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Is
There a Hole in this Tank System?
A
2001 study by California UST regulators took 330 or so UST cases of
soil/ground-water “action level exceedances” and compared how
those releases were identified.
In their analysis, they found that releases were discovered
via release detection methods (tank/line tightness testing or
approved monthly monitoring methods) only four percent of the time.
Most releases were discovered during tank system removal
activities.
What’s
the problem here? Leak
detection methods, their use and operation vary a lot, and that’s
an issue. But to me,
the most glaring trouble is that there’s a difference between
“releases” and “leaks.”
To
me, a release is any introduction of fuel into the environment.
It can be spillage, overfilling of a tank system, accidental
product loss during maintenance or repairs of a tank system (think
fuel filter changes), or an actual hole in the tank system.
I call a hole in the tank system a “leak,” even though
there are times when that leak does not result in a release.
Confused yet? Some
of you have dug up tanks and lines that had holes plugged by clay or
rust, and had precious little soil impact close to such holes.
But there’s almost always soil contamination under tank
fill riser locations, right, if the system went in before 1988?
How
much historical contamination underlies the older sites out there?
Can you have a “leaker” site and have a tight tank
system? You bet.
Think about the amount of spillage introduced to sites in the
“old days,” say, prior to 1986 or 1987 – or more likely, prior
to spill bucket installation! If
a tanker driver hauled a load of fuel to each of three tanks once a
week, and only spilled one-half gallon of fuel during each tank
fill, 1.5 gallons of fuel a week went into the backfill.
If this was carried on for ten years of site operations,
there’d be 780 gallons of fuel put into the ground over that time.
We know the fate and transport mechanisms, once fuel gets
into backfill, and we know Mother Nature can slowly remediate such a
problem. But by the
time those tanks get dug up, there’s a heck of a residual fuel
load available – mostly in native soil and often in ground water .
. .
As
usual, we want simple explanations for why there’s contamination
on a site. We want to
say the system’s tight or it’s not.
But many releases discovered, I believe, do not tie to an
open hole in the tank system. They
are related to the historical spillage – at tank fills and at
dispenser islands (from broken hoses, loose fittings, and fuel
filter change-outs) – that was caused by reasonable and customary
industry practices in use from the 1920s to the mid-1980s or later.
There
are even more variables to discuss than these – how much benzene
was in gasolines of ten to sixty years ago, compared to now?
Is there geology that holds residual fuel in a fairly small
native soil volume, to make the contaminant levels at a particular
boring look really horrendous?
I could go on. But the first thing I recommend is for industry and
regulators to agree on some basic definitions.
A “leak” and a “release” are seldom the same thing. And “leak detection,” which is what US EPA prescribes in
regulation and in Straight Talk on Tanks (EPA 510-K-95-003)
is not the same as “release detection,” which many regulators
believe they’re looking for.
Think about it.
Cal
Chapman, P. E.
Chapman Engineering
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