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CanonteEnvlronmental <br /> Canome En;�. ental Services Corgi <br /> 1710 Main Street17 <br /> March 10, 1995 Esca4on California 9320 <br /> 94-312-01 TIO � F Phone 209 838 3507 <br /> Phone 800 926 0806 <br /> Fax 209 838 3509 <br /> Mr Brad Wiest <br /> Chevron U S A Production Company <br /> P O Box 158 <br /> Rio Vista, CA 94571 <br /> Subject Groundwater Monitoring and Sampling at Chevron USA Production Company, <br /> 540 North Aurora Street, Stockton, California <br /> Mr Wiest: <br /> This letter report has been prepared by Canonie Environmental Services Corp (Canonie) at the <br /> request of Chevron USA, Inc (Chevron) and discusses recent groundwater sampling and <br /> monitoring activities conducted at the subject site (Plate 1). <br /> GROUNDWATER MONITORING AND SAMPLING <br /> • On February 6, 1995, a Canonie technician monitored fluid levels in each monitoring well <br /> Groundwater levels have risen an average of 2 81 feet since last measured in August 1994 <br /> Groundwater elevation data is summarized in Table 1. A groundwater gradient map was <br /> created using the February 6, 1995 data (Plate 2) Groundwater flows to the north with a <br /> gradient of 0 025 feet/foot or approximately 130 feet/mile <br /> A Canonie technician collected groundwater samples from monitoring wells MW1, MW2, and <br /> MW3 on February 6, 1995, according to the field procedures outlined in Attachment 1 Field <br /> purge logs are contained in Attachment 2. Collected groundwater samples were transported <br /> under chain of custody to State-Certified Sequoia Analytical Laboratories in Redwood City, <br /> California A trip blank was transported to the laboratory along with the collected <br /> groundwater samples All samples were analyzed for total petroleum hydrocarbons as gasoline <br /> (TPHg), total petroleum hydrocarbons as diesel (TPHd), benzene, toluene, ethylbenzene, and <br /> xylenes (BTEX) utilizing EPA Methods 8015 modified and 8020 <br /> CONCLUSIONS AND RECOMMENDATIONS � <br /> No petroleum hydrocarbon constituents were detected in any sample collected from monitoring <br /> wells MW2 or MW3 Unidentified peaks were detected at 51 parts per billion (ppb) in the <br /> diesel range in the sample collected from well MW 1 However, the laboratory reported that <br /> • the chromatogram pattern of the sample does not match the diesel standard and its <br /> 1501031QUARTMQR-0395 doe <br />