Where Does Fracking Wastewater Go? Socioeconomic Predictors of Class II Well Placement in Ohio

Abstract

Each hydraulically fractured oil or gas well yields millions of gallons of wastewater over its production lifetime.1 Most of this wastewater is stored underground in what are known as Class II wells.2 The authors of a study in Environmental Health Perspectives show that in Ohio, Class II wells that receive fracking wastewater are disproportionately situated in lower-income and rural communities.3

At different stages, fracking wastewater may contain different proportions of residual fracturing fluids, potentially toxic agents that occur naturally in some rock formations, and sodium chloride.3 In Class II wells, wastewater is injected into underground rock formations through a protective steel and cement casing.3 The layers of rock act as a natural containment barrier for the waste, although some studies have pointed to multiple potential pathways by which wastewater can contaminate drinking-water sources.4

The U.S. EPA has identified several ways by which fracking wastewater can reach drinking-water sources. Among them are fluid movement 1) through a fault in the well’s casing, 2) through the space between the casing and the wellbore, 3) into the underground formations that were meant to contain the injection site, or 4) through abandoned or completed wells that have been not been properly plugged. Image: U.S. Government Accountability Office.7

“Because of that contamination potential, it is important to understand the sociodemographic patterns of where these wells are located,” says senior study author Nicole Deziel, an exposure scientist at Yale University. Ohio, parts of which sit above the Marcellus and Utica shales, receives wastewater from its own fracked gas wells as well as those in neighboring Pennsylvania.3

Deziel and colleagues analyzed 2010 Census block group data from the state of Ohio by presence of Class II injection wells. Block groups are small census divisions that usually contain between 600 and 3,000 people.5 For each block group, the researchers assessed a series of sociodemographic factors, including population density, median household income, median age, and percentages of white residents, residents with a high school diploma or higher, and voter turnout.

“We thought these variables would best capture social vulnerability,” says Deziel. This is important because socially vulnerable communities may have fewer resources to mitigate outside stresses, including man-made and natural disasters.

The researchers identified 257 Class II injection wells in Ohio that were active at some point between July 2010 and March 2016. They obtained the geographic coordinates for each well from the nonprofit FracTracker Alliance, which compiles existing data on oil and gas facilities.

Of the 9,205 block groups, $2\%$ contained an active injection well. Compared with block groups without injection wells, block groups with wells were much less densely populated, with an average of 71.2 people per square mile versus 2,210 people per square mile. The odds of a block group containing an injection well decreased drastically with each additional 1,000 people per square mile.

Block groups containing Class II injection wells had lower median incomes than those without. In fact, the odds of a block containing an injection well were $13–17\%$ lower for each $\$\mathrm{10,000}$ increase in median income. Block groups with injection wells also tended to have higher percentages of older and white residents than block groups without wells.

These findings support a 2016 study in Texas that showed Class II injection wells were situated disproportionately in lower-income areas.6 Unlike the current study, the earlier research found a greater likelihood of injection wells in communities of color.

But census blocks are an imperfect proxy for an individual’s proximity to an injection well. “Rural census blocks can span a large geographic area, and we do not know exactly where people are living in that block or how close they may actually be to a well,” says Jill Johnston, an environmental scientist at the University of Southern California. Johnston was not involved in the current study.

The authors of the new paper note that lower-income rural areas also tend to be less densely populated, so it is unsurprising that injection wells would be sited there. They point out, however, that while the rural setting means fewer people may be exposed to potential well-related hazards, it also imposes disadvantages that could exacerbate health risks, such as distance from well-staffed health care facilities.

Identifying socially and environmentally vulnerable communities is just the first step in studying the potential impact of Class II wells, according to Deziel. “There’s a big question mark about exposures and human health risks in relation to these facilities,” she says. Future studies should investigate whether residents living near injection wells face an increased risk of chemical exposures or adverse health outcomes, say the researchers.

Biography

Lindsey Konkel is a New Jersey–based journalist who reports on science, health, and the environment.