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Mr. Ron Rowe Project 20805-146.010 <br /> February 2, 1998 <br /> Page 2 <br /> Evaluation Procedures <br /> EMCON will shut down the soil vapor extraction treatment system (SVETS) for a period <br /> of two weeks. After that time, EMCON will notify the SJCPHS of the date and time the <br /> SVETS will be restarted to allow the SJCPHS to be present. During the initial restart of <br /> system operation, EMCON will collect influent and effluent analytical data to evaluate the <br /> response of the petroleum hydrocarbon concentrations in the extracted soil vapor, <br /> specifically, benzene. EMCON will collect samples for laboratory analysis during the first <br /> and third hours of operation to evaluate the short term response of the subsurface soil <br /> vapor to pulsing of the system Additionally, EMCON will collect samples several times <br /> during the first week to assess the longer term response of influent benzene concentrations. <br /> A copy of the evaluation schedule is attached for your information and review. <br /> After collecting and analyzing samples from the treatment system at the site, EMCON will <br /> present the results in a letter report. The data will be used to evaluate whether the system <br /> has sufficiently completed the removal of petroleum hydrocarbons from the vadose soil at <br /> the site. If the SVETS has completed this goal, the system will be removed from the site. <br /> Tentatively, the start date for the SVETS is February 9, 1998. EMCON will confirm the <br /> date with SJCPHS one week before system start-up. <br /> If you have any questions or comments regarding this letter, please call one of the <br /> undersigned. <br /> Sincerely, <br /> EMCON <br /> Matt Turner 7a . Jo on,R.G. <br /> Remediation Manager nior oject Supervisor <br /> Attachment: Evaluation Schedule <br /> cc: Kyle Christie,ARCO Products Company <br /> Joel Coffman,EMCON <br /> SAC,N�PJO'M80"8051460.1AB-96\pmsmer.3 <br />