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Mr.M. Scott Mansholt—CEMC Third Quarter 2006 Groundwater Monitoring and Sampling Report October 25,2006 US Can-Welty Road Page 4 of 5 The groundwater analytical results are summarized and compared with the RWQCB Region 2 Environmental Screening Levels(ESLs)and the numerical State WQOs in Tables 2 and 33. Analytical results exceeding the most conservative ESL or WQO are highlighted in Tables 2 and 3 in bold-type font. TPHg or BTEX were not detected in the groundwater samples. TPHd were not detected in MW-5. TPHd at concentrations of 230 µg/L and 120 µg/L were detected in the field and field duplicate samples from WFSMW-1,respectively. These concentrations are above the TPHd WQO of 100 gg/L. PAHs were not detected except for a trace detection of phenanthrene(0.013 µg/L)in the field and field duplicate samples from WFSMW-1,which is below the most conservative WQO and ESL. It should be noted that trace phenanthrene was detected in the equipment blank and TPHd were detected in the laboratory method blank sample at 36 gg/L. 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 and the data usability summary are presented as Attachment B. Starting the second quarter 2006, laboratory analytical data are being qualified. Please see Attachment B for details regarding data qualifiers. 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 third quarter 2006,the oleophilic socks from MW-1 and MW-2 were inspected. The sock in MW-1 was replaced, and approximately 17 ounces(0.16 gallon)of SPO was removed. The sock in MW-2 was replaced, and approximately 13 ounces(0.12 gallon)of SPO was removed. 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 4procedures. Based on SAIC's evaluation,all analytical data are usable as qualified for the purpose of determining chemical concentrations in groundwater at the site. Qualified data with applicable reason codes are shown in Table B-1 of 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 east at an approximate gradient of 0.001 ft/ft during the third 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 230µg/L and 120 gg/L,respectively. No TPHd were detected in the sample from MW-5. PAHs were not detected except for a trace 3. The ESLs(provided as a reference)are a tool based on conservative standard exposure factors for initial human health and the environment screening-level evaluations of analytical results. The WQOs are defined by the Porter- Cologne Act as"the levels or limits of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area." 4. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Update).