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KEI-P89-1104 .QR6 • February 1, 1993 Page 3 DISCUSSION AND RECOMMENDATIONS Based on the analytical results for the ground water samples collected and evaluated to date, and no evidence of free product or sheen in any of the wells, KEI recommends the continuation of the current quarterly monitoring and semi.-annual sampling program of the existing wells, per KEI ' s proposal (KEI-P89-1104 . P5) dated December 10, 1990, and as modified in KEI ' s quarterly report (KEI- P89-1104 .QR4) dated February 3 , 1992 . As previously reported in KEI ' s report (KEI-P89-1104 .QR5) dated July 24 , 1992 , the analytical results for the ground water sample collected from well MW1 on June 22 , 1992 , indicated a concentration of 180 ppb of high boiling point (HBP) hydrocarbons . However, Sequoia Analytical Laboratory had noted that the sample "does not appear to contain diesel. HBP is due to several unidentified, non- fuel peaks. " Therefore, KEI recommended that the next groundwater sample collected from MW1 also be analyzed by EPA method 8270 (for semi-volatile organic compounds) , in an attempt to determine the unidentified peaks. The analytical results for the ground water sample collected from well MW1 on December 30, 1992 , indicated non-detectable concentra- tions of all EPA method 8270 constituents, except for 4 . 2 ppb of 1, 2-dichlorobenzene. However, the following compound was "tenta- tively identified" by the EPA method 8270 "open scan" : methyl-1, 2-ethanediyl) bis (oxy) ] -bis-2-Propano1 at a concentration of 660 ppb. Based on information provided by Sequoia Analytical Laboratory, this compound is a naturally occurring carbohydrate. Therefore, no additional analyses are recommended for well MW1, other than the current TPH as gasoline, TPH as diesel, BTX&E, and EPA method 8010 analyses. DISTRIBUTION A copy of this report should be sent to Mr. Harlin Knoll of the San Joaquin County Public Health Services Department, and to the Regional Water Quality Control Board, Central Valley Region. LIMITATIONS Environmental changes, either naturally-occurring or artificially- induced, may cause changes in ground water levels and flow paths, thereby changing the extent and concentration of any contaminants. Our studies assume that the field and laboratory data are reasonab- ly representative of the site as a whole, and assume that subsur- face conditions are reasonably conducive to interpolation and extrapolation.