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Groundwater Elevation Data Depth to groundwater was obtained from the existing groundwater monitor wells at the site using a water level indicator graduated to 0 01 foot The depth to groundwater measurement was converted to a groundwater elevation for each well and used to construct a potentiometric surface map (figure 2), and calculate the local groundwater flow direction and hydraulic gradient The groundwater potentiometric surface elevation averaged approximately 73 61 feet below ground surface (bgs) during this monitoring event The groundwater flow direction during this reporting period appears to converge on site Historical groundwater flow has been predominantly to the southwest A summary of data regarding groundwater levels measured through October 13, 1997, is presented in Table 1 Copies of field observations documenting work performed at the site is presented in Attaclunent 1 Groundwater Analytical Results The distribution of groundwater sample analytical results obtained from monitor wells at the site on October 13, 1997, is presented on Figure 2 and summarized in Table 2 Gasoline and BTEX were present at detectable concentrations in each of the samples submitted for analysis Chemical analytical results indicate the highest concentrations of TPHg and benzene are in the vicinity of monitor well MW-1 TPHg concentrations in groundwater samples ranged from 35,500 parts per billion(ppb) in monitor well MW-1,to less than detectable levels in samples collected from monitor well MW-10 Benzene concentrations ranged from below the laboratory method detection limit (<0 5 ppb) in monitor wells MW-7 and MW-10, to 921 ppb in MW-1 MTBE was reported with a • concentration of 10 9 ppb in a sample collected from monitor well MW-4, and less than detectable levels in samples collected from the remaining monitor wells Attachment I1 contains photocopies of the laboratory analytical reports and the chain-of-custody form Purgewater Purge water generated during groundwater purging was transported by Integrated Waste Management, Inc to Mckittrick Waste Treatment Site, in Mekittrick, California, for treatment and disposal FORTHCOMING ACTIVITIES During the first quarter of 1998, SECOR will conduct additional well monitoring, purging, and sampling activities The results of these activities will be summarized in a quarterly monitoring report to be submitted to you in April 1998 This report presents our understanding of existing conditions at the subject site The conclusions contained herein are based on the analytical results and professional judgment which are in accordance with current standards of professional practice, no other warranty is expressed or implied SECOR assumes no liability for exploratory borings or data reported by other consultants or contractors SECOR LCKFRDgm 497 2 January 2H 1999 7G005-On 1 01