SEATTLE Puget Sound Energy (PSE) will spend the next several years trying to find gas line installation problems that can lead to deadly explosions.

In thousands of cases nationwide, gas line installers accidentally punctured sewer lines with directional drill bits, then ran the gas lines through the sewer. It s called a cross bore and it usually never results in a problem.

But Duane Henderson, PSE s Manager of Gas System Integrity, said if a plumber or do-it-yourselfer tries to clear a clogged sewer line with a common cutter tool, they can unknowingly sever the gas line. Gas can then travel up sewer lines and into homes or businesses.

The structure can fill up with gas and if it finds an ignition source, then we have some serious damage, said Henderson.

Several people have died in explosions and fires caused by severed cross bores in several states. There have been no explosions in Washington state and PSE wants to make sure it doesn t happen with any of their lines.

They have spent just one year inspecting their 24,000 miles of pipes and have already discovered more than 500 cross bores. They will spend many more years looking for them and will dig up and repair each one they find.

Henderson explained that, unlike metal pipes or tubes carrying electronic or communication wiring, older clay or plastic sewer pipes will not show up on above ground sensors. Workers used to dig ditches and lay in the gas lines so they could see sewer lines and avoid them. Today workers use directional drilling techniques to bore holes for the gas lines underground. If they cut through sewer lines, nobody sees it.

PSE is sending camera-equipped robots into sewer lines that will detect cross bores. It s expensive and time consuming, but PSE said they know the problem exists on their system. Since cross bores have caused death and destruction in other states, it s become a priority to find and remove them.

See PSE s cross bore advice for homeowners and plumbers at this link:

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