Report says fracking can impact water
EPA study recommends focusing attention on situations where the risk of drinking water contamination is highest; cites data gaps
In response to concerns expressed by Congress, the Environmental Protection Agency has conducted a study into the impact of oil industry hydraulic fracturing operations on drinking water and has issued a draft version of a report on the study. Although there are significant gaps in the data relating to this difficult issue, the agency has found that there are situations where water impacts can happen and have occurred. The agency’s report says that a focus on situations where water impacts are most likely to happen can prevent or reduce future problems.
“EPA’s draft assessment will give state regulators, tribes and local communities and industry around the country a critical resource to identify how best to protect public health and their drinking water resources,” said Dr. Thomas Burke, deputy assistant administrator of EPA’s Office of Research and Development. “It is the most complete compilation of scientific data to date, including over 950 sources of information, published papers, numerous technical reports, information from stakeholders and peer-reviewed EPA scientific reports.”
Surface water impactsFracking, as hydraulic fracturing for oil production is commonly known, can impact drinking water supplies by removing water from drinking water sources, the draft report says. That caused a water shortage in the Haynesville shale area in Louisiana in 2011, for example. And water volumes reported for annual fracking operations have exceeded readily available freshwater supplies in 17 Texas counties, the report says. Overall, however, in most areas where fracking is taking place, the local water supplies greatly exceed the fracking needs. And the use of brackish water, rather than drinking water, or the use of surface water rather than aquifers, can alleviate situations where water supplies are tight. To a certain extent, water consumption can be reduced through the re-use in fracking of fracking wastewater.
A potential source of water contamination is the surface spillage of fracking fluids, given that the fluids, if not contained, could migrate into drinking water sources. The fluids consist predominantly of water and sand, which are not generally harmful. However, chemicals added to the fluid can be problematic. Although these chemicals only represent a tiny portion of the fracking fluid mix, the huge quantities of fracking fluid typically used result in the need for a significant volume of chemicals, the report comments. Over the years the EPA has documented 151 fluid spills, of which 13 impacted surface water resources. However, there is no data relating to the factors behind the spills and no data about the impacts of the spills on the water.
Spill prevention techniques, such as secondary containment systems and spill response capabilities, can mitigate this type of fluid spill problem, the report says.
Leakage from wellsAn escape of fracking fluids, or produced hydrocarbons, into the environment can also happen as a consequence of leakage from a well bore, especially as a consequence of a fracking operation, when hydraulic pressures in the well are substantially increased. There was an instance of an inadequately cemented well in Ohio leaking methane into local drinking water. And in North Dakota a well casing burst during a fracking operation, resulting in the release of fracking and formation fluids into a groundwater resource.
It is also theoretically possible for fracking fluid to leak to an aquifer through the subsurface fractures created by the fracking operation. However, in practice, fracking typically takes place many thousands of feet below any aquifers, thus making this cause of water contamination unlikely, the report says. There are a few places, such as in the Wind River basin, Wyoming, where there may be a problem with fracking operations within a location with drinking water resources. And the collocation of wells subject to fracking with other wells can raise the risk of a fluid leakage through those other wells, the report says.
The keys to preventing water contamination as a consequence of a fracking operation are ensuring the mechanical integrity of wells and maintaining adequate separation between the targeted rock formation and any underground drinking water resources, the report says.
Produced waterAfter a fracking operation has been completed and a well is producing oil or gas, water comes from the well, both in the form of used fracking fluid and in the form of water that had been present in the hydrocarbon bearing rock. This produced water, if not handled appropriately, could be spilled and thus contaminate a drinking water source. Although produced water spills have been reported across the United States, most of these spills have been relatively small. There have, however, been a small number of large-volume spills, including 12 spills greater than 21,000 gallons in North Dakota. Of 225 produced water spills characterized by the EPA, 30 spills reached surface water bodies, the report says.
The largest produced water spill noted in the report took place in 2015 in North Dakota, when 2.9 million gallons of water escaped from a broken pipeline and flowed into a local creek, the report says. Spill response actions mitigated the impacts of this spill. And, in general, spill prevention and response activities can protect water bodies from produced water spills, the report says.
Wastewater disposalThe disposal or re-use of wastewater can also pose some water contamination risks. Most of the water is disposed of underground by injection though approved disposal wells, the report says. Re-use of the water is much less common, except in certain specific regions, such as in Marcellus Shale gas wells in Pennsylvania. Evaporation ponds and other above ground disposal systems have also been used on occasion.
There have been documented examples of water contamination from above ground disposal systems, and from unlined or inadequately constructed wastewater storage pits, the report says.
The report says that some of the chemicals used in hydraulic fracturing are known to be hazardous to human health but there is an absence of data on any presence of these chemicals in drinking water. Local and regional hazard assessments could be conducted, the report suggests.
Data gapsIn general, there are significant gaps in the data required for a full assessment of the impact of hydraulic fracturing on drinking water, in part because data have not been collected or are not publicly available, the report says. There is also significant uncertainty relating to the complexity of the underground environment and the possibility of water contamination having multiple causes.
However, the report recommends a focus on issues most likely to result in drinking water problems, such as the withdrawal of fracking water from areas with low water availability; the spillage of fracking fluids or inadequately treated wastewater; ensuring the mechanical integrity of wells; avoiding the injection of fracking fluids directly into groundwater resources; and the inappropriate surface storage or disposal of wastewater.
In Alaska, the Alaska Oil and Gas Conservation Commission regulates drilling and hydraulic fracturing, including the enforcement of strict rules regarding well integrity. The Alaska Department of Environmental Conservation regulates surface environmental protection, including the protection of water bodies.