VANCOUVER — Fracking in Carroll County, the heart of Ohio’s natural gas boom, hasn’t contaminated groundwater, new research shows. The study is the first in the country to evaluate drinking water quality before and after the local onset of hydraulic fracturing, better known as fracking.
Some residential water wells did contain high levels of methane, which is the core component of natural gas. But researchers reported October 19 at the Geological Society of America’s annual meeting that the contamination came from natural biological sources such as soil bacteria, not leaky gas wells. Previous studies in Pennsylvania and New York linked fracking wells with methane pollution in groundwater (SN Online: 6/25/13).
“Our data show that fracking can be done in a way that maintains the integrity of the groundwater,” said Amy Townsend-Small, a geochemist at the University of Cincinnati.
Fracking taps the natural gas that fills pockets deep underground. In some regions, such as the Utica Shale in northeastern North America, the natural gas spreads between many smaller cavities. To reach the trapped methane, companies start by drilling down several kilometers. Fracking fluid, a mixture of water, sand and chemicals, is then pumped into the shaft at pressures high enough to fracture surrounding rock and allow the sought-after gas to bubble to Earth’s surface.
Proponents of natural gas say the technique offers cheap fuel, but critics contend the mixture of fracking fluid and gas could contaminate local groundwater. If the steel and concrete casings surrounding a fracking well fail, methane and fracking fluid can seep into groundwater. Despite the fracking boom in recent years, no previous studies had compared groundwater contamination before and after fracking activity began.
“The science woke up to the need for data after the drilling had occurred in a lot of places,” said Stanford University environmental scientist Robert Jackson.
As the gas boom hit Ohio in 2012, Townsend-Small looked to Carroll County, which has the highest number active gas wells in Ohio and roughly 90 percent of private land is leased to natural gas companies for underground gas extraction. She began sampling 23 residential water wells, a water source that many people in that rural area rely on for their drinking water.
In Townsend-Small’s lab, the team measured methane levels in the water. Methane doesn’t pose a health hazard apart from its flammability, but it can signal that other chemicals involved in fracking are also escaping.
But methane in groundwater can also come from soil bacteria. To tell the difference between bacterial methane and fracking-related contamination, the team measured the isotopes, forms of carbon and hydrogen, that make up the methane.
After more than two years collecting and testing water samples, Townsend-Small and her team detected only negligible levels of methane in the water from most of the 23 homes. The researchers did identify four homes with methane concentrations above the explosive threshold, the point where water becomes flammable. In all cases, the methane came from soil bacteria, not from natural gas.
So far, Townsend-Small hasn’t seen an increase in methane as fracking activity has intensified or a correlation between high methane levels and proximity to gas wells.
“That could change at any time,” said geochemist Claire Botner, who works with Townsend-Small at the University of Cincinnati. “Many of the [fracking] wells in Carroll County are just permitted, which means they’re still waiting to be drilled.” This year, the team has expanded its monitoring to 96 homes in a larger area of Ohio.
Long-term studies such as this one are important to improving fracking safety, Jackson said, even when they don’t find contamination. “The most important thing is to figure out when things go right, why they went right,” he says. “And when things go wrong, how do you keep them from happening elsewhere?”