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Monitoring Wells MW#4S and MW#4D were installed on the east side of Wilson Way in September of <br /> • 2000 Also monitoring wells MW#5D,M W#6S and M W#6D,MW47S and MW#7D were installed north <br /> and south ofthe pump islands in September of 2000 (see attached Site Map) <br /> Monitoring wells MW#8S and MW8D were installed in a single bore hole inside the existing building,west <br /> of the pump islands on October 3, 2000 <br /> FOURTH QUARTER 2001 MONITORING WELL SAMPLE ANALYSIS REPORT <br /> Sampled 12/13/2001 <br /> WATER ANALYSIS OF SAMPLES FROM MONITORING WELLS <br /> On December 13, 2001, Del-Tech Geotechnical Support Services extracted water samples from each <br /> monitoring well using Standard industry practices under the supervision of Foothill Frigineering A report <br /> ofthis woik by Del-Tech Geotechnical Support Services is attached and is apart of this report The water <br /> samples were transported ort ice by chain of custody to Sherwood Labs for analysis by Method S W8020 for <br /> BTEX, and 1 l'Hg <br /> • FINDINGS FROM GROUNDWATER SURFACE DETERMINATION <br /> The groundwatcr elevation on this site has risen 4 8'from the measurements done on September 13,2001 <br /> and is about 6' lower than in the fourth quarter of last year The slope of the groundwater gradient for this <br /> event is to the northeast at S = 0 0018 <br /> FINDINGS FROM MONITORING WELL SAMPLE ANALYSIS <br /> Fhe concentration of 1'PHg in monitoring wells MW#1,MW#2 M W#3,M W#6D,MW97S,and M W#8S <br /> are higher than last quarter All of the remaining monitor wells indicate concentrations ofTPHg the same <br /> or lower than the third quarter MW#4D,MW#6D,and M W#7Dare non-detect for all analyzed compounds <br /> this quarter Be monitoring well MW#4S on the eastside of Wilson Way has indicated very low <br /> concentrations of BTEX compounds (See attached sample data recap sheets) <br /> CONCLUSIONS <br /> fhe water table elevations on this site continue to fluctuate as high as six feet per quarter On similar sites <br /> in Stot kton the water table elevation varies no more than two feet between quarters High volume <br /> agricultural pumping offsite most likely is the reason for this large variation in water surface elevations <br /> RECOMMENDATIONS <br /> A review of groundwater receptors to the area of the site should be conducted to help determine the cause <br /> of the change in groundwater elevation and flog gradient direction <br /> The groundwaLe, sample results gathered by the last four groundwater sample events indicate that both the <br /> vertical depth and hoi tzontal limits of the contamination have been reached and further investigation below <br /> . a depth ofone hundred feet is not required Quarterly groundwater sampling of all monitoring wells should <br /> continue <br />