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r Mr Kyle Christie Project 0805-1460 003 April 27, 1995 Page 2 In January 1993, RESNA observed drilling of seven soil bonngs (B-13 through B-19) and the installation of two groundwater monitoring wells (MW-4 and MW-5) and four vapor extraction wells (VW-4 through VW-7) Results of this assessment were reported in RESNA's first quarter 1993 status report (RESNA, June 9, 1993, Report 31009-7) Analytical data indicated that hydrocarbons present in soil below 26 feet and in groundwater were probably from an off-site source Therefore, ARCO requested that an investigation of soil and groundwater be performed off site and upgradient of the ARCO station to evaluate whether hydrocarbons were present upgradient of the site In October 1993, RESNA observed drilling of two soil borings (1320 and B21) and the installation of two groundwater monitoring wells (MW-6 and MW-7) Analytical data indicated that residual and dissolved hydrocarbons are present in wells MW-6 and MW-7 (RESNA, February 15, 1994, Report 31009-9) HVOCs were also detected in groundwater samples collected from monitoring wells MW-6 and MW-7 GROUNDWATER MONITORING: FIRST QUARTER 1995 EMCON was contracted by ARCO to conduct the field work at the site Feld work included measuring depths to water and collecting groundwater samples for subjective and laboratory analyses EMCON used these data to evaluate the direction and gradient of groundwater flow beneath the site )OnFebruary 16, 1995, a technician from EMCON measured depths to water 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) Due to an automobile parked over well MW-7, the well was inaccessible during the site visit Field procedures are presented in Attachment 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 1, were used to evaluate the potentiometnc surface beneath the site The direction of groundwater flow on February 16, 1995, was southeast with a hydraulic gradient of shown on Figure 3 The adient is not consistent with previous data The c gem groundwater gradient and direction may be due to the increase in water levels Groundwater elevations have increased approximately 2 93 feet since the last sampling event(December 1994) Groundwater samples from wells MW-1 through MW-6 were analyzed for total petroleum hydrocarbons as gasoline (TPHG) using Environmental Protection Agency (EPA) Methods 5030/DHS LUFT, and benzene, toluene, ethylbenzene, and total xylenes using EPA Methods 5030/8020 prescribed by the state of California Samples were also analyzed for HVOCs using iEPA Methods 5030A/601, and the samples from wells MW-2 and MW-6 were analyzed for TOG using Standard Methods (SM) 5520 C&F and SM 5520 C These samples were analyzed at Columbia Analytical Services, Inc , in San Jose, Califomia The results of analyses are SAC1N 1PJM805108051460 3AL-94kims i