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November 16, 2005 <br /> NOA Project Number: E05120B <br /> None of the metals detected in the four samples analyzed were present above the Preliminary <br /> Remedial Goals (DRGs). Arsenic was detected in three samples at levels above the cancer endpoint <br /> PRG. It has been NOA's experience,however, that regulators may consider 5 mg/Kg an acceptable <br /> level of arsenic in soil, dependent upon background levels of arsenic in the area. Background levels <br /> of arsenic found by the Kearney Foundation Special Reports support this choice of a threshold <br /> value. Levels of arsenic were found to be below 5 mg/Kg in the three samples analyzed. <br /> 4.0 MANURE IMPACT INVESTIGATION <br /> Three boxings were advanced to groundwater on the site for the purpose of investigation into <br /> possible manure impacts to soil and nitrate impacts to groundwater. <br /> 4.1 Boring Locations and Methods <br /> The three borings were advanced on October 13, 2005 at the locations indicated on Plate 3. The <br /> borings were drilled by a B-53 Mobile Drill rig operated by NOA. Soil borings were advanced using <br /> 6.5-inch hollow stem augers. The soil cuttings brought to the surface were examined by the on-site <br /> geologist,who produced a log of each boring(Appendix A). <br /> Boring B-1 was advanced to a depth of 40 feet below ground surface (bgs),B-2 was advanced to 20 <br /> feet bgs,and B-3 was advanced to 30 feet bgs. The total depth of each boring was determined by <br /> • the depth to water. Flowing sands were encountered at boring B-1 at depths from 29 to 40 feet bgs, <br /> requiring drilling to greater depth to obtain a collectable water sample. <br /> 4.2 Depth to Groundwater <br /> Groundwater was encountered at 29 feet bgs in boring B-1,at 17.5 feet bgs in boring B-2, and at 26 <br /> feet bgs in boring B-3. <br /> 4.3 Sample Collection <br /> One groundwater sample was collected from each boring. At boring B-2,potentially manure- <br /> impacted soils (based on observations of color and smell)were observed within the boring from <br /> approximately 9 to 20 feet bgs. As a result,two soil samples were collected from the drill cuttings at <br /> that boring, from depths of approximately 15 and 20 feet bgs. <br /> $Kearney Foundation of Soil Science,Division of Agriculture and Natural Resources,University of California, <br /> 1996,Background Concentrations of Trace and Major Elements in California Soils. <br /> • 6 <br />