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, backfill the hole with bentonite pellets or grout. This is especially important in urban areas where ground contamination from leaking underground storage tanks is common. 

To avoid potential settlement or uplift of pavement core, backfill all borings under existing pavement shall be backfilled 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 non-shrink grout to the top of pavement

.