Mitigating Respirable Crystalline Silica with No Engineering Footprint

Abstract

Abstract In June 2016,the Occupational Safety and Health Administration, OSHA, reduced the Permissible Exposure Limit (PEL) and created an Action Level (AL) for respirable crystalline silica (RCS) by half and will require engineering controlsto help mitigate employee exposure. In June 2018, the new RCS PEL of 0.05 mg/m3 averaged over an 8-hour period will apply to hydraulic fracturing and most other industries, and engineering control obligations will commence in June 2021 for hydraulic fracturing operations. With an average of over one million pounds of silica sand used in horizontal well completions, crystalline silica is a major component of hydraulic fracturing. Multiple proppant transfer points can generate high concentrations of airborne dust, from offloading trucks to being pumped down hole. Engineering controls can be used tomitigate exposure. A study was conducted at multiple hydraulic fracturing sites to determine if RCS concentrations could be reduced below OSHA's new PEL using engineering controls that do not have an onsite footprint, namely chemically pre-treated sand.During the study, 10 mm nylon Dorr-Oliver (DO) cyclones were used to measure the amount of RCS produced with and without the chemical engineering control in place. The results showed significant reductions in RCS in both personal and area sampling. Results presented in this paper will show that effective engineering controls, withno footprint on site, exist and can significantly reduceair-borne RCS concentrations. Overall helping mitigate occupational exposures below the revised PEL and often below the Action Level.