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Mr. David DeWitt Page 5 November 2 , 1993 <br /> Unocal Corporation <br />• <br /> simulations, benzene reached the soil/ground water interface only <br /> in Simulation #3 . Upon contacting the ground water in the 11th <br /> year, however, the concentration of dissolved benzene was less than <br /> the California Department of Health Maximum Contaminant Level (MCL) <br /> of 1 ppb. Additionally, in ten months subsequent to initial <br /> contact with the ground water, the benzene concentration consis- <br /> tently attenuated to a non-detectable level . A detailed descrip- <br /> tion of the three SESOIL models and the results are included in <br /> KEI ' s report (KEI-P91-0202 .R7) dated March 18 , 1993 , which is <br /> attached to this letter. <br /> DISCUSSION <br /> Based on the analytical results of all of the soil and ground water <br /> samples collected and evaluated to date, there does not appear to <br /> be any significant soil or ground water contamination remaining at <br /> the subject site. Additionally, based on the results of the SESOIL <br /> computer simulation model, no significant impact to the ground <br /> water can be expected from the minimal soil contamination remaining <br /> at the subject site. Furthermore, KEI ' s previously conducted well <br /> survey indicates that it does not appear likely that any of the <br /> residual ground water contamination at the subject site could <br /> impact the identified potential receptor wells . Therefore, there <br /> does not appear to be a threat or a potential threat to the <br /> drinking water due to the previous operations at the subject Unocal <br /> site. <br />