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Wm. J. Hunter & Associates 2220 Loma Vista Dr Registered Geologists _,�' ;; Sacramento, CA 95825 Petroleum& Mineral Appraisers (916) 972-7941 FAX (916) 972-1683 T November 5 , 1996 Linda Turkatte, Sr REHS San Joaquin County PHS Environmental Health Division P 0 Box 388 Stockton, CA 95201-0388 Ref RESULTS OF GROUNDWATER SAMPLING - MARCI ' S DIESEL SERVICE, 2969 LOOMIS ROAD, STOCKTON On October 10, 1996, Del-Tech Geotechnical Support Services determined depth to water, and purged & sampled monitoring well #1 at the above site Water levels were also measured in MW-2 & MW-3 , but per instructions from the EHD, those wells were not sampled The field work was witnessed by a representative of the San Joaquin EHD A copy of the field log, chain of custody forms, and laboratory analyses of the water samples taken from MW-1 are included The direction of groundwater flow is to the southwest as shown on .� EXHIBIT A The gradient is very low, at about 0006 ' /ft EXHIBIT B shows the directions of flow since monitoring began Depth to groundwater during this event averaged 69 23 ' below grade, the highest level since monitoring began in April, 1992 There have been a total of 27 water level measurements taken since the start of the project The maximum variation in elevation was 4 801 , and the average depth to water is 71 28 ' bgl This small fluctuation in water levels, coupled with the highly divergent gradient , strongly suggests a very limited aquifer of extremely low transmissivity TABLE 1 summarizes all of the results of water analyses since monitoring began. Because MW-1 had not been entered since November, 1994, a water sample was taken prior to purging the well The well was then purged and sampled as detailed in the attached field notes submitted by Del-Tech The water sample taken prior to purging measured 1 2 ug/L of xylene; benzene, toluene, ethylbenzene, MBTE, & TPHd were below detection levels After purging the well, the water sample measured 1 3 ug/L; all others were non-detect The bailer blank prior to the second 3 sampling also revealed xylene at 1 . 1 ug/L The reason for this has not been identified A new, disposable bailer was used to collect the sample prior to purging, and also for the bailer blank The second water sample was collected with a stainless steel bailer which had been thoroughly cleaned and rinsed prior to use Although it is possible that the very minor amount of xylene could have been caused by contamination in the laboratory, 1