Fill or plug drill holes using bentonite pellets or cement bentonite grout to prevent injury to livestock or people in the area and to minimize the entry of surface water into the bore hole. If surface contamination of lower aquifers or cross contamination is a concern, grout the hole with cement bentonite grout using tremie method. This is especially important in urban areas where ground contamination from leaking underground storage tanks is common. To avoid potential settlement or uplift of a pavement core, backfill all borings under existing pavement with bentonite pellets or cement bentonite grout to a minimum depth of 6 inches below the bottom of pavement structure. Then patch the hole with nonshrink grout (or materials matching existing pavement) to the top of pavement.