Abstract: Shallow boreholes, e.g. seismic shot holes are usually sealed with cement, gravel or more recently by pouring a water swellable material such as bentonite into the hole. A more effective method of sealing involves the insertion of an impermeable bottom plug into the hole, followed by a thick layer of a particulate material such as sodium bentonite which expands when in contact with water to seal the hole. A top plug can also be used with or without a cover of cuttings to promote lateral expansion of the sealant in the hole.