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the installation of an SVE system utilizing wells W-1 through W-8 for the abatement of residual <br /> petroleum hydrocarbons in soil beneath the site (SECOR, May 27, 1998) <br /> In September 1998, SECOR performed a Tier 1 and Tier 2 Risk-Based Corrective Action <br /> (RBCA) evaluation to examine whether residual petroleum hydrocarbons posed a risk to <br /> human receptors, establish site-specific cleanup levels, and to assist in the preparation of a <br /> corrective action plan (CAP) for the site A comparison of subsurface petroleum hydrocarbons <br /> In sod and groundwater to American Standard Testing and Materials (ASTM)-established risk <br /> based screening levels (RBSLs) Indicated that concentrations of benzene and toluene in soils at <br /> depths greater than 5 feet bgs, and benzene in groundwater exceeded the RBSLs for selected <br /> exposure pathways detailed in Appendix D Residual petroleum hydrocarbon concentrations in <br /> soil less than 5 feet bgs did not exceed the Tier 1 RBSLs for the any exposure pathways <br /> I evaluated Results of Tier 2 analysis indicated that site-specific target levels (SSTLs) were <br /> exceeded for the following exposure pathways (1) residual benzene in soil greater than 5 feet <br /> bgs for the on-site commercial worker inhalation of vapors to indoor and outdoor air scenarios, <br /> (2) toluene concentrations in soil greater than 5 feet bgs for the on-site commercial worker <br /> inhalation of vapors to indoor air pathway, and (3) benzene in groundwater for the inhalation of <br /> vapors by commercial and residential human receptors into Indoor air Based on the RBCA <br /> evaluation, SECOR determined that active remediation of residual petroleum hydrocarbon <br /> impacts beneath the site to below SSTLs was required for the protection of human health, and <br /> proposed the Installation of an SVE/air sparging (AS) system for mitigating petroleum <br /> 1 hydrocarbon impacts beneath the site <br /> Construction of the SVE/AS system was completed in December 1999, and Its configuration <br /> consisted of seven SVE wells (W-1, W-3 through W-8), two groundwater monitoring wells <br /> modified for SVE (MW-1 and MW-3), and four AS wells (AS-1 through AS-4) The SVE system <br /> was equipped with catalytic oxidation treatment to control emissions from the SVE wells Initial <br /> start-up air discharge compliance testing was completed on December 13, 1999 The system <br /> operated continuously from December 1999 to September 2003, at which time the remediation <br /> system was shut down with the approval of SJCPHD due to low soil vapor influent <br /> concentrations At the request of the SJEHD on June 14, 2004, SECOR restarted the <br /> remediation system on June 18, 2004 as a result of the re-appearance of liquid phase <br /> hydrocarbons (LPH) In well MWA The SVE/AS system was cycled on and off for two-week <br /> periods through November 19, 2004 The SVE/AS system was shut down at that time with the <br /> approval of the SJCEHD due to the lack of increase in influent soil vapor petroleum hydrocarbon <br /> concentrations Operation of the SVE/AS system from December 1999 through November <br /> 2004 has resulted in the estimated removal and treatment of approximately 38,894 2 pounds of <br /> TPHg and 233 2 pounds of benzene from beneath the site Remedial system performance data <br /> Is Included in Table 6 The layout of the SVE/AS system Is presented on Figure 3 <br /> In February 2000, approximately 4 79 feet of liquid phase hydrocarbons (LPH) was detected In <br /> MWA during the first quarter 2000 groundwater monitoring and sampling event Assessment of <br /> the physical appearance (clear) of the LPH, and Its presence in the subsurface soil vapor <br /> extraction (SVE) piping suggested that the LPH was the result of condensed soil vapor To <br /> Investigate the possibly of a new release at the site, the site inventory records and leak <br /> detection systems were checked, and a visual comparison was made between the LPH and the <br /> three grades of gasoline dispensed at the site Inventory records and leak detection systems <br /> were normal, and the LPH did not visually match the colored grades of gasoline dispensed at <br /> Time Oil Asmt&SCM doc 5 March 17,2005 <br /> 770T 41658 00 0015 <br />