My husband worked for the local oil company for many years and I asked him what he thought. He said if they had a spill,no matter how small, the soil HAD to be dug up. Then it would have been incinerated. He thinks digging up the soil would be a good idea so your chickens dont ingest it. He isn't sure how you yourself would dispose of it. He only knows what his company did and that was take it to a professional to be incinerated. But he said he would for sure get the kero out. It will kill your birds if they ingest it, he has been on clean ups where full sized German shepards have died from ingesting small amounts. He said make sure you dig it all out of the ground.. no matter how deep. It will be rising back out. No matter what. They had to do all kinds of stuff when there were spills because of the EPA and regulations.