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i 'i "�Fu� Working to Restore Nature GROUNDWATER MONITORING: FOURTH QUARTER 1993 EMCON Associates (EMCON) of Sacramento, California, was contracted by ARCO to E' monitor the groundwater in the monitoring wells previously installed at the site, EMCON )X-) subsequently forwarded their field notes and the laboratory reports to RESNA RESNA used these data to evaluate dissolved gasoline hydrocarbon concentrations and the flow direction and groundwater gradient , On October 27, 1993, a technician from EMCON took water-level measurements and collected groundwater samples from monitoring wells MW-1 through MW-4 for subjective and laboratory analyses_ The technician did not observe floating product or product sheen on samples collected from the wells (Table 1) The surveyed elevations of the top of casing and the depth-to-groundwater measurements (summarized in Table 1) were used to evaluate the potentiometric surface beneath the site On October 27, 1993, the direction of groundwater now was northwest with a gradient of ' approximately 0 02 (Plate 3) The direction of groundwater flow has generally been i northwest since our investigation began The elevation of the groundwater surface has increased an average of approximately 0 42 foot in wells MW-1 through MW-4 since the last quarterly monitoring event (August 18, 1993) Groundwater samples from each well were analyzed for total petroleum hydrocarbons as gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) using Environmental Protection Agency Method 5030/8020/DHS LUFT The samples were analyzed at Columbia Analytical Services, Inc in San Jose, California (Hazardous Waste {C Testing Laboratory Certificate 1425) Samples were also analyzed for total lead using EPA " Method 7421 at Golden State/CAS Laboratories, Inc in Canago Park, California The results of analyses are summarized in Table 1 Copies of the laboratory analysis reports are attached Results of analyses indicated TPHg and BTEX concentrations were below laboratory detection limits in groundwater samples collected from wells MW-1 through MW- 4 with the exception of 0 7 parts per billion total xylenes Total lead was not detected in wells MW-1, MW-2, and MW-4 but was detected at 3 0 parts per billion in well MW-3 , WORK IN PROGRESS We understand the first quarter groundwater sampling event is schedule to be conducted in January 1994 �(C i i23ccar/3M-7 2