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i 11-4 4. Comment: Tank#4 On February 10, 1989, a liquid sample of the contents of this 1,200 gallon tank was collected and analyzed. The contents were subsequently reported as 46% diesel by weight and the remainder primarily water, but a copy of the analytical results was not provided. Please submit a copy of the analytical results of the tank's contents. On February 23, 1989, the tank was removed and two soil samples (931034 and #31035) were collected at 8.5 feet bgs. Odor and discoloration of the soil were noted by PHS/EHD staff in both areas sampled. The laboratory analysis detected soil contamination in sample #3 103 5 of 110 ppm hydrocarbons in the range of C13 to C28. The Iab quantitated the sample results based upon a diesel standard. The detection limits for TPH were elevated, 25 ppm instead of 1 ppm; also, the detection limits for BTEX were highly elevated, 50 ppm for BTE and 100 ppm for X. The tank was located approximately 125 feet east of Sutter Street and 5 feet south of Market Street. On March 10, 1989, the area where sample #31035 was collected was excavated to approximately 14 feet bgs and 20 cubic yards of contaminated soil removed. Two soil samples (#22926 [bottom sample at 14 feet bgs] and #22927 [north sidewall at 13.5 feet bgs]) were collected from the excavation. PHS/EHD staff observed definite hydrocarbon odors and soil discoloration which was not sampled. Those present at the time of sampling were informed that the contamination would be documented and that resampling could be necessary. The laboratory results from the samples collected did not report contamination; however, the lab noted on sample #22927 that late eluting, unresolved hydrocarbons in the range of C15 to C28 were detected but which could not be quantitated with the method used. The analytical results and field observations do not support closure of the site without additional investigation. Response: The analytical results from the tank liquid sampling are not in Kleinfelder's archived files. It is our understanding that the results of the tank liquid sampling were submitted to the City of Stockton and SJCLHD at the time of the investigation. Petroleum hydrocarbons were detected in one of the two samples collected beneath tank #4. Meinfelder has reviewed the detection limits for the first and second phases of sampling at the tank. The detection limits for the first phase of sampling appear to be elevated, but the detection limits for the second phase of sampling do not appear to be elevated. The detection limit numbers for the first and second phases are the same, but the units (pgNmg versus mg/kg) are different. There is no reason for the detection limits to be elevated, and it appears that the analytical laboratory (California Analytical/Enseco) put the wrong detection limit units on the first phase report. In any event, the soil in question was excavated further. Additional soil was removed from the excavation based on the detected petroleum hydrocarbon concentration. A gray Iayer was observed by Kleinfelder and SJCLHD at a depth of I1 to 13 feet below the ground GL344(1994) Page 4 of 5 June 1, 1994 Copyright 1994 Kleinfelder, Inc. KLE!\EE:-DER 2240 North1)oint Parkvvav, Sa[ t.] Ro"'I, 88