EVALUATION OF NEEDLE GUN AND ABRASIVE BLASTING TECHNOLOGIES IN BRIDGEPAINT REMOVAL PRACTICES

This paper reviews the results of a U.S. Environmental Protection Agen cy (EPA) study that assessed needle gun technology as an alternative t o conventional abrasive blasting technology to remove lead-based paint from steel bridges in western New York State. The study analyzed the operational and logistical aspects as they relate to worker health and safety, environmental protection, hazardous waste generation, and cos ts as compared to those arising from conventional abrasive blasting. I n this 1992 EPA study, the costs and the product quality aspects favor ed conventional abrasive blasting over the needle gun technology for r emoving lead paint. However, abrasive blasting exposed workers to airb orne lead levels that exceeded Permissible Exposure Limits (PELs) as e stablished by the Occupational Safety and Health Administration (OSHA) , as well as emitting high levels of lead-contaminated dusts and debri s into the environment. It was estimated that more than 500 Ibs of lea d-contaminated spent abrasives and paint waste were released into the environment during paint removal operations. The needle gun system red uced (up to 97.5%) the generation of hazardous waste and the airborne concentrations (up to 99%) of respirable dusts and lead-containing par ticulates generated during paint removal operations. However, labor co sts for the needle gun were three times higher than those for abrasive blasting primarily because of slower production rates that necessitat ed more operating personnel. The higher labor costs of the needle gun are partially offset by the increased costs associated with the expend able abrasive blast media and hazardous waste disposal. In the EPA stu dy, the productivity of the needle gun system was 12.2 ft(2)/hr vs. 14 7.5 ft(2)/hr for abrasive blasting. A post blast was needed for the ne edle gun system to meet surface preparation specifications. When facto ring in the costs of full containment structures to meet OSHA's 1993 L ead Exposure in Construction regulation, the needle gun system has the potential to be economically competitive with conventional abrasive b lasting.