Abstract
This article reviewed the results of bulk sampling of paint and personal and area air sampling for each step of surface preparation prior to the removal of lead (7439921) based paint from steel structures using a chemical stripping process. Paint removal was performed at an overpass bridge that carried four lanes of traffic and spans seven railroad tracks near a switching station. The contract called for removing 30,000 square feet of existing coatings from an I-beam overpass bridge and preparing the substance to SSPC- SP 10 (Near White Metal) specifications before repainting with lead free paint. The project lasted 3.5 months and required 3,800 worker hours to complete. Monitoring took place three times for a total of 5 days. A temporary containment system was constructed around each of the five spans. The workers sprayed an alkaline paste on the painted surface, allowing it to react overnight and then scraped the decomposed paint and excess caustic from the steel surface. After scraping, the debris was cleaned from the area and the surfaces were abrasive blasted. One man sprayed about 20% of the bridge steel with the caustic paste in about 5 hours. Five workers used knives with 4 to 12 inch blades to distribute the caustic paste on the surface. The next day these workers used the same knives to scrape the paint and paste from the bridge. Before abrasive blasting, the worker rinsed the chemically stripped steel surface with a water spray. The blast operators experienced the highest airborne lead and alkaline dust concentrations at this site, the time weighted averages of the two samples collected being 2,000 and 4,700 micrograms/cubic meter. There was very little lead exposure during the caustic paste application and scraping of the parts. Improvement of the rinsing system to remove more of the lead waste may be an effective approach for reducing the exposures as similar sites as this would reduce the airborne lead during subsequent abrasive blasting.
