Boston’s Leaky Legacy


Boston’s old and decaying natural gas infrastructure has the potential for huge economic, health and environmental impacts on the residents of the city.

Boston is one of the oldest cities in the United States and aging with the city is its infrastructure. Above the ground, stretches the Freedom Trail and epic architecture, but about three feet under, the city shrouds a network of leaky natural gas distribution pipelines. Some of these pipes are made of coated steel and plastic, indicating that they have been laid in the last three to four decades, but most are made of cast iron, dating as far back as the late 1800s when natural gas distribution first began. And some of those old pipes leak.

To some urban dwellers, leaking natural gas pipes may not come as much of a surprise, or even much of a worry. But that changes when losses are quantified. Nathan Phillips, professor of geography and environment at Boston University, has estimated that unaccounted-for gas in Massachusetts which amounts to eight billion cubic feet  or $40 million worth of natural gas per year. Of this, an estimated $4 million is being lost in Boston alone. Worse yet, methane, escaping from a punctured pipeline, is no longer a valuable domestic fuel but instead it’s a potent greenhouse gas, an explosive fuel and a health hazard.

Climate scientists have deduced that 7 to 15 percent of the global human-caused loss of methane comes from cities and urban centres. The main sources of urban methane are landfills, sewage treatment plants and natural gas distribution pipes. While expectations to reduce greenhouse gases are set globally, mitigation needs to happen locally. But in order to reduce levels researchers need first know how much methane is being released into the atmosphere from targeted sources. In the last few years, scientists have started measuring methane levels from individual targeted sources in cities and discovered that, in Boston, a significant amount is released from natural gas pipes. Leaking pipes are low hanging fruit, as compared to other urban methane sources. They are easy to identify and arguably simple to fix.

Phillips heads the Urban Metabolism project at BU to monitor greenhouse gas emissions in Boston. He started exploring methane leaks when his path serendipitously crossed that of Robert Ackley, owner of Gas Safety USA. One fall morning in 2010, Ackley was perusing the streets of Newton, MA with his flame ionization detector to find leaks in distribution pipes. The detector works on a simple principle- it uses a tiny flame which spikes upon contact with methane, a highly flammable gas. Phillips, who was taking his 5-year-old son for a stroll, had never seen the detector before and asked Ackley about it. The two researchers got talking and Phillips, immediately spotted a missing link in his own work. He used an instrument called the Picarro gas analyzer on the roof of a BU building to determine levels of carbon dioxide, methane and water vapor, in well-mixed samples of air. But if he could calculate the amount of methane leaking from distribution pipes, then his research could estimate the total amount of methane in Boston from independent human-caused sources. So Phillips, Ackley and Eric Crossan, Chief Technical Officer at Picarro took a drive through Boston in a car fitted with a Picarro greenhouse gas analyzer. Over the next ten months, Phillips patrolled the streets of Boston and its neighboring suburbs detecting and monitoring levels of methane from natural gas pipe leaks. One October morning, I joined the professor on a leak-detection tour in the Boston suburb of Brookline.

“Watch out, it’s hot in there,” said Phillips, as he opened the door of an SUV crowded with four Boston University students, lots of wires, some computer screens and other assorted gadgets. A baritone hum emanated from the back of the vehicle where a Picarro greenhouse gas analyzer sucked out the car’s energy to warm itself up to 1040F, its desired start up temperature.  The analyzer is a large metallic box with lots of buttons and blinking lights. A pipe, dangling from Picarro’s gas inlet, was waiting to feed it with air samples. At 7 am on a frigid Saturday morning, the BU crew looked surprisingly alert and ready for their mission.

Phillips quickly explained the rules of the hunt. “Baseline methane levels in Boston are about 2.1 ppm right now. When those numbers jump higher than that, it means that we are driving over a leak.” He twisted around under the tight grasp of his seat belt and tapped the corner of a computer screen resting on his student- Nurika’s, lap.  The students nodded their heads in acknowledgement and started parallel conversations about the impacts of methane on trees.  Methane molecules are lighter than oxygen so they easily rise and displace oxygen in porous soil, hampering respiration in tree roots.  Methane is a dry gas and also displaces moisture in the soil. An affected tree may die of methane asphyxiation. Researchers suspect that plants tolerant to swamp conditions have greater resilience to methane leaks in cities, as swamps naturally produce huge quantities of methane. “Honey locus trees are more resilient too,” Phillips said. Before he could explain why Nurika called our attention to the numbers on the screen that had suddenly jumped to 3.0 ppm.  The car had just turned around Kenmore square and onto Beacon Street, and the students were excited. Phillips nodded in acknowledgement and kept driving.

A study from The Netherlands published in 1986 established a connection between dying street trees and natural gas leaks. The Dutch researchers worked with municipal bodies and found that most trees in their cities died in the latter half of the 1960s, after the country made a switch from coal gas to natural gas. Ackley explains that city trees are exposed to several threats- road salt, insects and storms. Methane makes these trees more vulnerable to such threats. Some neighborhoods can afford  active replanting of dying trees. “But the damage has been going on for 30 years,” said Ackley “there are some places which have not re-planted for 20 years because of lack of funding.” Ackley is working with environmental attorney Jan Schlichtmann to represent the towns of Hingham, Nahant, Milton, Saugas and Brookline which are suing their natural gas distribution companies for tree damage from gas leaks.

Driving down Beacon Street, Phillips explained how to identify locations of gas pipes. “Those yellow spray painted arrows mean that there are gas pipes underneath,’ he said, pointing to the road-“Blue means water and red refers to electricity.” Again, he was interrupted by Nurika who called attention to a 5.3 ppm reading at the intersection of Park and Beacon streets. “Ooh that’s a big one,” said Phillips rolling down his window and sniffing violently. Phillips called gas companies, like N Star, efforts to repair leaks “Band-Aid solutions”, there are so many leaks in a given pipe that fixing one leak is almost never a solution.  Entire pipe systems needed replacement. The numbers on the screen jumped all over the place in testimony to the professor’s words.

The troupe headed towards Brookline reservoir, down Walnut Street. The well-to-do neighborhood offered a welcoming view with sprawling houses and cascading lawns. But the numbers on the computer screen presented a different picture.  Nurika read them out like a mechanical countdown that never reached below 3.  A 12.1ppm- reading stopped the car in its tracks and a pungent odor of gas wafted in as Phillips rolled down his window in front of a brick-fronted house, with pumpkins in its well-manicured yard.

Natural gas is colorless, and it’s rendered odorless after sulfur and water are removed from it to make it easier for distribution. Because it’s highly flammable, mercaptan- a chemical odorant is added to it to help identify leaks. Mercaptan smells like rotten eggs. Though he has smelt and identified leaks in many parts of the city, Phillips has been judicious about the ones he calls out. “I’d be stopping every couple of miles if I were to call out all dangerous leaks,” he explains “besides, most of these leaks have already been called in before and have not been fixed.” Earlier this year, Phillips called in a leak in Back Bay when the Picarro registered an explosive reading of 30 ppm. He added that he tries to call in most leaks that have a building foundation within a five foot radius from the leak to mitigate the threat of an explosion.

Methane’s flammability makes pipeline leaks a threat to climate-change deniers too. Since methane is lighter than atmospheric air, it rises from punctured pipes and collects in enclosed spaces like manholes and building foundations. If a manhole has 4 percent methane, gas companies grade it as a level 1 leak, which is dangerous and needs immediate attention. Phillips has seen manholes filled with 10 percent concentrations of natural gas. Ackley estimates that it costs about $3000 to fix a leak in a pipe. In most cases, gas companies don’t replace the worn-down pipe but replace the manhole cover with a slated one. A slated cover allows the collected gas to escape but the space created is immediately replaced with more leaking gas.  The result is either an explosion or a large consumer gas bill. In Massachusetts, both have happened.

In the last decade, there have been 19 gas explosions in the state of Massachusetts. Four blasts took place in 2009 alone, killing a 62-year-old resident in Somerset and critically injuring three others.  Ackley says that “no one cares unless someone loses an eye.” He had just returned from Allentown, Pennsylvania exploring a leak which had led to an explosion in February 2011, killing five people. When asked what prevents explosions from happening everyday in Boston, his response is authoritative- “Luck! Pure luck.” Soon after, he learned that I lived right off of Boylston aka Route 9 in Boston. “It’s a mess over there! All the trees are dying and Route 9 is crazy and filled with leaks.” The Cupertino, CA, gas explosion in September 2011 that destroyed an entire condominium is a clear indication that even plastic distribution pipes are not leak-proof.

Gas companies have few incentives to repair these leaks. The ‘cost of gas adjustment clause’ in the state of Massachusetts charges the consumer for lost and unaccounted for gas.  Massachusetts has the second-oldest pipe system in the country after Delaware but has the highest per capita distribution of cast iron pipes in the country. Shanna Cleveland, an attorney with Conservation Law Foundation (CLF), notes the presence of wooden pipelines in Downtown Boston dating back to the pre cast-iron pipeline era. “Everyone’s concerned about the cost of repairing leaks,” she says “but we forget that tax payers are already paying for lost gas.” Cleveland explained that CLF is working with Phillips and his team to understand the magnitude of the problem and to create policy solutions. Phillips too feels that the problem is larger than the costs involved in fixing leaks- “The real question should be how much it costs us not to fix leaks- $40 million per year.” Using the Picarro, he had recently picked up a leak with a methane reading of 7 ppm in his own house in Newton.

This year, Massachusetts state representative, Lori Ehrlich filed four bills demanding more inspection transparency and environmental responsibility from gas companies in the state. She explains that the Department of Utilities pays gas companies to replace entire pipe systems and not for repairing leaks. Hence, unless there is a high threat of explosion, private companies don’t have any incentive to repair leaks. “But leaks don’t repair themselves, they only get worse over time,” said Ehrlich. This is the first time a representative has filed these bills in the state and they have received bipartisan and bicameral co-sponsorship from over 40 Massachusetts legislators. The bills will be out of legislature next summer and Ehrlich is hoping for constructive measures.

Explosions are only one of methane’s health hazards. In confined spaces inhaling methane can have the same effects as other forms of asphyxiation like carbon monoxide poisoning. Once it’s released into the air, methane is a key ingredient in a toxic soup of chemical reactions that lead to the formation of ground ozone.  The other ingredients for this reaction are nitrous oxides and light- both readily available in urban settings. Ozone molecules in the stratosphere are pivotal to protecting human health and other organic matter from the sun’s harsh rays, but- closer to the Earth’s surface-in the lower troposphere they do just the opposite. They are highly reactive molecules and corrode any biological tissue they come in contact with. The internal linings of lungs are extremely vulnerable to ozone-induced degeneration. For this reason, the EPA monitors ozone levels and calls for Ozone Code Orange Days when levels rise beyond safe limits (101-150 on the Air Quality Index). On such days children, the elderly and people with asthma or other respiratory disorders are advised to stay indoors and avoid heavy physical activity.

J. Jason West, Assistant Professor, Department of Environmental Sciences & Engineering at the University of North Carolina has found a direct correlation between morbidity and mortality rates and ozone levels. “Ozone is listed as one of six urban particulate matter that is regulated by the EPA but none of ozone’s regulatory factors include mitigating methane levels,” he said. Methane has a long lifetime in the atmosphere which means that it can contribute to the formation of ozone over a longer period of time even though the reactions are slow. “I wouldn’t want to put words in the EPA’s mouth,” said John Levy, professor of Environmental Health at Boston University “Methane is a very challenging pollutant to control emissions and, given its diversity of source, it’s much harder to mitigate.”

On Earth Day 2011, Boston Mayor, Thomas Menino released new goals for Boston’s Climate Plan. Heading the list was an optimistic endeavor to reduce community greenhouse gas emissions -25 percent by 2020 and 80 percent by 2050. But how does one find out if these reductions have been met? Lucy Hutyra, assistant professor at BU’s department of geography and environment argues that “we need to have a framework to validate whether regulations are being met.” Hutyra represents a larger scientific community concerned about the 80 percent of the country’s greenhouse gases that come from urban centres.

Methane’s greenhouse gas potential is 20 times greater than carbon dioxide when measured over a 100 year period. This is a very worrying and frustrating fact for climate scientists who recognize that not enough is being done to mitigate human-caused emissions of methane.  According to Phillips “the best way to reduce the greenhouse gas potential of these leaks is to light them all on fire (which will break methane down to CO2 and water). Boston will be ablaze but at least the planet will have fewer greenhouse gases.”


  • Nathan Phillips: Professor, Geography and Environment, BU.
  • Robert Ackley: Gas Safety USA.
  • Eric Crosson: Chief Technical Officer, Picarro.
  • Lucy Hutyra: Assistant Professor, Department of Geography & Environment, BU.
  • Arlene Fiore: Physical Scientist, Atmospheric Chemistry, Physics and Climate Group, Princeton, NOAA.
  • Shanna Cleveland: Staff Attorney, Conservation Law Foundation.
  • J. Jason West: Assistant Professor, Department of Environmental Sciences & Engineering, University of North Carolina.
  • Jonathan Levy: Professor, Environmental Health, BU.
  • Representative Lori A. Ehrlich, CPA, MPA, Vice Chair Committee on Labor and Workforce Development, MA
  • Frank Gallagher-

Written for an ‘Advanced Science Writing’ class at Boston University with Ellen R. Shell. 

Estimating methane from livestock (LOE)

Close to the end of my internship with Living on Earth, I worked on a short story which I got to narrate myself. Not only was I excited about my voice being carried on a Public Radio International show, I also got to say “poop” on the radio. I doubt that will ever happen again.

The story describes a study by researchers from the University of Bristol and the Teagasc Animal and Grassland Research Centre in Ireland. According to the study, quantities of a compound, archaeol, in cow dung, is directly proportionate to the amount of methane released by the animal. If such is the case, then climate scientists will no longer have to rely on rough estimates for methane from livestock.

CLICK HERE to listen to the story.