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 presence of several stainless steel vats on the job site has led some to surmise that, as part of this Golden Age for Beer in Bernal Heights, a new microbrewery is under construction there, with skyline views that will pair nicely with a full-bodied IPA. 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, like that popular place in Japantown.
Suffice to say, such rumors are false and unfounded. Instead, the project on Bernal Heights Boulevard is part of a PG&E effort to reposition a high-voltage electric transmission line that’s buried under the street.
Neighbor Sam wrote about this process a few years ago after spotting a similar operation underway in Los Angeles. Here’s his basic explanation:
It turns out they have a problem with an underground wire. Not just any wire but a 230 KV, many-hundred-amp, 10 mile long coax cable. […]
The cable consists of a copper center conductor living inside a 16 inch diameter pipe filled with a pressurized oil dielectric. Hundreds of thousands of gallons [of mineral oil] live in the entire length of pipe. Finding the fault was hard enough. But having found it they still have a serious problem. They can’t afford to drain the whole pipeline – the old oil (contaminated by temporary storage) would have to be disposed of and replaced with new (pure) stuff which they claim takes months to order (in that volume). The cost of oil replacement would be gigantic given that it is special stuff. [..,]
That’s where the LN-2 [liquid nitrogen] comes in. An elegant solution if you ask me. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant (asbestos-looking) blankets filled with all kind of tubes and wires, feed LN-2 through the tubes, and *freeze* the oil. Viola! Programmable plugs! The faulty section is drained, sliced, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed.
That’s what’s happening on Bernal Hill right now. Only, the issue here isn’t a fault in the line. Instead, workers at the site tell Bernalwood that PG&E is re-positioning the underground electric line to bypass a sewer upgrade The City recently installed along Folsom Street.
So on Bernal Hill, a contractor is using liquid nitrogen to freeze a segment of the 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, and in-between, a third crew is repositioning the power line to avoid the new sewer pipes.
So now you know.
PHOTOS AND VIDEO: Telstar Logistics