Stuck on Grind off bird poo mission

On mission Finer Grind Tour 2: Bag of tricks. The one with Grind off bird poo /12 collect trash /5 and 5-0 grind /2. I need to grind off bird poo, I'm at 11/12. Not sure where the location is I have been playing for hours and lost it, cant find it. Anyone know where the location is??