Sentence:  All <WSD>sand boils</WSD> should be watched closely. A <WSD>sand boil</WSD> that discharges clear water in a steady flow normally does not endanger the embankment. However, if the flow of water increases and the <WSD>sand boil</WSD> begins to discharge material, remedial actions should be undertaken immediately. 
Meaning of the word marked with <WSD> tags:  An eruption of water through a bed of sand due, for instance, to seismic activity, or to differences in water pressure on two sides of a levee which causes water to penetrate beneath the levee.