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THRIFTY OIL CO. <br /> April 29, 1996 <br /> Ms Linda Turkatte <br /> Public Health Services/Environmental Health Division <br /> County of San Joaquin <br /> P O Box 2009 (1601 E Hazelton Ave ) <br /> Stockton, California 95201 <br /> RE Thn Oil Company Station #171 <br /> 1250 North Wilson Way <br /> Stockton, CA 95205 <br /> Quarterly Monitoring Report, 1st Quarter 1996 <br /> Dear Ms Turkatte <br /> This letter serves as a progress monitoring report for the above mentioned service station This <br /> status report presents site monitoring efforts through the 1st quarter 1996. Thrifty Oil Co has <br /> retained Earth Management Co (EMC) to conduct quarterly monitoring and sampling activities <br /> at the site The data collected by EMC is reported by Thrifty in-house environmental staff <br /> SITE REMEDIATION <br /> To date, no remediation of soil or groundwater has been conducted at the site Thrifty recently <br /> completed a comprehensive subsurface investigation that included installation of several <br /> groundwater monitoring wells, vapor extraction wells and groundwater recovery wells Also, <br /> a vapor extraction pilot study was conducted to obtain preliminary data for implementation of <br /> a remediation system <br /> GROUNDWATER MONITORING <br /> The latest groundwater sampling event was conducted on February 13, 1996 The site was <br /> visited by an Earth Management Co (EMC) technician The EMC technician obtained depth <br /> to groundwater data and observed wells for the presence of free product Groundwater depth <br /> measurements were taken from the top of the PVC well casing using an Oil Recovery Systems <br /> interface probe capable of measurements to within 0 01 feet (Appendix A) Using the depth to <br /> groundwater and survey data for the site, a groundwater contour map was developed The <br /> contour map is presented as Figure 1 The contour map suggests that the potentiometric surface <br /> of the groundwater generally slopes to the east across the site, under a gradient of 0 005 <br /> FREE PRODUCT REMOVAL <br /> Since July 1995, no liquid phase hydrocarbon (LPH) has been detected on the water table in well <br /> • MW5 In 1993, the thickness of the LPH in this well ranged from 0 4 to 1 78 feet These data <br /> �7 10,000 Lakewood Boulevard, Downey, CA 90240 4082 • (310) 923-9876 <br />