December 13, 2012 By Creighton Welch
Natural gas leaks can cause serious problems in our cities -- on Dec. 11, for instance, a 20-inch Columbia Gas transmission line exploded in Sissonville, W. Va., and destroyed four homes and essentially cooked a section of the interstate.
To see what Boston had going on in its natural gas pipelines, a team of scientists set out to map and measure leaks throughout the city. After all was said and done, they spent a month driving 785 miles -- and they discovered 3,356 methane leaks.
Jackson helped lead the study along with Nathan Phillips, associate professor at Boston University’s Department of Earth and Environment. During the month they spent measuring, they drove about 20 miles-per-hour down each street, sometimes in both directions, using a tool called a Picarro G2301 Cavity Ring-down Spectrometer.
It’s a fast-response methane analyzer that measures methane concentrations higher than 2 parts per million (the normal amount in the air). They combined the methane measurement device with a high-resolution GPS, and loaded those in the car. The devices were connected so as they measured methane concentrations, they also mapped where they were. This information was then loaded into a GIS file to produce a map of the measurements.
When they found large methane leaks that could pose an immediate explosion threat, they stopped and gathered an air sample to analyze the chemistry to determine if the leak was coming from a sewer or landfill, or if it was pipeline gas. A vast majority of the leaks were from pipelines. While all leaks were measured and mapped, the team called in six pipeline leaks they felt were explosion risks, which the utility companies then fixed.
“We tried to work constructively with the gas distribution companies as well as the city,” Jackson said. “The main reason they have so many leaks is because they have so many old pipes. The No. 1 goal should be to replace those old pipes as quickly as possible.”
The report even got the attention of a top U.S. congressman on the Energy and Commerce Committee.
Finding Gas Leaks via Plane
In Central California, UC Davis atmospheric researchers recently surveyed utility company's Pacific Gas & Electric Co's 600 miles of natural gas pipelines in a plane -- a single-engine Mooney TLS filled with "scientific instruments designed to sniff out leaks of methane," the Los Angeles Times reported. The mission was to quickly and cheaply find gas leaks several miles downwind from the source, and then dispatch ground crews to fix the problem. Image courtesy of AEROSPACE
“This study shows that we need a plan to ensure leaks from aging natural gas pipelines in Boston and other cities and communities are repaired, so that we can conserve this important natural resource, protect the consumers from paying for gas that they don’t even use, and prevent emissions of greenhouse gases into the environment,” Massachusetts Rep. Ed Markey wrote in a letter to the Pipeline and Hazardous Materials Safety Administration.
This technique used on the ground does not provide an amount of gas, just a concentration. “This first step gave us the hot spots,” Jackson said. “Just because you have a high concentration, that doesn’t tell you if it’s a big leak or a small leak. For example, if the wind is blowing hard, the methane will be carried away from the leak. Now we’re trying to get the total amount of methane leaking into the atmosphere.”
They can do this by combining the street work with sensors on top of buildings and skyscrapers that can track the movement of the methane.
This information has a number of important uses. The study itself makes publicly available this information about the health and safety of the community. The information can then be utilized for environmental purposes to help cut methane emissions, reduce greenhouse gas losses and lower ozone formation.
It can help save money from the consumers. According to Boston Mayor Thomas Menino, natural gas leaks cost tens of million dollars per year, and those costs typically are passed along to the community.
And it can help keep citizens safe.
“I think in the very near future you’ll see this approach used by a majority of cities,” Jackson said. “I think you could now put a study like this on the ground for less than $100,000. If by doing such a survey you can stop one explosion from happening, you’ve saved some lives and paid for the survey. Better will information will provide the impetus for fixing problems.”
Image at top shows relative volume of methane leaks at various locations around Boston. Credit: Boston University