Cleaner Air, Dirtier Water The Unintended Consequence Of Switching To Ultra Low Sulfur Diesel (ULSD) – Tank Corrosion

By Charles Liou

Recent Environmental Protection Agency (EPA) study has indicated a direct link between storage of Ultra Low Sulfur Diesel (ULSD) and rapid tank corrosions in Underground Storage Tanks (UST). This had spurred worries of groundwater contamination from leaks and spills after 35 of 42 sites that were sampled by EPA had shown moderate to severe tank corrosion upon further investigation.

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After the EPA adopted the final rule to reduce sulfur content in highway diesel in 2006, reports of corrosions in tanks storing ULSD began to emerge at an unprecedented rate. Numerous theories surfaced, some blamed the reduction of sulfur, while others held the increased use of biodiesel blended fuels accountable. Evidence suggested that acetic acid formed as a by-product during microbial activity when ethanol is present and that acid is corrosive to the tank. However, it is still unclear how the changes in lower sulfur content impacted the rate of microbial activity. This may be an example of unintended consequences originating from conforming regulation to protect the environment which actually are causing environmental damages in another media – cleaner air but contaminated groundwater.

The responsibility for ensuring the integrity of UST systems rests on the shoulders of owners and operators and could lead to violations if not properly monitored and maintained.  Making it important for owners/operators to be vigilant when storing ULSD.
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The EPA will likely release their final conclusions of the cause of tank corrosion later this year. Despite of what may have led to the inevitable premature replacement of USTs; early detection of catastrophic failure to such systems may not only save property owners from time-consuming remedial actions, but keep the environment out of harm’s way!