COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Lee Higgins - 7 - 7 December 2010 Chevron, TAOC Tracy Rail Yard concentrations detected in the sample from TRY-29 at a depth of five feet bgs, are inconsistent with the low TPHc detection of 240 mg/kg TPHc. AMEC concluded the elevated PAHs detected are unrelated to the historical crude oil pipelines, likely originating from another source. The PAH findings will be addressed by UPRR's consultant and incorporated into a health risk assessment report to be submitted to the DTSC for review. According to the Report, and similar to soil conditions at OU-2, TPH affected soil present at depths greater than 11 feet bgs extending to approximately 20 feet bgs, was encountered along the central-western edge of OU-5. The area of affected soil is adjacent to and about 100 to 200 feet to the north of, the historical TAOC pipelines. The lateral extent of affected soil has been defined at about 200 feet north-northeast of the former TAOC pipeline alignment. The vertical extent of affected soil was defined by analytical results of ND for TPHc for samples collected at a depth of approximately 21 feet bgs, and where visually affected soil was not observed in drill cuttings. However, the lateral offsite extent of TPH affected soil/groundwater offsite to the west and south of OU-5 into adjacent residential areas has not been adequately delineated, and will be addressed by future offsite soil and groundwater investigations. Groundwater TPHd was detected in six of the 13 samples submitted for analysis, with concentrations ranging from 68 to 510 fag/L. BTEX were not detected. PAHs were detected in 10 samples, and four carcinogenic PAHs detected had TEQs ranging from 0.0043 to 0.022 pg/L. Analytical results of the four downgradient boring samples for TPHd were ND at the MDL of 100 pg/L. Evaluation of the TRY-29 groundwater sample chromatogram determined that the TPHd present (5,600 pg/L) is consistent with severely biodegraded San Joaquin Valley crude oil and possibly bunker fuel. Soil Vapor Sampling One offset location (SV-E) near prior borings with elevated TPH in soil and groundwater in close proximity to adjacent residential areas, was chosen for collecting soil vapor samples at depths of five and ten feet bgs. Vapor samples were submitted for analysis of BTEX and naphthalene. Similar to results in OU-2, 3, and 4, benzene and naphthalene were ND in all samples at respective laboratory reporting limits. However, low concentrations of toluene, ethylbenzene, and xylenes were detected. The analytes detected did not exceed their respective residential or commercial environmental screening levels. According to AMEC's Report: • Analytical results of soil vapor samples collected from five impacted areas bordering adjacent residential areas, did not detect benzene or naphthalene above environmental screening levels. Low concentrations of toluene, ethylbenzene, and xylenes did not exceed respective method detection limits. AMEC summarized that the data indicates the soil vapor at those locations is not significantly impacted.