Two case histories are discussed where groundwater lowering was used to permit completion of excavations that experienced problems because of the lack of groundwater control.The first case involved a 4.1 m diameter tunnel, some 26 m below grade, within a clay stratum sandwiched between two water-bearing, granular deposits. Several collapses of the tunnel roof occurred because of a local depression in the surface of the clay stratum, allowing the upper, water-charged granular material to flow into the tunnel. Subsequent investigations indicated the feasibility of lowering the groundwater level by means of an eductor well system, allowing completion of the tunnel in relatively dry conditions.The second case describes groundwater problems associated with the sinking of a 21 m deep exploratory mine shaft through water-bearing silts and sands. Three attempts at sinking the shaft without groundwater control had failed. Therefore, based on the results of a pumping test, eductor wells were installed around a steel sheet pile cofferdam to permit the successful sinking of the shaft to bedrock.