Laserfiche WebLink
<br /> <br /> <br />r <br /> <br />Grand Junction Pipe <br />Surficial Geology Investigation Proposed Soaring Eagle Gravel Pit, Grand Junction, Colorado <br />January 25, 1999 Page 2 <br />The site is located on the north, northeastern flank of the Uncompahgre Uplift, with the sedimentary beds <br />dipping into the Piceance Basin, to the north northeast. The structural geology on this particular site is <br />relatively uncomplicated, with the srte being located approximately 2 miles northeast of the Redlands Fault <br />Complex and is at the southeast margin of the Piceance Basin. <br />' This tract is located approximately 2 miles northeast of the steep slopes and cliffs of [hc Colorado National <br />Monumem. The Colorado National Monument is a[ [he northeast portton of the Uncompahgre Uplift and the <br />steep cliffs overlooking the Redlands and Colorado River are the surface expression of the Redland Fault <br />' Complex. The higher elevations of the Colorado National Monument represent a vertical displacement in <br />excess of 2000 feet. <br />Some minor faulting is located near [hc Colorado/Utah State Line, approximately 25 miles northwest of this <br />site. This faulting is associated with several small, mapped anticline structures. <br />The tract is located within the geologically active flood plain of the Colorado River. This active Flood plain <br />is composed of approximately 15 to 25 fee[ of unconsolidated soils which are underlain by a very thick <br />sequence of sedimentary rocks. <br />The trnct is underlain by the Dakota Formation. The Dakota Formation is part of a thick sequence of <br />sedimentary rocks which gently dip or slope toward the north northwest. This dip in this general area ranges <br />from approximately 4 to 8 degrees from the horizontal. <br />Seismic events have occurred near, and possibly, in the Grand Valley area. These events were evaluated as <br />having Richter Magnitudes up to and including 4.4, with no reported damages. <br />SFfE GEOLOGY <br />At the present ground surface, a sandy gravel and gravel and cobble alluvial deposit was encountered. <br />' Numerous small Sand, Sil[ and C!aycy deposits are present on the ground surface, as a rosult of ovcrbank <br />flooding and normal river depositional processes. This coarse grained gravel and cobble deposit is the Present <br />Terrace Deposit of the Colorado River. This gravel and cobble deposit is believed to be between I S to 25 feet <br />' in thickness, based upon auger boring logs th this general area. This is the gravel deposit which is to be <br />extracted and processed. In general, the upper 3 to 5 feet of the gravel and cobble is somewhat sandier and <br />may contain some thin silt, sand and clayey deposits. The maximum cobble size is normally on the range of <br />7 to 9 inches (square screened size) but the lower 4 to 6 feet of the deposit may contain occasional cobbles up <br />to 12 to 16 inches in diameter. <br />The Dakota Fomtation is considered to be bedrock in this portion of the Grand Valley. The Dakota Formation <br />is believed to be less than 100 feet thick in this particular area, based upon exposures of [hc geologic rock <br />section in the river bluff on the south side of the Colorado River. The rock exposures to the aver bluff include <br />the Burro Canyon/Morrison Formations (undivided). The Dakota Formation in the Redlands Area of Grand <br />Juncuon is generally described as a series of interbedded siltstone and sandstone, with dark gray to gray black <br /> <br />