2100 PSIG (woodbine) 3-15-19
Why do some of Sunoco’s recent engineering drawings for the 16-inch pipeline show far higher design pressure than previously? They now show “2100” PSIG”. (“PSIG” stands for “pounds per square inch gauge”. The “gauge” part means that the pressure is measured relative to normal atmospheric pressure, which is 14.7 pounds per square inch. So “2100 PSIG” is equivalent to 2114.7 PSI.)

Some of Sunoco’s recent engineering drawings indicate a much higher pressure than previous drawings did. Increasing the pressure in the Dragonpipe (Mariner East pipeline system) would be an important change for several reasons. For Sunoco, higher pressure is a way of forcing more product through a pipeline of a given diameter. But higher pressure also makes leaks more likely; and, if a leak occurs, the amount of product leaked and size of the blast zone would be greater.

That’s why it is alarming to learn that Sunoco has been indicating higher pressures in its recent engineering drawings, submitted to the DEP as part of the permitting process. Typically, these drawing have shown “1480 PSIG” as the “internal design pressure” for the pipe, but some now show “2100 PSIG. You can see an example of this notation on the final page of this document, filed with the DEP.

This change, if it is real, is a big deal. It amounts to a 42% increase in pressure. Based on an informal check with an industry expert, such a pressure would be unusually high, even with brand new pipe.

Perhaps the more likely explanation is that this is a typographic error, and the real design pressure is still 1480 PSIG. But if so, this is unforgivable sloppiness. Pipeline pressure is a critical factor in pipeline safety. To misstate the pressure by 42% in a regulatory filing speaks of a very unprofessional engineering process.

Either way—covert design pressure change or typo—this doesn’t speak well for the way Sunoco is dealing with this project.

I am grateful to the sharp-eyed regulatory team at Clean Air Council for first noticing this and bringing it to my attention.