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July 14, 1992 THRIFTY OIL CO. <br /> s <br /> Mr Mike Infurna J 1 7 1992 <br /> �1�1�,� ! <br /> Public Health Services/Environmental Health Division QNiN4[N FA1� HE4� j <br /> County of San Joaquin PERMI1'I5E .'i4:ltr;) <br /> P O Box 2009 (1601 E Hazelton Ave ) <br /> Stockton, California 95201 <br /> RE -nnft Oil Ca—SWhon #172 <br /> 7647 Pacific Ave <br /> Stockton, CA 95207 <br /> Quarterly Monitoring Report <br /> Ist and 2nd. Quarter 1992 <br /> Dear Mr Infurna, <br /> This letter serves as a quarterly monitoring report for the above mentioned service station This status report <br /> presents site monitoring efforts during the months of January through June 1992 Thnfty Oil Co has retained Earth <br /> Management Co (EMC) to conduct quarterly monitoring and sampling activities at the site Reporting will be <br /> conducted by Thrifty in-house environmental staff No groundwater samples were collected during the first quarter, <br /> 1992 The most recent sampling event was accomplished by EMC on June 3, 1992 However, PHS/EHD was not <br /> contacted to observe the field procedures at that time EMC has been notified of this requirement and PHS/EHD <br /> will be notified in the future <br /> SITE REMEDIATION <br /> To date, no remediation of soil and groundwater has been conducted at the site As requested by PHS/EHD, a <br /> workplan for additional investigation at the site with regard to definition of the vertical and lateral extent of soil and <br /> groundwater contamination was submitted by Thrifty Oil Co in-house staff on April 14, 1992 <br /> GROUNDWATER M RIN <br /> The site was visited by an Earth Management Co (EMC) technician The EMC technician obtained depth to <br /> groundwater data and observed wells for the presence of free product Groundwater depth measurements were taken <br /> from the top of PVC we1l casing using an Oil Recovery Systems interface probe capable of measurements to within <br /> 0 01 feet Using the depth to groundwater and survey data for the site, a groundwater contour map was developed <br /> The contour map is presented as figure 2 The contour map suggests that the potentiometnc surface of the shallow <br /> groundwater is generally flat across the site with a slight southward trend The groundwater elevation has nsea <br /> about a foot since the last reporting, June 5, 1991 <br /> On June 3, 1992, groundwater samples were collected from the on-site wells by EMC personnel Prior to sample <br /> collection, at least three well volumes of groundwater were removed from each well by a portable submersible <br /> pump During the purging of groundwater, pH, conductivity,temperature and turbidity were monitored at selected <br /> intervals This data is included in Appendix A along with the gauging data for the reporting period Field water <br /> quality data sheets for the January sampling were not available from EMC All equipment was cleaned using a <br /> solution of Alconox and water followed by two tap water noses The actual groundwater samples were collected <br /> with a teflon bailer equipped with a bottom emptying device before being transferred into the laboratory supplied <br /> 40m1 VOA vials pending analyses The chain-of-custody documentation is presented in Appendix B. <br /> V O <br /> 10000 Lakewood Boulevard, Downey, California 90240 (310) 923-9876 <br />