W. Va. Code R. § 47-60-12
Drilling shall be conducted in a manner so as to minimize the introduction of foreign material into the borehole, produce the least possible disturbance to the formation, and permit the proper construction and development of the required diameter well. Only air, water free of bacterial and chemical contamination, or bentonite drilling mud mixed with water from an uncontaminated source may be used as drilling fluids. The water used for drilling shall be stored in such a manner as to prevent contamination of the clean water. If air is used as a drilling fluid, the air shall be filtered by an oil-air filter or oil trap to reduce or remove the oil content discharged from the compressor. If water is used, the source of the water shall be reported.
W. Va. Code R. § 47-60-12