The Gas Leaks Map

At the end of every year, Massachusetts gas distribution utilities are required to file annual service quality reports to the Department of Public Utilities (DPU). HEET extracts and maps the reported leak locations from these reports.

Use the map to zoom in on your home, school, or business to find local gas leaks, noting the following:

  • The map is a snapshot in time as of the last day covered by the reports, December 31 of each year.
  • A leak could have been repaired or new ones developed since the reports were published.
  • Locations of leaks are reported using addresses. However, leaks are on mains or service lines under streets, not inside buildings.
  • Independent researchers typically find 1.5 to 3 times as many leaks as utilities report.
  • The estimated equivalent costs of leaked gas is based on the EIA‘s average price of natural gas delivered to residential Massachusetts customers for data from the being year mapped.

See more information below about the leaks and using the map.

Previous maps:

  • Map of leaks reported as of the end of 2021 is here.
  • Google leak maps prior to 2021 are here.

About the Leaks

Leaks are graded by the utilities to indicate how potentially hazardous they are, ranging from Grade 1 to Grade 3 SEI, defined as follows:

  • Grade 1 leaks are hazardous and must be repaired immediately. This includes leaks in or near a contained space, such as a building or manhole, where the gas could build up enough to potentially explode.
  • Grade 2 leaks are non-hazardous, but could become hazardous in the near future. They must be repaired within a year.
  • Grade 3 leaks are non-hazardous and are expected to remain non-hazardous. Grade 3 leaks initially designated on or after 1/1/2018 are required to be repaired or eliminated within 8 years. 
  • Grade 3 SEI are grade 3 leaks larger than 2000 square feet in rectangular extent – these are leaks of significant environmental impact, or SEI’s. They are approximately the largest 7% yet contribute approximately 50% of all leak emissions. They are required to be repaired in 1-3 years. HEET is working to improve utility adoption of the leak extent method to better identify SEIs in the field.

Leaks are reported with a specific status :

  • Repaired indicates repair work was performed on the leak.
  • Pending or open indicates the leak is not yet repaired.
  • Eliminated by replacement indicates the leak was repaired under the Gas System Enhancement Program (GSEP).
  • Eliminated by ‘otherwise’ indicates the leak was removed for a variety of other reasons. Examples include : a routine survey did not detect gas at the leak, the leak was reported at a wrong address, or the grade of the leak was changed.

A leak’s grade and status are indicated on the map as a number in a colored bubble e.g.depicts an open Grade 1 leak and depicts a repaired Grade 3 leak.

The map includes layers for repaired and open leaks for each gas utility. Different leak information is reported in the annual reports depending on the utility. For example, National Grid only includes leaks that were repaired or open, but not eliminated leaks. Eliminated leaks are not included in this map for this reason.

Utilities are also required to report a snapshot of their entire leak inventories on a quarterly basis to the DPU. A simple analysis of these reports shows that utilities are just about keeping up with the rate of new leaks each year, if all types of eliminated leaks are taken into account:

  • In 2022, 10,185 new leaks were found, and 10,814 leaks were repaired and eliminated.
  • In 2021, 11,624 new leaks were found, and 12,954 leaks were repaired and eliminated.
  • In 2020, 12,644 new leaks were found, and 13,659 leaks were repaired and eliminated.

Emissions Estimates

Leaks reported in 2022 were responsible for an estimated 6,497 metric tons of methane emissions, equivalent to 558,758 metric tons of carbon dioxide, or $8.9 million of leaked gas (based on the EIA‘s average price of natural gas delivered to residential Massachusetts customers in 2022).

Lost And Unaccounted For (LAUF) gas regulations require utilities to submit standardized estimates of their annual statewide methane emissions from leaks to the DPU. We used this data to find the average amount of gas emitted from each utility’s leaks. We multiplied this by each utility’s number of leaks in each municipality and each neighborhood of Boston.

For example, this is how Newton’s emissions estimate was calculated:

National Grid Boston Gas’s emissions from leaks (Source: 2021 LAUF reports*) = 207,806 Thousand Cubic Feet (MCF)
National Grid Boston Gas’s leak count (Source: Annual Service Quality Reports) = 13,620
Newton’s leak count (Source: Annual Service Quality Reports) = 880
Metric tons of methane per MCF of methane (Source: LAUF reports) = 0.0192

Newton’s emissions estimate
= 880 Newton leaks × 0.0192 metric tons/MCF × 207,806 MCF/year ÷ 13,620 leaks
= 258 methane metric tons/year

*National Grid does not produce separate LAUF reports for its two components Boston Gas and Colonial Gas. Therefore we estimated Boston Gas’ emissions based on their fraction of National Grid’s total leak count.

These are underestimates due to only including reported leaks. The state’s standardized method of estimating the rates at which methane emits from leaking pipes is also older and more conservative. More information on the LAUF data and emissions estimates can be found on the LAUF Calculator page. The majority of atmospheric-measured methane emissions are still unaccounted for in the state. These emissions could be from the distribution system leaks we mapped here, and/or elsewhere.

Using the Map

The map includes the following layers of information:

  • Open leaks reported by each utility, by town and Boston neighborhood
  • Repaired leaks reported by each utility, by town and Boston neighborhood
  • Estimated emissions and equivalencies, by both town and Boston neighborhood
  • GSEP plans (more information about GSEP can be found here)


The map application provides controls for navigating and exploring :


The map provides various layers of information which can be selected with the Layer List button. In the example below, National Grid Boston Gas repaired and open leaks layers are enabled, together with Boston neighborhood and MA town boundaries.

Interacting With the Map

To see detailed information about a leak, click on it. Use the Maximize button to expand it:

If multiple layers of information are available, use the Next feature and Previous feature buttons to scroll them. In this example, we scroll between the leak details, and the leak summary and emissions estimates for the town in which the leak is in :

You can use the search bar to search for leaks and addresses across all layers, and then constrain to specific layers. In the example below Highland Rd, Brookline is search for, and then results are limited to just National Grid Boston Gas layers :

Data in layers can be selectively chosen using filter expressions using the Attribute Tables button. The example below reveals just the open Grade 3 SEI leaks in the selected region. A layer is selected and then filtered by selecting leaks where the ‘Grade for mapping’ attribute is ‘G3SEI’. Filters persist until removed.

Estimated emissions information is included in pop-ups for towns and colored emissions layers for both towns and Boston neighborhoods is available:

Using the Basemap Gallery, you can chose a different base map if you prefer:

How the map was made

In 2020, HEET developed a new process for generating a high quality geocoded set of gas leaks data from the annual utility reports, and then sharing and mapping it. This dataset can be used for geospatial analysis in research such as the recently peer reviewed paper, An environmental justice analysis of distribution-level natural gas leaks in Massachusetts, USA, by Dr Marcos Luna and Dominic Nicholas. In addition to being used to create this map, the data can be used in any mapping platforms that can consume geocoded data. For example, in 2021 HEET collaborated with the Town of Salem to develop its own Understanding Natural Gas Leaks portal.

The process in overview is as follows:

  • Each March, Annual Service Quality Report (ASQR) reports are obtained from MA DPU 
  • Leak data from these reports is reviewed, selected and extracted
  • Full leak addresses are constructed in preparation for geocoding which is the process of determining GPS coordinates and mapping addresses for each leak
  • The leak address data is geocoded using HEET proprietary software
  • All results are extensively checked, and warnings and errors are resolved
  • The final geocoded data is now ready for either sharing, or for use in map creation
  • Using standard GIS MA town boundaries and Boston neighborhood boundaries, intersection analysis is performed with the geocoded leaks to determine counts of repaired and open leaks in each MA town and Boston neighborhood. These results are also used in calculating emissions estimates.
  • We share this final cleaned and geocoded leaks data under a Creative Commons license. Please contact us directly if you want a copy of the data.

Leaks that could not be mapped

A very small number (27 out of 20,339 repaired and open leaks) of all reported leak locations could not be geocoded and mapped based on the reported addresses in the annual reports. Typically these were due to cross streets not intersecting and street names that didn’t exist.

Data Sharing

We share our geocoded leaks data under a Creative Commons license. Please contact us directly if you would like a copy.