundwater Protection Within Shale Gas Areas: Examples from Pennsylvania Source Water Protection Technical Assistance Program

Alfred C. Guiseppe, PG
The current natural gas development boom in eastern Ohio has raised serious source water protection concerns among drinking water suppliers.  Over the past five years, Pennsylvania has faced an unprecedented expansion in shale gas drilling activities. To help community water systems develop source water protection plans, the Pennsylvania Department of Environmental Protection initiated the Source Water Protection Technical Assistance Program in 2007. The SSM Group Inc., of Reading, Pennsylvania, was contracted to provide the technical assistance to qualifying community water systems across the commonwealth. In the first five years of the program, SSM provided approved Source Water Protection Plans to 91 water systems, 39 of which reside within the Marcellus Shale “Fairway.”  Approaches and strategies implemented to protect drinking water supplies vary greatly throughout the region based on the assessment of risk posed by current, and future, activities within the water contribution areas. One of the most effective protection strategies involves the utilization of the hydrologic and groundwater computer models that are used to predict water flow that contributes to supply sources. In addition to being used to delineate recharge areas and protection zones, the groundwater computer models are used to investigate potential sources of stray gas, assess the risk of gas well drilling activities, and predict migration paths of pipeline breaches and other surface derived contamination sources.

Water systems face many threats to the water quality of their supply. Taking a proactive approach to source water protection lessens the risk of a catastrophic loss of a water supply. The examples provided in this presentation illustrate the advantages to utilizing groundwater computer models for source water protection measures.

Relationship between pH and Dissolved Methane Concentrations in Groundwater from Water Wells in Northeastern Pennsylvania

Nancy Pees Coleman, Ph.D.
Dissolved methane has been found in the groundwater from domestic water wells in many locations in northeastern Pennsylvania. The dissolved methane can be naturally occurring thermogenic, diagnetic, or biogenic, or sourced from anthropogenic activities. The presence of dissolved methane has been reported to be associated with changes in geochemistry including increases in pH. The relationship between temporal changes in the dissolved methane concentrations and the pH level were examined within individual domestic water wells. 

Dissolved methane has been found to be variable in domestic water wells. These variations are attributed to several factors, including changes in atmospheric conditions, physical disturbances, anthropogenic sources, the action of water well pumping, etc. Sampling and laboratory analysis for dissolved methane requires specialized sampling and analytical techniques. Identification of a surrogate parameter that is amendable to direct measurement in the field, such as pH, would be highly desirable for use in screening and identification of domestic water wells requiring further evaluation. It has been suggested that changes in pH may be an appropriate surrogate. 

Comprehensive and frequent monitoring data for dissolved methane, pH, and other water-quality parameters were available for four groups of domestic water wells: (1) wells with no known impact from oil and natural gas drilling activities (approximately 28 wells), (2) wells with known perturbation of natural gas from a natural gas production well, (3) domestic wells sampled prior to the initiation of oil and natural gas drilling activity (predrill samples), and (4) wells under investigation for complaints related to the presence of increased levels of dissolved methane (18 wells). Analytical data for these domestic water wells were evaluated for short-term temporal variability in dissolved methane and pH. The data were evaluated to determine if any consistent predictive relationship exists between dissolved methane and pH and other water-quality parameters in groundwater in northeastern Pennsylvania.   

Shale Gas Drilling and Groundwater Quality in Northern Pennsylvania

Paul Wendel, Ph.D.
This study examines water quality related to shale gas extraction in Tioga County, Pennsylvania by horizontal drilling and slick-water hydraulic fracturing.  In Phase I (October 2010 through May 2011), 57 private drinking water wells less than 500 m from the nearest gas drill site (mean distance = 291 m) and 41 private drinking water wells greater than 500 m from the nearest gas drill site (mean distance = 1,965 m) were selected by a randomization procedure, sampled, and tested for pH, conductivity, barium concentration, and strontium concentration.  Barium and strontium were chosen as analytes because numerous studies found high concentrations of barium and strontium in flow-back fluids following hydraulic fracturing. Statistical tests revealed no statistically significant difference between water samples taken less than 500 m from the nearest gas drill site and water samples taken more than 500 m from the nearest gas drill site, and, furthermore, no statistically significant correlation was found between distance to the nearest drill site and analyte concentrations. In Phase II, each of the 98 water wells are being resampled and analyzed (October 2012 through May 2013). Since 2010-2011, gas wells have been drilled less than 500 m from each of the 41 wells originally greater than 500 m from the nearest drill site, enabling predrill/postdrill comparison for these sites in addition to longitudinal comparison of water samples taken from sites originally less than 500 m from the nearest gas well. Data and findings from both Phase I and Phase II will be presented.

The Occurrence of Methane in Shallow Groundwater from Extensive PreDrill Sampling

John Boulanger, PG
On behalf of a major shale gas operator, sampling of over 20,000 water wells has been conducted from 2009 to the present, from shale-gas development areas across Pennsylvania, Ohio, and West Virginia. Sampling was conducted prior to Marcellus/Utica Shale-related exploration, drilling, and production activities in the vicinity of these water wells. The predrill samples have been analyzed for methane, ethane, and propane, as well as many inorganic parameters.

This presentation will explore the occurrence and distribution of methane in groundwater prior to unconventional gas development. GIS-based mapping and statistics will be used to evaluate the geographic distribution and relationship to bedrock geology. The relationships between methane and other parameters can also help explain methane occurrence, including parameters such as ethane and propane, alkalinity, TDS and major ions, barium, etc. 

Better understanding of methane in shallow groundwater will lead to better decision-making when evaluating potential impacts of shale gas development on water supplies and stray gas occurrence.

Wellfield Sustainability and Water Quality

How Well Development and Redevelopment Affects Long-Term Well Performance History

Stuart A. Smith, CGWP
A common pattern for long-term well performance histories in glacial-fluvial aquifers is a years-long decline until operating the well becomes uneconomical. One factor that managers can control is well development. Many water wells are not completely developed in the first place, so wells are impaired from the start. Also, when wells are cleaned, the redevelopment is incomplete, so results are not as good as they could be. This talk will review long-term well performance patterns in Ohio Valley public water supply wellfields and circumstances that contribute to declining performance and lack of response to rehabilitation efforts. The reward is delay of expensive work and lower pumping energy cost.

Hydrogeological Investigation of the Carbonate Bedrock Aquifer to Evaluate Impact High-Yielding Wells, Ottawa County, Ohio

Curtis J. Coe, CPG, PG
A groundwater investigation of the carbonate bedrock aquifer was initiated in May 2011 by the ODNR Division of Soil and Water Resources at the request of local homeowners in Harris Township, Ottawa County, Ohio. The purpose of the investigation was to evaluate the impact of high-yielding irrigation wells on ground water levels in the nearby domestic water supply wells.

Previous work completed in this area confirms that the carbonate bedrock aquifer of northwestern Ohio contains a number of flow zones. The well completion diagram for the Luckey homestead farm well shows the extent to which the flow zones occur in the subsurface. Drilling data shows that the carbonate bedrock aquifer is anisotropic and heterogeneous in its configuration. This gives rise to a number of concerns that need to be considered before long-term pumping rates can be accurately calculated and the data used to design water supply systems.

Pumping test data shows that the transmissivity of the aquifer is not uniform throughout the aquifer. It can vary both in the vertical and horizontal directions, and may vary over short distances within the carbonate bedrock aquifer when there are significant variations in permeability as well as fracturing. This helps to explain major changes in yield over short distances in both the vertical and horizontal directions.

Field data obtained for this project shows that the pumping of the high-yielding water wells can have an impact on the local water supply wells. The degree of impact depends on the location of the water well relative to the pumping center and the pumping rate. It also depends on the flow zone from which the water well produces. A deeper high-yielding well can impact water supply wells completed in the upper flow zone in the carbonate bedrock aquifer.

Wellfield Sustainability and Water Quality (cont.)

Effective Water Well Rehabilitation – Complying with Revised Total Coliform Rule and Controlling Iron Bacteria

Neil Mansuy
Lost capacity and associated water quality problems, including total coliform will be described and methods of rehabilitation discussed. Complying with the Revised Total Coliform Rule (RTCR) 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. With ever-increasing energy costs, there is increasing pressure to look at ways to reduce these costs. New, effective, and economical methods of well maintenance will be presented with case studies of cost savings. Case studies will also be presented on solving difficult total coliform issues on wells.