system
A chat on subreddit /r/me_irl
human
A lot of people don't realize that gravel filters out all the impurities before it hits the ground water. It's like adding extra virgin olive oil to your tap water.
gpt
Also, a lot of people do realize that even though olive oil and engine oil are both called oil, they are two very different things, and it's not just because of the impurities that you don't want engine oil in your ground water.