The first step in the supply and operation of a gas station is delivering the product on site and transferring it to the (typically) underground storage tanks (UST as it is commonly known). This is a process that involves rules and devices in place to minimize and mitigate any spillage of product that will occur.
One such device is the Spill Bucket. A receptacle embedded in the ground at the end of the main drop tube, its purpose is to capture any product that might remain in the truck's hose once the delivery of the product is concluded and the hose is disconnected from the fill adapter cap. The product captured in it then can be flushed inwards to the storage tank via an internal valve.
The following video illustrates this device: