It was a chemical to speed up grout curing. I don’t know which one. I looked up a few and they were corrosive petrochemicals with like 20-letter-long names and an acute health exposure rating of 4 on the MSDS. They also didn’t provide PPE or instructions on what PPE was necessary. And have you ever gotten any significant amount of gasoline on your skin? It burns and it is not safe. Here’s a list of chemicals in common gasoline mixtures: Gasoline, Toluene, Hexane, Xylene, Octane, Ethanol, Trimethylbenzene, n-Heptane, Pentane, Cumene, Ethylbenzene, Benzene, n-Hexane, Cyclohexane.
Even if it was just the water in the tunnel — how about you try 8+ hours of heavy work in steel toed boots with damp feet, let alone standing in ankle deep water filled with corrosive chemicals. Even standing still in clean water, your skin basically turns to paste after not too long.
With the way the job market is trending in tech, you might have the opportunity to find out one day while someone sitting in a Herman miller chair in a climate controlled office building dismisses your pain as petty griping.