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Mr Kyle Christie Project 0805-146 03 January 24, 1996 Page 3 Results of this assessment were reported in EMCON's "Second Quarter 1995 Status Report" (August 2, 1995) Results of analyses indicated that TPHG concentrations .,.ere below laboratory detection limits in all soil samples analyzed, except for the soil sample collected at 25 feet bgs (in the historical capillary fringe zone in boring B-13, which had a concentration of 6 ppm) Benzene, toluene, ethylbenzene, and total xylenes (BTEX) v.ere detected at low concentrations in soil samples collected from the borings Benzene concentrations ranged from 0 005 ppm to 0 087 ppm GROUNDWATER MONITORING. FOURTH QUARTER 1995 EMCON was contracted by ARCO to monitor the groundwater monitoring wells previously installed at the site Field work included measuring depths to groundwater and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the gradient and direction of groundwater flow beneath the site �On Nov 1995 a technician from EMCON measured depths to groundwater and collected groundwater samples from wells MW-1 through MW-7 for subjective and laboratory analyses Floating product was not noted in samples from the wells (see Table 1) Sampling and analysis procedures are presented in Appendix A The wellhead elevations of the site monitoring wells were previously surveyed by Tom O 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 grQundwater flow on N theast and southeast with a hydraulic gradient of 0 003, as shown on Figure 3 The gradient has generally been toward the northeast Groundwater elevations have decreased approximately 0 15 foot since the last sampling event (August 1995) Groundwater samples from wells MW-1 through MW-7 were analyzed for TPHG using Environmental Protection Agency (EPA) Methods 5030/DHS LUFT, and BTEX using EPA Methods 5030/8020 prescribed by the state of California. Groundwater samples are analyzed for HVOCs using EPA Method 601 during the first and third quarters of each year In addition, the samples from wells MW-2 and MW-6 were analyzed for TOG using Standard Methods (SM) 5520 C&F. These samples were analyzed at Columbia Analytical Services, Inc , in San Jose, California. The results of analyses are summarized in Tables 1 and 2. Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix B Results of analyses indicated that dissolved gasoline hydrocarbons were detected in the • groundwater samples collected from the all the wells Concentrations of TPHG ranged from 30,000 parts per billion (ppb) in well MW-2 to 160,000 ppb in well MW-6, and SAC\N TIM90"8051460 3DS-95\pu i