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0 0 to assess the local groundwater gradient Water level measurements on August 23 and 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 ugll and benzene at 0 4 ug/l No concentrations of TPH as gasoline or toluene, ethylbenzene, and xylenes were detected above the laboratory analytical reporting limits in the first round The most recent groundwater assessment was conducted during May 1993 FIELD ACTIVITIES, SECOND ROUND For the second round assessment, two groundwater samples were collected from MW-1 The first sample (73497 to 73499 ) was collected on May 13, 1993 The second sample (73490 to 73491) was collected on May 26, 1993 The second sample was collected on May 26, 1993 because the TPH as diesel analysis was not included in the May 13, 1993 sampling The sampling protocol was as follows ► Down-well equipment (water-level meter) was decontaminated by scrubbing in a tri sodium-phosphate wash followed by a distilled water rinse, prior to use P. The depth-to-water was measured using a conductivity-based water-level meter 11The volume of water standing in the well was calculated by subtracting the depth-to- water measurement from the depth of the well and multiplying by the appropriate conversion factor (3 14*radius2, 0 16 for 2-inch wells) ► The water sample was collected after purging 20 well volumes (during the well development) 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 carrier) in an iced cooler to Superior Analytical laboratory in San Francisco under chain-of-custody documentation 24-220172-Ao0/FR11-72(1993) Page 2 of 4 Copyright 1993 Kleinfelder, Inc KLEINFELDER 3077 Fite Circle, Sacramento, CA 95827 (916) 366-1701