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• Corporadon ember of The IT Group Ms. Devra Lewis Project 812717 April 9, 2001 Page 4 This error was not detected in our review. • Figure 9 has a value of 1,700 ppb contoured inside the 5,000 ppb contour line; This is also an error that was not detected in our review. • Figure 14 has an 11,000 ppb concentration not contoured; The 11,000 gg/L concentration was not included within a contour because we had no data from surrounding wells. Additional groundwater analytical data in this area will be generated as part of the expanded groundwater monitoring program and will be included in the quarterly isoconcentration maps. • Figure 18 has a value of 369 contoured closer to the 100 contour line than a 286 value; The location of the contour line in the area of the 369 gg/L value was based on our interpretation of the concentration gradient in this area. Historical groundwater analytical data indicates that petroleum hydrocarbons have not been detected in upgradient groundwater samples (north and northwest). Based on these data we have inferred that the concentration gradients in this area are steep. • Figure 18 has a value of<1,000 within the <50 contour line; and The analytical laboratory diluted the D-Zone groundwater sample from CPT CPT/H00-05 which raised the lower reporting limit for this sample from the standard 50 µg/L to 1,000 µg/L. TPHD was only detected in groundwater samples from two of the CPTs at concentrations of 268 gg/L at CPT/H00-03 and 369 gg/L at CPT/H00-08. Both of these detection's were at CPTs located downgradient of the STTC facilities. Based on this data we inferred that the TPHD would not likely be detected in groundwater samples within the D-Zone at this location. TPHD concentrations in the D-Zone in this area will be further evaluated as part of the expanded groundwater monitoring well program. • Figure 22 has a value of<2,000 outside the <50 contour line. The analytical laboratory diluted the D-Zone groundwater sample from CPT CPT/H00-05 which raised the lower reporting limit for this sample from the standard 50 gg/L to 2,000 gg/L. TPHD was only detected in groundwater samples from two of the CPTs at concentration of 126 gg/L at CPT/H00-09 and 392 gg/L at CPT/H00-03. Both of these detection's were at CPTs located downgradient of the STTC facilities. Based on this data we inferred that the TPHD would not likely be detected in this area. TPHD concentrations in the D-Zone in this area will be further evaluated as part of the expanded groundwater monitoring well program IT and the STTC (Jeff Baker of Tesoro Petroleum) would appreciate the opportunity to meet with you on-site at the Stockton Terminals to discuss project progress and provide a tour of this IT CORPORATION SAC:\C:\My DocumenwProjects\Pon ofStocktom.CPT HP Study\Response to Comments.doc-98\it 1 812717