is a common assumption that fiberglass Underground Storage Tanks (USTs) are impervious
to corrosion which is often seen in steel USTs, but recently fiberglass USTs
have been shown to fail and the cause is interior tank degradation. These tank
failures can result in catastrophic releases of fuel into the environment if problems
with tank interiors are not detected early. A report published in 2013 by the
Association of State and Territorial Solid Waste Management Officials (ASTSWMO)
explains that increased concentrations of ethanol and biodiesel fuel blends can
have a detrimental effect on the life expectancy of a fiberglass UST. It is
important to understand that not all tanks or their components will be compatible
with these new fuel blends.
can a fuel with a higher ethanol concentration degrade a fiberglass UST?
Biofuels have different chemical properties than conventional gasoline or
diesel which can lead to compatibility issues. Biofuels are more soluble and
can degrade, soften, and seep through hoses, gaskets, seals, elastomers, glues,
and plastics. Biofuels are more conductive, which directly leads to corrosion
in steel USTs. Biofuels have the capacity to absorb more water than
conventional fuels, this causes the water to become suspended in the fuel to a
greater extent than is normally seen. The presence of water creates a habitat
for microbial growth while hydrocarbon fuel is a food source for many types of
management is one of the main ways to protect your UST from degradation. Water
intrusion into the UST can create a habitat for bacterial growth, which can
waste product and result in tank or tank component failures. Many types of
bacteria use hydrocarbons (gasoline or diesel) as a food source and once they
consume the fuel they excrete byproducts that can degrade tank linings. Other
types of bacteria can use the resin holding the fibers together in a fiberglass
tank as a food source, which makes tanks vulnerable to failure. Tank
components, especially those made of metal, can be degraded by bacteria as
well; leak detectors, fill tubes, turbines, tank linings, elastomeric seals and
hoses, low points in the piping, turbine pump components, filters and valves.
fiberglass USTs are not immune to
degradation as previously assumed, it is a good practice to inspect for
evidence of interior degradation and microbial contamination. Signs of
microbial contamination in USTs include plugged fuel filters (< 6 month
intervals between fuel filter changes), plugged fuel lines, erratic gauges,
rotten-egg odor, and frequent replacement of valves, rubber seals, and hoses. Direct
signs of tank degradation include white “hair-like” fiber debris and black
coffee ground-like debris. These are typically found in used fuel filters. If
you are experiencing any of these problems you should contact us about possible
microbial contamination or tank degradation. If your tanks are over 20 years
old you are at a higher risk for tank degradation and you should pay extra
attention to this matter.
What we recommend you do:
Implement Good Water
Management Practices: Water intrusion can occur from leaky riser joints, leaky
tank top fittings, faulty spill bucket drains, or careless operators that drain
spill bucket liquid back into the tank. Protect your tank from water intrusion.
Monitor Water in your Tank: New ATG probes can
measure water in various fuel types including alcohol based fuel. Another
method includes using a tank gauging stick and water finding paste.
Inspect your Filters: If your fuel filters
need to be changed frequently (< 6 month intervals), then check to see if
there are white “hair-like” fibers present or black substances that look like
coffee grounds. These are signs of fiberglass degradation. If you suspect degradation,
have your filters analyzed by a laboratory.
Keep Records of
Keep track of how often you need to replace valves, rubber seals, and hoses for
each of your tanks. Frequent replacement of these items is a sign of bacterial
growth in the tank.
you suspect bacterial growth in your tank arrange for your tank interior to be
inspected. If your tank is still under warranty and is over 20 years old, we
recommend having the interior inspected before the warranty on the tank expires.
Tank interiors can be inspected using a camera which can determine if your tank
is at risk of failure.
you have any specific concerns or questions related to the tanks at your
facility, please contact our staff so that we can further assist you.