ARCHIVED REPORTS XR0001801 - Laserfiche WebLink

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I - e�u� Working to Restore Nature 1 On March 21, 1994, a technician from GTI measured depths to water and collected groundwater samples from the wells for subjective and laboratory analyses The technician noted no floating product or sheen in the three wells (Table 2) The wellhead elevations of the monitoring wells at the site were surveyed by Tom O F Morrow Inc The surveyed elevations and the depth-to-groundwater measurements, summarized in Table 2, were used to evaluate the potentiometric surface beneath the site The direction of groundwater flow on March 21, 1994 was southeast with a hydraulic gradient of 0 001 as shown on Plate 15 The static water level in the wells was approximately 60 feet below grade 1 Groundwater samples were analyzed for TPHg and BTEX using EPA Methods 5030, 8020 and Modified 8105, TPHd using EPA Method 8015, and TOG using EPA Method 413 2 These samples were analyzed at GTEL Environmental Laboratories, Inc in Concord, California. The results of analyses are summarized in Table 2 Copies of the laboratory 1 analysis reports are in the appendix Results of analyses indicated dissolved gasoline hydrocarbons were detected in samples from the three wells Concentrations of TPHg ranged from 60 parts per billion (ppb) to 130 ppb in the three wells Benzene was detected at 0 4 ppb in well MW-3 but was not detected in wells MW-1 and MW-2 Concentrations of TPHd and TOG were below detection limits in samples from all three wells. These results are shown on Table 2. Concentrations of TPHg and benzene are shown on Plate 2 WORK IN PROGRESS 1 ARCO will continue to perform quarterly groundwater sampling ARCO is in the process of evaluating the data collected to date and will begin preparation of the Problem Assessment Report (PAR) in the future CONCLUSIONS 1 Residual gasoline, diesel, and oil and grease are present in soil at 21-1/2 to 61-1/2 feet bsg near the former gasoline and waste-oil tanks Soil near the northeast property boundary contains O&G (72 ppm) at 21-1/2 feet bsg Residual gasoline, diesel, and oil and grease are not present in soil at the southwest property boundary Dissolved gasoline hydrocarbons 1 were detected in samples from the three wells, however, dissolved diesel and oil and grease were not detected 031%car/38N8-11 4 !