Here's what I would do, put it in your bathtub, then fill with hot water from the tap. Let it sit for an hour or so, then scrub it to get any dirt or loose debris off of it. Drain the bathtub and I say you're good to go for putting it where you want. If there was anything bad in/on the wood, the hot tap water will kill it. Plus, doing this will tell you if it sinks or not. If it doesn't, well, you have some more work ahead of you.