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Technical Memorandum Hartman King PC 13 March 2020 1883010.00 Page 2 Kennedy Jenks Attorney Client Privilege/ Attorney Work Product The 24 January 2019 soil samples were analyzed by California Laboratory Services for metals by EPA Method 6020 and EPA Method 7471 B, semi -volatile compounds by EPA Method 8270C, and total petroleum hydrocarbons (TPH) as diesel and motor oil by EPA Method 8015M. The laboratory analytical report is included in Attachment B. Semi -volatile compounds and TPH as diesel were not detected in any of the four samples at or above the laboratory reporting limits. Metals results are summarized in Table 1. Barium, chromium, cobalt, copper, nickel, vanadium, and zinc were detected in every sample, and lead and molybdenum were detected in the sample from SS -01. As shown in Table 1, detected concentrations of metals were below the Department of Toxic Substances Control (DTSC) screening levels and US EPA Regional Screening Levels (RSLs) by one to four orders of magnitude and likely represent background concentrations. TPH concentrations and RSLs for residential and industrial soil are shown in Table 2. The laboratory methods refer to TPH with a carbon number range of 10-28 (C10 -C28) as Diesel Range Organics and to heavier hydrocarbons with 17-44 carbons (C17 -C44) as Motor Oil Range Organics. Only TPH in the motor oil range was detected (C17 -C44). Based on our understanding of the material in the drums, and because TPH in the diesel range (C10 -C28) was not detected, it is reasonable to assume that the carbon range of the TPH detected are on the heavier side of the TPH motor oil range. This distinction is important because although the US EPA RSLs shown on Table 2 are also distinguished by carbon number, the carbon ranges don't correspond directly with the carbon ranges reported by the laboratory using EPA Method 8015M. Instead, the RSLs designate a ,'medium" weight corresponding to C9 -C16 or C9 -C18 (the lower end of the diesel range) and "high" weight corresponding to C17 -C32 or C19 -C32. The classification is further distinguished as "aliphatic" or "aromatic" based on molecular structure. Aliphatic compounds have been found to comprise about 73 — 80% of the total weight of used oil'. Therefore, it is reasonable to assume that the TPH concentrations reported in Table 2 would fall predominantly into the "High Aliphatic" classification of the USEPA RSLs. Drum Removal and October 2019 Soil Sampling Further soil samples were collected on 7 October 2019, to characterize the extent of hydrocarbon -impacted soils in advance of excavation and removal. Soil samples were collected at new locations KJ -01 through KJ -04, and deeper samples were collected at the previously sampled SS -02 and SS -03 locations. Each boring was advanced with a hand auger and the ' Environmental Impact of Used Motor Oil, Science of the Total Environment, Vazquez-Duhalt, Rafael; 1989. plirv1201811883010.00 hartman king - raymus matL-05655 mitchelI residenceltech memo12019 121components1200313_technical memorandum -15655 mitchell rd.docx © Kennedy Jenks Consultants, Inc.