ARCHIVED REPORTS_2021 CURRENT CONDITIONS RPT

Home Browse Search

24 May 2021 Project No. 14-3002 Page 19 of 23  TPH-g was detected in five soil and two waste samples at concentrations ranging from 1.2 mg/kg (B46-5) to 79.9 mg/kg (B40-17).  TPH-d was detected in twenty soil and five waste samples at concentrations ranging from 1.3 mg/kg (B45-5 and B46-14) to 2,400 mg/kg (B47-15).  TPH-mo was detected in eighteen soil and six waste samples at concentrations ranging from 5.5 mg/kg (B79-5) to 7,500 mg/kg (B47-15). TPH-d were detected at maximum concentrations of 1,990 mg/kg, 1,890 mg/kg and 2,400 mg/kg in soil samples B40-13, B40-17, and B47-15, respectively. These were the only concentrations that exceeded the ESL of 1,200 mg/kg. Concentrations of TPH-g and TPH-mo did not exceed their respective ESL, and detections of TPH-g were very limited. TPH impact appears to be limited to the higher range carbon chain (C10-C36). Analytical results of TPH in soil and waste are summarized in Table 2, and results of TPH-d in soil and waste are depicted in plan view in Figure 16 and in cross-sectional view in Figures 17 through 21. TPH-d and TPH-mo were detected in four groundwater samples collected from AOC2 at concentrations ranging from 98 µg/l to 1,000 µg/l of TPH-d and 380 µg/l to 6,100 µg/l of TPH-mo. TPH-d were detected above the MCL Priority of 200 µg/l in the samples collected from B65 and B79; there is no established MCL or MCL Priority for TPH-mo. TPH-g were not detected above the laboratory reporting limit of 50 µg/l in the groundwater samples collected from AOC2. Based on TPH detections in soil, waste, and groundwater and their respective screening and contaminant levels, AGI utilized TPH-d as the TPH of concern to evaluate the impact. Analytical results of TPH in groundwater are summarized in Table 3, and TPH-d results in groundwater are depicted in Figure 22. TPH-D EXTENTS (TPH) The vertical extent of TPH-d contamination in soil and waste extends to the water table in the locations of buried waste (B40 and B47). The three highest TPH-d concentrations, detected above the ESL, were located beneath buried waste at depths between 13 feet and 17 feet bsg; samples were not collected below 17 feet bsg in B40 and B47. The next highest TPH-d concentration was 1,100 mg/kg which was detected in B65 at 15 feet bsg. This result is just below the ESL and was also located beneath buried waste. A sample collected at 20 feet bsg in B65 was non-detect for TPH. Based on this data, the vertical extent of TPH-d contamination in soil and waste is defined and does not extend beyond 20 feet bsg in the areas where waste was encountered. Outside of the waste limits, TPH impact does not extend beyond six feet bsg (Figures 16 through 21).