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 Due
to some environmental concerns, our laboratory began EPA-related testing
of existing bridge paints that were due to be removed due to age and
wear. The structural steel on several of Nebraska’s bridges that were
built before Federal mandating eliminated the use of lead paints still
has the older lead-enriched pigments. There has been concern by Federal,
State, and local government, as well as private citizenry, that as
these older lead paints degrade or are removed by sandblasting methods,
that there may be a hazardous potential of the lead leeching into
the local soil or ground water. To date, there are two methods that
are used to determine the lead content of structural steel paint that
is scheduled for removal, and its potential effects on the environment.
The first
is simply referred to as “Total Lead Content.” An inspector scrapes
some of the paint off the structural steel and obtains a sample of
preferably at least half of a gram. This sample is then run through
our X-Ray Fluorescent Spectrometer and tested for the element
of Lead to an accuracy of parts-per-million. The results show if there
is Lead present in the paint, and whether or not there should be a
concern with it becoming friable (airborne during removal), or intrusive
to the removal site’s surrounding soil and groundwater.
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 The
Bridge Engineer decides if a more labor and material intensive test
method should be employed. It is referred to as “Toxicity Characteristic
Leaching Procedure”, EPA method 1311, or TCLP for
short. A sample at least 30 grams of the paint scrapings is obtained,
and after being finely ground, the pH is determined. Depending on
the pH, one of two extraction fluids is applied to the sample, which
is then rotated in an agitation device, (shown on the right),
for 16-20 hours.
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 The
resulting solution is then filtered, and the fitrate’s pH is adjusted.
The filtrate is then taken to our Atomic Absorption Spectrometer,
pictured on the left, for analysis. The parts per million of Lead
and Chromium that are detected in the filtrate are accepted as being
the amount that would have intruded or “leeched” into the environment.
The laboratory then creates a report of the results and sends it to
the Bridge Division.
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