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r Wrn. J. Hunter & Associates 2220 Loma vista Dr. Registered Geologists €:; `III,4, .;' { ;1 ;`hj ';{ Sacramento, CA 95825 Petroleum & Mineral Appraisers - '?'i`�" {916) 972-7941 I `j , 7�L FAX (916) 972-1683' November 5, 1996 Linda Turkatte, Sr. REHS - o- San Joaquin County PHS Environmental Health Division P. O. .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. gradientis 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 27water 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 .281 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 result's of water..analyses since monitoring began. Because MW-1' had riot 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 measure& 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 j 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 i. xylene could have .been caused by contamination in the laboratory, 1 .