My Test

Underground Storage Tanks & Corrosion


A Closer Look At Diesel: Colorado Dept of Labor and Employment - Division of Oil and Public Safety 

This report explains the background of the EPA report of July 2016 (below).

The reason for the severe sudden corrosion seems to be attributed to the gradual changes in diesel fuel between 2006-2014 - from low sulfur diesel (LSD) to ultra low sulfur diesel (ULSD).

It resulted in:

  • sulfur change -  the fuel’s “antibiotic” properties diminish, possibly allowing for more microbial activity 
  • lubricity additives -  may not be compatible with certain non-metallic seals and gaskets. 
  • oxidation stability -  can result in the buildup of oxidation products, commonly seen as rust or sediment buildup.  

Also, the blending of biodiesel in diesel fuel that makes it more susceptible to oxidative degradation than petroleum diesel. 

EPA's July 2016 (see below) finding:

  • 83% of UST systems evaluated in the study exhibited moderate to severe corrosion. Only 25% of the affected owner/operators were aware of the corrosion prior to the study. 
  • Severe corrosion is not limited to the tanks, but also prevalent in all the metal components of the fueling system. Found in steel as well as fiberglass tanks. 
  • The condition is widespread – affecting diesel fueling systems in multiple regions of the country. 
  • Ethanol was present in 90% of the 42 tanks sampled, “suggesting cross contamination of diesel fuel with ethanol is likely the norm.” 
  • Many UST systems may be storing fuel that is less “clean and dry” than those standards stipulate. 
  • The presence of particulates and water in the fuel were “closest to being statistically predictive factors for metal corrosion”. 

EPA: Notice Of Corrosion Risks In Underground Storage Tanks Storing Diesel Fuel (July 2016)  


Observations from EPA’s 2016 research, which examined 42 operational UST systems storing diesel fuel across the country, show a significant prevalence of corrosion of metal components inside those tanks. The preliminary results categorized 35 of 42 – or 83 percent – of the examined diesel fuel tanks exhibiting moderate or severe corrosion. Less than 25 percent of USTs involved in the research reported corrosion prior to the internal inspection. Corrosion in the upper vapor spaces inside USTs is a relatively new phenomenon and can cause equipment failure by preventing proper operation of release detection and prevention equipment. In steel tanks, corrosion can cause direct tank failure and releases to the environment.

Since studies to date have not definitively confirmed the root cause of the corrosion, there is no widely accepted solution to the problem. However, there are actions tank owners can take now to minimize the corrosion and the associated risks while stakeholders look for a solution. 


EPA recommends UST owners check for corrosion in their tank systems storing diesel fuel; this applies to both systems with steel tanks and systems with fiberglass tanks. Owners reporting corrosion sometimes find sludge or particles, which may look like coffee grounds, clogging their fuel filters. EPA recommends all owners of UST systems storing diesel fuel conduct a visual inspection by checking in their filters and inside UST system access points even if they have not seen symptoms in the filter; severe corrosion may already be established before symptoms appear in the fuel filter and an owner becomes aware of a severe corrosion issue. Remember that this initial diagnostic observation of UST equipment visible from the surface may not show corrosion even if it exists in the UST system. 

Blind Trust, No More

The regulations and oversights have the history of failure. They are created and maintained with good intentions, with best knowledge and technology of the day, but things keep changing. In this case, the components of fuel change and the long-term effects of them on the UST are unknown for many years to come.

There are also accidents and human mistakes, detection system malfunctions. Even the multi-layer oversight or detection systems can all fail at once. What happened to Boeing 777 Max and why?  Who can blame the public for not trusting the government regulations, oversights and employee training?

We need more than the best promises. We need proactive measure of not placing any potential hazard where they may pose ongoing unnecessary oversight and cautionary expenses, not to mention remedial burden on the innocent public.