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Mr.M. Scott Mansholt—CEMC Fourth Quarter 2006 Groundwater Monitoring and Sampling Report and Annual Summary Report January 12,2007 US Can-Welty Road Page 6 of 8 those results exceeding the most conservative ESL or WQO are highlighted in bold-type font. TPHg or BTEX were not detected in the groundwater samples. TPHd at a concentration of 970 gg/L were detected in the field sample from WFSMW-1,which exceeds the TPHd WQO of 100 gg/L. Low concentrations of TPHd were detected in samples from MW-3 and MW-5 at 60 gg/L and 77 gg/L,respectively. Naphthalene(0.054 µg/L)was detected in the sample from WFSMW-1, and fluoranthene(0.011 gg/L) and pyrene(0.041 µg/L)were detected in the sample from MW-3. The detected PAH concentrations are below the most conservative WQOs and ESLs. It should be noted that trace TPHd were detected in the laboratory method blank sample at 33 gg/L. A petroleum-hydrocarbon distribution map is presented on Figure 4. The laboratory analytical report and data usability summary, as well as details regarding data qualifiers, are presented as Attachment B. QUARTERLY OLEOPHILIC SOCK REPLACEMENT An oleophilic sock was installed in well MW-I 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-I and MW-2 have been monitored and replaced as necessary on a quarterly basis. During the fourth quarter 2006,the oleophilic socks from MW-I and MW-2 were inspected and re- deployed down the wells because SPO was not observed on the socks. 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 13 procedures. 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-I 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. ANNUAL SUMMARY 2006 Quarterly groundwater monitoring and sampling began at the site in the second quarter of 2005. Depth to groundwater recorded during 2006 ranged between approximately 31.08 feet btoc in MW-5 to 36.76 feet btoc in WFSMW-1 (Table 1). Groundwater flow during 2006 was toward the east at an average gradient of 0.001 ft/ft. A summary of groundwater flow directions and gradients is presented in Table 4, and the previous 2006 quarterly potentiometric surface maps are presented as Attachment C. The site wells are constructed with screen lengths of approximately 25 to 45 feet bgs. Depth to groundwater has ranged from approximately 31 to 37 feet bgs, indicating that the site wells are appropriately screened to monitor the upper water-bearing zone beneath the site. A summary of well construction details is presented in Table 5. No TPHg or BTEX were detected in any groundwater samples during 2006. TPHd were consistently detected at WFSMW-I during 2006 at concentrations ranging from 66 to 970 gg/L. 13. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Update).