Natural Gas Pipeline Integrity and Maintenance

We're always working to keep you safe. Our comprehensive maintenance and inspection program, as well as an effective leak management program, exceeds the requirements of federal and state pipeline safety regulations.

An Eversource employee inspecting a home in the Merrimack Valley.Our leak survey program includes:

  • Semi-annual Surveys – High-pressure distribution lines and critical infrastructure pipes are surveyed for leaks twice a year. High-pressure lines are also patrolled an additional two times.
  • Annual Surveys – In business districts, we conduct annual leak surveys over all gas distribution mains. Surveys are conducted from vehicles or on foot.
  • Winter Survey – When cold weather and frost are prevalent, we survey all cast-iron mains on a 10-day cycle. The surveys continue until warmer weather returns.
  • Tri-Annual Surveys – Every three years, we survey pipelines exposed to the atmosphere, including company-owned piping inside customers’ buildings. We meet or exceed state or federal regulations, which require surveys every three years on some types of pipelines and every five years on others.

In accordance with federal regulations, we test and inspect gas meters and associated piping to monitor corrosion and detect potential leaks before they become a hazard.

Pressure on the gas distribution system is maintained by specialized equipment positioned in strategic locations throughout the system.

At each location, additional over-pressure protection equipment monitors and limits pressure. We also monitor system pressures 24/7 at our natural gas control centers.

Natural gas procedures, technology and best practices

Pipeline Integrity Management Plan

We are committed to continually improving the safety and reliability of our natural gas pipelines.  

In conformance with federally mandated regulations issued by the U.S. Department of Transportation's Pipeline Hazardous Materials Safety Administration, Eversource has implemented a Transmission Integrity Management Program for our transmission pipelines. A Transmission Integrity Management Program is a comprehensive, systematic process for evaluating and reducing risks to pipeline safety. This is achieved by:

Identification and Risk Assessment of Threats to Pipeline Safety

 Construction records, operating history, maintenance records, and environmental data are integrated and evaluated to identify conditions or hazards that could negatively impact the integrity of pipelines and to understand the severity of the risk posed by the threat.  Risk assessment is an analytical consideration of the risk factors that promotes an effective allocation of resources for appropriate prevention, detection, and mitigation activities.

Identification of High Consequence Areas

 High Consequence Areas are locations with high population density, difficult to evacuate facilities such as hospitals and schools, and locations where people congregate such as churches, office buildings, and recreational areas. Transmission pipelines that are near these locations are prioritized for enhanced pipeline inspections. Eversource consults with public officials in identifying these locations.

Prevention, Detection, and Mitigation Activities

 Periodic field inspection of transmission pipelines are conducted within regular intervals to proactively discover locations where the pipeline could be corroding or damaged. Pipeline flaws that are discovered are repaired before they can impact the safety and reliability of the pipeline.

Prevention and mitigation activities are selected to address the unique conditions impacting each pipeline.

Examples of these activities include: 

  • Patrolling/surveying the pipeline corridor to look for indications of abnormal conditions such as missing pipeline markers, construction activity, potential gas leaks, right of way encroachments, changes to the terrain due to rain/flooding, or other issues detrimental to the safe operation of the pipeline
  • Monitoring excavating activity of third parties in the vicinity of our transmission pipelines
  • Developing improvements to emergency response
  • Communication of pipeline safety information to public officials, emergency responders, the general public, and employees
  • Replacement of aging pipeline facilities with state-of-the-art facilities

Continuous Safety Improvement

As the Transmission Integrity Management matures, our knowledge of the conditions of our pipelines is enhanced. We use this knowledge to continually evaluate the effectiveness of risk reduction activities and our decision making processes. We evaluate the integrity management program for areas of success and looks for other areas on our pipeline system where improvements can be made. Our prevention, detection and mitigation activities evolve to ensure continual improvement in the safety of the transmission pipelines. Eversource actively seeks the use of new technologies and adopts best operating practices to improve the effectiveness of the program.

To view the location of natural gas transmission pipelines operated by Eversource and other companies, visit the U.S. Department of Transportation National Pipeline Mapping System.