timothy wrote:Ok. Get the lid to go with it to keep weather out. Build up sloping grade around it. Line it with heavy plastic.
My appologies for not adequately explaining the "flange" concept. I used that term to mean a part that will flare outward from the main container while leaving the main container open to the sky. This would make the apparent surface area of the tar pit much larger than the actual container. This is important because the material to fill the container is expensive. Because the "flange" portion will also have "tar" in it there must be a reliable seal between the flange and container. Otherwise the tar will leak out. When the pit is not in use there must also be a cover to keep out rain and other debris. This cannot be a flexible plastic sheet because that would allow puddling. I will be quite astonished if what is needed can be purchased off the shelf.