At least, that's not what's going on in this widely circulated photo of a sinkhole filled with bright green ooze.

Here's where we figure out who the real infrastructure geeks are.

Last week, photographer Steven Reitz captured this photo of a sinkhole in Philadelphia that appeared to be filled with a Ghostbusters-esque green ooze. When the image exploded on Reddit, there was naturally some talk about sludge, slime, and pending mutations to the local population.

The explanation, depending on how you feel about wastewater systems, is cooler or less cool. The Philadelphia Water Department, according to NBC 10, uses harmless dyes to trace the connections of sinkholes underground, in an effort to detect their relationship with other underground water deposits. Neon green, obviously, is a particularly visible hue, though the department also uses red and blue.

Anything to get the people interested in water management, right?

Top image by Steven Reitz.

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