It was starting to weep when we inspected it. You’ll want to include a “power down” step in your response plan.
• Vent line construction. One of our original concerns was what
would happen when the wind pulled on a steel vent line attached
to a fiberglass tank. Would the vent pipe rip out of the tank?
Would the vent simply break? Would it damage the tank?
Ironically, we did not see tank damage at any of our sites. As
one of the owners told me, “It wasn’t where the wind was blowing,
but what the wind
That seemed to
define vent pipe
damage. At some
of the sites, all
were the vent
pipes. Apparently, Vent pipe left standing
5 4 | PEI.ORG | Second Quarter 2012
they made a small target. At one site, the vent piping had been
constructed by threading the steel underground portion with a
straight, steel pipe at the ground surface. When a car was tossed
against the vent pipes, those threads served as a “shear spot.”
There was a clean break at the ground surface with no signs of
stress or damage underground—much easier to repair.
• Shear valves. We have all seen action movies where a car runs
over the dispenser, gas sprays up in the air like a geyser, the gas
ignites and moviegoers are treated to an amazing explosion scene.
You probably shake your head and laugh because you know that
in today’s stations that really shouldn’t be able to happen. In
most states—Missouri included—the shear valve installation is
regularly checked so that if a dispenser is hit, the damage will be
minimal. What even our inspectors didn’t realize, however, was
that those shear valves also serve another purpose.
When the dispensers were destroyed in the tornado, the shear
valves cut off all product loss—exactly as they were intended to
do. But the shear valve also served to protect the underground
components by isolating the parts of the system that were most
vulnerable to damage from those belowground components. As
a result, most of our Joplin owners will tell you the shear valve is
worth every dime it costs. Just make sure it is installed properly.
Some of our customers were able to rebuild their buildings
and canopies (no small task) and simply reinstall the dispensers. The rest of their UST systems were fine! During these
difficult economic times, I would wager that the owners and
operators were especially relieved to not have to replace the
tank system, too.
At one site, the shear valve broke when the bolt-anchored dispenser was blown off. The piping, unfortunately, went with the
dispenser. At another facility, the evidence of the straight upward
wind was obvious. Whatever was left of the dispenser, anchor,
Broken fiberglass line