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WIFETSIVIR'""M"M Mr. Mike Infurna j April 26, 2004 J Page 3 Soil Vapor Extraction System Status Since starting the remedial system in November 1999, the thermal oxidizer has operated for a fill total of 6,410 hours and removed approximately 8,462 pounds of petroleum hydrocarbons from impacted soil and groundwater. On September 30, 2003, Environmental Audit, Inc. of Placentia, CA (EAI) recommended that the SVE system be shut down. In a letter dated October 23, 2003, the RWQCB concurred with EAI's recommendation to shut down the SVE system and to continue to operate the AS system in a pulse operational mode. �i A summary of SVE system operational parameters, destruction efficiencies, and mass flow rates are presented in Tables 4 through Table 9, respectively. 1. Air Sparginig System Status The AS system typically operates in a pulse operations mode (week on 1 week off basis). The sparge compressor only operated intermittently during the first quarter 2004 due to necessary repairs. ENSR intends to operate the system on a pulse basis during the second quarter 2004. According to the hour meter on the AS system, it has operated for approximately 19,743 hours w since remediation at this site began in November 1999. Effectiveness of Remediation System System effectiveness is evaluated by assessing groundwater data from monitoring wells MW-2, MW-3, MW-11, and MW-12. Concentrations of TPHg, benzene, and MtBE in groundwater Fsamples collected from selected wells screened in Unit A or Unit B are depicted'graphically on cross section A-A' (Attachment E). Concentrations of TPHg, benzene, and MtBE in groundwater samples collected from selected wells screened across Unit A, Unit B and Unit D � are depicted graphically on cross-section B-B' (Attachment E). Concentrations of TPHg and F! benzene vs. depth to groundwater are depicted graphically in Attachment F. RMtBE was detected in groundwater samples collected from monitoring wells MW-9 and MW-25S at concentrations of 0.65 micrograms per liter (pg/L) and 0.58 pg/L, respectively, during the first quarter 2004 groundwater monitoring and sampling event. None of the remaining groundwater monitoring wells that were sampled on during the first quarter sampling event contained MtBE, according to laboratory results. MtBE was not detected at or above laboratory reporting limits in groundwater samples collected during fourth quarter 2003. ENSR will continue to monitor the i site for MtBE. Soil vapor samples were collected from selected SVE wells and monitoring wells utilized for the SVE system. Samples collected during the first quarter 2004 were submitted to Air Toxics LTD in Folsom, California for analyses of VOCs by Modified EPA Method TO-3. Historical analytical results for soil vapor samples collected from selected wells are summarized in Table 10. Tabular results of recent soil vapor sampling analytical results are summarized in Table 11. J:1Projects10694015098-2931FinallReportsllst otr'04-QMR RSR.doc ' 35 Years of Excellence in Environmental Services