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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.

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.

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.