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' IT Corporation-- <br /> 4005 Port Chirago Ili-hual <br /> Concord C 1 94520 1120 <br />' Tel 925 288 9898 <br />,,,he Fax 925 288 0888 <br /> 1 Alemhrr oI Tltr 1 r L(t;group <br /> 1, <br /> October 15, 1999- <br /> Mr Bob DeNinno _ <br /> 7-Eleven, Inc <br /> 1 10220 S W Greenburg Road, Suite 470 <br /> Portland, OR 97233 <br />' Subject Third Quarter 1999 Monitoring and Sampling Report <br /> 7-Eleven Store No 99976 <br /> 1399 North Main Street <br /> Manteca, California <br /> Ir IT Project No 779956 <br /> Dear Mr DeNinno <br /> This Third Quarter 1999 Monitoring and Sampling Report presents the results of monitoring and sampling <br /> activities performed by IT Corporation at the subject site (Figures 1 and 2, Attachment 1) on September 14, <br /> M 1999 A summary of activities conducted during this reporting period is provided below <br /> ® Depth to water(DTW)was gauged in eight site-related groundwater monitoring wells MW-1, <br /> 1 MW-1A, MW-2, MW-3 and the recently installed MW-4, MW-4A, MW-5 and MW-5A <br /> ■ Groundwater samples were collected from the eight monitoring wells and submitted to a California- <br /> certified laboratory for analysis of benzene, toluene, ethylbenzene and total xylenes (BTEX), total <br /> petroleum hydrocarbons-as-gasoline (TPH-G), methyl-tert-butyl-ether(MTBE), tert-butanol (TBA), <br /> diisopropyl ether(DIPS), ethyl-tert-butyl ether(ETBE), and tert-amylmethyl ether(TAME) <br /> tGroundwater Monitoring Data <br /> tGroundwater monitoring of the wells was performed on September 14, 1999 Before monitoring, the well <br /> caps were opened to allow the water in each well to stabilize to atmosphenc pressure The DTW was _ <br /> measured to the nearest 0 01 foot from the top of the well casing using an ORS Environmental Equipment <br />' INTERFACE PROBE TM Well Monitoring System <br /> Two potentiometric surface maps were prepared using the groundwater elevation data collected on <br /> September 14, 1999 Based on the groundwater elevation data, groundwater flow in the shallow water- <br /> bearing zone is toward the northwest and north at a gradient of approximately 0 004 ft/ft (Figure 2) Based <br />' on the groundwater elevation data collected from the deeper groundwater monitoring wells 1A, 4A and 5A, <br /> groundwater flow in the deeper water-bearing zone is also toward the northwest and north at a slightly <br />