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1 <br /> ' ARCADIS Ms. Kathryn Dominic <br /> August 24, 2010 <br /> ' Soil cleanup levels for metals in CAO No. 92-707 are provided as extractable <br /> concentrations (per the WET method) and are therefore not directly comparable to <br /> ' the results for the soil samples above. These concentrations are; however, below the <br /> United States Environmental Protection Agency(USEPA) Region 9 preliminary <br /> remediation goals (PRG), which are 280 mg/kg for total chromium and 400 mg/kg for <br /> ' lead (http://www.epa.gov/region09/superfund/prq/). <br /> Groundwater cleanup levels for these metals provided in CAO No. 92-707 are <br /> ' 50 pg/L for chromium and 15 pg/L for lead. <br /> RWQCB Request: The RWQCB requested in the February 19, 2009 letter to UPRR <br /> ' that representative soil samples be collected from the Biotreatment Beds and <br /> analyzed using the DI-WET for metals. The RWQCB also requests that groundwater <br /> samples be collected from beneath and downgradient of the Biotreatment Beds for <br /> ' analysis of total chromium, total lead, and PAI-Is (PAHs were discussed previously). <br /> ARCADIS Response: ARCADIS did not analyze soil or groundwater samples for <br /> metals because based on historic site use and soil sampling data presented in the <br /> Remedial Investigation(RI) Report(Industrial Compliance 1994), metals were not <br /> ' COCs for sludge or soil removed from the TPCA pond and placed in the <br /> Biotreatment Beds.According to the Remedial Investigation(RI) Report(Industrial <br /> Compliance 1994), groundwater sampling over several years has shown that metals <br /> ' detected in groundwater are likely from an upgradient metals plating company. <br /> In addition, the biotreatment methods used to remediate the TPCA pond soil and <br /> ' sludge entailed mixing nutrients into the soil and aerating the soil by tilling to promote <br /> aerobic bioremediation of petroleum hydrocarbons (i.e. TPH-d). The post remediation <br /> investigation sampling objective was to verify the effectiveness of the biotreatment. <br /> ' The biotreatment methods were not intended to remediate metals in soil and aerobic <br /> bioremediation is not an effective remediation method for metals. Therefore, post <br /> remediation analysis of soil and groundwater for metals was not considered. <br /> Post-Remediation Soil Sampling and Analysis Methodology <br /> ' Soil samples were collected during March 2010 by ARCADIS staff from six locations <br /> as shown on Figure 1. Soil samples were collected at each location from two depths, <br /> 1 and 3 feet below ground surface (ft bgs). Based on a biotreatment bed thickness of <br /> ' 2 feet, the intent was to collect one soil sample from within the biotreatment bed (1 ft <br /> bgs)and to collect one soil sample from the bottom or from just below the <br /> Page: <br /> ' 7/12 <br />