What Is a Class VI Well?

California has some of the most ambitious climate targets in the nation: cutting greenhouse gas emissions 40% below 1990 levels by 2030 and achieving carbon neutrality by 2045. Meeting these milestones requires more than clean power and electric vehicles, it demands innovative tools for removing and safely storing carbon dioxide (CO₂).

One of the most promising solutions is the Class VI well. These wells are specifically designed for underground carbon sequestration, providing a secure way to keep CO₂ out of the atmosphere for thousands of years. At Calgren, we’re advancing this effort through the Tulare County Carbon Capture and Sequestration Project (TCCSP), a pioneering initiative that places our region at the forefront of California’s carbon capture strategy.

The U.S. Environmental Protection Agency (EPA) regulates underground wells through the Underground Injection Control (UIC) program. This program ensures that underground injection, whether for water disposal, enhanced oil recovery, or carbon storage, protects both drinking water resources and the environment.

The Six Well Classes

• Class I: Industrial and municipal waste disposal
• Class II: Oil and gas-related injection
• Class III: Solution mining (e.g., salt, uranium)
• Class IV: Hazardous waste (now banned)
• Class V: Miscellaneous wells (from geothermal to stormwater)
• Class VI: Wells dedicated to geologic carbon sequestration

Class VI wells are unique because they’re designed solely to inject CO₂ into deep rock formations, safely and permanently trapping it underground.

Think of a Class VI well as a reinforced straw that carries CO₂ deep underground. Except instead of piercing a soda can, it penetrates carefully studied layers of porous rock sealed beneath impermeable caprock.

Site Characterization

Before a well is drilled, scientists perform extensive site characterization, studying geology, hydrology, and seismic stability to ensure CO₂ will remain contained. Only formations that demonstrate long-term storage security are approved.

Well Design & Construction

Well construction is held to some of the highest engineering standards in the energy sector. Multiple layers of steel casing and cement create protective barriers that isolate the injected CO₂ from groundwater sources.

Monitoring & Verification

Once operational, Class VI wells are subject to rigorous monitoring, reporting, and verification (MRV) requirements. Operators track pressure, CO₂ plume movement, and groundwater quality, ensuring storage integrity. Even after injection ends, monitoring continues for decades to guarantee permanence.

California’s Scoping Plan and legislation like SB 32 outline the need for carbon capture and storage (CCS) alongside renewable energy expansion. State regulators, including the California Geologic Energy Management Division (CalGEM) and the California Air Resources Board (CARB), are building frameworks to scale CCS responsibly.

In Tulare County, Calgren is supporting this initiative with the Tulare County Carbon Capture and Sequestration Project. The project will establish a dedicated Class VI well near Calgren’s renewable fuels facility, capturing CO₂ and securely storing it underground.

Key features of the TCCSP:

• Location: Tulare County, CA leveraging existing energy infrastructure
• Storage Potential: 50 million metric tons of CO₂ over the project’s lifetime
• Innovation: Among the earliest Class VI well projects advancing in California
• Community Impact: Job creation, investment in local infrastructure, and positioning the Central Valley as a hub for clean energy innovation

Benefits

• Permanent CO₂ storage that keeps emissions out of the atmosphere
• Support for California’s clean energy transition, complementing renewables
• Local economic growth, including jobs and tax revenue from new energy projects

Challenges

• Regulatory approvals take time, requiring coordination across state and federal agencies
• Public acceptance depends on transparent communication and community trust
• Costs of drilling, monitoring, and maintaining Class VI wells are significant, though they are expected to decrease as projects scale

For California to meet its climate goals, tools like Class VI wells are essential. They provide a safe, permanent way to manage emissions while supporting clean energy and local economies.

Calgren’s Tulare County Carbon Capture and Sequestration Project demonstrates how California’s Central Valley can lead the state, and the nation, in advancing carbon storage solutions.