A dedicated washout area should be sized for expected truck traffic, feature impermeable lining

https://super-wiki.win/index.php/From_Slurry_to_Safety:_Concrete_Washout_Management_for_Small_Projects

A dedicated washout area should be sized for expected truck traffic, feature impermeable lining, and provide safe access for vacuum trucks or pumps to remove accumulated liquids and hardened materials.