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' Sulfolane Remedial <br /> Investigation Work Plan <br /> ARCADIS Former Occidental Chemical Corporation <br /> Lathrop, California <br /> soil samples. 107 soil samples(including six duplicate samples)were collected during <br /> ' three separate phases of the investigation.The boring locations are shown on <br /> Figure 3 and copies of the analytical data tables from the PW-18 Vadose Zone Soil <br /> Investigation(CRA 2008)are included in Appendix A. <br /> EDB and DBCP were not detected above their respective reporting limits(10 pg/kg)in <br /> soil samples collected from the 18 soil borings(513-1 through S13-18)advanced during. <br /> the first phase of the investigation. Therefore,subsequent soil samples collected in the <br /> vicinity of well cluster PW26 were not analyzed for EDB and DBCP. <br /> Sulfolane was detected in 23 soil samples collected from ten soil borings(SB-3,-3a, <br /> -23,-24,-24a,-25,-26,-27,-29,and S13-30).The highest sulfolane concentrations in <br /> soil were detected in samples collected from soil borings SB-3, SB-24,and SB-25. <br /> ' Sutfolane was detected in 23 soil samples collected at variable depths from ground <br /> surface to the water table from soil borings SB-3, SB-23, SB-24, SB-25, SB-26, SB-27, <br /> SB-29 and SB-30 above the cleanup level of 8,600 pg/kg. <br /> 3.2 Soil Data Gaps. <br /> ' Additional step-out borings are proposed to further delineate horizontal and vertical <br /> sulfolane impacts in the vadose zone above the cleanup level of 8,600 -glkg. Potential <br /> data gaps exist to the east of borings SB-29 and SB-30, southeast of boring SB-27, <br /> ' south of boring SB-22, and northeast of borings SB-3 and SB-24. Proposed boring <br /> locations are shown on Figure 4 and summarized on Table 1. <br /> ' 3.3 2008 Groundwater Investigation <br /> During the 2008 investigation,two borings(SB-3a and SB-24a)were advanced to <br /> approximately 70 feet bgs for collection of soil and groundwater samples. Seven <br /> groundwater samples(including one duplicate sample)were collected during the third <br /> phase of the investigation.These borings were located adjacent to the future location <br /> ' of groundwater well cluster PW26 as shown on.Figure 3. <br /> EDB and DBCP were not detected above their respective reporting limits(0.01 pg/L)in <br /> groundwater samples collected from the borings SB-3a and SS-24a. <br /> ' Sulfolane was detected in all seven groundwater samples above the health-based <br /> drinking water criterion of 57 pg/L at maximum concentrations of 53,000 pg/L(20 feet <br /> ' bgs),61,000 pg/L(46 to 50 feet bgs), and 1,400 pg/L(66 to 70 feet bgs). <br /> avec�. a,n wot„.a« 5 <br />