PURPOSE:  The objective of this project is to improve the understanding of dust generation principles, evaluate and improve current control technologies, and develop new control technologies to provide a broad-based approach towards reducing silica exposure in surface mining operations.

RESEARCH SUMMARY:  Historically, Mine Safety and Health Administration (MSHA) dust sampling data has indicated that some of the most frequently overexposed mining occupations are at surface coal mines. MSHA data for the years 1996 through 2000, shows that of the 1,400 respirable dust samples collected on highwall drill operators at surface mines, over 31% exceeded the permissible exposure limit (PEL) for silica dust.

Reducing respirable silica dust exposures to surface mine workers will be accomplished through multiple efforts. A number of research tasks will address dust generated by surface drills, which is typically the greatest dust source at surface mine sites. Respirable dust reductions for surface drills will be achieved through application of engineering controls that include: using air spray nozzles to maximize dust capture under the drill shroud, developing methods to reduce/eliminate dust emissions at the dust collector’s discharge dump, determining the optimum drilling parameters for minimizing respirable dust generation and using wet drilling technology to reduce dust liberation. Testing will be conducted with full-scale test facilities located at PRL to determine optimum system parameters for using air spray nozzles. Successful lab results will lead to evaluation at working surface mine sites.

Most surface mining equipment is equipped with enclosed cabs that have the potential to provide significant protection from respirable dust, if properly operating. Cab research has focused on improving the performance of air filtration and air conditioning/heating systems. Enclosed cab integrity will be addressed by determining the effective range of operating parameters (filter loading and system integrity) and identifying effective cab maintenance guidelines. In addition, a field-test method for evaluating environmental integrity of enclosed cab systems has been developed and tested through a cooperative research and development agreement (CRADA) with a filter manufacturer. Method development is ongoing and a patent is being pursued. Demonstration of these improved dust control technologies will be completed at a limited number of mining operations.

This research program has the potential to lower the silica exposure of workers by reducing dust generation during drilling and by improving the protection offered by enclosed cabs. Successful development and implementation of improved control technologies will lead to reducing overexposures by 30% within the next five years.