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Mr. M. Scott Mansholt—CEMC <br /> Third Quarter 2006 Groundwater Monitoring and Sampling Report October 25, 2006 <br /> Vernalis Pump Station Page 5 of 5 <br /> data are usable as qualified for the purpose of determining chemical concentrations in <br /> groundwater at the site. Qualified data with applicable reason codes are shown in Table B-1 of <br /> Attachment B. <br /> Unless noted otherwise, analytical data collected in support of this investigation are considered <br /> precise, accurate, representative, complete, and comparable, and they may be used for their <br /> intended purposes. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Groundwater elevations from the site wells indicate that groundwater flow was to the east at an <br /> approximate gradient of 0.001 ft/ft during the third quarter of 2006. No dissolved-phase TPHg or <br /> BTEX appear to be present at the site. TPHd were detected in the samples from MW-7 and the <br /> MW-7 field duplicate sample during the third quarter of 2006 at concentrations of 62 gg/L and 52 <br /> gg/L, respectively. TPHd detection may be attributed to laboratory cross-contamination since <br /> TPHd were also detected in the laboratory method blank. PAI-Is were not detected in any samples <br /> during the third quarter 2006 :monitoring event. SPO has been observed in well MW-1 since <br /> 1998. <br /> SAIC will continue quarterly monitoring at this site as recommended in the RWQCB letter dated <br /> September 20, 2006. TPHg and BTEX have not been detected during quarterly monitoring <br /> events at site wells. SAIC recommends removing TPHg and BTEX from the analytical suite for <br /> fixture sampling events. The oleophilic sock in well MW-1 will be monitored quarterly and <br /> replaced as necessary. When the petroleum sheen has been removed, SAIC recommends that <br /> well MW-1 be incorporated into the monitoring and sampling program. <br /> CLOSING <br /> If you have any questions regarding this report, please call Chris Dennis at(916) 979-3866. <br /> Sincerely, <br /> SCIENCE APPLICATIONS INTERNATIONAL CORPORATION <br /> A- Geo <br /> Suzet e Villanueva Christopher B. Dennis, P.G. <br /> Staff Scientist Senior Geologist Ok CHRISTOPHER <br /> IL B. 4 <br /> Enclosures: DENNIS <br /> Figure 1. Vicinity Map N0.7184 4 <br /> Figure 2. Site Map <br /> Figure 3. Potentiometric Surface Map Third Quarter 2006 OF CALF <br /> Figure 4. Petroleum Distribution in Groundwater Third Quarter 2006 <br /> Table 1. Groundwater Elevation Data and SPO Thickness Measurements Expires August 3t 'Z <br /> Table 2. Groundwater Analytical Results—THPd, TPHg, and BTEX <br /> Table 3. Groundwater Analytical Results—PAHs <br /> Attachment A: Field Data Sheets <br /> Attachment B: Data Usability Summary and Laboratory Analytical Report <br />