SITE INFORMATION AND CORRESPONDENCE

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Wendy L. Cohen • • 4 15 March 1993 Ground Water Monitoring Results A more extensive ground water sampling program was conducted after installation of additional monitoring wells. The program also included more wells not previously sampled during the preliminary ground water sampling program. 1 . The report states that ST's eastern property boundary contained 0.36 foot of free product (FP) on 21 September 19 PS/MW-16. 92 and 0.01 foot of FP also was detected in TS/MW-1 and This characterization of the extent of FP is wholly inaccurate. Following is a complete description of the FP extent obtained from Table 7 which was based on the September 1992 sampling. Well Number Product Thickness (feet) AR/MW-IA Sheen AR-MW-9A Sheen AR-MW-11A Sheen PS/P-11 0.08 PS/MW-14 0.36 PS/MW-16 0.02 ST/MW-1 0.89 TO/T-1 TSheen Sheen TO/T-5 Sheen TO/T-8 Sheen TO/T-12 Sheen TO/R-1 through R-6 Sheen The report did not state how often the wells are checked for FP or if there is an ongoing bailing program. The above table shows that it was PS/MW-14 which had 0.36 foot of FP and ST/MW-1 had 0.89 foot. The table also shows TS-1 had sheen on the ground water yet the depth to water column of Table 7 says "Ory". This discrepancy must be explained. 2. The report states that except for one, all B-zone monitoring wells showed contamination, and additional data will be needed to determine its horizontal extent. Yet, as stated above, no additional work is proposed. Thus, the lateral extent of contamination in the B-zone is not defined and the vertical extent of contamination at the entire terminal is not defined. 3. The report states that ground water samples indicated two separate areas over the site where TPHG values exceeded 100,000 119/1 , and low concentrations of BTEX were detected in ground water samples from an upgradient piezometer PS/CB- 1 . The significance of 100,000 pg/l was not stated. Plate 3 of Harding Lawson Associate's 1990 report shows the location of Stockton Petroleum (SP) northeast of Time Oil and adjacent to PS/CB-1 's location. Although PS/CB-1 appears to be upgradient of SP, the latter's activities, which were not included in the site history, could have affected the ground water beneath SP and also the ground water being monitored by PS/CB-1 . PS/CB-1 was not resampled to confirm earlier results.