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exceeds the Tier 1 and EPA Tap Water ESLs of 0.46 ug/L, and organic lead, for which the reporting limit of 0.15 ug/L exceeds the EPA Tap Water ESL of 0.0013 ug/L. Petroleum: Recommendations OU 2 is located in the same area as OU 10. Because both were investigated for similar petroleum- and solvent-related compounds, these data (Tables 0U2-P and OU1O-P) can be combined into a single dataset, which yields 342 soil results, of which all are ND except for the two xylenes concentrations of 0.0056 and 0.0065 mg/kg detected at OU 2. While many reporting limits are not tabulated, these data strongly indicate that there are no petroleum-related issues at OU 2. Potential concentrations would be expected to be normally distributed. Such a distribution resulting in only 2 detections out of 342 soil results and 0 detections out of 57 groundwater results would have to fall well below reporting limits. Kleinfelder therefore recommends spot-checking the reporting limits to confirm they are reasonably low and therefore constrain potential concentration distributions as expected. Moreover, Hydropunch data provide direct evidence of groundwater conditions. These data are all ND. While Halogenated VOC reporting limits are not tabulated, BTEX are, and they are generally below associated groundwater ESLs. This strongly indicates that groundwater is effectively protected, no matter the soil data reporting limits. Kleinfelder therefore recommends that evaluation of spot-checked soil reporting limits be conducted with the context that direct groundwater data strongly indicate that groundwater has been protected. It is anticipated that this exercise will provide the Board the data it needs to demonstrate due diligence with respect to demonstrating that these data warrant no further action. OU 2 Work Plan Spot Check Slide Hammer Passive Soil Gas Survey Soil Vapor Soil Hydropunch Explorations Samples 22 (20%) Analyses Kleinfelder will use a random number generator to select 22 results (20% of the dataset). For each randomly selected result, Kleinfelder will assess the initial Phase ll paper-copy laboratory reports and tabulate the associated laboratory reporting/detection limits and screening levels. If a randomly selected result does not have an associated screening level, Kleinfelder will randomly select a new result. Kleinf elder will provide these data to the Board for its review. 20173951.001A/SAC17R68420 © 2017 Kleinfelder Page 6 of 26 November 2, 2017 www.kleinfelder.com KLEINFELDER 2882 Prospect Park Dr., Suite 200, Rancho Cordova, CA 95670 p I 916.366-1701 f I 916.366-7013