This chapter provides a summary of presentations that describe the use of water in the process of hydraulic fracturing and the potential impact of shale gas extraction on water resources and human health. Health impact assessment (HIA) is discussed as a framework for assessing the impact of hydraulic fracturing on water. Studies to address public concerns regarding water contamination are also described.
Deborah L. Swackhamer, Ph.D., M.S.
Professor, Co-Director of the Water Resources Center
Division of Environmental Health Sciences
University of Minnesota School of Public Health
Deborah L. Swackhamer described her presentation as setting the stage for a discussion of hydraulic fracturing and its impact on water resources. Water contamination and the impact that hydraulic fracturing has on water resources is a growing concern to the public. Dr. Swackhamer’s presentation provides the context of the role water plays in hydraulic fracturing and the interaction between hydraulic fracturing and water resources. For this purpose it is important to start by understanding the water cycle in the fracturing process.
There are six important steps in the cycle as described below and seen in Figure 6-1.
- Water acquisition. Water needs to be collected from a major water site. It could be groundwater or surface water. The water then needs to be transported to the well site.
- Chemical mixing. Water needs to be mixed with chemicals necessary for the gas extraction. In most occasions it is done onsite or transported as the fluid to be injected.
- Well injection. The fluid is then injected into the well to fracture the shale and extract the gas. The fluid displaces the gas from the fissures of the rock to be collected.
- Flowback and produced water. Some of the fluid flows back after being injected into the well. It has been calculated that about 40 percent of the flowback is recovered but varies considerably from well to well. Produced water is that which is recovered with the gas extraction. The flowback and produced water have high concentrations of sand that were mixed during the injection, contaminants from the geological formation, chemical additives, and high dissolved solids.
- Storage tanks and pit. Most of the produced water is stored in tanks or in an open pit. The fluid is stored before it is treated or disposed. It has a high concentration of chemicals and particles.
- Water disposal. The water is transported to a treatment facility or disposed by deep well injection, or treated on site.
There is a potential problem for contamination in each one of the steps of the cycle. Dr. Swackhamer noted that the U.S. Environmental Protection Agency (EPA) is carrying out a study to specifically examine impact of hydraulic fracturing on drinking water resources (EPA, 2011). In addition to the fracturing water cycle, it is also important to consider the entire life cycle of water included in the processes of well construction, sand mining, water acquisition, and treatment and disposal during shale gas extraction, Dr. Swackhammer said.
She further explained that during well construction (see Figure 6-2) there are a variety of liquids and muds involved in the process. These are not comparable to the total usage of water during the life of the well, but can constitute approximately half a million gallons and need to be taken into account. The drilling of the well also involves the use of chemicals, so there is a potential for spillage and contamination. For the purpose of gas extraction, the well is drilled several thousand feet past aquifers and surface waters. The higher risk during this process is leakage from the casing. The cuttings, result of the drilling, should also be collected and properly disposed.
Sand mining raises a number of concerns that go beyond water. Sand mining requires considerable amounts of water for cleaning and sorting the sand, and in preparing it to be used as a proppant. In addition to the large quantities of water necessary, sand mining raises concerns related to transportation, air quality, workers health, and safety. In the last decade the number of wells has increased significantly making the demand for sand and water rise exponentially.
FIGURE 6-1 Water cycle of hydraulic fracturing.
SOURCE: EPA, 2011.
FIGURE 6-2 Initial well drilling and design of a well.
SOURCE: Laurie Barr. Reprinted with permission from Shutterstock.
It is estimated that between 2 and 4 million gallons of water are used in the lifetime of a shale gas extraction well. There are tens of thousands, almost approaching hundreds of thousands of wells being drilled and in production thus a significant amount of water is required in the activity of hydraulic fracturing. The main concern of local governments affected by hydraulic fracturing is the balance between water withdrawal and water consumption. It is important to keep in mind all activities and services provided by the water source. Dr. Swackhamer said that many water sources are being depleted and other sources will be exhausted if the withdrawal rate continues expected in the projection estimated for the Barnett Shale (see Figure 6-3). The graph in Figure 6-4 describes the increase in the number of active wells relative to the required amount of water required for shale gas extraction.
Dr. Swackhamer noted that the impacts of withdrawal of large quantities of water are many. Initially groundwater–surface–water interactions will be affected; excessive withdrawals of groundwater can result in reduced surface water flow or the drying of streams. Groundwater withdrawals can also have huge impacts on ecological functioning. The impact of water withdrawal can be short term or long term; for example, as water changes place underground, exchanges between aquifers can occur. It is imperative to understand the full water balance.
FIGURE 6-3 Postaudit analysis of water-use projections (solid lines) made in 2006 relative to actual water use (dots) through mid-2011 for the Barnett Shale (cumulative as of June 2011).
NOTE: This figure gives an estimate of the uncertainty associated with the analysis, which provides cumulative water use projections within less than a factor of 2 in the next 5-10 years. The assumption that current trends will still be valid beyond the 10-year horizon becomes weaker with increased uncertainty in the projections. Postaudits of long-term projections show that they often deviate from estimates because of unpredicted events, with unprecedented water-intensive shale-gas production being an example.
SOURCE: Nicot and Scanlon, 2012. Reprinted with permission. Copyright © 2012 American Chemical Society.
Water Treatment and Disposal
Dr. Swackhamer stated that the large consumption of water consequently has raised concerns in local health departments regarding water disposal and treatment. There are no studies that could provide a baseline of the particle and chemical concentrations in the water before and after treatment. Some localities use wastewater treatment plants to dispose of the water, but it has been said that not all wastewater treatment plants are capable of treating all chemicals found in the wastewater from fracturing. Wastewater treatment plants were not designed to treat for some of those contaminants. Until recently, Pennsylvania
FIGURE 6-4 Time evolution of Barnett Shale well count and water use per well percentiles.
SOURCE: Nicot and Scanlon, 2012. Reprinted with permission. Copyright © 2012 American Chemical Society.
is one of the states that allow wastewater treatment plants to collect the wastewater. This practice is of great concern because there have been a number of studies that demonstrate the fate of many of the contaminants is unknown. The current situation is that either they are not on the safe drinking water list or they are not on the list of what is being measured for wastewater treatment.
Many of the well sites also use a pit to collect their wastewater. Pits are used for temporary storage and to control contamination. Limited treatment is done in these pits that could accumulate high concentration of chemicals and residue from the fracturing activity. A major concern with the pits is a possible overflow or spill. Pits are exposed to the environment and are vulnerable to temperature and weather conditions. The common practice is to transport this water to a different location for disposal. Some wells have developed the capacity to reuse the water or recycle it and inject it in the well once again. After a certain period of time, somewhere between 5 and 7 years, companies plan to refracture wells to increase the productivity. In this there is a potential for cumulative impacts. There are no studies conducted on this practice. The contaminant levels are not known in any step of the cycle and each time the water is reused there is a higher degree of unknowns. The repressurization of the same well structures increases the risk for leaks to occur as well.
Concentrations of the chemicals in the fluid constitute approximately 1 to 2 percent of the total makeup of the fracturing fluid. While 1 or 2 percent of hydraulic fracturing fluid appears very small, Swackhamer noted that the minimum contaminant levels for some of these chemicals in drinking water are far below a total percentage point. Some of the chemicals used in hydraulic fracturing are tested on a scale of parts per million and even parts per billion, which is less than 0.0001 percent. Dr. Swackhamer stated that some of the chemicals used are known endocrine disruptors; these chemicals are measured on a scale of parts per trillion in the environment.
Dr. Swackhamer stressed that each of the steps of the water cycle in hydraulic fracturing constitutes a potential risk for water contamination and consequent impact on the environment. Not only with wells that are used for shale gas extraction, but in general all wells of similar construction present the most noticeable weaknesses in their physical structure. Most reports on contamination of aquifers pinpoint the cause of contamination as a leak of the well casing, pipes, or storage tanks. The integrity of the wells is critical in their operation and in the minimization of risk. Some of the wells are intended to be used several times, debilitating the structure and compromising operations. In terms of water use, the fluid is injected in the well at extremely high pressures under circumstances that are not completely known. Any engineering structure has a failure rate.
After the fluid has been injected and the fissures in the rock have been opened, there is not a clear indication of what happens to that water. There are estimates that the flowback or collected water is around 40 percent, but some locations have reported a 20 percent and even 80 percent flowback. Considering that a large percentage of the water remains in the ground, it is possible that it can migrate upward or continue to flow for long distances. The gases themselves can be pushed and potentially contaminate aquifers. Another consequence of not accounting for the total balance of injected water and flowback is the accumulation of chemicals in the ground. All the chemicals that are injected in the fluid could prove a more serious long-term contamination problem. Even though the injection is done several thousand feet underground, the composition of the soil is being altered and there is a disruption in the ecosystem, with unknown consequences.
As mentioned before, the treatment and disposal of the wastewater is the toughest challenge. It is a risk to dispose of it in existing wastewater treatment plants because some of the chemicals are not accounted for in the treatment process. There is also a high risk to use injection wells for disposal because the concentration of chemicals can affect other aquifers. There are suggestions for land use application of wastewater treatment
solids, but there are many unknowns with this practice and other areas could be exposed to the contamination.
Health Impact Assessment
HIAs, Dr. Swackhamer suggested, are an excellent framework for assessing system effects on human health. Different from a risk assessment, HIA is a more flexible framework that lends itself more appropriately for system-based issues. The difficulty in implementing HIA, is that in the third step, when an assessment is conducted, there are huge data gaps. The initial baseline data for tens of thousands of wells have not been collected. This is a large obstacle when trying to understand the impact on the communities, the environment, and health. Added to this, is lack of coordination or standardization of the data that are being reported. Further, there are many gray lines between the authorities (federal, state, local) that need to regulate hydraulic fracturing. It has been mentioned that the local government needs to become involved in the regulatory process. HIA includes an evaluation of alternatives and nothing has been developed in this area.
Dr. Swackhamer noted there is a call for industry and research institutions to collaborate especially around knowledge gaps. These areas include understanding the
- fate of the fracturing fluid;
- toxic burden for exposure analysis;
- impact of flowback water and produced water;
- effectiveness of contaminant removal and disposal technologies;
- cumulative impacts of refracturing;
- research alternatives to the current hydraulic fracturing practices;
- effective monitoring strategies to be implemented;
- fingerprints of chemicals and fracturing fluids;
- exposure modeling of populations, including vulnerable populations; and
- social impacts and outcomes.
There are many knowledge gaps and much research is needed, she said.
Dr. Swackhamer pointed out that there is a tremendous need for research around toxicity and risks associated with chemical constituents and fluids. A recent paper Colborn et al. (2011) identified more than 600 chemical constituents and fracturing fluids used in the process. Of these, the author could evaluate the literature for the potential health effects of 353 chemicals identified by Chemical Abstract Services (CAS) numbers (see Figure 6-5). The authors found that more than 75 percent of these chemicals can cause acute effects (see Table 6-1).
Dr. Swackhamer closed her presentation by acknowledging that there is much left to do to better understand the potential impacts of hydraulic fracturing on water resources.
FIGURE 6-5 Profile of possible health effects of chemicals with Chemical Abstract Service (CAS) numbers used in natural gas operations.
NOTE: The x-axis refers to the 12 possible health effect categories and the yaxis represents the percentage of the 353 chemicals with CAS numbers that are associated with each health effect category. The labels on the x-axis are as follows (from left to right): skin, eye, and sensory organ; respiratory; gastrointestinal and liver; brain and nervous system; immune; kidney; cardiovascular and blood; cancer; mutagenic; endocrine disruption; other; and ecological.
SOURCE: Colborn et al., 2011. Used with permission from Taylor & Francis.
TABLE 6-1 Percent of Chemicals in Fracturing Fluids Identified in Colborn et al. (2011) That Could Present Health Impacts
|% of Chemicals||Health Impacts|
|>75||Could affect skin, eyes, other sensory organs, and respiratory and gastrointestinal systems|
|40–50||Could affect brain and nervous systems, immune system, cardiovascular systems, kidneys|
|37||Could affect endocrine system|
|25||Could cause cancer and mutations|
SOURCE: Swackhamer, 2012.
Robert B. Jackson, Ph.D., M.S.
Nicholas Chair of Global Environmental Change
Nicholas School of the Environment
Professor, Department of Biology
Robert Jackson began the presentation by acknowledging his collaborator, Avner Vengosh at Duke University. He stated that the goal of the work he was about to describe was conducted to help answer many of the questions about the use of water in hydraulic fracturing activities. The challenge is not only to collect the data, but more importantly to know which kind of information needs to be produced.
Public concerns about the role of water in hydraulic fracturing have helped to shape the study. The public has voiced many concerns: What is the drinking water contamination potential? What is the amount of water required for the operations? How is the wastewater going to be disposed? What is the concentration of polluting chemicals? These are important questions that need answers.
Dr. Jackson explained the possible water interactions in the hydraulic fracturing process. There are several operations occurring at the surface level, there is injection of fluid far beneath aquifers, and there is the interaction with produced water.1 Water interactions can occur at different levels. There is natural water or formation water2 deep underground which often contains high concentrations of naturally occurring chemicals and contaminants and they typically are very salty. In some areas of the country, such as the Marcellus Shale, formation water can contain naturally occurring radioactive materials (NORMs). In hydraulic fracturing, some of the formation waters can flow back to the surface as part of produced waters. Those waters should be kept from contaminating the surface groundwater where drinking water is obtained.
Fracturing fluids used in the hydraulic fracturing process interact with water sources. These fluids represent a small component of water, about 1 percent. But the average operation uses 3 million or 4 million gallons of water, or 30 million pounds, or about 300,000 pounds of fracturing fluid chemicals. Most of those chemicals are harmless such as salt, and citric acid. However, some of them are not as harmless: benzene, naphthalene, and diesel, which are potential carcinogens; toluene and hydrochloric acid and many other hazardous air pollutants; and many
1 “Produced water” is used in the oil industry to describe water that is produced when oil and gas are extracted from the ground.
2 Formation water is a natural water layer underlying oil and gas reservoirs.
other chemicals, including 2-butoxyethanol, ethylene glycol, and lead (U.S. House of Representatives, 2011). A 2011 report on constituents of fracturing fluids identified 2,500 fracturing products containing 750 chemicals and other components. The presence of a chemical in the field does not mean that it is a problem, Dr. Jackson explained, but it is important to know the concentration, how it got there, and its long-term impact in the environment.
Dr. Jackson paused to highlight a novel approach to chemicals and the hydraulic fracturing process. The chief executive officer of an unconventional gas exploration company in Northern Ireland promulgated a no chemicals pledge for their hydraulic fracturing process (see Box 6-1). Such an approach has not been taken in the United States.
Management of Produced Water
Dr. Jackson turned to discuss produced waters which are primarily a combination of naturally occurring deep formation waters and fracturing fluids. In the Marcellus Shale formation and many other locations, formation waters are very salty, and they may have high bromide concentrations. Bromide can be an issue if it interacts with other chemicals; for example, it can enhance disinfection by-products (e.g., trihalomethanes) upon chlorination of downstream potable water. There are also high concentrations of other toxic elements, including barium, arsenic, selenium, and lead. Hydrocarbon residuals in produced waters, such as oil and organics, can come from both the natural formations and the fluids themselves.
Dr. Jackson reiterated that questions the public would like answers to are the long-term ecological effects and health risks associated with produced water disposal. He described the five main practices used by industry to dispose and manage produced waters. Deep injection for underground disposal is a common practice. The potential problem with deep injection is well leakage or contamination of surrounding aquifers, but there is a long history of this practice, Dr. Jackson stated.
No Chemicals Pledge
The Chief Executive of Tamboran, Richard Moorman, came out with a no chemicals pledge for their hydraulic fracturing in Ireland. He said: “Tamboran will not utilize any chemicals in its hydraulic fracturing process in Northern Ireland, and we will be bringing together the best technologies developed worldwide into this one project to ensure the safe and responsible development of a tremendous resource.”
SOURCE: Moorman, 2010.
Another disposal strategy is spraying produced water on land. This strategy is problematic for a number of reasons. As noted earlier, the salinity of produced water is high. The potential for long-term damage of the soil is also high. Further, runoff from sprayed water could contaminate surrounding surface water or percolate into aquifers. Dr. Jackson opined that from every point of view, this strategy is problematic.
The delivery of produced waters to a municipal wastewater treatment plant is another option. Some states have established this practice. It is not recommended to dispose of produced waters in municipal wastewater treatment plants, Dr. Jackson said. These plants do not have the capacity to treat many of the chemicals found in produced waters. Further, some plants do not have the capacity to monitor some of the contaminants. Wastewater treatment plants may then dispose of the treated water in adjacent streams or rivers; the potential for contamination of those water sources is high. The chemicals could accumulate in sediments and cause a higher environmental impact. Municipalities that are located downstream will use the surface water, and those chemicals could end in their drinking water. Figure 6-6 describes the downstream flow of chlorine from the outflow area of a treatment facility. Different concentrations of bromide and trace metals as well as radionuclides in river sediments were found at distances from 300 to 500 meters downstream.
FIGURE 6-6 Downstream flow of chlorine from the outflow area of a treatment facility.
SOURCE: Jackson, 2012.
Another potential disposal strategy is to deliver produced water to a commercial wastewater treatment facility. It is a viable alternative, although these treatment plants do not always have the capacity to receive large volumes of produced water. Lack of familiarity with all the chemicals to be treated may be another limitation of this strategy.
Jackson described the practice of recycling or reusing produced water in a future fracturing job with or without treatment. This practice reduces the amount of water needed to be acquired and also reduces the expense of wastewater treatment. The challenge of reusing the water is monitoring the concentrations of chemicals in the produced water. Every time produced water is reused and collected, it can become more difficult to treat, and the contaminant levels can also be exceeded. Nonetheless, Dr. Jackson said that this practice is a positive development and the industry deserves credit for implementing it.
Quality of the Groundwater Naturally
Another question that Dr. Jackson attempted to answer is what is in shallow groundwater naturally? Jackson described a study that had as an objective to understand the quality of the groundwater in this region of the north of Pennsylvania. Figure 6-7 shows about 400 observations that have been collected over time in the area. The type of water was grouped into four types: two with low salinity levels and two with high salinity
FIGURE 6-7 Occurrence of saline groundwater naturally enriched in barium and other elements in shallow aquifers.
SOURCE: Warner et al., 2012.
levels. More specifically, there is special interest in one type denominated Type D. It is one of the two high in salinity plus it has high bromine-tochlorine ratio. This is important because those waters are the ones that look Marcellus-like and suggest natural connections to Marcellus-like brines through natural flow pass. It is not associated with drilling; it occurs naturally. The areas designated as Type D should be monitored for potential contamination.
Surface drinking water was also sampled and tested for dissolved gas concentration, salts, and NORMs. The results were published in Osborn et al. (2011) (see Figure 6-8). This is the first paper to look at the relationship between water quality and distance to gas wells. Most of the contaminants were not found. In the subset that was looked at initially, there was no evidence for the brines found naturally in deep formation waters or evidence for NORMs in residents’ drinking water. What was found in some drinking water from wells were much higher dissolved gas concentrations of methane and ethane particularly. Within about 1 kilometer of the well, there is the likelihood of seeing very high concentrations of methane. Some wells fell within or above limits set by the Department of the Interior for hazard mitigation; immediate action is required on these wells because they pose a health hazard. In those cases, it is important to focus on the well integrity. According to historical records, 10 or 20 percent of the time, faulty cement or corrosion in the casing is present. Most cause of contamination or spillage is such a compromised well structure.
FIGURE 6-8 No evidence of brines or fracturing fluids was present, but methane concentrations in drinking water were higher near gas wells. The gray band is the Department of the Interior hazard mitigation recommendation.
SOURCE: Osborn et al., 2011.
The results of the study suggest that the liability distance be increased to 3,000 feet (see Figure 6-8). At that time, presumptive liability distance in Pennsylvania was 1,000 feet. Governor Corbett recently signed a bill (Pennsylvania Office of the Governor, 2012) stating that the new presumptive liability distance is 2,500 feet. The presumptive liability says that if a homeowner has a problem with his or her water, now within a year of drilling, the operator is presumed guilty unless they can show otherwise.
Other recommendations made in the study address disclosure of information to enhance environmental monitoring. For example, companies should release the isotopic values of the methane or ethane from each producing well (C-13 and the deuterium values), which could help rule out cases that could be perceived as contamination. Such testing would allow comparison of gas coming out of the ground and the gas that is in homeowners’ wells; these data could help researchers identify sources of stray gas. Public disclosure and making information available in general would be a positive development. It could show transparency and willingness of industry to address public concerns.
As a last recommendation, the paper proposed studies on the health effects of chronic, low-level exposure to methane in people and animals (Jackson et al., 2011). There is little information in this area but it would be important for health care professionals to examine the issue.
Dr. Jackson acknowledged that while the session was focused on water, he wanted to briefly discuss natural gas and air. Dr. Jackson highlighted work done in collaboration with Nathan Philips at Boston University to map natural gas leaks across the city of Boston. The study found 3,300 gas leaks across the city (Phillips et al., 2013). A highresolution methane imager is used to detect gas leaks, and samples are taken and analyzed in the laboratory for isotopic composition. The isotopic composition allows distinguishing among landfill gas, sewer gas, and natural gas coming from a pipeline. Figure 6-9 shows 3,300 gas leaks across the city. This type of information can help to reduce the environmental footprint of some of these processes.
Returning to the topic of water, Dr. Jackson briefly noted the situation in Pavillion, Wyoming. As mentioned earlier, one of the biggest public concerns is organics from fracturing fluids leaking into drinking water. Studies conducted by the EPA reported findings of dissolved gases and chemicals associated with hydraulic fracturing in the groundwater in Pavillion. Hydraulic fracturing there occurred as shallowly as about 1,000–1,500 feet underground; however, people may be obtaining their drinking water at 750 feet underground, sometimes in the same formation, this is not a good idea, Dr. Jackson said. Further test by the U.S. Geological Survey will confirm or refute contaminations.
In concluding his remarks, Dr. Jackson identified a number of positive developments on the water front:
- industry-driven initiative to recycle and reuse water for fracturing the next well;
- greater disclosure of the chemicals in fracturing fluids (except those that are trade secret), which is being driven by state laws; and
- interest in green completion and elimination of open wastewater pits.
These types of practices, if pushed, would benefit all, he said.
FIGURE 6-9 Emissions to the atmosphere: Methane leaks for the Boston metroplex.
NOTE: ppm = parts per million.
SOURCE: Phillips et al., 2013. Reprinted from Environmental Pollution with permission from Elsevier. Copyright © 2013.
Jennifer Orme-Zavaleta, Ph.D.
Director, National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Jennifer Orme-Zavaleta opened her remarks by saying that fracturing is not a new practice and the concept has been around for awhile. It has become more popular in the last decade because it has become part of the country’s energy security and energy independence strategy. As the technologies evolve, the possibility of acquiring more of the shale gas deposits has become more viable. To clarify many of the concerns from the public and to develop a standardized practice for industry, Congress asked the EPA to study the impact of hydraulic fracturing on drinking water resources.3
Dr. Orme-Zavaleta explained that the objective of the study was specifically to assess whether hydraulic fracturing can affect drinking water resources and to better understand the factors that affect the severity and frequency of these impacts. The study focuses on surface and subsurface practices of hydraulic fracturing. The greatest attention was given to the well structure. Considering that most failures and accidents occur because of damaged or deteriorated well structure, this aspect needs to be deeply studied. She further discussed the research approach. There were five different research components to the study.
The first component is data gathering and analysis of available data. Data describe previous incidences of accidents at particular sites, their frequency, and how they were handled. The data gathered also include operating procedures from each one of the companies, the technology and types of materials they use, and the components of the fracturing fluid that they are using.
The second research component is based on case studies. The study identified several retrospective case studies as well as two prospective case studies. The purpose of looking back was to determine if drinking
3 “The conferees urge the Agency to carry out a study on the relationship between hydraulic fracturing and drinking water, using a credible approach that relies on the best available science, as well as independent sources of information” (emphasis added). Department of the Interior, Environment, and Related Agencies Appropriations Act, 2010, H. Rep. 111-316. http://thomas.loc.gov/cgi-bin/cpquery/?&sid=cp111alJsu&r_n=hr316.111&dbname=cp111&&sel=TOC_351721& (accessed May 30, 2013).
water sources were previously affected and what factors were involved in those cases of contamination. The advantage of following the two prospective cases is that there is an opportunity to establish a prefracturing and predrilling baseline and to compare those baselines with the conditions afterward.
The third research component is failure scenario evaluation. This approach allows a comprehensive assessment and understanding of the impacts. It is important to look at issues such as water quantity, including water withdrawal, transportation, refracturing, and treatment and disposal of wastewater. She said that the EPA is not generally thought of as being interested in water quantity issues but she emphasized that it is not possible to look at water quality, an area that the EPA is known for, without considering quantity; these two characteristics are interrelated.
The fourth research component is laboratory studies. The evidence from laboratory studies can contribute to an understanding of the most efficient and safest wastewater treatment practices. Laboratory studies can be used to understand the interaction of hydraulic fracturing fluids and shale formations. There are different types of hydraulic fracturing fluids and each of the fluids interacts with the different types of shale formations. That these fluids are used with different components and at different concentrations must also be considered. Laboratory studies can also help assess the effectiveness of wastewater treatment. Laboratory studies can also help the treatment process. Processes must be able to effectively handle the types of contaminants that are in flowback and produced waters. If they are not effective, what would be the potential impact for drinking water resources? Other areas of concern are the analytical methods used and whether they are sufficient to measure the contaminants at the concentrations that are of interest. These issues are best determined and subject to experiments within the controlled laboratory environment.
The fifth research component is toxicity assessment. This component fundamental to understanding the interaction and impact of each of the chemicals used in hydraulic fracturing fluid (see Box 6-2). Toxicity assessments are focused on hydraulic fluids, wastewater, and naturally occurring substances that enter wastewater. The contaminants are being assessed for their chemical, physical, and toxicological properties. For some of the chemicals there is a lack of information; thus, an additional step of assessing the properties using quantitative structure–activity relationships or other computational types of approaches will be taken. This will help screen those chemicals and prioritize them for toxicity studies.
Studying the impact of hydraulic fracturing on drinking water is complicated, Orme-Zavaleta noted. To begin, the practice of hydraulic fracturing is not standardized. Every company is different. Each company’s formulation of fluids is different. Different conditions require different types of fluids and mixtures, which makes comparisons complicated. Studies in this area must grapple with this issue.
Component Materials Used in Hydraulic Fracturing Fluids
Acids; Acid inhibitor
A complete list of chemicals as of November 2011 is available at http://www.epa.gov/hfstudy (accessed May 30, 2013).
Dr. Orme-Zavaleta also noted that the EPA does not have general regulatory authority over hydraulic fracturing fluids. Hydraulic fracturing is only regulated under the Safe Drinking Water Act if diesel fuel is used. When diesel fuel is used, a permit is required through the Underground Injection Control Program.4 As was stated earlier, there is cause for concern if drinking water is contaminated with diesel because of human health effects. Diesel fuels contain benzene, toluene, ethylbenezenes, and xylenes, which are hazardous to health.
One of the study objectives was to determine specific indicators that would help the EPA track the chemicals in fluid and produced waters. These indicators can help determine standards for the industry such as frequency of use, toxicity of the chemicals, and improvement of the monitoring and detection methods.
In concluding her remarks, Dr. Orme-Zavaleta said that the biggest concern from the public and local authorities is the lack of understanding about whether hydraulic fracturing can impact drinking water sources and, consequently, human health. The objective of studies such as this one from the EPA, is to gather and analyze the available data, which can then be used to make informed decisions about the practice. It is known that many types of chemicals are mixed with water and subsequently injected in the ground. It is the responsibility of the EPA to know the toxicity and impact of the chemicals being used. Although the study will not conduct quantitative risk assessments, it will help understand the
4 Water: Underground Injection Control, Regulation, 40 CFR Parts 144–148. Available: http://water.epa.gov/type/groundwater/uic/regulations.cfm (accessed May 30, 2013).
consequences of possible human exposure to the fracturing fluid, she said.
An important consideration of the study is to keep the public and industry informed of the processes under way. The information collected and available reports can be found through the EPA website.5 The final report is due in 2014.
To begin the discussion, Bernard Goldstein asked Dr. Orme-Zavaleta whether the scenario component of the study she described would include an analysis of chemical mixtures. Dr. Orme-Zavaleta responded that the study was currently focused on individual compounds but that the case study component of the study will eventually allow for the examination of chemical mixtures. Christopher Portier asked Dr. Orme-Zavaleta if the study had preliminary results on endocrine disruptors in the chemicals identified in the study. Dr. Orme-Zavaleta responded that the data collection component of the study was currently identifying the chemical, physical, and toxicological properties of water quality components but was not yet at the stage of identifying endocrine disruptors. She highlighted that the health end points the study would focus on included carcinogenicity as well as developmental and reproductive end points, which would include, endocrine disruptors.
Colborn, T., C. Kwiatkowski, K. Schultz, and M. Bachran. 2011. Natural gas operations from a public health perspective. Human and Ecological Risk Assessment: An International Journal 17:1039–1056.
EPA (U.S. Environmental Protection Agency). 2011. Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources, EPA/600/R-11/122. http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/upload/hf_study_plan_110211_final_508.pdf (accessed May 30, 2013).
Jackson, R. B. 2012. Hydraulic fracturing, water resources, and human health. PowerPoint presentation at the Institute of Medicine workshop on the Health Impact Assessment of New Energy Sources: Shale Gas Extraction, Washington, DC.
Jackson, R. B., B. Rainey Pearson, S. G. Osborn, N. R. Warner, and A. Vengosh. 2011. Research and policy recommendations for hydraulic fracturing and shale gas extractions. Durham, NC: Center on Global Change, Duke University.
Moorman, R. 2010. Tamboran. Our commitment to the people of Ireland. http://www.tamboran.com/operations/ireland-uk/our-commitment (accessed May 30, 2013).
Nicot, J. P., and B. Scanlon. 2012. Time evolution of Barnett Shale well count and water use per well percentiles. Environmental Science & Technology 46:3580–3586.
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