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I i events The March 17, 2004 and June 3, 2004 sampling data were obtained prior to system start- up The June 21-22, 2005 sampling data was information obtained approximately 12 months after system operation start-up Although there are possible reductions in the areal extent of TPHg dunng this quarter, significant reductions of TPHg concentrations are apparent along the infection well corridor(Figure 23) 5 0 CONCLUSIONS TPHgdetected in the groundwater samples collected from MW6a indicates the hydrocarbon plume extends offsite to the shallow aquifer MTBE detected in groundwater samples collected from MW6b, MW6c, MW7a, MW7b MW7c, MW10a, and MW10b indicate the MTBE plume extends offsite to the east in deeper groundwater MTBE concentrations to MW7a, MW7b and MW10a are below action levels MTBE concentrations in MW6b and MW6c increased when compared with the December 13, 2004 groundwater monitoring event BTEX components were not detected during the June 21-22, 2005 event in MW4, MW5, MW6a, MW6b, MW6c, MW7a, MW7b, MW7c, MW8, MW9a, MW9b, MW9c, MW10a, MW10b and MW10c Benzene, toluene, ethylbenzene and/or xylenes were detected in MW1, MW2, MW3 and EW1 during the June 21-22, 2005 event Benzene appears to be declining or cleaned-up or below typical action levels due to the C- SpargeTM operation in MW1, MW2, MW3, MW4 and EW-1 DO also increased significantly after system start-up in MW 1 from 0 36 mg/L on June 3, 2004 to 10 54 mg/L during the June 21- 22, 2005 event suggesting a further correlation System effectiveness with respect to MTBE in the Jamar on site wells appears to be positive for MWI and EW1 The responses (i e , destruction of MTBE) to the system operation for MW2 and MW4 are not as clear 6.0 RECOMMENDATIONS Based on the results of the second quarter 2005 monitoring episode, ATC makes the following recommendations • Conduct third quarter groundwater monitoring and sampling ofMW1 through MW10C and EW1 and analyze the samples for TPHg, BTEX, MTBE, ETBE, DIPE, TBA, TAME, 1, 2-DCA and EDB • Conduct monthly groundwater monitoring and sampling for field parameters including DO and ORP in the on-site remediation well network (MW1 -MW5, MW8 and EWi) • Continue operation and monitoring of the C-SpargeTM system for existing parameters and include electrical meter readings • • Separate quarterly groundwater monitoring reporting from System O&M reporting • Reduce system O&M reporting to semi-annual 51268231QM repoM\2005 2ndQR doe 12