CHATHAM — For many years, you could almost locate the intersection of Main Street and Old Queen Anne Road in Chatham by smell. The odor of natural gas meant you were there.
The low-grade leak in the pipes under the roadway was enough to cause a strong smell, but not enough to pose a public safety risk. Over the course of years, people reported the odor to the fire department and the gas company would investigate, taking measurements of the gas concentration at the scene.
“They have acceptable amounts of leakage,” Chatham Fire Chief Peter Connick said. The most minor leaks are classified as Grade 3 and need to be checked annually; Grade 2 leaks are checked every six months and must be scheduled for repair within a year. When concentrations are high enough to be potentially hazardous, they are classified as Grade 1 and are repaired on the spot.
On Aug. 11, firefighters were again called to the intersection and National Grid responded, digging up and fixing the leaky pipe over the course of a couple of hours.
As of July 15, National Grid's most recent filing with the state Department of Public Utilities, there were 18 Grade 3 leaks identified in Chatham, two in Harwich and none in Orleans, and there were no Grade 2 or Grade 1 leaks in any of those towns.
The danger of explosion from an outdoor natural gas leak is less than one might think, since the fuel needs to have the proper mix with oxygen to ignite. “It's really a pretty narrow range,” Connick said. Still, people should call the fire department anytime they smell natural gas. “If you smell something, say something,” he quipped.
A main concern about natural gas leaks is the environmental harm they cause. Methane, the primary ingredient of natural gas, is a potent greenhouse gas. Together with other sources of methane, like the production and transport of fossil fuels, livestock production and landfill out-gassing, natural gas leaks add to the greenhouse effect, which traps heat in the earth's atmosphere and contributes to climate change.
Local public safety officials have high praise for National Grid's responsiveness to leaks, even while describing the low-pressure natural gas distribution network on the Cape as “Swiss cheese.” In Chatham, other notorious leaks are at the rotary, at Route 28 at Bailey's Path and in several other spots. A longstanding Grade 2 leak at Chatham Bars Avenue was reclassified as a Grade 1 leak several years ago, necessitating emergency repairs during the middle of Chatham's First Night celebration.
“We are working to address methane emissions in a safe, efficient, and workable manner,” National Grid spokesperson Danielle Williamson said. As part of a comprehensive Energy Bill passed a year ago, state officials agreed to establish criteria for evaluating the environmental impact of leaks and to set timelines to fix those found to have significant environmental impact.
“We are collaborating with Massachusetts gas companies to define environmentally significant leaks, and are committing to plan to reduce all existing leaks in our backlog within 10 years – not just the environmentally significant leaks,” Williamson said.
While outdoor gas leaks have long been a problem on the Cape, the problem is less severe than in inland areas, Williamson noted.
“Approximately 30 percent of our overall gas system in Massachusetts is cast iron and bare steel pipe, which is most susceptible to leaks,” she said. “On the Cape, the system is newer, with most being plastic pipe – hence why leak activity is lighter on the Cape.”
Natural gas distribution systems move large volumes of gas along high-pressure lines, but then reduce the pressure to a trickle as the gas enters homes. Locally, safety concerns about those high-pressure mains prompted National Grid to reduce pressure in the system in 2014, necessitating a moratorium on new natural gas hook-ups. Those large mains are being replaced now, and the moratorium is expected to be lifted by 2019.