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• water ~ movement through siltstone and <br />T-~ n•Jo-d- . <br />shale in the~Vermejo ~ Raton :~.9v,~c~ is misleading because <br />of a disproportionately high hydraulic conductivity measurement <br />Tr, w ,J~.a)- <br />in one 2 foot thick zone of fractured siltstone. Tests of~Vermejo- <br />•Raton shale and siltstone usually show these rocks to be nearly <br />impervious. <br />The transmissivity is the hydraulic conductivity of an aquifer <br />So,}u~aiEd <br />multiplied by itSnthickness and is an indication of the volume of <br />water that an aquifer can transmit, as expressed in feet square per <br />day. Equal transmissivities can result from a thick aquifer with <br />low hydraulic conductivity or a thin aquifer with high hydraulic <br />conductivity. Table 7.4-1 indicates that the alluvium can transmit <br />much more water than bedrock, that fracturing can increase the <br />• Tr, n, ~~ <br />transmissivity of a bedrock aquifer, and that, in the~Vermejo <br />Raton 'ayv~~« coal and sandstone have about the same transmissivity. <br />Aquifer test data are contained in Griggs (1948), Dames and <br />Moore (.1978), Water, Waste, and Land, Ltd. (1980), Howard (1982), <br />Colorado Water Resources Division drillers logs, and U.S. Geological <br />Survey computer files. <br />• <br />63 <br />