If decontamination procedures are not followed, which piece(s) of drill equipment is (are) most likely to contaminate a well?

• A. Drill rods only
• B. Augers only
• C. Samplers only
• D. Drill rods, Augers, and Samplers

Answer: (D)

Decontamination is needed for anything that touches formation material or well water before it’s used again, because residues can be carried into the next operation. In groundwater work, all three types of equipment—drill rods, augers, and samplers—contact the subsurface or the water being sampled. If they aren’t cleaned properly, contaminants can cling to their surfaces and be introduced into the well or into another formation being sampled.

Drill rods transmit drilling fluids and formation debris down into the borehole, augers pick up and move soil and sediments, and samplers collect water or soil samples that can carry surface- or other-formation contaminants. Any of these surfaces can retain contaminants and transfer them to the next well or to the next sample, making cross-contamination likely if decontamination steps are skipped.

In practice, to prevent this, equipment that contacts different wells or formations is either thoroughly decontaminated between uses or dedicated to a single well. Since any of these pieces can introduce contaminants if not cleaned, all three are at risk of contaminating a well when decontamination procedures aren’t followed.