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Some Austrian areas exhibit soil and rock structures that make the infiltration of water into the aquifer difficult . During the 1980s , most of the springs ceased flowing , and further increase in water demand has caused deterioration in water quality , including the intrusion of seawater into the aquifer system . The greater San Antonio area has a particularly sensitive ecosystem built upon hard limestone bedrock and thin soils.The limestone 's faults and sinkholes allow rainwater to drain directly into the aquifer without the benefit of passing through soil , which naturally filters out sediment and urban runoff pollutants . Injecting air or oxygen into an aquifer to strip or flush volatile contaminants as air bubbles up through the ground water . In the course of the study , only 67 percent of the chloride and THMs injected into the aquifer system were recovered after 132 percent of the volume of the injected water had been extracted . But experts also worry that the long-lasting chemical will increasingly penetrate more deeply into the aquifer system and turn up in more of the deep public wells that supply most of the region 's drinking water . Acceptable water well construction methods include well drilling , driving , boring , jetting and excavating into an aquifer to obtain groundwater for a source of water supply . Municipal and industrial monitoring wells are usually not suited for examining shallow ground water , because they are often completed deep into an aquifer to allow for the maximum yield , according to Iles . Data from 18 shallow borings indicate incision into each aquifer by the paleo Savannah River channel and subsequent infill of permeable alluvium , allowing for direct hydraulic connection between aquifers and the Savannah River along parts of its reach .