My sister has a deck built prior to 1995, could be in the 70s or 80s, using non PT lumber. One deck board has some rot in the top, otherwise it seems to be sound, at the max it's 1" deep, 2" wide, 15" long. I really don't want to replace the board, rather just use some type of liquid to fill it. I was going to cut it out with a circular saw. Suggestions?