Ladera Ranch cancer investigation renewed by 20-year-old oil well warnings

Handwritten warnings discovered on 20-year-old documents have renewed concerns regarding a cluster of rare childhood cancers in Ladera Ranch, Orange County, California. The notes, appearing on a 2002 permit for the abandonment of a historical oil well, state: “This well is not to be built over without further considerations.”

The memos, believed to have been written by engineer Floyd Leeson, do not specify the reason for the warning or whether any subsequent precautions were taken. Between 2013 and 2024, at least six cases of Ewing sarcoma have been diagnosed in the community.

While residents have raised concerns regarding local landfills and pesticide use on school property, health officials continue to investigate potential causes. The California Department of Conservation suggested the notes might be a “clerical error,” though officials have not clarified why the documents specifically instructed that the warning be “put on final letter.”