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21 December 2017 <br />AGE-Project No. 14-3154 <br />Page 5 of 23 <br /> <br />4.2. ADDITIONAL INVESTIGATIONS <br /> <br />Following the preliminary investigation in December 2014, the owners of the subject <br />property submitted the data to the LEA and requested a path to obtain a clean closure for <br />the subject property to develop the site. The following is a summary of the investigations <br />performed as required by the LEA to achieve a clean closure of the subject property. <br /> <br /> Subsurface Trenching/Exploration– April 2015: In April 2015 trenches T1 through <br />T23 were established within the former waste/glass handling area. The trenches <br />were excavated through the minor amounts of residual glass waste and into <br />underlying native soil to further investigate soil and waste identified in this area of <br />the subject property. Trenching logs and tabulated field data for the trenches are <br />included in Appendix B. Discrete soil samples were collected under the waste <br />between four and five feet bsg and from the generated soil/waste stockpile. For <br />this investigation, the LEA only directed the native soil and waste to be analyzed <br />for CAM 17 metals. Cover soil was observed over the glass waste at depths <br />between two feet and five feet bsg. Glass waste and fine glass dust or the waste <br />component of glass (dolomite, limestone and soda ash) were observed to be <br />minimal; one foot thick and locally indurated (hardened). Various CAM 17 metals <br />were detected in the trench (T1 through T23) and stockpile samples (S1 through <br />S23) at concentrations below the DTSC-SLs and RSLs or at levels consistent with <br />background concentrations in California soils. Analytical results are summarized <br />in Table 1. <br /> Soil Sampling Investigation – July 2015: On 22 July 2015, a total of six soil samples <br />were collected approximately 12 to 18 inches bsg (ABSP1A-ABSP2C) from areas <br />of lower topographic relief to the east and south of the waste/glass handling area. <br />The depth of these soil samples was approximately 8 to 10 feet below the natural <br />land grade and therefore are not considered to represent shallow soils. In August <br />2015, two deeper soil samples were collected at the location of ABSP2B, at depths <br />of 1.5 feet and 3.0 feet below the surface (ABSP2B-1.5 and -3.0). A total of four <br />soil samples collected from these areas indicated minor detections of a PCB <br />(Aroclor 1254) at concentrations ranging between 0.05 milligrams per kilogram <br />(mg/kg) and 0.72 mg/kg (Table 5). The DTSC-SL (May 2015) established for <br />general PCBs is 0.78 mg/kg, which is greater than the concentrations of PCBs <br />detected in the soil samples collected during the 2015 investigation (Table 5). <br />Various metals were detected in the soil samples at concentrations below the <br />DTSC-SLs and RSLs or at levels consistent with background concentrations in <br />California soils (Tables 1-3). <br />Dioxin and furans were detected in two soil samples (ABSP2B and ASSP2C) <br />collected within the areas of lower topographic relief, south of the former <br />waste/glass handling area. Dioxins and Furans were detected at a maximum toxic <br />equivalency (TEQ) of 1.26 picograms per gram (parts per trillion). The conversion <br />of 1 milligram per kilogram is equal to 1, 000,000 picograms per gram (pg/g), which <br />is parts per trillion (ppt). The concentrations of dioxin and furans in these soil