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Dept. of Environmental Healt
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2019-02-20 14:03:28.033909
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Noise and Silica Exposures A Survey of Washington State Quarry Operations The Mine Safety and Health Administration (MSHA) issued a new standard for hearing protection effective in September 2000. The new rule requires that mine operators enroll miners in a hearing protection program if they are exposed to an average sound level of 85 decibels (dBA) or more during an eight-hour period. In order to determine average sound level, workplace noise monitoring is required. The Field Research and Consultation Group (FRCG) at the University of Washington received requests from ten open surface mines in Washington State to conduct noise monitoring to meet these new requirements. In addition, mine operators also requested monitoring for silica to determine silica quartz exposures. The companies evaluated were all small employers, with one to seven quarry operations employees working in three types of open surface mines. The three types of mines included two basalt excavation mines, three portable crusher operations, and five sand and gravel operations. The primary difference in the three operations is the source, size, and type of rock handled. In basalt excavation, blasting and drilling is employed to break rock free of an open face; sand and gravel quarries dredge material from an open pit or pond; and portable crusher plants obtain material from near a road or pond to process for roadbed construction. In all three types of operations dump trucks, excavators, and front-end loaders are used to transport material. The rock is delivered to a processing area where the material is transported via conveyors through a series of crushers and screens for breaking and sorting. There are two types of crushers: cone and jaw. Jaw crushers break large rock into smaller sizes, while cone crushers are used to break aggregate into smaller aggregate. The crusher is run by a crusher operator who usually stays inside the operator™s booth. In small operations, the operator would sometimes go outside to clear jams or for other equipment maintenance purposes. At larger operations there was also often a crusher mechanic and groundsman. The crusher mechanic worked outside near the crusher doing maintenance/repair tasks and frequently worked during breaks when there were no other noise sources nearby. The groundsman was a laborer who cleared jams on conveyors, directed traffic and handled other labor requirements near the crusher. In some cases, workers operated several pieces of equipment over the course of a shift. Figure 1: Portable screening and crusher operation ______________________________________________________________________________________FRCG 01-10 page 1
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