Cancer cluster at California ranch leads back to an abandoned well after 20-year-old warning surfaces

A well abandoned nearly 20 years ago below what is now Orange County’s Ladera Ranch in California has become a topic of discussion after residents raised concern that something in the area is causing cancer among children, adults and pets. Six children in the suburban community in southern California have been diagnosed with Ewing sarcoma over 11 years, a rare cancer. Many residents believe have been caused by herbicides and pesticides.

"We’re very concerned about pesticides that are being sprayed all around the community,” a woman named Liesl Heidt told ABC7. Others say a landfill site in the area could also be the reason. Besides children, many adults and pets are also suffering from cancer. The cases have left authorities puzzled even as the American Cancer Society said "no known lifestyle-related or environmental causes" have been identified.

Old warning notes about the well surface

Now, 20-year-old memos warning about the site and an oil well have surfaced, raising further concerns about what could have caused the cancer cases. The New York Post reported that the ominous notes appear twice in pencil markings on the Department of Conservation permit, and say, "This well is not to be built over without further considerations."

State oil and gas supervisor William F Guerard Jr, acting state oil and gas supervisor Kenneth Henderson and deputy supervisor RK Baker signed the final report after the well was sealed on February 26, 2002. The memos warning that no structures should be built above the well were reportedly written by engineer Floyd Leeson. They do not reveal why such a warning about the well was issued.

Notes about the California well could be ‘clerical error’

Another note had an arrow pointing at the message, with the words "Put on final letter." Los Angeles Times talked to Henderson and asked about the reason for the caution note. He could not recall why such a warning was issued, although he believes the way the well was sealed might not be "up to the current standards." Meanwhile, the Department of Conservation told the outlet the notes could have been a "clerical error."

The six cases of Ewing sarcoma were reported between 2013 and 2024. There is nothing to prove that the abandoned well could have led to Ewing sarcoma cases in Ladera Ranch. There is still no scientific consensus on what causes the rare cancer that primarily affects bone and soft tissue.

Warning about the well should be investigated

Karen Lincoln, director of the Center for Environmental Health Disparities Research at UC Irvine, told The Post that it wouldn't be right to assume the well was hazardous based on the notes, although they should not be completely dismissed. "If an engineer specifically raised a concern about building over a well, it’s reasonable to ask what that concern was and whether it was resolved before homes were built over or around it," she said.

The concerns could have been about the "condition of the well, how it was sealed, the materials used to seal it or the possibility that gases or other substances could move through or around the well."

Karen added that abandoned wells can become a passage for gases or other substances underground to move towards the surface. However, something being "a potential hazard and an actual exposure" are different things.