Under the streets of most American cities, water and natural gas are leaking from aging pipes. Large natural gas leaks are an immediate safety risk, but even small leaks are not completely benign, and they may be more common than previously thought, according to the preliminary findings of a new methane mapping project being carried out by Environmental Defense Fund and Google Earth.

Natural gas is often touted as being far cleaner than coal in terms of greenhouse gas emissions, but that depends on how much natural gas is leaked in the extraction and delivery process. And unfortunately, there is little accurate historical data on just how much natural gas is seeping into the atmosphere.

To understand just how much methane is leaking underneath most major metropolises, Environmental Defense Fund and Google Earth have partnered to create interactive online maps that show the leaks below the streets of Boston, Indianapolis and New York’s Staten Island, with more to come.

The trio of cities is part of a pilot project to use Google Street View mapping vehicles that are equipped with specialized gear that can measure environmental indicators and then make that information public.

For the past two years, EDF has been investigating methane as part of its data collection effort to better understand the climate impacts of natural gas. Methane constitutes only 9 percent of U.S. greenhouse gas emissions, according to the EPA. But methane is 84 times more potent than carbon dioxide over a twenty-year time frame, according to EDF. About one-third of U.S. methane emissions come from the natural gas industry.

“Methane leaks are a pervasive challenge throughout the natural gas industry. This is an ideal chance to put new science to work and to solve a major real-world challenge,” Steven Hamburg, chief scientist for EDF, said in a statement.

The sensing technology was developed by researchers at Colorado State University and EDF, and it is used in a system that not only locates methane but can also identify very small trace amounts of the gas. Each leak was verified with at least two sampling runs. The algorithms used to map the leaks will be published in a scientific paper later this year.

On average, EDF found that there was about one leak for every mile the cars drove in Boston and on Staten Island, although those were often clustered in certain neighborhoods. The information has been shared with local utilities, which can use it to prioritize upgrades, especially in older cities. Indianapolis, with its more modern gas infrastructure, had far fewer leaks. 

“We support what EDF is doing to bring new science, new tools and new data into the conversation so that we can better understand what the methane looks like from the wellhead to the burner tip,” said Susan Fleck, VP of pipeline safety for National Grid.  

In June, Massachusetts Governor Deval Patrick signed a bill to accelerate the detection and repair of leaks that pose safety threats, but it doesn't necessarily address this issue. “You have a situation where a system has many chronic leaks that don’t present a threat to safety and yet may present a real environmental threat,” said Mark Brownstein, associate VP and chief counsel for natural gas at EDF.

Currently, class 3 leaks, which are non-hazardous, are monitored and repaired over time, but utilities' records don’t usually break down which class 3 leaks are the biggest. Hamburg said that by prioritizing larger type 3 leaks, utilities could double or triple the reduction in leakage across this class of leaks.

“Until now, these smaller leaks have not been a priority in most places. Yet we can see from these maps just how much they can add up,” said Brownstein. 

Screen grab of EDF map of Boston methane leaks

Assessing the entire supply chain

Although the older pipe networks are rife with leaks that contribute to climate change in aggregate, the larger source of greenhouse gas emissions from natural gas is from the extraction phase of the supply chain.

Last fall, EDF released a study that found methane emissions are lower than estimated by EPA for well completions, but emissions are higher for valves and equipment that control operations at a well site.

The study also found that EPA’s New Source Performance Standards, which require all new fractured natural gas wells to burn off or use emissions controls known as green completions, are effective in reducing emissions.

EDF and Google’s work is an important step in building a larger database of emissions that is not self-reported by the industry. In an episode of Showtime’s Emmy-nominated Years of Living Dangerously, government and university researchers discussed how their research found that methane leaks at natural gas production sites were higher than the EPA numbers, which largely come from industry sources.

One study from Cornell University found the incidence of leakage was about four times higher than industry reports. Independent studies and more accurate databases can help educate regulators. Earlier this year, Colorado became the first state to restrict methane emissions from oil and gas production.

EDF is not just focusing on production and distribution of natural gas, but plans to use Google Earth and sensing technology to study processing facilities, long-distance pipelines and commercial truck and refueling stations to paint a full picture of methane emissions from the natural gas industry, which could be very different than the one the EPA has been able to piece together.

The environmental organization is not just stopping at natural gas, either. The team is already working with other cities to map other pollutants, such as ozone, benzene, carbon monoxide, SOX, NOX and other volatile organic compounds. “There’s an enormous amount of technology, and we can bring that to bear on the problems we face today,” said Hamburg, although he did not specify the next pollutant EDF would try to map using this technology.

The EDF website allows the public to suggest which city the company should bring the methane mapping to next, and Hamburg added that Southern California Gas Company is definitely one of their next stops.