In-Depth Evaluation: Dust-Control Technology for Asphalt Pavement at Milling at South Dakota Highway 79 Resurfacing Project, Border States Paving and Industrial Builders, Contractors Buffalo Gap, South Dakota, August 15 through 17, 2006

摘要

As part of an ongoing study to evaluate the effectiveness of dust-control systems on pavement-milling machines, a field survey was performed during milling of asphalt on a rural four-lane divided highway. The objective of this survey was to estimate the reduction in respirable dust emissions and workers' exposures that could be achieved through the use of higher water flow rates through the milling machine's water spray system. The effectiveness of the dust controls examined in this study was evaluated by measuring the reduction in the respirable dust and respirable quartz exposures in personal and area samples collected during this typical milling job. Increasing the total water flow to the water-spray nozzles from about 12.5 gallons per minute (gpm) to about 18.8 gpm resulted in overall reductions in measured respirable dust concentrations at area air-monitoring locations around the machine. The average overall reduction based on the results of the time-integrated air sampling method used was 41%, while that based on the mean results of the real-time data-logging instrumentation was 53%; both of these reductions were statistically significant at the 95% confidence level. In contrast, an examination of short-period subset data from the data-logging instruments (assembled from selected portions of the data sets generated closest together in time and space) revealed an average reduction of 14% that was not statistically significant. Overall, the results varied by location, with the greatest reductions occurring on the right side of the machine. Personal breathing-zone exposures to crystalline silica were below analytical limits of detection.