In-Depth Evaluation: Dust-Control Technology for Asphalt Pavement at Milling at U.S. Highway 2 Resurfacing Project, Midwest Asphalt, Contractor, Wilton, Minnesota, June 20 through 22, 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 water-flow rates to the spray nozzles at the cutter drum from an average of about 16 gallons per minute (gpm) to an average of about 18.5 gpm resulted in no clear reduction in measured respirable dust concentrations at area air monitoring locations around the machine. The following factors make the possibility of detecting sizable reduction unlikely for this study: (1) the relatively small difference in the water flow rates; (2) the considerable interruption in the flow of trucks removing the milled asphalt, leading to substantial down time in the actual milling. Both of these may explain the ineffectiveness of the water-flow levels seen, which is evident from examination of the data collected. Long time-period respirable dust and quartz results reveal a minimal average reduction from low to high water-flow rates, and the various examinations of the real-time monitoring data, using both long and short time periods, reveal conflicting results with no evidence of reductions in respirable dust concentrations.