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1 ' 7-Eleven/Stockton 13 • March 1991 The distribution of detectable dissolved-hydrocarbons in the monitoring wells sampled during this quarter was confined to samples from monitoring wells MW-1 and MW-17b Analytical results showed that the highest concentration of dissolved hydrocarbons was detected in the sample collected 1 from monitoring well MW-1 during the October 23, 1990, sampling round Results showed a concentration of 51 parts per billion (ppb) TPH-as-gasoline and no detectable BTEX compounds in the ' sample from monitoring well MW-1 The concentration of TPH-as-gasoline reported in the sample from monitoring well MW-17b was 1 ppb and BTEX compounds were non-detectable Samples from all of the ' other monitoring wells and pumping wells contained no detectable levels of dissolved hydrocarbons Historical results of past laboratory data for the monitoring and pumping wells are tabulated in Appendix E 1 The results of laboratory analyses on groundwater samples collected from the domestic wells ' surrounding the site indicate that none of the wells contained detectable levels of dissolved hydrocarbons during the October 23 and November 27, 1990 sampling rounds However, results of laboratory analyses from the December 23, 1990 sampling round showed 3 ppb of TPH-as-gasoline and no detectable BTEC compounds in the TMG well Sampling from a number of the nearby domestic wells I (including the TMG well) has been conducted on either a weekly or a monthly basis since July 1986 The laboratory data collected to this date has shown that the BTEC and TPH-as-gasoline concentrations are commonly not detectable with some sporadic positive results The few positive results have ' primarily been below 50 ppb of TPH-as-gasoline The last positive analytical laboratory results for the presence of TPH-as-gasoline prior to December 28, 1990 were reported on August 10, 1989, with a ' concentration of 1 ppb reported for the TMG water sample and concentrations of 2 ppb reported for samples from wells 1927 and 9140 The highest concentrations reported in any of the domestic wells were from the July 3 and July 17, 1986 sampling rounds During these initial sampling rounds the highest concentration was reported in the well 9149 with concentrations of 19,000 ppb of TPH-as-gasoline Samples from well TMG were reported on July 17, 1986 as having concentrations of 890 ppb of TPH-as-gasoline Subsequent domestic well sampling on July 18, 1986 by the Department of Health Services (DHS) from eleven of the wells that had previously reported detectable concentrations of TPH-as-gasoline reported non-detectable levels in each of the eleven samples The DHS sampling included the domestic well 9149, which had previously shown 19,000 ppb of TPH-as-gasoline Likewise, later sampling rounds from these wells by Groundwater Technology have shown concentrations to be not detectable Lr GROL ND%kATER TEcHNOLOGt INC