The chances are that the weld had cooled below the T1 temperature when the water was spilled, so there is little danger the base metal will be hardened. That is, it wasn't quenched from the austenizing temperature.

If you are welding on prequalified base metal that isn't quenced and tempered, the CE is "relatively" low, so the hardenability is relatively low. There is a slim chance the hardness is a major concern.

That being said, you can do some hardness tests on the area in question and compare them to welds that were not subject to the cooling effects of the water. If there is a significant difference, further investigation may be warrented.

You mentioned the weld wasn't completed at the time the water was spilled. Did they continue to weld over the area that was affected? If they did, the subsequent welding most likely tempered the area that was cooled by the water if it was hot enough to cause a change in hardness.

If the hardness of the affected area is significant, consider doing a localiized heat treatment if the member is in a critical area.

It is never a good idea to cool a weld quickly, but from a practical standpoint, I have taken A36 plate welded with E7018 and tossed it into a snow bank while it was still very hot (nearly red) and still had the bend straps pass the requirements of D1.1. Rest easy, these were not welder qualification tests, these were some experiments that I performed at different temperatures to see how sensitive the A36 is to rapid cooling. As I found out, the carbon content is low enough that the resulting hardness was not high enough to concern me. Was it harder? Yes, but not much different than the material that was allowed to air cool.

The higher the carbon equivalency, the more sensitive the base metal is to quenching, but most of the prequalified steels have relatively low carbon equivalencies. Hardening occurs when the metal is cooled from the austenizing temperatures (above 1330 F). Heating to temperatures below T1 (1330 F) will soften the steel. Rapid cooling will only affect austenite, that is, it there is retained austenite at the temperature when the water was spilled, it may have transformed to martensite, but I doubt there was much in the way of retained austenite unless the water was spilled as the welder "broke" his arc, because the weld cools to temperatures below T1 almost immediately.

Best regarts - Al

You could always do the math on say the quenching ability of 8 oz of water on metal. Simply put I doubt there is a big enough heat capacity of so little water to greately affect hardness.
It takes quite a bit of water to cool metal especially of thicker sections