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Geotechnical Engineering Report lrerracon <br /> Carr Aggregate Pit ■ Carr, Colorado - <br /> April 23, 2020 ■ Terracon Project No. 20195087 GeORepOrt <br /> zone. To provide a check on stockpile sampling, the aggregate materials collected using drilling <br /> methods indicated gravel content ranged from about 12 to 36 percent and fines ranging from <br /> about 1 to 20 percent. Samples of site bedrock selected for plasticity testing exhibited low to <br /> moderate plasticity with liquid limits ranging from non-plastic to 38 and plasticity indices ranging <br /> from non-plastic to 21. Laboratory test results are presented in the Exploration Results section <br /> of this report. <br /> OVERVIEW <br /> Based on subsurface conditions encountered in the borings, sand, gravel, and cobble materials <br /> are present in the proposed project area. This report presents a broad characterization of the <br /> horizontal and vertical extent of potential aggregate resources. A vegetative layer (about 12 <br /> inches thick) and clayey soil were encountered consistently within the upper 4 to 5 feet of most of <br /> our exploration locations. In general, aggregate materials were encountered below the <br /> overburden, ranging in thickness from about 2'/2 feet (CW-02)to about 10 feet (CW-11); typically, <br /> the thickness of potential aggregate was on the order of about 4 to 5 feet thick. <br /> Bedrock depths varied across the site,with the shallowest depth encountered with CW-06 in north <br /> central area of the site, whereas the bedrock was encountered in test pit CW-15 at depth of about <br /> 131/ feet. These estimates are approximate depths, and can be higher or lower depending on <br /> location. <br /> Grain-size distribution test results may not be completely indicative of soils present below this <br /> site. Stockpile sampling methods in general accordance with ASTM C702 were used to collect <br /> subsurface samples from test pits. Materials greater than 3 inches where collected and submitted <br /> to Kiewit personnel for testing; materials less 3 inches where collected for grain-size analyses. To <br /> confirm test pit results, hollow-stem auger borings were drilled between test pit locations. Gravel <br /> and fines content from borings may not be indicative of the actual material quantities, particularly <br /> where gravel and/or cobble particle sizes exceed the diameter of the samplers used during field <br /> exploration. Larger gravel/cobbles then indicated within our laboratory test results were present <br /> below this site. <br /> Groundwater was encountered in test pit CW-13 near Lone Creek at a depth of about 10 feet <br /> below existing site grades. In addition, groundwater was observed in all of the test borings, <br /> ranging from about 16.5 feet to about 24 feet below existing site grades. <br /> GENERAL COMMENTS <br /> Our analysis and opinions are based upon our understanding of the project, the geotechnical <br /> conditions in the area, and the data obtained from our site exploration. Natural variations will occur <br /> between exploration point locations or due to the modifying effects of construction or weather. <br /> Responsive■ Resourceful ■ Reliable 5 <br />