Yes, soilage is in the scrabble dictionary.

Is Soilage a word?

an act or instance of soiling. the condition of being soiled.

Is this word OK for scrabble?

"OK" is now OK to play in a game of Scrabble. The two-letter word is one of 300 new additions to the latest version of the Official Scrabble Players Dictionary, which Merriam-Webster released on Monday. ... Not all Scrabble players are OK with OK, however, especially at the game's highest levels.