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Mr.M. Scott Mansholt—CEMC Second Quarter 2006 Groundwater Monitoring and Sampling Report July 11,2006 US Can-Welty Road Page 4 of 5 No TPHg or BTEX were detected in the groundwater samples. No TPHd was detected in MW-5. TPHd at concentrations of 190 and 160 gg/L were detected in the field and field duplicate samples from WFSMW-1,respectively. No PAHs were detected in the groundwater samples during the second quarter 2006. The groundwater analytical results are presented in Tables 2 and 3. A petroleum-hydrocarbon distribution map is presented as Figure 4. A copy of the laboratory analytical report is included in Attachment B. QUARTERLY OLEOPHILIC SOCK REPLACEMENT An oleophilic sock was installed in well MW-1 due to the presence of SPO in the well and an oleophilic sock was placed in MW-2 due to the petroleum odor detected from the well. The socks in MW-1 and MW-2 have been monitored and replaced as necessary on a quarterly basis. During the second quarter 2006,the oleophilic sock from MW-1 was weighed but not replaced, and approximately 7 ounces (0.07 gallon)of SPO had been absorbed. The oleophilic sock from MW-2 was also weighed but not replaced, and approximately 5 ounces(0.05 gallon)of SPO had been absorbed. A summary of SPO thickness measurements is included in Table 1. QUALITY ASSURANCE/QUALITY CONTROL (QA/QC) All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis 3procedures. Based on SAIC's evaluation,all analytical data are usable as qualified for the purpose of determining chemical concentrations in groundwater at the site. The result for naphthalene detected in the equipment rinsate blank,QA-R,was qualified"J" because the concentration was between the laboratory method detection limit and reporting limit. The final result for this sample is 0.019 Jµg/L. The data usability summary and the laboratory reports are presented as Attachment B. Unless noted otherwise, analytical data collected in support of this investigation are considered precise, accurate,representative, complete, and comparable, and they may be used for their intended purposes. CONCLUSIONS AND RECOMMENDATIONS Groundwater elevations from the site wells indicate that groundwater flow was to the northeast at an approximate gradient of 0.001 ft/ft during the second quarter 2006. No dissolved-phase TPHg or BTEX appear to be present at the site. TPHd were detected in field sample and field duplicate samples collected from WFSMW-1 at concentrations of 190 and 160µg/L,respectively. No TPHd were detected in the sample from MW-5. No PAHs were detected in the groundwater samples during the second quarter 2006. SPO has been observed in wells MW-1 and MW-2 since 1999. TPHg and TPHd appear to be present in the SPO in the vicinity of wells MW-1 and MW-2. SAIC recommends continued quarterly groundwater monitoring and sampling of wells MW-1 through MW-5 and WFSMW-1. SAIC is preparing a work plan to properly destroy and replace wells MW-3 and MW-4 because the water volumes in these wells are insufficient for adequate sample collection. The work plan will be submitted during the third quarter of 2006. Oleophilic socks in wells MW-1 and MW-2 will be monitored quarterly and replaced as necessary. When 3. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Update).