Storing raw foods in the wrong order is a classic cause of cross-contamination. These answers explain the correct top-to-bottom cooler order and the Food Code rule behind it. Primary source: U.S. Food and Drug Administration.
From top to bottom the order is: ready-to-eat food on the top shelf, then raw whole seafood, then raw whole cuts of beef and pork, then raw ground meat and ground fish, and raw poultry on the bottom. The logic is that items are arranged by their minimum required cooking temperature, lowest at top and highest at bottom, so that if anything drips, it drips from a food that needs less cooking onto one that will be cooked hotter, never the reverse.
It prevents cross-contamination by drip. If raw poultry sat above ready-to-eat salad, juices carrying pathogens like Salmonella could drip onto food that will be served without further cooking. FDA Food Code 3-302.11 requires raw animal foods to be separated from and stored so as not to contaminate ready-to-eat food and other raw animal foods. Ordering by cooking temperature ensures that any drip lands on an item that will subsequently be cooked to a temperature high enough to destroy the transferred pathogens.
FDA Food Code 3-302.11 is the core rule. It requires separating raw animal foods during storage from ready-to-eat food and from other raw animal foods that require different final cooking temperatures, and storing them to prevent cross-contamination, which in a shared cooler means keeping the higher-cook-temperature items below. The specific cooking temperatures that set the order, such as poultry at the highest required temperature, come from the cooking requirements in Food Code 3-401.11.
On the bottom shelf. Poultry has the highest minimum internal cooking temperature of the common raw proteins, so it goes lowest to ensure that if it drips, nothing below it is contaminated, and anything it might drip onto is itself raw meat destined for thorough cooking. Storing poultry at the bottom is the single most important storage-order habit, since undercooked or cross-contaminated poultry is a leading source of foodborne illness. This ordering is driven by FDA Food Code 3-302.11.
Yes. Ready-to-eat foods, including washed produce, cooked items, deli meats, and anything served without further cooking, go on the top shelf, above all raw animal foods. Because they receive no additional cook step to kill pathogens, they must never sit where raw-meat juices could drip onto them. FDA Food Code 3-302.11 requires this separation. The only nuance is that commercially packaged, sealed items are protected by their packaging, but the safe default is to keep ready-to-eat food highest.
Raw ground meat and ground fish are stored below whole cuts of beef and pork but above raw poultry. Grinding mixes surface bacteria throughout the product and raises its required cooking temperature above that of an intact whole cut, so ground products sit lower in the cooler than whole muscle cuts. This mirrors the cooking-temperature hierarchy in FDA Food Code 3-401.11, which the storage order in 3-302.11 is designed to protect against cross-contamination.