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EEC Project No. 1082030 <br />Turnpike Reservoir -Feasibility Study <br />May 5, 2008 <br />Page 5 <br />SITE GEOLOGY <br />Earth Engineering Consultants, Inc. <br />The site geology presented in this report is based upon the acquired field data, review of the <br />available literature and maps, and previous experience with similar geologic conditions in <br />this area. The locations of geologic features are approximate and should be considered <br />accurate only to the degree implied by the methods used to make those measurements. <br />The Turnpike Reservoir site lies within the Colorado Piedmont Section of the Great Plains <br />Physiographic Province. The Colorado Piedmont is an elongated trough in the Great Plains, <br />adjacent to the Front Range of the Southern Rockies. The Colorado Piedmont was formed <br />when uplift of the area in Miocene-Eocene times (20-50 million years ago) produced an <br />increase of stream erosion resulting in scouring next to the foothills and outlying areas. The <br />Piedmont is bordered by the southern Rockies to the west, Great Plains escarpment to the <br />northeast, and Palmer Divide to the south. <br />Structurally, the site lies on the western edge of the Denver Basin, a thick accumulation of <br />Paleozoic and Mesozoic Era sediments involved with down-warping in the basin area and <br />uplift of the adjacent highlands. Small anticlinal folds occur adjacent to the Front Range. <br />Locally, this site is situated within the Boulder-Weld Coalfield, a complex network of <br />northeast trending dip-slip faulting, which is thought to be associated with the development <br />of a large delta at the time of deposition. Faulting is not obvious from surficial features and <br />has been documented within the extensive historic mining operations. It is our understanding <br />that faulting has not taken place in the recent historic past in this area. <br />The site is overlain with surficial alluvial and mixed alluvial soils which overlie the Laramie <br />Formation. These soils consist primarily of clays and sands with significant sand and gravel <br />deposits within the influence of Boulder Creek. <br />The Laramie Formation consists of interbedded claystone, siltstone, and sandstone strata <br />several hundred feet thick in this area. Cementation of this formation varies from weak to <br />strong, depending primarily on the cementing agent and the degree of weathering.