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TIPS OF THE TRADE
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Be Alert for Cross Bores
Review these tips with coworkers at your tailgate or tool box meetings before work begins to help avoid potential hazards when working near natural gas pipelines or other utility lines.
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Please help us improve our safety tips to meet your training needs. Take our two minute survey.
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Natural Gas Lines May Cross Sewer Lines
NW Natural installs some gas lines using a trenchless method that drills horizontally through the ground. Many utilities use this method because it minimizes damage to pavement and landscaping. However, if a sewer line wasn’t mapped or installed with tracing technology and couldn’t be located on the property, it’s possible that our drilling equipment crossed through it. Gas lines that have been drilled directly through sewer lines are known as “cross bores.”
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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 could cause the 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.
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Call Before You Clear
Cross bores are rare, and now we are able to prevent them. When trenchless gas line installation is complete, we scope the gas line with a video camera to ensure it doesn’t cross the sewer line. We are also inspecting sewer lines street-by-street throughout our territory to identify cross bores. Nevertheless, there is a rare chance that you may encounter a cross bore when clearing a sewer blockage, so always take the following precautions:
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- Before clearing.If you own or can obtain access to an inline camera, use it to assess the blockage before attempting to clear it. If the camera view is obstructed due to the clog, vacuum it out first.
- If a camera is not available, run a hydro-jetter through the sewer line to clear it. If you sense resistance that does not resemble a tree root or other common obstruction, do not force it and do NOT use a cutting tool. Stop immediately and call NW Natural.
- If a cross bore is suspected, call NW Natural at 800-882-3377. We will respond quickly, and if the gas line crosses through the sewer line, we will repair the sewer line and reroute the gas line at no cost to the property owner.
- After clearing. Natural gas pipes are typically colored plastic. If you have used a cutting tool, look for plastic on the blades when you withdraw it. Watch for bubbles escaping from the entry point of the clearing equipment or toilet and/or use gas detection equipment, if available.
If You Hit a Gas Line
Assume the situation is dangerous. Immediately warn all inhabitants and evacuate the area. Do not use matches or lighters, start an engine, or operate any electrical device (even a phone), as a tiny spark could ignite leaking gas. From a safe location, call 911 and NW Natural immediately at 800-882-3377.
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Free Online Excavation Safety Training
Now being offered — Excavation Safety 101.
This online course will strengthen your understanding of common safety issues as well as educate you on laws and best practices for safe excavation. The course is designed to take a minimum of 50 minutes to complete, although there is no maximum time limit. Successful completion of Excavation Safety 101 with a 100% grade will earn you a certificate, proving that you've completed the course and giving you a way to earn continuing education credits.
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The course is available to anyone. Simply create an account, enroll in the course, and complete the material at your own pace.
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NW Natural
Emergencies
800-882-3377
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