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' M Infurna Project No 1232 April 21, 2000 Page 2 for TPH, BTEX, and M1 BE The analytical results are presented in Table 2 and Appendix A which contains copies of the chain of custody records and laboratory reports ' To evaluate qualitatively the efficiency of remediation efforts, samples of ground water were obtained from wells MW-2, MW-3, VE-3, and VEW-4 on March 27, 2000 The samples were ' obtained using a non-purge method Analytical results comparatively to the results obtained in the third and fourth quarters are presented in Table 8 ' 3 0 REMEDIATION RESULTS ' Since start-up, the unit had been in operation for 1,771 hours removing approximately 7,333 pounds of petroleum hydrocarbons from impacted soil and ground water The calculated amount of TPH, benzene, toluene, ethylbenzene, and xylenes and corresponding the destruction ' and removal efficiency of the thermal oxidizer are presented in Tables 3, 4, 5, 6 and 7, respectively The analytical data from the second round of testing indicates the presence of low concentrations of MTBE in the extracted soil vapor, which was not detected in the first round EPA Method TO-3, which was the analyses used on the vapor samples, is a GC method which does not quantified MTBE 4.0 CONCLUSIONS ' The remediation unit has been operating in full compliance with the Permit to Operate issued by the SJVAPCD During the reporting period, the unit operated for 1,356 hours of the 1,771 ' total operating hours and removed approximately 3,232 pounds of the 7,333 pounds of total petroleum hydrocarbons from impacted soil and ground water The concentration of hydrocarbons in extracted soil vapor indicated ten-fold reduction comparatively to the previous testing There are two possible reasons for this reduction 1) the concentration of dissolved hydrocarbons was reduced to the point when removal of hydrocarbons is being controlled by diffusion, or 2) rising ground water level caused by heavy rains reduced the extraction efficiency To verify the concentration of hydrocarbons in the extracted air, it is proposed to take a soil vapor sample by the middle of May 2000 The conceniraiion of dissolved hydioeaibons in ground water exhibited a decieasing trend in three of four wells sampled However, the concentration of dissolved hydrocarbons in monitoring well MW-3 showed the sharp increase with no obvious reasons except that this well is located in proximity of the "hot" spot at the former Unocal site ' ENVIRONMENTAL AUDIT, INC