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.al ` THIRD QUARTER 2000 MONITORING WELL SAMPLE ANALYSIS REPORT Sampled 10/09/2000 r� WATER ANALYSIS OF SAMPLES FROM MONITORING WELLS On October 9, 2000, Del-Tech Geotechnical Support Services extracted water samples from each monitoring well using standard industry practices under the supervision of Foothill Engineering A report of this work by Del-Tech Geotechnical Support Services is attached and is a part of this report The water samples were transported on ice by chain of custody to Sherwood Labs for analysis by EPA Methods 602 and 5030/8015(M) for BTEX, and TPHg, and EPA Method 8260B for oxygenates FINDINGS FROM MONITORING WELL ANALYSIS The most important change for this reporting period is a+I-6 5 feet drop in the ground water elevation The direction and slope of the hydraulic gradient have changed significantly The direction of flow is to the east at the time of this event The slope of the gradient is from S=0 001 (see attached site drawing) The concentration of TPHg has decreased in monitoring wells MW#1 and MW#3 Monitoring well MW#2 was analyzed at the same concentration level for TPHg as the last event All compounds of BTEX in MW#1 and MW43 have been reduced (see attached sample data recap sheets) All analysts for oxygenates were non-detect for each of the monitoring wells CONCLUSIONS The 9 8 feet drop in the groundwater table elevation from the 3/16100 event is a significant change in the site conditions This pattern of large variations in groundwater elevations may contribute to the change in contamination levels found in the last two sampling events There is a general downward trend in the levels of contamination in the groundwater from the first sampling event on 9/22/99 After five quarters of sample analysis for oxygenates, all water samples have been non-detect RECOMMENDATIONS A review of groundwater receptors in the area of the site should be conducted to help determine the cause of the change in groundwater elevation and flow gradient direction It is the opinion of the author that further action to determine the extent of the vertical and horizontal limits of the contamination plume should wait until the fourth quarter water samples have been analyzed The results from the first water samples of the latest set of monitoring wells indicate that low concentrations of gasoline contamination are present at one hundred feet of depth This may be a result of contamination transported down the bore hole from soil boring operations and it may take the purging of a few sampling events to remove this contamination There is no indication that oxygenates are present in the groundwater on this site To conserve financial resources, analysis for oxygenates will not be continued without a request of the PHS-EHD 3