The debate unfolding in California over idle or abandoned oil wells located near schools, parks, homes, and care facilities risks drifting toward a familiar misconception: confusing proximity with danger.
No parent or caregiver wants to imagine industrial infrastructure posing a risk near places meant to protect vulnerable people. There are hazards associated with old oil wells, but steps can be taken to mitigate them and accommodate redevelopment and vibrant new land uses on sites with existing oil wells.
Land scarcity and housing demand are driving redevelopment into former oil fields, some of which appear as vacant lots surrounded by urban development. Redevelopment of these lands can unlock property value and support economic development, while protecting our health by mitigating the impacts of abandoned oil wells before and during the development process. In addition, various funding sources are available through multiple federal and state agencies.
Addressing Abandoned Oil Wells in California
California contains thousands of legacy oil wells embedded in developed cities as well as rural lands used for agriculture or environmental preservation (i.e., wetlands). California’s challenge is not simply where legacy wells are located, but how they are evaluated, managed, and regulated as land use changes.
San Diego County has far fewer oil and gas wells than counties such as Los Angeles, Ventura, Kern, and Santa Barbara. That difference is due to geology and the presence of petroleum reservoirs inherent in these areas.
Senate Bill 1137, enacted in 2022, created health protection zones around homes and other sensitive land uses in areas where idle or abandoned oil wells are present. The law reflects a long-overdue reckoning: California is far more urban today than when many of these wells were drilled decades ago. Mitigating any risk to the environment, public health, and safety requires technical clarity of when and how the wells were drilled, not just maps showing the location.
Idle and abandoned oil wells in California are not unregulated relics. Oversight falls to the California Geologic Energy Management Division, or CalGEM, which enforces detailed standards (California Public Resources Code [PRC] § 3208.1) for access to the well, wellbore integrity, and abandonment under state law.
CalGEM can require the well to be “re-abandoned” to modern standards—standards that are far more stringent than those in place decades ago. They emphasize verified cement isolation, groundwater protection, monitoring, and testing to confirm long-term integrity for redevelopment.
Development and Health Can Go Hand-in-Hand
Even in locations with disproportionately high numbers of abandoned oil wells, a strategic redevelopment project with qualified petroleum engineers or geologists (e.g., Pacific City in the City of Huntington Beach or the 2nd & PCH shopping center in the City of Long Beach) is successful. The due diligence team reviews historical well records (available from CalGEM), verifies well locations in the field, assesses vapor and methane conditions, and coordinates closely with regulators and local agencies using a systematic approach.
Where necessary, Vapor Intrusion Mitigation Systems (VIMS) are built into the project design. VIMS are proven to prevent toxic chemical vapors from contaminated soil and groundwater from entering buildings, thereby protecting indoor air quality. Done early during due diligence — before construction begins — helps identify potential hazards and addresses them, protecting public health and preventing costs from escalating.
Differentiating Wells and Funding
It is important not to treat all idle or abandoned oil wells the same. Most publicly available maps from CalGEM’s Well Finder show the different types of wells and the operator on record. Many wells remain the responsibility of active oil and gas field operators and are subject to idle well management plans, bonding requirements, and escalating plugging obligations under recent legislation.
Others are truly orphaned, with no viable operator remaining. For those wells, California has established a state-run orphan well program, which includes a process for safely plugging and abandoning wells and four funding sources. The sources are:
Ensuring Regulatory Enforcement
In February 2026, the Center for Biological Diversity highlighted sensitive land-use areas with vulnerable populations where oil and gas wells exist. Public awareness is essential, but the conversation cannot stop at cataloging proximity. The real challenge is ensuring that regulatory enforcement, redevelopment planning, and funding mechanisms are aligned to meaningfully reduce site-specific risk.
This requires collaboration among regulators, landowners, developers, environmental advocates, and local governments. It requires acknowledging uncertainty where it exists while recognizing the technical frameworks already in place. And it requires moving beyond headlines toward informed decision-making.
CalGEM recommends that engaging qualified professionals—those who understand CalGEM’s requirements and California’s regulatory framework—is critical to evaluating legacy wells safely and responsibly. The opportunity now is to apply those evaluations consistently, transparently, and early in the land-use planning process, so communities are protected and urban infill and redevelopment can proceed without unnecessary fear, delay, or oversimplification.
Finding the Appropriate Support to Minimize Risk
We recommend finding an engineering firm, preferably with a background in the petroleum industry and a successful track record in remediating brownfields and performing highly structured due diligence. Your engineer will likely rely on the expertise of a geologist or hydrogeologist, depending on the location. You’ll want more than a due diligence consultant; you’ll need, in states like California, a California-licensed professional petroleum engineer (PE) and a California-licensed professional geologist (PG). Evaluating risks is complex, and firms like SCS Engineers provide the expertise to assess the land, complete the required plug-and-abandonment process for the wells, and make properties valuable, sustainable, and useful again.
Author: Senior Project Manager and Geoscientist Tim Rathmann. Confer with Tim or an expert in your area at SCS Engineers, or reach Tim on LinkedIn.
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On July 24, the U.S. Environmental Protection Agency (EPA) proposed to designate five chemicals as High-Priority Substances for risk evaluation under the nation’s chemical safety law, the Toxic Substances Control Act (TSCA). If EPA finalizes these designations as proposed, the agency would immediately move forward with the risk evaluation process. According to the current Administration this step is consistent with a commitment to understand and address environmental and toxic exposures to ensure that every community has access to clean air and water while bolstering efforts to make progress on delivering environmental justice and tackling plastic pollution.
The five chemical substances EPA is proposing to designate as High-Priority Substances are:
EPA will accept public comments on the proposed designations for 90 days after publication via docket EPA-HQ-OPPT-2023-0601 at the Regulations.gov page. Upon publication of the Federal Register notice, supporting documents will also be available in the docket.
Chemicals Proposed as High-Priority Substances for Risk Evaluation
All five chemicals were selected from the 2014 TSCA Work Plan, which is a list of chemicals identified by EPA for further assessment based on their hazards and potential for exposure. In proposing these five chemical substances as High-Priority Substances for risk evaluation, EPA had to consider the chemicals’ conditions of use and production volume or changes in conditions of use and production volume over time, impacts to potentially exposed or susceptible subpopulations including children and workers, and the chemicals’ potential hazards and exposures. EPA also considered more specific criteria such as the chemical’s bioaccumulation and environmental persistence and whether the chemical is stored near significant sources of drinking water.
Vinyl chloride is used primarily in the manufacturing and processing of plastic materials such as polyvinyl chloride (PVC), plastic resins, and other chemicals. Many of these materials are used for pipes and insulating materials. This chemical was also involved in the Norfolk Southern train derailment in East Palestine, Ohio. Vinyl chloride is a known human carcinogen and can cause liver, brain, and lung cancer in exposed workers. Short-term exposure to vinyl chloride can also result in other health effects such as dizziness, nausea, and eye and skin irritation. Vinyl chloride exposure can also damage genetic material in cells, which can lead to numerous adverse health effects. In the 1970s, the White House Council on Environmental Quality and EPA officials raised serious concerns about the health impacts of vinyl chloride as an example when the Nixon Administration asked Congress to write a law to ensure chemicals were made and used safely, which led to passage of the “original” TSCA in 1976.
Acetaldehyde is used primarily in the manufacturing and processing of adhesives, petrochemicals, plastic and other chemicals, as well as intermediates for products such as packaging and construction materials. Acetaldehyde is a probable human carcinogen. Specifically, animal studies have shown that exposure to acetaldehyde can result in the formation of nasal and laryngeal tumors. Short-term exposure can also result in health effects such as irritation of the respiratory system and reduced heart function. Data further shows that acetaldehyde exposure can damage genetic material in cells, potentially leading to numerous adverse health effects.
Acrylonitrile is used primarily in the manufacturing and processing of plastic materials, paints, petrochemicals, and other chemicals. Acrylonitrile is a probable human carcinogen and can cause lung and brain cancer in exposed workers. Short-term exposure to acrylonitrile can also result in health effects such as eye, skin, and respiratory irritation. Long-term exposure can result in reproductive effects such as reduced sperm count and developmental effects such as slowed fetal growth.
Benzenamine is used in the manufacturing and processing of dyes and pigments, petrochemicals, plastics, resins, and other chemicals. Benzenamine is a probable human carcinogen and can cause bladder tumors and pancreatic cancer in workers. Long-term exposure to benzenamine can result in a range of adverse health effects such as difficulty in breathing, tumor growth in the spleen, and possible reductions in fetal viability.
MBOCA is used in the manufacturing and processing of rubbers, plastics, resins, and other chemicals. MBOCA is a probable human carcinogen. Specifically, animal studies have shown that exposure to MBOCA can cause liver and urinary bladder cancer. Short-term exposure to MBOCA can result in eye and skin irritation. Data further demonstrates that MBOCA exposure can damage genetic material in cells, potentially leading to numerous adverse health effects.
EPA Prioritization Process
Prioritization is the first step under EPA’s authority to regulate existing chemicals currently on the market and in use. EPA’s proposed designations are not themselves a finding of risk. If EPA finalizes these designations, the agency will initiate risk evaluations for these chemicals to determine whether they present an unreasonable risk to human health or the environment under the TSCA conditions of use (the way the chemical is made and used), which the agency is required to complete within 3-3.5 years. If at the end of the risk evaluation process EPA determines that a chemical presents an unreasonable risk to health or the environment, the agency must begin the risk management process to take action to eliminate these unreasonable risks.
EPA began the process of prioritizing these five chemicals in December 2023 and also announced that it expects to initiate prioritization on five chemicals every year, which will create a sustainable and effective pace for risk evaluations. According to EPA, the agency has continued to improve the prioritization process by investing in cutting-edge software to review more information earlier in prioritization. EPA has also implemented improvements to its systematic review approaches as recommended by the Scientific Advisory Committee on Chemicals (SACC) by incorporating additional data sources such as assessments published by other government agencies to identify potential hazards and exposures, clarifying terminology to increase transparency in the systematic review process, and presenting interactive literature inventory trees and evidence maps to better depict data sources containing potentially relevant information.
EPA has conducted a preliminary screening and technical review of large data sets to more efficiently identify relevant information for prioritization and risk evaluation and can easily flag information that may be useful to retrieve later in the risk evaluation process. As a result, EPA now has a head start on risk evaluations. At this proposed designation stage, EPA has a much fuller understanding of how these chemicals behave in the environment and their potential hazards and exposures than it had at this point in the process in the previous prioritization cycle conducted in 2019. That has also enabled EPA to make considerably more information available to the public a year earlier than occurred for the first 30 chemicals designated for risk evaluation under TSCA. The public will be able to see which studies and what information EPA considered in its screening review for proposed designation and submit any additional information they would like EPA to consider via public comment.
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