A 2021 Leak Survey of Washington DC

Massachusetts leads the nation in terms of public transparency around gas leaks on the pipes under our streets.  The gas utilities regularly report location, status, grade and other information for every gas leak in their territories. This transparency is critical to understanding the current prevalence of gas leaks, their geographic concentration, and implications for the climate and safety of residents. However, Washington Gas—the gas provider for all of Washington DC—is not required to publicly report such information.

From April through June, 2021, Gas Safety Inc president Bob Ackley, Boston University Professor Nathan Phillips and HEET Director, Dominic Nicholas, collaborated on a gas leak survey of residential neighborhoods in Washington DC and identified 3,346 leaks on the gas distribution system. These results are being used by DC’s Department of Energy and Environment (DoEE) to help inform policy development for a strategic transition toward decarbonized heating and electrification.

Note that this survey does not grade the leaks for safety or hazardousness. Washington Gas uses their site‐specific criteria for identifying safety risks.

This project provides an excellent example of making the invisible visible – making leak locations transparent – and using that information as a lever for catalyzing change.


Leaks from natural gas infrastructure contribute to climate change, create potential safety risks, degrade air quality, damage trees and waste ratepayer money. Identifying the locations of leaks can help quantify and reduce greenhouse gas emissions effectively, and can inform policy development to allow for a strategic and equitable transition to decarbonized heating and cooling.

Most gas leaks in the distribution system are associated with old, leak‐prone pipes,.Some pipes over a century old can be found, especially in older cities. In 2021, DC had the highest proportion (39%) of leak prone pipes and the second highest proportion of leak prone services (21%) in the country (according to PHMSA).

In this study, Gas Safety Inc surveyed methane emissions along 713 miles of road (this is the total length of the road, regardless of the number of lanes) using a high‐precision vehicle‐mounted methane analyzer. In this survey each road was driven twice to verify stationary repeatable leak locations to eliminate false positives. The project team jointly developed a new and improved algorithm to analyze the raw survey’s geospatial emissions data and we used it to identify 3,346 leaks attributable to natural gas pipes – or about 5 leaks per centerline mile. We surveyed surface methane emissions on public roads in selected residential areas serviced by gas:

Figure 1: Yellow areas indicate residential areas serviced by gas and surveyed for methane leaks along public roads.

The survey covered approximately 99% of the public roads in these residential areas:

Figure 2 : Roads Driven and surveyed for methane leaks overlaid on the yellow residential areas depicted

Methane can come from sources other than natural gas pipelines, including broken sewer mains, landfills, and wetlands. Therefore, Gas Safety Inc verified leaks were associated with gas pipes by selecting forty leaks representing small, medium and large methane readings and confirmed that they all were close to gas mains, valves or service lines.

Results Map

Use the map to explore the analyzed leak locations, noting the following :

  • Readings obtained in this survey are not intended to serve as indicators of safety or hazardousness. Safety determinations are made by Washington Gas using their site‐specific criteria for identifying safety risks.
  • Leaks in the map represent a snapshot in time as covered by the duration of the surveying (April through June 2021).
  • Leaks may have been repaired or new ones developed since the surveying.
  • Leaks are on mains or service lines under streets, not inside buildings.

More Information

The original project report provided to the , “2021 Fugitive Methane Emission Survey of the District of Columbia, For the District of Columbia Department of Energy and Environment October 31, 2021”, can be found here.

Data Sharing

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