Officials were alerted more than two decades ago that an abandoned oil well in Ladera Ranch, California, should not be built upon without further consideration, according to unearthed records. These handwritten notes on official documents have intensified fears surrounding at least six cases of Ewing sarcoma diagnosed in the community between 2013 and 2024.
The notes, written in pencil on the Department of Conservation permit for the abandonment of a historical oil well, state: "This well is not to be built over without further considerations." The documents were signed off on February 26, 2002, by state oil and gas officials. A separate notation indicated the message should be "Put on final letter."
Engineer Floyd Leeson appears to have authored the memos, which do not specify the reason for the caution or whether any further assessments were conducted. Kenneth Henderson, a former acting state oil and gas supervisor, told the LA Times that he did not recall the specific context but suggested the well's plugging might not have met current standards.
The Department of Conservation offered that the notes could have been a clerical error, but did not elaborate on why they were marked for inclusion in a final letter. There is currently no direct evidence linking the abandoned well to the Ewing sarcoma cases, and the exact causes of the cancer remain under investigation by health officials.
Karen Lincoln, director of the Center for Environmental Health Disparities Research at UC Irvine, advised against dismissing the notes. "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. Lincoln noted that concerns could involve the well's condition, sealing integrity, materials used, or the potential for gases or other substances to migrate.
Abandoned oil wells, if not adequately sealed or if their seals have deteriorated, can potentially create pathways for underground substances to reach the surface. Lincoln explained that such substances could include methane, hydrocarbons, and benzene, some of which are known or suspected carcinogens, though not specifically linked to Ewing sarcoma. Potential exposure routes include air, soil gas, and groundwater.
Ladera Ranch, a community of about 24,000 people in Orange County, began development in the late 1990s on land that was formerly part of a cattle ranch. Construction of the first homes started in 1999, with many old oil wells being sealed as development progressed.
Residents have been seeking answers regarding the cluster of Ewing sarcoma cases, an exceptionally rare cancer that affects bones or soft tissue, disproportionately impacting children and young adults. A UCLA study identified geographic areas in Southern California with a high concentration of these cases, prompting calls for further investigation into environmental risk factors, though researchers cautioned that causality could not be inferred.
Parents of affected children have expressed their desire for clarity. Dustin Matteson, whose son Brody died after being diagnosed, stated that residents deserve to know if environmental factors contributed to the cases. DeAnn Kling, another parent, believes potential contributing factors could range from pesticides and water quality to the homes themselves and the ground beneath them.
The California Geologic Energy Management Division (CalGEM) generally discourages building over sealed oil wells to ensure continued access and minimize leakage risks. While wells plugged to current standards are considered less likely to leak, CalGEM acknowledges there is no absolute guarantee.