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IT Corporation 4005 Port Chica;o Ihghxa; Concord C4 94520 1120 Tel 925 288 9898 10he 0 Far 925 288 0888 � ,soup A 11c mber of Thi IT Gro,y December 27, 1999 Mr Bob DeNEnno 7-Eleven, Inc 10220 S W Greenburg Road, Suite 470 Portland, OR 97233 Subject Fourth Quarter 1999 Monitoring and Sampling Report Former Southland Store No 20632 4627 DaVinci Drive Stockton, California IT Corporation Project 779962 Dear Mr DeNinno This Fourth Quarter 1999 Monitoring and Sampling Report presents the results of monitoring and sampling activities performed by IT Corporation on November 24, 1999, at the subject site (Figures 1 and 2, Attachment 1) A summary of activities conducted during this reporting period is provided below • ■ Depth to water(DTW)was gauged in four site-related groundwater monitoring wells, MW-1 through MW-3, and MW-5 ■ Groundwater samples were collected from the four monitoring wells and submitted to a California-certified laboratory for analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX), total petroleum hydrocarbons-as-gasoline (TPH-G), and the oxygenates methyl-tert- butyl-ether(MTBE), tert-butanol (TBA), dnsopropyl ether(DIPS), ethyl-tert-butyl ether(ETRE), and tent-amyl-methyl ether (TAME) Groundwater Monitoring Data Groundwater monitoring of the four wells was performed on November 24, 1999 Before monitoring, the well caps were opened to allow the water in each well to stabilize to atmospheric pressure The DTW was measured to the nearest 0 01 foot from the top of the well casing using an interface probe A potentiametnc surface map was prepared using the groundwater elevation data (Figure 2) Based on the groundwater elevation data, groundwater flow is toward the southwest at a gradient of 0 002 ft/ft The groundwater monitoring results from the November 24, 1999 monitoring and sampling event and historical monitoring results are presented in Table 1 (Attachment 2) Field data streets are included in Attachment 3 a•