SITE INFORMATION AND CORRESPONDENCE (2)

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Mr. M. Scott Mansholt--CEMC Fourth Quarter 2006 Groundwater Monitoring and Sampling Report and Annual Summary Report January 12,2007 Vernalis Pump Station Page 7 of 7 concentrations appear stable within the range of fluctuation. PAH concentrations remained stable at low concentrations. SPO has been observed in well MW-1 since 1998 and a total of 0.16 gallon has been extracted from that well. SAIC will continue quarterly monitoring at this site as recommended in the RWQCB letter dated September 20,2006. TPHg and BTEX have not been detected in groundwater at the site wells and will be eliminated from future analytical sampling events beginning first quarter of 2007. The oleophilic sock in well MW-1 will be monitored quarterly and replaced as necessary. When the petroleum sheen has been removed, SAIC recommends that well MW-1 be incorporated into the monitoring and sampling program. CLOSING If you have any questions regarding this report, please call Chris Dennis at(916) 979-3866. Sincerely, SCIENCEAPPLICATIONS INTERNA TIONAL CORPORATION NAL O� CHRISTOPHER 0, r'C. �6LIuy_'M C_ �' '".� - B. tA Laura Sanc ' Christopher B. Dennis, P.G. DENNIS � Staff Geologist Senior Geologist N0.7184 Enclosures QP CA'_%F_ � Figure 1: Vicinity Map Figure 2: Site Map Expires August 31 , Figure 3: Potentiometric Surface Map—Fourth Quarter 2006 Figure 4: Petroleum Distribution in Groundwater During 2006 Figure 5: Potentiometric Surface Map—First Quarter 2006 Figure 6: Potentiometric Surface Map—Second Quarter 2006 Figure 7: Potentiometric Surface Map Third Quarter 2006 Table 1: Groundwater Elevation Data and SPO Thickness Measurements Table 2: Groundwater Analytical Results—THPd,TPHg, and BTEX Table 3: Groundwater Analytical Results—PA-Hs Table 4: Summary of Groundwater Flow Direction and Gradient Table 5: Monitoring Well Construction Details Attachment A: Field Data Sheets Attachment B: Data Usability Summary and Laboratory Analytical Report