2012-08-03_PERMIT FILE - C1981012 (4)

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April 16, 2012 3.0 FIELD INVESTIGATION Page 5 A field investigation was performed March 8 and 9, 2012 to better define the subsurface conditions at the site. 3.1 Field Investigation Program A total of three borings (BH -38, BH -39 and BH -40) were advanced March 8, and another boring (BH -41) and a dynamic sounding (DS -1) were advanced March 9, 2012 as part of the geotechnical field investigation. The borings and sounding are located within the footprint of the proposed DWDA and are illustrated in Figure 1. Each boring was advanced with a truck - mounted Simco drill rig equipped with 4 -inch diameter solid stem, continuous flight augers. Representative bulk soil samples were recovered by cuttings brought to the surface by the auger flights. More representative samples of specific intervals were collected with a California barrel (2 -inch inner diameter sampler), driven with a 140 -pound hammer to a depth of 18 inches. The California barrel was equipped with brass liners to preserve the soil properly for laboratory tests, provided the sample remained intact within the liner. Blow counts or drive sample counts were recorded over three 6 -inch intervals in order to obtain a relative determination of the bearing capacity of the soil in general accordance with the American Society for Testing and Materials Standard Penetration Test (SPT) procedure (ASTM D 1586).1 SPT resistance values, when properly evaluated, indicate the relative density or consistency of the soils or materials penetrated. SPT sampling was conducted in each boring at 5 -ft intervals. Details of the sampling, soil classifications and descriptions of materials encountered, SPT blow counts, drilling and groundwater information were recorded on field boring logs by AAI's field representative. Information on the field boring logs was entered into a boring log program that creates a final format for report presentation. In addition to the conventional auger drill hole, a dynamic sounding (DS -1), was advanced alongside BH -39. The dynamic sounding consisted of a steel cone (1.5- inch - diameter) being driven using procedures outlined by ASTM D1586.1 The purpose of the dynamic sounding was to obtain a continuous log of the relative consistency of the alluvial materials present with particular attention to any soft, weak intervals that may not be identified by conventional auger drilling. 3.2 Subsurface Conditions The material encountered in the borings was somewhat consistent in that silty, sandy clay and clayey to gravelly sand overlies weathered sandstone bedrock. Approximately 10 ft of fill, consisting of gravelly to silty sand, is present in the area of BH -38. The depth of the alluvium varies from approximately 10 ft in BH -41 to approximately 20 ft in BH -38. Weathered bedrock underlies the alluvium. The thickness of the bedrock weathering is inconsistent and varies from nonexistent to approximately 5 ft. Underlying the weathered bedrock is unweathered bedrock consisting, in general, of weak, poorly cemented, medium to coarse - grained sandstone. The boring location of BH -38 and the drill rig used for the site investigation are illustrated in Photograph 3. American Society for Testing and Materials (ASTM), "Standard Test Method for Standard Penetration Test (SPT) and Split - Barrel Sampling of Soils," Designation D1586 -11. Agapito Associates, Inc.