By TIM FAULKNER/ecoRI News staff
Beneath our streets and front yards lie miles of leak-prone natural-gas pipes. Most are decades-old cast-iron and steel pipes. How much gas is escaping into the atmosphere and contributing to climate change is hard to calculate.
A 2015 Harvard University-led study estimated that nearly 3 percent of natural gas is lost as it moves through gas mains and service lines that connect to homes and businesses across southern New England. It may not sound like much, but depending on the season, the leaking gas accounts for between 60 percent and 100 percent of methane emissions in the region. Natural gas, of course, is about 90 percent methane, one of the most potent greenhouse gases.
Massachusetts and Rhode Island are looking to patch these errant emissions to meet their long-term climate change emission reduction goals.
Fortunately, these old and leaking pipes are getting replaced, albeit slowly. Rhode Island is currently on pace to replace 1,237 miles of leak-prone pipes — about 39 percent of all gas pipes in the state — by 2035. Massachusetts has an estimated 20,000 gas leaks, but only those that pose an immediate health hazard are being fixed.
To speed up and expand the process, Massachusetts passed a law in 2016 to repair leaks that pose a low threat for explosion but still cause a significant environmental impact. As a result of the law, the state Department of Public Utilities (DPU) is exploring ways for utilities to quickly and affordably spot and fix the leaks, known as fugitive emissions.
As part of its efforts to curb climate emissions, the DPU released new rules in December that set emission caps for gas-distribution companies such as National Grid and Eversource Energy based on the miles of pipeline they own. The caps are expected to cut emissions by 10 percent by 2020.
Natural gas, of course, isn't a liquid but an invisible and mostly odorless gas. Leaks therefore seep undetected into the ground and percolate up into the atmosphere. In addition to causing explosions, leaky gas pipes increase ground-level ozone and reduce oxygen. They also kill vegetation, such as trees. In Massachusetts, Brookline, Hingham, Milton and Saugus have filed lawsuits against National Grid for not fixing leaky pipes that killed trees in their communities.
National Grid, the largest distributor of natural gas in the Northeast, is gradually replacing these gas lines. In 2015, they replaced 75.3 miles of gas lines in Rhode Island. In 2016, 64.6 miles were replaced. They plan to replace another 65 miles this year.
The improvements are part of a $445 million upgrade to pipes and natural-gas infrastructure in the state. Ratepayers pay those costs. Environmental advocates claim repairing leaks and replacing old pipelines reduces the need for new, interstate gas pipelines and other fossil-fuel infrastructure, such as power plants.
The Conservation Law Foundation estimates that gas customers in Massachusetts pay $38.8 million annually for gas that is lost from leaks.
“It's consumers that pay the price for a perpetually leaking gas system. The end consumer pays for all of the gas that local distribution companies purchase from producers, regardless of how much of that gas is lost to leaks (or other causes) on the way to consumers’ homes and businesses,” CLF said its report Massachusetts’ Triple Threat: Understanding the Impact of Natural Gas Leaks on Public Safety, the Environment and Your Wallet.
Distribution pipelines are the “mains” that run under the street and can be 2 inches to 2 feet in diameter. Service pipelines are the gas pipes that connect from the main to homes and businesses. They are about 2 inches in diameter.
Transmission lines are the large pipelines that carry natural gas from the well, such as a fracking field, to a regional distribution center.
Prior to the 1950s, many of the mains and service pipes were made of cast iron. In the 1950s, the pipes switched to steel. Since the 1980s, plastic composite tubes have become the primary material for pipelines and now account for more than half of distribution and service pipes.
National Grid says that the age of a service line or a gas main doesn’t necessarily mean that it leaks. According to the company, third-party incursions caused by construction close to the lines by contractors or homeowners causes most leaks.
The new plastic pipelines are flexible and lighter than the cast-iron and steel mains, some of which date back to the late 1800s. Cast-iron and steel sections were mostly welded together. The plastic sections are fused to one another with a heat-producing device. This eliminates the joints between sections, which are the source of many leaks.
Wood pipes were first used when gas pipelines began in the mid-1800s. They were eventually abandoned for cast iron and steel. Some wood pipes remain in the ground but are unused.
The advocacy group HEET Home Energy Efficiency Team of Cambridge, Mass., says the public can help patch leaky pipes by supporting state bills and municipal endorsements of efforts to speed up repairs.
The public can also help by reporting suspected leaks to their utility. Patches of dead vegetation are a sign of leaks. A sulfur-like smell is another. A substance called mercaptan is added to natural gas, which is odorless, to give it its distinctive rotten-egg smell.