When we put our pit in we have a small drop off to the side so water running in wasn’t a problem. I just sloped a slight grade around the pit. To handle the water filling in, I dug a drywell. I went as deep as I could get with a post hole digger, 8" diameter about 4’ down the center of the pit. I filled that with gravel and sand. Our soil is heavy clay. On top of that is an old carpet to keep the next 4-6 inches of sand from falling in. This is the base of the pit. My pit is about 6" poured cement that ends at ground level with a 6" cement lip around to keep the grass from growing and burning too close. The lid is a very large trash can lid that happens to be close to the correct size.