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r <br /> THRIFTY OIL CO. <br />'. February 5, 1993 <br /> Mr Mike Infurna <br /> Public Health Services/Environmental Health Division Rk:Urm I VE20 <br /> County of San Joaquin <br /> P O Bax 2009 (1601 E Hazelton Ave) FE9 10 1993 <br /> Stockton, California 95201 ENVIRONMENTAL <br /> HEALTH <br /> RE &notr co station 11172 <br /> PERMIT/SERVICES <br /> � <br /> 7647 Pacific Ave <br /> Stockton, CA 95207 <br /> Quarterly Monttonng Report <br /> 41h. Quarter 1992 <br /> Dear Mr Infurna, <br /> This letter serves as a quarterly monitoring report for the above mentioned service station Tlus status report <br /> presents site monitoring efforts during the months of October, November and December Thrifty Oil Co has <br /> retained Earth Management Co (EMC) to conduct quarterly monitoring and sampling activities at the site The <br /> data is reported by Thrifty in-house environmental staff <br /> SITE REMEDIATION <br /> To date, no remediation of soil and groundwater has been conducted at the site As requested by PHS/BHD, 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 This workplan will <br /> be evaluated after more data is collected from the wells <br /> A survey of the wells within a 1/2 mile of the site was conducted by SSB Environmental Consultants m July, 1991 <br /> Their findings were included in the initial site investigation report titled "Preliminary Assessment of Soil and <br /> Groundwater Quality at Thrifty Oil Company Station No 172, 7647 Pacific Avenue, Stockton, California", dated <br /> July 17, 1991 <br /> GROUNDWATER MONITORING <br /> On November 24, 1992,The site was visited by an Earth Management Co (EMC)technician The EMC technician <br /> obtained depth to groundwater data and observed wells for the presence of free product Groundwater depth <br /> measurements were taken from the top of PVC well casing using an Oil Recovery Systems interface probe capable <br /> of measurements to within 0 01 feet Using the depth to groundwater and survey data for the site, a groundwater <br /> contour map was developed The contour map is presented as Figure 2 The contour map suggests that the <br /> potentiometric surface of the shallow groundwater is generally flat across the site with a slight eastward trend <br /> Groundwater samples were collected from the on-site wells by EMC personnel Prior to sample collection,at least <br /> three well volumes of groundwater were removed from each well by a portable submersible pump or bailer During <br /> the purging of groundwater, pH, conductivity,temperature and turbidity were monitored at selected intervals This <br /> data is included in Appendix A along with the gauging data for the reporting period All equipment was cleaned <br /> using a solution of Alconox and water followed by two tap water rinses The actual groundwater samples were <br /> collected with a teflon bailer equipped with a bottom emptying device before being transferred into the laboratory <br /> supplied 40m1 VOA vials pending analyses The chane-of-custody documentation is presented in Appendix B. <br /> QQ �� <br /> 10000 Lakewood Boulevard, Downey, California 90240 (310) 923-9876 <br />