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