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Coronavirus can lead to worsened cross-bore utility condition

Cross-bore is the unintended intersection of two utility lines. [STATEPOINT PHOTO]
Cross-bore is the unintended intersection of two utility lines. [STATEPOINT PHOTO]

Lifestyle changes in response to the coronavirus could turn an underground cross-bore condition — in this case, the unintended penetration of a sanitary sewer line by a natural gas line — into a potentially dangerous situation, but it can be avoided.

The situation is not uncommon, according to the Cross Bore Safety Association, with estimates suggesting that it occurs at an average rate of 0.4 cross-bores per mile of sewer line.

Cross-bores most frequently occur in association with “trenchless” methods of utility line installation. In other words, it involves installing a utility line without digging up the ground. The reasons for doing this typically involve minimizing surface disruption, increasing the speed of installation, and reducing costs.

The downside to this method is that historically installers have not been able to see when the installed utility line penetrates a sanitary sewer line. The immediate result is typically uneventful, until the affected sewer line becomes blocked.

As far back as 1976, there have been documented incidents of attempts to clear blocked sewer lines where there is an undiscovered cross-bore. The resulting rupture of the intersecting gas line by some mechanical device, like a root-cutter, allows gas to enter a home through the sewer where it is accidentally ignited, causing an explosion.

As the existence of cross-bores has become better understood, steps are being taken to eliminate existing cross-bores, and to prevent them from occurring at all. Still, many “legacy” cross-bores remain.

The coronavirus pandemic has had more people at home for long periods, which means more sanitary sewer use. The scarcity of toilet paper has people using alternative materials that are not designed to degrade in a sanitary sewer environment. The inevitable result has been more blocked sewer lines.

Experts advise putting only toilet paper into the sewer. And homeowners should make sure a plumber uses a camera to see any blockage before attemptiong to remove it.

To see what a cross-bore looks like, and to learn more about excavation safety, go to