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Canepa's Car Wash 6230 Pacific Avenue,Stockton CA Second Quarter Groundwater Monitoring Report May 2006 Page 6 of 8 Vapor Phase Volume Measurements The airflow though the treatment system catalytic oxidizer has averaged approximately 278 cubic feet per minute (CFM) since system start-up During the second quarter of 2006 the average flow was _ _approximately 278 1_CFM Approximately 50% of the airflow is from the groundwater air-stripper and approximately 50% from the array of nine soil vapor extraction wells Laboratory analysis of a vapor sample collected from the effluent of the air-stripper and another vapor sample collected from the effluent of_the_soil vapor extraction welIs,_both_collected at-the_time_of-start-up,-indicated TPH-G-concentrations of 2 9 and 690 parts per million (ppm), respectively The TPH-G input to the catalytic oxidizer,therefore, is primarily from the soil vapor extraction wells This is confirmed by weekly FID measurements - Vapor_Phase-Concentration7Measurements,Calculations,and Quantification During the second quarter 2006, vapor samples were collected from the catalytic oxidizer influent and effluent for laboratory analyses on March 30, 2006 PID measurements of the influent and effluent were also collected at that time For the March 30, 2006 laboratory analyses, TPH-G was not detected at or above the laboratory reporting limit of 20 0 ppm in both influent and effluent samples Corresponding PID measurements for the March 30, 2006 influent and effluent analyses were 9 0 ppm and 0 1 ppm, respectively A correlation has historically been created between the TPH-G concentrations obtained from the laboratory sample analyses and the PID measurement to provide an empirical correction factor for the PID measurements However, because TPH-G was not detected in the March 30, 2006 samples, a correlation was instead created between the laboratory-reported benzene concentration and the PID measurements This correlation was created for concentrations from the system influent as well as the system effluent The correction factor for the PID is adjusted on an on-going basis for both system influent and effluent samples The data and calculations can be found in Appendix D, SVE Vapor Stream Sample Laboratory Analytical and PID Results - Fifteen PID measurements of the system influent and effluent were collected between January 31, 2006 and May 18, 2006 The average PID influent measurement was 40 5 ppm and the average effluent measurement was 0 1 ppm The average corrected PID reading is calculated using the above mentioned correction factor, resulting in an average corrected influent PID measurement of 18 3 ppm The average -—corrected-PID-value-wasmultiplied�by`�the-laboratory-supplied conversion factor of approximately 4 mg/m3 for TPH-G in different units for use in following calculations_The unit_conversion resulted in an _ average-influent concentration of 73-2 irig/m -An-average airflow of 278 1-CFM was then used to calculate the mass of approximately 108 8 pounds of TPH-G removed by the system during the second quarter of 2006 A similar calculation procedure was followed for the system effluent to calculate the TPH-G released by the system to the atmosphere Using the airflow of 278 1 CFM, the mass of TPH-G released by the system was calculated to be approximately 4 76 pounds, resulting in a destructive efficiency of approximately 95 6%for the period s Vapor Phase Destructive Efficiency Of the approximately 10,637 4 pounds of TPH-G removed by the soil vapor extraction system and air- stripper to'date, the catalytic oxidizer destroyed approximately 10,468 6 pounds and approximately 168 8 pounds have been released to the atmosphere This results in an overall destructive efficiency of approximately 98 4% A worksheet showing the SVE calculations for the current quarter is included in Attachment D, SVE Mass Removal Calculation Worksheet SUMMARY The concentration of MTBE at MW-3 was lower than detected during the third and fourth quarters of 2005, but still remains at elevated levels compared to historically lower levels when monitoring began in August of 1996 EDB was detected for the third consecutive quarter in MW-1 (5 2 pg/L) The J CONDOR