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THRIFTY MIL CO . <br /> August 3, 1998 <br /> Mr Michael J Infurna, Jr Q�y &PAD <br /> Senior REHS d a <br /> Site Mitigation Unit IV/LOP rr <br /> 304 East Weber St , Fifth Floor <br /> Stockton, California 95202 W <br /> RE Thrifty Oil Co. Station #171 <br /> 1250 North Wilson Way <br /> Stockton, Ca <br /> 1st Quarter„1998 <br /> Dear Mr Inf ima <br /> Presented herein is the Status Report prepared for Thrifty Oil Co Station #171 located at 1250 <br /> Wilson Way, Stockton, Ca (Figure 1) Presented in this report are the results of the quarterly <br /> groundwater monitoring program This report presents data collected during the period from January <br /> • thru March, 1998 <br /> GROUNDWATER MONITORING <br /> depth to groundwater is measured in each monitoring well on a quarterly basis Gauging data <br /> obtained from February 11, 1998 is presented in Table 1 In general, groundwater occurs under <br /> water table conditions beneath the station at depths ranging from 47 20 to 49 22 feet below ground <br /> surface(bgs) A groundwater elevation contour map based upon February 11, 1998 data is presented <br /> as Figure 1 The general direction of groundwater flow beneath the site is toward the east-northeast <br /> with a gradient of approximately 0 17 foot/feet <br /> Quarterly Groundwater Sampling <br /> As part of the groundwater monitoring program, groundwater samples were obtained from <br /> monitoring wells MW-3R, MW-4, MW-5, MW-6, TB-1, TB-7, TB-8, and TB-10 Groundwater <br /> samples were obtained by Earth Management Co (EMC) and delivered in a chilled state in a light <br /> proof ice chest following strict Chain-of-Custody procedures to a state certified laboratory and <br /> analyzed for volatile organic hydrocarbons by EPA method 8020,and total petroleum hydrocarbons <br /> (TPH) by EPA method 8015 modified Figure 2 indicates dissolved TPH, figure 3 indicates <br /> dissolved benzene, and figure 4 indicates dissolved MTBE concentrations in groundwater <br /> Starting in the third quarter of 1997, as required by the Central Valley Regional Water Quality <br />. Control Board (CVRWQCB), samples were analyzed for Oxygenates by EPA Method 8260 The <br /> Qo <br /> 13539 E Foster Rd, Santa Fe Springs, CA 90670-0138•(562)923-9876 <br />