Groundwater Contamination

Aquifer Contamination

The Central Oklahoma Aquifer faces contamination threats primarily from human activities concentrated in urban and semi-urban areas. While the aquifer remains a vital water source for central Oklahoma, its vulnerability is heightened where shallow groundwater intersects with industrial, military, and agricultural land use.

Several federally designated Superfund sites are located within or near the aquifer boundary. These sites have released a range of pollutants into shallow groundwater, including volatile organic compounds (VOCs), chlorinated solvents, petroleum hydrocarbons, and heavy metals:

• Tinker Air Force Base: Located east of Oklahoma City, Tinker AFB is a major contamination source, with chlorinated solvent plumes—primarily trichloroethylene (TCE) and perchloroethylene (PCE)—migrating into shallow groundwater. EPA has implemented containment and treatment systems, with long-term monitoring in place (EPA, n.d-f).

• North Canadian River (OKC): This site includes petroleum-related contamination from industrial operations along the river corridor, which intersects the aquifer’s western extent. Remediation has involved soil removal and groundwater monitoring (EPA, n.d-e).

• Double Eagle Refinery: A former oil reclamation facility in Oklahoma City that released benzene, toluene, and xylene into the environment. Subsurface groundwater remains impacted, with ongoing containment measures in place (EPA, n.d.-a).

• Compass Industries: Located in Logan County, this site contributed volatile organic compounds (VOCs) and waste oil to the shallow aquifer. Cleanup included drum and contaminated soil removal, with monitoring of nearby residential wells (EPA, 2024c).

• Eagle Industries: This metal plating site released hexavalent chromium, cadmium, and other heavy metals into shallow soil and groundwater. A groundwater extraction system has been installed to prevent contaminant migration, with monitoring ongoing (EPA, 2024e).

Beyond Superfund sites, nonpoint source pollution from agriculture and septic systems also threatens water quality in the unconfined portion of the aquifer. In rural areas with shallow wells and permeable soils, nitrate concentrations have exceeded recommended levels, particularly in parts of Cleveland, Logan, and Pottawatomie counties (Christenson & Carpenter, 1992; OWRB, 2019).

Contaminants are typically concentrated in the shallow aquifer, but in areas with permeable pathways or fractured zones, pollutants may migrate deeper. This underscores the importance of identifying sensitive recharge zones and enforcing land use protections near vulnerable parts of the aquifer. 

While this section focuses on human-caused contamination, it's important to note that some naturally occurring contamination, such as arsenic, uranium, and chromium, can also affect water quality in parts of the aquifer. These are described in more detail in the Natural Chemical Character of Groundwater section of Aquifer Characteristics page (Parkhurst et al., 1994; (Christenson & Carpenter, 1992).

Protection and Clean-up

Multiple agencies are responsible for protecting and remediating groundwater quality in the Central Oklahoma (Garber-Wellington) aquifer system.

The U.S. Environmental Protection Agency (EPA) oversees Superfund site remediation under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), including at major sites like Tinker Air Force Base and the Double Eagle Refinery. These efforts involve groundwater containment systems, soil remediation, and long-term monitoring to prevent contaminant plume migration (EPA, 2024b, 2024d).

The Oklahoma Department of Environmental Quality (ODEQ) works in partnership with EPA on site investigations, risk assessments, and oversight of groundwater monitoring across affected sites (EPA, 2024a–f). ODEQ also manages public health communication and enforces site-specific institutional controls, such as land use or well restrictions (ODEQ, 2023).

The Oklahoma Water Resources Board (OWRB) is tasked with managing groundwater rights and sustainability through well permitting and enforcement of maximum annual yield determinations, which account for both quantity and quality concerns (OWRB, 2019; OWRB, Tentative Order, 2024). These administrative rules help prevent overextraction in areas with contamination risk.

In some cases, responsible parties—such as the U.S. Air Force at Tinker AFB—operate on-site treatment systems and submit cleanup progress reports under EPA oversight (EPA, 2024b). Institutional controls are frequently applied where remediation is ongoing to protect public health and prevent exposure.

Collectively, these federal and state agencies coordinate to monitor groundwater, enforce remediation, and protect long-term aquifer sustainability (EPA, 2024a–f; OWRB, 2019; ODEQ, 2023).