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April 23, 1998 96-1113008.80 State of California Department of the Youth Authority Facilities Planning Division Attention: Ms. Corinda Yep, Chief-Hazardous Materials and Waste Program Subject: LETTER-REPORT-Re-Sampling of Former Diesel Underground Storage Tank Locations Northern California Youth Correctional Center 7650 South Newcastle Road Stockton, California Page 2 had been established in the field. The MARK representative consulted with Ms. Briggs regarding her understanding of the sample identifications,and she agreed that there had apparently been some confusion as to sample identification. A summary of possible the mis-identifications in the preliminary data is as follows: ■ Samples from the Dewitt Nelson School appeared to have been reversed, west to east. However,since the total petroleum hydrocarbons as diesel(TPH-d)analytical results were either none detected or very low[64 milligrams per kilogram(mg/kg)in stockpile sample SP-DW-D], no re-sampling was considered warranted; ■ Samples from the Karl Holton School also appeared to have been reversed, west to east. In this case, the TPH-d analytical results for the native soil were none detected, however, the excavation stockpile results were reported at 8,528 mg/kg(SP-CH-H)and 586 mg/kg(SP-CH- F). Given the wide difference in TPH-d levels between the two locations, and that different remedial options would probably be recommended,resampling was considered warranted; and ■ Samples from the O.H Close School appeared accurate with respect to location. However,the high TPH-d concentration(7,994 mg/kg)reported for native soil sample YA-5 was contrary to observations made in the field. The laboratory,Chemical and Environmental Laboratories,Inc., was contacted and was asked to evaluate whether the sample sleeve contained excavation backfill(yellow-ish to grayish-brown sand or grayish-brown silty clay) or native soil(reddish- brown clayey silt). The laboratory reported that the supposed native soil sample YA-5 consisted of grayish-brown sand which matches the description of excavation backfill. Given that it appears that excavation backfill was sampled and analyzed rather than native soil, re-sampling was considered warranted for the west UST location. On March 30, 1998, Allwest submitted their Underground Fuel Storage Tank Closure report to Vector 3, and then subsequently to DYA. In this report, the mapped sample locations appeared to have been adjusted to correspond to the sample identifications agreed to upon in the field. However, reported sample concentrations still appeared to be anomalous. Their report stated the findings and recommended further delineation of the extent of TPH-d impacted soil beneath the former location of tank no. 5 (i.e., west UST at O. H. Close School). Due to the apparent location and concentration anomalies, MARK recommended re-sampling of the Karl Holton School UST locations and the west UST location at the O. H. Close School.