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Quik Stop Station No 039 June 15, 2000 . Stockton. California_ Quarterly Groundwater Monitoring Report to Kiff Analytical (Ki$), a California Department of Health Services-certified analytical laboratory (FLAP No 2236) located in Davis, California The samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene, toluene, ethylbenzene and total xylenes (BTEC, and the fuel oxygenate methyl tertiary butyl ether (MTBE) by Environmental Protection Agency (EPA) Method 8260B The monitoring well MW-1 sample was also analyzed for total petroleum hydrocarbons as motor oil (TPHmo) by EPA Method 8015M Laboratory results are summarized in Table 1 Copies of the laboratory data sheets and chain-of-custody reports are included as Attachment C On 19 May 2000, Horizon transported the purge water to InStrat, Inc in Rio Vista, California for disposal A Non-Hazardous Material Profile Sheet was filled out and accompanied the shipment A payment receipt for acceptance of the purge water was received by Horizon Copies of the profile sheet and receipt are contained in Attachment D Results Groundwater level data collected by Horizon was used to construct a groundwater contour snap (Figure 2) Depth-to-groundwater measurements were subtracted from the surveyed TOC elevations to calculate static groundwater elevations The average groundwater elevation for the site was approximately 20 4 feet mean sea level and represents an . approximately 3 5-foot fall compared to that measured in December 2000 after installation of the wells The groundwater flow direction was generally to the northwest under a gradient of approximately 0 004 The calculated groundwater flow direction in December 2000 was also to the northwest under a gradient of 0 007 No gasoline or motor oil constituents were reported in the groundwater sample collected from monitoring well MW-1 Concentrations of 300 and 710 micrograms per liter (parts per billion or ppb) TPHg were reported for groundwater samples collected from monitoring wells MW-2 and MW-3, respectively A xylenes concentration of 0 96 ppb was also reported for the groundwater sample collected from monitoring well MW-3 No MTBE was reported in any groundwater sample Recommendations Although the site monitoring wells have only been sampled twice, gasoline constituent concentrations in groundwater appear to be relatively stable Horizon recommends continued quarterly monitoring at the site for three more quarters to identify any trends the hydrogeologic parameters or in groundwater quahty 7039q=U0Q2 doc 703941 2 HORIZON ENVIRONMENTAL INC