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SEMI-ANNUAL SAMPLING EVENT REPORT OF 3/17/05 SAMPLING PROCEDURE Monitoring wells were vented and purged by normal methods per standards of the industry (see Groundwater Field Report by Del-Tech Geotechnical Services attached) Purge pump rates were +/-0 5 gallons per minute in all monitoring wells,except for MW-5S which was purged at 2gpm Groundwater samples were extracted from each monitoring well using the check valve in tube technique Samples were transported on ice under chain of custody for delivery to Sherwood Labs for analysis WATER TABLE ELEVATIONS AND GRADIENT Soundings on the monitoring wells showed the groundwater elevation has raised 5.2 feet from the last soundings on 9/15/04 The hydraulic gradient of the water table is bearing to the east at S=0 009 WATER SAMPLE ANALYSIS FINDINGS Test were performed for BTEX, TPHg, Oxygenates, 1,2 DCA, and EDB EPA 624 was not performed for solvents Monitoring well samples taken on 3/17/05 were very similar to the previous sample events when analyzed for BTEX and TPHg MW-3S continues to produce samples with BTEX compounds and TPHg as determined by EPA Method 5030/8015(M) TPHg in MW-3S was analyzed at 668 ug/T' 1,2-Dichloroethane,continues to be present in all of the wells with the exception of MW-2D,MW- 4S and MW-4D Monitoring well MW-5D had the highest recorded values of the compound 1,2- Dichloroethane at 32 ug/L. CONCLUSIONS BTEX compounds in the monitoring well MW-3S remain in the same range as the past events 1,2- Dichloroethane remains in monitoring wells MW-1, MW-2S, MW-3S, MW-3D and MW-5S and MW-5D There are two compounds that continue to be above drinking water levels, benzene and 1,2- Dichloroethane Comparing current values to the initial values,shows a natural attenuation process is taking place The well with benzene over drinking water levels is MW-3S. The wells with 1,2- Dichloroethane over drinking water levels are MW-3S, MW-5S, MW-5D RECOMMENDATIONS The author requests that all monitoring wells continue to be sampled in semiannual events to conserve financial resources Please contact this office at (91 W53 y questions arse from this report : OBERT Respectfully submitted, E Foo tt�l E fne t' 707 . 1Vjlchae Vla it EXP 12-31-05 /3 1 j� d' CIV 11 `q- 1� /[J cc Mrs Helen Higgins, 5815f Pte 6, Stockton CA 95219 2