Utility Deploys Deep Freeze Technique In Bernal Hill Construction

Utility Deploys Deep Freeze Technique In Bernal Hill Construction

Photo: Bernalwood

By Todd Lappin - Published on July 24, 2017.

There’ve been many questions and much speculation about the big construction project that’s gobbled up a whole lane of Bernal Heights Boulevard on the north side of Bernal Hill.

It’s quite a scene:

The frosty mist emanating from a pipe has caused others to wonder if the site will become a pop-up location for one of those trendy, liquid-nitrogen ice cream stands.

Suffice to say, such rumors are false and unfounded. The project on Bernal Heights Boulevard is part of a PG&E effort to reposition a high-voltage electric transmission line buried under the street.

Workers at the site told Bernalwood that PG&E is moving the underground electric line to bypass a sewer upgrade the city recently installed along Folsom Street.

The contractor is using liquid nitrogen to freeze a segment of mineral oil that functions as an insulator for the high-voltage electric line. The frozen segment acts like a cork to seal off the mineral oil backed up in the rest of the very long electric line.

There’s another liquid nitrogen site farther north on Folsom that corked the other end of the line; in-between, a third crew is repositioning the power line to avoid the new sewer pipes.

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