Just dump it in the grass, really, it won't hurt it. Hell, I still dump my drain oil down the sewer in front of my house. There's a nice looking image of a large fish cast into the top of the sewer grate. I don't know what that's all about, but all the grates on our street have them. Mine's the only one on the block that's not all rusty looking. I guess all the oil I've dumped on it over the years has kept it nice looking. That's the kinda guy I am. I like keeping things nice looking. Good luck with your project.