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Mr.M. Scott Mansholt—CEMC 2008 Annual Groundwater Monitoring and Sampling Report April 16,2008 US Can-Welty Road Page 4 of 6 gallon of SPO was removed from each of these wells. A total of approximately 0.39 gallon of SPO has been removed since June 1999 from wells MW-1 and MW-2. SPO has not been detected in the other site wells. A summary of SPO thickness measurements is included in Table 1. QUALITY ASSURANCE/QUALITY CONTROL All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis procedures. SAIC's evaluation concluded that 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. 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 unless noted otherwise. CONCLUSIONS AND RECOMMENDATIONS The 2008 annual groundwater monitoring and sampling event was conducted between January 28 and 30,2008. Groundwater elevation at the site varied from 71.16 feet(MW-1)to 71.47 feet (MW-2)feet above MSL with a flow gradient toward the east at 0.001 ft/ft. The groundwater flow direction has historically been east/southeast and the groundwater elevation at the site has ranged from 70.19 to 73.09 feet above MSL. The average groundwater elevation at the site is 71.53 feet above MSL. TPHd were detected above the WQO and ESL in MW-3 at 1,600 gg/L(1,300 gg/L after silica-gel cleanup). PAHs were detected above ESLs or WQOs in MW-3. MW-3 had the following PAHs exceeding screening levels: benzo(a)anthracene at 0.033 gg/L,benzo(a)pyrene at 0.015 gg/L, benzo(b)fluoranthene at 0.032 gg/L(MW-3 Duplicate), and chrysene at 0.30 gg/L. January 2008 was the first time MW-3 was sampled since March 2006 due to insufficient water or inaccessibility. Well MW-4 indicated no detectable concentrations of TPHd or PAHs. The oleophilic socks in wells MW-1 and MW-2 exhibited SPO staining during the 2008 annual monitoring and were therefore replaced. Approximately 0.01 gallon of SPO was removed from each of these wells. SPO has been observed in wells MW-1 and MW-2 since 1999 with a total of 0.39 gallon of SPO removed from these wells to date. SAIC recommends the following based on the above conclusions: • Continue monitoring the oleophilic socks in wells MW-1 and MW-2 on an annual basis (during the first quarter); • Abandon MW-4 and MW-5 in accordance with the San Joaquin County well abandonment regulatory requirements; and 2. SAIC,2007. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. April (Update).