Shared Action Plan Annual Results

This report documents the progress of a first-in-the-nation shared action plan involving gas utilities identifying and repairing distribution system leaks with the largest environmental impact. HEET’s role is to independently verify results and make recommendations to utilities for improvement.

Massachusetts has some of the oldest natural gas infrastructure in the country.¹ Old pipes in this system are leaking methane, a greenhouse gas 86 times more potent than carbon dioxide over the first 20 years in the atmosphere.² The cost of this wasted gas is passed on to customers and is estimated to be millions of dollars per year.³ Methane from gas leaks also poses a safety hazard to both people and vegetation.

Research in 2016 showed that just 7% of the Metro Boston distribution system leaks emit half of all the gas by volume, creating a clear policy opportunity.⁴  Later the same year, the Massachusetts Legislature enacted a law requiring that these leaks of significant environmental impact (‘SEIs’) be repaired, since doing so would cut methane emissions in half for the least cost to the utilities and the least disruption to cities and towns. Gas companies had always been mandated to focus on the potential hazardousness of a leak and not emissions, and had no reliable and accurate method to identify SEIs. In 2017, HEET coordinated a large collaborative study to determine a new SEI identification method. Working with Eversource Gas of Massachusetts (formerly Columbia Gas, and now a part of Eversource Energy), and National Grid, Gas Safety Inc., Mothers Out Front and other stakeholders, the research team field-tested multiple methods and showed that a new leak identification protocol - the ‘leak extent method’ ⁵ - is a quick, effective and low cost solution.⁶ The shared action plan emerged from this collaboration.

Since 2018, National Grid and Eversource Gas have been using the leak extent method to identify SEIs and prioritize them for repair. Based on the testing of hundreds of SEIs by HEET since the beginning of the program, the utility SEI identification rate appears to be improving in accuracy over time.

Note: Regulations require that SEI leaks are repaired within 1-3 years of identification, depending on the extent and repair method. Emissions reductions are therefore expected to trail identification by 1-3 years.

The annual estimated impact of all SEIs based on the 20 year global warming potential of methane is currently equivalent to approximately 3% of Massachusetts’s greenhouse gas inventory, which is equivalent to the emissions of 1/3rd of all Massachusetts stores and businesses (i.e. the commercial sector) in 2017.⁷

Massachusetts is the first to enact legislation to identify SEIs, the first to determine an SEI identification protocol, and the first to test it widely in the field across multiple gas companies. We hope to report in coming years, when repairs of currently identified SEIs are confirmed completed, that we are also first in the nation to cut in half our methane emissions from the gas distribution system. This shared action plan work will continue to provide independent analysis, findings and assistance to utilities to help improve over time.

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• In 2021, Massachusetts gas utilities reported 24,578 leaks, about half of which were found that year. The other half were carried forward from previous years. 
• Reported Rates of SEIs: Based on 2021 quarterly leak inventory reports to the DPU, National Grid and EGMA reported SEI rates similar to the expected 7%, while Eversource reported a lower rate, closer to 2%.
• Accuracy of Identification: HEET sampled and studied 100 utility-identified SEIs this year to check that the leak extent method was being applied consistently. The utilities still appear to be identifying more SEIs than we confirmed.
• Eversource Gas of Massachusetts surveyors appeared to be over-measuring SEI leak extents relative to HEET by a factor of 3 on average, compared to a factor of 2 in the previous two years. National Grid surveyors appeared to be under-measuring SEI leak extents relative to HEET by 35% on average. This is similar to last year, and an improvement from year 1. Eversource’s extents appeared to be slightly under-measured on average. 

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• Of the studied SEIs, 5 of National Grid’s 58 leaks and 1 of Eversource’s 6 leaks would have required an increase in repair prioritization based on current Massachusetts Department of Public Utilities regulations 220 CRM 114.07, due to HEET measuring an extent over 10,000 sq ft where a utility measured an extent under 10,000 sq ft. This is compared to only one leak that would have required an increase in repair prioritization in the previous shared action plan year.

• Mobile survey: HEET ran a mobile gas leak survey with a Cavity Ring Down Spectrometer (CRDS). We did not find any unreported SEIs in our surveys. In total, we found 123 leaks which did not correspond to any of the 413 reported unrepaired leaks on our route.
• Repair Rates: SEI repairs are not always successful. This year, the repairs we surveyed eliminated all gas from the entire leak footprint only ½ of the time. While far from 100%, this is a significant improvement over last year’s rate of ¼. Repairs appear to be affected by pipe diameter. In the last 4 years HEET has done pre- and post-repair surveys of 12 leaks on pipes that were larger than 6 inches in diameter. Some showed a reduction in leak extent on the post-repair survey, but none showed a 100% reduction in gas at the site.

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