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21 October 2020 <br />Project No. 14-3002 <br />Page 15 of 15 <br />approximate extent of TPH-impacted soil is depicted in Figure 9. <br /> Based on the data collected, TPH impact migrated laterally, until it encountered <br />waste, and then migrated vertically through the waste. TPH was only detected at <br />or beneath 10 feet bsg in borings where waste was encountered. Additionally, <br />TPH-d and TPH-mo were generally detected in groundwater samples collected <br />from borings with waste (B46, B48, B65). The maximum dissolved TPH <br />concentrations were detected in the groundwater sample collected from B65, <br />waste was encountered in B65 from 8.5 to 13 feet bsg. Dissolved TPH and waste <br />were not detected in B67 (Tables 7 and 8). <br /> Total lead was analyzed and detected in three waste samples at a maximum <br />concentration of 160 mg/kg. The concentrations were below the DTSC-SL of <br />320 mg/kg and ESL of 380 mg/kg (Table 7). <br /> Dioxin/Furans were analyzed and detected in four waste samples at TEQ <br />concentrations ranging between 2.19 pg/g and 96.6 pg/g. Two of the four <br />concentrations were above the ESL of 22 pg/g (Table 7). Waste samples collected <br />during the previous investigation also detected dioxin/furans above the ESL. <br /> Total lead was detected in groundwater samples collected from B46, B48 and B65 <br />at concentrations between 0.017 mg/l and 0.37 mg/l. The concentrations exceed <br />the MCL of 0.015 mg/l. However, the samples were inadvertently analyzed for total <br />lead and not dissolved lead. Based on data collected during the previous <br />investigation, dissolved lead is not a risk to groundwater at the site (Table 8). <br /> Dioxin/Furans were detected in the groundwater samples collected from B46, B48 <br />and B65 at TEQ concentrations between 0.0126 pg/l and 0.723 pg/l. The <br />concentrations detected were significantly below the MCL of 30 pg/l for <br />dioxin/furans (Table 8). <br /> <br /> <br />7.0. LIMITATIONS <br /> <br />Our professional services were performed using that degree of care and skill ordinarily <br />exercised by environmental consultants practicing in this or similar localities. The findings <br />were based upon field measurements and analytical results provided by an independent <br />laboratory. Evaluations of the hydrogeologic conditions at the site for the purpose of this <br />investigation are made from a limited number of available data points (i.e. field data, soil, <br />waste, and groundwater samples) and subsurface conditions may vary away from these <br />data points. No other warranty, expressed or implied, is made as to the professional <br />interpretations, opinions and recommendations contained in this report.