In 2023, DA Smith conducted a multisite exploration core drilling campaign at the Graymont Pleasant Gap underground limestone mine located near Bellefonte, Pennsylvania. At over 2,500 feet deep, the Pleasant Gap mine is one of the deepest limestone mines in North America. The exploration campaign was designed to collect rock mechanics and structural data for mine design ahead of deep downdip mining. Holes were cored HQ3 in orientations ranging from subhorizontal to subvertical, on strike, down dip, and normal to bedding.
Drilling was complicated by the occurrence of pressurized natural gas in the formation. DA Smith developed and utilized a proprietary high-pressure gas diverter and blowout preventer (BOP) installed at the collar of the core holes to contain and divert gas away from the drill and personnel. The BOP was attached to grouted-in steel surface casing. On-person and remote station gas monitors were used to monitor gas concentrations throughout the project. Strict adherence to gas-related operating protocols ensured safe working conditions.
The drilling campaign was completed successfully in May.