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• <br />' Grand ]unction Pipe <br />Surficial Geology Investigation Proposed South Fruits Gravel Pit Extension, Fruits, Colorado <br />April 5, 2001 Page 3 <br />' the south side of the Colorado River. The rock exposures th the river bluff to the south also include the Burro <br />Canyon/Momson Formations (undivided). The Dakota Formation in the Redlands Area of Grand ]unction is generally <br />' described as a series of interbedded siltstone and sandstone, with dark gray to gray black thin bedded to laminated bedded <br />carbonaceous shale, mudstone and siltstone. <br />GROUND WATER <br />The ground water elevations are believed to be within 3 to 6 feet of the ground surface and aze largely controlled by the <br />elevation of the Colorado River and irrigation practices north of this site and northeast of Fruits. This ground water should <br />be considered a permanent feature of the site. Dewatering of the open pit during nrinirrg will be required. <br />' A deeper ground water is present in the underlying rock deposits. This lower ground water is within several confined <br />aquifers. Some of these confined water are potable. Information available to Lincoln DeVore, the U.S. Geological Survey <br />' Professional Paper # 451, Geology and Artesian Water Supply, Grand Junction area, Colorado, S.W. Lohman, 1965, <br />provides a drillers log of several walls penetrating some of the confined aquifers. Making corrections for topography and <br />the structural dip of the beds, a salty ground water in the Dakota Formation could be anticipated approximately 100 fleet <br />' below the ground surface, a thin potable aquifer in the Somerville Formation approximately 700 feet below the ground surface <br />and potable water th the Entrada Sandstone approximately 1000 feet below the ground surface. As can be seen from these <br />depths, the confined water strata would be found at significant depths and would probably be separated from the proposed <br />' mineral extraction. <br />SURFACE WATER <br />Surface water generated on this tract, resulting from storm runoff is expected to be quite small. The principle source of storm <br />' water on this site will probably be by flooding of the Colorado River. The Adobe Creek Drainage is located about 1-I /2 mile <br />east of this tract and the Little Salt Wash is about 1 mile northwest of the tract. A prominent drain ditch is present along the <br />east tract line. <br />' This site is within the designated 100 Year Flood Plain, shown on the National Flood Insurance Program Maps for Mesa <br />County, Colorado. <br />ECONOMIC GEOLOGIC DEPOSITS <br />' The economic deposit of consequence on this site is the sand and gravel of the Present Colorado River Terrace. <br />The perched ground water on this site, which may be enwuntered between 3 to 6 feet below the present ground surface, <br />' contains soluble sulfate salts and other minerals insufficient quantity that the water is not considered potable. These waters <br />may, in some instances be utilized for imgation but, are normally considered to have excessive minerals. The confined waters <br />vi the Dakota, Summerville and Entrada Formations are generally considered of minor consequence th this area It is not <br />' believed this proposed gravel extraction operation would affect, either positively or adversely, these deeper, confined ground <br />waters. <br />