Be alert for cross bores

Welcome to National Grid’s Tips of the Trade. National Grid is committed to your safety and these tips are intended to help you work safely near our facilities. Please review these tips with your coworkers at your tailgate or toolbox meetings before work begins.

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Call before you clear a sewer clog or blockage

Some sewer laterals may have natural gas pipelines intersecting them. So before clearing any clogged sewer or drain lines, it’s critical that you contact National Grid to ensure you can proceed without the risk of puncturing a natural gas line. Please call our dedicated 24-hour emergency/dispatch number at National Grid.

How natural gas lines intersect sewer lines

National Grid uses horizontal directional boring to install natural gas lines underground beneath streets, driveways and mature trees. This approach is common in the utility industry because it causes less environmental disruption than open digging. National Grid currently uses techniques to detect sewer lines during directional digging. However, because many older sewer lines are not easily identifiable, in the past we may have unintentionally bored our gas lines directly through sewer lines in what are known as “cross bores.”

Know the dangers

A cross bore in a sewer lateral will impede flow and lead to eventual blockage. A worker who attempts to remove the blockage can accidentally cut the gas line and cause a dangerous release of natural gas. The resulting loss of service may not be immediately apparent. Gas can migrate undetected through the lateral and concentrate in sewer lines and nearby structures, causing a potential hazard.

Take these steps to work safely:

• Before clearing. Always call National Grid before you clear. We will determine if any conflicts exist between our natural gas lines and the blocked sewer line. If we detect a conflict, we will notify the customer and repair/reroute the gas line within 14 days at no cost.
• During clearing. Play it safe and always proceed as if a cross bore might be present. As you go, feel for resistance that does not resemble a tree root or other common obstruction. Natural gas utility lines are typically plastic. If you must use a cutting tool, look for yellow or orange plastic on the blades when you withdraw it. Watch for bubbles escaping from the entry point of the cutting equipment or toilet and/or use a combustible gas indicator (CGI) or other gas detection equipment, if available.
• If you suspect a gas leak. Immediately warn all inhabitants and evacuate the area. Do not use a flame or anything electrical, as a spark could ignite the gas. From a safe location call 911 and National Grid immediately.

Would you like to know more?

Additional overhead and digging guidelines, case studies, instructional videos and training tools can all be found, at no charge to you, on National Grid’s e-SMARTworkers website.

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For more contractor safety information, visit ngridsafety.com.

Call 811 or enter an online request at least 72 hours before digging in Massachusetts and Rhode Island, and at least 48 hours in New York, excluding weekends and legal holidays:

• MA & RI: digsafe.com
• Upstate NY: digsafelynewyork.com
• Metro NY, Long Island & the Rockaways: newyork-811.com