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OU 10: Work Plan <br />Spot <br />Check <br />Slide <br />Hammer <br />Passive <br />Soil Gas <br />Survey <br />Soil Vapor Soil Hydropunch <br />Explorations <br />Samples 23 (10%) <br />Analyses <br />Kleinfelder will use a random number generator to select 23 results (10% of the dataset). For <br />each randomly selected result, Kleinfelder will assess the initial Phase II paper-copy laboratory <br />reports and tabulate the associated laboratory reporting/detection limits and screening levels. If a <br />randomly selected result does not have an associated screening level, Kleinfelder will randomly <br />select a new result. Kleinfelder will provide these data to the Board for its review. <br />OPERABLE UNIT 11 <br />Description <br />OU 11 Corresponds to Sub-Recommendations 21.1 and 21.2, which concern two rail spurs that <br />enter the Site from its southeast corner and then run west toward its center. The Phase I identified <br />potential for soil contamination via spills from rail cars of offsite metal- and petroleum-related <br />compounds. The Phase I also identified potential for pesticide/herbicide use for rail spur <br />maintenance. Phase II samples were collected and analyzed for metal- and petroleum-related <br />compounds and pesticides/herbicides. <br />Metals: Existing Data <br />Eleven soil samples were analyzed for CAM 17 metals (Table OU11-M, soil samples 6-6 through <br />6-13). Concentrations are all below Industrial Thresholds, but arsenic concentrations and <br />laboratory reporting limits exceed the Industrial Threshold. Moreover, cobalt and mercury results <br />and arsenic and thallium laboratory reporting limits exceed Protection of Groundwater SSLs. <br />Kleinf elder analyzed these metal concentrations against those from OU 7 (Table 0U7-M, soil <br />samples 12-8 through 12-16) and OU 11 (Table OU11-M, soil samples 6-6 through 6-13). Metal <br />concentration distributions from OU 1 and OU 7 are very similar, despite samples being collected <br />from two separate areas to assess potential for two separate means of potential contamination. <br />This indicates OU 1 and OU 7 metal concentrations represent natural background concentrations. <br />Some OU 11 metal concentrations exceed typical OU 1 and OU 7 concentrations. Specifically, <br />arsenic, copper, lead, nickel, and zinc are all substantially higher, both when calculating average <br />concentrations with and without NDs. Examination of concentration data indicates these above- <br />average concentrations are not due to isolated, anomalously high results; the majority of results <br />are typically 2- to 3-times higher than OU 1 and OU 7 averages. This indicates that these elevated <br />metal concentrations are likely caused by Site operations identified in the Phase I rather than <br />anomalous samples. <br />20173951.001A/SAC17R68420 Page 20 of 26 November 2, 2017 <br />© 2017 Kleinfelder www.kleinfelder.com <br />KLEINFELDER 2882 Prospect Park Dr., Suite 200, Rancho Cordova, CA 95670 p I 916.366-1701 f (916.366-7013