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SECTiONTHREE Field Investigation <br />3.1 GENERAL <br />The field exploration program consisted of drilling exploration borings and test pit excavations <br />around the perimeter and within the interior of the proposed gravel pit and water reservoir. The <br />owner, Platte Sand and Gavel, provided a base topographic map of the project site and surveyed <br />the horizontal coordinates and elevations of the borings and test pits. The locations of the test <br />pits and test borings aze shown on Drawing 1. <br />3.2 TEST BORINGS <br />The purposes for the subsurface exploration borings were to determine the subsurface <br />stratigraphy, observe and evaluate overburden and rock mass properties (weathering and <br />fracturing), perform packer permeability tests in the bedrock, identify the groundwater table, and <br />install close ended standpipe piezometers in some of the completed borings. <br />The drilling exploration consisted oftwenty-nine borings. Twenty-four borings (TH-1 through <br />TH-24) were located (generally evenly spaced) around the perimeter of the Shazkey's Lake <br />Gravel Pit and five borings (TH-25 through TH-29) were located in the interior future pit area to <br />evaluate the variations of the bedrock depth within the pit. The drilling exploration was <br />completed between August 29, and September 15, 2005. High Plains Drilling, Denver, <br />Colorado, drilled the exploration borings under a subcontract with URS. URS coordinated, <br />observed, and logged the borings. Approximate locations of the borings are shown on Drawing <br />1 and a summazy of the subsurface exploration program is shown in Table 3.2. <br />3.2.1 Drilling Methods <br />Borings were drilled with a CME-75 truck-mounted drill rig and advanced through soils using a <br />4 1/4-inch inside diameter hollow stem auger until bedrock was reached. Soil samples were <br />obtained in advance of the augers at 10 ft to15 ft intervals by driving a 3-inch diameter split <br />spoon in sandy-gravelly soils or a 2-inch diameter standard split spoon in more clayey soils <br />and/or transitions with bedrock. The sampling and in-situ testing was done in general <br />accordance with the procedures of ASTM D1586-99 "Standard Test Method for Penetration Test <br />and Split-Barrel Sampling of Soils". A representative portion of each split-spoon sample was <br />sealed in a Ziploc plastic bag and labeled. <br />NX -sized coring (2-inch inside-diameter) was done into the bedrock with lengths varying from 8 <br />ft to 10 ft. The core was obtained in increments of 5 feet or less and water was used as the <br />drilling fluid. Packer permeability testing was conducted within the bedrock in each borehole <br />upon completion of the coring. After the completion of coring and packer permeability testing, <br />the bedrock was grouted using cement-bentonite grout and cuttings were backfilled up to the <br />ground surface except where a piezometer was installed. <br />3.2.2 Logging Procedures <br />Concurrent with drilling, IJRS' field engineer prepared field logs for each boring. Soil and <br />bedrock samples were visually classified and sample locations, depth of groundwater at the time <br />of drilling, and other pertinent information was recorded. Bedrock core samples were logged to <br />I' N*9PR~OJEC~TS\2223B240 PLATTE_$AND GRAVEL\SUB_OOU2.0_WORD_PROGV'LATTESANDBGRAVELGEOTECNNICALDESIGNREPORT4.O.D000bNOV-0Sl1 3-1 <br />ViW <br />