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Kennedy/Jenks Consultants <br /> Section 6: Summary of Findings and Conclusions <br /> This section presents the findings of the subsurface investigations performed at the former <br /> Union Pacific Tracy Railyard in December 2005 and January 2006. The findings are presented <br /> below for each operable unit, followed by site-wide findings. <br /> 6.1 Operable Unit 1 <br /> Eighteen soil borings were advanced in OU-1 and a total of 58 soil samples were collected and <br /> submitted for analysis of total and soluble lead. Many of these samples did not contain soluble <br /> lead at concentrations exceeding analytical reporting limits, but in those samples where soluble <br /> lead was detected, the concentrations of soluble lead corresponded well with concentrations of <br /> total lead in the same sample. <br /> ' With the exception of Boring OU1-A013-S9, in borings where relatively higher concentrations of <br /> lead were encountered in surface or near-surface soil samples, the lead concentrations <br /> decreased with increasing depth. Boring 0U1-A013-S9 was located west of A012 (area of <br /> previously excavation). <br /> Surface soil samples collected from 11 borings advanced in OU-1 contained total lead at <br /> concentrations exceeding residential CHHSL and PRG values. <br /> Groundwater samples were not collected from OU-1 during this field investigation. <br /> 6.1.1 OU-1 AOI 1 <br /> None of the eight soil samples collected from the two borings advanced in the previously <br /> remediated soils in AOI 1 contained total or soluble lead at concentrations exceeding the <br /> residential CHHSL or PRG values. The largest total lead concentration in these samples was <br /> 23 mg/kg and the largest soluble lead concentration in these samples was 0.75 mg/1. <br /> 6.1.2 OU-1 AOI 2 <br /> The total lead concentrations in near-surface soil samples collected from five of the six soil <br /> borings advanced in AOI 2 exceed residential CHHSL and PRG values. The elevated lead <br /> concentrations appear to be limited to near-surface soil. <br /> 6.1.3 OU-1 AOI 3 <br /> The total lead concentrations in surface and/or near-surface soil samples collected from six of <br /> the ten soil borings advanced in AOI 3 exceed residential CHHSL and PRG values. With the <br /> exception of Boring OU1-A013-S9 noted above, concentrations of total lead decrease with <br /> increasing depth, suggesting that the elevated lead concentrations are limited to surface and <br /> near-surface soils. <br /> DRAFT Phase I Remedial Investigation Report Page 39 <br /> Former Tracy Railyard, Tracy, California <br /> g,\is-groupladminGob10510565777.18_uprr 09-reportslri rpNext.doc <br />