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September 17, 1991 for three monitoring wells at this site indicated a consistent groundwater gradient of approximately 0 0026 feet per foot in a northwest direction Details of the groundwater gradient review are provided in Kleinfelder's letter to SJCPHS, dated January 8, 1993 Based on the groundwater gradient review, Kleinfelder installed a single monitoring well northwest of the previous tank excavation to assess groundwater Two rounds of groundwater sampling were proposed Prior to conducting field activities at the site, Kleinfelder prepared a work plan dated October 29, 1992 for County approval The work plan included a map of the proposed well location, a drilling permit application, a health and safety plan, a description of Kleinfelder's drilling and well installation protocol, and the proposed well construction details Kleinfelder also prepared a work plan addendum dated January 8, 1993, which summarized the results of the groundwater gradient review and Kleinfelder's recommendation to install a single monitoring well The first groundwater assessment was conducted on February 3, 1993. Results from the laboratory reported low concentrations of TPH as diesel at 64 µg/l and benzene at 0 4 µg11 No concentrations of TPH as gasoline or toluene, ethylbenzene, and xylenes were detected above the laboratory analytical reporting limits in the first round The second groundwater assessment was conducted on May 26, 1993 Petroleum hydrocarbons were not detected in the second round of sampling FIELD ACTIVITIES, THIRD ROUND For the thud round assessment, one groundwater sample was collected from MW-1 The sample (80283) was collected on August 16, 1993 The sampling protocol was as follows Down-well equipment (water-level meter) was decontaminated by scrubbing in a trisodium-phosphate wash followed by a distilled water nnse, prior to use ► The depth to groundwater was measured using a conductivity-based water-level meter The water was measured at 18 01 feet below the casing surface on August 16, 1993 The volume of water standing in the well was calculated by subtracting the depth to groundwater measurement from the de,pth of the well and multiplying by the appropriate conversion factor (3 14*radius , 0 16 for 2-inch wells) The water sample was collected after purging four well volumes using a clean disposable bailer ► Physical parameters (pH, electrical conductivity, and temperature) were monitored for stability during purging The physical parameter measurements are recorded on purge- and-sample logs, along with the time and volume of water purged at each measurement. ► The sample was collected with a new disposable bailer and was contained in appropriately prepared bottles provided by the analytical laboratory New bailer cord also was used prior to use ► The sample was immediately labeled and placed in an iced sample container At the end of the day, the samples were shipped (by earner) in an iced cooler to Superior Analytical laboratory in San Francisco under chain-of-custody documentation 24-220172-AOO/DR4-60(1993) Page 2 of 4 August 30, 193 CopyWt 1993 Kleznfelder, Inc KLHNFECDEIZ 3077 Fite Circle, Sacramento CA 95827 (916) 366-1701