C.1.2.6 Targeted Spill Area DU ISM Results

Figure C.1-5 and Table C.1-2 summarize the reported concentration of PCBs in ISM samples collected from the 28-36 and 36-60 inch depth intervals of the central spill area DU. The concentration of PCBs was highest for the fine soil fraction (<0.063mm), although the mass of PCBs is present in the <2 mm to >0.25 mm soil fraction, which makes up 75%-80% of the samples from both intervals. Based on a weighted average of the individual size-fraction data, the total concentrations of PCBs in the <2 mm soil fraction from the two targeted intervals are 15 mg/kg and 33 mg/kg, respectively.

Table C.1-2. Incremental soil sample results for central spill area

DU Sample interval Grain size fraction (mm) Sample weight (g) Percentage of sample (%) PCB concentration (mg/kg)
17 28-36 inches >2 mm 110 9 3.88
<=2 to >0.25 mm 975 83 14.1
<0.25 to >=0.063 mm 95 8 25.8
<0.063 mm 1.5 0.1 72.7
Weighted average (<2 mm): 15
18 28-36 inches >2 mm 220 19 2.31
<=2 to >0.25 mm 880 74 33.2
<0.25 to >=0.063 mm 82.5 7 44.7
<0.063 mm 2.5 0.2 81.6
Weighted average (<2 mm): 33