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portion of the site. Evidence of slope failures was not observed in the natural, undisturbed slopes or the <br />existing cut slopes. Some minor rockfall and erosion was observed in the cut slopes. <br />The sandstone bedrock observed in the existing cut slopes were silty, fine to medium grained, hard to very <br />hard and brown to red in color. The sandstone bedrock appeared to have relatively thin, horizontal bedding <br />planes that were dipping very gently down to the west- southwest and away from County Road 53. Some <br />small fractures in the sandstone materials were observed in the existing cut slopes. Extensive fracturing or <br />faulting was not observed in the sandstone materials at the time of our observations. Samples of the <br />sandstone bedrock materials were obtained for density and compressive strength testing. <br />Laboratory Investigation: Three samples of the sandstone bedrock obtained from the existing cuts slopes <br />at the site were tested in our laboratory for unit weight and compressive strength. The sandstone bedrock <br />materials had unit weights ranging from 140.0 to 147.5 pcf. Unconfined compressive strengths of the <br />sandstone bedrock materials generally ranged from 1,800 to 8,200 psi. <br />Geologic Setting and Conditions: The site lies along the northern flank of the Williams Fork Mountains <br />at the southeastern end of the Sand Wash basin. The Sand Wash basin is depositional basin containing <br />rocks of the Cretaceous age Mesaverde Group and is bordered on the east by the Park Range, the south by <br />the White River uplift and Axial Anticline to the west (Robson & Stewart, 1990). Marine and nonmarine <br />rocks of the Iles and Williams Fork Formations compose the Mesaverde Group. <br />Geologic mapping (Tweto, 1976) indicates site bedrock conditions consist of interbedded sandstones, <br />shales and coal beds of the Cretaceous Williams Fork Formation. The site is located along the western limb <br />of a north trending anticline several miles east of the site. Site observations indicate moderate to massively <br />bedded, highly cemented (indurated) sandstone is the predominant rock exposed and displays a gentle dip to <br />the west - southwest. Bedrock fracturing, jointing and erosion has produced highly variable outcrop grain <br />sizes ranging from gravel to small boulder (I -inch to 24 -inch) size material. Weathered shaley claystones <br />were also observed near the proposed top of cut at several locations. <br />Slope failures, hummocky topography or other indications of slope instability were not observed within or <br />west of the site. Although minor rockfall and erosion was observed on exposed bedrock surfaces and in <br />previous mining locations, global and shallow slope stability appeared good. <br />Geologic Hazard Evaluation: NWCC's review of Routt County Geologic Hazard maps indicate the <br />proposed quarry site is not located within mapped Un- Stable (US) slopes, Potentially Unstable Slopes <br />(PUS), Land -Slide (LS) deposits or Rock Fall (RF) areas. <br />NWCC agrees with this assessment. Site topography is somewhat variable due in part to previous quarry <br />mining activity, and also in part to natural variability. Natural slopes range from steep (30 to 40 percent) to <br />very steep (up to 100 %). Slope failures or evidence of creep were not observed within or adjacent to <br />proposed quarry areas; however, some minor rockfall was observed in the existing cut slopes. Deeper <br />seated slope failures, slides and large rockfall hazards are not anticipated. <br />Job Number: 11 -9090 NWCC, Inc Page 2 <br />