Drilling methods

1. This subsection applies to areas not likely having subsurface contamination. a. Whenever feasible, drilling methods should not introduce water or fluids into the borehole and should optimize cuttings control at ground surface. The selected drilling method must reflect the purpose or objective of the borehole or monitoring well. b. During drilling of boreholes, adequate care must be taken to prevent commingling of water from separate aquifers. c. The nominal diameter of a borehole must provide a minimum annular space of 1.9 inches [48 millimeters]. 2. This subsection applies to areas having potential subsurface contamination. In addition to the requirements of subsection 1, drilling methods in areas of potential subsurface contamination must follow the procedures in this subsection. a. During drilling of boreholes, precautions must be taken to prevent cross-contamination of boreholes. (1) Augers, center plug, and soil sampling equipment must be decontaminated following procedures appropriate for the contaminants of concern, which do not result in the cross-contamination of boreholes or monitoring wells and which do not conflict with the monitoring objective. (2) The drilling sequence of boreholes must consider the objective of the site assessment, including factors such as the suspected location of the contaminant, contaminant characteristics, and local site geology. b. All potentially contaminated cuttings, as well as development and purge water, must be handled in an environmentally safe manner. When suspected contamination includes hazardous substances as defined and regulated under chapter 33.1-24-02, proper management methods for cuttings and water of each borehole must meet the requirements of North Dakota Century Code chapter 23.1-04 and North Dakota Administrative Code article 33.1-24.