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Shaw Environmental, Inc. <br /> 4005 Port Chicago Highway <br /> Concord, CA 94521 <br /> Phone: 925.288.9898 <br /> Fax: 925.288.0888 <br /> SaW" Shaw Environmental, Inc. <br /> August 4, 2003 <br /> Shaw Project No. 838819.48 <br /> Mr, Andrew Taylor <br /> SBC <br /> 2600 Camino Ramon; Room 93E000 <br /> San Ramon, California 94583 <br /> Subject: Letter Report for Quarterly UST Monitoring, Various SBC Facilities, <br /> California <br /> Dear Mr. Taylor: <br /> Shaw Environmental Inc. (Shaw) is pleased to present this letter report outlining underground <br /> storage tank (UST) quarterly monitoring activities completed at 16 SBC facilities located <br /> throughout California. These monitoring events are conducted on UST's that were temporarily <br /> closed under permit in December 2002. Monitoring is completed each quarter to ensure that the <br /> internal atmosphere within the UST's remains in compliance with permit conditions. _ <br /> Field Activities <br /> During the months of June and July 2003, Shaw visited the subject sites to perform quarterly <br /> monitoring of the USTs. The lower explosive limit (LEL) and percent oxygen were measured <br /> using a field-calibrated photoionization detector(PID)to observe that the levels remain below <br /> 10%, as required by the temporary closure permits and Shaw protocol. If initial LEL and percent <br /> oxygen readings were in excess of 10%, Shaw personnel first lowered them by adding dry ice at <br /> a rate of 20 pounds per 1,000 gallons of tank capacity, with additional dry ice added as needed. <br /> Time was then allowed for the dry ice to displace residual vapors and oxygen from the tank <br /> before measuring the final LEL and percent oxygen. The amount of dry ice used and the LEL <br /> and oxygen readings are summarized in Table 1. <br /> rNCDASHARFU1ST\GMOP.9 Hoc <br /> A Shaw Group Company. <br />