I know a lot of people were concerned about the underground fire & explosion last Saturday at 23rd & Pike. This morning I got in touch with the very helpful Peter Clarke at Seattle City Light, and he filled in a few details about the incident (and big kudos to City Light for being responsive to a lowly neighborhood blog such as this – wish we were so lucky with other agencies).
I’m sure you’ve seen the big electrical facility behind the 70’s style brick wall along 23rd, between Pike & Pine streets. That is the East Pine Substation, and it takes the high voltage that comes into the city from the Bonneville Power Administration and distributes it to the eastern part of town, stepping it down from 230,000 volts to 26,000 volts in the process. The substation serves the area roughly between the ship canal and I-90 on the north and south, and Lake Washington & I-5 on the east and west.
The underground vault where the explosion occurred contains multiple feeder lines that take the power from the substation and send it out to the various neighborhoods on this side of town. The wires carrying that power are in close proximity to each other, and insulation is used to keep the wires from touching and causing short circuits. But on Saturday some of that insulation failed for unknown reasons (I’m guessing it’s just old), causing a short. Due to the high voltage in those wires, a short can release an immense amount of heat very quickly, causing the loud explosive sounds and the resulting fire. Circuit breakers quickly detected the fault and tripped, cutting power to a big part of the neighborhood.
One of the risks with electrical equipment is the presence of PCBs. It’s a nasty, toxic, potentially cancer-causing chemical that was used to cool electrical equipment up until the point when it was banned by the EPA in the 70s. But older equipment still contains PCBs and can pose an environmental & health hazard if it leaks out or the equipment containing it is damaged.
The good news here is that there isn’t any equipment in the underground vault that contains PCBs. And while there are 3 transformers in the neighboring substation that do contain “very small amounts” of PCBs, they were not damaged or otherwise affected by the underground incident. City Light also assures me that they have active monitoring and spill prevention/response plans for the older equipment in the substation that contain PCBs.