What California’s E15 Update Means for Retailers: A Practical Look at Compatibility, Risk, and Best Practices

When California Governor Gavin Newsom signed new legislation on October 2 authorizing the sale of gasoline blends containing up to 15 percent ethanol (E15), it signaled a cautious but meaningful shift in the state’s fuel landscape. While the Air Resources Board (CARB) continues its analysis to ensure E15 meets California’s strict clean-air requirements, retailers now find themselves preparing for a future in which higher ethanol blends may become commonplace.

Shortly after the bill was signed, the State Water Resources Control Board issued a Technical Notice reminding operators of something critically important: compatibility matters — especially when ethanol content increases.

For Underground Storage Tank (UST) operators, this isn’t simply a regulatory footnote. Ethanol blends like E15 can introduce new risks if equipment isn’t properly compatible or maintained. The Water Board’s notice points back to longstanding requirements in California Code of Regulations, Title 23, which mandate that every component in the UST system—from tanks and piping to seals, gaskets, and probes—must be certified compatible with the product stored.

Why This Matters: The Hidden Risks of Higher Ethanol Blends

Ethanol behaves differently than traditional gasoline. Even at E10, retailers have long monitored for issues such as phase separation and increased corrosion potential. With E15, these concerns can become more pronounced:

• Phase Separation: Ethanol attracts water. When water accumulates in a tank, ethanol can separate from the gasoline and settle to the bottom, potentially causing engine damage for customers and costly cleanup for retailers.

• Corrosion: Higher ethanol blends can accelerate corrosion in metal components, which may go unnoticed until equipment begins to fail.

• ATG Data Anomalies: Water level fluctuations, sudden changes in product height, or unusual alarms can all indicate compatibility issues or developing problems related to ethanol exposure.

These factors mean routine inspections will need to be sharper, more intentional, and more informed.

A Retailer’s Guide: What To Do Now

Whether California ultimately approves E15 statewide or keeps the authorization temporary, retailers should begin preparing. The Water Board’s Technical Notice highlights existing regulatory expectations, but here’s what operators should be doing proactively:

• Verify Compatibility Documentation
  Confirm that tanks, piping, ATGs, sensors, gaskets, and dispensers are all certified for use with E15. This includes gathering letters of compatibility from manufacturers or UL listings.

• Evaluate Your ATG Trends Carefully
  Unexplained water alarms, erratic product-loss readings, or sensor faults can be the first indicators of phase separation or material degradation. Technicians should know what ethanol-related anomalies look like.

• Increase Visual and Preventative Inspections
  Inspect spill buckets, sumps, seals, and vent components more frequently for signs of swelling, softening, or corrosion. Ethanol-induced deterioration often shows up early in elastomers and metal fittings.

• Train Staff on the Changes
  From managers to technicians, everyone touching the UST system needs to understand what E15 means, what to watch for, and how to respond. This is especially important in California, where regulatory scrutiny is high.

• Stay Connected to Regulatory Updates
  CARB’s ongoing evaluation will continue to define the future of E15 in the state. Retailers should monitor the Water Board’s Technical UST Program Notifications for evolving requirements.

The Bottom Line

California’s temporary authorization of E15 is more than a policy headline — it’s the beginning of a transition that retailers must manage carefully. The environmental and compliance stakes are high, but with proper preparation, operators can reduce risk, protect equipment investments, and maintain compliance.

Higher ethanol blends aren’t new to most of the country, but California’s unique regulatory framework and climate mean that even proven national best practices must be reinforced, documented, and executed consistently. Retailers who prepare now will be far ahead when CARB provides its final ruling.

If you're a fuel retailer in California, think of this moment as a reminder: compatibility isn’t just a requirement — it’s your first line of defense.

Make Compliance Easier with PASS Harmonics

Retailers navigating higher ethanol blends need reliable visibility into every part of their UST system. PASS Harmonics centralizes your ATG data, documentation, inspection findings, and site tasks — helping you spot trends early and maintain compliance effortlessly. If your organization is preparing for E15, PASS Harmonics is the simplest way to manage the added complexity.
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