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1 ~ • <br />1 <br />' Grand Junction Pipc <br />Proposed White+vater Pit, Whi[cwaler, CO <br />Februan'19,1998 Page 2 <br />feet cast of this silt and approximately 1000 Ccet south of this site. Based upon information available to Lincoln <br />' DeVore. it rs believed the dip of the sedimentan~ beds beneath this site would be bet+veen 2 to S degrees, with <br />a strike of approxrmateh~ 30 degrees to 45 degrees west of north. <br />' Seismic events hate occurred near the White+vater area. These events, generally considered to have occurred <br />m the greater Grand Junction area, have generally noL been further identified as to source. It is believed the <br />Glade Park Fault, +chich is west of [he Jacobs Ladder Fault Complex and the Ladder Creek Monocline would <br />' hate some potential for these low' intensity canh quakes. Thcsc events, within the greater Grand Junction area <br />were c+alualcd as hating Richter Magnitudes up to and including d.d, with no reported damages. <br />' SITE GEOLOGY <br />This p.~trtrcular site is located at or slightly above the contact of the Dakota Formation and the overlying Mantos <br />Shale Formation. The majorih of Lhc Mantos Shale has been eroded from this site. For all intents and <br />' purposes. the Dakota Formation should probably be considered as bedrock. It is anlicipatcd the Dakota <br />Fommlion and possible remnants of the Mantos Shale Formation wall be encountered at the base of the gravel <br />pit. <br />' Thc actual gravel deposit appears to have been deposited as part of the Gunnison River Terrace. It is possible <br />that sonic contributions of Whitc+vater Creek, originating on the upper slopes of Grand Mcsa, may be found m <br />' this pit Thc majority of finer grains soils on (hc gound surface and possibly as lenses within the gravel deposit, <br />would be sonic Ilood/oycr bank deposits of the Gunnison River and a large amount of fine grained soils <br />deposited b} Whitc+vatcr Crcek. The amount of stratification and intcrtongucing of the Gunnison River deposits <br />' and the Whiltacatcr Creek deposits cannot be dctennirtcd without a large number of exploration/obsen~ation pits. <br />GROUND WATER <br />' This tract is underlain b+' several aquifers, with significant confined aquifers being located in [he lower <br />sandstones of the Dakota Formation. thin sandstones beds in the Summerville Formation and the Entrada <br />sandstone Formation Thcsc confined aquifer beds r.•tngc from approximately 100 feet below the present ground <br />t surface to in excess of S00 feel Il is anlicipatcd Thcsc confined aquifers will not be affected by the extraction <br />of gravel on this site. <br />' Thc site is underlain by a shallow'. pcrchcd +valcr aquifer comamcd in the alluvium of the Gunnison River and <br />~hitcwatcr Crcck. Thc s~rayels and cobbles of the Gunnrson Rrccr alluvmm is proposed for extraction m this <br />project This shallow, pcrchcd water in the alluvium would probably require some pumping in order to lover <br />' and control the +vatcr in(lo+cs into the pit arcs. Actual rates of pumping in these gravels deposits along the <br />Gunnison River arc typically rclatiecly small, due to the thin aquifer thickness and relaliveh-small ground water <br />potential surface. <br />SURFACE WATER <br />' This silt is totaled in +vhal ++•ould probably be termed the 100 Ycar Flood Plain of the Gunnison River. Sonic <br /> <br /> <br />